PATENT DOCUMENT

Publication Number: US-10637093-B2
Application Number: US-201816007369-A
Country: US
Kind Code: B2

Title: Thin film battery structures having sloped cell sidewalls

Abstract:
Solid-state battery structures and methods of manufacturing solid-state batteries, such as thin-film batteries, are disclosed. More particularly, embodiments relate to solid-state batteries having a current collector tab between multiple electrochemical cells each having an electrolyte layer between an anode layer and a cathode layer in a vertical direction. The anode layer, the electrolyte layer, and the cathode layer include respective sidewalls exposed along a cell sidewall, and the cell sidewall has a non-zero, non-vertical slope.

Claims:
What is claimed is: 
     
       1. An electrochemical device, comprising:
 a first electrochemical cell, comprising:
 a first electrolyte layer between a first anode layer and a first cathode layer in a vertical direction, wherein the first anode layer, the first electrolyte layer, and the first cathode layer include respective sidewalls exposed along a first cell sidewall, and wherein the first cell sidewall has a non-zero, non-vertical slope; and 
 
 a second electrochemical cell, comprising:
 a second electrolyte layer between a second anode layer and a second cathode layer in a vertical direction, wherein the second anode layer, the second electrolyte layer, and the second cathode layer include respective sidewalls exposed along a second cell sidewall, the second cell sidewall has a non-zero, non-vertical slope, and the second anode layer contacts a top surface of the anode layer of the first electrochemical cell; and 
 a cathode current collector tab in contact with the first cell side wall of the first electrochemical cell and the second cell sidewall of the second electrochemical cell. 
 
 
     
     
       2. The electrochemical device of  claim 1 , wherein the first anode layer includes a top surface, and wherein a height of the first cell sidewall diminishes in a transverse direction outwardly from the top surface along the non-zero, non-vertical slope. 
     
     
       3. The electrochemical device of  claim 2 , wherein the respective exposed sidewalls of the first anode layer, the first electrolyte layer, and the first cathode layer are contiguous along the non-zero, non-vertical slope. 
     
     
       4. The electrochemical device of  claim 3 , wherein the non-zero, non-vertical slope includes a linear slope portion. 
     
     
       5. The electrochemical device of  claim 3 , wherein the non-zero, non-vertical slope includes a curvilinear slope portion. 
     
     
       6. The electrochemical device of  claim 3 , wherein the exposed sidewall of the first anode layer extends between an anode top edge on the top surface and the exposed sidewall of the first electrolyte layer, and wherein the exposed sidewall of the first electrolyte layer extends between the exposed sidewall of the first anode layer and the exposed sidewall of the first cathode layer. 
     
     
       7. The electrochemical device of  claim 6 , wherein the exposed sidewall of the first cathode layer is offset from the exposed sidewall of the first anode layer in the vertical direction and in a transverse direction outwardly along the non-zero, non-vertical slope. 
     
     
       8. The electrochemical device of  claim 2 , wherein the first electrochemical cell further comprises:
 a first cathode current collector having a top surface, wherein the first cathode layer is over the top surface of the first cathode current collector, wherein the height of the first cell sidewall diminishes in the transverse direction outwardly from the top surface of the first anode layer along the non-zero, non-vertical slope to a terminal edge on the first cathode current collector, and wherein the terminal edge is offset in the vertical direction from the top surface of the first cathode current collector. 
 
     
     
       9. The electrochemical device of  claim 8 , wherein the first cathode current collector includes a bottom surface below the top surface of the first cathode current collector, and wherein the terminal edge is on the bottom surface and the first cell sidewall diminishes from the top surface of the first anode layer to the terminal edge across a cell height of the first electrochemical cell. 
     
     
       10. The electrochemical device of  claim 1 , wherein the first cathode layer of the first electrochemical cell includes a first cathode current collector having a first exposed horizontal surface and the second cathode layer has a second cathode current collector having a second exposed horizontal surface, the cathode current collector tab also in contact with the first exposed horizontal surface and the second exposed horizontal surface. 
     
     
       11. An electrochemical device, comprising:
 a first electrochemical cell, comprising:
 a first anode layer, a first electrolyte layer, a first cathode layer, and a first cathode current collector stacked in a vertical direction, wherein the first anode layer, the first electrolyte layer, and the first cathode layer include respective sidewalls exposed by removing material from the layers using an ablation process, and wherein the respective sidewalls of the first anode layer, the first electrolyte layer, and the first cathode layer are exposed and contiguous with each other along a first cell sidewall, 
 
 wherein the first cathode current collector has an exposed horizontal surface that is in a first vertical plane and a cathode contacting surface that is in a second vertical plane that is different from the first vertical plane. 
 
     
     
       12. The electrochemical device of  claim 11 , wherein the first cell sidewall has a non-zero, non-vertical slope. 
     
     
       13. The electrochemical device of  claim 12 , wherein the first cathode layer is over a top surface of the first cathode current collector, wherein the first cathode current collector includes a sidewall exposed by removing material from the first cathode current collector using the ablation process, wherein the sidewall of the first cathode current collector is exposed and contiguous with the other exposed sidewalls of the first anode layer, the first electrolyte layer, and the first cathode layer, and wherein a height of the first cell sidewall diminishes outwardly from a top surface of the first anode layer along the non-zero, non-vertical slope. 
     
     
       14. The electrochemical device of  claim 12 , wherein an exposed sidewall of the first anode layer extends between an anode top edge on a top surface and an exposed sidewall of the first electrolyte layer, and wherein the exposed sidewall of the first electrolyte layer extends between an exposed sidewall of the first anode layer and an exposed sidewall of the first cathode layer. 
     
     
       15. The electrochemical device of  claim 14 , wherein the exposed sidewall of the first cathode layer is offset from the exposed sidewall of the anode layer in the vertical direction and in a transverse direction outwardly along the non-zero, non-vertical slope. 
     
     
       16. The electrochemical device of  claim 11 , further comprising a second electrochemical cell comprising:
 a second anode layer, a second electrolyte layer, a second cathode layer, and a second cathode current collector stacked in the vertical direction, wherein the second anode layer, the second electrolyte layer, and the second cathode layer include respective sidewalls exposed by removing material from the second anode layer, the second electrolyte layer, and the second cathode layer using the ablation process, and wherein a top surface of the second anode layer is in contact with a top surface of the first anode layer; and 
 a cathode current collector tab in contact with each of the first cathode current collector and the second cathode current collector. 
 
     
     
       17. The electrochemical device of  claim 16 , wherein the first cathode current collector has a first exposed horizontal surface and the second cathode current collector has a second exposed horizontal surface, the cathode current collector tab in contact with the first exposed horizontal surface and the second exposed horizontal surface. 
     
