Patent Publication Number: US-11658352-B2

Title: System and method for operating a rechargeable electrochemical cell or battery

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/670,933 (now U.S. Pat. No. 11,056,728), filed Oct. 31, 2019, and entitled “System and Method for Operating a Rechargeable Electrochemical Cell or Battery,” which is incorporated herein by reference in its entirety for all purposes. 
    
    
     TECHNICAL FIELD 
     Charge/discharge management of electrochemical cells, and related systems, are generally described. 
     BACKGROUND 
     Conventionally, batteries have failed to compete successfully with established power sources such as combustion engines in various industries, such as vehicles. One reason for this failure has been that battery users have been dissatisfied with the longevity and performance that batteries have conventionally provided. 
     SUMMARY 
     Disclosed herein are embodiments related to charge/discharge management of electrochemical cells and related systems. The subject matter of the present invention involves, in some cases, interrelated products, alternative solutions to a particular problem, and/or a plurality of different uses of one or more systems and/or articles. 
     Some embodiments are directed to an electrochemical cell management system comprising: an electrochemical cell, and at least one controller configured to control the cell such that, for at least a portion of a charge cycle, the cell is charged at a charging rate or current that is lower than a discharging rate or current of at least a portion of a previous discharge cycle. 
     Some embodiments are directed to an electrochemical cell management system comprising: an electrochemical cell, and at least one controller configured to monitor at least one characteristic of the cell, the at least one characteristic comprising at least one of: at least a portion of a discharge history of the cell, and at least one morphological characteristic of the cell, and based on the at least one characteristic of the cell, induce a discharge of the cell and/or control a charging rate or current of the cell. 
     Certain embodiments are directed to an electrochemical cell management system comprising: an electrochemical cell, and at least one controller configured to induce a discharge of the cell before and/or after a charging step of the cell. 
     Further embodiments are directed to an electrochemical cell management method. The method may comprise controlling an electrochemical cell such that, for at least a portion of a charge cycle, the cell is charged at a charging rate or current that is lower than a discharging rate or current of at least a portion of a previous discharge cycle. 
     Additional embodiments are directed to an electrochemical cell management method. The method may comprise inducing a discharge of an electrochemical cell before and/or after a charging step of the cell. 
     Some embodiments are directed to an electrochemical cell management method. The method may comprise monitoring at least one characteristic of the cell, the at least one characteristic comprising at least one of: at least a portion of a discharge history of the cell, and at least one morphological characteristic of the cell; and based on the at least one characteristic of the cell, inducing a discharge of the cell and/or controlling a charging rate or current of the cell. 
     Other advantages and novel features of the present invention will become apparent from the following detailed description of various non-limiting embodiments of the invention when considered in conjunction with the accompanying figures. In cases where the present specification and a document incorporated by reference include conflicting and/or inconsistent disclosure, the present specification shall control. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention. In the figures: 
         FIG.  1 A  is a block diagram illustrating a representative electrochemical cell management system, according to some embodiments. 
         FIGS.  1 B- 1 D  are current-time graphs illustrating representative charging schemes for a representative electrochemical cell management system, according to some embodiments. 
         FIG.  1 E  is a circuit diagram illustrating a representative simplified electrochemical cell model, according to some embodiments. 
         FIG.  1 F  is a block diagram illustrating a representative battery management system, according to some embodiments. 
         FIG.  2    is a block diagram illustrating a representative battery pack, according to some embodiments. 
         FIG.  3 A  is a block diagram illustrating a representative battery management system, according to some embodiments. 
         FIG.  3 B  is a block diagram illustrating a representative cell set and corresponding components, according to some embodiments. 
         FIG.  3 C  is a cross-sectional schematic diagram illustrating the application of an anisotropic force to one or more electrochemical cells, according to some embodiments. 
         FIG.  3 D  is a cross-sectional schematic diagram of electrochemical cells, according to some embodiments. 
         FIG.  4 A  is a flow chart depicting a representative process for controlling a charging rate or current of a cell, according to some embodiments. 
         FIG.  4 B  is a flow chart depicting an additional representative process for controlling a charging rate or current of a cell, according to some embodiments. 
         FIG.  4 C  is a flow chart depicting a representative process for inducing discharge of a cell, according to some embodiments. 
         FIG.  4 D  is a flow chart depicting an additional representative process for inducing discharge of a cell, according to some embodiments. 
         FIG.  5 A  is a flow chart depicting a representative process for monitoring cell characteristic(s) and inducing discharge or controlling the charge rate or current of the cell, according to some embodiments. 
         FIG.  5 B  is a flow chart depicting an additional representative process for monitoring cell characteristic(s) and inducing discharge or controlling the charge rate or current of the cell, according to some embodiments. 
         FIG.  6 A  is a flow chart depicting a representative process for discharging sets of cells of a battery, according to some embodiments. 
         FIG.  6 B  is a flow chart depicting an additional representative process for discharging sets of cells of a battery, according to some embodiments. 
         FIG.  6 C  is a flow chart depicting a representative process for controlling a battery pack, according to some embodiments. 
         FIG.  6 D  is a flow chart depicting an additional representative process controlling a battery pack, according to some embodiments. 
         FIG.  7 A  is a chart depicting an exemplary discharge profile, according to some embodiments. 
         FIG.  7 B  is a chart depicting an exemplary full discharge profile, according to some embodiments. 
         FIG.  7 C  is a chart depicting an exemplary battery cycle life, according to some embodiments. 
         FIG.  8    is a block diagram depicting a representative computing system that may be used to implement certain aspects. 
     
    
    
     DETAILED DESCRIPTION 
     The inventors have recognized and appreciated that conventional techniques for management and operation of rechargeable electrochemical cells have resulted in the previously poor longevity and performance of cells (and batteries in which they may be included). For example, cells have suffered a short cycle life (e.g., a low number of complete charge and discharge cycles before capacity falls below 80% of original capacity, as cells typically do at some point after sufficient usage), particularly where charge and discharge rates are similar, or where the charge rate is higher than the discharge rate. For example, many users of cells in batteries have desired the batteries to have nearly identical charge and discharge rates (e.g., 4 hours to charge and 4 hours to discharge), and battery manufacturers have provided batteries and battery management systems that provide such nearly identical rates. Many users have also desired batteries to charge at higher rates than they discharge (e.g., 30 minutes to charge and 4 hours to discharge) for various reasons, such as to reduce inconvenience of waiting for charging to use the batteries. 
     The term “complete charge cycle” is used herein to generally refer to a period of time during which about 100% of a cell&#39;s re-charge capacity is charged, and the term “complete discharge cycle” is used to generally refer to a period of time during which about 100% of the cell&#39;s discharge capacity (which may be different from it re-charge capacity) is discharged. On the other hand, the term “charging step” is used herein to generally refer to a continuous period of time during which charging is performed without discharging, and the term “discharging step” is used herein to generally refer to a continuous period during which discharging is performed without charging. 
     The term “charge cycle” is used to generally refer to a period of time during which the cell is charged, and it need not be a complete charge cycle. The term “discharge cycle” is used to generally refer to a period of time during which the cell is discharged, and it need not be a complete discharge cycle. The term “previous discharge cycle” is used to generally refer to a period of time during which the cell has been or is being discharged. For example, this “previous” discharge cycle may have been completed or may still be in progress—it need not refer to the most recent completed discharging steps that sum to about 100% of the cell&#39;s discharge capacity. If no complete discharge cycle has been performed, the previous discharge cycle may refer to any previously completed discharging steps. 
     The term “capacity” is used to generally refer to an amount of electrical charge a cell or cells can deliver at a given or rated voltage and is often measured in amp-hours (such as milliamp-hours or mAh). In some embodiments, capacity may be the mAh a cell or cells can hold at a given point in time (which may change over multiple charge or discharge cycles), it may be the mAh remaining in a cell or cells at a given point in time, or it may be the mAh a cell or cells need to fully re-charge. 
     The inventors have recognized and appreciated that the cycle life of a cell (and a battery including the cell), and consequently the longevity and performance of the cell (and battery), may be greatly improved by employing higher ratios of discharge rate to charge rate. Furthermore, the inventors have recognized and appreciated that these ratios may be employed by providing a cell and/or battery management system that controls the cell or cells to provide such ratios. 
     For example, some embodiments are directed to a cell management system that controls a cell such that, for at least a portion of a charge cycle, the cell is charged at a charging rate or current that is lower than a discharging rate or current of at least a portion of a previous discharge cycle. As another example, some embodiments are directed to a cell management system that monitors at least one characteristic of the cell (such as some portion of the cell&#39;s discharge history or a morphological characteristic of the cell) and induces a discharge or controls the charging rate or current of the cell based on the characteristic(s). As an additional example, some embodiments are directed to a cell management system that induces a discharge of the cell immediately (or at some earlier time) before and/or after a charging step of the cell, while the cell is connected to a charging device. 
     In some embodiments, inducing a discharge of a cell may include discharging the cell in response to a command from the controller. In some embodiments, an induced discharge may be at a rate higher than an average discharge rate in the cell&#39;s discharge history. In some embodiments, an induced discharge may include discharging the cell without powering a load to perform a function, which may be done for the purpose of altering the overall average discharge rate of the cell and/or the average for a present charge/discharge cycle. In some embodiments, an induced discharge may be performed during a charge cycle, which may include multiple charging steps such as are shown in  FIGS.  1 B- 1 D . 
     Some embodiments, such as embodiments having multiple cells, are directed to a battery management system that multiplexes cells such that the cells can be charged all at once (or with multiple cells discharged at the same time) and discharged individually or in smaller sets. This may result in actual ratios of discharge rate to charge rate for the cells that improve their cycle life, while providing whatever output rates that are desired or required for particular loads and applications. Furthermore, the inventors have recognized and appreciated that discharging some but not all of the cells at once with homogeneous current distribution may also improve their cycle life. 
     For example, with a battery having 4 cells, 1 cell could be discharged at a time at 0.5 amps for 3 hours each, and then all 4 cells could be charged at 0.5 amps for 12 hours—such a configuration would provide an actual ratio of discharge rate to charge rate of 4:1, while the ratio from the user&#39;s perspective would be 1:1 because the cells are discharged individually for 3 hours each (totaling 12 hours of discharge time). The inventors have recognized and appreciated that such a battery management system may actually improve the cycle life of batteries while still providing users what they desire or need from the batteries. In some embodiments, the functionality providing this duo of benefits may be hidden from users and may be integrated into the cell blocks and/or batteries themselves. 
     The inventors have recognized and appreciated that the cycle life of batteries may be further improved by monitoring the cycles of the cells and various properties (such as the duration of a connection between a load and a cell or cells currently connected to the load, or a more complex function considering multiple parameters) and selecting which cells to discharge when based on this monitoring, especially compared to conventional techniques, which relied on much simpler selection processes like “round robin” or considering a number of prior discharge cycles. 
       FIG.  1 A  depicts a representative cell management system  100 . In some embodiments, representative system  100  may include a controller (e.g.,  114 ) and an electrochemical cell (e.g.,  121 A). In some embodiments, cell  121 A may be present alone. In other embodiments, additional cells (e.g., optional cells  121 B and  121 C in  FIG.  1 A ) and/or additional cell sets (e.g., optional cell set  122  in  FIG.  1 A ) may be present (e.g., to form battery  120 ). Optionally, system  100  may include one or more sensors (e.g.,  116 ). It should be appreciated that although only a single controller  114  and a single sensor  116  are shown in  FIG.  1 A , any suitable number of these components may be used. Any of numerous different modes of implementation may be employed. 
     According to some embodiments, the cell  121 A may include at least one lithium-metal electrode active material. Additionally, each set of cells (e.g., cell set  121 ) may include one or more cells (e.g.,  121 A- 121 C). In some embodiments, each set of cells may have a single cell. Alternatively, each set of cells may include multiple cells and may form a cell “block,” or multiple sets of cells may together form a cell block. Additionally, each cell (either in a battery, all the batteries in a battery pack, or in a set of cells) or set of cells may utilize the same electrochemistry. That is to say, in some embodiments, each cell may make use of the same anode active material and the same cathode active material. 
     In some embodiments, such as embodiments having multiple cells, a multiplexing switch apparatus (not shown in  FIG.  1 A ) may be included, such as described in relation to  FIG.  1 B  below, and may include an array of switches, such as those further described in relation to  FIGS.  3 A and  3 B  below. Additionally, the multiplexing switch apparatus may be connected to each set of cells and/or to each cell individually. In some embodiments, the controller, such as  114 , may use the multiplexing switch apparatus to selectively discharge the cells or sets of cells. 
     In some embodiments, the controller (e.g.,  114 ) may include one or more processors, which may be of whatever complexity is suitable for the application. Alternatively or additionally, the controller may include an analog circuit and/or a less complex logic device than a processor or microprocessor. 
     In some embodiments, the controller may control the cell such that, for at least a portion of a charge cycle of the cell, the cell is charged at a charging rate or current that is lower than a discharging rate or current of at least a portion of a previous discharge cycle. For example, the controller may cause the cell to be charged for some percentage of the cell&#39;s re-charge capacity (e.g., anywhere from 1% to 100% of re-charge capacity) at a charging rate or current that is on average at least 2 times lower than the discharging rate or current that has been used on average for some percentage of the cell&#39;s discharge capacity (e.g., anywhere from 1% to 100% of discharge capacity) (i.e., the charging rate or current is half as fast as the discharging rate or current). Alternatively or additionally, the controller may cause the cell to be charged at a charging rate or current that is at least 4 times lower than the discharging rate (e.g., as a result of this controlling, over the last discharge/charge cycle, the cell is charged for some percentage of the cell&#39;s re-charge capacity one-fourth as fast as the cell has been discharged for some percentage of the cell&#39;s discharge capacity). The inventors have recognized and appreciated that such ratios of charge rate to discharge rate may improve the performance and cycle life of a cell. 
     In some embodiments, controlling the cell may include controlling when and how to start and stop charging and discharging, induce discharging, increase or decrease the rate or current of charging or discharging, and so on. For example, controlling charging or discharging of the cell may include, respectively, starting charging or discharging, stopping charging or discharging, increasing or decreasing the rate or current of charging or discharging, and so on. 
     In some embodiments, the cell is charged such that, over a period of time during which at least 5% (or at least 1%, or at least 10%, or at least 15%, or at least 25%, or anywhere between) of the capacity of the cell is charged, the average charge rate or current is lower than the average discharge rate or current used to discharge at least 5% (or at least 10%, or at least 15%, or at least 25%, or anywhere between) of the cell&#39;s capacity during a previous discharge cycle, which may be, for example, the immediately preceding discharge cycle or an earlier discharge cycle. 
     In some embodiments, a charging step is performed such that, for at least 5% (or at least 10%, at least 25%, at least 50%, or at least 75%) of the cell&#39;s or battery&#39;s capacity, the average of the charging rate and/or current is less than 50% (or less than 35%, or less than 25%) of an average discharging rate and/or current at which at least 5% (or at least 10%, at least 25%, at least 50%, or at least 75%) of the cell&#39;s or battery&#39;s capacity was discharged during a previous discharge step. 
     In certain embodiments, a charging step is performed such that, for at least 5% (or at least 10%, at least 25%, at least 50%, or at least 75%) of the cell&#39;s or battery&#39;s capacity, the average of the charging rate and/or current is less than 50% (or less than 35%, or less than 25%) of an average discharging rate and/or current at which at least 5% (or at least 10%, at least 25%, at least 50%, or at least 75%) of the cell&#39;s or battery&#39;s capacity was discharged during the immediately preceding discharge step. 
     In some embodiments, an average discharging rate or current during the previous discharge cycle may be equal to or less than an average charging rate or current during the charge cycle, and an average discharging rate or current during discharge of at least 5% of the discharge capacity of the cell during the previous discharge cycle may be at least 2 times higher (or may be 4 times higher) than the average charging rate or current during the charge cycle. The inventors have recognized and appreciated that improvements described herein, such as improved cell cycle life, can still be had even if the average discharge rate for the cell is the same or even slower than the charge rate, so long as during discharge of at least a portion (such as 5%) of the discharge capacity of the cell during the previous discharge cycle, an average discharging rate or current is sufficiently higher than (such as at least double, triple, or quadruple) the average charging rate or current during that time. 
     As used herein, when a cell is charged at multiple different rates over a given period of time (e.g., over a portion of a charging step, over an entire charging step, or over a series of charging steps), the average charging rate over that given period of time is calculated as follows: 
               CR   Avg     =       ∑     i   =   1     n     ⁢           ⁢         CCap   i       CCap   Total       ⁢     CR   i               
where CR Avg  is the average charging rate over the given period of time, n is the number of different rates at which the cell is charged, CRi is the charging rate, CCap i  is the portion of the cell&#39;s re-charge capacity that is charged at charging rate CR i  during the given period of time, and CCap Total  is the total of the cell&#39;s re-charge capacity that is charged over the entire period of time. To illustrate, if, during a charging step, a cell is charged from 0% to 50% of its re-charge capacity at a rate of 20 mAh/minute and then from 50% to 80% of its re-charge capacity at a rate of 10 mAh/minute, then the average charging rate during the charging step would be calculated as:
 
