Interlayer coatings for silicon and aluminum anodes in solid- state batteries at low stack pressures

Abstract

The present disclosure is directed to a solid-state battery, comprising an anode, a cathode, a solid-state electrolyte, and an interfacial layer. The anode can comprise at least one material selected from a group consisting of silicon and aluminum. The interfacial layer can be positioned between the anode and the solid-state electrolyte and can be the interfacial layer is configured to conduct ions between the solid-state electrolyte and the anode.

Description

INTERLAYER COATINGS FOR SILICON AND ALUMINUM ANODES IN SOLID- STATE BATTERIES AT LOW STACK PRESSURESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial Nos. 63 / 674,490, filed on 23 July 2024, and 63 / 709,860, filed 21 October 2024, both of which are incorporated herein by reference in its entirety as if fully set forth below.FIELD OF THE DISCLOSURE

[0002] The various embodiments of the present disclosure relate generally to solid state batteries.BACKGROUND

[0003] Solid-state batteries (SSBs) are an emerging technology that could be safer than conventional Li-ion batteries while also allowing for the use of new electrode materials that could increase the energy density and specific energy compared to Li-ion batteries. Solid-state batteries typically feature an active cathode material, a solid-state ion-conducting separator, and an active anode material. The cathode and anode materials store lithium ions, which travel back and forth between the two during charge and discharge.

[0004] Research on solid-state batteries largely focuses on either pure lithium metal anodes or composite anodes that contain active materials mixed with inactive solid-state ion-conducting material. Lithium metal is a promising anode material, but it poses substantial challenges due to the formation of short circuits, which cause battery failure. Composite anodes that contain active materials mixed with solid-state electrolyte (SSE) typically feature relatively low energy density because of the excess inactive materials present.

[0005] Alloy-type anodes, such as Al-based foils and Si electrodes, are promising materials for SSBs. These materials can exhibit good cycle life while offering high energy density and low manufacturing cost. Silicon anodes are attracting great attention for solid-state battery commercialization worldwide, with a variety of companies working on their commercialization. However, a key challenge in the field has been to enable good performance at low applied stack pressures within battery cells. This challenge arises because the alloy anode material undergoes large volume changes during charge and discharge, and it can lose contact with the solid-state electrolyte interface due to these volume changes. Low stackpressure (e.g., <2 MPa) is critical since higher stack pressures require bulky pressure jigs that result in very low energy density of the battery cells. Thus, new strategies are needed that can enable high capacity and good cycling stability of silicon-based solid-state batteries at low stack pressures.BRIEF SUMMARY

[0006] A first aspect of the present disclosure is directed to a solid-state battery, comprising an anode, a cathode, a solid-state electrolyte, and an interfacial layer. The anode can comprise at least one material selected from a group consisting of silicon and aluminum. The interfacial layer can be positioned between the anode and the solid-state electrolyte and can be configured to conduct ions between the solid-state electrolyte and the anode.

[0007] Another aspect of the present disclosure is directed to a method of making a solid-state battery, comprising: providing an anode comprising at least one material selected from the group consisting of: silicon and aluminum; providing a cathode; providing a solid-state electrolyte; and providing an interfacial layer disposed between the anode and the solid-state electrolyte.

[0008] In any of the embodiments disclosed herein, providing the interfacial layer can comprise coating the interfacial layer on the anode.

[0009] In any of the embodiments disclosed herein, coating the interfacial layer on the anode can comprise electrodepositing the interfacial layer on the anode.

[0010] In any of the embodiments disclosed herein, the interfacial layer can comprise a material selected from a group consisting of: Indium, Bismuth, Silver, Tin, Antimony, Germanium, and Gallium.

[0011] In any of the embodiments disclosed herein, the interfacial layer can comprise a composite material.

[0012] In any of the embodiments disclosed herein, the composite material can comprise a polymer composite material.

[0013] In any of the embodiments disclosed herein, the polymer composite material can comprise a polydimethylsiloxane polymer matrix and metallic particles disposed within the matrix. The metallic particles can be selected from the group consisting of: Indium, Bismuth, Silver, Tin, Antimony, Germanium, and Gallium.

