Patent Publication Number: US-2023163389-A1

Title: Method and system for formation of cylindrical and prismatic can cells

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE 
     The present application is a continuation of U.S. application Ser. No. 17/377,029, filed Jul. 15, 2021. The aforementioned documents are hereby incorporated herein by reference in their entirety. 
    
    
     FIELD 
     Aspects of the present disclosure relate to energy generation and storage. More specifically, certain embodiments of the disclosure relate to a method and system for formation of cylindrical and prismatic can cells. 
     BACKGROUND 
     Conventional approaches for formation of can cells may be costly, cumbersome, and/or inefficient—e.g., they may be complex and/or time consuming to implement, and may limit battery lifetime. 
     Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present disclosure as set forth in the remainder of the present application with reference to the drawings. 
     BRIEF SUMMARY 
     A system and/or method for formation of cylindrical and prismatic can cells, substantially as shown in and/or described in connection with at least one of the figures, as set forth more completely in the claims. 
     These and other advantages, aspects and novel features of the present disclosure, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         FIG.  1    is a diagram of a battery, in accordance with an example embodiment of the disclosure. 
         FIG.  2 A  is a flow diagram of a lamination process for forming a silicon-dominant anode cell, in accordance with an example embodiment of the disclosure. 
         FIG.  2 B  is a flow diagram of a direct coating process for forming a silicon-dominant anode cell, in accordance with an example embodiment of the disclosure. 
         FIG.  3    illustrates example cell stack expansion during operation, in accordance with an example embodiment of the disclosure 
         FIG.  4    illustrates a can cell with strain absorbing material, in accordance with an example embodiment of the disclosure. 
         FIG.  5 A  illustrates a prismatic can cell with a single electrode stack and internal absorbing layers, in accordance with an example embodiment of the disclosure. 
         FIG.  5 B  illustrates foam pad properties, in accordance with an example embodiment of the disclosure. 
         FIG.  6    illustrates a prismatic can cell with multiple electrode stacks and internal absorbing layers, in accordance with an example embodiment of the disclosure. 
         FIG.  7    illustrates a can cell formation pressure apparatus, in accordance with an example embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    is a diagram of a battery with silicon-dominant anodes, in accordance with an example embodiment of the disclosure. Referring to  FIG.  1   , there is shown a battery  100  comprising a separator  103  sandwiched between an anode  101  and a cathode  105 , with current collectors  107 A and  107 B. There is also shown a load  109  coupled to the battery  100  illustrating instances when the battery  100  is in discharge mode. In this disclosure, the term “battery” may be used to indicate a single electrochemical cell, a plurality of electrochemical cells formed into a module, and/or a plurality of modules formed into a pack. Furthermore, the battery  100  shown in  FIG.  1    is a very simplified example merely to show the principle of operation of a lithium ion cell. Examples of realistic structures are shown to the right in  FIG.  1   , where stacks of electrodes and separators are utilized, with electrode coatings typically on both sides of the current collectors. The stacks may be formed into different shapes, such as a coin cell, cylindrical cell, or prismatic cell, for example. 
     The development of portable electronic devices and electrification of transportation drive the need for high performance electrochemical energy storage. Small-scale (&lt;100 Wh) to large-scale (&gt;10 KWh) devices primarily use lithium-ion (Li-ion) batteries over other rechargeable battery chemistries due to their high-performance. 
     The anode  101  and cathode  105 , along with the current collectors  107 A and  107 B, may comprise the electrodes, which may comprise plates or films within, or containing, an electrolyte material, where the plates may provide a physical barrier for containing the electrolyte as well as a conductive contact to external structures. In other embodiments, the anode/cathode plates are immersed in electrolyte while an outer casing provides electrolyte containment. The anode  101  and cathode are electrically coupled to the current collectors  107 A and  107 B, which comprise metal or other conductive material for providing electrical contact to the electrodes as well as physical support for the active material in forming electrodes. 
     The configuration shown in  FIG.  1    illustrates the battery  100  in discharge mode, whereas in a charging configuration, the load  109  may be replaced with a charger to reverse the process. In one class of batteries, the separator  103  is generally a film material, made of an electrically insulating polymer, for example, that prevents electrons from flowing from anode  101  to cathode  105 , or vice versa, while being porous enough to allow ions to pass through the separator  103 . Typically, the separator  103 , cathode  105 , and anode  101  materials are individually formed into sheets, films, or active material coated foils. Sheets of the cathode, separator and anode are subsequently stacked or rolled with the separator  103  separating the cathode  105  and anode  101  to form the battery  100 . In some embodiments, the separator  103  is a sheet and generally utilizes winding methods and stacking in its manufacture. In these methods, the anodes, cathodes, and current collectors (e.g., electrodes) may comprise films. 