     
       18. The electrochemical device of  claim 17 , wherein the first exposed horizontal surface of the first cathode current collector is in a first vertical plane and a first cathode contacting surface is in a second vertical plane that is different from the first vertical plane, and the second exposed horizontal surface of the second cathode current collector is in a third vertical plane and a second cathode contacting surface of the second cathode current collector is in a fourth vertical plane that is different from the third vertical plane.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. Pat. No. 10,020,532 filed on May 26, 2015, which claims the benefit of U.S. Provisional Patent Application No. 62/003,504, filed May 27, 2014, and U.S. Provisional Patent Application No. 62/165,101, filed May 21, 2015, each hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Embodiments relate to electrochemical devices and methods of manufacturing electrochemical devices. More particularly, some embodiments relate to solid-state batteries, and in particular thin film batteries. Other embodiments are also described. 
     BACKGROUND 
     Solid-state batteries, such as thin-film batteries, are known to provide better form factors, cycle life, power capability, and safety, as compared to conventional battery technologies. However, solid-state battery structure and manufacturing methods may be improved to further optimize battery performance and packaging. 
     Referring to  FIG. 1 , an electrochemical device, such as a solid-state battery, may include one or more electrochemical cells  100  having a substrate layer  102 , a cathode layer  104 , and an electrolyte layer  106 . There may also be a barrier layer as shown, between the cathode layer  104  and the substrate layer  102 . During fabrication of the electrochemical cell  100 , there may be a need to cut or remove material from one or more of the cell layers using a laser. 
     SUMMARY 
     It has been discovered that the high energy of typical lasers used during fabrication of electrochemical cells, e.g., operations to cut or remove cell materials, may generate heat that causes melting, reflowing, and redeposition of the sheet materials. More particularly, as depicted in  FIG. 2 , melted materials may be ejected or reflowed and redeposited onto an upper surface of the electrochemical cell  200  as ejected slag  202  or along the cut face as a slag layer  204 .  FIGS. 3A and 3B  provide magnified views of a cell surface after laser technology has been used to melt and cut away material. The figures illustrate a distinct ejected slag  202  that has redeposited onto the upper surface and a slag layer  204  along the cut face. 
     An issue caused by the ejected slag  202  that is formed over the electrolyte layer  106  is the risk that the slag layer  202  will become an electrical short between the cathode layer and the anode layer of a cell. This can be explained using  FIG. 4 , which is a partial side view of an electrochemical device  400 . The electrochemical device  400  may include the electrochemical cell  200  having ejected slag  202  over the electrolyte layer  106 . Furthermore, an anode layer  402  has been deposited over the electrolyte layer  106 . It can be seen that anode layer  402  may come close to making contact with the conductive slag layer  204  and ejected slag  202 . To avoid this, the anode layer  402  is masked away from an outer edge of the cell during deposition, so as to maintain a margin  404  between the ejected slag  202  and the anode layer  402 . 
     A problem with adding the margin  404 , however, is that it may cause underutilization of the electrochemical cell area, since it in effect creates a cathode area with no opposing anode area over the margin  404 . This can make the cathode layer  104  appear to have a virtual leak as the electrochemical device  400  goes through chemical equilibrium at rest. Thus, electrochemical device  400  having the margin  404  may have sub-optimal energy density. 
     Still referring to  FIG. 4 , the slag  202 ,  204  creates a further risk of electrical shorting when an anode current collector  406  is placed over the anode layer  402 . To avoid electrical shorting between the cathode layer  104  and anode current collector  406 , through the slag layer  204  and ejected slag  202 , a z-gap  408  is maintained in a vertical direction, i.e., in the direction of layer stacking. But the z-gap  408  may cause underutilization of space in the vertical direction, particularly in a case in which multiple electrochemical cells  200  are stacked to form the electrochemical device  400 . Thus, electrochemical device  400  having the z-gap  408  may have sub-optimal energy density. 
     In an embodiment, an electrochemical device may include a stack of two or more electrochemical cells, and at least one of the cells may include an insertion void, notch, slot, or other gap feature at an edge or side of the cell stack (cell sidewall), to receive a tab component, e.g., an anode current collector tab or a cathode current collector tab that makes electrical contact with the corresponding anode or cathode electrode. This may advantageously improve utilization of the available z-height for the battery stack, because the tab component now does not add to the z-height. 
     In an embodiment, an insertion void at an edge region of an electrochemical device permits insertion of an anode current collector tab that once inserted becomes electrically connected to respective anode layers of a pair of adjacent electrochemical cells. The electrochemical device includes a first electrochemical cell having a first electrolyte layer between a first anode layer and a first cathode layer in a stack direction. The first electrochemical cell may include an anode contact region and an anode current collector contact region, and the anode contact region may be offset in the stack direction from the anode current collector contact region. Furthermore, the electrochemical device may include a second electrochemical cell having a second electrolyte layer between a second anode layer and a second cathode layer. The second anode layer of the second electrochemical cell may face the first anode layer of the first electrochemical cell. For example, the first anode layer may touch or contact the second anode layer at the anode contact region. In an embodiment, the electrochemical device includes an anode current collector tab between the anode current collector contact region and the second electrochemical cell. The anode current collector tab may be disposed in a tab insertion space. The insertion void may be between the anode layers of the adjacent cells and have a distance in the stack direction between one anode and the anode current collector contact region of another anode. The distance may be at least as far as the offset between the anode contact region and the anode current collector contact region, and the anode current collector tab may fill the insertion void across the distance. The anode current collector tab may be physically located between the electrochemical cells, and furthermore, the respective anode layers of the electrochemical cells may be electrically connected to each other by the anode current collector tab. The anode current collector tab may physically contact the first anode layer, e.g., at the anode current collector contact region, and/or the second anode layer. 
     In an embodiment, an insertion void at an edge region of an electrochemical device, where two adjacent cells are connected, permits insertion of a cathode current collector tab that is electrically connected to the respective cathode layers of the two connected electrochemical cells. In an embodiment, the first electrochemical cell includes a first cathode layer between a first cathode current collector and the anode contact region of the first anode layer. The second electrochemical cell may include a second cathode layer between a second cathode current collector and the first anode layer. Furthermore, the first cathode current collector and the second cathode current collector may include respective exposed cathode current collector surfaces facing one another and not covered by the cathode layers or the anode layers. The exposed cathode current collector surfaces may be transversely offset from the anode contact region and the anode current collector contact region. In an embodiment, the cathode current collector tab is inserted between the exposed cathode current collector surfaces. 
     Rather than describing the gap feature that receives a tab in terms of an “insertion void,” etc., the device structure may also be described in terms of separation distances between corresponding cell regions, where the separation distance may be greater near an edge region of the device as compared to a middle region of the device, thereby allowing for a current collector tab to be inserted between the cells over the edge region without increasing the z-height of the device over the middle region. In an embodiment, an electrochemical device includes a first electrochemical cell and a second electrochemical cell, and each cell has a respective electrolyte layer between a respective anode layer and a respective cathode layer in a stack direction. The cells may be separated by a separation distance in the stack direction that varies along a transverse direction, and the separation distance may be greater near an outer perimeter of the cells than near a medial portion of the cells. For example, the separation distance over the outer region may be similar to a thickness of a current collector tab and the separation distance over the inner region may be essentially zero. In an embodiment, a transition region tapers, e.g., along a ramp, between the outer region and the inner region. The outer region may include an anode collector contact region and the inner region may include an anode contact region, and furthermore, the anode collector contact region may be electrically connected to the anode contact region. In an embodiment, one or more of the anode contact region or the anode collector contact region includes at least a portion of a respective anode layer. 
