Patent Publication Number: US-2021184265-A1

Title: Stacked prismatic architecture for electrochemical cell

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a U.S. National Phase of International Patent Application Serial No. PCT/US2018/036294 entitled “STACKED PRISMATIC ARCHITECTURE FOR ELECTROCHEMICAL CELL”, filed on Jun. 6, 2018. International Patent Application Serial No. PCT/US2018/036294 claims priority to U.S. Provisional Application No. 62/520,478, entitled “STACKED PRISMATIC ARCHITECTURE FOR ELECTROCHEMICAL CELL”, and filed on Jun. 15, 2017. The entire contents of each of the above-listed applications are hereby incorporated by reference for all purposes. 
    
    
     FIELD 
     The present application relates a battery cell system and a method for manufacturing a battery cell system. 
     BACKGROUND AND SUMMARY 
     The search for cost-effective solutions to increase battery capacity is a significant challenge. As the price-per-kWh continues to drop for battery electrochemical storage, there is a need to build larger, higher-capacity batteries which can also be used for high-power applications. Many types of electrochemical cells have electrodes in ‘sheet’ form, wherein sheets of positive and negative electrode material are stacked together and separated by electrically insulating porous separator sheets. In order to increase overall capacity (e.g., total usable energy) of the cell, close contact between sheets, or electrodes, may be desired. 
     A large geometric surface area may be desired for a high-power, low-impedance electrochemical cell having stacked prismatic cell architecture. In manufacturing a typical battery comprising a stacked prismatic cell, the stack is formed by layers of electrode cells which may contain lithium-ion or other electrochemical materials useful for secondary batteries, or secondary cells. When the electrodes of the electrode stack remain in very close contact with one another throughout the life of the cell, the battery can achieve a desired capacity. However, if the electrode stack achieves less than desired contact between sheets, then tension between sheets or between sheets and the battery housing may arise due to gas generated within the battery during the cycling of the battery. In order to increase battery capacity and provide desired electrode stacking, many solutions have been proposed. 
     One proposed example is shown in U.S. Pat. No. 8,133,609. Therein, a battery comprising a plurality of cells, or plates, has tabs from each cell welded to a lead portion, and the lead portion is protected by an enclosure. Another example is shown in U.S. Pat. No. 6,159,631. Therein, a variety of scored regions located on a cell can, or housing, are provided in order to release excess pressure over a narrow and controllable range, in order to avoid explosion in the event of a large battery swell. 
     However, the inventors herein have identified potential issues with such systems related to layering of battery cells, welding of battery cells, housing manufacture and assembly, and the design and manufacture of release or safety ventilation. For example, a normal battery having a high-power stacked prismatic cell has a plurality of layers of cells, or electrode cells. The number of layers is limited by the welding technique used to weld the tabs, or electrodes, of each layer together. In particular, the number of electrodes included in a cell is limited by the durability of electrode tabs when exposed to the energy of welding. Thus, as the number of electrodes increases, and therefore the weld intensity needed to weld all of the electrodes increases, the electrodes may be more susceptible to degradation (e.g., melting, deformation, etc.). For example, current manufacturing techniques utilize a large electrode dimension and a layer count often less than 60 layers, and typically in the range of 20-30 layers. Additionally, the thickness of a cell may be limited to 15 mm due to manufacturing limitations of the housing. 
     Furthermore, the housing imposes an additional limitation of constraining the depth to which housing material can be formed. Often housing is formed from aluminum, and the shape of the housing is formed from aluminum sheet metal in a similar fashion to the way in which sheet metal is stamped. However, during conventional housing forming processes, the aluminum, or other housing material, is stretched and its thickness is reduced, thereby reducing the strength of the material. Additionally, previous secondary, or rechargeable, batteries do not include safety valves or gas-releasing apparatus in order to deal with catastrophic failure of one or more battery cells. 
     In one embodiment, some of the above issues may be at least partially addressed by a battery cell system comprising an electrode stack including a first anode with a first anode tab, a second anode with a second anode tab laterally offset from the first anode tab, a first cathode with a first cathode tab, and a second cathode with a second cathode tab laterally offset from the first cathode tab. By offsetting tabs of like polarity electrodes, the number of electrode tabs in a welded group may be reduced, if desired. As such, the number of electrodes included in a cell may be increased without unduly increasing the thickness of the groups of electrode tabs. Consequently, the risk of electrode tab degradation (e.g., deformation, melting, etc.,) caused by increased intensity welding may be reduced. In this way, a higher power cell with increased durability may be achieved, if desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an example of a prior art electrochemical cell. 
         FIGS. 2A and 2B  show, respectively, cathodes and anodes in a battery cell system. 
         FIG. 3  shows coated sheet material of the anode in the battery cell system. 
         FIG. 4  shows coated sheet material of the cathode in the battery cell system. 
         FIG. 5  shows an electrode stack with interleaved tabs in the battery cell system. 
         FIG. 6  shows an electrode stack with trimmed tabs for welding in the battery cell system. 
         FIG. 7  shows an electrode stack with welded extension tabs in the battery cell system. 
         FIG. 8  shows an electrode stack with a top frame in the battery cell system. 
         FIG. 9  shows a structural frame with a stack assembly in the battery cell system. 
         FIG. 10  shows an electrode stack with a structural frame in the battery cell system. 
         FIG. 11  shows a structural frame sidewall designed for strain relief in the battery cell system. 
         FIG. 12  shows a protective housing surrounding an electrode stack in the battery cell system. 
         FIGS. 13A and 13B  show different views of the protective housing in the battery cell system. 
         FIG. 14  shows another view of the protective housing in the battery cell system. 
         FIG. 15  shows a welded electrode stack in the battery cell system. 
         FIG. 16  shows a pouch top with a filling or ventilation port in the battery cell system. 
         FIG. 17  shows a rupture disc vent installed in the filling or ventilation port in the battery cell system. 
         FIG. 18  shows an example of an electrode stack pattern in a battery cell system. 
         FIG. 19  shows layers of a laminate pouch in a battery cell system. 
         FIG. 20  shows a method for manufacturing a battery cell system. 
         FIGS. 2A-17  are drawn to scale, although other relative dimensions may be used, if desired. 