     
       
         
           
             
               CR 
               Avg 
             
             = 
             
               
                 
                   
                     
                       50 
                       ⁢ 
                       % 
                     
                     
                       80 
                       ⁢ 
                       % 
                     
                   
                   ⁢ 
                   
                     ( 
                     
                       20 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       mAh 
                       ⁢ 
                       
                         / 
                       
                       ⁢ 
                       min 
                     
                     ) 
                   
                 
                 + 
                 
                   
                     
                       30 
                       ⁢ 
                       % 
                     
                     
                       80 
                       ⁢ 
                       % 
                     
                   
                   ⁢ 
                   
                     ( 
                     
                       10 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       mAh 
                       ⁢ 
                       
                         / 
                       
                       ⁢ 
                       min 
                     
                     ) 
                   
                 
               
               = 
               
                 16.25 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 mAh 
                 ⁢ 
                 
                   / 
                 
                 ⁢ 
                 
                   min 
                   . 
                 
               
             
           
         
       
     
     As used herein, when a cell is discharged at multiple different rates over a given period of time (e.g., over a given charging step or series of charging steps), the average discharging rate over that given period of time is calculated as follows: 
               DR   Avg     =       ∑     i   =   1     n     ⁢           ⁢         DCap   i       DCap   Total       ⁢     DR   i               
where DR Avg  is the average discharging rate over the given period of time, n is the number of different rates at which the cell is discharged, DRi is the discharging rate, DCap i  is the portion of the cell&#39;s discharge capacity that is discharged at discharging rate DR i  during the given period of time, and DCap Total  is the total of the cell&#39;s discharge capacity that is discharged over the entire period of time. To illustrate, if, during a discharging step, a cell is discharged from 90% to 50% of its discharge capacity at a rate of 25 mAh/minute and then from 50% to 20% of its discharge capacity at a rate of 15 mAh/minute, then the average discharging rate during the discharging step would be calculated as:
 
     
       
         
           
             
               DR 
               Avg 
             
             = 
             
               
                 
                   
                     
                       40 
                       ⁢ 
                       % 
                     
                     
                       70 
                       ⁢ 
                       % 
                     
                   
                   ⁢ 
                   
                     ( 
                     
                       25 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       mAh 
                       ⁢ 
                       
                         / 
                       
                       ⁢ 
                       min 
                     
                     ) 
                   
                 
                 + 
                 
                   
                     
                       30 
                       ⁢ 
                       % 
                     
                     
                       70 
                       ⁢ 
                       % 
                     
                   
                   ⁢ 
                   
                     ( 
                     
                       15 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       mAh 
                       ⁢ 
                       
                         / 
                       
                       ⁢ 
                       min 
                     
                     ) 
                   
                 
               
               = 
               
                 20.71 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 mAh 
                 ⁢ 
                 
                   / 
                 
                 ⁢ 
                 
                   min 
                   . 
                 
               
             
           
         
       
     
     The inventors have recognized and appreciated that a number of factors may go into determining charge rates that may improve the performance and cycle life of a cell such as a lithium metal cell, which may include rate of discharge, cell impedance, and/or cell State of Health (SOH). In some embodiments, the controller may be aware of these factors because it may measure parameters or characteristics (such as via sensor  116 ) that can be used to determine each of them. The controller may directly or indirectly measure charge and discharge current, Coulombs added or removed, cell impedance (capacitive and resistive), and/or cell pressure, size, and/or thickness. 
     In some embodiments, the controller may monitor such characteristic(s) of the cell. For example, the characteristic(s) may include at least a portion of a discharge history of the cell. Alternatively or additionally, the characteristic(s) may include at least one morphological characteristic of the cell. The controller may monitor any of these using sensor  116 , such as a pressure sensor, a gauge to measure thickness, a sensor to measure or determine surface roughness and/or pits (such as pits in an anode), and/or a memory for storing cell charge/discharge history. For example, a pressure sensor may be included to measure uniaxial pressure and/or gas pressure (such as to determine if the cell generates an excessive amount of gas). Alternatively or additionally, a gauge may be included to measure a thickness of the cell, and the controller may determine and monitor at least one rate of increase of the thickness. 
     In some embodiments, the controller may use this information, such as the characteristic(s), to determine the charge method and/or rate to be used, which may include controlling rates or other parameters as described herein. For example, the overall charging scheme may look similar to  FIG.  1 B , where the cell is discharged for time DT and charged for time CT. As shown in  FIG.  1 B , the cell is discharged briefly, then fully charged at a lower current than for discharging, then discharged briefly, and topped back up with charge. 
     As another example, the overall charging scheme may look similar to  FIG.  1 C , which shows a cell being discharged for time DT, charged for time CT at a lower current than for discharging, discharged again for time DT, charged again for time CT, then discharged again for time DT. In some embodiments, CT may correspond to just more than half of the total cell re-charge capacity, and DT may be a relatively short time determined by the SOH of the cell. 
     In some embodiments, the controller may induce a discharge of the cell, such as any of the discharges shown in  FIGS.  1 B- 1 D . For example, the controller may induce a discharge of the cell immediately before a beginning of a charging step of the cell, such as in a form like that shown in  FIGS.  1 B- 1 C . In some embodiments, the controller may cause such an induced discharge or any of those described herein based on the characteristic(s) of the cell. Alternatively, the controller may perform or cause any of these induced discharges based on other criteria, as described herein. In some embodiments, the cell may remain connected to the charging device during both the induced discharge and surrounding charging step(s). 
     The inventors have recognized and appreciated that inducing a discharge at the times described herein may improve the performance and cycle life of the cell because it may bring the ratio of discharge to charge rates or currents to be closer to a desired asymmetric range, such as 2:1 or 4:1. For example, if the cell has been discharged at a lower rate or current than charging, such an induced discharge may be performed at a much higher rate or current to improve the ratio, especially during a portion of the charge/discharge cycle. In some embodiments, the controller may induce a discharge of the cell at a first rate or current, through at least a threshold capacity of the cell (such as at least 5%, at least 10%, or at least 15% of the cell&#39;s discharge or re-charge capacity), before (such as immediately before or less than 10 minutes before) a beginning of a charging step of the cell that charges the cell slower than the first rate or current. In some embodiments, the controller may induce a discharge at a rate or current that is higher than an average discharging rate or current of a previous (such as the latest) discharge cycle and/or discharging step or that is higher than an average charging rate or current of a previous (such as the latest) charge cycle and/or charging step. 
     Alternatively or additionally, the controller may induce a discharge of the cell during (such as at an end of) a discharge cycle and/or discharging step of the cell. In some embodiments, the controller may induce such a discharge at a higher rate or current than that of the existing discharge or an average discharge of a previous discharge cycle. For example, a discharge may be induced at 400 mA, while the average discharge current of the most recent discharge cycle may have been 100 mA. Other examples may be found in Tables 1-4 below. 
     The controller may alternatively or additionally induce a discharge at an end of a charge cycle and/or a discharging step of the cell, such as in a form like that shown in  FIG.  1 C . In some embodiments, inducing a discharge at an end of a cycle may include inducing the discharge within the last 5% (or 10% or 15%) of the cycle. 
     The inventors have recognized and appreciated that inducing a discharge of a cell in some or all of the situations described herein may reduce physical damage to the cell, such as pit formation and extension (e.g., in the anode of the cell), and may even smooth out and undo some previous damage to the cell. 
     The overall charging scheme may, as a further example, look similar to  FIG.  1 D , which shows a cell being first charged for time PCT, then discharged for DT, and finally charged fully for CT. The inventors have recognized and appreciated that when a cell is determined to have been fully discharged, as may be the case for the cell in  FIG.  1 D , it would not be advantageous to start with a discharge cycle and/or a discharging step. 
     In some embodiments, the controller may consider any of several factors when determining the cell State of Charge (SOC) and State of Health (SOH). For example, for cell impedance, the cell model can be simplified as shown in  FIG.  1 E , which shows a resistor in series (RS) with the parallel combination of a resistor (RP) and a capacitor (C 1 ). An impedance measurement may have two components: real and imaginary. The real component may be simply the DC resistance R=RS+RP. The imaginary (or reactive) component in this case may be XC, which may be affected inversely by frequency: 
             XC   =     1     2   ⁢   π   ⁢           ⁢   fc             
where f is frequency and c is capacitance. Impedance (Z) may be found at any particular frequency, and the phase angle may be known or determined as follows: Z=√{square root over (R 2 +XC 2 )}. Impedance may change both with SOC and SOH. The inventors have recognized and appreciated that these relationships may allow the controller to determine how to charge the cell in order to provide improvements described herein.
 