     In an example scenario, the battery  100  may comprise a solid, liquid, or gel electrolyte. The separator  103  preferably does not dissolve in typical battery electrolytes such as compositions that may comprise: Ethylene Carbonate (EC), Fluoroethylene Carbonate (FEC), Propylene Carbonate (PC), Dimethyl Carbonate (DMC), Ethyl Methyl Carbonate (EMC), Diethyl Carbonate (DEC), etc. with dissolved LiBF 4 , LiAsF 6 , LiPF 6 , and LiClO 4  etc. In an example scenario, the electrolyte may comprise Lithium hexafluorophosphate (LiPF 6 ) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) that may be used together in a variety of electrolyte solvents. Lithium hexafluorophosphate (LiPF 6 ) may be present at a concentration of about 0.1 to 2.0 molar (M) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) may be present at a concentration of about 0 to 2.0 molar (M). Solvents may comprise one or more of ethylene carbonate (EC), fluoroethylene carbonate (FEC) and/or ethyl methyl carbonate (EMC) in various percentages. In some embodiments, the electrolyte solvents may comprise one or more of EC from about 0-40%, FEC from about 2-40% and/or EMC from about 50-70%. The electrolyte can also be a polymer or polymer gel type electrolyte, which includes solid polymer and gel polymer electrolytes (GPE) where a gelling agent is added to a liquid electrolyte. GPEs consist of liquid electrolyte absorbed within a polymer matrix. Examples of polymer matrix are poly(vinylidene difluoride) (PVdF), poly(ethylene oxide) (PEO), poly(methyl methacrylate) (PMMA), polyvinyl chloride (PVC), and poly-(vinylidene fluoride-hexafluoropropylene). Polymer groups such as (but not limited to) polyacrylate, polynitrile, polyether, polycarbonate polyvinyl can be considered as other polymer hosts for GPEs. 
     Inorganic solid electrolytes (ISE), solid polymer electrolytes (SPE), and composite electrolytes (CSE) can also be employed. SPEs with inert oxide ceramic as fillers such as SiO 2 , Al 2 O 3 , TiO 2 , zeolite are some examples that can been incorporated into a polymer. Garnet-type (A 3 B 2 (XO 4 ) 3  (A=Ca, Mg, Y, La or rare-earth elements; B=Al, Fe, Ga, Ge, Mn, Ni, or V), Perovskite-type solid electrolytes, NASICON-type and LISICON-type SPEs can also be introduced as fast ionic conductors. 
     The separator  103  may be wet or soaked with a liquid or gel electrolyte. In addition, in an example embodiment, the separator  103  does not melt below about 100 to 120° C., and exhibits sufficient mechanical properties for battery applications. A battery, in operation, can experience expansion and contraction of the anode and/or the cathode. In an example embodiment, the separator  103  can expand and contract by at least about 5 to 10% without failing, and may also be flexible. 
     The separator  103  may be sufficiently porous so that ions can pass through the separator once wet with, for example, a liquid or gel electrolyte. Alternatively (or additionally), the separator may absorb the electrolyte through a gelling or other process even without significant porosity. The porosity of the separator  103  is also generally not too porous to allow the anode  101  and cathode  105  to transfer electrons through the separator  103 . 
     The anode  101  and cathode  105  comprise electrodes for the battery  100 , providing electrical connections to the device for transfer of electrical charge in charge and discharge states. The anode  101  may comprise silicon, carbon, or combinations of these materials, for example. Typical anode electrodes comprise a carbon material that includes a current collector such as a copper sheet. Carbon is often used because it has excellent electrochemical properties and is also electrically conductive. Anode electrodes currently used in rechargeable lithium-ion cells typically have a specific capacity of approximately 200 milliamp hours per gram. Graphite, the active material used in most lithium ion battery anodes, has a theoretical energy density of 372 milliamp hours per gram (mAh/g). In comparison, silicon has a high theoretical capacity of 4200 mAh/g. In order to increase volumetric and gravimetric energy density of lithium-ion batteries, silicon may be used as the active material for the cathode or anode. Silicon anodes may be formed from silicon composites, with more than 50% silicon or more by weight in the anode material on the current collector, for example. 
     In an example scenario, the anode  101  and cathode  105  store the ion used for separation of charge, such as lithium. In this example, the electrolyte carries positively charged lithium ions from the anode  101  to the cathode  105  in discharge mode, as shown in  FIG.  1    for example, and vice versa through the separator  105  in charge mode. The movement of the lithium ions creates free electrons in the anode  101  which creates a charge at the positive current collector  107 B. The electrical current then flows from the current collector through the load  109  to the negative current collector  107 A. The separator  103  blocks the flow of electrons inside the battery  100 , allows the flow of lithium ions, and prevents direct contact between the electrodes. 