     
    
    
     DETAILED DESCRIPTION 
     The following description relates to a battery cell system with a stacked electrochemical cell battery (e.g., stacked prismatic electrochemical cell battery) and a method for manufacturing the battery cell system. It will be appreciated that  FIGS. 2A-20  may be discussed collectively.  FIGS. 2A-15  show different stages of assembly of a battery cell system  550 .  FIGS. 16-17  show example configurations of a protective housing in the battery cell system.  FIG. 18  shows an example of layers an electrode stack that may be included in the battery cell system.  FIG. 19  shows an example of layers in a protective housing in the battery cell system.  FIG. 20  shows a method for manufacturing a battery cell system. Furthermore, axes X, Y and Z are provided for references in  FIGS. 2A-17 . In one example, the Z-axis may be parallel to a gravitational axis and therefore may be referred to as a vertical axis. Additionally, the Y-axis may be a lateral axis and the X-axis may be a longitudinal axis. However, the axes may have alternate orientations, in other examples. 
     The stacked cell battery described herein is an improvement upon  FIG. 1  (prior art). Prior art  FIG. 1  shows an example of an electrode stack  100  having a plurality of anode foil tabs  102  and cathode foil tabs  104 . As shown in  FIG. 1  the anode foil tabs  102  are laterally aligned with one another. The cathode foil tabs are likewise laterally aligned with one another. 
     In the description herein, an anode is a positive electrode and a cathode is a negative electrode. It will be appreciated that a negative electrode is an electrode through which conventional current leaves the device and a positive electrode is an electrode through which conventional current enters the device. As such, the anodes and cathodes may be generally referred to as electrodes, in some examples. 
       FIG. 3  shows an example anode  300  that may be included in an electrode stack, such as electrode stack  500  shown in  FIG. 5 . The anode  300  may comprise an anode coating  302 , coated onto both sides of an anode electrode sheet  306  designed to collect current. The anode electrode sheet  306  may comprise a metallic foil substrate, and the coating  302  may comprise an electrochemically active anode material (e.g., electro-active Lithium intercalation material) such as a mixture of natural and artificial graphite or Lithium-titanate, or metallic Lithium. Thus, the anode  300  may comprise a metallic foil substrate (e.g., anode electrode sheet  306 ) that is partially or wholly covered with the coating  302 . The coating  302  may be applied over a specific portion of the anode electrode sheet  306 , such as over a specific width of the anode electrode sheet  306 , but not all of the anode electrode sheet  306 , such that at least a portion of the anode electrode sheet  306  may remain uncoated. Thus, the anode  300  may comprise a coated section  304  which contains the coating  302 , and an uncoated section  308  that comprises the anode electrode sheet  306  and protrudes from the coated section  304 . The coated sheet material may then be slit along alternating edges of the coated sections, resulting in a continuous electrode material with exposed uncoated foil extended a specific width from the coated area on one edge of the electrode. 
       FIG. 4  shows an example cathode  400  that may be included in the electrode stack  500 , shown in  FIG. 5 . Cathode  400  may also be referred to as positive electrode  400 , in some examples. In one example, the cathode  400  may be similar in size and configuration to anode  300  (it may comprise similar dimensions and may be partially covered with a coating). However, in other examples, the cathode  400  may have a different size, shape, etc., than the anode. Furthermore, the cathode  400  is comprised of different materials than the anode  300 . In particular, the cathode  400  may include a mixture of specially prepared Lithiated Iron-Phosphate powder or Lithiated Metal-oxide powder, conductive carbon and polymeric binder. Specifically, the cathode  400  may comprise a cathode electrode sheet  406  coated in a cathode coating  402 . The cathode electrode sheet  406  may also comprise a metallic foil current collector substrate, similar to the anode electrode sheet  306  of the anode  300 , but the coating  402  may comprise the different mixture of specially prepared powder. In particular, the cathode coating  402  may comprise an electrochemically active cathode material such as the mixture of specially prepared Lithiated Iron-Phosphate powder or Lithiated Metal-oxide powder, conductive carbon and polymeric binder referenced above. Thus, the cathode  400  may be prepared in a similar fashion as the anode  300 , except that the coatings of the anode and cathode are different. Similar to the coating on anode  300 , the coating  402  may be applied over a specific portion of the electrode sheet  406 , such as over a specific width of the electrode sheet  406 , but not all of the sheet  406 , such that at least a portion of the sheet  406  may remain uncoated. Thus, the cathode  400  may comprise a coated section  404  that contains the coating  402 , and an uncoated section  408  that comprises the electrode sheet  406 . The coated sheet material may then be slit along alternating edges of the coated sections, resulting in a continuous electrode material with exposed uncoated foil extended a specific width from the coated area on one edge of the electrode. 
     Thus, an uncoated portion of the electrode sheets  306  and  406  may extend beyond and protrudes from the coatings  302  and  402 . As discussed in greater detail herein, the protruding portions of the electrode sheets  306  and  406  may be trimmed down to narrower tabs. After trimming, these narrowed, cut uncoated electrode areas may be referred to as electrode tabs (as will be described in greater detail herein). Thus, the trimmed electrode sheets  306  and  406  may be referred to as electrode tabs  212 ,  216 ,  220 , and  224 . 
     Thus, the continuous rolls of coated, calendered, and slit electrodes  300  and  400 , may be stamped to desired dimensions using a normal stamping process, such as a steel ruled die or a close clearance-stamping die. The stamped electrode shape may also be created by laser cutting. In the prior art prismatic cells, each of the first and second electrodes would have identical foil tabs remaining after stamping (see  FIG. 1 ), such that when stacked into a cell electrode stack, the individual foil tabs  102  of the first electrode would all align in a single position relative to one corner of the electrode stack. All the stamped foil tabs  104  of the second electrode would likewise all align together at a different single position relative to the electrode stack corner. 
