PATENT DOCUMENT

Publication Number: US-11189834-B1
Application Number: US-201816038865-A
Country: US
Kind Code: B1

Title: Multiple electrolyte battery cells

Abstract:
Energy storage devices, battery cells, and batteries of the present technology may include a first current collector and a second current collector. Exemplary battery cells may also include a first region defined between the first current collector and the second current collector. The first region may include electrode materials. The battery cells may also include a second region defined between the first current collector and the second current collector. The second region may be fluidly isolated from the first region. The second region may include an electrolyte.

Claims:
What is claimed is: 
     
       1. A battery cell comprising:
 a first current collector; 
 a second current collector; 
 a first region defined between the first current collector and the second current collector, wherein the first region contains electrode materials; 
 a second region defined between the first current collector and the second current collector, wherein the second region is fluidly isolated from the first region, wherein the second region includes an electrolyte, and wherein the electrode materials comprise a cathode active material and an anode active material contained within and limited to the first region. 
 
     
     
       2. The battery cell of  claim 1 , further comprising a separator extending through both the first region and the second region. 
     
     
       3. The battery cell of  claim 1 , further comprising a seal at least partially defining the first region and the second region. 
     
     
       4. The battery cell of  claim 3 , wherein the second region is positioned laterally external to the first region, and wherein the seal defines an exterior of the first region and an interior of the second region. 
     
     
       5. The battery cell of  claim 3 , wherein the seal defines sidewalls of the second region. 
     
     
       6. The battery cell of  claim 5 , wherein, with the first current collector and the second current collector, the seal defines a cavity within the second region. 
     
     
       7. The battery cell of  claim 6 , wherein the seal defines a plurality of separate cavities fluidly isolated from one another and located external to the first region. 
     
     
       8. The battery cell of  claim 1 , wherein the first region includes a first electrolyte, and wherein the second region includes a second electrolyte different from the first electrolyte. 
     
     
       9. The battery cell of  claim 8 , wherein the second electrolyte is configured to remain passive at operating voltages below or about 4.0 V. 
     
     
       10. The battery cell of  claim 9 , wherein the second electrolyte is configured to be electrically activated at operating voltages above or about 4.0 V. 
     
     
       11. The battery cell of  claim 10 , wherein the second region defines a plurality of separate cavities fluidly isolated from one another, wherein a first fluid cavity of the plurality of fluid cavities contains an electrolyte configured to remain passive at operating voltages below or about 4.0 V, and wherein a second fluid cavity of the plurality of fluid cavities contains an electrolyte configured to remain passive at operating voltages below or about 4.3 V. 
     
     
       12. The battery cell of  claim 1 , wherein the first current collector and the second current collector electrically couple the first region and the second region. 
     
     
       13. A battery cell comprising:
 a first current collector; 
 a second current collector; 
 a separator extending between the first current collector and the second current collector, wherein the separator faces the first current collector along a first surface of the separator, and wherein the separator faces the second current collector along a second surface of the separator opposite the first surface of the separator; 
 a first region defined between the first current collector and the second current collector, wherein the first region contains cathode and anode electrode active materials; 
 a second region defined between the first current collector and the second current collector, wherein the second region is fluidly isolated from the first region, wherein the second region extends laterally outward of the first region along the first surface of the separator, and wherein the second region includes an electrolyte. 
 
     
     
       14. The battery cell of  claim 13 , wherein the electrolyte in the second region is a second electrolyte, wherein the first region comprises a different electrolyte from the second region, and wherein the second electrolyte is configured to remain passive at operating voltages below or about 4.0 V. 
     
     
       15. The battery cell of  claim 13 , further comprising a seal at least partially defining the first region and the second region along each of the first surface and the second surface of the separator. 
     
     
       16. The battery cell of  claim 15 , wherein the second region is positioned laterally external to the first region, and wherein the seal defines an exterior of the first region and an interior of the second region. 
     
     
       17. The battery cell of  claim 15 , wherein the seal defines sidewalls of the second region. 
     
     
       18. The battery cell of  claim 17 , wherein, with the first current collector and the second current collector, the seal defines a cavity within the second region. 
     
     
       19. The battery cell of  claim 18 , wherein the seal defines a plurality of separate fluid cavities fluidly isolated from one another and located external to the first region. 
     
     
       20. The battery cell of  claim 19 , wherein a first fluid cavity of the plurality of fluid cavities contains an electrolyte configured to remain passive at operating voltages below or about 4.0 V, and wherein a second fluid cavity of the plurality of fluid cavities contains an electrolyte configured to remain passive at operating voltages below or about 4.3 V.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Application Ser. No. 62/543,229 filed Aug. 9, 2017, the entire disclosure of which is hereby incorporated by reference in its entirety for all purposes. 
    