     While the battery  100  is discharging and providing an electric current, the anode  101  releases lithium ions to the cathode  105  via the separator  103 , generating a flow of electrons from one side to the other via the coupled load  109 . When the battery is being charged, the opposite happens where lithium ions are released by the cathode  105  and received by the anode  101 . 
     The materials selected for the anode  101  and cathode  105  are important for the reliability and energy density possible for the battery  100 . The energy, power, cost, and safety of current Li-ion batteries need to be improved in order to, for example, compete with internal combustion engine (ICE) technology and allow for the widespread adoption of electric vehicles (EVs). High energy density, high power density, and improved safety of lithium-ion batteries are achieved with the development of high-capacity and high-voltage cathodes, high-capacity anodes and functionally non-flammable electrolytes with high voltage stability and interfacial compatibility with electrodes. In addition, materials with low toxicity are beneficial as battery materials to reduce process cost and promote consumer safety. 
     The performance of electrochemical electrodes, while dependent on many factors, is largely dependent on the robustness of electrical contact between electrode particles, as well as between the current collector and the electrode particles. The electrical conductivity of silicon anode electrodes may be manipulated by incorporating conductive additives with different morphological properties. Carbon black (SuperP), vapor grown carbon fibers (VGCF), and a mixture of the two have previously been incorporated separately into the anode electrode resulting in improved performance of the anode. The synergistic interactions between the two carbon materials may facilitate electrical contact throughout the large volume changes of the silicon anode during charge and discharge. 
     State-of-the-art lithium-ion batteries typically employ a graphite-dominant anode as an intercalation material for lithium. Silicon-dominant anodes, however, offer improvements compared to graphite-dominant Li-ion batteries. Silicon exhibits both higher gravimetric (4200 mAh/g vs. 372 mAh/g for graphite) and volumetric capacities (2194 mAh/L vs. 890 mAh/L for graphite). In addition, silicon-based anodes have a low lithiation/delithiation voltage plateau at about 0.3-0.4V vs. Li/Li+, which allows it to maintain an open circuit potential that avoids undesirable Li plating and dendrite formation. While silicon shows excellent electrochemical activity, achieving a stable cycle life for silicon-based anodes is challenging due to silicon&#39;s large volume changes during lithiation and delithiation. Silicon regions may lose electrical contact from the anode as large volume changes coupled with its low electrical conductivity separate the silicon from surrounding materials in the anode. 
     In addition, the large silicon volume changes exacerbate solid electrolyte interphase (SEI) formation, which can further lead to electrical isolation and, thus, capacity loss. Expansion and shrinkage of silicon particles upon charge-discharge cycling causes pulverization of silicon particles, which increases their specific surface area. As the silicon surface area changes and increases during cycling, SEI repeatedly breaks apart and reforms. The SEI thus continually builds up around the pulverizing silicon regions during cycling into a thick electronic and ionic insulating layer. This accumulating SEI increases the impedance of the electrode and reduces the electrode electrochemical reactivity, which is detrimental to cycle life. 
     In this disclosure, prismatic and cylindrical can cells are described where the expansion of the electrodes during formation and cycling is known, and strain absorbing layers may be incorporated in the cans to configure a desired pressure. The formation process comprises at least one charge/discharge cycle. The current may be greater than 1 C, greater than 2 C, greater than 3 C, or greater than 4 C, for example, to reduce the formation time. Sizing of the internal stack of electrodes/separator may be configured so that the electrodes expand just enough to apply the right range of pressure on the stack. In addition, applying pressure or just placing the can cell in a constant gap metal plate system so that the metal can does not bulge during formation or during cycling may also provide desired formation pressures while reducing/eliminating can bulging during operation. Having a foam or other “springy” material within the can cell may ensure pressure uniformity. The foam may comprise a foam that is robust to electrolyte and stable at elevated temperatures that is suitable for high temperature cell operation. In another example scenario, an excess separator or multiple layers of separator may be utilized to provide this interface, or springy material. An inert filler material may also be used such as alumina, silica, or zirconia. 
       FIG.  2 A  is a flow diagram of a lamination process for forming a silicon-dominant anode cell, in accordance with an example embodiment of the disclosure. This process employs a high-temperature pyrolysis process on a substrate, layer removal, and a lamination process to adhere the active material layer to a current collector. 