     Referring now to  FIGS. 2A and 2B , as an improvement over the above-mentioned prior art, the presently disclosed battery cell system. The continuous rolls of coated calendered and slit electrode materials are stamped to desired dimension using stamping techniques, but each of the cathodes and anodes,  300  and  400  respectively, are stamped into two different electrode dimensions, differing in the position of the remaining foil tab, resulting in two different stamped cathodes  202  and  204  and two different stamped anodes  206  and  208 . The stamped, cathodes  202  and  204  may comprise electrode tabs  212  and  216 , respectively. Thus, first cathode  202  may comprise a first cathode tab  212 , and the second cathode  204  may comprise a second cathode tab  216 . Similarly, the first anode  206  may comprise a first anode tab  220  and the second anode  208  may comprise a second anode tab  224 . As described in greater detail herein, the cathodes  202  and  204  and the anodes  206  and  208  may be stacked to form an electrode stack (e.g., the electrode stack  500  shown in  FIG. 5 ). In particular, up to 150 of the electrodes (e.g., cathodes  202  and  204  and/or anodes  206  and  208 ) may be stacked together to form the electrode stack. When stacked, the electrodes may be aligned with one another such that the ends of the electrodes are aligned. Thus, first ends  201 ,  205 ,  211 , and  215  of the electrodes  202 ,  204 ,  206 , and  208  may be aligned, and second ends  204 ,  207 ,  213 , and  217  may be aligned. However, the tabs  212 ,  216 ,  220 , and  224  may be laterally offset from one another when the electrodes are stacked, and thus, the tabs  212 ,  216 ,  220 , and  224  may not overlap with one another. 
     As described above, the cathode tabs  212  and  216  may extend from the cathode electrode sheet  406  that has been cut down to the example dimensions shown in  FIG. 2A . Thus, the cathode tabs  212  and  216  may have a similar (e.g., equivalent) composition, and may have a similar (e.g., equivalent) size, shape, and/or geometry, except that they are laterally offset from one another when the cathodes  202  and  204  are aligned with one another. Said another way, the protruding electrode sheet  306  of the cathodes  202  and  204  may be cut differently, such that their resulting cathode tabs,  212  and  216  respectively, are offset from one another, and do not overlap when stacked as shown in  FIG. 5 . The cathodes  202  and  204  may be aligned with another when stacked in the electrode stack (e.g., electrode stack  500  shown in  FIG. 5 ) by aligning first ends  201  and  205  of the cathodes  202  and  204 , respectively. As shown in the example of  FIG. 2A , the tabs  212  and  216  may be positioned closer to the first ends  201  and  205  of the cathodes  202  and  204 , respectively, than the second ends  203  and  207 . Offsetting groups of anode tabs as well as cathode tabs allows the thickness of the tab stacks to be reduced when compared to previous cell stacks in which the electrode tabs of like charge are aligned. Reducing the thickness of the tab stack allows the energy used to weld the tab stacks to be reduced, in turn. As a result, the likelihood of cell stack degradation (e.g., unwanted deformation, melting, etc.,) caused by increased welding intensity may be reduced, if desired. As a result, the size of the battery system may be increased without unduly increasing the thickness of the tab stacks above an undesirable value. 
     Thus, cathode tab  212  may be spaced away from the first end  201  of the cathode  202  by a distance defined by a first tab offset  210 . Similarly, the cathode tab  216  may be spaced away from a first end  205  of the cathode  204  by a distance defined by a second tab offset  214 . However, the second tab offset  214  may be greater (e.g., a greater distance) than the first tab offset  210 . In this way, the tab  216  of the cathode  204  may be spaced a greater distance away from the first end  205  of the cathode  204 , than the cathode tab  212  of the cathode  202  that is spaced from the first end  201  of the cathode  202 . In particular, the second tab offset may be sized such that the tab  216  does not overlap any of the cathode tab  212  when the cathodes  202  and  204  are aligned with one another by aligning their first ends  201  and  205 , and second ends  203  and  207  with one another. 
       FIG. 2B  shows a similar electrode tab spacing to the cathode tab spacing shown in  FIG. 2A , except that  FIG. 2B  shows the electrode tab spacing for the anodes  206  and  208 . Thus, anode tabs  220  and  224  of the anodes  206  and  208 , respectively may have a similar (e.g., equivalent) size, shape, and/or geometry as the cathode tabs  212  and  216 , except that unlike the tabs  212  and  216  of the cathodes  202  and  204 , the anode tabs  220  and  224  of the anodes  206  and  208  may be spaced closer to the second ends  213  and  217  of the anodes  206  and  208  than first ends  211  and  215 . 
     Thus, electrode tab  220  may be spaced away from the second end  213  of the anode  206  by a distance defined by a first tab offset  218 . Similarly, the anode tab  224  may be spaced away from a second end  217  of the anode  208  by a distance defined by a second tab offset  222 . However, the second tab offset  222  may be greater than the first tab offset  218 . In this way, the tab  224  of anode  208  may be spaced a greater distance away from the second end  217  of the anode  208 , than the tab  220  of the anode  206  is spaced from the second end  213  of the anode  206 . In particular, the second tab offset  222  may be sized such that the tab  224  does not overlap any of the tab  220  when the anodes  206  and  208  are aligned with one another by aligning their first ends  211  and  215 , and second ends  213  and  217  with one another. 
     When the tabs are offset, lateral sides  250  of the offset tabs are spaced away from one another such that they are laterally separated. Furthermore, the top sides  252  of the tabs shown in  FIGS. 2A and 2B  have a similar height. However, in other examples, the top sides  252  of the tabs may have non-equivalent heights. Furthermore, in other examples, the first group of anode tabs may be offset from the second group of anode tabs by a different amount than the offset between the groups of cathode tabs. 
     During the electrode stacking process the two different cathodes  202  and  204  and two different anodes  206  and  208  may be alternatively stacked and may be separated by insulating porous separator material. The lateral offset between the stamped tabs of the same polarity electrodes is determined from the sum of the tolerances for stamping width and position and the stacking position tolerance of each electrode, such that a small gap may be maintained between the electrode tabs of each type. 