    
     TECHNICAL FIELD 
     The present technology relates to batteries and battery components. More specifically, the present technology relates to battery cell structures and uses. 
     BACKGROUND 
     In battery-powered devices, batteries may sometimes include overcurrent protection features. While protecting the cell from overcurrent events, the features may be complex and can limit materials available for the cell, or occupy area that could otherwise be used for additional active material. 
     SUMMARY 
     The present technology relates to energy storage devices, including battery cells and batteries, that include an additional electrolyte system for providing overcurrent protection. These additional electrolytes may utilize redox reactions to protect cell components from excess voltage. The electrolyte materials may be included within individual cell structures to provide protection at the level of individual cells as will be described throughout the disclosure. 
     Energy storage devices, battery cells, and batteries of the present technology may include a first current collector and a second current collector. Exemplary battery cells may also include a first region defined between the first current collector and the second current collector. The first region may include electrode materials. The battery cells may also include a second region which may be defined between the first current collector and the second current collector. The second region may be fluidly isolated from the first region. The second region may include an electrolyte. 
     In some embodiments, the battery cells may further include a separator extending through both the first region and the second region. The battery cells may further include a seal at least partially defining the first region and the second region. The second region may be positioned laterally external to the first region, and the seal may define an exterior of the first region and an interior of the second region. The seal may define sidewalls of the second region. Along with the first current collector and the second current collector, the seal may define a cavity within the second region. The seal may define a plurality of separate cavities fluidly isolated from one another and located external to the first region. The electrode materials may include a cathode active material and an anode active material contained within and limited to the first region. The first region may include a first electrolyte, and the second region may include a second electrolyte different from the first electrolyte. The second electrolyte may be configured to remain passive at operating voltages below or about 4.0 V. The second electrolyte may be configured to be electrically activated at operating voltages above or about 4.0 V. The second region may define a plurality of separate cavities fluidly isolated from one another. A first fluid cavity of the plurality of fluid cavities may contain an electrolyte configured to remain passive at operating voltages below or about 4.0 V. A second fluid cavity of the plurality of fluid cavities may contain an electrolyte configured to remain passive at operating voltages below or about 4.3 V. The first current collector and the second current collector may electrically couple the first region and the second region. 
     The present technology also encompasses batteries. The batteries may include a first battery cell including a first current collector. The first battery cell may include a second current collector. The first battery cell may include a first region defined between the first current collector and the second current collector. The first battery cell may also include a second region defined between the first current collector and the second current collector. The second region may be fluidly isolated from the first region, and the second region may include a redox electrolyte. The batteries may also include a second battery cell. The second battery cell may include a third current collector. The second battery cell may include a fourth current collector. The second battery cell may include a third region defined between the third current collector and the fourth current collector. The second battery cell may also include a fourth region defined between the third current collector and the fourth current collector. The fourth region may be fluidly isolated from the third region, and the fourth region may include a redox electrolyte similar to or different from the redox electrolyte of the first battery cell. 
     In some embodiments, the first region and the third region may be interior regions of the first battery cell and the second battery cell. The second region and the fourth region may be exterior regions of the first battery cell and the second battery cell. The batteries may further include a first separator incorporated within the first battery cell and positioned between the first current collector and the second current collector. The batteries may further include a second separator incorporated within the second battery cell and positioned between the third current collector and the fourth current collector. The first separator may extend across each of the first region and the second region, and the second separator may extend across each of the third region and the fourth region. The second region may be vertically offset from the fourth region within the battery. The second region may be electrically coupled with the first region by the first current collector and the second current collector. The fourth region may be electrically coupled with the third region by the third current collector and the fourth current collector. The second region and the fourth region may be electrically isolated from one another. 
     The present technology also encompasses methods of balancing a battery. The methods may include delivering current to the battery from a voltage source. The battery may include a first battery cell including a first current collector and a second current collector. The first battery cell may include a first region defined between the first current collector and the second current collector. The first battery cell may also include a second region defined between the first current collector and the second current collector. The second region may be fluidly isolated from the first region, and the second region may include a redox electrolyte. The battery may also include a second battery cell including a third current collector and a fourth current collector. The second battery cell may include a third region defined between the third current collector and the fourth current collector. The second battery cell may also include a fourth region defined between the third current collector and the fourth current collector. The fourth region may be fluidly isolated from the third region. The fourth region may include the redox electrolyte. The first battery cell may be characterized by a charge level higher than a charge level of the second battery cell. 
     The methods may include supplying additional current to the first battery cell and the second battery cell. The additional current may increase the voltage within the first battery cell to a voltage threshold of the redox electrolyte in the first battery cell. The methods may also include charging the second battery cell to an equivalent level of the first battery cell. In some embodiments, a voltage level within the first battery cell while supplying the additional current may be maintained at the voltage threshold of the redox electrolyte in the first battery cell until the second battery cell is charged to a level associated with a fully charged battery cell. 
     Such technology may provide numerous benefits over conventional technology. For example, the present devices may provide overcurrent protection to each individual cell. Additionally, the described cell structures may provide ways of balancing cells within a battery. These and other embodiments, along with many of their advantages and features, are described in more detail in conjunction with the below description and attached figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A further understanding of the nature and advantages of the disclosed embodiments may be realized by reference to the remaining portions of the specification and the drawings. 
         FIG. 1  shows a schematic cross-sectional view of an energy storage device according to embodiments of the present technology. 
         FIG. 2  shows a schematic cross-sectional view of a current collector according to embodiments of the present technology. 
         FIG. 3  shows a schematic cross-sectional view of an energy storage device according to embodiments of the present technology. 
         FIG. 4  shows a schematic cross-sectional view of a battery cell according to embodiments of the present technology. 
         FIGS. 5A-5B  show cross-sectional views along line A-A of  FIG. 4  of a battery cell according to embodiments of the present technology. 
         FIGS. 6A-6C  show schematic views of battery cells according to embodiments of the present technology. 
         FIG. 7  shows operations of a method of balancing battery cells according to embodiments of the present technology. 
         FIG. 8  shows a schematic cross-sectional view of a battery cell according to embodiments of the present technology. 
         FIG. 9  shows a schematic cross-sectional view of a portion of a battery cell according to embodiments of the present technology. 
     
    
    