     The raw electrode active material is mixed in step  201 . In the mixing process, the active material may be mixed, e.g., a binder/resin (such as PI, PAI), solvent, and conductive additives. The materials may comprise carbon nanotubes/fibers, graphene sheets, metal polymers, metals, semiconductors, and/or metal oxides, for example. Silicon powder with a 1-30 or 5-30 μm particle size, for example, may then be dispersed in polyamic acid resin (15% solids in N-Methyl pyrrolidone (NMP)) at, e.g., 1000 rpm for, e.g., 10 minutes, and then the conjugated carbon/NMP slurry may be added and dispersed at, e.g., 2000 rpm for, e.g., 10 minutes to achieve a slurry viscosity within 2000-4000 cP and a total solid content of about 30%. 
     In step  203 , the slurry may be coated on a substrate. In this step, the slurry may be coated onto a Polyester, polyethylene terephthalate (PET), or Mylar film at a loading of, e.g., 2-4 mg/cm 2  and then undergo drying to an anode coupon with high Si content and less than 15% residual solvent content. This may be followed by an optional calendering process in step  205 , where a series of hard pressure rollers may be used to finish the film/substrate into a smoothed and denser sheet of material. 
     In step  207 , the green film may then be removed from the PET, where the active material may be peeled off the polymer substrate, the peeling process being optional for a polypropylene (PP) substrate, since PP can leave ˜2% char residue upon pyrolysis. The peeling may be followed by a pyrolysis step  209  where the material may be heated to 600-1250 C for 1-3 hours, cut into sheets, and vacuum dried using a two-stage process (120° C. for 15 h, 220° C. for 5 h). 
     In step  211 , the electrode material may be laminated on a current collector. For example, a 5-20 μm thick copper foil may be coated with polyamide-imide with a nominal loading of, e.g., 0.2-0.6 mg/cm 2  (applied as a 6 wt % varnish in NMP and dried for, e.g., 12-18 hours at, e.g., 110° C. under vacuum). The anode coupon may then be laminated on this adhesive-coated current collector. In an example scenario, the silicon-carbon composite film is laminated to the coated copper using a heated hydraulic press. An example lamination press process comprises 30-70 seconds at 300° C. and 3000-5000 psi, thereby forming the finished silicon-composite electrode. 
     The electrodes may be stacked with one or more separators between electrodes, and strain absorbing material comprising a foam or other springy material may be incorporated when incorporating the stack in a can, such as a cylindrical or prismatic can. Extra layers of separator may purposely be introduced, for example, by winding extra layers of separator outside of the stack. 
     In step  213 , the cell may be assessed before being subject to a formation process. The measurements may comprise impedance values, open circuit voltage, and thickness measurements. During formation, the initial lithiation of the anode may be performed, followed by delithiation. Cells may be clamped during formation and/or early cycling. The formation cycles are defined as any type of charge/discharge of the cell that is performed to prepare the cell for general cycling and is considered part of the cell production process. Different rates of charge and discharge may be utilized in formation steps and the known expansion along with the strain absorbing material within the can may enable a desired pressure on the electrodes during formation, leading to increased performance and cell life, and may also be beneficial for pack design with can cells. 
       FIG.  2 B  is a flow diagram of a direct coating process for forming a silicon-dominant anode cell, in accordance with an example embodiment of the disclosure. This process comprises physically mixing the active material, conductive additive, and binder together, and coating it directly on a current collector before pyrolysis. This example process comprises a direct coating process in which an anode or cathode slurry is directly coated on a copper foil using a binder such as CMC, SBR, Sodium Alginate, PAI, PI and mixtures and combinations thereof. 
     In step  221 , the active material may be mixed, e.g., a binder/resin (such as PI, PAI), solvent, and conductive additives. The materials may comprise carbon nanotubes/fibers, graphene sheets, metal polymers, metals, semiconductors, and/or metal oxides, for example. Silicon powder with a 5-30 μm particle size, for example, may then be dispersed in polyamic acid resin (15% solids in N-Methyl pyrrolidone (NMP)) at, e.g., 1000 rpm for, e.g., 10 minutes, and then the conjugated carbon/NMP slurry may be added and dispersed at, e.g., 2000 rpm for, e.g., 10 minutes to achieve a slurry viscosity within 2000-4000 cP and a total solid content of about 30%. 
     Furthermore, cathode active materials may be mixed in step  221 , where the active material may comprise lithium cobalt oxide (LCO), lithium iron phosphate, lithium nickel cobalt manganese oxide (NMC), lithium nickel cobalt aluminum oxide (NCA), lithium manganese oxide (LMO), lithium nickel manganese spinel, or similar materials or combinations thereof, mixed with a binder as described above for the anode active material. 