[0014] In any of the embodiments disclosed herein, the interfacial layer can be configured to maintain contact between the anode and the solid-state electrolyte during charge and discharge cycles.

[0015] In any of the embodiments disclosed herein, the interfacial layer can be configured to maintain contact between the anode and the solid-state electrolyte during charge and discharge cycles when the battery is operating at stack pressures of 0. 1-20 MPa.

[0016] In any of the embodiments disclosed herein, the interfacial layer can be configured to deform and accommodate volume changes in the anode material.

[0017] In any of the embodiments disclosed herein, the interfacial layer can form a coating on at least a portion of the anode.

[0018] In any of the embodiments disclosed herein, the interfacial layer can have an average thickness of 10 nm to 10 microns.

[0019] These and other aspects of the present disclosure are described in the Detailed Description below and the accompanying drawings. Other aspects and features of embodiments will become apparent to those of ordinary skill in the art upon reviewing the following description of specific, exemplary embodiments in concert with the drawings. While features of the present disclosure may be discussed relative to certain embodiments and figures, all embodiments of the present disclosure can include one or more of the features discussed herein. Further, while one or more embodiments may be discussed as having certain advantageous features, one or more of such features may also be used with the various embodiments discussed herein. In similar fashion, while exemplary embodiments may be discussed below as device, system, or method embodiments, it is to be understood that such exemplary embodiments can be implemented in various devices, systems, and methods of the present disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The following detailed description of specific embodiments of the disclosure will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the disclosure, specific embodiments are shown in the drawings. It should be understood, however, that the disclosure is not limited to the precise arrangements and instrumentalities of the embodiments shown in the drawings.

[0021] FIG. 1 provides an SEM image of a focused-ion-beam (FIB) cross section of a particulate silicon anode with a few-micron thick indium layer deposited on the top surface via electrodeposition, in accordance with an exemplary embodiment of the present disclosure.

[0022] FIG. 2. provides an SEM image of a FIB cross section of a particulate silicon anode on a copper current collector with no deposited indium layer.

[0023] FIG. 3 provides a photograph of an indium-polydimethylsiloxane composite spread into a less than 10-micron layer on an aluminum foil anode, in accordance with an exemplary embodiment of the present disclosure.

[0024] FIG. 4 provides an SEM image of a cross section of an indium-polydimethylsiloxane composite spread into a less than 10-micron layer on an aluminum foil anode, in accordance with an exemplary embodiment of the present disclosure.

[0025] FIG. 5 provides a surface SEM image of an indium-polydimethylsiloxane composite spread into a less than 10-micron layer on an aluminum foil anode, in accordance with an exemplary embodiment of the present disclosure.

[0026] FIG. 6 provides a plot of first-cycle galvanostatic charge-discharge curves for a solid- state battery cell comprising a particulate silicon anode with an indium coating, a LiNio.6Coo.2Mno.2O2 (NMC622) cathode with 5 mAh cm'2capacity, and a LioPS CI solid-state electrolyte, in which the cell was operated at 0.2 mA cm-2at 25 °C using a stack pressure of 5 MPa, in accordance with an exemplary embodiment of the present disclosure.

[0027] FIG. 7 provides a plot of galvanostatic charge-discharge cycling for a solid-state battery cell consisting of a particulate silicon anode with an indium coating, a LiNio.6Coo.2Mno.2O2 (NMC622) cathode with 5 mAh cm-2capacity, and a LioPSsCI solid-state electrolyte, in which the cell was operated at 0.2 mA cm'2for the first two cycles, followed by 1 mA cm'2for the following cycles, and the temperature was 25 °C and the stack pressure was 5 MPa, in accordance with an exemplary embodiment of the present disclosure.

[0028] FIG. 8 provides a plot of first-cycle galvanostatic charge-discharge curves for a solid- state battery cell comprising a particulate silicon anode, a LiNio.6Coo.2Mno.2O2 (NMC622) cathode with 5 mAh cm'2capacity, and a LioPSsCI solid-state electrolyte, in which the cell was operated at 0.2 mA cm'2at 25 °C using a stack pressure of 5 MPa.