     Several of the figures are included as schematics. It is to be understood that the figures are for illustrative purposes, and are not to be considered of scale unless specifically stated to be of scale. Additionally, as schematics, the figures are provided to aid comprehension and may not include all aspects or information compared to realistic representations, and may include exaggerated material for illustrative purposes. 
     In the figures, similar components and/or features may have the same numerical reference label. Further, various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components and/or features. If only the first numerical reference label is used in the specification, the description is applicable to any one of the similar components and/or features having the same first numerical reference label irrespective of the letter suffix. 
     DETAILED DESCRIPTION 
     Batteries, battery cells, and more generally energy storage devices, may be made from a variety of materials. These devices may include one or more safety features including overcurrent protection features that may protect the devices from battery issues or other failures. Overcurrent protection may have one or more components at a cell level as well as components or code at a battery management level. Conventional cells that are charged for a period of time above normal operating voltages may cause metal plating at the cathode, as well as reactions within the cell that may form gases increasing the pressure within the cell, compounding the issues. Some conventional rechargeable battery designs, such as some lithium-ion batteries, have incorporated redox shuttle additives into the electrolyte system of individual battery cells to help address this issue. 
     Electrolytes utilizing redox shuttle additives may provide an amount of overcurrent protection within an individual cell. For example, certain materials may be activated at a particular current or voltage above standard operating voltage of the cell. When the cell is overcharged, the current will begin to raise the voltage within the cell, which may cross a threshold to activate the shuttle additives allowing redox reactions to occur. The shuttle additives may be characterized by faster reaction than the lithium-containing species allowing the redox species to accept the increased current and limit reactions with the lithium-containing species. The shuttle additive may be oxidized at a higher voltage, and may lose an electron to the cathode of the cell. The redox additive cation produced will then diffuse to the anode to obtain a replacement electron and be reduced. The reversible reaction process can continue to occur to shuttle electrons between the two electrodes without causing damage to the electrode materials, such as forcing additional intercalation of lithium ions, or causing dendritic formation issues within a normal cell under overcharge conditions. Put another way, the redox shuttle additive may protect the cell by shunting the current between the positive and negative electrodes, which may maintain the voltage at the oxidation potential of the redox shuttle additives. This may protect the lithium-containing species and electrolyte materials during the overcurrent. 
     Although the additives may provide overcurrent protection, the redox shuttle materials may also pose issues within the cell. For example, the additives are conventionally added directly to the electrolyte mixture. The additives may be characterized by a greater molecular weight than the other components of the electrolyte, which may increase the viscosity of the electrolyte mixture. This increased viscosity may reduce the mobility of the materials within the electrolyte. The inclusion of the additives may also increase the conductivity of the electrolyte, and may restrict the materials that may be used for the electrolyte. For example, the additive would be required to couple with the different materials of the electrolyte, which may limit both the electrolyte materials and the additive materials to compatible compositions. These issues may reduce the life cycle of the battery substantially compared to cells that do not include redox shuttle additives within the electrolyte. 
     The present technology overcomes these issues by forming isolated locations within a battery cell to house a redox electrolyte. By locating the redox electrolyte separately from the electrolyte used with the electrodes, the issues noted above may be obviated. The electrolyte may be electrically coupled with an electrode region of the battery cell, which may allow the redox electrolyte to operate as overcurrent protection for the cell if exposed to excess voltage. Additionally, the present cell designs when used in multi-cell batteries may enable balancing of the individual cells utilizing similar mechanisms of the shuttle electrolyte in different charging schemes. 
     Although the remaining portions of the description will routinely reference lithium-ion batteries, it will be readily understood by the skilled artisan that the technology is not so limited. The present designs may be employed with any number of battery or energy storage devices, including other rechargeable and primary, or non-rechargeable, battery types, as well as electrochemical capacitors also known as supercapacitors or ultracapacitors. Moreover, the present technology may be applicable to batteries and energy storage devices used in any number of technologies that may include, without limitation, phones and mobile devices, handheld electronic devices, laptops and other computers, appliances, heavy machinery, transportation equipment including automobiles, water-faring vessels, air travel equipment, and space travel equipment, as well as any other device that may use batteries or benefit from the discussed designs. Accordingly, the disclosure and claims are not to be considered limited to any particular example discussed, but can be utilized broadly with any number of devices that may exhibit some or all of the electrical or chemical characteristics of the discussed examples. 
       FIG. 1  depicts a schematic cross-sectional view of an energy storage device according to embodiments of the present technology. The energy storage devices may include a single current collector or coupled current collectors. The energy storage devices may operate in a conventional manner with regard to electronic flow across or through material layers, such as providing electronic mobility across an xy-plane of the current collectors. Additionally, the described devices may operate by electronic flow through the structure in a z-direction through individual cells as opposed to via tabbed current collectors as described above for conventional batteries. 
     As illustrated, the stacked battery  100  may include a stack of electrochemical cells C 1 , C 2 , C 3 , and C 4  between end plates  102  and  104 . End plates  102  and  104  may be metal current collector plates, which can serve both electrical and mechanical functions. In some embodiments, end plates  102  and  104  can be support plates that form part of an external housing of the stacked battery. End plates  102  and  104  may also provide mechanical support within a housing of the stacked battery. Some or all of the support plates may be electrically conductive, and there may be a terminal within the support plate that is electrically connected to the end plate. In embodiments an additional plate similar to end plates  102  and  104  may be disposed within the stack of cells, such as between two cells. This configuration including an additional plate may provide structural rigidity, and the additional plate may also preform electronic functions similar to end plates  102 ,  104 . End plates  102  and  104  may act as positive and negative terminals of the battery. The cells may pass current in the z-direction through individual cells to the end plates, which may transfer current in any direction across the plate and from the battery. 
     The stack of electrochemical cells may include any number of electrochemical cells depending on the selected voltage for the stacked battery  100 , along with the individual voltage of each individual electrochemical cell. The cell stack may be arranged with as many or as few electrochemical cells in series as desired, as well as with intervening plates for support and current transfer. The cells C may be positioned adjacent, e.g. abutting, one another in some configurations. Each electrochemical cell C may include a cathode  110  and an anode  120 , where the cathode  110  and anode  120  may be separated by separator  130  between the cathode and anode. Between the anode  120  of cell C 1  and the cathode of adjacent cell C 2  may be a stacked current collector  150 . The stacked current collector  150  may form part of C 1  and C 2 . On one side, stacked current collector  150  may be connected to the seal  140  of C 1  and connected on an opposing side to the seal  140  of C 2 . 
     In some embodiments, as shown in  FIG. 1 , stacked current collector  150  may include a first current collector  152  and a second current collector  154 . In embodiments one or both of the current collectors may include a metal or a non-metal material, such as a polymer or composite. As shown in the figure, in some embodiments the first current collector  152  and second current collector  154  can be different materials. In some embodiments, the first current collector  152  may be a material selected based on the potential of the anode  120 , such as copper or any other suitable metal, as well as a non-metal material including a polymer. The second current collector may be a material selected based on the potential of the cathode  110 , such as aluminum or other suitable metals, as well as a non-metal material including a polymer. In other words, the materials for the first and second current collectors can be selected based on electrochemical compatibility with the anode and cathode active materials used. 
     The first and second current collectors can be made of any material known in the art. For example, copper, aluminum, or stainless steel may be used, as well as composite materials having metallic aspects, and non-metallic materials including polymers. In some instances the metals or non-metals used in the first and second current collector can be the same or different. The materials selected for the anode and cathode active materials can be any suitable battery materials. For example, the anode material can be silicon, graphite, carbon, a tin alloy, lithium metal, a lithium containing material, such as lithium titanium oxide (LTO), or other suitable materials that can form an anode in a battery cell. Additionally, for example, the cathode material can be a lithium-containing material. In some embodiments, the lithium-containing material can be a lithium metal oxide, such as lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, or lithium titanate, while in other embodiments, the lithium-containing material can be a lithium iron phosphate, or other suitable materials that can form a cathode in a battery cell. 