     In accordance with an embodiment of the invention, an electrochemical device having one or more cells includes a cell stack up that includes an electrolyte layer between an anode layer and a cathode layer. The stack up of the anode layer, the electrolyte layer, and the cathode layer defines a cell sidewall that has a non-zero, non-vertical slope (or simply, slope). In one embodiment, the cell sidewall is said to be sloped in an outward direction, in that a height of the cell sidewall diminishes versus increasing distance in an outward direction. The anode layer, the electrolyte layer, and the cathode layer may include respective sidewalls exposed along the cell sidewall. For example, the cell sidewall may extend from a top surface of the anode layer to the exposed cathode current collector surface, and the exposed sidewalls of the layers may be contiguous along the non-zero, non-vertical slope. Thus, the cell sidewall in that region may have a fixed or alternatively a smoothly changing slope. Examples include a cell sidewall whose slope does not become zero, or exhibits no discontinuity. In an embodiment, the non-vertical slope may include a linear portion. The non-vertical slope may also include a curvilinear or nonlinear slope portion, instead of, or in addition to, the linear slope portion. The electrochemical cell may include additional layers in the cell stack, e.g., a cathode current collector, and the additional layers may include respective exposed sidewalls. For example, a cathode current collector may include an exposed sidewall that is contiguous with the other exposed sidewalls of the stack layers along the non-zero, non-vertical slope of the cell sidewall. The cell sidewall may extend from the top surface of the anode layer to a terminal edge on any other layer, e.g., the terminal edge may be on the cathode current collector at a location vertically offset from a top surface of the cathode current collector, and the exposed sidewall of the cathode current collector may extend between the top surface and the terminal edge. 
     In an embodiment, the cell sidewall having a non-zero, non-vertical slope may be contiguous in that the edges of the adjacent constituent layers of the cell are coincident. For example, the electrolyte sidewall may extend between an electrolyte top edge and the cathode layer, where the electrolyte top edge may be coincident with a bottom edge of the anode. Another way to describe a cell sidewall as having a non-zero, non-vertical slope is one whose anode bottom edge is laterally offset from the anode top edge, for example in an outward direction. 
     The sloped sidewall may be obtained by using a controlled, ablation process that limits the creation of heat during cutting across the various layers of the cell, to thereby avoid formation of the slag layers mentioned above. For example, the ablation process may be performed using an ablation laser to result in the cut cell having a sloped sidewall, and one that advantageously may be devoid of a slag layer, thereby avoiding the need for adopting the limited solutions described above (that cause under utilization of the electrochemical cell area). 
     As mentioned above, a controlled laser ablation process that limits the creation of heat during cutting may be used to fabricate the various cell and device architectures described below. In an embodiment, a method includes setting an intensity of a laser beam to a level less than required to melt one or more layers of an electrochemical cell. For example, setting the intensity may include setting a power of the laser beam and defocusing the laser beam to achieve the intensity. The method may also include lasing the one or more layers of the electrochemical cell with the laser beam to remove material from the cell layers and expose layer sidewalls along the cell sidewall having a non-zero, non-vertical slope. 
     The above summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the Detailed Description below and particularly pointed out in the claims filed with the application. Such combinations have particular advantages not specifically recited in the above summary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a sheet of multi-layered material used to manufacture an electrochemical cell. 
         FIG. 2  is a side view of an electrochemical cell. 
         FIGS. 3A-3B  are magnified views of an electrochemical cell, illustrating the redeposition of slag from the cut material. 
         FIG. 4  is a partial side view of an electrochemical device. 
         FIG. 5  is a side view of an electrochemical cell in accordance with an embodiment. 
         FIG. 6  is a side view of an electrochemical cell having a non-vertical sloped sidewall in accordance with an embodiment. 
         FIG. 7  is a side view of several singulated electrochemical cells formed from a sheet of multi-layered material in accordance with an embodiment. 
         FIG. 8  is a detail view, taken from Detail A of  FIG. 7 , of an edge of a singulated electrochemical cell in accordance with an embodiment. 
         FIG. 9  is a top view of an electrochemical device having current collector tabs in accordance with an embodiment. 
         FIG. 10  is a cross-sectional view, taken about line A-A of  FIG. 9 , of an electrochemical device having an anode current collector tab in accordance with an embodiment. 
         FIG. 11  is a cross-sectional view, taken about line B-B of  FIG. 9 , of an electrochemical device having a cathode current collector tab in accordance with an embodiment. 
         FIGS. 12-21  are various views of an electrochemical device having current collector tabs shown at different stages of a manufacturing process in accordance with an embodiment. 
         FIG. 22  is a top view of two electrochemical cells prior to being stacked to form an electrochemical device in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Structures and manufacturing methods for solid-state batteries are described. However, while some embodiments are described with specific regard to manufacturing processes or structures for integration within a solid-state battery, the embodiments are not so limited, and certain embodiments may also be applicable to other uses. For example, one or more of the embodiments described below may be used to manufacture other layered elements, such as silicon-based solar cells. 
     The following description is with reference to the figures. However, certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations. In the following description, numerous specific details are set forth, such as specific configurations, dimensions, and processes, in order to provide a thorough understanding of the embodiments. In other instances, well-known processes and manufacturing techniques have not been described in particular detail in order to not unnecessarily obscure the description. Reference throughout this specification to “one embodiment,” “an embodiment,” or the like, means that a particular feature, structure, configuration, or characteristic described is included in at least one embodiment. Thus, the appearance of the phrase “one embodiment,” “an embodiment,” or the like, in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, configurations, or characteristics may be combined in any suitable manner in one or more embodiments. 
     In one aspect of the invention, an electrochemical cell includes several layers having respective sidewalls that combine to form a cell sidewall. Furthermore, the cell sidewall may include a non-vertical slope. For example, the cell sidewall may taper along the respective layer sidewalls, e.g., between an anode layer, an electrolyte layer, and a cathode layer, such that a height of the cell sidewall diminishes in a transverse direction outwardly from a top surface of the anode layer. The transverse direction may be distinguished from a stack direction (or a vertical direction), in that the transverse direction may be essentially orthogonal to the stack direction. Thus, the transverse direction may be considered to radiate perpendicular to stack axis  1014 . An outward direction may be a direction away from a centerline or middle region of an electrochemical cell or electrochemical device. Thus, an outward transverse direction is orthogonal to stack axis  1014  located along a centerline of the cell or device. Accordingly, the respective sidewalls of the electrochemical cell layers may be contiguous, i.e., the edges of each layer of the electrochemical cell are coincident with edges of a next adjacent layer, thereby forming a contiguous cell sidewall. The non-vertical slope of the cell sidewall may have planar and/or curvilinear portions. Thus, the sloping cell sidewall may provide for a cathode layer that is essentially entirely covered by the anode layer, and thus, electroactive portions of the cell may be maximized and energy density of the electrochemical cell may be improved. 
     In another aspect, an electrochemical device having two electrochemical cells is provided. In an embodiment, the electrochemical cells are fabricated to include one or more recesses to receive a current collector. In an embodiment, both cells include one or more recesses, and in another embodiment, only one of the two cells includes one or more recesses. As a result of the recesses, a separation distance between the cells in a vertical direction varies over a transverse direction. For example, the separation distance between the cells over the recess area near an outer portion of the electrochemical cells may be greater than the separation distance between the cells near a medial portion of the cells. In an embodiment, a transition region such as a tapered region may be formed between the recessed region and the non-recessed regions. Furthermore, the recesses may include a portion of an anode layer or an exposed cathode current collector, i.e., a cathode current collector uncovered by other layers of the cell prior to insertion of a current collector tab, and the recessed regions may be placed in electrical connection with respective anode or cathode material near the medial region of the cell stack. More particularly, at least one of the electrochemical cells may include an anode collector contact region that is vertically offset in a vertical direction from an anode contact region of the electrochemical cell. Thus, when the electrochemical cells are apposed to one another, the recesses form a gap to facilitate insertion of an anode current collector tab to make electrical contact with the anode layers or to facilitate insertion of a cathode current collector tab to make electrical contact with the substrate layers. The gap may be filled entirely by the tabs, and in an embodiment, the tabs may be encompassed within the outer boundary of the electrochemical cells, to provide for a square or rectangular electrochemical device profile when viewed from above. This efficient packaging of the tabs within the electrochemical device provides for optimized energy density and a more compact form factor for improved product packaging. 
     Referring to  FIG. 5 , a side view of an electrochemical cell is shown in accordance with an embodiment. The electrochemical cell  500  may include an electrolyte layer  508  between an anode layer  510  and a cathode layer  506 . The cathode layer  506  may, for example, include LiCoO2, LiMn2O4, LiMnO2, LiNiO2, LiFePO4, LiVO2, or any mixture or chemical derivative thereof. The electrolyte layer  508  may facilitate ion transfer between the cathode layer  506  and the anode layer  510 . Accordingly, the electrolyte layer  508  may be a solid electrolyte, which may not contain any liquid components and may not require any binder or separator materials compounded into a solid thin film. For example, the electrolyte layer  508  may include lithium phosphorous oxynitride (LiPON) or other solid state thin-film electrolytes such as LiAlF 4 , Li 3 PO 4  doped Li 4 SiS 4 . The anode layer  510  may, for example, include lithium, lithium alloys, metals that can form solid solutions or chemical compounds with lithium, or a so-called lithium-ion compound that may be used as a negative anode material in lithium-based batteries, such as Li 4 Ti 5 O 12 . 