     In step  223 , the slurry may be coated on a copper foil. In the direct coating process described here, an anode slurry is coated on a current collector with residual solvent followed by a calendaring process for densification followed by pyrolysis (˜500-800 C) such that carbon precursors are partially or completely converted into glassy carbon. Similarly, cathode active materials may be coated on a foil material, such as aluminum, for example. The active material layer may undergo a drying in step  225  resulting in reduced residual solvent content. An optional calendering process may be utilized in step  227  where a series of hard pressure rollers may be used to finish the film/substrate into a smoother and denser sheet of material. In step  227 , the foil and coating proceeds through a roll press for lamination. 
     In step  229 , the active material may be pyrolyzed by heating to 500-1000° C. such that carbon precursors are partially or completely converted into glassy carbon. Pyrolysis can be done either in roll form or after punching. If done in roll form, the punching is done after the pyrolysis process. The pyrolysis step may result in an anode active material having silicon content greater than or equal to 50% by weight, where the anode has been subjected to heating at or above 400 degrees Celsius. In an example scenario, the anode active material layer may comprise 20 to 95% silicon and in yet another example scenario may comprise 50 to 95% silicon by weight. In instances where the current collector foil is not pre-punched/pre-perforated, the formed electrode may be perforated with a punching roller, for example. The electrodes may then be sandwiched with a separator and electrolyte to form a cell. The electrodes may be stacked with one or more separators between electrodes, and strain absorbing material comprising a foam or other springy material may be incorporated when incorporating the stack in a can, such as a cylindrical or prismatic can. Extra layers of separator may purposely be introduced, for example, by winding extra layers of separator outside of the stack. 
     In step  233 , the cell may be assessed before being subject to a formation process. The measurements may comprise impedance values, open circuit voltage, and thickness measurements. During formation, the initial lithiation of the anode may be performed, followed by delithiation. Cells may be clamped during formation and/or early cycling. The formation cycles are defined as any type of charge/discharge of the cell that is performed to prepare the cell for general cycling and is considered part of the cell production process. Different rates of charge and discharge may be utilized in formation steps and the known expansion along with the strain absorbing material within may enable a desired pressure or pressure range on the electrodes during formation, leading to increased performance and cell life. 
       FIG.  3    illustrates example cell stack expansion during operation, in accordance with an example embodiment of the disclosure. Referring to  FIG.  3   , there is shown can cell  300  comprising can  301 , cell stack  303 , cell pouch  305 , and terminals  307 . The can  301  may comprise a metal container, for example, that provides structural rigidity as well as protection from the external environment such as air and moisture. In this example, the can  301  comprises a prismatic shape, such as a rectangular shape, although may instead comprise a cylindrical or other shape in some embodiments. 
     The cell stack  303  comprises one or more sets of anode/separator/cathode stacked within an electrolyte to form a cell, where the number of stacks may be configured based on desired cell output or cycle capacity, for example. In an example scenario, the cell stack  303  may also be enclosed in a cell pouch  305 , which may provide further environmental isolation for the cell stack  303  and its electrolyte. The cell pouch  305  may comprise a plastic material and may have terminals  307  comprising metal tabs, for example, extending from the cell pouch  305  that provide electrical contact to the cell stack  303 , one being electrically coupled to the anode(s) and the other to the cathode(s). In some embodiments, the cell pouch  305  is optional, such as in instances where the can  301  provides adequate protection from the environment. The terminals  307  provide electrical connection to terminals outside the can  301 . 
     As shown by the two views in  FIG.  3   , the cell stack  303  expands due to the lithiation of the anode during charging, for example. The upper view shows the cell stack  303  before lithiation and the lower view shows the cell stack  303  after lithiation. As described above, the charging of silicon-dominant anodes causes physical expansion of the electrodes due to lithiation of the silicon, which can result in pressure on the cell stack  303  if the dimensions of the can  301  are less than the final thickness, without restraint, of the cell stack  303 . 
     If the expansion of the cell is too high or too low, the cell performance may be non-optimal. Therefore, it is desirable to provide a strain absorbing material of a desired thickness and springiness to provide a desired pressure on the stack as well as evening out the pressure so that pressure is more uniform during the formation process, as well as during regular cycling. This is shown further with respect to  FIGS.  4 - 7   . 
       FIG.  4    illustrates a can cell with strain absorbing material, in accordance with an example embodiment of the disclosure. Referring to  FIG.  4   , there is shown can cell  400  comprising can  401 , cell stack  403 , cell stack pouch  405 , terminals  407 , strain absorbing material  409 , external terminals  411 A and  411 B, and electrolyte fill hole  413 . 