     The inventors have also recognized and appreciated that pulses of charge/discharge cycles and/or charging/discharging steps should not be applied faster than a rate equal to about double or triple RC time constants, because at a faster rate, most of the energy may not be effective in charging or discharging the cell. Rather, it may be mostly reactive in nature and most of the energy may be returned by the capacitance or dissipated in the resistance. 
     The inventors have further recognized and appreciated that a cell grows and shrinks in thickness with every cycle and that a portion of the growth is retained each cycle. This growth and shrinkage can be measured by monitoring the pressure and/or size change of the cell directly. These are additional inputs that may be used when determining SOC and SOH, and they can also be used in determining how to charge the cell. 
     In some embodiments, the controller may control charging of the cell based on the characteristic(s) of the cell. For example, if the cell has had a discharge cycle or history of discharging at a certain discharge rate or current (such as 300 mA) at least for a portion of the previous discharge cycle, the cell may be controlled to charge at a lower rate or current (such as at 150 mA or 75 mA) for at least a portion of the charge cycle. 
     In some embodiments including an induced discharge, the controller may control the cell such that, for at least a portion of the charge cycle (such as 5% of the cycle), the cell is charged at a charging rate or current that is lower than a discharging rate or current of at least a portion of a previous discharge cycle other than (i.e., not including) the induced discharge. 
     As another example, the controller may terminate usage of the cell if an applied anisotropic pressure falls below a threshold, which may indicate that the pressure applying system (examples of which are described in more detail below) is damaged. For example, in some embodiments such a threshold may be 1% to 50% of nominal applied anisotropic pressure. Alternatively or additionally, the controller may terminate usage of the cell if pressure is too high or the thickness has been increasing faster than a threshold rate. For example, in some embodiments such a threshold rate may be 1% to 3% of thickness increase or more per cycle. 
       FIG.  1 F  depicts a representative battery management system  100 . In some embodiments, such as embodiments having multiple cells, representative system  100  may include a multiplexing switch apparatus (e.g.,  112 ), a controller (e.g.,  114 ), one or more sensors (e.g.,  116 ), and one or more batteries (e.g.,  120 ,  130 ,  140 ,  150 , and so on). It should be appreciated that although only a single multiplexing switch apparatus  112 , controller  114 , sensor  116 , and only four batteries  120 - 150  are shown in  FIG.  1 F , any suitable number of these components may be used. Any of numerous different modes of implementation may be employed. Furthermore, although a label in the singular is used herein to reference a multiplexing switch apparatus, it should be appreciated that the components used for the multiplexing and switching described herein may be distributed across any suitable number of devices (e.g., switches). 
     According to some embodiments, the battery or batteries may include at least one lithium-metal battery. Additionally, the battery or batteries (e.g.,  120 - 150 ) may respectively include one or more cell sets (e.g.,  121 - 124 ,  131 - 132 ,  141 - 142 ,  151 - 152 , and so on), referred to also as sets of cells. In some embodiments, two or more sets of cells are included in each battery, such as  121 - 122  and so on. Additionally, each set of cells (e.g., cell set  121 ) may include one or more cells (e.g.,  121 A- 121 C). In some embodiments, each set of cells may have a single cell. Alternatively, each set of cells may include multiple cells and may form a cell “block,” or multiple sets of cells may together form a cell block. Additionally, each cell (either in a battery, all the batteries in a battery pack, or in a set of cells) or set of cells may utilize the same electrochemistry. That is to say, in some embodiments, each cell may make use of the same anode active material and the same cathode active material. 
     In some embodiments, a multiplexing switch apparatus (e.g.,  112 ) may include an array of switches, such as those further described in relation to  FIGS.  3 A and  3 B  below. Additionally, the multiplexing switch apparatus may be connected to each set of cells and/or to each cell individually. In some embodiments, the controller, such as  114 , may use the multiplexing switch apparatus to selectively discharge the cells or sets of cells based on at least one criterion. 
     For example, the criterion may include a sequence in which to discharge the cells or sets of cells, such as a predefined numbering or order associated with the sets of cells (e.g., starting with a first set, switching through each set to the last set, and then starting over with the first set), and/or an order based on the cell(s) or set(s) of cells with the next highest voltage or some other measure indicating the next strongest. The inventors have recognized and appreciated that using a sequence, especially a predefined numbering, may reduce the complexity of the operations performed by the system (e.g., a controller that is not a microprocessor) and may be usable by a wider array of systems. 
     Alternatively or additionally, the criterion may be context-sensitive, such as by considering any one or more of the following: a duration of a connection between a load and a set of cells currently connected to the load (which may be at least 0.01 seconds in some embodiments), a delivered discharge capacity at the connection, and the value of a function having one or more parameters. In certain embodiments, the criterion may not include a number of prior discharge cycles of the set of cells. 
     In some embodiments, the function may have parameters such as any one or more of the following: a capacity accumulated over several connections between the load and the set of cells, the delivered discharge capacity at the connection, a current of the set of cells, a voltage of the set of cells and/or of at least one other set of cells, a cutoff discharge voltage of the set of cells, a power of the set of cells, an energy of the set of cells, a number of charge or discharge cycles of the set of cells, an impedance of the set of cells, a rate of voltage fading of the set of cells during the connection, a temperature of the set of cells, and a pressure of the set of cells (e.g., the pressure on the cell(s) from their physical enclosure, which may indicate cell capacity and is discussed further below). According to some embodiments, the delivered discharge capacity at a single connection may be in the range from 0.01% of nominal capacity to 100% (e.g., 95%) of set nominal capacity. 
     In some embodiments, a sensor (e.g.,  116 ) may measure the criterion and/or any of the parameters of the function. For example, the sensor may include a current sensor that measures the current in amperes of a given set of cells. It should be appreciated that the criterion may be plural or singular and may relate to the currently discharging set of cells and/or may determine the next set of cells. 
     In some embodiments, the controller (e.g.,  114 ) may include one or more processors, which may be of whatever complexity is suitable for the application. For example, evaluating the function of the criterion in some embodiments may rely on a microprocessor forming part or all of the controller. 
     In some embodiments, the controller may use the multiplexing switch apparatus to selectively discharge and charge the cells or sets of cells at different, programmable rates. For example, the controller may use the multiplexing switch apparatus to selectively discharge the cells or sets of cells at a first rate at least 2 times higher than a second rate of charging the sets of cells (i.e., discharging twice as fast as charging). Alternatively or additionally, the first rate of discharging may be at least 4 times higher than the second rate of charging the sets of cells (i.e., discharging four times as fast as charging). The inventors have recognized and appreciated that such ratios of discharge rate to charge rate may improve the performance and cycle life of the cells. 
     According to some embodiments, the controller may temporally overlap the discharge of the sets of cells. For example, before a given cell or set of cells ceases discharging, another cell or set of cells may begin discharging. In some embodiments, the controller may continue to provide power from the sets of cells during switching between different sets. The inventors have recognized and appreciated that this temporal overlap of discharging and continuation of power may maintain the power requirements of the load even during transition between different cells of sets of cells, which may further improve the cycle life of the cell(s) compared to conventional techniques. Accordingly, multiple cells may discharge simultaneously during such an overlap. Additionally, such an overlap may provide smoother transition of voltage than has been possible with conventional techniques. 
     In some embodiments, the load may be at least one component of a vehicle. The vehicle may be any suitable vehicle, adapted for travel on land, sea, and/or air. For example, the vehicle may be an automobile, truck, motorcycle, boat, helicopter, airplane, and/or any other suitable type of vehicle. 
     Alternatively or additionally, the controller may use the multiplexing switch apparatus (e.g.,  112 ) to connect the sets of cells to a load in a topology employed or required by the load. 
     In some embodiments, the controller may use the multiplexing switch apparatus (e.g.,  112 ) to isolate a single set of cells for discharging while other sets of cells are not discharging. Alternatively or additionally, a single cell may be isolated at a time. For example, the controller may use the multiplexing switch apparatus to isolate a single set of cells or a single cell for discharging while the other cells or sets of cells are not discharging. For a given cycle, each cell may be discharged once before any cell is discharged twice, according to some embodiments (e.g., where sequential discharging is used, but not limited to such embodiments). 
     As for charging, in some embodiments the controller may use the multiplexing switch apparatus to charge the sets of cells, and/or cells within a set, in parallel. For example, all the cells in the cell block, battery, or batteries may be charged in parallel at a rate one-fourth of the rate of discharge. 
       FIG.  2    depicts a representative battery pack  210 . In some embodiments, representative battery pack  210  may include a switching control system (e.g.,  218 ) and one or more batteries (e.g.,  120 ,  130 ,  140 ,  150 , and so on). It should be appreciated that although only a single switching control system  218  and only four batteries  120 - 150  are shown in  FIG.  2   , any suitable number of these components may be used. Any of numerous different modes of implementation may be employed. Furthermore, although a label in the singular is used herein to reference a switching control system, it should be appreciated that the components used for the control and switching described herein may be distributed across any suitable number of devices (e.g., switches, controller(s), etc.). 
     In some embodiments, a switching control system (e.g.,  218 ) may include an array of switches, such as those further described in relation to  FIGS.  3 A and  3 B  below, and it may include a controller. Additionally, the switching control system may be connected to each set of cells and/or to each cell of the batteries individually, as discussed regarding  FIG.  1 F  above. In some embodiments, the switching control system may be integrated into the battery pack. Additionally, the switching control system may control the switch(es) (such as in a switch array) to discharge the cells or sets of cells sequentially, such as in a predefined order associated with the cells or sets of cells. Alternatively or additionally, the switching control system may control the switch(es) to discharge the cells or sets of cells based on any one or more of the following: a duration of a connection between a load and a set of cells currently connected to the load (which may be at least 0.01 seconds in some embodiments), a delivered discharge capacity at the connection, and the value of a function. In certain embodiments, the basis for the control may not include a number of prior discharge cycles of the set of cells. 
     According to some embodiments, the switching control system may perform any number of other functions, such as those of the controller described in relation to  FIGS.  1 A and  1 F  above. 
     It should be appreciated that any of the components of representative system  100  or representative battery pack  210  may be implemented using any suitable combination of hardware and/or software components. As such, various components may be considered a controller that may employ any suitable collection of hardware and/or software components to perform the described function. 
       FIG.  3 A  depicts a representative battery management system  300 . In some embodiments, representative system  300  may include any suitable number of multi-cell blocks (e.g.,  321 - 325 ), a battery cell block arrangement and balance switch configuration (e.g.,  326 ), a battery management microcontroller (e.g.,  327 ), a battery system interface (e.g.,  328 ), battery power terminals (e.g.,  329 ), and a sensor (e.g.,  360 ). The multi-cell blocks may be connected to the battery cell block arrangement and balance switch configuration. The multi-cell blocks may also be connected to the battery management microcontroller. 
     In some embodiments, the battery cell block arrangement and balance switch configuration may include switch multiplexing, which may connect the cell blocks (e.g.,  321 - 325 ) in the series, parallel, serial/parallel, or any other suitable topology required to meet the voltage and current requirements of a given application or load. 
     According to some embodiments, the battery management microcontroller may monitor and control the charging and discharging of the battery management system to ensure the safe operation of the system and its components. Additionally, the battery management microcontroller may communicate with a user (e.g., a consumer using the system to power a load) as well as with any suitable internal production, calibration, and test equipment. For example, the battery management microcontroller may be connected to the battery system interface (e.g.,  328 ), which may provide the interface required for the battery management microcontroller to communicate with the user as well as internal production, calibration, and test equipment, and any other suitable entity. 
     In some embodiments, the sensor may be connected to the battery cell block arrangement and balance switch configuration, the battery management microcontroller, and/or the battery power terminals, and it may the measure attributes of the multi-cell blocks and/or any other component of the system. For example, the sensor may measure attributes of the multi-cell blocks that form a criterion and/or any of the parameters of a function as described above. For example, the sensor may include a current sensor that measures the current in amperes of a given set of cells. 
     It should be appreciated that although battery cell block arrangement and balance switch configuration  326 , battery management microcontroller  327 , battery system interface  328 , and sensor  360  appear in singular form, and only five multi-cell blocks  321 - 325  are shown in  FIG.  3 A , any suitable number of these components may be used and they may represent multiple components. Any of numerous different modes of implementation may be employed. Indeed, although a label in the singular is used herein to reference a battery cell block arrangement and balance switch configuration, it should be appreciated that the components used for the arrangement and balance switching described herein may be distributed across any suitable number of devices (e.g., switches). 
       FIG.  3 B  depicts a representative cell set and corresponding components. In some embodiments, the representative cell set may include any suitable number of cells (e.g.,  321 A-C) and may constitute a multi-cell block, such as is described above. Additionally, the representative cell set may include cell multiplexing switches (e.g.,  326 A 1 ), cell balance switches and resistors (e.g.,  326 A 2 ), a cell block microcontroller (e.g.,  327 A), a battery management microcontroller interface (e.g.,  328 A), a sensor (e.g.,  360 A), and an input/output bus for the cell set (e.g.,  321 IO). In some embodiments, the cells may be connected to the cell balance switches and resistors, which may be connected to the cell multiplexing switches. 
     In some embodiments, each cell (e.g., each of  321 A-C) may be connected to an array of the cell multiplexing switches, which may connect or isolate the given cell(s) from the input/output bus (e.g.,  321 IO), and which may connect or disconnect the given cell(s) to a balance resistor (e.g., one of the resistors in  326 A 2 ) that shares the balance bus with the other cells. Additionally, in discharge mode one cell (e.g.,  321 A) may be connected to the input/output bus and disconnected from the balance resistor. The remaining cells (e.g.,  321 B-C) may be disconnected from the input/output bus and connected to the corresponding balance resistor(s). Additionally, in charge mode for some embodiments, all cells (e.g.,  321 A-C) may be connected to the input/output bus and disconnected from the balance resistors  326 A 2 . 
     According to some embodiments, the cell block microcontroller (e.g.,  327 A) may generate switching waveforms to ensure that overlap and deadband requirements for the switching is appropriate for the application or load. Additionally, the cell block microcontroller may determine the state required by the application or load by monitoring the cell block&#39;s voltage and current, as well as by receiving communication from a battery management microcontroller (e.g.,  327  in  FIG.  3 A ), to which the cell block microcontroller may be connected via the battery management microcontroller interface. 
       FIG.  3 C  is an exemplary cross-sectional schematic illustration of an electrochemical system in which an anisotropic force is applied to an electrochemical cell (e.g.,  321 A), according to one set of embodiments. The term “electrochemical cell” is used herein to generally refer to an anode, a cathode, and an electrolyte configured to participate in an electrochemical reaction to produce power. An electrochemical cell can be rechargeable or non-rechargeable. 
     In  FIG.  3 C , the system may include electrochemical cell  321 A and, in some embodiments, a pressure distributor  334  containing a fluid associated with electrochemical cell  321 A. Pressure distributor  334  can be configured such that an anisotropic force is applied to a component of electrochemical cell  321 A through pressure distributor  334 . For example, in the set of embodiments illustrated in  FIG.  3 C , pressure transmitter  336  can be configured to apply an anisotropic force to pressure distributor  334 , which in turn causes an anisotropic force to be applied to at least one component (e.g., an electrode) of electrochemical cell  321 A. The system can also include a substrate  332  on which the electrochemical cell is positioned. Substrate  332  can comprise, for example, a tabletop, a surface of a container in which electrochemical cell  321 A is housed, or any other suitable surface. 
     Pressure distributor  334  can be associated with electrochemical cell  321 A in a variety of suitable configurations to produce the inventive systems and methods described herein. As used herein, a pressure distributor is associated with an electrochemical cell when at least a portion of a force that is applied to and/or through the pressure distributor can be transmitted to a component of the electrochemical cell. For example, in certain embodiments, a pressure distributor is associated with an electrochemical cell when the pressure distributor is in direct contact with the electrochemical cell or a component thereof. Generally, a first article and a second article are in direct contact when the first article and the second article are directly touching. For example, in  FIG.  3 C , pressure distributor  334  and the electrochemical cell  321 A are in direct contact. 