     In an embodiment, the cathode layer  506  may be electrically connected with a cathode current collector  504 , which may be an electrically conductive layer or a tab. Similarly, the anode layer  510  may be electrically connected with an anode current collector, which may be an electrically conductive layer or a tab. Optionally, one or more intermediate layers may be disposed between the cathode layer  506  or the anode layer  510  and a respective current collector. For example, a barrier film layer  502  may separate the cathode layer  506  from the cathode current collector  504 . For example, the barrier film layer  502  may be in direct physical contact with the cathode layer  506  and the cathode current collector  504 . The barrier film layer  502  may reduce the likelihood of contaminants and/or ions from diffusing between the cathode current collector  504  and the cathode layer  506 . Thus, the barrier film layer  502  may include materials that are poor conductors of ions, such as borides, carbides, diamond, diamond-like carbon, silicides, nitrides, phosphides, oxides, fluorides, chlorides, bromides, iodides, and compounds thereof. Alternatively, an additional intermediate layer, such as a substrate layer, e.g., substrate layer  102 , may be disposed between the cathode layer  506  and the cathode current collector  504 . The substrate layer may, for example, provide electrical connectivity between the cathode layer  506  and the cathode current collector  504  and may also provide structural support, e.g., rigidity, to the electrochemical cell  500 . Accordingly, the substrate layer may include a metal foil or another electrically conductive layer. 
     In some instances, the electrochemically active layers of the cell may be formed on one side of the substrate layer, e.g., using material deposition techniques such as physical vapor deposition, and the cathode current collector  504  may be formed separately and physically coupled to another side of the substrate layer. In other instances, the electrochemically active layers of the cell may be formed on the substrate layer, and then the electrochemically active layers may be removed from the substrate layer and physically coupled to the separately formed cathode current collector  504 . In still other instances, the electrochemically active layers of the cell may be formed, e.g., physical vapor deposited, directly on the cathode current collector  504 . Thus, there are many different ways to create an electrochemical cell  500  having several electrochemically active layers. 
     The layers of the electrochemical cell  500  may be thin. For example, the cathode current collector layer  504  may have a thickness in a range of between 10 to 100 μm, e.g., 50 μm. The composite electrochemical cell  500  may have a total thickness in a range of between 13 to 300 μm. For example, the barrier film layer  502 , cathode layer  506 , electrolyte layer  508 , and anode layer  510  may combine to have a thickness in a range of between 3 to 290 μm, e.g., 25 μm. 
     In an embodiment, an electrochemical cell  500  may be provided that includes every layer of electrochemical cell  500 . More particularly, the electrochemical cell may include cathode current collector  504 , barrier film layer  502 , cathode layer  506 , electrolyte layer  508 , and anode layer  510 . During fabrication, the layers may be cut using conventional laser technology to melt through the layers. Accordingly, a slag layer  512  may be redeposited along the laser cut outer edge of electrochemical cell  500 . 
     Referring to  FIG. 6 , a side view of the electrochemical cell of  FIG. 5  is shown, having a non-vertical sloped sidewall in accordance with an embodiment of the invention. In an embodiment, the electrochemical cell  500  may have material removed to form a cell sidewall  601 . For example, a portion of the electrochemical cell  500  may be ablated, etched, skived, ground, etc., using “cold cutting” technologies that remove material. Cold cutting is a term that is used broadly to refer to methods that can cut or remove material without melting the materials, but conceivably, slope cell sidewall  601  may be achieved using other cutting methods that employ material melting, and thus, cold cutting is not intended to be limiting of the invention. Nonetheless, the viable options for selectively and controllably eliminating material without melting include laser ablation, which is to be distinguished from laser cutting that produces slag layer  512 . More particularly, in a laser ablation process, a low-energy, short wavelength, and/or defocused laser beam may remove portions of one or more layers of material from the electrochemical cell  500  without melting and redepositing slag. As a result of the laser ablation process, at least a portion of the resulting slag layer  512  may be removed across the cut surface as seen in  FIG. 6 , thereby reducing the likelihood of electrical shorting between cell layers, e.g., the anode layer  510  and the cathode layer  506 . 
     The cell sidewall  601  may be formed along the cut surface. In an embodiment, the cell sidewall  601  includes respective sidewalls of one or more layers of the electrochemical cell  500 . For example, the cell sidewall  601  may extend along a non-zero, non-vertical slope between a top surface  620  of the anode layer  510  to (and optionally including portions of) the cathode current collector  504 . That is, the cell sidewall  601  may extend outwardly from anode top edge  602  of top surface  620  to a terminal edge  603 . Terminal edge  603  may represent a location at which the taper of cell sidewall ends and a lateral side of electrochemical cell transitions to an infinite, vertical slope. For instance, terminal edge  603  may coincide with slag layer top edge  604 , which is an upper location along the vertical wall formed by laser cutting electrochemical cell  500 . Thus, in an embodiment, the cell sidewall  601  may include a non-vertical slope between a top edge, e.g., anode top edge  602  and a bottom edge, e.g., terminal edge  603  coinciding with slag layer top edge  604 . That is, the cell sidewall  601  may be sloped and a height (in a vertical direction) of the cell sidewall  601  diminishes along a transverse direction orthogonal to the vertical direction. More particularly, the cell sidewall  601  height may diminish in a transverse direction outwardly from an anode top surface having the anode top edge  602  toward the terminal edge  603 . The height of the cell sidewall  601  may diminish at a higher or lower rate, however, in an embodiment, the cell sidewall  601  includes a non-vertical slope and the diminution of the height does not occur at an infinite rate as in the case of a vertical sidewall. 
     Given that the slope of cell sidewall  601  may vary, and also given that cell sidewall  601  may be formed by removing material from electrochemical cell  500  using an ablation process that can be varied to ablate the cell to a desired depth, it will be appreciated that terminal edge  603  of cell sidewall  601  may be located along a sidewall of any of the constituent layers of electrochemical cell  500 . For example, cathode current collector  504  may have a top surface  650  electrically connected to cathode layer  506  (cathode layer  506  may be over the top surface  650  and on cathode current collector  504 ). By varying the depth that material is removed using an ablation process, terminal edge  603  may terminate at locations more or less offset from the top surface  650  of cathode current collector  504 . For example, as shown in  FIG. 6 , terminal edge  603  may be offset in the vertical direction from top surface (and below top surface  650 ). When terminal edge  603  is below top surface  650  along cell sidewall  601 , the cathode current collector includes a cathode current collector sidewall  652  that is exposed due to the removal of material using the ablation process. The cathode collector sidewall  652  may be contiguous with the other exposed sidewall portions, as described below, to form the non-zero, non-vertical slope of cell sidewall  601 . 
     Less material may be removed during the ablation process to form a shallower cut. Accordingly, the terminal edge may coincide with top surface  650 . That is, cell sidewall  601  may extend along a non-zero, non-vertical slope from anode top edge  602  to terminal edge  603  at top surface  650 . In such case, since the ablation cut does not extend below top surface  650  of cathode current collector  504 , electrochemical cell  500  may lack a cathode current collector sidewall  652 . 
     In an embodiment, cathode current collector  504  includes a bottom surface  660  below top surface  650 . Furthermore, the ablation process may be varied to remove material across an entire cell height  700  (see  FIG. 7 ) of electrochemical cell  500 . That is, as shown in  FIG. 7 , cut trough  702  may be driven through electrochemical cell  500  to form cell sidewall  601  extending from anode top edge  602  at anode top surface  620  to terminal edge  603  at bottom surface  660 . Thus, cell sidewall  601  may include an exposed cathode current collector sidewall  652  sloping from top surface  650  to terminal edge  603  at bottom surface  660 , as shown in  FIG. 7 . 
     In an embodiment, as shown below in the electrochemical device embodiments of  FIGS. 10-11 , terminal edge  603  may be a transition point at which cell sidewall  601  changes to a zero, horizontal slope. For example, cell sidewall  601  may slope from anode top edge  602  to terminal edge  603  below top surface  650  of cathode current collector  504 . Accordingly, cell sidewall  601  may include the exposed sidewalls of anode layer  510 , electrolyte layer  508 , cathode layer  506 , and cathode current collector  504 . The ablation cut depth may be shallower, however, than cell height  700 , and thus, a horizontal upper surface is formed at the bottom of the ablation cut. This horizontal upper surface (indicated, in an embodiment, as exposed cathode current collector surface  1102  in  FIG. 11 ) may extend from terminal edge  603  to a lateral side of cathode current collector  504 . As such, rather than being a point at which cell sidewall  601  transition to a vertical surface (e.g., the lateral surface apposed with slag layer  512  in  FIG. 6 ) or a point at which cell sidewall  601  transitions to bottom surface  660  (see  FIG. 7 ), terminal edge  603  may be a point at which cell sidewall  601  along a side of an ablation cut transitions into a horizontal surface along a base of the ablation cut. 
     In an embodiment, the cell sidewall  601  is contiguous across its length. For example, in an embodiment, the cell sidewall  601  tapers between the anode top edge  602  and the slag layer top edge  604 , as seen in  FIG. 6  (which shows an exaggerated taper). The respective sidewalls of the anode layer, electrolyte layer, and cathode layer along the non-vertical slope may be partially or wholly planar. Accordingly, the non-vertical slope may include a linear slope portion. Thus, a slope of cell sidewall  601  may be consistent across all layers of electrochemical cell  500 . That is, the ablated wall having the slope, i.e., cell sidewall  601 , may have a continuous and linear slope from anode top edge  602  to slag layer top edge  604 . 