     Referring now to  FIG. 5 , it shows the battery cell system  550  including the electrode stack  500  and the structural frame  501 . The battery cell system  550  may also include a protective housing such as the laminate pouch  1200 , shown in  FIG. 12  and discussed in greater detail herein.  FIG. 5  also shows the cathodes  202  and  204  and the anodes  206  and  208  forming an electrode stack  500 . Although the electrode stack  500  may include the first and the second cathodes  202  and  204 , respectively, and/or the first and the second anodes  206  and  208 , respectively, in one example. It will be appreciated that in other examples, the electrode stack  500  may include more than two anodes and/or cathodes. 
     The electrodes may be held in place by a structural frame  501 . Thus, when stacked, the tabs  212 ,  216 ,  220 , and  224  of the electrodes  202 ,  204 ,  206 , and  208  may form four distinct groups of tabs, each of the groups comprising the same type of electrode. However, in some examples, the foil tabs may be rearranged to any desirable order. Thus, a first electrode tab group  502  may comprise the tab  212  of the first cathode  202 , the second electrode tab group  504  may comprise the tab  216  of the second cathode  204 , the third electrode tab group  506  may comprise the tab  220  of the first anode  206 , and the fourth electrode tab group  508  may comprise the tab  224  of the second anode  208 . Each of the groups  502 ,  504 ,  506 , and  508  may comprise a plurality of the respective type of electrode tab, in some examples. Further, in some examples, each of the groups may comprise the same number of electrode tabs. However, in other examples, the groups may comprise different numbers of electrode tabs. For instance, up to 150 electrodes may be stacked in the electrode stack  500 . However, since the stack includes two different cathode tab groups offset from one another and two different anode tab groups offset from another, the number of tabs in each of the groups may be reduced when compared to approaches where all of the cathode tabs are aligned with one another and all of the anode tabs are aligned with one another. 
     In further examples, more than two offset anode and/or cathode tabs may be used in the electrode stack. Thus, more than two offset groups of positive and more than two offset groups of negative electrodes may be used in the electrode stack. By increasing the number of offset tabs that are utilized in the electrode stack, the number of electrodes that may be included in the stack may be increased. 
     Assembling the electrode stack  500 , may include utilizing a specialized stacking machine, in one example. The specialized stacking machine includes a continuous sheet of porous separator material that is ‘Z’ folded around the alternating stacked electrodes (e.g., cathodes and anodes), resulting in a rectangular or prismatic shape electrode stack  500  of alternating cathodes and anodes with four distinct groups of foil tabs extending beyond the edges of the separator on a single edge of the stack or from opposing sides of the electrode stack. As an example, electrode stack  500  may be wrapped in porous separator material after Z-wrapping the alternating electrodes. The porous separator material allows the anodes and the cathodes to be separated to reduce the likelihood of unwanted interaction (e.g., short circuit) between the anodes and cathodes while allowing the transportation of ionic charge carriers. It will be appreciated that other manufacturing techniques for the electrode stack  500  have been contemplated. 
     After stacking, as shown in  FIG. 5 , the tabs of the tab groups  502 ,  504 ,  506 , and  508 , may be trimmed, shaped, bent, folded, etc., to a desired shape (e.g., a final shape), an example of which is shown in  FIG. 6 .  FIG. 6 , shows the electrode stack  500  after removal from the stacking machine, where the electrode stack  500  is placed in the structural frame  501  (e.g., holding fixture) and the extending tab groups  502 ,  504 ,  506 , and  508  are shaped and trimmed to a desired shape (e.g., final shape) and dimension they may have after welding of a cell extension tab. As shown in  FIG. 6 , the trimmed and shaped tab groups may be referred to herein as shaped tab groups  602 ,  604 ,  606 , and  608 . Thus, the tab groups  602 ,  604 ,  606 , and  608 , are the tab groups  502 ,  504 ,  506 ,  508  that have been trimmed and shaped to a desired shape prior to welding. The negative electrode groups  602  and  604  including the negative electrode tabs may be referred to collectively as the cathode tabs  612 , and the positive electrode groups  606  and  608  may be referred to collectively as the anode tabs  614 . In some cases, a small ultrasonic pre-weld may be employed to hold the tabs in the desired shape for consolidation and extension tab welding. 
     As shown in  FIG. 6 , the tab groups  502 ,  504 ,  506 , and  508  may be trimmed such that the resulting tabs  612  and  614  may include vertical welding surfaces  603  and  605 , respectively, which may be welded directly to extension tabs as shown and described in greater detail herein with reference to  FIG. 7 . 
       FIG. 6  also shows a front side  650 , a backside  652 , a top side  654 , a bottom side  656 , a first lateral side  658 , and a second lateral side  660  of the battery cell system  550 . The structural frame  501  may partially enclose the electrode stack  500 . Specifically, the structural frame  501  extends down the front side  650 , the backside  652 , the first lateral side  658 , and the second lateral side  660  of the system. In this way, the structural frame  501  may provide structural reinforcement to the battery cell system  550 . 
     Turning to  FIG. 18 , a general stacking sequence for forming an electrode stack  1800  in a battery cell system  1850 , is illustrated. The battery cell system  1850  may be an example of the battery cell system  550 , shown in  FIGS. 2A-17 . The electrode stack  1800  may be arranged according to the following the pattern: separator material  1802 /first electrode  1804 /separator material  1802 /second electrode  1806 /separator material  1802 /third electrode  1808 /separator material  1802 /fourth electrode  1810  and so one and so forth. In this non-limiting example, elements  1804 ,  1806 ,  1808 , and  1810  may correspond to any of the first and second positive and negative electrodes shown in  FIGS. 2A and 2B . However, other stacking sequences have been contemplated. Furthermore, it will be appreciated that the cell stacking pattern shown in  FIG. 18  may be repeated as many times as desired. In some examples, the pattern may be repeated between 20 and 60 times. As an example, indicated by the bottom-most separator material  1802  (bottom and top distinguished by arrow adjacent to electrode stack), the stack may be started at the top with a layer of separator material and ended at the bottom with a lower (e.g., final) layer of separator material. 
     As an example, with reference to  FIG. 18 , a stacking sequence which may be repetitively employed is: separator/first anode/separator/first cathode/separator/second anode/separator/second cathode. However, as mentioned above other stacking sequence may be employed. Additionally, as an example, one or more stacking sequences may be used throughout the stack. As a further example, after stacking and repeating the stacking sequence or sequences a number of times, a layer of separator material may be used such that the stack begins and ends with layers of separator material. As a further example, after stacking, the trailing edge of separator may be taped in place to maintain its position during subsequent cell manufacturing steps. 