     The first and second current collectors may have any suitable thickness, and may have a thickness that allows for a seal to be formed and provides suitable mechanical stability to prevent failure, such as breakage of the layers, during anticipated usage of the stacked battery. Additionally, the thickness of the current collectors can be sufficiently thin to allow for bending and flexing in the separation region to accommodate expansion anticipated during cycling of the stacked battery, including, for example, up to 10% expansion in the z-direction. 
     Turning to  FIG. 2 , the stacked current collector  150  may have a connection region  153  where the first current collector  152  and second current collector  154  may be connected, and a gap region  155  at the peripheral ends of the collector  150 . In the connection region  153 , the first current collector and second current collector may be in direct contact or otherwise joined to be electrically-conductive. In some embodiments, the first current collector and second current collector may be directly connected, while in other embodiments the first current collector and second current collector may be indirectly connected via a conductive material. To form the connection region  153 , the first current collector  152  and the second current collector  154  may be laminated together. Additionally, the connection region  153  may be created by welding the first current collector  152  and the second current collector  154  together. The connection region  153  may also be created by using an adhesive, which may be electrically conductive, between the first current collector  152  and the second current collector  154 . In other embodiments, the connection region  153  may be created by the wetting that can occur between the materials of the first current collector  152  and the second current collector  154 . 
     In the gap region  155 , the peripheral ends of the first current collector  152  and the second current collector  154  may be spaced apart and moveable relative to each other. As such, there may be a separation distance between the first and second current collectors, which may increase as the electrochemical cell swells. In some embodiments, the spaced apart peripheral ends of the first current collector  152  and the second current collector  154  may be of a length that is sufficient to accommodate an anticipated expansion of the individual electrochemical cells of the stacked battery during cycling of the battery. The peripheral ends of the current collectors  152   a  and  154   a  may have a length L, as shown in  FIG. 2 , which may be long enough that up to or at least about 10% expansion in the z-direction can be accommodated. 
     As shown in  FIG. 1 , each cell C 1 , C 2 , C 3 , and C 4 , also includes a seal  140 , which, with the current collector layers, may electrochemically isolate the electrochemical cells from each other. Thus, each cathode-anode pair may be electrochemically sealed and isolated from neighboring electrochemical cells. Because the current collectors  152  and  154  may be separated at the peripheral ends, separate seals  140  can be formed on opposing sides, such as a top and bottom, of the stacked current collector  150 . The seals  140  may be the same or different materials, and each seal  140  may also be a laminate, composite, or coupling of two or more materials in embodiments. 
     The seal material may be able to bond with the first and second layers of the stacked current collector to prevent electrolyte leakage. The seal material may be a polymer, an epoxy, or other suitable electrically-insulating material that can bond with first and second current collectors to create a seal, which may be a hermetic seal. In some embodiments, the polymer may be polypropylene, polyethylene, polyethylene terephthalate, polytrimethylene terephthalate, polyimide, or any other suitable polymer that may bond with the first and second current collectors of the stacked current collector to form a hermetic seal and may also provide resistance to moisture ingress. The electrolyte may be a solid, a gel, or a liquid in embodiments. The seal may electrochemically isolate each electrochemical cell by hermetically sealing the cell, thereby preventing ions in the electrolyte from escaping to a neighboring electrochemical cell. The seal material may be any material providing adequate bonding with the metal layers such that the seal may be maintained through a predetermined period of time or battery usage. 
     The separator may be wetted with the electrolyte, such as a fluid electrolyte or gel electrolyte, to incorporate the electrolyte into the stacked battery. Alternatively, a gel electrolyte may coat the separator. In still further alternatives, a gel electrolyte may coat the first metal layer and/or second metal layer before combination. Additionally, the electrolyte may be blended with particles of electrode active material. In various embodiments, incorporating the electrolyte into the components of the stacked battery may reduce gassing in the stacked battery. In variations that include a flexible seal, the stacked battery may accommodate gas resulting from degassing. 
     The individual electrochemical cells may be formed in any suitable manner. In some embodiments, the cathode  110 , the anode  120 , and the separator  130  may be preassembled. A first current collector  152  may then be connected to the anode while a second current collector  154  may be connected to the cathode to create a cell. The seal material may be disposed between the first current collector  152  and the second current collector  154  to form seals  140 . Finally, the peripheral ends of the sealed electrochemical cell may be further taped to frame the cell. Tapes  145 , as well as other coatings, sealing, or material layers, may be disposed around the outer perimeter of the metal layers and seals. The tape  145  may be substituted with ceramic or polymeric materials. Tape  145  may be included for various reasons including to prevent shorting to adjacent layers or to surrounding conductive surfaces within the device, to provide improved electrochemical or chemical stability, and to provide mechanical strength. 
       FIGS. 1 and 2  illustrate an exemplary stacked battery design according to the present technology. Additional configurations other than illustrated, or as variations on the designs, are also encompassed by the present technology. For example, certain embodiments may not include an additional seal material, and first current collector  152  and second current collector  154  may be directly coupled or bonded together. Additionally, the current collectors may include designs including combinations of polymer material and conductive materials, such as within a matrix. 
     An exemplary matrix for a current collector may include a polymer disposed as the matrix material or as part of the matrix material. The matrix may provide an insulative design that limits or reduces xy-directional conductivity. The polymer matrix may be developed with a conductive material to produce a current collector having particular electrochemical or composite properties, such as electrical conductivity in the z-direction or through the cell. For example, conductive particulate material may be incorporated within the matrix. The conductive material may include any of the conductive materials previously identified. In embodiments, the conductive material may include one or more of silver, aluminum, copper, stainless steel, and a carbon-containing material. In this way, the current collector may have a tuned resistivity to provide directional control for electrical conductivity. For example, the produced current collector may be configured to provide an in-plane resistivity across a length in the xy-plane, as well as a through-plane resistivity in the z-direction, which is greater than or about 1×10 −4  ohm-m in embodiments. Additionally, exemplary current collectors may have an in-plane and through-plane resistivity of between about 1×10 −3  ohm-m and about 1,000 ohm-m. In other embodiments, more conventional electrical distribution may be employed, where current is transferred along conductive current collectors into and out of the cell. 
     The present technology may also be applicable in other cell designs utilizing xy-plane current transfer. Turning to  FIG. 3  is shown a schematic view of an energy storage device  300  according to embodiments of the present technology. Energy storage device  300  may be a battery cell or may be a composite battery. Energy storage device  300  may be characterized by a number of structural configurations including a cylindrical cell design, a jelly roll design, a pouch design, or a prismatic design, for example. As illustrated, energy storage device  300  may include battery cell material  310 , which may be a jelly roll or layers of material stacked or overlapped in various configurations. The cell material  310  may be electrode materials for an anode and cathode of an electrochemical cell. As would be readily understood, the layers are not shown at any particular scale, and are intended merely to show the possible layers of cell material  310 . As illustrated, cell material  310  may include a cathode current collector  307 , which may be coupled with a cathode electrode material  309 . In embodiments, cathode current collector  307  may be aluminum, and may also be alternative metals or conductive materials that may be stable at potentials above about 3 V, for example. Cathode current collector  307  may be coated or coupled with a cathode active material  309 , which may include a lithium-containing compound in embodiments. 
     Cell material  310  may also include an anode current collector  311 , which may be coupled with an anode electrode material  313 . Anode current collector  311  may be copper in embodiments, and may also be alternative metals or conductive materials that may be stable at potentials below about 1 V, for example. Anode current collector  311  may be coated or coupled with anode active material  313 , which may include a carbon-containing compound in embodiments. A separator  316  may be disposed between the electrodes, and may be a polymer film or a material that may allow lithium ions to pass through its structure while not otherwise conducting electricity. 
     Although illustrated as single layers of electrode material, cell material  310  may be any number of layers. Although the cell may be composed of one layer each of anode and cathode material as sheets, the layers may also be formed into a jelly roll design, or folded design, such that any number of layers may be included in cell material  310 . For embodiments which include multiple layers, the tab portions of each anode current collector may be coupled together, as may be the tab portions of each cathode current collector. 