     Rather than having a continuous and linear slope, as shown by a dotted line in  FIG. 6 , the non-vertical slope may be contiguous but instead have a curvilinear portion. For example, curvilinear slope portion  606  may follow a curvilinear path, e.g., an arc, between the anode top edge  602  and the slag layer top edge  604 . In an embodiment, the curvature or shape of the cell sidewall  601  may be controlled by defocusing a laser beam used for ablation. For example, the laser beam may be defocused to cause a taper of an ablated sidewall to have a taper run, i.e., a distance covered by the cell sidewall  601  in a direction orthogonal to the vertical direction, of between 5-50 μm, e.g., 20 μm. The laser beam intensity and focus may be controlled to create any range of cut surface geometries. 
     Given that the ablated surface of cell sidewall  601  may be contiguous, each layer of the electrochemical cell  500  may include a top edge and a bottom edge, and the top edge of a first layer may be coincident with the bottom edge of a second layer stacked over the first layer. For instance, the anode layer  510  may have an anode sidewall  610  between the anode top edge  602  and the anode bottom edge  608 . Furthermore, the anode layer bottom edge  604  may be laterally offset, i.e., in a transverse direction orthogonal to a vertical direction and outwardly away from a top surface of the anode top surface and the anode top edge  602 . Similarly, the electrolyte layer  508  between the anode layer  510  and the cathode layer  506  may have an electrolyte sidewall  612  between an electrolyte top edge  614  and an electrolyte bottom edge  616 , e.g., at the cathode layer  506 . In an embodiment, the electrolyte top edge  614  is coincident with the anode bottom edge  608 , which may make a smooth transition between the sidewalls of the two layers. It is to be understood that a smooth transition does not imply that a tangent of the respective merging sidewalls are parallel, but rather, one sidewall may be angled with respect to the other sidewall. If the edges of the sidewalls are essentially coincident at the transition between layers, then the transition may be considered to be smooth. Similarly, a top edge of the cathode layer  506  may be coincident with the electrolyte bottom edge  616 , and so on. Accordingly, the sidewalls of all layers are contiguous and continuous over the ablated, or otherwise formed, cell sidewall  601  surface. Referring to  FIG. 7 , a side view of several singulated electrochemical cells formed from a sheet of multi-layered material is shown in accordance with another embodiment of the invention. This structure may be, but is not necessarily, the result of a low-energy, short wavelength, and/or defocused laser beam having been used to cut fully through a multilayered sheet of material, but without melting and redepositing the material to create the slag layer  512 . In other words, rather than singulating the electrochemical cells  500  by melting through the sheet with a typical laser cutting process and then ablating the sidewalls to remove the slag layer  512 , the sheet may instead be singulated using a cold cutting technology, e.g., a laser ablation process, that removes material without melting and redepositing the material in the first place. The sheet of multi-layered material may be singulated using an ablation laser, e.g., a laser that has been tuned for ablation rather than for cutting. The intensity of the laser beam may also be adjusted to reduce the taper angle shown in the figure, while driving a cut trough  702  fully through the sheet, from the anode layer  510  down through the cathode current collector  504 . Such cutting through ablation, rather than melting, may mitigate or even reduce the likelihood of slag redeposition along the resulting cut edge and also the top surface of the singulated cells. The cutting tool, e.g., a laser beam, may be used to generate a gap between adjacent cell sidewalls where material has been removed. Furthermore, the gap may be defined between the cell sidewalls  601 , and each cell sidewall  601  may include a non-vertical sloped surface, e.g., the slope may include at least a planar or curvilinear slope portion. Note that ablation is only one manner of creating a contiguous sloped surface without melting and redepositing the cut or removed material, and thus, is not limiting of the invention. Furthermore, other embodiments may allow for typical laser cutting technologies to melt through layers of an electrochemical cell and to still create the non-vertical sloped sidewall surface described herein. 
     Referring to  FIG. 8 , a detail view, taken from Detail A of  FIG. 7 , of an outer edge of a singulated electrochemical cell is shown. The cut may leave a contiguous taper from the anode top edge  602  through every layer from the anode layer  510  down through the cathode current collector  504 . A slope of cell sidewall  601  along the ablation cut may be consistent across all layers of electrochemical cell  500 . That is, the ablated wall having the slope, i.e., cell sidewall  601 , may have a continuous and linear slope from anode top edge  602  to a bottom edge of the layer forming cathode current collector  504 . Thus, each layer of the singulated electrochemical cell  500  may include a sidewall that transitions smoothly into an adjacent layer sidewall. In an embodiment, for each layer sidewall the top and bottom edges are coincident with adjacent sidewall edges, meaning that there may be essentially no discontinuity as the sidewalls transition from one layer to the next. This is in contrast to what is shown in  FIG. 4 , where a margin  404  is formed between the sidewalls of the adjacent anode layer  402  and electrolyte layer  106 . 
     As a result of the processes and electrochemical cell structures described above, a proportion of the cathode layer  506  having anode layer  510  overlying it, may be increased. The proportion may vary based on an angle of the sidewall slope, but for any given slope angle, the proportion may be maximized. That is, for any given sidewall slope, the anode layer  510  may extend fully to a lateral edge of the electrochemical cell  500 , i.e., there may be little or no margin between an electrolyte sidewall  612  and an anode sidewall  610 . For example, any margin or lateral offset between the sidewalls  610 ,  612  may be less than a thickness of the anode layer  510 , e.g., less than 20 μm. Thus, the electrochemical cell surface area in a direction orthogonal to the vertical direction may be essentially fully utilized and anode area may be maximized. More particularly, the electrochemical cell  500  may have a structure in which practically the entire cathode layer  506  is apposed by an anode layer  510  across from the electrolyte layer  508  as a result of the sidewall having a contiguous slope between the cathode layer  506  and the anode layer  510 . Thus, a bottom surface area of an anode area may be essentially equal to an upper surface area of the cathode layer  506 , the difference being determined by the sidewall slope between the areas, resulting in substantially no virtual leak observed in the cathode as the electrochemical cell  500  goes through chemical equilibrium at rest. By maximizing the proportion of cathode having anode overlying it in this way, an increase in performance of up to 20% may be achieved over masking methodologies that form a margin between the anode and cathode edges, as described with respect to  FIG. 4  above. In addition to improving battery performance, a contiguous sidewall surface with a maximized anode surface area may also be more manufacturable, since no masking is required. In the case of singulating electrochemical cells using a cold cutting technology, e.g., laser ablation, as opposed to masking and laser cutting, cut trough may have closer tolerances or be narrower than may be achieved with masking. This may reduce material waste and manufacturing cost, as compared to existing masking and patterning techniques, which are generally too flimsy or time-consuming to achieve such thin cut troughs  702 . 
     As described above, in an embodiment, cold cutting to singulate an electrochemical cell  500  from a sheet of multi-layered material, or to pattern or ablate the electrochemical cell  500 , e.g., to remove the slag layer  512  to reduce the likelihood of shorting between layers, may be achieved using an ablation laser. A laser beam in a wavelength spectrum below 550 nm may be used to ablate and remove material from the sheet or electrochemical cell  500 . For example, a green or ultraviolet wavelength laser beam having a wavelength of 530 nm may be used to ablate the one or more layers of electrochemical cell  500 . Furthermore, an intensity of the short wavelength laser beam may be controlled to reduce the likelihood of melting of the material layers. That is, the intensity of the laser beam may be controlled to generate heat that is absorbed in the multilayered material, causing ablation of the material rather than melting of the material. In an embodiment, laser beam intensity may be controlled by adjusting a power setting of the laser beam. 
     Intensity of the laser beam used to ablate the multilayered sheet may also be controlled by adjusting a focal area of the laser beam. More specifically, the laser beam may be defocused. Accordingly, the focal area at the surface of the multilayered sheet is increased, thereby reducing laser beam intensity at a given point. In an embodiment, defocusing the laser beam changes the geometry of the resulting cut surface, and thus, the cell sidewall  601  slope angle or shape. For example, as the laser beam is further defocused, a taper angle of the cell sidewall  601  may increase. That is, defocusing the laser beam may create a larger taper run. 
     Referring to  FIG. 9 , a top view of an electrochemical device having current collector tabs is shown in accordance with an embodiment. In an embodiment, an electrochemical device  900  may be manufactured to include current collector tabs, e.g., an anode current collector tab  902  and a cathode current collector tab  904 . More particularly, an electrochemical device  900  may be formed that includes at least two electrochemical cells  500 . In an embodiment, each electrochemical cell  500  includes an anode layer  510 , an electrolyte layer  508 , a cathode layer  506 , and a cathode current collector  504 , as described above. Each cell may, but need not, maximize the proportion of cathode area having an anode area overlying it, by incorporating a contiguously sloped sidewall having essentially no margin between layers that are immediately next to one another. In an embodiment, the architecture includes tabs that can fit within an outer boundary of the electrochemical cell  500 , e.g., within a square or rectangular cell profile when viewed from above. This fit provides for efficient packaging that may be more easily incorporated into products. In an embodiment, separation spaces  906  may be provided between the tabs  902 ,  904  and an adjacent cell body  908  to reduce the likelihood that electrical and/or ionic shorting will occur between the sides of the tabs and any of the layers, e.g., a sidewall of the anode layer, cathode layer, or electrolyte layer, that may be exposed and facing the tab sides. 