     Referring now to  FIG. 7 , after tab shaping and trimming each pair of at least two tab groups (for example,  612  and  614  of  FIG. 6 ) may be welded to a first extension tab  702  and second extension tab  704 , the width of the first and second extension tabs may be at least equal to twice the electrode tab width plus the gap between the two tab groups,  612  and  614 , in one example. Two separate ultrasonic welds are employed to consolidate the two electrode tab groups to the single extension tab. The two welds may be accomplished simultaneously with a single welding horn, in one instance. This welding may be performed separately on both the two groups of anode tabs and on the anode extension tab and also on the two groups of cathode tabs and on the cathode extension tab. As an example, the two groups of anode tabs  614  may be welded to an anode extension tab  704 , and the two groups of cathode tabs  612  may be welded to a cathode extension tab  702 . The extension tabs  702  and  704  allow different groups of offset tabs to be electronically coupled. 
     In some examples, the tabs  612  and  614  may be sandwiched between the extension tabs  702  and  704 , and electrode tab supports  706 , and  708 , respectively. However, in other examples, the tabs may be directly welded to the extension tabs without the electrode tab supports. In other examples, the respective tab groups  602  and  604 , shown in  FIG. 6 , and then the tab groups  606  and  608 , shown in  FIG. 6 , may be welded to extension tabs  702  and  704 , shown in  FIG. 7 . Such a process may be used to consolidate the tab groups before adding the tab supports  706  and  708  and may provide a more robust electrode assembly. 
     The electrode tab supports  706  and  708  increase the structural integrity of the tab assembly thereby reducing the likelihood of tab damage occurring during battery use and/or manufacturing. As a result, the durability of the battery cell system is increased. The electrode tab supports  706  and  708  each include a slit  710  and  712 , respectively, through which the extension tabs  702  and  704  may extend, in the illustrated example. However, other electrode tab support profiles have been contemplated. Additionally, in one example, the electrode tab supports  706  and/or  708  may include an electrically insulating polymeric material  714 . The electrically insulating polymeric material  714  may be designed to provide electrical isolation between the extension tabs  702  and  704  and components such as a protective housing, described in greater detail herein. Further, in some examples, the electrode tab supports  706  and  708  may be integrally formed with the protective housing or are directly physically coupled to the protective housing. 
     Additionally, in one example, the cathode tabs  612  may include an aluminum material and the anode tabs  614  may include a nickel plated copper material. However, additional or alternative material may be included in the anode and/or cathode tabs, in other examples. 
     Referring now to  FIG. 8 , after welding of the extension tabs, a structural frame  501  containing the electrode stack is assembled. In one example, in a cell configuration having both positive and negative tabs on a single cell face, there may only be a single molded frame assembly on that face. In another example, if the tabs extend from opposing sides of the electrode stack, then two molded frame assemblies may be used. The structural frame  501  may include at least one support  804  (e.g., polymer support). In the illustrated example, the support  804  has a substantially triangular cross section with chamfered edges, to match the resulting shape of the laminate pouch packaging. However, other profiles of the support  804  have been contemplated. Additionally, the support  804  includes two slots  805  and  807  sized to allow the extension tabs  702  and  704  to pass through the central region of the support. The structural frame  501  may be fabricated in two matching halves which are then assembled onto the tabbed side of the cell by snap fitting or press fitting the two molded frame halves together, in one example. Furthermore, the support  804  may be injection molded, in one example. Additionally, the support  804  has a triangular cross-section in a Z-Y plane, in the illustrated example. Thus, the support  804  may taper in the vertical direction. However, other shapes of the support  804  have been contemplated and may be used, in other examples. For instance, the support  804  may have rectangular cross-section or the support may include curved (e.g., convex or concave) sections. Furthermore, the support  804  may be attached (e.g., welded, adhesively bonded, mechanically coupled, combinations thereof, etc.,) to a base  806  of the structural frame  501 . 
     Referring next to  FIG. 9 , it shows the structural frame  501  (e.g., internal box) assembled and providing mechanical separation of the tabs and electrode stack from the internal surfaces of the laminate pouch packaging material, thereby protecting the pouch from mechanical damage and loss of electrical isolation due to impact, vibration or shock during handling or subsequent environmental exposure in the battery application environment. The structural frame may be fabricated in two separate halves,  904  and  906 , by injection molding and may be assembled onto the welded electrode stack by press fitting or snap fitting. Additionally, a further enhancement of the structural frame may include a reduced thickness area  908  on one face  909  of the structural frame  501 , thereby creating a recessed groove to provide mechanical relief to a heat sealed seam of the laminate pouch which may be applied in the next assembly step. In one example, the structural frame  501  may be injection molded. However, other frame manufacturing techniques have been contemplated. 
     Structural frame  501  may then be packaged and/or vacuum sealed within a protective housing. In one example, the protective housing may be a laminate pouch, such as the laminate pouch  1200  shown in  FIG. 12 , with an internal protective structure with a recessed seam relief groove, as described above. However, other types of protective housing have been contemplated, such as a housing that has a greater rigidity. 
     An example of a laminate pouch  1900  is shown in  FIG. 19 . It will be appreciated that the laminate pouch  1900  is an example of the previously described laminate pouch  1200  included in the cell battery system  550 . The laminate pouch  1900 , shown in  FIG. 19 , may include at least two layers and, in some examples, four functional layers to create a heat sealable laminate with at least one metallic layer which reduces (e.g., prevents) moisture ingress into the finished electrochemical cell, having a non-aqueous electrolyte. The inner most layer  1902  may be a heat sealable polyolefin, such a polypropylene, bonded to an aluminum layer  1904  which may be bonded to another polymer layer  1906  (e.g., a nylon layer) which in turn may be bonded to the external layer  1908  (e.g., a polyethylene terephthalate (PET) layer). As an example, the layers  1902 ,  1904 ,  1906 , and  1908  may be rearranged as desired based on end-use design goals. The laminate pouch  1900  may be included in a battery cell system  1950 . It will be appreciated that the battery cell system  1950  may be an example of the battery cell system  550 , shown in  FIGS. 2A-18 . The laminate pouch  1900  may include one or more walls that accommodate expansion during electrolyte activation, in one example. Further, in such an example, the walls of the laminate pouch may be substantially flat after electrolyte activation and bent inward prior to electrolyte activation. In this way, the pouch may accommodate expansion to reduce the likelihood of pouch and/or cell damage. 