     The can  401 , cell stack  403 , cell stack pouch  405 , and terminals  407  may be similar to similar elements described with respect to  FIGS.  1 - 3   . The lines shown in the cell stack  403  represent the stacked anodes, cathodes, and separators within an electrolyte. The terminals  407  provide electrical connection to external terminals  411 A and  411 B on the outside surface of the can  401 . While a prismatic can is shown in  FIG.  4   , a cylindrical or other shaped can may be utilized in accordance with the present disclosure. The strain absorbing material  409  may comprise a foam, open or closed cell, for example, or other elastic material that may be operable to absorb strain from the expanding cells stack  403  during lithiation, and provide a desired resistive pressure against the expansion of the cell stack  403 . In another example embodiment, the strain absorbing material  409  may comprise a gel polymer electrolyte, in which case the cell stack pouch  405  would not be needed. 
     In yet another example, the strain absorbing material  409  comprises a solid state or semi-solid state electrolyte, such as gel-polymer electrolytes. The electrolyte may be a polymer or polymer gel type electrolyte, which includes solid polymer and gel polymer electrolytes (GPE) where a gelling agent is added to a liquid electrolyte. GPEs consist of liquid electrolyte absorbed within a polymer matrix. Examples of polymer matrix are poly(vinylidene difluoride) (PVdF), poly(ethylene oxide) (PEO), poly(methyl methacrylate) (PMMA), polyvinyl chloride (PVC), and poly-(vinylidene fluoride-hexafluoropropylene). Polymer groups such as (but not limited to) polyacrylate, polynitrile, polyether, polycarbonate polyvinyl can be considered as other polymer hosts for GPEs. 
     Inorganic solid electrolytes (ISE), solid polymer electrolytes (SPE), and composite electrolytes (CSE) can also be employed. SPEs with inert oxide ceramic as fillers such as SiO 2 , Al 2 O 3 , TiO 2 , zeolite are some examples that can been incorporated into a polymer. Garnet-type (A 3 B 2 (XO 4 ) 3  (A=Ca, Mg, Y, La or rare-earth elements; B=Al, Fe, Ga, Ge, Mn, Ni, or V), Perovskite-type solid electrolytes, NASICON-type and LISICON-type SPEs can also be introduced as fast ionic conductors. 
     In instances where the electrolyte is a liquid and there is no cell pouch  405 , the electrolyte may be incorporated into the can  401  via the electrolyte fill hole  413 , which is subsequently sealed. In yet another example, the strain absorbing material  409  may comprise a leaf spring mechanism between the cell stack  403  and the walls of the can  401  for absorbing strain/applying pressure on the cell stack  403 . In yet another example, the strain absorbing material  409  can be powder or a powder suspension of inert material such as silica, alumina, or zirconia. 
     In silicon anode can cells, the can may bulge out during the formation process and/or when cycling. To counter that, pressure may be applied to the can or it may be placed in a constant gap setup. During formation, the applied pressure or constant gap setup may prevent bulging, such that even after the added pressure is removed or the can is removed from the setup, the cell does not bulge in subsequent cycles. In an example with large amounts of expansion, on the order of 10-20%, when the cells tack is placed in the can and subjected to a formation process, there may not be adequate pressure if enough space is left to allow expansion. In this case, springy material, such as the strain absorbing material  409 , may be incorporated in the can  401 . In an example scenario, a physically robust foam may be utilized that is also chemically robust to the electrolyte. 
     Another option is to utilize multiple separators with some amount of elasticity, increasing the thickness such that the pressure applied during formation is configured at a desired level for increased cell performance and cell life. Some example materials for the strain absorbing material in gel form are polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF), etc. Some examples may comprise polymer matrix such as poly(vinylidene difluoride) (PVdF), poly(ethylene oxide) (PEO), poly(methyl methacrylate) (PMMA), polyvinyl chloride (PVC), and poly-(vinylidene fluoride-hexafluoropropylene). Polymer groups but not limited to polyacrylate, polynitrile, polyether, polycarbonate polyvinyl can be considered as the polymer hosts for GPE. Different rates of charge and discharge may be utilized in formation steps and the known expansion of the cell stack  403  along with the strain absorbing materials  409  within the can  401  may enable a desired pressure on the electrodes during formation, leading to increased performance and cell life. 
       FIG.  5 A  illustrates a prismatic can cell with a single electrode stack an internal absorbing layers, in accordance with an embodiment of the disclosure. Referring to  FIG.  5   , there is shown a prismatic can cell  500  comprising can  501 , cell stack  503 , cell pouch  505 , terminals  507 , and strain absorbing materials  509 A- 509 C. The can  501 , cell stack  503 , cell stack pouch  505 , and terminals  507  may be similar to similar elements described with respect to  FIGS.  1 - 4   . 