     Referring to  FIG. 10 , a cross-sectional view, taken about line A-A of  FIG. 9 , of an electrochemical device having an anode current collector tab is shown. In one embodiment, the electrochemical device  900  includes a stack of electrochemical cells  500 . For example, a first electrochemical cell  1002  may be inverted and stacked on a second electrochemical cell  1004  such that respective anode layers  510  of the electrochemical cells  1002 ,  1004  face one another. 
     In an embodiment, the electrochemical device  900  includes an insertion void  1006  to receive an anode current collector tab  902  between the anode layers  510 , without increasing z-height of the assembled device. More particularly, the electrochemical cells  500  may be formed such that after assembly, a gap or opening is provided near an edge of the electrochemical device  900  to receive the anode current collector tab  902 . The anode layers  510  over the majority of the electrochemical device&#39;s transverse area, e.g., over a medial portion of the electrochemical device, may be either adjacent or abutted with one another. For example, the anode layers may be immediately next to each other, e.g., in physical contact with each other, over at least a portion of their respective areas. Alternatively, there may be a thin separation layer between the anode layers, such as an electrically and/or ionically insulating layer. The separation layer may have a thickness less than a height of gap or opening provided to receive the anode current collector tab  902 . Thus, in an embodiment, z-height may be reduced, even though it may not be reduced to zero. In addition to reducing z-height, the device architecture may allow for thicker tabs to be used, which may increase the robustness of the tabs and make electrical and physical connections to external components more reliable. 
     Each electrochemical cell  500  may include an anode current collector contact region  1012  near an outer perimeter or sidewall. The anode current collector contact regions  1012  may be separated by a distance in the stack direction sufficient to receive anode current collector tab  902 . For example, anode current collector tab  902  may be inserted such that a distal end extends inward from the sidewall of the cells. The inner surface of the cells along the anode current collector contact region  1012  may transition, e.g., taper, over a transition region  1010 . That is, in an embodiment, top surface  620  of respective anode layers  510  of the stacked electrochemical cells may taper along a non-zero, non-vertical slope across transition region  1010 . More particularly, the separation between cell inner surfaces may reduce over the transition region  1010 . As a result, a gap may exist between inner surfaces of the cells over transition region  1010 , since the anode current collector tab  902  may be thicker than the separation distance, and thus, not extend into the transition region. Note that the taper over the transition region  1010  as shown in  FIG. 10  is exaggerated, and that a taper run of the transition region may be a fraction of the taper rise. In an embodiment, the taper may be essentially vertical, but may include a non-zero slope, such that the transition region  1010  is very small, and the anode current collector contact region  1012  is essentially directly next to the anode contact region  1008 . 
     Note that the taper over transition region  1010  may include a vertical rise, and thus, the anode contact region  1008  of each electrochemical cell may be offset in the stack direction from the respective anode current collector contact region  1012  of the cell. Over the anode contact region  1008 , a separation between the inner surfaces of the cells may be less than over the anode current collector contact region  1012 . That is, the cells may be separated less over a medial portion, i.e., inward from the transition region  1010 , than over an edge region, i.e., over the anode current collector contact region  1012 . In one embodiment, a separation distance between the inner surfaces of the cells over the anode contact region  1008  may be essentially zero and the separation distance between the inner surfaces of the cells over the anode current collector contact region  1012  may be equal to a thickness of the anode current collector  902 . Thus, an insertion void may be formed between cells over both anode current collector contact region  1012  and transition region  1010 . Accordingly, the respective anode layers over the anode contact region  1008  may be directly in electrical contact. Alternatively, the anode layers may be placed in electrical contact through an electrically conductive material that is also running in a same direction as one or more of the anode layers over the anode contact region  1008 , e.g., horizontally or transversely. 
     In an embodiment, the separation between the inner surfaces of the cells over the anode current collector contact region  1012  may be formed by removing a portion of one or more of the respective cathode layers  506  of first electrochemical cell  1002  and second electrochemical cell  1004 . More particularly, the cathode material may be removed at the periphery of the cell to make space for the anode current collector tab  902 . Another way to describe this is that a notch or slot has been formed in a cell sidewall where at least two stacked cells are joined. Forming such a gap feature may result in the inner surface of the cell, which is located in the notch, to be lined with anode layer material that is electrically in contact with both of the respective cell anode layers  510  (and an anode current collector tab  902  placed within the gap feature may therefore be in contact with those anode layers). 
     For completeness of understanding of the above description, another way to describe an embodiment of the electrochemical device  900  is as follows. While the anode layer, the electrolyte layer, and the cathode layer, in a conventional structure, all run horizontally outward, essentially as transverse layers, until they end at the same distance, thereby defining a vertical cell sidewall as seen in  FIG. 5  for example, the cathode layer  506 , in accordance with an embodiment of the invention, stops short (does not run all the way out to the cell sidewall as otherwise defined by the side or periphery of a substrate). This in effect creates a gap in the cell sidewall (making up all or part of an insertion void  1006 ). The electrolyte layer  508  and the anode layer  510 , however, continue to run and conform to the surface of the cathode  506  in the gap, as seen in  FIG. 10 . The gap need not have any particular shape, but it may be large enough to allow an anode current collector tab  902  to be positioned at least partially inside so as to make electrical contact with the anode layers  510 . The anode current collector tab  902  may therefore fill the insertion void  1006  between the anode current collector contact regions  1012  of the anode layers, i.e., may fill a distance in the stack direction between the anode current collector contact region on an anode layer and a top surface of an opposing anode layer. 
     It will be appreciated that the embodiment represented in  FIG. 10  illustrates a “balanced” insertion void  1006 , when equal amounts of cathode layer  506  are absent over an edge region of the stacked cells. However, the contribution to the insertion void  1006  may alternatively be imbalanced, where, for example, only the cathode layer  506  of first electrochemical cell  1002  is absent or notched out over the edge region (which may encompass the anode current collector contact region  1012  and the transition region  1010 ) while the other cathode layer  506  of second electrochemical cell  1004  (and its anode layer  510  and electrolyte layer  508 ) may extend continuously transverse across those regions, i.e., without showing any vertical offset. Accordingly, an anode current collector  902  with half the thickness may still fit within such an imbalanced insertion void  1006 . In the case of either a balanced or an imbalanced insertion void  1006 , the insertion void  1006  may have a distance, e.g., a height in the stack direction of stack axis  1014 , that is at least as far as the offset in the stack direction between the top surface  620  along anode contact region  1008  and the top surface  620  along anode current collector contact region  1012 . 
     The anode current collector tab  902  may be inserted into the insertion void  1006  and physically coupled with the inner surface of the cells over the anode current collector contact region  1012 . For example, anode layers  510  of the electrochemical device may extend over the anode current collector contact region, and thus, the anode layers  510  may be bonded to the anode current collector  902 . A physical connection between the anode current collector tab  902  and the anode layers  510  may be made in various manners, including by using an adhesive, e.g., a conductive pressure sensitive adhesive, to create an adhesive bond between surfaces of the physically connected components. Alternatively, a friction fit between the anode current collector tab  902  and the anode layers  510  may be formed. Furthermore, other techniques, such as thermal welding of the anode current collector tab  902  to the anode layers  510  may be used. 
     In an embodiment, only one of the electrochemical cells in an electrochemical device  900  includes anode current collector contact region  1012  offset from the anode contact region  1008 . That is, a recess may be formed in only one electrochemical cell to provide an insertion gap  1006  for insertion of an anode current collector tab  902 . Furthermore, it is not necessary that one or more layers of the electrochemical cells extend fully to the perimeter of the cell, as shown in  FIG. 10 . For example, one or more of the respective anode layers  510  in the electrochemical device  900  may not extend fully over the anode contact region  1008  and the anode current collector contact region  1012 . For example, the anode layer  510  may extend over the anode contact region  1008  without also extending over the transition region  1010  or the anode current collector contact region  1012 . Nonetheless, electrical contact may be made between those regions to permit an inserted anode current collector tab  902  to be electrically connected to an anode layer  510  over a portion of the anode contact region  1008 . For example, an electrically conductive layer, lead, via, etc., may be used to form an electrical connection between the anode current collector contact region  1012  and the anode material within the anode contact region  1008 . Thus, illustration of the anode layer  510  extending fully between and over regions  1008 ,  1012  over transition region  1010  is not intended to be limiting of the invention. Rather, electrochemical cells with different architectures may be used if a separation distance between the electrochemical cells is higher over a region  1012  than at a region  1008  to allow for insertion of a current collector tab without increasing z-height. 