     Turning now to  FIG. 10 , as a further example, assembling the battery cell system  550  may optionally include first assembling the structural frame  501  around the exterior of the welded electrode stack assembly in order to protect the electrode stack edges from mechanical damage during assembly and use as well as to protect the electrode stack edges from external pressure (e.g., a pressure of at least 14.6 pounds per square inch (psi)) created when the cell assembly is vacuum sealed. The internal frame may include at least a protective frame placed around the welded tab area of the electrode stack. The top side of the structural frame may have a substantially triangular cross sectional shape and tapered edges  1002 ,  1004  at the ends to match with the shape of the folded pouch laminate packaging. Optionally the structural frame  501  may be extended to prevent the edges and corners of the electrode stack from making direct contact with the internal surface of the pouch laminate material, thereby preventing loss of internal electrical isolation by mechanical damage to the inner heat sealable polymer layer and exposing the Aluminum layer to electrical contact with the electrochemically active electrodes. 
     In one example, the internal structural frame may be fabricated in two matching halves with a flexible gap between each frame half, shown in  FIGS. 9 and 10 . The reduced thickness area  908  of the structural frame  501  allows the finished cell and electrode stack to be compressed in the normal thickness direction during the cell&#39;s electrochemical activation, formation and degassing processes. This compression being applied as a means to eliminate gas bubbles between the electrode and separator surfaces which form as a byproduct of the cell&#39;s electrochemical formation processes, such as anode SEI formation, reaction with residual moisture in the cell and/or other parasitic chemical reactions which generate gaseous byproducts. The flexible gap further allows the cell thickness to increase/decrease during cell charging and discharging due to electrode swelling caused by the changing state of charge. The structural frame (e.g., internal fabricated support frame) may be fabricated by injection molding a chemically compatible polymer such as polypropylene, polyethylene, polybutylene terephthalate (PBT), and/or polyethylene terephthalate (PET), for example. 
     Turning now to  FIG. 11 , as an example, in order to accommodate electrode stack swelling during cell electrolyte activation, formation, and use, the vertical side walls  1104  of the structural frame  501  and/or protective housing, discussed in greater detail herein, may be tapered inward toward the center-line  1110  of the cell, allowing extra material to accommodate cell expansion and retraction. The extra material reduces the likelihood of wrinkling and cracking in the battery cell system. As the cell swells, indicated at  1106 , during the normal cycling of the battery, the extra material may provide strain relief so as not to damage the central seam. The electrode stack and frame assembly may then be packaged within the laminate pouch. As a further example, the above-mentioned feature of tapered-inward sides of the structural frame  501  may be used in order to relieve pressure on other edges or faces of the battery. Thus, other edges or faces of the battery may have tapered-inward sides. 
     Turning to  FIG. 12 , the battery cell system includes a protective housing in the form of a laminate pouch  1200 , in the illustrated example. However, as previously discussed other suitable types of protective housings have been contemplated. 
     As shown in  FIG. 12 , the laminate pouch  1200  may be formed into a rectangular cross sectional shape and one section (e.g., end) may be folded and heat sealed. As such, a heat seam  1202  extends (e.g., vertically extends) down the laminate pouch, in the illustrated example. In this way, a closed end of the laminate pouch may be formed. Furthermore, the heat seam  1202  may be aligned with the reduced thickness area  908  in the structural frame  501 , shown in  FIG. 10 . In this way, the heat seam  1202  may be mated with the reduced thickness area  908 , in one example. However, it will be appreciated that the heat seam  1202  may be positioned in other locations, in other examples. 
     Additionally, a solid rectangular sizing fixture  1206 , having the same dimensions as the electrode stack, may be placed inside the laminate pouch to maintain a desired rectangular shape while one end may be folded and heat sealed, in some examples. 
     One example of an assembly sequence for a laminate pouch may be as follows: the laminate pouch material may be taken from a continuous roll and first rolled into tubular form with an overlapping section of 2 to 20 mm wide. As an example, the overlapping section may be 10 mm wide. The overlapping section may be heat sealed using flat heating bars and folded flat with respect to the unsealed surface. 
     The pouch folding may include, in one example, displacing a triangular shaped area on each of the two narrow sides of the pouch while compressing the long faces of the pouch perpendicular direction with respect to the pouch&#39;s narrow side walls. Additionally, the pouch  1200  may be selectively heat sealed along a narrow width adjacent to the sidewall edges of the pouch package. The center area may be left unsealed at this step to allow electrolyte filling during future assembly steps, in some examples. 
     Turning now to  FIGS. 13A and 13B , after folding and heat sealing the bottom closed end of the laminate pouch  1200 , the rectangular sizing fixture  1206  may be removed and the electrode stack and molded plastic frame assembly may be inserted with tabs facing away from the closed end of the pouch package. The corner triangular folds may be accomplished in similar fashion as were the bottom closed end triangular folds. The top open end may be compressed and the pouch may be heat sealed both to the electrode tab supports  706  and  708  and to the opposing face of the pouch, creating a seal at the top tab end of the cell. A fill port may also be incorporated into this concept. This feature can be integrated with the injection molded protective frame or as a separate part fused to the pouch material or frame. The surrounding area of the structural frame may be heat sealed to the internal polymer layer of the pouch, creating a leak tight seal. Additionally, an untrimmed end  1306  of the laminate pouch  1200  may be employed for cell filling and gas formation collection. 
       FIG. 14  shows an additional view of the laminate pouch  1200  with the additional untrimmed end  1306  of laminate pouch. 
       FIG. 15  shows an alternate view of the electrode welded stack before the addition of the structural frame or the addition of a protective housing (e.g., laminate pouch) before a structural frame or sizing fixture has been added. 