     The strain absorbing materials  509 A and  509 B may comprise foam pads, excess separator, or other springy materials incorporated within the can  501  and may be of a certain thickness and rigidity to provide a desired pressure when the cell stack  503  expands upon lithiation during formation. The absorbing material  509 C may comprise a gel surrounding the cell stack  503 , and may be the same or different than the strain absorbing materials  509 A and  509 B. These gels may comprise polymers that contain polyacrylate, polynitrile, polyether, polycarbonate, polyvinyl, that may be considered as the polymer hosts for GPE, which can trap Li conducting organic solvent (electrolyte). 
     The use of the strain absorbing materials  509 A and  509 B between cell stacks, such as cell stack  503 , and the can  501 , distributes the cell pressure evenly across the cell. The pressure on the cells may range between 10 kPa and 1 MPa, 50 kPa and 500 kPa, 50 kPa and 300 kPa. The relationship between deformation of the elastic material (displacement) and pressure may be nonlinear and different for each foam, as illustrated in  FIG.  5 B . 
     The strain absorbing material  509 A and  509 B may be electrochemically and chemically inactive with the electrolyte and other cell components. Different rates of charge and discharge may be utilized in formation steps and the known expansion of the cell stack  503  along with the strain absorbing materials  509 A and  509 B within the can  501  may enable a desired pressure on the electrodes during formation, leading to increased performance and cell life. 
       FIG.  5 B  illustrates foam pad properties, in accordance with an example embodiment of the disclosure. Referring to FIR.  5 B, there is shown foam pad compression versus displacement and pressure versus displacement for various foams and thicknesses, where the solid lines represent compression and the dashed lines represent force (pressure). As can be seen from the plots, while the compression is linear with displacement, the pressure is not linear with displacement. 
       FIG.  6    illustrates a prismatic can cell with multiple electrode stacks and internal absorbing layers, in accordance with an embodiment of the disclosure. Referring to  FIG.  6   , there is shown a prismatic can cell  600  comprising can  601 , cell stacks  603 A and  603 B, cell pouches  605 A and  605 B, terminals  607 A and  607 B, and strain absorbing materials  609 A- 609 C. The can  601 , cell stacks  603 A and  603 B, cell stack pouches  605 A and  605 B, and terminals  607 A and  607 B may be similar to similar elements described with respect to  FIGS.  1 - 5   . While a prismatic can cell is shown, a cylindrical or other shape can is possible in accordance with the present disclosure. 
     The strain absorbing materials  609 A- 609 C may comprise gels, foam pads, excess separator layer or layers, inert particle suspensions, or other springy or elastic materials incorporated within the can  601  and may be of a certain thickness and rigidity to provide a desired pressure when the cell stacks  603 A and  603 B expand upon lithiation during formation or operation. Example gel materials comprise polymers that contain polyacrylate, polynitrile, polyether, polycarbonate polyvinyl can be considered as the polymer hosts for GPE, which can trap Li conducting organic solvent (electrolyte). The strain absorbing material  609 C may be the same or different than the strain absorbing materials  609 A and  609 B. In one example, the absorbing materials  609 A and  609 B comprise a gel mostly surrounding the cell stacks  603 A and  603 B, while the absorbing material  609 C comprises a foam layer between the cell stacks  603 A and  603 B. 
     The strain absorbing materials  609 A- 609 C may comprise electrolyte, which may be a polymer or polymer gel type electrolyte, which includes solid polymer and gel polymer electrolytes (GPE) where a gelling agent is added to a liquid electrolyte. GPEs consist of liquid electrolyte absorbed within a polymer matrix. Examples of polymer matrix are poly(vinylidene difluoride) (PVdF), poly(ethylene oxide) (PEO), poly(methyl methacrylate) (PMMA), polyvinyl chloride (PVC), and poly-(vinylidene fluoride-hexafluoropropylene). Polymer groups such as (but not limited to) polyacrylate, polynitrile, polyether, polycarbonate polyvinyl can be considered as other polymer hosts for GPEs. In yet another example, the strain absorbing material  609 A- 609 C can be powder or a powder suspension of inert material such as silica, alumina, or zirconia. 
     The absorbing materials  609 A- 609 C may enable pressures ranging from 10 kPa to 1 MPa, 50 kPa to 500 kPa, and 50 kPa to 300 kPa. Different rates of charge and discharge may be utilized in formation steps and the known expansion of the cell stacks  603 A and  603 B along with the strain absorbing material  605 A- 605 C within the can may enable a desired pressure on the electrodes during formation, leading to increased performance and cell life. Materials used in  609 A- 609 C and  605 A- 605 C may or may not be the same pressure absorbing material. 