     Referring to  FIG. 11 , a cross-sectional view, taken about line B-B of  FIG. 9 , of an electrochemical device having a cathode current collector tab is shown in accordance with an embodiment. In an embodiment, the electrochemical device  900  includes an insertion void  1006  to receive a cathode current collector tab  904 , between the cathode current collectors  504 , without increasing z-height of the assembled device. More particularly, the electrochemical cells  500 , i.e., first electrochemical cell  1002  and second electrochemical cell  1004 , may be formed such that after assembly, a gap or opening is provided near a perimeter region of the electrochemical device  900  that receives the cathode current collector tab  904 . The gap or opening may be the result of vertically recessed surfaces in one or both of the mating electrochemical cells  1002 ,  1004 . That is, one or both of the electrochemical cells  1002 ,  1004  may include recessed substrate surfaces  1102  as described further below. Thus, each electrochemical cell  500  may include respective exposed cathode current collector surfaces  1102  facing one another and located laterally outside of the various other layers of the cell. The cathode current collector surfaces  1102  facing one another to make electrical contact with an inserted current collector are exposed because they may not be covered by the other layers of the electrochemical cell  500 . The various other layers, e.g., the barrier film layer  502 , the cathode layer  506 , the electrolyte layer  508 , and the anode layer  510 , of each electrochemical cell  500  in the stack, may include a cell sidewall  601  that is contiguous, and may include a non-zero, non-vertical slope, as described above. Thus, the cathode layer  506  may be essentially fully covered by an overlying anode layer  510  to increase energy density. The cathode current collector tab  904  may be inserted into the insertion void  1006  and bonded to the cathode current collectors  504  of the electrochemical device using, e.g., a conductive pressure sensitive adhesive. The cathode current collector tab  904  may contact the exposed surface of the cathode current collectors  504 , i.e., may be in direct contact with the cathode current collectors  504 , to facilitate electrical conductivity therebetween. Furthermore, the cathode current collector tab  904  may fill the insertion void  1006  to fully utilize lateral and vertical space within the electrochemical device. This may allow for the tab to fit within the outer boundaries of the stack. It should be clarified that by fitting within the outer boundaries of the stack, it is meant that the tab may extend outward and away from a contact point between cells of the electrochemical device  900  and that the shape of the tab fills in or defines an outer boundary of the stack that may be recognized as a simple shape. For example, without the tabs in place, the stack may be recognized from above as having a square profile with notched corners, but upon insertion of the tabs, the stack may be recognized as a having a square profile. However, a square profile is provided by way of example only, and in other instances, insertion of the tabs may define an outer boundary of the electrochemical device  900  having any general shape, e.g., any regular convex polygon shape. Accordingly, in an embodiment, an electrochemical device having tabs and an outer boundary with a square profile is achieved. 
     Advantageously, an electrochemical device having architecture as illustrated in  FIGS. 10 and 11  allows for a reduction in a z-height of the electrochemical device, thereby improving material energy density. The reduction in z-height may come at the expense of reducing material in an x- or y-axis direction, i.e., orthogonal to the stack axis  1014 , to yield the insertion void  1006 , but such reduction in the direction of the x-y plane may be proportionally less impactful in terms of battery performance degradation. Thus, the illustrated electrochemical device architecture may provide a benefit over current electrochemical device architectures that include, e.g., an anode current collector layer between the anode layers  510 , which adds additional height to the electrochemical device stack. An example of a manufacturing process for building an electrochemical device structure as shown in  FIGS. 9-11  is described further below. 
     Referring to  FIG. 12 , a top view of a precursor cell used during the manufacture of an electrochemical device is shown in accordance with an embodiment. A precursor cell  1200  may be provided. The precursor cell may have, e.g., a square or rectangular profile, although the profile may be shaped otherwise. The precursor cell  1200  may be, but is not necessarily, singulated from a sheet of multi-layered material using laser cutting technologies, including an ablation laser for performing a laser ablation process. 
     Referring to  FIG. 13 , a cross-sectional view, taken about line C-C of  FIG. 12 , of a precursor cell is shown in accordance with an embodiment. The precursor cell  1200  may include the cathode current collector  504 , the barrier film layer  502 , and the cathode layer  506 , having the material and structure described above. Thus, in an embodiment, the precursor cell  1200  represents a state of manufacturing prior to deposition of the electrolyte layer  508  and the anode layer  510 . In an embodiment, the precursor cell  1200  has a contiguous sidewall. That is, the sidewall of each layer may be flush with that of another, creating a smooth transition across the entire sidewall face of the cell  1200 . The face may have a planar surface and/or a curved surface. Furthermore, in an embodiment, there is no slag layer over the face of the sidewall; this may be achieved using laser ablation as described above, to singulate the precursor cell  1200  from a sheet of multi-layered material. 
     Referring to  FIG. 14 , a top view of a precursor cell having an ablated anode current collector contact region is shown in accordance with an embodiment. In an embodiment, a cold cutting technology, such as an ablation laser, is used to remove a portion of one or more of the layers of the precursor cell  1200  in an anode current collector contact region  1012 . For example, a region having a width and/or length one-tenth of a width of the precursor cell  1200  may be ablated, although other widths and/or lengths are alternatively possible. 
     Referring to  FIG. 15 , a cross-sectional view, taken about line D-D of  FIG. 14 , of a precursor cell having an ablated anode current collector contact region is shown in accordance with an embodiment. As described above, the precursor cell  1200  may be ablated to remove portions of the cathode layer  506  and the barrier film layer  502 . Some portion of the cathode current collector  504  may also be ablated. Thus, an anode current collector contact region  1012  on an upper surface of the cathode current collector  504 , as well as a sidewall  1502  along an ablated surface of the cathode layer  506  and the barrier film layer  502 , may be formed. The sidewall  1502  may include a non-vertical slope extending between a cathode top edge  1504  and the anode current collector contact region  1012 . The sidewall  1502  slope may have a planar surface or a curved surface and be contiguous across the various ablated layers, as described above. Note that at least a portion of cathode current collector  504  may be a sloped sidewall between anode current collector contact region  1012  and barrier film layer  502 . Thus, the anode current collector contact region  1012  may be formed by only partially ablating through precursor cell  1200 , i.e., the laser ablation process may remove material from a top surface of precursor cell  1200  to the anode current collector contact region  1012  on cathode current collector  504  without cutting through the entire thickness of precursor cell  1200  as may be the case in a traditional laser cutting process. 
     Referring to  FIG. 16 , a top view of an electrochemical cell having the anode current collector contact region offset in a vertical direction is shown in accordance with an embodiment.  FIG. 17  is a cross-sectional view, taken about line E-E of  FIG. 16 , showing how an anode current collector contact region  1012  may be recessed in a vertical direction (vertical direction as seen in the figure). The electrolyte layer  508  and the anode layer  510  are deposited over the cathode layer  506  of the precursor cell  1200 . Deposition of the layers may be achieved using known processes, such as physical vapor deposition or other suitable technique. In this case, each of the electrolyte layer  508  and the anode layer  510  are formed with uniform thickness across the entire upper surface area of the precursor cell  1200 , including over the previously ablated anode current collector contact region  1012  and the sloped portion of cathode current collector  504  between anode current collector contact region  1012  and barrier film layer  502 . Deposition, coating, etc., of the electrolyte layer  508  and the anode layer  510  may uniformly cover the underlying anode current collector contact region  1012 , i.e., the exposed cathode current collector  504 , to form an upper surface of electrochemical cell  500 , having an anode layer  510  with the anode contact region  1008  as indicated, and the anode current collector contact region  1012 . In one embodiment, the anode layer  510  is the same thickness over its surface area and follows the tapered region between the cathode top edge  1504  and the anode current collector contact region  1012 , thereby resulting in a top surface of the anode layer  510 , which is located directly over the anode current collector contact region  1012 , to be vertically recessed in a vertical direction below a top surface of the anode layer  510  that is located directly over the anode contact region  1008 . 