     Turning now to  FIG. 16 , a port  1602  (e.g., fill port) in the laminate pouch  1200  may be molded with internal or external threads and used for electrolyte filling and/or degassing of the cell during the formation process, thereby reducing the quantity of pouch material used in manufacturing in comparison to the current formation process. In some instances, incorporation of the filling/degassing port may reduce the amount of pouch material used for forming of the battery cell by 40% (compared to forming the battery cell without a filling/degassing port). The current formation process uses an integral gas volume formed with extra length of pouch material, creating an extra internal void volume to accommodate gasses generated during the initial cell formation process. 
     Turning to  FIG. 17 , the above-mentioned fill port may incorporate a vent/rupture disc  1702  in the laminate pouch  1200  which may help to manage pressure relief, thereby providing controlled venting under operating conditions or extreme conditions in which the cell has been run or handled outside normal operating conditions (e.g., physical damage to battery, exposure to extreme heat etc.). 
     With reference to  FIG. 17 , after formation, the cell may be vacuum degassed and sealed. In the current process the extra pouch material may be trimmed off during a vacuum sealing step and discarded. The cell may be vacuum degassed through the integrated fill port during this degassing step. After degassing the fill port may be sealed by several methods, such as a heat sealed plug or threaded plug. As an example, further enhancement to cell safety under abusive conditions may be made and a pressure relief vent is installed in the fill port sealing plug. The fill port may have a vent cap plug that will rupture or open at a specified pressure to control the rate of gas ejection from the cell, decreasing the probability of explosion or fire during exposure to abusive conditions. Adding a plug or disc may in some instances incorporate the sealing methods mentioned above, not limited to heat sealing or threading. As an example, controlled venting may also incorporate a scored or coined slit on the pouch to rupture before heat seal failure. As an example, scoring or slitting the pouch may be added to any desirable location on the pouch. 
     It should be understood that the figures show example configurations with relative positioning of the various components. If shown directly contacting each other, or directly coupled, then such elements may be referred to as directly contacting or directly coupled, respectively, at least in one example. Similarly, elements shown contiguous or adjacent to one another may be contiguous or adjacent to each other, respectively, at least in one example. As an example, components laying in face-sharing contact with each other may be referred to as in face-sharing contact. As another example, elements positioned apart from each other with only a space there-between and no other components may be referred to as such, in at least one example. As yet another example, elements shown above/below one another, at opposite sides to one another, or to the left/right of one another may be referred to as such, relative to one another. Further, as shown in the figures, a topmost element or point of element may be referred to as a “top” of the component and a bottommost element or point of the element may be referred to as a “bottom” of the component, in at least one example. As used herein, top/bottom, upper/lower, above/below, may be relative to a vertical axis of the figures and used to describe positioning of elements of the figures relative to one another. As such, elements shown above other elements are positioned vertically above the other elements, in one example. As yet another example, shapes of the elements depicted within the figures may be referred to as having those shapes (e.g., such as being circular, straight, planar, curved, rounded, chamfered, angled, or the like). Further, elements shown intersecting one another may be referred to as intersecting elements or intersecting one another, in at least one example. Further still, an element shown within another element or shown outside of another element may be referred as such, in one example. 
       FIG. 20  shows a method  2000  for manufacturing a battery cell system. The method  2000  may be used to manufacture the battery cell systems described above with regard to  FIGS. 2A-19 . However, in other examples, the method may be used to manufacture other suitable battery cell systems. Furthermore, the method  2000  may be stored as instructions in memory (e.g., non-transitory memory) executable by a processor. 
     At  2001  the method includes forming an electrode stack with offset anode tabs and offset cathode tabs. It will be appreciated that the electrode stack may include alternating cathodes and anodes with separator sheets positioned there between, in some examples. Specifically, the anodes and cathodes may be formed in an electrode stack with the following stacking sequence; a first anode, a first layer of porous separator material, a first cathode, a second layer of porous separator material, etc. Forming the electrode stack may include steps  2002 - 2004 . 
     At  2002  the method includes forming a plurality of anodes with a plurality of anode tabs, where the plurality of anode tabs include a first group of anode tabs laterally offset from a second group of anode tabs. 
     Next at  2004  the method includes forming a plurality of cathodes with a plurality of cathode tabs, where the plurality of cathode tabs include a first group of cathode tabs laterally offset from a second group of cathode tabs. Laterally offsetting groups of cathode tabs as well as groups of anode tabs allows the thickness of the tabs to be reduced when compared to cell stack with aligned tabs. Therefore, welding energy needed to weld the groups of tabs may be reduced. Consequently, the likelihood of degradation (e.g., melting, deformation, etc.,) of the electrode tabs (e.g., anode and cathode tabs) during welding is reduced. 
     At  2006  the method includes welding a first extension tab to the first group of anode tabs and the second group of anode tabs. Next at  2008  the method includes welding a second extension tab to the first group of cathode tabs and the second group of cathode tabs. 
     Additionally, in some examples, the method may include steps  2010 ,  2012 ,  2014 , and/or  2016 . At  2010  the method includes attaching a first electrode tab support to the first group of anode tabs and the second group of anode tabs and at  2012  the method includes attaching a second electrode tab support to the first group of cathode tabs and the second group of cathode tabs. 
     At  2014  the method includes placing the electrode stack in a structural frame. The structural frame may at least partially surround the electrode stack. Further, in one example, the structural frame may include openings allowing the first and second support tabs to extend there through. Additionally, the structural frame may be molded from a polymeric material, in one example. 
     At  2016  the method includes placing the structural frame and the electrode stack within a protective housing. In one example, the protective housing may be a laminate pouch and therefore, the method may include in such an example, folding a laminate pouch around the electrode stack and the support frame and heat sealing the laminate pouch. In one example, subsequent to folding and heat sealing the laminate pouch, the pouch may be degassed via a degas port. After degassing the degas port may be sealed. In this way, unwanted gas may be removed from the system, thereby reducing the size of the protective housing. Consequently, the compactness of the battery cell system may be increased. 
     The invention will further be described in the following paragraphs. In one aspect, a battery cell system is provided that includes an electrode stack including a first anode with a first anode tab, a second anode with a second anode tab laterally offset from the first anode tab, a first cathode with a first cathode tab, and a second cathode with a second cathode tab laterally offset from the first cathode tab. 