     Turning to  FIG. 4  is shown a schematic cross-sectional view of a battery cell  400  according to embodiments of the present technology. Battery cell  400  may include aspects of any of the previously described battery cells of  FIGS. 1 and 3 . Battery cell  400  may be utilized in a variety of energy storage devices previously described, and may be part of a rolled, stacked, prismatic, or any other battery type. Battery cell  400  may include aspects of the present technology, which may allow overcurrent protection within the battery cell  400 . Battery cell  400  may be used in a single cell or multi-cell battery, and when used in a multi-cell battery may be used with one or more additional battery cell  400  structures. 
     Battery cell  400  may include a first current collector  405  and a second current collector  410 . Either current collector may be an anode current collector with the other operating as a cathode current collector. The current collectors may be similar or different materials in embodiments, and may be characterized by any of the previously described materials, including metals such as copper, aluminum, nickel, stainless steel, or other metals that may operate at anode or cathode potential, as well as non-metal or metal-containing materials, such as polymers or structures which may include an amount of conductivity to provide current either across or through the current collector. In embodiments in which the current collectors are utilized in a stacked structure, such as similar to those described with respect to  FIG. 1 , the current collectors may be characterized by an amount of xy-direction conductivity in addition to the z-direction conductivity. Although the xy-direction conductivity may be limited based on the cell operation, the xy-direction conductivity may assist electrical coupling of the regions of the battery cell  400  discussed in more detail below. 
     Battery cell  400  may also be characterized by different regions, which may include or contain the different operational structures within the battery cell. For example, battery cell  400  may include a first region  420 , which may be at least partially defined from above by first current collector  405  and may be at least partially defined from below by second current collector  410 . First region  420  may include electrode materials, and may include the active materials within the cell. The electrode materials may include a first active material  407  associated with first current collector  405 , and may include a second active material  412  associated with second current collector  410 . The active materials may be or include a cathode active material and an anode active material to be utilized in power functions of the cell. 
     The cathode active materials may include any of the previously described materials, and may include a lithium-containing material in embodiments, although any cathode active materials for primary or secondary batteries may be suitable with the present technology. Similarly, the anode active material may include any of the previously described materials, including a carbon-containing material, although again any anode active materials in primary or secondary batteries may be suitable with the present technology. As will be explained further below, first region  420  may contain the active materials within the cell, and in some embodiments, first active material  407  and second active material  412  may be limited to first region  420 , and may not be included in other regions of the battery cell  400 . 
     Battery cell  400  may also include a second region  430  in embodiments. Second region  430  may also be at least partially defined from above by first current collector  405 , and may be at least partially defined from below by second current collector  410 . Second region  430  may be adjacent first region  420 , and in some embodiments, second region  430  may be fluidly isolated from the first region  420 . While first region  420  may include the active cell materials in some embodiments, second region  430  may include active materials, although in some embodiments second region  430  may not include any active materials. Second region  430  may include an electrolyte within the second region, and the electrolyte in second region  430  may be a redox electrolyte in some embodiments. 
     Exemplary battery cells may include one or more other cell materials as previously described, and may include a separator  415 . Separator  415  may be a polymeric material, and may be any of the materials previously described. Separator  415  may include a single film of material used within the battery cell  400 , although in other embodiments separator  415  may include multiple separators including different materials utilized in different regions of the cell. The separator  415  may include multiple materials coupled together in embodiments, and may utilize different materials based on their compatibility with electrolyte materials within the first region  420  or the second region  430  in embodiments. In some embodiments, as illustrated, separator  415  may extend across battery cell  400 . Separator  415  may extend through first region  420  and also extend into, across, or through second region  430  so as to extend through both the first region  420  and the second region  430 . As noted above, in some embodiments, second region  430  may not include active materials. However, because first current collector  405  and second current collector  410  may extend across second region  430 , an electronic barrier, such as separator  415 , may be included within second region  430  to limit shorting between the two current collectors, which may be operating as positive and negative current collectors of battery cell  400 . 
     Battery cell  400  may also include a seal  440  within the cell structure. Seal  440  may include a single seal having defined characteristics discussed below, or may include multiple seals. For example, a first seal  440   a  may be included between the first region  420  and the second region  430  in embodiments. First seal  440   a  may provide the fluid isolation as well as electrical isolation between the first region  420  and the second region  430  in embodiments. First seal  440   a  may at least partially define one or both of the first region  420  and the second region  430 . As illustrated, although second region  430  may be located in a variety of positions relative to first region  420 , in some embodiments second region  430  may be positioned laterally external to the first region  420  within battery cell  400 . First seal  440   a  may be positioned to define sidewalls of one or both of first region  420  and second region  430 . For example, as illustrated, first seal  440   a  may define an exterior sidewall of first region  420 . First seal  440   a  may also define an interior sidewall of second region  430 . 
     Separator  415  may extend across first seal  440   a  in embodiments, and first seal  440   a  may include a two-part design to accommodate separator  415 . For example, a first part of first seal  440   a  may be coupled with first current collector  405 , and a second part of first seal  440   a  may be coupled with second current collector  410 . During fabrication, separator  415  may be positioned between the first part and the second part of first seal  440   a , for example, and the materials may be sealed together in one or more ways, such as by heat pressing the materials together. This may allow separator  415  to extend across both first region  420  and second region  430 , while allowing a fluid seal to be formed between the two regions with separator  415 . 
     Battery cell  400  may also include a second seal  440   b , which may define an exterior of second region  430 . Second seal  440   b  may be part of first seal  440   a  to produce a single seal for the cell, although in some embodiments second seal  440   b  may be a separate component from first seal  440   a . Second seal  440   b  may define an exterior of battery cell  400  as well, and may provide a hermetic seal for the battery cell to prevent both ingress of vapor as well as egress of electrolyte, gases, or other materials from the cell. Second seal  440   b  may be the same material or materials as first seal  440   a , although in other embodiments second seal  440   b  may be a different material from first seal  440   a . For example, first seal  440   a  and second seal  440   b  may perform different functions within the cell, for which different materials may facilitate the individual functions. For example, first seal  440   a  may include materials that may be compatible with active materials and electrolyte materials of first region  420  as well as electrolyte materials of second region  430 . Second seal  440   b  may include materials that may be compatible with electrolyte materials of second region  430 , and may also provide decreased water permeability to enable improved protection from water ingress to battery cell  400 . 
     Second seal  440   b  may also be or include a two part design, and may include or be part of the two parts of first seal  440   a . For example, separator  415  may extend through second seal  440   b  as well in some embodiments, and may extend fully through battery cell  400 . Second seal  440   b  may include a first part coupled with first current collector  405 , which may or may not be a single piece of material including a first part of first seal  440   a  as well. Similarly, second seal  440   b  may include a second part coupled with second current collector  410 , which also may or may not be a single piece of material including a second part of second seal  440   b  as well. A number of combinations of seal materials  440  have been described, and it is to be understood that any number of combinations or differentiations based on this discussion are similarly encompassed by the present technology. 
     Seal  440  with first current collector  405  and second current collector  410  may define a cavity  450  within second region  430  of battery cell  400 . Cavity  450  may be characterized by a number of shapes and volumes. Additionally, separator  415  materials may be formed or located to define a plurality of cavities  450  throughout the battery cell  400 , which may be located about or external to first region  420  of battery cell  400 . Turning to  FIGS. 5A-5B  is shown cross-sectional views along line A-A of  FIG. 4  of a battery cell  500  according to embodiments of the present technology. Battery cell  500  may include any of the aspects of battery cell  400  as previously described, and may also include any of the aspects of the batteries and components discussed previously with respect to  FIGS. 1 and 3 , for example. As illustrated, the cross-sectional view is provided below separator  415 , which may be above the view illustrated. However, separator  415  may be included in any fashion as previously discussed, and may be included across the entire area of battery cell  500 , and may extend past one or more outer edges of the cell. 