[0029] FIG. 9 provides a plot of galvanostatic charge-discharge cycling for a solid-state battery cell comprising a particulate silicon anode, a LiNio.6Coo.2Mno.2O2 (NMC622) cathode with 5 mAh cm'2capacity, and a LioPSsCI solid-state electrolyte, in which the cell was operated at 0.2 mA cm'2for the first two cycles, followed by 1 mA cm'2for the following cycles, and the temperature was 25 °C and the stack pressure was 5 MPa.

[0030] FIG. 10 provides a plot of first-cycle galvanostatic charge-discharge curves for a solid- state battery cell comprising a particulate silicon anode with an indium coating, a LiNio.6Coo.2Mno.2O2 (NMC622) cathode with 5 mAh cm'2capacity, and a LioPS CI solid-state electrolyte, in which the cell was operated at 25 °C using a stack pressure of 2 MPa, with 1 mAcm-2used for charging and 0.2 mA cm'2used for discharging, in accordance with an exemplary embodiment of the present disclosure.

[0031] FIG. 11 provides a plot of galvanostatic charge-discharge cycling for a solid-state battery cell comprising a particulate silicon anode with an indium coating, a LiNio.6Coo.2Mno.2O2 (NMC622) cathode with 5 mAh cm'2capacity, and a LioPS CI solid-state electrolyte, in which the cell was operated at 25 °C using a stack pressure of 2 MPa, with 1 mA cm'2used for charging and 0.2 mA cm'2used for discharging, in accordance with an exemplary embodiment of the present disclosure.

[0032] FIG. 12 provides a plot of first-cycle galvanostatic charge-discharge curves for a solid- state battery cell comprising a particulate silicon anode, a LiNio.6Coo.2Mno.2O2 (NMC622) cathode with 5 mAh cm'2capacity, and a LioPSsCI solid-state electrolyte, in which the cell was operated at 25 °C using a stack pressure of 2 MPa, with 1 mA cm'2used for charging and 0.2 mA cm'2used for discharging.

[0033] FIG. 13 provides a plot of galvanostatic charge-discharge cycling for a solid-state battery cell comprising a particulate silicon anode, a LiNio.6Coo.2Mno.2O2 (NMC622) cathode with 5 mAh cm'2capacity, and a LioPSsCI solid-state electrolyte, in which the cell was operated at 25 °C using a stack pressure of 2 MPa, with 1 mA cm'2used for charging and 0.2 mA cm'2used for discharging.

[0034] FIG. 14 provides a plot of galvanostatic charge / discharge curves from a solid-state battery cell with a polymer / indium-coated aluminum foil (30 microns) as the anode, a LiNio.6Coo.2Mno.2O2 (NMC622) cathode with 5 mAh cm'2capacity, and a LioPS CI solid-state electrolyte, in which a current density of 0.2 mA cm'2was used for the first two cycles, and then it was increased to 0.5 mA cm'2for subsequent cycles, and a stack pressure of 1 MPa was used, in accordance with an exemplary embodiment of the present disclosure.

[0035] FIG. 15 provides a plot of galvanostatic charge-discharge cycling from a solid-state battery cell with a polymer / indium-coated aluminum foil (30 microns) as the anode, a LiNio.6Coo.2Mno.2O2 (NMC622) cathode with 5 mAh cm'2capacity, and a LioPS CI solid-state electrolyte, in which a current density of 0.2 mA cm'2was used for the first two cycles, and then it was increased to 0.5 mA cm'2for subsequent cycles, and a stack pressure of 1 MPa was used, in accordance with an exemplary embodiment of the present disclosure.DETAILED DESCRIPTION

[0036] Although preferred exemplary embodiments of the disclosure are explained in detail, it is to be understood that other exemplary embodiments are contemplated. Accordingly, it is not intended that the disclosure is limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The disclosure is capable of other exemplary embodiments and of being practiced or carried out in various ways. Also, in describing the preferred exemplary embodiments, specific terminology will be resorted to for the sake of clarity.