       FIG.  7    illustrates a can cell formation pressure apparatus, in accordance with an example embodiment of the disclosure. Referring to  FIG.  7   , there is shown formation pressure apparatus  700  applying pressure to can  701 , the apparatus comprising top and bottom pressure plates  725 A and  725 B, spacers  721 A and  721 B, strain absorbing materials  709 A and  709 B, and bolts  723 A and  723 B. The can  701  comprises terminals  711 A and  711 B and electrolyte fill hole  713 , although other terminal and fill hole placements are possible, depending on the application. 
     The spacers  721 A and  721 B may be configured to provide a fixed spacing between the top and bottom plates  725 A and  725 B, where the can  701  is placed within with the strain absorbing materials  709 A and  709 B, so that a desired range of pressure is applied to the can  701  as uniformly as possible during the formation process. The absorbing materials  709 A and  709 B may be in addition to absorbing materials within the can  701 , and may comprise polymer matrix such as poly(vinylidene difluoride) (PVdF), poly(ethylene oxide) (PEO), poly(methyl methacrylate) (PMMA), polyvinyl chloride (PVC), and poly-(vinylidene fluoride-hexafluoropropylene). Polymer groups such as (but not limited to) polyacrylate, polynitrile, polyether, polycarbonate polyvinyl can be considered as other polymer hosts for GPEs. In yet another example, the strain absorbing material  609 A- 609 C may be powder or a powder suspension of inert material such as silica, alumina, or zirconia. 
     The absorbing materials  709 A and  709  may provide pressures ranging from 10 kPa to 1 MPa, 50 kPa to 500 kPa, and 50 kPa to 300 kPa. Different rates of charge and discharge may be utilized in formation steps and the known expansion of the cell stack along with the strain absorbing material within the can  701  and the strain absorbing materials  709 A and  709 B external to the can  701  may enable a desired pressure on the electrodes during formation, leading to increased performance and cell life. 
     In an example embodiment of the disclosure, a method and system is described for formation of cylindrical and prismatic can cells, and may include providing a battery comprising: one or more cells, each cell comprising at least one silicon-dominant anode, a cathode, and a separator; and a metal can that contains the one or more cells such that during formation a pressure between 50 kPa and 1 MPa is applied to the one or more cells. One or more strain absorbing materials may be arranged between the one or more cells and interior walls of the can. The strain absorbing materials may comprise foam. The strain absorbing materials may comprise a solid electrolyte layer. 
     The strain absorbing materials may comprise The strain absorbing materials may comprise some sort of foam, excess separator, PMMA, PVDF, or a combination thereof. The strain absorbing materials may comprise powder or a powder suspension of inert material such as silica, alumina, or zirconia. A pressure may be applied to the one or more cells during a formation process due to a thickness of the strain absorbing materials being thicker than an expansion of the one or more cells during lithiation of the at least one silicon-dominant anode. The battery may comprise two or more cells and a first absorbing material is between one of the two or more cells and an interior wall of the can and a second absorbing material is between two of the two or more cells. The first absorbing material may be a different material than the second absorbing material or may be a same material as the second absorbing material. One or more strain absorbing materials may be placed outside the can during the formation process. The formation process may comprise one or more charge and discharge cycles with currents greater than 1 C. 
     As utilized herein the terms “circuits” and “circuitry” refer to physical electronic components (i.e. hardware) and any software and/or firmware (“code”) which may configure the hardware, be executed by the hardware, and or otherwise be associated with the hardware. As used herein, for example, a particular processor and memory may comprise a first “circuit” when executing a first one or more lines of code and may comprise a second “circuit” when executing a second one or more lines of code. As utilized herein, “and/or” means any one or more of the items in the list joined by “and/or”. As an example, “x and/or y” means any element of the three-element set {(x), (y), (x, y)}. In other words, “x and/or y” means “one or both of x and y”. As another example, “x, y, and/or z” means any element of the seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, “x, y and/or z” means “one or more of x, y and z”. As utilized herein, the term “exemplary” means serving as a non-limiting example, instance, or illustration. As utilized herein, the terms “e.g.,” and “for example” set off lists of one or more non-limiting examples, instances, or illustrations. As utilized herein, a battery, circuitry or a device is “operable” to perform a function whenever the battery, circuitry or device comprises the necessary hardware and code (if any is necessary) or other elements to perform the function, regardless of whether performance of the function is disabled or not enabled (e.g., by a user-configurable setting, factory trim, configuration, etc.). 
     While the present invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from its scope. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed, but that the present invention will include all embodiments falling within the scope of the appended claims.