     As shown in the plan view cross-sectional schematic of  FIG. 5A , battery cell  500  may include a current collector  410  on which a number of components may be positioned, or with which the materials may be coupled. An active material  412  may be positioned on current collector  410 , and may be included in a first region  420  of battery cell  500 . Additionally, a seal material  440  may be positioned on current collector  410 . As previously discussed, seal material  440  may be a single piece across current collector  410 , or may be or include two or more pieces which may define one or more cavities  450  along second region  430  of current collector  410 . The embodiment illustrated in  FIG. 5A  includes two elongate cavities  450   a ,  450   b  distributed on opposite sides of first region  420 . The cavities  450  may be any length or shape, and in some embodiments may be a single form extending around the entire circumference of first region  420 . 
       FIG. 5B  shows an additional structural configuration of battery cell  500  in which an additional array of cavities  450  may be included. As illustrated in  FIG. 5B , the battery cell includes current collector  410  on which an active material  412  is positioned in first region  420 . Additionally, the cell may include one or more seal materials  440  in second region  430 . The seal materials  440  may define cavities  450  about first region  420 . As shown, the cavities  450  are distributed about first region  420 , and may be arranged with seal materials  440  to be fluidly separate from one another. As will be explained below, this may afford tuning of the electrolyte materials within the cavities  450  in second region  430 . 
     As noted previously, the first region  420  of the battery cells  400 ,  500  may include electrode materials, and may also include a first electrolyte, which may include one or more salts, solvents, and other materials or additives. In embodiments, the first electrolyte may not include any of the redox additives discussed previously, which may avoid the issues discussed previously. The materials within the first electrolyte may be any one of many known materials used in electrolytes for secondary or rechargeable batteries, which may include lithium-ion batteries as well as any other type of rechargeable battery that may use an electrolyte. For example, such as with a lithium-ion battery, the first electrolyte may include one or more lithium salts dissolved in one or more solvents, which may be non-aqueous in embodiments, and may include organic solvents. For example, the salts may include LiPF 6 , LiBF 4 , or LiClO 4 , among other lithium-containing materials. Exemplary solvents may include, for example, ethylene carbonate, dimethyl carbonate, diethyl carbonate, propylene carbonate, and other organic solvents. By utilizing these materials without redox additives, the electronic capabilities of the cell may be maintained at higher efficiency than when additional materials are incorporated within the first electrolyte. 
     The cavities defined within the second region  430  of each battery cell  400 ,  500 , may include a second electrolyte. The second electrolyte may be different from the first electrolyte, and the second electrolyte may be or include a redox electrolyte in embodiments, and may be configured to operate during overcurrent events. The second electrolyte may include similar or different solvents as the first electrolyte, and may or may not include lithium-containing compounds or other metal salts as may be utilized in the first electrolyte to promote cell activity. For example, some embodiments of the second electrolyte may not include lithium-containing compounds, similar to the first electrolyte, which may not include any of the second electrolyte components discussed here. The second electrolyte components may include one or more organometallic compounds, and may include components having one or more aromatic rings or aryl groups in embodiments. For example, the components may include one or more phenyl groups, or substituted aromatic compounds. The substitutions may include nitrogen or other elements. Exemplary compounds that may be utilized in the present technology include dihydrophenazine, dimethoxybenzene, derivatives of such, or other compounds including one or more methoxy groups, ferrocene or other metallocenes, thiantlurene, phenothiazine or other sulfur, halogen, acetyl, or alkyl containing materials. By utilizing such compounds, the voltage limits of the produced electrolyte may be tuned above 4.0 V vs. Li/Li + . 
     Some of the compounds may include high-molecular weight compounds, which as previously discussed may reduce the efficiency of the electrolyte in the standard cell, but which may be beneficial in separate cavities within the battery cell structure. Utilizing different compounds or different combinations of compounds may allow the second electrolyte to be oxidized at particular voltages. For example, the second electrolyte may be tuned to be oxidized above 4.0 V, which may allow the material to remain passive below 4.0 V, or during standard operation of the cell. Accordingly, current delivered to and from the battery cell may be provided through the first section of the cell in which the electrode materials may reside. The first electrolyte may allow oxidation to occur during a voltage window below or about 4.3 V, and may operate within a voltage window below or about 4.2 V, below or about 4.1 V, below or about 4.0 V, below or about 3.9 V, below or about 3.8 V, below or about 3.7 V, below or about 3.6 V, below or about 3.5 V, below or about 3.4 V, below or about 3.3 V, or lower depending on the composition of the cell components. 
     The second electrolyte may remain passive within these voltage ranges, and may not be electrically active. Once the voltage exceeds a threshold to begin oxidation of components within the second electrolyte, current may be shunted from the first region into the second region where the second electrolyte may reside. The first current collector and the second current collector may electrically couple the first region and the second region, which may allow current to be consumed within either region of the battery cell. One or more components of the second electrolyte may become electrically active, or may begin to oxidize, at a voltage window above or about 3.5 V, and may begin to oxidize above or about 3.6 V, above or about 3.7 V, above or about 3.8 V, above or about 3.9 V, above or about 4.0 V, above or about 4.1 V, above or about 4.2 V, above or about 4.3 V, above or about 4.4 V, above or about 4.5 V, or higher in embodiments. Below any of these ranges, the second electrolyte may be configured to remain passive in embodiments. The redox reactions may be faster occurring within the second electrolyte, which may allow the material to continue to shunt current away from the first region until the overcharge situation has finished or been resolved. The redox reaction occurring within the second electrolyte may be considered a controlled short within the second region, where the reversible shuttling converts the overcharge current into heat to be dissipated from the battery cell. This may allow the battery cell to avoid performing the reactions at the electrodes at high voltage, which may degrade the materials within the cell. 
     The second electrolyte may be configured to begin oxidation at or within any of the ranges discussed above. In some embodiments, different configurations of the second electrolyte may be included in different cavities of the battery cell in order to provide further tuning during overcurrent scenarios. For example, referring back to  FIG. 5A , in some embodiments the second electrolyte contained in cavity  450   a  may be differently tuned from the second electrolyte contained in cavity  450   b . Both of the second electrolytes may be configured to remain passive at operating voltages below or about 4.0 V, and may begin oxidation at voltages above or about 4.0 V. Either of the second electrolytes may be tuned to begin oxidation in any of the ranges discussed above. For example, the electrolyte in cavity  450   a  may be configured to remain passive at operating voltages below or about 4.0 V, and may begin oxidation reactions to shunt current above or about 4.0 V. Additionally, the electrolyte in cavity  450   b  may be configured to remain passive at operating voltages below or about 4.3 V, and may begin oxidation reactions to shunt current above or about 4.3 V. Alternatively, the electrolyte in cavity  450   a  may electrically activate at 4.3 V, and the electrolyte in cavity  450   b  may electrically activate at 4.5 V. Any additional amounts and ranges may be used as well and are understood to be encompassed by the present technology. 
     By utilizing a range that may be above normal operating ranges by a certain amount, unnecessary shunting may be avoided during normal operating fluctuations, and shunting may be reserved for actual overcurrent events to maintain full efficiency of the battery cell. By utilizing differently tuned amounts of the second electrolyte, a first portion of the second electrolyte may be utilized as an overcurrent event begins, and a second portion of the second electrolyte may be reserved for scenarios of additional overcurrent events or in the event of the overcurrent event deteriorating to a greater degree. Additionally, such as with structures illustrated in  FIG. 5B  in which more cavities are defined about the second region, each amount may be differently tuned in a variety of ways from the second electrolyte included in one or more other regions to provide multiple protection levels activated at different voltage levels. 
     The battery cells of the present technology may also be utilized in combination with other battery cells that may be similar or also include a second electrolyte according to the present technology. Turning to  FIGS. 6A-6C  is shown schematic views of battery  600 , which may be similar to batteries discussed with respect to  FIGS. 1 and 3  as well as other battery designs that may utilize the present technology. Battery  600  may include a first battery cell  602   a  and a second battery cell  602   b  according to embodiments of the present technology. Battery cells  602   a  and  602   b  may be similar to any of the battery cells previously discussed, and may show a configuration of multiple cells in a battery according to the present technology. The battery  600  may include cells  602  and may include any number of cells as previously described. Battery cells  602  may each include similar components as discussed previously with respect to  FIG. 4 . 