     In certain embodiments, a pressure distributor is associated with the electrochemical cell when the pressure distributor is in indirect contact with at least one component of the electrochemical cell. Generally, a first article and a second article are in indirect contact when a pathway can be traced between the first article and the second article that intersects only solid and/or liquid components. Such a pathway can be in the form of a substantially straight line, in certain embodiments. A pressure distributor can be in indirect contact with an electrochemical cell, in certain embodiments, when one or more solid and/or liquid materials are positioned between them, but a force can still be transmitted to the electrochemical cell through the pressure distributor. 
     In certain embodiments, a pressure distributor is associated with an electrochemical cell when it is located within the boundaries of a container at least partially (e.g., completely) enclosing the components of the electrochemical cell. For example, in certain embodiments, pressure distributor  334  could be positioned between an electrode and a container at least partially enclosing the electrochemical cell. In certain embodiments, pressure distributor  334  could be positioned between a current collector and a container at least partially enclosing the electrochemical cell. In some embodiments, pressure distributor  334  can be used as a current collector, for example, positioned next to an electrode of the electrochemical cell and within a container at least partially containing the electrodes and electrolyte of the electric cell. This could be achieved, for example, by fabricating pressure distributor  334  from a material (e.g., a metal such as a metal foil, a conductive polymer, and the like) that is sufficiently electrically conductive to transport electrons to and/or from an electrode of the electrochemical cell. 
     In some embodiments, a pressure distributor is associated with an electrochemical cell when it is located outside the boundaries of a container at least partially (e.g., completely) enclosing the components of the electrochemical cell. For example, in certain embodiments, pressure distributor  334  could be positioned in direct or indirect contact with an exterior surface of a container at least partially enclosing the electrodes and electrolyte of an electrochemical cell. 
     In certain embodiments, the pressure distributor can be located a relatively short distance from at least one electrode of an electrochemical cell. For example, in certain embodiments, the shortest distance between the pressure distributor and an electrode of the electrochemical cell is less than about 10 times, less than about 5 times, less than about 2 times, less than about 1 time, less than about 0.5 times, or less than about 0.25 times the maximum cross-sectional dimension of that electrode. 
     In some embodiments, a pressure distributor can be associated with a particular electrode (e.g., an anode) of an electrochemical cell. For example, a pressure distributor can be in direct or indirect contact with an electrode (e.g., an anode such as an anode comprising lithium) of an electrochemical cell. In certain embodiments, the pressure distributor can be positioned outside a container at least partially containing the electrode but still associated with the electrode, for example, when only liquid and/or solid components separate the electrode from the pressure distributor. For example, in certain embodiments in which the pressure distributor is positioned in direct or indirect contact with a container at least partially enclosing the electrode and a liquid electrolyte, the pressure distributor would be associated with the electrode. 
     In certain embodiments, a force can be applied to electrochemical cell  321 A or a component of electrochemical cell  321 A (e.g., an electrode of the electrochemical cell) through pressure distributor  334 . As used herein, a force is applied to a first component (e.g., an electrochemical cell) through a second component (e.g., a pressure distributor) when the second component at least partially transmits a force from the source of the force to the first component. 
     A force can be applied to an electrochemical cell or a component thereof through a pressure distributor in a variety of ways. In certain embodiments, applying a force to a pressure distributor comprises applying a force to an external surface of the pressure distributor. This can be achieved, for example, via pressure transmitter  336 . For example, in  FIG.  3 C , pressure transmitter  336  can be positioned to apply an anisotropic force to electrochemical cell  321 A through pressure distributor  334  by applying a force to surface  340  of pressure distributor  334 . As used herein, a first component is positioned to apply an anisotropic force to a second component when the first and second components are positioned such that at least a portion of a force that is applied to and/or through the first component can be transmitted to the second component. In certain embodiments, pressure transmitter and the pressure distributor are in direct contact. In some embodiments, one or more materials (e.g., one or more solid and/or liquid materials) are positioned between the pressure transmitter and the pressure distributor, but a force can still be applied to the pressure distributor by the pressure transmitter. In certain embodiments, the pressure transmitter and the pressure distributor can be in indirect contact such that a continuous pathway can be traced through solid and/or liquid materials from the pressure distributor to the electrochemical cell. Such a pathway can be substantially (e.g., completely) straight, in certain embodiments. 
     In the set of embodiments illustrated in  FIG.  3 C , pressure transmitter  336  and electrochemical cell  321 A are positioned on opposite sides of pressure distributor  334 . Accordingly, when an anisotropic force (e.g., an anisotropic force in the direction of arrow  150 ) is applied to and/or by pressure transmitter  336  to surface  340 , the force can be transmitted through pressure distributor  334  onto surface  342  of electrochemical cell  321 A, and to the components of electrochemical cell  321 A. 
     In some embodiments, applying a force to a pressure distributor comprises applying a force to an internal surface of the pressure distributor. For example, in certain embodiments, a force can be applied through the pressure distributor to the electrochemical cell by maintaining and/or increasing the pressure of the fluid within the pressure distributor. In the set of embodiments illustrated in  FIG.  3 C , a force can be applied through pressure distributor  334  to electrochemical cell  321 A by transporting additional fluid through an inlet (not shown) of pressure distributor  334  (e.g., by inflating pressure distributor  334 ). In some such embodiments, when the pressure within a pressure distributor is maintained and/or increased, the movement of pressure transmitter can be restricted such that a force is produced on an external surface of the electrochemical cell and/or on a component of the electrochemical cell (e.g., an active surface of an electrode within the electrochemical cell). For example, in  FIG.  3 C , as additional fluid is added to pressure distributor  334 , pressure transmitter  336  can be configured to restrict the movement of the boundaries of pressure distributor  334  such that a force is applied to surface  342  of electrochemical cell  321 A. 
     In certain embodiments, fluid can be added to pressure distributor  334  before it is positioned between electrochemical cell  321 A and pressure transmitter  336 . After the fluid has been added, pressure distributor  334  can be compressed and positioned between electrochemical cell  321 A and pressure transmitter  336 , after which, the compression of the fluid within pressure distributor  334  can produce a force that is applied to surface  342  of electrochemical cell  321 A (and, accordingly, to a surface of one or more components of the electrochemical cell, such as an active surface of an electrode). One of ordinary skill in the art, given the present disclosure, would be capable of designing additional systems and methods by which a force can be applied to an electrochemical cell through a pressure distributor. 
     The fluid within pressure distributor  334  can allow the pressure that is transmitted through pressure distributor  334  to be applied relatively evenly across the surface  342  of electrochemical cell  321 A (and, accordingly, relatively evenly across a surface of one or more components of the electrochemical cell, such as an active surface of an electrode). Not wishing to be bound by any particular theory, it is believed that a presence of a fluid within pressure distributor  334  reduces and/or eliminates points of relatively high pressure on surface  342  as fluid within relatively high pressure regions is transported to regions of relatively low pressure. 
     In some embodiments, the degree to which the pressure distributor evenly distributes the force applied to electrochemical cell can be enhanced if the external surface of the pressure transmitter is appropriately aligned with an external surface of the electrochemical cell or a container thereof. For example, in the set of embodiments illustrated in  FIG.  3 C , external surface  340  of pressure transmitter  336  faces external surface  342  of electrochemical cell  321 A. In certain embodiments, the external surface of the pressure transmitter is substantially parallel to the external surface of the electrochemical cell to which a force is applied. For example, in the set of embodiments illustrated in  FIG.  3 C , external surface  340  of pressure transmitter  336  is substantially parallel to external surface  342  of electrochemical cell  321 A. As used herein, two surfaces are substantially parallel to each other when the two surfaces form angles of no greater than about 10 degrees. In certain embodiments, two substantially parallel surfaces form angles of no greater than about 5 degrees, no greater than about 3 degrees, no greater than about 1 degree, or no greater than about 0.1 degree. 
     The pressure distributor can have a variety of suitable forms. In certain embodiments, the pressure distributor can comprise a bag or other suitable container in which a fluid is contained. In some embodiments, the pressure distributor can comprise a bellows that is configured to deform along the direction in which the force is applied to the pressure distributor. 
     The pressure distributor container can be made of a variety of materials. In certain embodiments, the pressure distributor container can comprise a flexible material. For example, in certain embodiments, the pressure distributor container can comprise a polymer such as polyethylene (e.g., linear low density and/or ultra-low density polyethylene), polypropylene, polyvinylchloride, polyvinyldichloride, polyvinylidene chloride, ethylene vinyl acetate, polycarbonate, polymethacrylate, polyvinyl alcohol, nylon, silicone rubber (e.g., polydimethylsiloxane), and/or other natural or synthetic rubbers or plastics. In certain embodiments (e.g., in embodiments in which a gas is used as the fluid within the pressure distributor), the pressure distributor container can include a metal layer (e.g., an aluminum metal layer), which can enhance the degree to which fluid (e.g., a gas) is retained within the pressure distributor. The use of flexible materials can be advantageous, in certain embodiments, as they may allow for redistribution of the contents of the pressure distributor relatively easily, enhancing the degree to which the force is uniformly applied. 
     In some embodiments, the pressure distributor can comprise an elastic material. In certain embodiments, the elasticity of the material from which the pressure distributor is fabricated can be selected such that the pressure distributor transmits a desirable amount of a force applied to the pressure distributor to an adjacent component. To illustrate, in certain cases, if the pressure distributor is made of a very flexible material, a relatively high percentage of the force applied to the pressure distributor might be used to elastically deform the pressure distributor material, rather than being transmitted to an adjacent electrochemical cell. In certain embodiments, the pressure distributor can be formed of a material having a Young&#39;s modulus of less than about 1 GPa. One of ordinary skill in the art would be capable of measuring the Young&#39;s modulus of a given material by performing, for example, a tensile test (also sometimes referred to a tension test). Exemplary elastic polymers (i.e., elastomers) that could be used include the general classes of silicone polymers, epoxy polymers, and acrylate polymers. 
     In certain embodiments, the pressure distributor comprises an enclosed container containing a fluid. The pressure distributor can comprise an open container containing a fluid, in certain embodiments. For example, in some embodiments, the pressure distributor comprises a container fluidically connected to a device constructed and arranged to transport the fluid through the pressure distributor, as described in more detail below. 
     A variety of fluids can be used in association with the pressure distributor. As used herein, a “fluid” generally refers to a substance that tends to flow and to conform to the outline of its container. Examples of fluids include liquids, gases, gels, viscoelastic fluids, solutions, suspensions, fluidized particulates, and the like. Typically, fluids are materials that are unable to withstand a static shear stress, and when a shear stress is applied, the fluid experiences a continuing and permanent distortion. The fluid may have any suitable viscosity that permits flow and redistribution of an applied force. 
     In certain embodiments, the fluid within the pressure distributor comprises a gas (e.g., air, nitrogen, a noble gas (e.g., helium, neon, argon, krypton, xenon), a gas refrigerant, or mixtures of these). In certain embodiments, the gas within the pressure distributor can comprise a relatively high molecular weight (e.g., at least about 100 g/mol), which can limit the degree to which gas permeates through the walls of the pressure distributor. In some embodiments, the fluid within the pressure distributor comprises a liquid including, but not limited to, water, an electrolyte (e.g., a liquid electrolyte similar or identical to that used in the electrochemical cell), greases (e.g., petroleum jelly, Teflon grease, silicone grease), oils (e.g., mineral oil), and the like. In certain embodiments, the fluid within the pressure distributor comprises a gel. Suitable gels for use within the pressure distributor include, but are not limited to, hydrogels (e.g., silicone gel), organogels, or xerogels. In certain embodiments, the fluid comprises a fluidized bed of solid particles (e.g., sand, powders, and the like). Fluidization can be achieved, for example, by passing a gas and/or a liquid through the particles and/or by vibrating a substrate on which the particles are positioned such that the particles move relative to each other. 
     The fluid used in association with the pressure distributor can have any suitable viscosity. In certain embodiments, a Newtonian fluid can be used within the pressure distributor, although some embodiments are not so limited, and non-Newtonian fluids (e.g., a shear thinning fluid, a shear thickening fluid, etc.) can also be used. In certain embodiments, the pressure distributor can contain a Newtonian fluid with a steady-state shear viscosity of less than about 1×10 7  centipoise (cP), less than about 1×10 6  cP, less than about 1×10 5  cP less than about 1000 cP, less than about 100 cP, less than about 10 cP, or less than about 1 cP (and, in some embodiments, greater than about 0.001 cP, greater than about 0.01 cP, or greater than about 0.1 cP) at room temperature. 
     In certain embodiments, the fluid within the pressure distributor can be selected such that it is suitable for being transported into and/or out of the pressure distributor. For example, in certain embodiments, fluid may be transported into the pressure distributor to apply an anisotropic force to the electrochemical cell (e.g., by compressing the fluid within the pressure distributor when it is positioned between the electrochemical cell and the pressure transmitter). As another example, a fluid may be transported into and/or out of a pressure distributor to transfer heat to and/or away from a component of the system. 
     Pressure transmitter  336  can also adopt a variety of configurations. In certain embodiments, pressure transmitter  336  is moveable relative to electrochemical cell  321 A. In some such embodiments, a force can be applied to electrochemical cell  321 A through pressure distributor  334  by moving pressure transmitter  336  closer to electrochemical cell  321 A and/or maintaining the separation between electrochemical cell  321 A and pressure transmitter  336 . As one particular example, in some embodiments the pressure transmitter  336  includes a compression spring, a first applicator structure, and a second applicator structure. First applicator structure can correspond to, for example, a flat plate of rigid material, or any other suitable structure. Second applicator structure can correspond to, for example, a second plate of rigid material, a portion of a wall of a container in which the electrochemical cell is housed, or any other suitable structure. In some embodiments, a force can be applied to surface  342  of electrochemical cell  321 A when a compression spring is compressed between applicator structure and applicator structure. In certain embodiments, Belleville washers, machine screws, pneumatic devices, weights, air cylinders, and/or hydraulic cylinders could be used in place of, or in addition to, the compression spring. In some embodiments, a force can be applied to an electrochemical cell using a constricting element (e.g., an elastic band, a turnbuckle band, etc.) arranged around one or more external surfaces of the electrochemical cell. A variety of suitable methods for applying a force to an electrochemical cell are described, for example, in U.S. Patent Publication No. 2010/0035128 to Scordilis-Kelley et al. filed on Aug. 4, 2009, entitled “Application of Force in Electrochemical Cells,” which is incorporated herein by reference in its entirety for all purposes. 
     In certain embodiments, pressure transmitter  336  is not substantially moveable relative to electrochemical cell  321 A, and a force can be applied to the electrochemical cell, for example, by pressurizing the pressure distributor  334 . In some such embodiments, pressurizing the pressure distributor can result in the application of a force to the electrochemical cell because the substantially immovable pressure transmitter  336  restricts the movement of one or more of the boundaries of pressure distributor  334 , thereby applying an anisotropic force to electrochemical cell  321 A. 
     In certain embodiments, pressure transmitter comprises all or part of a substantially rigid structure (e.g., a package enclosing an electrochemical cell), and the movement of the pressure transmitter can be restricted by the degree to which the substantially rigid structure is inflexible. In certain embodiments, the pressure transmitter can comprise a structure that is integrated with at least a portion of the other components of the system, which can restrict its movement. For example, in certain embodiments, the pressure transmitter can comprise at least a portion of one or more walls of a package within which electrochemical cell  321 A and pressure distributor  334  are positioned. As one particular example, pressure transmitter  336  might form a first wall of a package containing electrochemical cell  321 A while substrate  332  forms a second wall (e.g., opposite to the first wall) of the package. In certain embodiments, the movement of pressure transmitter  336  can be restricted by applying a force within and/or on the pressure transmitter such that its movement is restricted. In any of these cases, a force can be applied to the electrochemical cell, in certain embodiments, by adding fluid to and/or maintaining the amount of fluid within pressure distributor  334 . 
       FIG.  3 C  illustrates a set of embodiments in which a single pressure transmitter and a single pressure distributor are used to apply a force to an electrochemical cell. In certain embodiments, however, more than one pressure distributor and/or more than one pressure transmitter can be employed. For example, in some embodiments, the system includes a second pressure distributor positioned under electrochemical cell  321 A and a second pressure transmitter positioned under the second pressure distributor. In certain embodiments, a substantially evenly distributed force can be applied to an external surface of electrochemical cell  321 A through the second pressure distributor, for example, by applying a force to and/or through the second pressure transmitter and onto a surface of the second pressure distributor. 