     In another aspect, a method for manufacturing a battery cell system is provided. The method includes forming a plurality of anodes with a plurality of anode tabs, where the plurality of anode tabs include a first group of anode tabs laterally offset from a second group of anode tabs, forming a plurality of cathodes with a plurality of cathode tabs, where the plurality of cathode tabs include a first group of cathode tabs laterally offset from a second group of cathode tabs, welding a first extension tab to the first group of anode tabs and the second group of anode tabs, and welding a second extension tab to the first group of cathode tabs and the second group of cathode tabs. In one example, the method may further include attaching a first electrode tab support to the first group of anode tabs and the second group of anode tabs and attaching a second electrode tab support to the first group of cathode tabs and the second group of cathode tabs. In another example, the method may further include placing the plurality of cathodes and anodes in at least one of a structural frame and a protective housing at least partially surrounding the plurality of cathodes and anodes. 
     In another aspect, an electrochemical cell is provided that comprises a plurality of first negative electrodes comprising first negative electrode tabs, a plurality of second negative electrode comprising second negative electrode tabs, wherein the second negative electrode tabs are offset from the first negative electrode tabs, a plurality of first positive electrodes comprising first positive electrode tabs, and a plurality of second positive electrodes comprising second positive electrode tabs. 
     In another aspect, an electrochemical cell is provided that includes a first positive electrode and a second positive electrode forming a positive electrode group, and a first negative electrode and a second negative electrode forming a negative electrode group, wherein each electrode is separated by a layer of porous separator material, and each electrode has a tab width and offset such that no tabs of different electrodes overlap and, the at least two electrodes of the positive electrode group are welded together and the at least two electrodes of the negative electrode group are welded together. 
     In another aspect, an internal frame for an electrochemical cell is provided that includes an electrode tab support, the electrode tab support comprising two slots for receiving an anode and a cathode of the electrochemical cell, wherein the electrode tab support prevents lateral movement of the anode and cathode. 
     In another aspect, an electrochemical cell is provided that includes a stack of aligned electrodes, the stack comprising at least four groups of electrode tabs offset from one another. 
     In any of the aspects or combinations of the aspects, the electrode stack may further comprise a porous separator positioned between each of the first and second anode and the first and second cathode. 
     In any of the aspects or combinations of the aspects, the battery cell system may further include a first extension tab welded to and laterally extending between the first and second anode tabs. 
     In any of the aspects or combinations of the aspects, the battery cell system may further include a second extension tab welded to and laterally extending between the first and second cathode tabs. 
     In any of the aspects or combinations of the aspects, the battery cell system may further include an electrode tab support, wherein the electrode tab support is fitted over one or more of the first and second anodes and/or cathodes and the first and second extension tabs and provides mechanical support for the first and second extension tabs. 
     In any of the aspects or combinations of the aspects, the electrode tab support may include an electrically insulating polymeric material and provides electrical isolation between the first and/or extension tabs and a protective housing. 
     In any of the aspects or combinations of the aspects, the electrode tab support may include a first slit and a second slit for receiving the first and second extension tabs, where the first and second extension tabs extend through the first slit and the second slit in the electrode tab support. 
     In any of the aspects or combinations of the aspects, the battery cell system may include a structural frame at least partially surrounding the first and second anodes and the first and second cathodes. 
     In any of the aspects or combinations of the aspects, the electrode tab support may be integrally formed within a protective housing, or is directly physically coupled to the protective housing. 
     In any of the aspects or combinations of the aspects, the structural frame may include one or more walls that are flexible and are bent inwards towards the electrode stack, such that the one or more walls accommodate expansion during electrolyte activation. 
     In any of the aspects or combinations of the aspects, the structural frame may include one or more faces with a recessed area of reduced thickness mated with a heat seam of a protective housing. 
     In any of the aspects or combinations of the aspects, the battery cell system may further include a protective housing includes a port receiving an electrolyte and/or venting gasses. 
     In any of the aspects or combinations of the aspects, the negative electrodes and the positive electrode tabs may be offset from one another. 
     In any of the aspects or combinations of the aspects, the electrodes may be the same size, such that when stacked, the edges of the electrodes are aligned with one another, except for the tabs. 
     In any of the aspects or combinations of the aspects, the tabs may be offset when the electrodes are stacked to form an array. 
     In any of the aspects or combinations of the aspects, the electrochemical cell may further include a structural frame through which the electrode tabs extend. 
     In any of the aspects or combinations of the aspects, the structural frame limits lateral movement of the electrode tabs. 
     In any of the aspects or combinations of the aspects, the electrochemical cells may further comprise electrode extension tabs extending from the electrode tabs, and welded to the electrode tabs. 
     In any of the aspects or combinations of the aspects, the at least four groups of electrode tabs may be welded to two electrode extension tabs, and where each of the at least four groups of electrode tabs may only be welded to one of the two electrode extension tabs. 
     In any of the aspects or combinations of the aspects, the at least four groups of electrode tabs may comprise at least two groups of negative electrode tabs and at least two groups positive electrode tabs. 
     In any of the aspects or combinations of the aspects, at least four groups of electrode tabs may comprise a vertically folded portion that is welded to an extension tab. 
     In any of the aspects or combinations of the aspects, the electrochemical cell may further comprise an injection molded frame. 
     In any of the aspects or combinations of the aspects, the electrochemical cell may further comprise a multi-layered laminate pouch. 
     In any of the aspects or combinations of the aspects, the electrochemical cell may further comprise a multi-use port for filling the electrochemical cell with electrolyte and/or degassing the electrochemical cell. 
     In any of the aspects or combinations of the aspects, offset tabs of matching polarity may be welded to an electrode group tab and then may be welded to an extension tab. 
     In any of the aspects or combinations of the aspects, the anode tab may include nickel plated copper and the cathode tab may include aluminum. 
     In any of the aspects or combinations of the aspects, the electrode tab support may have a triangular cross-section. 
     The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein. 
     The following claims particularly point out certain combinations and subcombinations regarded as novel and nonobvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.