     For example, as shown in  FIG. 6A , battery cell  602   a  may include a first current collector  405   a  and a second current collector  410   a . Battery cell  602   b  may include a third current collector  405   b  and a fourth current collector  410   b . For example, current collector  405  may be a cathode current collector, and current collector  410  may be an anode current collector, although in other embodiments the current collectors may be reversed. A first active material  407 , which may be a cathode active material, may be in contact with the first current collector  405 . A second active material  412 , which may be an anode active material, may be in contact with the second current collector  410 . Battery cells  602  may include a seal material  440  as previously described, which may be configured to separate battery cell  602   a  into a first region  420   a  and a second region  430   a , and separate battery cell  602   b  into a third region  420   b  and a fourth region  430   b . Seal material  440  may maintain the second region  430   a  and fourth region  430   b  fluidly isolated from the first region  420   a  and the third region  420   b.    
     The battery electrode materials may be limited to the first region  420 , which may be an interior region, and the second region may include a redox electrolyte, which may be an exterior region, in embodiments as previously discussed. Seal material  440  may include a first portion of the seal material, such as portions  440   a  and  440   c , and a second portion of the seal material, such as portions  440   b  and  440   d , which may define one or more cavities  450  as previously described. Each battery cell  602  may also include a separator  415  disposed between the current collectors in any of the configurations previously described. For example, a first separator  415   a  may extend across the first region and the second region, and a second separator  415   b  may extend across the third region and the fourth region. The separators may be similar or different materials, and may include any of the materials previously identified. In embodiments, the first current collector and second current collector may electrically couple the first region and the second region, and the third current collector and the fourth current collector may electrically couple the third region and the fourth region to allow the current shunting as previously described. In embodiments, the second region may be fluidly isolated from the fourth region, and in embodiments each region may be fluidly isolated from any other region. 
       FIG. 6B  illustrates cross-sectional views of battery cells  602   a - b  along lines A-A and B-B of  FIG. 6A . These views may illustrate additional configurations of cavities  450  within the individual battery cells. The plan view of battery cell  602   a  may include a view of second current collector  410   a . The cell may include a first region  420   a  in which active material  412   a  may be positioned. The cell may include one or more seal materials  440   a - b , which may at least partially define one or more cavities  450   a  in second region  430   a . Similarly, battery cell  602   b  may include current collector  410   b , which may include a third region  420   b  in which active material  412   b  may be positioned or disposed. Battery cell  602   b  may also include one or more seal materials  440   c - d , which may at least partially define one or more cavities  450   b  in fourth region  430   b.    
     The cavities  450   a  of battery cell  602   a  may be similar or different from the cavities  450   b  of battery cell  602   b . For example, the cavities may be the same size or different sizes in embodiments. Cavities  450  may include the redox electrolyte, which may be similar to the second electrolyte previously discussed. The electrolyte may be the same or different between cells, and may be tuned to the same or different voltage, for example. Additionally, the redox electrolytes may include multiple tuned portions of electrolyte distributed throughout multiple cavities of each battery cell. In some embodiments each battery cell  602  may be formed similarly to one another. In other embodiments, cavities in a first battery cell may be offset from cavities in a second battery cell. For example, as illustrated, cavities  450   a  may be offset from cavities  450   b , which may reduce contact between the associated current collectors or regions of the battery cells. 
       FIG. 6C  illustrates a plan view through line A-A of battery  600 , which shows cavities  450   b  in hidden view through the structure. The figure illustrates that cavities  450   b  may be vertically offset from cavities  450   a  in some embodiments. This may reduce or prevent contact between these regions of the battery compared to directly in line cavities. In other embodiments, the cavities may be in line, and the battery cells may be identical to one another to facilitate fabrication. The cavities in which the redox electrolyte is contained may not be characterized by the same thickness as the first region of the battery cells where the electrode active materials are contained, which may similarly prevent or reduce contact between current collectors in the second region. 
     When multiple cells or all cells in an exemplary battery include regions including the second electrolyte, or shuttle electrolyte, the battery configuration may afford additional balancing capabilities. In batteries including multiple cells, over time one or more cells may weaken compared to other cells, and may under charge or over discharge. Balancing the cells relative to one another may protect the cells from detrimental effects over time. The present technology may allow balancing at regular intervals utilizing the redox electrolyte to enable additional charging to assist balancing a weaker cell. 
       FIG. 7  shows operations of a method  700  of balancing battery cells according to embodiments of the present technology. The method may include delivering current to a battery from a voltage source at operation  710 , such as during charging. The battery may include multiple cells, and may be similar to battery  600  or any other battery previously described. The battery may include at least two cells having characteristics of the previously discussed cells, and may include a redox electrolyte in distinct regions of the battery cells. The battery cells may be out of balance, and a first cell of the battery may be characterized by a charge level higher than a second cell of the battery. The present technology may utilize the redox electrolytes at intervals of charging to ensure each cell within the battery is similarly charged. For example, the balancing may be performed when a particular cell registers a voltage indicating it is out of balance, or the balancing operation may be performed every charge, or may be performed after a number of charges greater than or about 2 charges, greater than or about 5 charges, greater than or about 10 charges, greater than or about 25 charges, greater than or about 50 charges, greater than or about 100 charges, greater than or about 200 charges, or more. 
     When performed, the method may include supplying additional current to the battery cells at operation  720 . The operation may occur when the first battery cell has reached full charge, and the voltage begins to rise within the cell. As the additional current continues to be delivered to the battery, the first battery cell may reach a voltage level at which the redox electrolyte begins oxidation in order to protect the electrode materials within the cell. The redox electrolyte within the first battery cell may shunt current from the electrode materials in the first battery cell while the second battery cell characterized by a lower charge level is brought into balance. By shunting the additional current delivered, the first battery cell may be maintained at a voltage threshold of the redox electrolyte, which may limit the voltage within the first battery cell from continuing to rise. This may occur until the second battery cell is brought into balance. For example, the additional current may be delivered, and the second battery cell may be charged to a level associated with a fully charged battery cell at operation  730 . When all battery cells within the battery read a voltage level indicating full charge or a voltage level activating the redox electrolyte, the charging operation may be ceased as all batteries may be in balance again. By utilizing the redox electrolytes in the structures described, overcurrent protection may be provided, while cell performance may be maintained by fluidly isolating the redox electrolyte from the electrolyte in contact with the electrode active materials. 
     Turning to  FIG. 8  is shown a schematic cross-sectional view of a battery cell  800  according to embodiments of the present technology. Battery cell  800  may include aspects of any of the previously described battery cells including  FIG. 4 . Battery cell  800  may be utilized in a variety of energy storage devices previously described, and may be part of a rolled, stacked, prismatic, or any other battery type. Battery cell  800  may include aspects of the present technology, which may allow overcurrent protection within the battery cell  800 . Battery cell  800  may be used in a single cell or multi-cell battery, and when used in a multi-cell battery may be used with one or more additional battery cell  800  structures. 
     As illustrated, battery cell  800  may include multiple components previously described. For example, battery cell  800  may include a first region  820 , which may include a first active material  807  and a second active material  812  as previously described. The active materials may be included between a first current collector  805  and a second current collector  810 . Separating the active materials may be a first separator  815 . Battery cell  800  may also include a second region  830  in embodiments. Second region  830  may also be at least partially defined from above by first current collector  805 , and may be at least partially defined from below by second current collector  810 . Second region  830  may be adjacent first region  820 , and in some embodiments, second region  830  may be fluidly isolated from the first region  820  with seal material  840  as previously described, which may include first seal  840   a  providing fluid isolation between first region  820  and second region  830 . Second seal  840   b  may be a part of first seal  840   a  and may define an exterior of battery cell  800 , all as previously described, although second seal  840   b  may also be separate from first seal  840   a  in embodiments. 