     In some embodiments, fluid can be transported into and/or out of the pressure distributor to transport heat to and/or away from electrochemical cell  321 A. For example, pressure distributor  334  may include an inlet and an outlet configured to transport a fluid through pressure distributor  334 . As fluid is transported through pressure distributor  334 , it can absorb heat from electrochemical cell  321 A and transport it away from the system via the outlet. Any suitable device can be used to transport the fluid through the pressure distributor such as, for example, a pump, a vacuum, or any other suitable device. 
     In certain embodiments, the fluid used in association with the pressure distributor can be selected such that it cools or heats the system to a desired degree. For example, in certain embodiments, the fluid within the pressure distributor can comprise a coolant such as water, ethylene glycol, diethylene glycol, propylene glycol, polyalkylene glycols (PAGs), oils (e.g., mineral oils, castor oil, silicone oils, fluorocarbon oils, and/or refrigerants (e.g., freons, chlorofluorocarbons, perfluorocarbons, and the like). 
     The embodiments described herein can be used with a variety of electrochemical cells. While primary (disposable) electrochemical cells and secondary (rechargeable) electrochemical cells can be used in association with the embodiments described herein, some embodiments advantageously make use of secondary electrochemical cells, for example, due to the benefits provided by uniform force application during the (re)charging process. In certain embodiments, the electrochemical cell comprises a lithium-based electrochemical cell such as a lithium-sulfur electrochemical cell (and assemblies of multiple cells, such as batteries thereof). 
     Although some embodiments can find use in a wide variety of electrochemical devices, an example of one such device is provided in  FIG.  3 D  for illustrative purposes only. In  FIG.  3 D , a general embodiment of electrochemical cell  321 A includes cathode  310 , anode  312 , and electrolyte  314  in electrochemical communication with the cathode and the anode. 
     In some cases, electrochemical cell  321 A may optionally be at least partially contained by containment structure  316 . Containment structure  316  may comprise a variety of shapes including, but not limited to, cylinders, prisms (e.g., triangular prisms, rectangular prisms, etc.), cubes, or any other shape. In certain embodiments, a pressure distributor can be associated with electrochemical cell  321 A by positioning the pressure distributor outside containment structure  316 , in either direct or indirect contact with surface  318 A and/or surface  318 B. When positioned in this way, the pressure distributor can be configured to apply a force, directly or indirectly, to surfaces  318 A and/or  318 B of containment structure  316 , as described above. In certain embodiments, a pressure distributor can be positioned between cathode  310  and containment structure  316 , or between anode  312  and containment structure  316 . In some such embodiments, containment structure can act as a pressure transmitter and/or a separate pressure transmitter can be configured to apply a force to the pressure distributor via the containment structure. 
     A typical electrochemical cell system also would include, of course, current collectors, external circuitry, and the like. Those of ordinary skill in the art are well aware of the many arrangements that can be utilized with the general schematic arrangement as shown in the figures and described herein. 
     The components of electrochemical cell  321 A may be assembled, in some cases, such that the electrolyte is located between the cathode and the anode in a planar configuration. For example, in the embodiments illustrated in  FIG.  3 D , cathode  310  of electrochemical cell  321 A is substantially planar. A substantially planar cathode can be formed, for example, by coating a cathode slurry on a planar substrate, such as a metal foil or other suitable substrate, which may be included in the assembly of electrochemical cell  321 A (although not illustrated in  FIG.  3 D ) or removed from cathode  310  prior to assembly of the electrochemical cell. In addition, in  FIG.  3 D , anode  312  is illustrated as being substantially planar. A substantially planar anode can be formed, for example, by forming a sheet of metallic lithium, by forming an anode slurry on a planar substrate, or by any other suitable method. Electrolyte  314  is also illustrated as being substantially planar in  FIG.  3 D . 
     In certain embodiments, electrochemical cell  321 A can comprise an electrode that comprises a metal such as an elemental metal and/or a metal alloy. As one particular example, in certain embodiments, electrochemical cell  321 A can comprise an anode comprising elemental lithium (e.g., elemental lithium metal and/or a lithium alloy). In certain embodiments, the anisotropic force applied to the electrochemical cell is sufficiently large such that the application of the force affects the surface morphology of the metal within an electrode of the electrochemical cell, as described in more detail below. 
     While  FIG.  3 D  illustrates an electrochemical cell arranged in a planar configuration, it is to be understood that any electrochemical cell arrangement can be constructed, employing the principles of some embodiments, in any configuration. In addition to the shape illustrated in  FIG.  3 D , the electrochemical cells described herein may be of any other shape including, but not limited to, cylinders, a folded multi-layer structure, prisms (e.g., triangular prisms, rectangular prisms, etc.), “Swiss-rolls,” non-planar multi-layered structures, etc. Additional configurations are described in U.S. patent application Ser. No. 11/400,025, filed Apr. 6, 2006, entitled, “Electrode Protection in both Aqueous and Non-Aqueous Electrochemical Cells, including Rechargeable Lithium Batteries,” to Affinito et al., which is incorporated herein by reference in its entirety. 
     In some embodiments, the cathode and/or the anode comprise at least one active surface. As used herein, the term “active surface” is used to describe a surface of an electrode that is in physical contact with the electrolyte and at which electrochemical reactions may take place. For example, in the set of embodiments illustrated in  FIG.  3 D , cathode  310  includes cathode active surface  320  and anode  312  includes anode active surface  322 . 
     In certain embodiments, the anisotropic force applied to a pressure transmitter  336  and/or through pressure distributor  334  (and eventually in some cases to surface  342  of electrochemical cell  321 A) comprises a component normal to the active surface of an electrode (e.g., an anode such as an anode containing lithium metal) within the electrochemical cell. Accordingly, applying an anisotropic force through pressure distributor  334  to the electrochemical cell can result in an anisotropic force being applied to an active surface of an electrode (e.g., an anode) within the electrochemical cell. In the case of a planar electrode surface, the applied force may comprise an anisotropic force with a component normal to the electrode active surface at the point at which the force is applied. For example, referring to the set of embodiments illustrated in  FIG.  3 C  and  FIG.  3 D , an anisotropic force in the direction of arrow  370  may be applied to electrochemical cell  321 A through pressure distributor  334 . An anisotropic force applied in the direction of arrow  370  would include a component  372  that is normal to anode active surface  322  and normal to cathode active surface  320 . In addition, an anisotropic force applied in the direction of arrow  370  would include a component  374  that is not normal (and is in fact parallel) to anode active surface  322  and cathode active surface  320 . 
     In the case of a curved surface (e.g., a concave surface or a convex surface), the force applied to the electrochemical cell may comprise an anisotropic force with a component normal to a plane that is tangent to the curved surface at the point at which the force is applied. 
     In one set of embodiments, systems and methods are configured such that, during at least one period of time during charge and/or discharge of the cell, an anisotropic force with a component normal to the active surface of an electrode (e.g., the anode) is applied to the electrochemical cell. In some embodiments, the force may be applied continuously, over one period of time, or over multiple periods of time that may vary in duration and/or frequency. 
     The magnitude of the applied force is, in some embodiments, large enough to enhance the performance of the electrochemical cell. In certain embodiments, an electrode active surface (e.g., an anode active surface) and the anisotropic force may be together selected such that the anisotropic force affects surface morphology of the electrode active surface to inhibit an increase in electrode active surface area through charge and discharge and wherein, in the absence of the anisotropic force but under otherwise essentially identical conditions, the electrode active surface area is increased to a greater extent through charge and discharge cycles. “Essentially identical conditions,” in this context, means conditions that are similar or identical other than the application and/or magnitude of the force. For example, otherwise identical conditions may mean a cell that is identical, but where it is not constructed (e.g., by brackets or other connections) to apply the anisotropic force on the subject electrochemical cell. 
     The electrode active surface and anisotropic force can be selected together, to achieve results described herein, easily by those of ordinary skill in the art. For example, where the electrode active surface is relatively soft, the component of the force normal to the electrode active surface may be selected to be lower. Where the electrode active surface is harder, the component of the force normal to the electrode active surface may be greater. Those of ordinary skill in the art, given the present disclosure, can easily select anode materials, alloys, mixtures, etc. with known or predictable properties, or readily test the hardness or softness of such surfaces, and readily select cell construction techniques and arrangements to provide appropriate forces to achieve what is described herein. Simple testing can be done, for example by arranging a series of active materials, each with a series of forces applied normal (or with a component normal) to the active surface, to determine the morphological effect of the force on the surface without cell cycling (for prediction of the selected combination during cell cycling) or with cell cycling with observation of a result relevant to the selection. 
     As noted above, in some embodiments, an anisotropic force with a component normal to an electrode active surface (e.g., of the anode) is applied, during at least one period of time during charge and/or discharge of the cell, to an extent effective to inhibit an increase in surface area of the electrode active surface relative to an increase in surface area absent the anisotropic force. The component of the anisotropic force normal to the electrode active surface may, for example, define a pressure of at least about 20, at least about 25, at least about 35, at least about 40, at least about 50, at least about 75, at least about 90, at least about 100, at least about 125, at least about 150, at least about 200, at least about 300, at least about 400, or at least about 500 Newtons per square centimeter. In certain embodiments, the component of the anisotropic force normal to the anode active surface may, for example, define a pressure of less than about 500, less than about 400, less than about 300, less than about 200, less than about 190, less than about 175, less than about 150, less than about 125, less than about 115, or less than about 110 Newtons per square centimeter. While forces and pressures are generally described herein in units of Newtons and Newtons per unit area, respectively, forces and pressures can also be expressed in units of kilograms-force and kilograms-force per unit area, respectively. One of ordinary skill in the art will be familiar with kilogram-force-based units, and will understand that 1 kilogram-force is equivalent to about 9.8 Newtons. 
     In certain embodiments, the component of the anisotropic force normal to the active surface of an electrode within the electrochemical cell defines a pressure that is at least about 50%, at least about 75%, at least about 100%, at least about 120% of the yield stress of that electrode (e.g., during charge and/or discharge of the electrochemical cell). In certain embodiments, the component of the anisotropic force normal to the active surface of an electrode within the electrochemical cell defines a pressure that is less than about 250% or less than about 200% of the yield stress of that electrode (e.g., during charge and/or discharge of the electrochemical cell). For example, in some embodiments, the electrochemical cell can comprise an anode (e.g., an anode comprising lithium metal and/or a lithium alloy), and the component of an applied anisotropic force that is normal to the anode active surface can define a pressure that is at least about 50%, at least about 75%, at least about 100%, or at least about 120% of the yield stress of the anode (and/or less than about 250% or less than about 200% of the yield stress of the anode). In some embodiments, the electrochemical cell can comprise a cathode, and the component of the anisotropic force normal to the cathode active surface can define a pressure that is at least about 50%, at least about 75%, at least about 100%, or at least about 120% of the yield stress of the cathode (and/or less than about 250% or less than about 200% of the yield stress of the cathode). 
     In some cases, the anisotropic force can define a pressure that is relatively uniform across one or more external surfaces of the electrochemical cell and/or across one or more active surfaces of electrode(s) within the electrochemical cell. In some embodiments, at least about 50%, at least about 75%, at least about 85%, at least about 90%, at least about 95%, or at least about 98% of the area of one or more external surfaces of an electrochemical cell and/or of the area of one or more active surfaces of an electrode (e.g., anode) defines a uniform area that includes a substantially uniform distribution of pressure defined by an anisotropic force. In this context, a “surface of an electrochemical cell” and a “surface of an electrode” refer to the geometric surfaces of the electrochemical cell and the electrode, which will be understood by those of ordinary skill in the art to refer to the surfaces defining the outer boundaries of the electrochemical cell and electrode, for example, the area that may be measured by a macroscopic measuring tool (e.g., a ruler) and does not include the internal surface area (e.g., area within pores of a porous material such as a foam, or surface area of those fibers of a mesh that are contained within the mesh and do not define the outer boundary, etc.). 
     In some embodiments, a pressure is substantially uniformly distributed across a surface when any continuous area that covers about 10%, about 5%, about 2%, or about 1% of the uniform area (described in the preceding paragraph) includes an average pressure that varies by less than about 25%, less than about 10%, less than about 5%, less than about 2%, or less than about 1% relative to the average pressure across the entirety of the uniform area. 
     Stated another way, in some embodiments, at least about 50% (or at least about 75%, at least about 85%, at least about 90%, at least about 95%, or at least about 98%) of the area of a surface of the electrochemical cell and/or of the active area of an electrode defines a first, continuous area of essentially uniform applied pressure, the first area having a first average applied pressure. In some cases, any continuous area that covers about 10% (or about 5%, about 2%, or about 1%) of the first, continuous area of the surface of the electrochemical cell and/or of the electrode includes a second average applied pressure that varies by less than about 25% (or less than about 10%, less than about 5%, less than about 2%, or less than about 1%) relative to the first average applied pressure across the first, continuous area. 
     One of ordinary skill in the art would be capable of determining an average applied pressure within a portion of a surface, for example, by determining the force level applied at a representative number of points within the surface portion, integrating a 3-dimensional plot of the applied pressure as a function of position on the surface portion, and dividing the integral by the surface area of the surface portion. One of ordinary skill in the art would be capable of producing a plot of the applied pressure across a surface portion by, for example, using a Tekscan I-Scan system for measuring the pressure field. 
     The anodes of the electrochemical cells described herein may comprise a variety of anode active materials. As used herein, the term “anode active material” refers to any electrochemically active species associated with the anode. For example, the anode may comprise a lithium-containing material, wherein lithium is the anode active material. Suitable electroactive materials for use as anode active materials in the anode of the electrochemical cells described herein include, but are not limited to, lithium metal such as lithium foil and lithium deposited onto a conductive substrate, and lithium alloys (e.g., lithium-aluminum alloys and lithium-tin alloys). Methods for depositing a negative electrode material (e.g., an alkali metal anode such as lithium) onto a substrate may include methods such as thermal evaporation, sputtering, jet vapor deposition, and laser ablation. Alternatively, where the anode comprises a lithium foil, or a lithium foil and a substrate, these can be laminated together by a lamination process as known in the art to form an anode. 
     In one embodiment, an electroactive lithium-containing material of an anode active layer comprises greater than 50% by weight of lithium. In another embodiment, the electroactive lithium-containing material of an anode active layer comprises greater than 75% by weight of lithium. In yet another embodiment, the electroactive lithium-containing material of an anode active layer comprises greater than 90% by weight of lithium. Additional materials and arrangements suitable for use in the anode are described, for example, in U.S. Patent Publication No. 2010/0035128 to Scordilis-Kelley et al. filed on Aug. 4, 2009, entitled “Application of Force in Electrochemical Cells,” which is incorporated herein by reference in its entirety for all purposes. 
     The cathodes in the electrochemical cells described herein may comprise a variety of cathode active materials. As used herein, the term “cathode active material” refers to any electrochemically active species associated with the cathode. Suitable electroactive materials for use as cathode active materials in the cathode of the electrochemical cells of some embodiments include, but are not limited to, one or more metal oxides, one or more intercalation materials, electroactive transition metal chalcogenides, electroactive conductive polymers, sulfur, carbon and/or combinations thereof. 
     In some embodiments, the cathode active material comprises one or more metal oxides. In some embodiments, an intercalation cathode (e.g., a lithium-intercalation cathode) may be used. Non-limiting examples of suitable materials that may intercalate ions of an electroactive material (e.g., alkaline metal ions) include metal oxides, titanium sulfide, and iron sulfide. In some embodiments, the cathode is an intercalation cathode comprising a lithium transition metal oxide or a lithium transition metal phosphate. Additional examples include Li x CoO 2  (e.g., Li 1.1 CoO 2 ), Li x NiO 2 , Li x MnO 2 , Li x Mn 2 O 4  (e.g., Li 1.05 Mn 2 O 4 ), Li x CoPO 4 , Li x MnPO 4 , LiCo x Ni (1-x) O 2 , and LiCo x Ni y Mn (1-x-y) O 2  (e.g., LiNi 1/3 Mn 1/3 Co 1/3 O 2 , LiNi 3/5 Mn 1/5 Co 1/5 O 2 , LiNi 4/5 Mn 1/10 Co 1/10 O 2 , LiNi 1/2 Mn 3/10 Co 1/5 O 2 ). X may be greater than or equal to 0 and less than or equal to 2. X is typically greater than or equal to 1 and less than or equal to 2 when the electrochemical cell is fully discharged, and less than 1 when the electrochemical cell is fully charged. In some embodiments, a fully charged electrochemical cell may have a value of x that is greater than or equal to 1 and less than or equal to 1.05, greater than or equal to 1 and less than or equal to 1.1, or greater than or equal to 1 and less than or equal to 1.2. Further examples include Li x NiPO 4 , where (0&lt;x≤1), LiMn x Ni y O 4  where (x+y=2) (e.g., LiMn 1.5 Ni 0.5 O 4 ), LiNi x Co y Al z O 2  where (x+y+z=1), LiFePO 4 , and combinations thereof. In some embodiments, the electroactive material within the cathode comprises lithium transition metal phosphates (e.g., LiFePO 4 ), which can, in certain embodiments, be substituted with borates and/or silicates. 