[0037] To facilitate an understanding of the principles and features of the present disclosure, various illustrative embodiments are explained below. The components, steps, and materials described hereinafter as making up various elements of the embodiments disclosed herein are intended to be illustrative and not restrictive. Many suitable components, steps, and materials that would perform the same or similar functions as the components, steps, and materials described herein are intended to be embraced within the scope of the disclosure. Such other components, steps, and materials not described herein can include, but are not limited to, similar components or steps that are developed after development of the embodiments disclosed herein.

[0038] As used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise.

[0039] Also, in describing the preferred exemplary embodiments, terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art and includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.

[0040] Ranges can be expressed herein as from “about” or “approximately” one particular value and / or to “about” or “approximately” another particular value. When such a range is expressed, another exemplary embodiment includes from the one particular value and / or to the other particular value.

[0041] Similarly, as used herein, “substantially free” of something, or “substantially pure”, and like characterizations, can include both being “at least substantially free” of something, or “at least substantially pure”, and being “completely free” of something, or “completely pure”.

[0042] By ‘ ‘comprising” or “containing” or “including” is meant that at least the named compound, member, particle, or method step is present in the composition or article or method, but does not exclude the presence of other compounds, materials, particles, method steps, evenif the other such compounds, material, particles, method steps have the same function as what is named.

[0043] Mention of one or more method steps does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Similarly, it is also to be understood that the mention of one or more components in a device or system does not preclude the presence of additional components or intervening components between those components expressly identified.

[0044] The materials described as making up the various members of the invention are intended to be illustrative and not restrictive. Many suitable materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of the invention. Such other materials not described herein can include, but are not limited to, for example, materials that are developed after the time of the development of the invention.

[0045] Reference will now be made in detail to exemplary embodiments of the disclosed technology, examples of which are illustrated in the accompanying drawings and disclosed herein. Wherever convenient, the same references numbers will be used throughout the drawings to refer to the same or like parts.

[0046] Embodiments of the present disclosure are directed to engineering of the interface between alloy anodes and the solid electrolyte in a solid-state battery with novel interlayer materials to enable contact retention during cycling at low stack pressures.

[0047] As disclosed herein and shown in FIG. 1 , embodiments of the present disclosure can utilize an interfacial material layer disposed between an alloy anode (such as an aluminum- based foil) and a solid-state electrolyte material within a solid-state battery. The interfacial material can be designed to conduct ions between the solid-state electrolyte and the anode material, where the ions are stored upon charge.

[0048] The interfacial material layer can be many different metallic materials that alloy with lithium such as In, Bi, Ag, etc. In some embodiments, the interfacial material could be a polymer material that conducts ions between the solid-state electrolyte and the anode material.

[0049] The interfacial material can be specifically designed to be a composite of a metallic material that alloys with lithium and a polymer material that conducts ions between the solid- state electrolyte and the anode material. By mixing these materials in a composite, the interfacial material can retain the mechanical properties of the polymer (low yield strength,high elasticity), the electrically conducting properties of the metal, the reaction properties of the metal with lithium, and the lithium-transporting properties of the composite.

[0050] The interfacial material can also be configured to deform during volume changes of the anode and maintain contact between the anode and the solid-state electrolyte despite these volume changes. Adhesion between both the anode material and the solid-state electrolyte is likely desired.

[0051] As an example of one such metallic interfacial material, a silicon anode has been coated with a thin (3-4 micron) layer of indium metal. Indium has a low yield strength (~1 MPa) and reacts with lithium to form the ion-conductive phase Liln. It can deform and maintain contact between the sulfide solid-state electrolyte (e.g., LiePSsCl) and the aluminum alloy foil during charge / discharge. FIG. 1 shows a focused ion beam (FIB)-scanning electron microscopy (SEM) image of a particulate silicon anode coated with a 3-4 micron-thick indium layer. The indium layer is coated by electrodeposition. Conversely, FIG. 2 shows a silicon anode without the indium layer for comparison. Both electrodes feature obvious silicon particles, and the indium coating in FIG. 1 appears brighter.

[0052] For composite interfacial materials, metals such as indium, bismuth, silver, and other metallic particles can be mixed with polymer. The composites can be made many different ways known in the art, including, but not limited to, melting the materials together, physically mixing the materials, crosslinking the polymer in the presence of the metal particles, and the like.