     Referring to  FIG. 18 , a top view of the electrochemical cell having a cathode current collector tab region that is offset in a vertical direction (from an anode layer) is shown, wherein a corner of the electrochemical cell  500  that is opposite from the anode current collector contact region  1012  is ablated to expose the cathode current collector  504  and form a cathode current collector tab region  1802 . See the cross-sectional view, taken about line F-F of  FIG. 18 , in  FIG. 19 . Similar to the creation of the vertically recessed anode current collector contact region  1012  (see  FIGS. 16-17 ), the layers of the electrochemical cell  500  may be ablated to remove portions of the anode layer  510 , the electrolyte layer  508 , the cathode layer  506 , and the barrier film layer  502 . Furthermore, some portion of the cathode current collector  504  may be ablated to expose an upper surface of the cathode current collector  504  over a cathode current collector tab region  1802 . The exposed cathode current collector surface  1102  may provide a landing for making electrical contact with the cathode current collector  504 . That is, the cathode current collector surface  1102  may be exposed in the sense that it is not covered by any other layer of the electrochemical cell  500  prior to tab insertion. However, after a tab is inserted, physical and electrical contact may be made between the cathode current collector  504  and the inserted tab, and thus, at least a portion of the cathode current collector surface  1102  may no longer be “exposed.” Thus, the electrochemical cell  500  may transition from the anode layer  510  to the cathode current collector  504  by removing material to create a sidewall  1502  that slopes in a non-vertical direction between the anode layer  510  and the cathode current collector  504 . Note that the sidewall  1502  is illustrated with an exaggerated taper angle, i.e., the taper run of the sidewall  1502  may actually be substantially small as compared to a top surface area of the electrochemical cell  500 , and thus, sidewall  1502  is not apparent in the top view of electrochemical cell  500  illustrated in  FIG. 18 . More particularly, the sidewall  1502  may extend between an anode top edge  602  and the exposed cathode current collector surface  1102 . The sidewall  1502  may have a non-vertical sloped surface and be contiguous across the various ablated layers, as described above. Also note that at least a portion of cathode current collector  504  may be a sloped sidewall between the upward facing exposed cathode current collector  1102  and barrier film layer  502 . Thus, the cathode current collector  1102  may be formed by only partially ablating through electrochemical cell  500 , i.e., the laser ablation process may remove material from a top surface of electrochemical cell  500  to the exposed cathode current collector  1102  on cathode current collector  504  without cutting through the entire thickness of electrochemical cell  500  as may be the case in a traditional laser cutting process. 
     Referring to  FIG. 20 , a top view of an electrochemical cell having a cathode current collector tab region  1802  that is offset in a vertical direction is shown. In an embodiment, the anode current collector contact region  1012  and the cathode current collector tab region  1802  are trimmed back from the perimeter of the electrochemical cell  500 , creating an offset in a transverse direction, between an outer perimeter edge  2002  and a tab region outer edge  2004 . As described above, such a gap may be filled by a respective anode current collector tab  902  or cathode current collector tab  904  during assembly of an electrochemical device to define an outer boundary for electrochemical cell  500  or electrochemical device  900  that is a simple shape, e.g., a regular convex polygon shape such as a square. This can be seen in the top view of the device shown in  FIG. 21 . More particularly, the tabs can be described as being integrated with the cell structure and sandwiched between electrochemical cells, and extend away from the contact regions  1012 ,  1802  to fill the gaps to result in a profile in which outer edge  2002  of the cell perimeter and the tab edges  2102  are aligned, e.g., as when the electrochemical cell  500  has a square or rectangular profile as seen in  FIG. 21 . 
     Referring to  FIG. 22 , a top view of two electrochemical cells prior to being stacked to form an electrochemical device is shown in accordance with an embodiment. In an embodiment, at least two electrochemical cells  500 A and  500 B include respective first and second tab insertion areas. For example, a first electrochemical cell  500 A may include a left tab insertion area  2200 A and a right tab insertion area  2202 A. Similarly, a second electrochemical cell  500 B may include a left tab insertion area  2200 B and a right tab insertion area  2202 B. The first electrochemical cell  500 A may be flipped to stack on second electrochemical cell  500 B, for example, to form an electrochemical device  900  having facing anode layers. Thus, in an assembled configuration, the left tab insertion area  2200 A may face the right tab insertion area  2202 B, and the right tab insertion area  2202 A may face the left tab insertion area  2200 B. Accordingly, tab insertion areas of first electrochemical cell  500 A and second electrochemical cell  500 B may be mirror images of each other with respect to which type of tab is inserted into left and right tab insertion areas. That is, tab insertion areas  2200 A and  2202 B may be configured to contact anode current collector tab  902  and tab insertion areas  2202 A and  2200 B may be configured to contact cathode current collector tab  904 . In an embodiment, both tab insertion areas of mating tab insertion areas may include recessed contact regions, such as anode current collector contact region  1012  or cathode current collector tab region  1802  offset in a vertical direction from  1008  as described above. In other embodiments, mating tab insertion areas may include only one recessed area. For example, first electrochemical cell  500 A may include recessed left tab insertion area  2200 A, e.g., a recessed anode current collector contact region  1012 , and right tab insertion area  2200 B, e.g., a recessed cathode current collector tab region  1802 , and the mating left and right tab insertion areas  2200 A,  2202 B may not be recessed over the respective current collector contact regions. As a result, the current collector tabs may fill a vertical space between the electrochemical cells  500  that is half the separation distance of insertion void  1006  in  FIGS. 10-11 . Nonetheless, z-height may be reduced and the tabs may be recessed into the device in a transverse direction to provide for a device profile in which the outer perimeter edge  2002  is aligned with tab outer edges  2102 . More particularly, the electrochemical device of  FIGS. 9-11  may be formed. 
     The present invention also provides the following itemized embodiments: 
     1. An article of manufacture comprising: several electrochemical cells singulated from a sheet, wherein adjacent ones of the several electrochemical cells are separated by a gap that is tapered. 
     2. An article of manufacture, comprising: a first electrochemical cell with a second electrochemical cell, each cell having a respective electrolyte layer between a respective anode layer and a respective cathode layer in a stack direction, wherein the cells are separated by a separation distance in the stack direction that varies in a transverse direction, and wherein the separation distance is greater over an outer region of the coupled cells than over an inner region of the coupled cells. 
     3. The article of manufacture of item 2, wherein the outer region includes an anode collector contact region and the inner region includes an anode contact region, and wherein the anode collector contact region is electrically connected to the anode contact region. 
     4. The article of manufacture of item 3, wherein the respective anode layers extend over one or more of the anode contact region or the anode collector contact region. 
     5. A method, comprising: setting an intensity of a laser beam to a level less than required to melt one or more layers of an electrochemical cell; and lasing the one or more layers of the electrochemical cell with the laser beam to form a cell sidewall having a non-zero, non-vertical slope. 
     6. The method of item 5, wherein the one or more layers include an electrolyte layer stacked between an anode layer and a cathode layer in a vertical direction, the one or more layers having respective sidewalls making up at least a portion of the cell sidewall. 
     7. The method of item 6, wherein the anode layer includes an anode top surface, and wherein a height of the cell sidewall diminishes in a transverse direction outwardly. 
     8. The method of item 7, wherein the respective sidewalls of the anode layer, the electrolyte layer, and the cathode layer are contiguous along the non-vertical slope. 
     9. The method of item 8, wherein the non-vertical slope includes a linear slope portion. 
     10. The method of item 8, wherein the non-vertical slope includes a curvilinear slope portion. 
     In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of the invention as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.

Metadata:
Filing Date: 20180613
Publication Date: 20200428
Grant Date: 20200428
Priority Date: 20140527
Inventors: SNYDER, Shawn William
ISHIKAWA, TETSUYA
Assignee: APPLE INC
CPC Classifications: [{"code": "H01M10/052", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M10/0585", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M10/0525", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M10/052", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M10/0585", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M10/0436", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/0562", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M10/0463", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/0463", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M4/70", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/0562", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M10/0525", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M10/0436", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01M10/0562", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M4/64", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/0585", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M6/40", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M4/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M10/052", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M10/0436", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01M4/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M6/40", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M4/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M10/0525", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M6/40", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M10/0463", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/052", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M4/64", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/0525", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M2/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M6/40", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M10/0585", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M4/70", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/0463", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M10/0436", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01M4/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M10/0562", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01M50/536", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M50/536", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01M50/536", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02P70/50", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y02E60/10", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 53366314