     As noted above, in some embodiments, the cathode active material comprises one or more chalcogenides. As used herein, the term “chalcogenides” pertains to compounds that contain one or more of the elements of oxygen, sulfur, and selenium. Examples of suitable transition metal chalcogenides include, but are not limited to, the electroactive oxides, sulfides, and selenides of transition metals selected from the group consisting of Mn, V, Cr, Ti, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, and Ir. In one embodiment, the transition metal chalcogenide is selected from the group consisting of the electroactive oxides of nickel, manganese, cobalt, and vanadium, and the electroactive sulfides of iron. In one embodiment, a cathode includes one or more of the following materials: manganese dioxide, iodine, silver chromate, silver oxide and vanadium pentoxide, copper oxide, copper oxyphosphate, lead sulfide, copper sulfide, iron sulfide, lead bismuthate, bismuth trioxide, cobalt dioxide, copper chloride, manganese dioxide, and carbon. In another embodiment, the cathode active layer comprises an electroactive conductive polymer. Examples of suitable electroactive conductive polymers include, but are not limited to, electroactive and electronically conductive polymers selected from the group consisting of polypyrroles, polyanilines, polyphenylenes, polythiophenes, and polyacetylenes. Examples of conductive polymers include polypyrroles, polyanilines, and polyacetylenes. 
     In some embodiments, electroactive materials for use as cathode active materials in electrochemical cells described herein include electroactive sulfur-containing materials. “Electroactive sulfur-containing materials,” as used herein, relates to cathode active materials which comprise the element sulfur in any form, wherein the electrochemical activity involves the oxidation or reduction of sulfur atoms or moieties. The nature of the electroactive sulfur-containing materials useful in the practice of some embodiments may vary widely, as known in the art. For example, in one embodiment, the electroactive sulfur-containing material comprises elemental sulfur. In another embodiment, the electroactive sulfur-containing material comprises a mixture of elemental sulfur and a sulfur-containing polymer. Thus, suitable electroactive sulfur-containing materials may include, but are not limited to, elemental sulfur and organic materials comprising sulfur atoms and carbon atoms, which may or may not be polymeric. Suitable organic materials include those further comprising heteroatoms, conductive polymer segments, composites, and conductive polymers. 
     In some embodiments, an electroactive sulfur-containing material of a cathode active layer comprises greater than 50% by weight of sulfur. In another embodiment, the electroactive sulfur-containing material comprises greater than 75% by weight of sulfur. In yet another embodiment, the electroactive sulfur-containing material comprises greater than 90% by weight of sulfur. 
     The cathode active layers of some embodiments may comprise from about 20 to 100% by weight of electroactive cathode materials (e.g., as measured after an appropriate amount of solvent has been removed from the cathode active layer and/or after the layer has been appropriately cured). In one embodiment, the amount of electroactive sulfur-containing material in the cathode active layer is in the range of 5-30% by weight of the cathode active layer. In another embodiment, the amount of electroactive sulfur-containing material in the cathode active layer is in the range of 20% to 90% by weight of the cathode active layer. 
     Additional materials suitable for use in the cathode, and suitable methods for making the cathodes, are described, for example, in U.S. Pat. No. 5,919,587, filed May 21, 1997, entitled “Novel Composite Cathodes, Electrochemical Cells Comprising Novel Composite Cathodes, and Processes for Fabricating Same,” and U.S. Patent Publication No. 2010/0035128 to Scordilis-Kelley et al. filed on Aug. 4, 2009, entitled “Application of Force in Electrochemical Cells,” each of which is incorporated herein by reference in its entirety for all purposes. 
     A variety of electrolytes can be used in association with the electrochemical cells described herein. In some embodiments, the electrolyte may comprise a non-solid electrolyte, which may or may not be incorporated with a porous separator. As used herein, the term “non-solid” is used to refer to materials that are unable to withstand a static shear stress, and when a shear stress is applied, the non-solid experiences a continuing and permanent distortion. Examples of non-solids include, for example, liquids, deformable gels, and the like. 
     The electrolytes used in electrochemical cells described herein can function as a medium for the storage and transport of ions, and in the special case of solid electrolytes and gel electrolytes, these materials may additionally function as a separator between the anode and the cathode. Any liquid, solid, or gel material capable of storing and transporting ions may be used, so long as the material facilitates the transport of ions (e.g., lithium ions) between the anode and the cathode. Exemplary materials suitable for use in the electrolyte are described, for example, in U.S. Patent Publication No. 2010/0035128 to Scordilis-Kelley et al. filed on Aug. 4, 2009, entitled “Application of Force in Electrochemical Cells,” which is incorporated herein by reference in its entirety for all purposes. 
     U.S. application Ser. No. 16/527,903, filed Jul. 31, 2019, and entitled “Multiplexed Charge Discharge Battery Management System” is incorporated herein by reference in its entirety for all purposes. 
     The following documents are incorporated herein by reference in their entireties for all purposes: U.S. Pat. No. 7,247,408, filed May 23, 2001, entitled “Lithium Anodes for Electrochemical Cells”; U.S. Pat. No. 5,648,187, filed Mar. 19, 1996, entitled “Stabilized Anode for Lithium-Polymer Batteries”; U.S. Pat. No. 5,961,672, filed Jul. 7, 1997, entitled “Stabilized Anode for Lithium-Polymer Batteries”; U.S. Pat. No. 5,919,587, filed May 21, 1997, entitled “Novel Composite Cathodes, Electrochemical Cells Comprising Novel Composite Cathodes, and Processes for Fabricating Same”; U.S. patent application Ser. No. 11/400,781, filed Apr. 6, 2006, published as U. S. Pub. No. 2007-0221265, and entitled “Rechargeable Lithium/Water, Lithium/Air Batteries”; International Patent Apl. Serial No.: PCT/US2008/009158, filed Jul. 29, 2008, published as International Pub. No. WO/2009017726, and entitled “Swelling Inhibition in Lithium Batteries”; U.S. patent application Ser. No. 12/312,764, filed May 26, 2009, published as U.S. Pub. No. 2010-0129699, and entitled “Separation of Electrolytes”; International Patent Apl. Serial No.: PCT/US2008/012042, filed Oct. 23, 2008, published as International Pub. No. WO/2009054987, and entitled “Primer for Battery Electrode”; U.S. patent application Ser. No. 12/069,335, filed Feb. 8, 2008, published as U.S. Pub. No. 2009-0200986, and entitled “Protective Circuit for Energy-Storage Device”; U.S. patent application Ser. No. 11/400,025, filed Apr. 6, 2006, published as U.S. Pub. No. 2007-0224502, and entitled “Electrode Protection in both Aqueous and Non-Aqueous Electrochemical Cells, including Rechargeable Lithium Batteries”; U.S. patent application Ser. No. 11/821,576, filed Jun. 22, 2007, published as U.S. Pub. No. 2008/0318128, and entitled “Lithium Alloy/Sulfur Batteries”; patent application Ser. No. 11/111,262, filed Apr. 20, 2005, published as U.S. Pub. No. 2006-0238203, and entitled “Lithium Sulfur Rechargeable Battery Fuel Gauge Systems and Methods”; U.S. patent application Ser. No. 11/728,197, filed Mar. 23, 2007, published as U.S. Pub. No. 2008-0187663, and entitled “Co-Flash Evaporation of Polymerizable Monomers and Non-Polymerizable Carrier Solvent/Salt Mixtures/Solutions”; International Patent Apl. Serial No.: PCT/US2008/010894, filed Sep. 19, 2008, published as International Pub. No. WO/2009042071, and entitled “Electrolyte Additives for Lithium Batteries and Related Methods”; International Patent Apl. Serial No.: PCT/US2009/000090, filed Jan. 8, 2009, published as International Pub. No. WO/2009/089018, and entitled “Porous Electrodes and Associated Methods”; U.S. patent application Ser. No. 12/535,328, filed Aug. 4, 2009, published as U.S. Pub. No. 2010/0035128, and entitled “Application of Force In Electrochemical Cells”; U.S. patent application Ser. No. 12/727,862, filed Mar. 19, 2010, entitled “Cathode for Lithium Battery”; U.S. patent application Ser. No. 12/471,095, filed May 22, 2009, entitled “Hermetic Sample Holder and Method for Performing Microanalysis Under Controlled Atmosphere Environment”; U.S. patent application Ser. No. 12/862,513, filed on Aug. 24, 2010, entitled “Release System for Electrochemical cells (which claims priority to Provisional Patent Apl. Ser. No. 61/236,322, filed Aug. 24, 2009, entitled “Release System for Electrochemical Cells”); U.S. Provisional Patent Apl. Ser. No. 61/376,554, filed on Aug. 24, 2010, entitled “Electrically Non-Conductive Materials for Electrochemical Cells;” U.S. Provisional patent application Ser. No. 12/862,528, filed on Aug. 24, 2010, entitled “Electrochemical Cell;” U.S. patent application Ser. No. 12/862,563, filed on Aug. 24, 2010, published as U.S. Pub. No. 2011/0070494, entitled “Electrochemical Cells Comprising Porous Structures Comprising Sulfur”; U.S. patent application Ser. No. 12/862,551, filed on Aug. 24, 2010, published as U.S. Pub. No. 2011/0070491, entitled “Electrochemical Cells Comprising Porous Structures Comprising Sulfur”; U.S. patent application Ser. No. 12/862,576, filed on Aug. 24, 2010, published as U.S. Pub. No. 2011/0059361, entitled “Electrochemical Cells Comprising Porous Structures Comprising Sulfur”; U.S. patent application Ser. No. 12/862,581, filed on Aug. 24, 2010, published as U.S. Pub. No. 2011/0076560, entitled “Electrochemical Cells Comprising Porous Structures Comprising Sulfur”; U.S. Patent Apl. Ser. No. 61/385,343, filed on Sep. 22, 2010, entitled “Low Electrolyte Electrochemical Cells”; and U.S. patent application Ser. No. 13/033,419, filed Feb. 23, 2011, entitled “Porous Structures for Energy Storage Devices”. All other patents and patent applications disclosed herein are also incorporated by reference in their entirety for all purposes. 
       FIG.  4 A  depicts a representative high-level process  400 A for controlling a charging rate or current of a cell. The acts of representative process  400 A are described in detail in the paragraphs that follow. 
     In some embodiments, representative process  400 A may include act  430 A, wherein an electrochemical cell (such as electrochemical cell  121 A described above) may be controlled to be, for at least a portion of a charge cycle, charged at a charging rate or current that is lower than a discharging rate or current of at least a portion of a previous discharge cycle, as described herein. 
     In some embodiments, process  400 A may then end or repeat as necessary, such as for more charge/discharge cycles. 
       FIG.  4 B  depicts a representative process  400 B for controlling a charging rate or current of a cell (such as electrochemical cell  121 A described above). The acts of representative process  400 B are described in detail in the paragraphs that follow. 
     In some embodiments, representative process  400 B may include act  410 , wherein characteristic(s) of a cell may be monitored (e.g., by a controller such as  114  and a sensor  116  as described above), as described herein. 
     In some embodiments, representative process  400 B may then optionally proceed to act  420 , wherein at least one threshold may be considered to determine if it has been met, as described herein. For example, the threshold may be a threshold measurement of the monitored characteristic(s), such as a threshold amount (or rate or current) of discharging in the discharge history, a pressure measurement on the cell, and so on. 
     In some embodiments, if the threshold has been met, representative process  400 B may then proceed to act  430 A, wherein the cell may be controlled (e.g., by controller  114 ) to be charged at a charging rate or current lower than a discharging rate or current for a portion of the cell&#39;s discharge cycle. For example, if the cell has had a discharge cycle or history of discharging at 300 mA, the cell may be controlled to charge at 150 mA or less, as described herein. Alternatively, if the threshold has not been met, the characteristic(s) may continue to be monitored. 
     In some embodiments, representative process  400 B may then optionally proceed to act  431 B, wherein an induced discharge of the cell may be caused by the controller. An induced discharge may be caused at various times and for various reasons, as described herein. 
     In some embodiments, representative process  400 B may then optionally proceed to any of acts  432  or  434 . For example, if process  400 B proceeds from act  431 B to act  432 , the cell may be controlled to charge at a charging rate at least 2 times lower than its discharging rate, as described herein. 
     Alternatively or additionally, process  400 B may proceed from act  431 B to act  434 , wherein the cell may be controlled to charge at a charging rate 4 times lower than its discharging rate, as described herein. 
     In some embodiments, process  400 B may then end or repeat as necessary, such as for more charge/discharge cycles. 
     It should be appreciated that any of acts  432  and/or  434  may actually be integral to act  430 A, although they are represented as separate acts in  FIG.  4 B . 
       FIG.  4 C  depicts a representative high-level process  400 C for inducing discharge of a cell. The acts of representative process  400 C are described in detail in the paragraphs that follow. 
     In some embodiments, representative process  400 C may include act  430 C, wherein an induced discharge of a electrochemical cell (such as electrochemical cell  121 A described above) may be caused before and/or after a charging step, as described herein. 
     In some embodiments, process  400 C may then end or repeat as necessary, such as for more charge/discharge cycles. 
       FIG.  4 D  depicts a representative process  400 D for inducing discharge of a cell. The acts of representative process  400 D are described in detail in the paragraphs that follow. 
     In some embodiments, representative process  400 D may optionally include act  410 , wherein characteristic(s) of a cell may be monitored as described herein. 
     In some embodiments, representative process  400 D may then optionally proceed to act  420 , wherein at least one threshold may be considered to determine if it has been met. For example, the threshold may be a threshold measurement of the monitored characteristic(s), such as a threshold amount (or rate or current) of discharging in the discharge history, a pressure measurement on the cell, a thickness or size of the cell, and so on. 
     In some embodiments, if the threshold has been met, representative process  400 D may then proceed to act  430 C, an induced discharge of the cell may be caused by the controller (e.g., by controller  114 ), as described herein. For example, the threshold may be met if a charge/discharge history of the cell shows that the discharge cycle has ended, the discharge cycle and/or a discharging step is still in progress, a charge cycle has ended, or a charge cycle and/or charging step is about to begin, as described herein. Alternatively, if the threshold has not been met, the characteristic(s) may continue to be monitored. 
     In some embodiments, representative process  400 D may then optionally proceed to act  431 D, wherein the cell may be controlled to be, for at least a portion of a charge cycle, charged at a charging rate or current that is lower than a discharging rate or current of at least a portion of a previous discharge cycle, as described herein. 
     In some embodiments, representative process  400 D may then optionally proceed to any of acts  432  or  434 . For example, if process  400 D proceeds from act  431 D to act  432 , the cell may be controlled to charge at a charging rate at least 2 times lower than its discharging rate. 
     Alternatively or additionally, process  400 D may proceed from act  431 D to act  434 , wherein the cell may be controlled to charge at a charging rate 4 times lower than its discharging rate. 
     In some embodiments, process  400 D may then end or repeat as necessary, such as for more charge/discharge cycles. 
     It should be appreciated that any of acts  432  and/or  434  may actually be integral to act  430 C, although they are represented as separate acts in  FIG.  4 D . 
       FIG.  5 A  depicts a representative process  500 A for monitoring cell characteristic(s) and inducing discharge or controlling the charge rate or current of the cell. The acts of representative process  500 A are described in detail in the paragraphs that follow. 
     In some embodiments, representative process  500 A may include act  510 , wherein characteristic(s) of a cell may be monitored (e.g., by a controller such as  114  and a sensor  116  as described above), as described herein. 
     In some embodiments, process  500 A may then proceed from act  510  to act  530 , wherein, based on the monitoring in act  510 , an induced discharge of the cell and/or controlled charging of the cell may be caused by the controller, as described herein. 
     In some embodiments, process  500 A may then end or repeat as necessary. 
       FIG.  5 B  depicts a representative process  500 B for monitoring cell characteristic(s) and inducing discharge or controlling the charge rate or current of the cell. The acts of representative process  500 B are described in detail in the paragraphs that follow. 
     In some embodiments, representative process  500 B may include act  510 , wherein characteristic(s) of a cell may be monitored (e.g., by a controller such as  114  and a sensor  116  as described above). 
     In some embodiments, representative process  500 B may then optionally proceed to act  520 , wherein at least one threshold may be considered to determine if it has been met, as described herein. For example, the threshold may be a threshold measurement of the monitored characteristic(s), such as a threshold amount (or rate or current) of discharging in the discharge history, a pressure measurement on the cell, a thickness or size of the cell, and so on. 
     In some embodiments, if the threshold has been met, representative process  500 B may then proceed to act  530 , wherein an induced discharge of the cell may be caused by the controller (e.g., by controller  114 ), as described herein. For example, the threshold may be met if a charge/discharge history of the cell shows that the discharge cycle has ended, the discharge cycle and/or a discharging step is still in progress, a charge cycle has ended, or a charge cycle and/or charging step is about to begin, as described herein. Alternatively, if the threshold has not been met, the characteristic(s) may continue to be monitored. 
     In some embodiments, representative process  500 B may then optionally proceed to any of acts  532  or  534 . For example, if process  500 B proceeds from act  530  to act  532 , the cell may be controlled to charge at a charging rate at least 2 times lower than its discharging rate. 
     Alternatively or additionally, process  500 B may proceed from act  530  to act  534 , wherein the cell may be controlled to charge at a charging rate 4 times lower than its discharging rate. 
     In some embodiments, process  500 B may then end or repeat as necessary. 
     It should be appreciated that any of acts  532  and/or  534  may actually be integral to act  530 , although they are represented as separate acts in  FIG.  5 B . 
     The inventors have recognized and appreciated that some embodiments described above may produce results showing various improvements over conventional techniques when implemented. 
     In the following Examples 1-5 and Tables 1-4, cells are cycled under pressure of 10-12 kg/cm 2 . 
     Example 1: Example 1 shows that cycle life was short when cells were cycled at the same charge and discharge rates (currents or times) in the wide range of rates. Cells with NCM111 cathode, 15 μm vapor-deposited lithium anode, and an electrolyte were cycled under 10 kg/cm 2  pressure. The electrolyte included a 1 molar solution of lithium hexafluorophosphate in a 2:1 weight ratio of ethylene carbonate to dimethyl carbonate. Total cell active electrodes area was 99.4 cm 2  and cell capacity was 200 mAh. Cell were charged to 4.35 V and discharged to 3.2 V at currents in Table 1 below. Charge and discharge current were equal. All cells showed short cycle life of 38-56 cycles for the range of charge discharge currents from 40 to 200 mA (5 times different currents). 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Discharge 
                 Charge 
                 Cycle Life 
               