[0053] As an example of one such composite interfacial material, an aluminum foil alloy anode material was coated with a thin layer of indium mixed with polydimethylsiloxane that has a boron-based crosslinker. This composite can be formed by melting the indium metal and the polymer together, solidifying, and then physically mixing. The composite can be highly deformable and can be spread onto an aluminum foil anode for further testing. FIG. 3 shows an image of an indium-polymer film spread onto an aluminum foil. FIGS. 4-5 show cross- sectional and surface SEM images, respectively, of an indium-polydimethylsiloxane composite spread into a less than 10-micron layer on an aluminum foil anode. Both images feature obvious indium particles (brighter particles) uniformly distributed in the polymer matrix.

[0054] The composite layers can deform to retain contact with the SSE and alloy anodes while also ensuring lithium is chemically extracted from the anodes during battery discharge. These factors can promote high Coulombic efficiency and long-term cycling stability. Such interfaciallayers can be lithium alloy materials themselves, they can be polymeric ion conductors, or they can be other materials that exhibit the properties enumerated above. Embodiments of the present disclosure can be compatible with any solid-state electrolyte separator, including, but not limited to, oxide lithium ion conductors, sulfide lithium ion conductors, polymer lithium conductors, conductors of other ions such as sodium, and the like.

[0055] FIG. 6 shows first-cycle galvanostatic charge-discharge curves for a solid-state battery cell consisting of a particulate silicon anode with an indium coating, a LiNio.6Coo.2Mno.2O2 (NMC622) cathode with 5 mAh cm'2capacity, and a LioPSsCI solid-state electrolyte. The cell was operated at 0.2 mA cm-2at 25 °C using a stack pressure of 5 MPa.

[0056] FIG. 7 shows galvanostatic cycling data from this cell over 100 cycles. At this relatively low stack pressure (5 MPa), the cell exhibits over 2 mAh cm-2areal capacity and retains 85% of its capacity from the 3rdto the 100thcycle.

[0057] FIG. 8 shows comparative data from a similar cell with a silicon electrode but without the indium interlayer, also operated at 5 MPa stack pressure. The cycling data for this cell in FIG. 9 shows lower capacity (rapidly falling below 1 mAh cm'2), and the cell only retains 38% of its capacity from the 3rdto the 100thcycle.

[0058] FIGS. 10-11 show electrochemical cycling data from a solid-state battery cell with a silicon anode with an indium coating, an NMC622 cathode with 5 mAh cm'2capacity, and a LioPS CI solid-state electrolyte. The cell was operated at 25 °C using a lower stack pressure of 2 MPa, with 1 mA cm'2used for charging and 0.2 mA cm'2used for discharging. FIG. 11 shows that even at this very low stack pressure, the cell exhibits >2 mAh cm'2areal capacity over the first 30 cycles. In contrast, FIGS. 12-13 show a similar cell operated at 2 MPa stack pressure but containing a silicon electrode without the indium coating. FIG. 13 shows that the cell capacity is very low, below 1 mAh cm'2for all cycles.

[0059] Battery performance in a solid-state battery cell containing polymer-metal composite interlayer was also tested. FIG. 14 shows galvanostatic data from a solid-state battery cell with a polymer / indium-coated aluminum foil (30 microns) as the anode, a LioPSsCl solid-state electrolyte separator, and a LiNio.6Mno.2Coo.2O2 cathode. A current density of 0.2 mA cm'2was used for the first two cycles, and then it was increased to 0.5 mA cm'2for subsequent cycles. A stack pressure of 1 MPa was used. The galvanostatic curves in FIG. 14 show that almost the theoretical capacity is achieved on first charge. FIG. 15 shows that the cycling is fairly stable over 30 cycles.

[0060] Embodiments of the present disclosure find many commercial applications. The novel interfacial layers disclosed herein can improve the electrochemical behavior and durability of high-capacity anodes for solid-state batteries, which is attractive for high-energy-density batteries. This interfacial layer in combination with these active anode materials can enable high-energy batteries with simplified manufacturing steps compared to conventional battery technologies. Embodiments of the present disclosure offer many advantages over conventional batteries, including, but not limited to, higher energy density, longer cycle life, and improved safety.