     Seal  840  may at least partially define a cavity  850 , which may include a redox electrolyte as previously described. Battery cell  800  may include multiple redox sections compared to other embodiments. For example, as discussed above, the redox electrolyte may provide an amount of overcurrent protection during operation when cell voltage exceeds a defined threshold for the redox electrolyte. When a single redox electrolyte material is utilized in some embodiments, the materials available having operational ranges as discussed above may be limited. For example, at a desired overcurrent protection above 4.0 V, or any other voltage previously noted, fewer materials may be characterized by activation at or above this range. However, battery cell  800  illustrates an exemplary second region  830  including multiple redox electrolyte sections configured in series. Such a configuration may allow additional materials to be utilized by dividing the threshold voltage by the number of redox sections included in series within each cavity. 
     For example, second region  830  may include three redox sections  855 , although in embodiments second region  830  may include two, three, four, five, six, or more redox sections. By utilizing multiple redox sections coupled in series between first current collector  805  and second current collector  810 , the threshold voltage to perform shuttling may be divided accordingly. For example, for a battery cell characterized by a threshold voltage for shuttling of 4.2 V, when three redox sections are utilized in series, each may be configured for a voltage of 1.4 V, which may allow a greater variety of materials to be used. Because the redox sections  855  may be coupled in series with one another, and in parallel with first region  820 , the redox sections may not operate until the voltage exceeds the additive voltage of the sections, limiting the redox shuttling to operational situations above the desired threshold voltage. 
     To form a number of serially connected redox sections  855 , cavity  850  may include additional electrode components, such as redox electrodes  860 , which may divide the individual redox sections. Each redox section may also include a redox separator  865 , which may ensure shorting does not occur across the redox sections. Redox electrodes  860  may include any electrode component previously described, and may include stainless steel in some embodiments, although materials may also be selected at least in part based on the redox shuttle electrolyte materials. Additional components may be included such as copper, aluminum, silver, and any transition metal or transition metal compound that may operate at potentials sought for the cell, as well as any material previously described. The redox electrodes  860  and redox separators  865  may be included within cavity  850 , and may be incorporated within seal  840  to ensure fluid separation between each redox section  855 . 
     Redox electrodes  860  may be operated as bipolar electrodes between each redox section  855 , where there may not be a direct electrical connection with redox electrodes  860  between current collectors  805 ,  810 . This may allow electrical separation of each section across the cavity, producing a series electrical coupling across the cavity between the first current collector  805  and the second current collector  810 . Additionally, each redox section  855  may include separate redox electrodes as illustrated in  FIG. 9 . 
       FIG. 9  illustrates a partial cross-sectional view of a battery cell  900  according to embodiments of the present technology. Battery cell  900  may include components similar to any of the previously described battery cells, including  FIG. 8  illustrating multiple redox sections. Battery cell  900  may illustrate a portion of second region  930  of battery cell  900 . It is to be understood that the battery cell may also include any of the components previously described, and may include a first section similar to any first section including active materials. Battery cell  900  may include a first current collector  905  and a second current collector  910 . Battery cell  900  may also include a seal  940  including a first seal  940   a , which may separate second region  930  from a first region not shown, and a second seal  940   b  contributing to an exterior of battery cell  900 . First seal  940   a  and second seal  940   b  may or may not be joined or be part of the same seal material in embodiments, such as previously described. 
     Defined by seal  940  may be a cavity  950 , which may be similar to any of the cavities previously described in which a redox shuttle electrolyte may be contained. Battery cell  900  illustrates three redox sections  955 , although it is to be understood that any number of redox sections may be included based on the threshold voltage for redox shuttling of an incorporated electrolyte. Each redox section may include at least one internal electrode in the series operation. While  FIG. 8  illustrated a bipolar internal electrode  860  separating the redox sections, battery cell  900  may include coupled electrodes between each redox section. 
     For example, and based on the exemplary three redox sections illustrated, a first redox section  955   a  may extend from current collector  905  to first internal electrode  960 . Separator section  965   a  may extend within the redox section to limit or prevent shorting between the current collector  905  and the electrode  960 . Electrode  960  may be electrically coupled with a second internal electrode  962 , which may form part of second redox section  955   b . In some embodiments electrode  960  and electrode  962  may be directly connected or coupled, while in other embodiments a layer of material may be disposed between the electrodes. Redox section  955   b  may extend to a third internal electrode  963 , which may form the electrical boundary for redox section  955   b . A second separator section  965   b  may be included within redox section  955   b . Third internal electrode  963  may be electrically coupled with a fourth internal electrode  964 , which may at least partially define a third redox section  955   c . Third redox section  955   c  may extend from the fourth internal electrode  964  to second current collector  910 , which may complete the series configuration of the redox sections. Similar to the other redox sections, third redox section  955   c  may include a separator material  965   c  between the electrodes. It is to be understood that the redox sections  955  may be extended to any number of redox sections to produce a series threshold redox shuttling voltage based on the redox shuttle electrolyte utilized within the system. 
     Because the multiple redox sections may divide the threshold redox shuttling voltage by the number of cells included, a number of additional redox shuttling electrolytes may be utilized in accordance with the present technology. Accordingly, the electrolytes may include aqueous electrolytes, as well as a variety of acids, including one or more ions of various materials. For example, exemplary electrolyte materials may include one or more solutions including one or more elements of bromine, chlorine, iodine, chromium, nitrogen, oxygen, mercury, or other materials that may provide a redox potential that when included in a number of series redox sections may provide a threshold redox shuttling reaction to provide overcurrent protection to the battery cell. 
     In the preceding description, for the purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present technology. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details. 
     Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the embodiments. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present technology. Accordingly, the above description should not be taken as limiting the scope of the technology. 
     Where a range of values is provided, it is understood that each intervening value, to the smallest fraction of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Any narrower range between any stated values or unstated intervening values in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of those smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included. Where multiple values are provided in a list, any range encompassing or based on any of those values is similarly specifically disclosed. 
     As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a material” includes a plurality of such materials, and reference to “the cell” includes reference to one or more cells and equivalents thereof known to those skilled in the art, and so forth. 
     Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”, “include(s)”, and “including”, when used in this specification and in the following claims, are intended to specify the presence of stated features, integers, components, or operations, but they do not preclude the presence or addition of one or more other features, integers, components, operations, acts, or groups.

Metadata:
Filing Date: 20180718
Publication Date: 20211130
Grant Date: 20211130
Priority Date: 20170809
Inventors: ZENG, Qingcheng
Assignee: APPLE INC
CPC Classifications: [{"code": "H01M50/183", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M50/409", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02E60/50", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y02P70/50", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y02E60/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M50/186", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M50/184", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/52", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/0585", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01M10/0567", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/0566", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/4235", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/441", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M4/0404", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/0525", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M2200/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M2004/027", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M2004/028", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M4/661", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01M10/425", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M4/583", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M8/188", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M2004/027", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M8/188", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M2200/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M4/583", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M4/0404", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/0525", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M4/661", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01M2004/028", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M10/425", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/441", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M50/409", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M50/183", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 78767929