               
                 mA 
                 mA 
                 to 110 mAh 
               
               
                   
               
             
            
               
                  40 
                  40 
                 56 
               
               
                  67 
                  67 
                 44 
               
               
                 150 
                 150 
                 38 
               
               
                 200 
                 200 
                 38 
               
               
                   
               
            
           
         
       
     
     Example 2: Example 2 shows that cycle life improved when discharge current was fixed but charge currents were substantially lower. Higher discharge/charge currents ratio led to longer cycle life. 
     Cells similar to Example 1 but with NCM622 cathode. Cell capacity was 330 mAh. Cells were charged to 4.35 V and discharged to 3.2 V at currents in Table 2 below. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Discharge 
                   
                 Discharge/Charge 
                 Cycle Life to 250 
               
               
                 mA 
                 Charge mA 
                 Current Ratio 
                 mAh 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 300 
                 100 
                 3 
                 96 
               
               
                 300 
                 50 
                 6 
                 140 
               
               
                 300 
                 40 
                 7.5 
                 146 
               
               
                 300 
                 30 
                 10 
                 159 
               
               
                   
               
            
           
         
       
     
     Cycle life in Table 2 increased with higher discharge/charge current ratio. The biggest gain was for 3-6 ratio with diminishing additional gain at higher ratio values and respectively longer charge. 
     Example 3: Example 3 shows that cycle life improved when charge current was fixed but discharge current was substantially higher. Higher discharge/charge currents ratio led to longer cycle life. 
     Cells are similar to Example 2 but with electrolyte LiIon1401. Cell capacity was 330 mAh. Cells were charged to 4.35 V and discharged to 3.2 V at currents in Table 3 below. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 Discharge 
                   
                 Discharge/Charge 
                 Cycle Life to 250 
               
               
                 mA 
                 Charge mA 
                 Current Ratio 
                 mAh 
               
               
                   
               
             
            
               
                  75 
                 75 
                 1 
                  54 
               
               
                 300 
                 75 
                 4 
                 334 
               
               
                   
               
            
           
         
       
     
     Change of discharge/charge currents ratio from 1 to 4 at fixed charge current lead to dramatic, 6-fold cycle life improvement. 
     Example 4: Example 4 shows that cycle life improved when charge current was fixed and discharge current was substantially higher but was not necessarily continuous. The cell was discharged at conditions when discharge was periodically suspended for a certain period of time and resumed again. 
     Cells are similar to Example 3. Cell capacity was 330 mAh. Cells were charged to 4.35 V and discharged to 3.2 V at currents in Table 3 below. Charge and discharge currents of 100 mA were continuous. 
     Discharge process at 400 mA was not continuous. Discharge at 400 mA lasted for 10 s, then was suspended for 30 s and resumed again. This process was periodical. Cycle life data obtained at these two processes are in Table 4. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 Discharge 
                   
                 Discharge/Charge 
                 Cycle Life to 250 
               
               
                 mA 
                 Charge mA 
                 Current Ratio 
                 mAh 
               
               
                   
               
             
            
               
                 100 
                 100 
                 1 
                  51 
               
               
                 400 
                 100 
                 4 
                 277 
               
               
                   
               
            
           
         
       
     
     Example 5: Example 5 shows that cycle life improved only if higher discharge/charge current ratio is applicable for substantial part of discharge time or capacity. If higher current discharge conditions are just a small portion of entire discharge time the cycle life gain is not substantial. 
     Cells are similar to Example 4 but with NCM721 cathode. Cell capacity was 360 mAh. Cells were charged to 4.4 V and discharged to 3.2 V. 
     The first portion of the cells experienced equal 100 mA charge and discharge currents and delivered cycle life of 43 cycle at 250 mAh cutoff. 
     The second portion of the cells was charged at constant current of 100 mA and discharged at two steps: 100 mA to 95% of capacity and then at 400 mA to get remaining 5% of capacity. 
     The cycle life of these cells was 52 cycles. This was 9 cycles or ˜21% of cycle life gain based on higher discharge/charge current ratio of 4 being applied for 5% of total discharge capacity. The inventors have recognized and appreciated that better cycle life can be expected with 5% of discharge capacity obtained at higher discharge/charge current ratio, such as where an average discharging rate or current during the previous discharge cycle is equal to or less than an average charging rate or current during the charge cycle, and an average discharging rate or current during discharge of at least 5% of the discharge capacity of the cell during the previous discharge cycle is at least 2 times higher or is 4 times higher than the average charging rate or current during the charge cycle. 
       FIG.  6 A  depicts a representative high-level process  600 A for discharging sets of cells of a battery. The acts of representative process  600 A are described in detail in the paragraphs that follow. 
     In some embodiments, representative process  600 A may include act  630 A, wherein sets of cells in a battery may be selectively discharged based on at least one criterion using a multiplexing switch apparatus (such as multiplexing switch apparatus  112  described above). Additionally, the multiplexing switch apparatus may be connected to two or more sets (e.g.,  121 ,  122 ,  123 , and/or  124 ) of cells (e.g.,  121 A-C) of at least one battery (e.g.,  120 - 150 ). Each set of cells may comprise one or more cells. 
     In some embodiments, process  600 A may then end or repeat as necessary. 
       FIG.  6 B  depicts a representative high-level process  600 B for discharging sets of cells of a battery. The acts of representative process  600 B are described in detail in the paragraphs that follow. 
     In some embodiments, representative process  600 B optionally may begin at act  610 , wherein the multiplexing switch apparatus may be used to connect the sets of cells to a load in a topology employed by the load. The batteries (e.g.,  120 - 150 ) may include sets (e.g.,  121 ,  122 ,  123 , and/or  124 ) of the cells (e.g.,  121 A-C), and each set of cells may comprise one or more cells. For example, the multiplexing switch apparatus may connect the cells to the load in series, parallel, serial/parallel, or any other suitable topology required to meet the voltage and current requirements of the load or the desires of the given application or user. 
     In some embodiments, representative process  600 B may then optionally proceed to act  620 , wherein at least one criterion, and/or some parameter of a criterion, may be measured or otherwise monitored in relation to the cells of the battery or batteries, which may already be discharging or have discharged at least one cell or set of cells, to determine whether the criterion has been met. 
     For example, a sensor (such as  116  in  FIGS.  1 A and  1 F ) may measure the delivered discharge capacity at a connection between a load and a set of cells currently connected to the load, or it may measure the current of the set of cells. Alternatively or additionally, the sensor may measure any of the following: a duration of the connection (which may be at least 0.01 seconds in some embodiments), a capacity accumulated over several connections between the load and the set of cells, a voltage of the set of cells and/or of at least one other set of cells, a cutoff discharge voltage of the set of cells, a power of the set of cells, an energy of the set of cells, a number of charge or discharge cycles of the set of cells, an impedance of the set of cells, a rate of voltage fading of the set of cells during the connection, a temperature of the set of cells, and a pressure of the set of cells. 
     In some embodiments, the criterion may include a sequence in which to discharge the cells or sets of cells. Alternatively or additionally, the criterion may be the value of a function that has any of the above as parameters. According to some embodiments, the criterion does not include a number of prior discharge cycles of the sets of cells. 
     In some embodiments, if the criterion has been met, representative process  600 B may then proceed to act  630 , wherein the next set of cells in the battery may be selectively discharged based on the criterion using a multiplexing switch apparatus (such as multiplexing switch apparatus  112  described above). For example, if the current discharging set of cells has met whatever criterion or criteria is required, that set of cells may be disconnected and the next set of cells may be connected (where the next set may be determined by a criterion or criteria which may be the same or different from those discussed above) as described herein. Alternatively, if the criterion has not been met, it may continue to be monitored. According to some embodiments, the connection between a single cell and the load may be at least 0.01 seconds in duration. The inventors have recognized and appreciated that a shorter connection duration than 0.01 seconds may surprisingly produce more noise than at 0.01 seconds and may not allow the electrochemistry of the cell to accomplish anything non-negligible. 
     In some embodiments, representative process  600 B may then optionally proceed to act  631 , wherein the multiplexing switch apparatus may be used to isolate a single set of cells for discharging while other sets of cells are not discharging. For example, when a controller (e.g.,  114  of  FIGS.  1 A and  1 F ) determines that cell  121 B should be discharged, it may cause the multiplexing switch apparatus to isolate cell  121 B for discharging while cells  121 A and  121 C are not discharging. 
     In some embodiments, representative process  600 B may then optionally proceed to any of acts  632 ,  634 ,  636 , and/or  638 . For example, if process  600 B proceeds from act  631  to act  632 , the multiplexing switch apparatus may be used to selectively discharge the sets of cells at a first rate at least 2 times higher than a second rate of charging the sets of cells. 
     Alternatively or additionally, process  600 B may proceed from act  631  to act  634 , wherein the multiplexing switch apparatus may be used to selectively discharge the sets of cells at a first rate at least 4 times higher than a second rate of charging the sets of cells. 
     Alternatively or additionally, process  600 B may proceed from act  631  to act  636 , wherein discharge of the sets of cells may be temporally overlapping, such as by using the multiplexing switch apparatus as discussed above. 
     Alternatively or additionally, process  600 B may proceed from act  631  to act  638 , wherein power may continue to be provided from the sets of cells during switching between different sets. 
     It should be appreciated that any of acts  631 ,  632 ,  634 ,  636 , and/or  638  may actually be integral to act  630 , although they are represented as separate acts in  FIG.  6 B . 
     In some embodiments, representative process  600 B may then optionally proceed to act  640 , wherein the multiplexing switch apparatus may be used to charge the sets of cells in parallel, such as is described above. 
     According to some embodiments, any number of sets of cells, including all the sets of cells in the battery, battery pack, or system, may be discharged simultaneously. For example, with a battery having 4 cells, all 4 cells (or only 2 or 3) could be discharged at the same time, producing whatever discharge current is desirable for the load or application and possible for the cells. Additionally, in some embodiments, the number of cells or sets discharged or charged is selected based on the at least one criterion, such as discharge current for discharging. In certain embodiments, the sequence in which the number of cells or sets of cells is discharged or charged is selected based on the at least one criterion, such as discharge current for discharging. In some embodiments, both the number of cells or sets discharged or charged and the sequence of doing so is selected based on the at least one criterion, such as discharge current for discharging. 
     In some embodiments, process  600 B may then end or repeat as necessary. For example, process  600 B may repeat through any suitable number of cycles. According to some embodiments, for each cycle or some cycles, each cell may be discharged once before any cell is discharged twice. 
       FIG.  6 C  depicts a representative high-level process  600 C for controlling a battery pack. The acts of representative process  600 C are described in detail in the paragraphs that follow. 
     In some embodiments, representative process  600 C may include act  630 C, wherein switches may be controlled (e.g., by a controller such as  114  described above) to discharge sets (e.g.,  121 ,  122 ,  123 , and/or  124 ) of cells (e.g.,  121 A-C) in the battery pack (e.g.,  210 ) sequentially using an integrated switching control system. Additionally, the multiplexing switch apparatus may be connected to two or more sets of cells of the battery or batteries. Each set of cells may comprise one or more cells. 
     In some embodiments, process  600 C may then end or repeat as necessary. 
       FIG.  6 D  depicts a representative high-level process  600 D for controlling a battery pack. The acts of representative process  600 D are described in detail in the paragraphs that follow. 
     In some embodiments, representative process  600 D may include act  630 D, wherein switches may be controlled (e.g., by a controller such as  114  described above) to discharge sets (e.g.,  121 ,  122 ,  123 , and/or  124 ) of cells (e.g.,  121 A-C) in the battery pack (e.g.,  210 ) based on a criterion using an integrated switching control system. Additionally, the multiplexing switch apparatus may be connected to two or more sets of cells of the battery or batteries. Each set of cells may comprise one or more cells. In some embodiments, the criterion may include any of the following: a duration of a connection between a load and a set of cells currently connected to the load, a delivered discharge capacity at the connection, and a value of a function having one or more parameters. 
     In some embodiments, process  600 D may then end or repeat as necessary. 
     The inventors have recognized and appreciated that some embodiments described above may produce results showing various improvements over conventional techniques when implemented. For example, in one implementation, cells were made of NCMA622 cathode (BASF) with 50 μm Li foil and 25 μm Celgard 2325 separator filled with F9 (BASF) electrolyte containing 1% by weight of lithium bis(oxalato)borate (LiBOB), with an active electrode area of 99.41 cm 2 . The cells were assembled into 13 batteries containing 4 cells each. The batteries were subjected to 13 electrical charge-discharge cycling tests performed using some embodiments at conditions summarized in Table 5 and Table 6 below. The cells in the batteries were kept at pressure of 12 kg/cm 2  and temperature of 18° C. during cycling tests. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Battery test data for 4 cells simultaneously discharged with  
               