[0061] It is to be understood that the embodiments and claims disclosed herein are not limited in their application to the details of construction and arrangement of the components set forth in the description and illustrated in the drawings. Rather, the description and the drawings provide examples of the embodiments envisioned. The embodiments and claims disclosed herein are further capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purposes of description and should not be regarded as limiting the claims.

[0062] Accordingly, those skilled in the art will appreciate that the conception upon which the application and claims are based may be readily utilized as a basis for the design of other structures, methods, and systems for carrying out the several purposes of the embodiments and claims presented in this application. It is important, therefore, that the claims be regarded as including such equivalent constructions.

[0063] Furthermore, the purpose of the foregoing Abstract is to enable the United States Patent and Trademark Office and the public generally, and especially including the practitioners in the art who are not familiar with patent and legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The Abstract is neither intended to define the claims of the application, nor is it intended to be limiting to the scope of the claims in any way.

Claims

CLAIMSWhat is claimed is:

1. A solid-state battery, comprising: an anode comprising at least one material selected from a group consisting of: silicon and aluminum; a cathode; a solid-state electrolyte; and an interfacial layer positioned between the anode and the solid-state electrolyte; wherein the interfacial layer is configured to conduct ions between the solid-state electrolyte and the anode.

2. The solid-state battery of claim 1, wherein the interfacial layer comprises a material selected from a group consisting of: Indium, Bismuth, Silver, Tin, Antimony, Germanium, and Gallium.

3. The solid-state battery of claim 2, wherein the interfacial layer comprises a composite material.

4. The solid-state battery of claim 3, wherein the composite material comprises a polymer composite material.

5. The solid-state battery of claim 4, wherein the polymer composite material comprises a polydimethylsiloxane polymer matrix, and metallic particles disposed within the matrix, the metallic particles selected from a group consisting of: Indium, Bismuth, Silver, Tin, Antimony, Germanium, and Gallium.

6. The solid-state battery of claim 1, wherein the interfacial layer is configured to maintain contact between the anode and the solid-state electrolyte during charge and discharge cycles.

7. The solid-state battery of claim 6, wherein the interfacial layer is configured to maintain contact between the anode and the solid-state electrolyte during charge and discharge cycles when the battery is operating at stack pressures of 0.1-20 MPa.

8. The solid-state battery of claim 1, wherein the interfacial layer is configured to deform and accommodate volume changes in the anode material.

9. The solid-state battery of claim 1, wherein the interfacial layer forms a coating on at least a portion of the anode.

10. The solid-state battery of claim 1, wherein the interfacial layer has an average thickness of 10 nm to 5 microns.

11. A method of making a solid-state battery, comprising: providing an anode comprising at least one material selected from the group consisting of: silicon and aluminum; providing a cathode; providing a solid-state electrolyte; and providing an interfacial layer disposed between the anode and the solid-state electrolyte.

12. The method of claim 11, wherein the interfacial layer comprises a metallic material selected from the group consisting of Indium, Bismuth, Silver, Tin, Antimony, Germanium, and Gallium.

13. The method of claim 12, wherein providing the interfacial layer comprises coating the interfacial layer on the anode.

14. The method of claim 13, wherein coating the interfacial layer on the anode comprises electrodepositing the interfacial layer on the anode.

15. The method of claim 11, wherein the interfacial layer comprises a polymer composite material.

16. The method of claim 15, wherein the polymer composite material comprises metallic particles selected from the group consisting of Indium, Bismuth, Silver, Tin, Antimony, Germanium, and Gallium.

17. The method of claim 16, wherein the polymer composite material is crosslinked using a boron-based crosslinker.

18. The method of claim 11, wherein providing the solid-state electrolyte comprises laminating the solid-state electrolyte to the interfacial layer.

19. The method of claim 11, wherein the interfacial layer is configured to maintain contact between the anode and the solid-state electrolyte during charge and discharge cycles when the battery is operating at stack pressures of 0. 1 -20 MPa.

20. The method of claim 11, wherein the interfacial layer is configured to deform and accommodate volume changes in the anode material during charge and discharge cycles.

21. The method of claim 11 , wherein the interfacial layer has an average thickness of 10 nm to 10 microns.

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