               
                 even current distribution. 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 Battery 
                 Battery  
                   
                   
               
               
                   
                   
                   
                 Cycle  
                 5 th   
                   
                   
               
               
                   
                 Battery 
                 Battery 
                 Life 
                 Cycle 
                 Cell 
                 Cell  
               
               
                   
                 Discharge 
                 Charge 
                 to 800 
                 Discharge 
                 Discharge 
                 Charge 
               
               
                 Test 
                 Current 
                 Current 
                 mAh 
                 Capacity 
                 Current 
                 Current 
               
               
                 # 
                 mA 
                 mA 
                 Cutoff 
                 mAh 
                 mA 
                 mA 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 1 
                 800 
                 800 
                 29 
                 1344 
                 200 
                 200 
               
               
                 2 
                 400 
                 400 
                 52 
                 1380 
                 100 
                 100 
               
               
                 3 
                 300 
                 300 
                 53 
                 1412 
                 75 
                 75 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Battery test data for 4 cells sequentially discharged at various discharge pulse durations. 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 Battery 
                   
                   
                   
                   
                   
                   
               
               
                   
                   
                   
                 Cycle 
                 Battery 
                 Cell 
                 Cell 
                   
                   
                 Level of 
               
               
                   
                 Battery 
                 Battery 
                 Life to 
                 5 th  Cycle 
                 Discharge 
                 Discharge 
                 Cell No 
                 Cell 
                 Cell 
               
               
                   
                 Discharge 
                 Charge 
                 800  
                 Discharge 
                 Pulse 
                 Pulse 
                 Current 
                 Charge 
                 Discharge 
               
               
                 Test 
                 Current 
                 Current 
                 mAh 
                 Capacity 
                 Current 
                 Duration 
                 Duration 
                 Current 
                 at Single 
               
               
                 # 
                 mA 
                 mA 
                 Cutoff 
                 mAh 
                 mA 
                 s 
                 s 
                 mA 
                 Pulse 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                  4 
                 800 
                 800 
                 94 
                 1064 
                 800 
                 1197 
                 0 
                 200 
                 Full 
               
               
                  5 
                 800 
                 800 
                 131 
                 1208 
                 800 
                 10 
                 30 
                 200 
                 Partial 
               
               
                  6 
                 800 
                 800 
                 125 
                 1252 
                 800 
                 1 
                 3 
                 200 
                 Partial 
               
               
                  7 
                 800 
                 800 
                 46 
                 1260 
                 800 
                 0.1 
                 0.3 
                 200 
                 Partial 
               
               
                  8 
                 400 
                 400 
                 263 
                 1260 
                 400 
                 2835 
                 0 
                 100 
                 Full 
               
               
                  9 
                 400 
                 400 
                 283 
                 1284 
                 400 
                 10 
                 30 
                 100 
                 Partial 
               
               
                 10 
                 400 
                 400 
                 217 
                 1352 
                 400 
                 1 
                 3 
                 100 
                 Partial 
               
               
                 11 
                 400 
                 400 
                 59 
                 1368 
                 400 
                 0.1 
                 0.3 
                 100 
                 Partial 
               
               
                 12 
                 300 
                 300 
                 334 
                 1304 
                 300 
                 3912 
                 0 
                 75 
                 Full 
               
               
                 13 
                 300 
                 300 
                 298 
                 1412 
                 300 
                 10 
                 30 
                 75 
                 Partial 
               
               
                   
               
            
           
         
       
     
     Table 5 (Tests #1-#3) represents comparative examples (as performed by conventional techniques) and summarizes test results when batteries were charged and discharged at constant currents with cells connected in parallel and with charge and discharge currents distributed evenly among 4 cells. Charge cutoff voltage was 4.35 V and discharge cutoff voltage was 3.2 V. Charge-discharge cycling stopped when battery capacity reached 800 mAh. 
     Table 6 (Tests #4-#13) summarizes test results when batteries were charged to 4.35 V at constant currents with cells connected in parallel and with charge discharge currents distributed evenly among 4 cells. Discharge of these batteries was performed in a way that the battery as a whole experienced constant discharge current. However, individual cells were connected to and disconnected from the load sequentially, providing discharge current pulse only for one of four cells at a time. At the end of this pulse, the next cell was connected and the previous one was disconnected. Cells experienced discharge pulses in sequences (e.g., Cell #1, 2, 3, 4, 1, 2, 3, 4, etc.) during a certain pulse time or until discharge voltage reached 3.2 V. Tests #4, #8, and #12 provided full cell discharge at single pulse. Other tests provided partial cell discharge at single pulse with durations of 0.1, 1, and 10 s. Charge-discharge cycling stopped when battery capacity reached 800 mAh. 
       FIG.  7 A , corresponding to Test #13, shows the battery voltage profile at the beginning of the 10 second pulse discharge for the first 240 seconds, and  FIG.  7 B  shows the full discharge profile to a voltage of 3.2 V. In  FIG.  7 A , the cell numbers affected by the 10 second 300 mA pulses at repeated sequences are shown for the first 80 seconds. 
     Referring back to Table 5 and Table 6, the inventors have recognized and appreciated that applying whole battery discharge current to the portion of the battery cells in sequence (Table 6) has led to surprising and dramatic cycle life improvement compared with homogeneous current distribution among all battery cells (Table 5), as has been done in conventional techniques. This cycle life improvement may be up to six-fold, and the inventors recognized it may be a function of discharge pulse duration as well as charge-discharge rate.  FIG.  7 C , which illustrates battery cycle life as a function of pulse duration at two charge-discharge rates (corresponding to Tests #4-#11), shows that cycle life may be especially improved with pulse time longer than 0.1 seconds and pulse duration around 10 seconds. The inventors have recognized and appreciated that improvements to battery cycle life described herein are even available using some embodiments at partial discharge, as  FIG.  7 C  shows and as would not have been expected based on experience with conventional techniques. Additionally, the full capacity of all cells, even when far from uniform, can be utilized with some embodiments. 
     It should be appreciated that, in some embodiments, the methods described above with reference to  FIGS.  4 A- 6    may vary, in any of numerous ways. For example, in some embodiments, the steps of the methods described above may be performed in a different sequence than that which is described, a method may involve additional steps not described above, and/or a method may not involve all of the steps described above. 
     It should further be appreciated from the foregoing description that some aspects may be implemented using a computing device.  FIG.  8    depicts a general purpose computing device in system  800 , in the form of a computer  810 , which may be used to implement certain aspects, such as any of the controllers described above (e.g.,  114 ). 
     In computer  810 , components include, but are not limited to, a processing unit  820 , a system memory  830 , and a system bus  821  that couples various system components including the system memory to the processing unit  820 . The system bus  821  may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. By way of example, and not limitation, such architectures include Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnect (PCI) bus also known as Mezzanine bus. 
     Computer  810  typically includes a variety of computer readable media. Computer readable media can be any available media that can be accessed by computer  810  and includes both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, computer readable media may comprise computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other one or more media that may be used to store the desired information and may be accessed by computer  810 . Communication media typically embody computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media include wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. Combinations of the any of the above should also be included within the scope of computer readable media. 
     The system memory  830  includes computer storage media in the form of volatile and/or nonvolatile memory such as read only memory (ROM)  831  and random access memory (RAM)  832 . A basic input/output system  833  (BIOS), containing the basic routines that help to transfer information between elements within computer  810 , such as during start-up, is typically stored in ROM  831 . RAM  832  typically contains data and/or program modules that are immediately accessible to and/or presently being operated on by processing unit  820 . By way of example, and not limitation,  FIG.  8    illustrates operating system  834 , application programs  835 , other program modules  839  and program data  837 . 
     The computer  810  may also include other removable/non-removable, volatile/nonvolatile computer storage media. By way of example only,  FIG.  8    illustrates a hard disk drive  841  that reads from or writes to non-removable, nonvolatile magnetic media, a magnetic disk drive  851  that reads from or writes to a removable, nonvolatile magnetic disk  852 , and an optical disk drive  855  that reads from or writes to a removable, nonvolatile optical disk  859  such as a CD ROM or other optical media. Other removable/non-removable, volatile/nonvolatile computer storage media that can be used in the exemplary computing system include, but are not limited to, magnetic tape cassettes, flash memory cards, digital versatile disks, digital video tape, solid state RAM, solid state ROM, and the like. The hard disk drive  841  is typically connected to the system bus  821  through an non-removable memory interface such as interface  840 , and magnetic disk drive  851  and optical disk drive  855  are typically connected to the system bus  821  by a removable memory interface, such as interface  850 . 
     The drives and their associated computer storage media discussed above and illustrated in  FIG.  8   , provide storage of computer readable instructions, data structures, program modules and other data for the computer  810 . In  FIG.  8   , for example, hard disk drive  841  is illustrated as storing operating system  844 , application programs  845 , other program modules  849 , and program data  847 . Note that these components can either be the same as or different from operating system  834 , application programs  835 , other program modules  539 , and program data  837 . Operating system  844 , application programs  845 , other program modules  849 , and program data  847  are given different numbers here to illustrate that, at a minimum, they are different copies. A user may enter commands and information into the computer  810  through input devices such as a keyboard  892  and pointing device  891 , commonly referred to as a mouse, trackball or touch pad. Other input devices (not shown) may include a microphone, joystick, game pad, satellite dish, scanner, or the like. These and other input devices are often connected to the processing unit  820  through a user input interface  590  that is coupled to the system bus, but may be connected by other interface and bus structures, such as a parallel port, game port or a universal serial bus (USB). A monitor  891  or other type of display device is also connected to the system bus  821  via an interface, such as a video interface  890 . In addition to the monitor, computers may also include other peripheral output devices such as speakers  897  and printer  899 , which may be connected through a output peripheral interface  895 . 
     The computer  810  may operate in a networked environment using logical connections to one or more remote computers, such as a remote computer  880 . The remote computer  880  may be a personal computer, a server, a router, a network PC, a peer device or other common network node, and typically includes many or all of the elements described above relative to the computer  810 , although only a memory storage device  881  has been illustrated in  FIG.  8   . The logical connections depicted in  FIG.  8    include a local area network (LAN)  871  and a wide area network (WAN)  873 , but may also include other networks. Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets and the Internet. 
     When used in a LAN networking environment, the computer  810  is connected to the LAN  871  through a network interface or adapter  870 . When used in a WAN networking environment, the computer  810  typically includes a modem  872  or other means for establishing communications over the WAN  873 , such as the Internet. The modem  872 , which may be internal or external, may be connected to the system bus  821  via the user input interface  890 , or other appropriate mechanism. In a networked environment, program modules depicted relative to the computer  810 , or portions thereof, may be stored in the remote memory storage device. By way of example, and not limitation,  FIG.  8    illustrates remote application programs  885  as residing on memory device  881 . It will be appreciated that the network connections shown are exemplary and other means of establishing a communications link between the computers may be used. 
     Embodiments may be embodied as a computer readable storage medium (or multiple computer readable media) (e.g., a computer memory, one or more floppy discs, compact discs (CD), optical discs, digital video disks (DVD), magnetic tapes, flash memories, circuit configurations in Field Programmable Gate Arrays or other semiconductor devices, or other tangible computer storage medium) encoded with one or more programs that, when executed on one or more computers or other processors, perform methods that implement the various embodiments discussed above. As is apparent from the foregoing examples, a computer readable storage medium may retain information for a sufficient time to provide computer executable instructions in a non-transitory form. Such a computer readable storage medium or media can be transportable, such that the program or programs stored thereon can be loaded onto one or more different computers or other processors to implement various aspects of the present invention as discussed above. As used herein, the term “computer-readable storage medium” encompasses only a tangible machine, mechanism or device from which a computer may read information. Alternatively or additionally, some embodiments may be embodied as a computer readable medium other than a computer-readable storage medium. Examples of computer readable media that are not computer readable storage media include transitory media, like propagating signals. 
     While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the functions and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings of the present invention is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention may include each individual feature, system, article, material, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, and/or methods, if such features, systems, articles, materials, and/or methods are not mutually inconsistent, is included within the scope of the present invention. 
     The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” 
     The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified unless clearly indicated to the contrary. Thus, as a non-limiting example, a reference to “A and/or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc. 
     As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law. 
     As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc. 
     Some embodiments may be embodied as a method, of which various examples have been described. The acts performed as part of the methods may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include different (e.g., more or less) acts than those that are described, and/or that may involve performing some acts simultaneously, even though the acts are shown as being performed sequentially in the embodiments specifically described above. 
     Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements. 
     In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.