Method for prelithiation of anodes for battery applications

Abstract

The invention provides a method for the prelithiation of an anode material. The method comprises providing a transfer sheet having a layer of lithium metal (Li) or lithium-containing alloy deposited on a surface thereof, and bringing the transfer sheet into contact with the anode material. Molten lithium or a molten lithium-containing alloy may be used to deposit the layer of Li or lithium-containing alloy onto the transfer sheet.

Description

TITLE OF THE INVENTION METHOD FOR PRELITHIATING ANODES FOR BATTERY APPLICATIONS CROSS-REFERENCE TO RELATED REQUESTS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 724,750 filed on November 25, 2024. The content of that application is incorporated in its entirety into this application by reference. FIELD OF INVENTION

[0002] The invention relates generally to methods for prelithiating anodes. More specifically, the invention relates to a method using a transfer sheet having a layer of lithium metal deposited on its surface. The surface of the transfer sheet may also include a lithium protective layer and a layer of lithiophilic material. The method consists of bringing the transfer sheet into contact with the anode material to be prelithiated. CONTEXT OF THE INVENTION

[0003] The formation of the solid electrolyte interphase (SEI) on the negative electrode of lithium-ion batteries is a significant source of lithium consumption and contributes substantially to the decrease in the battery's initial coulombic efficiency (ICE). The low ICE is even more detrimental to the performance of silicon-based anodes due to the irreversible capacity loss during the first cycle, related both to electrolyte decomposition at the interface and to lithium entrapment within the silicon to form intermetallics [1]. Anode prelithiation has been proposed as a compensatory strategy to overcome this problem and avoid lithium consumption from the cathode.

[0004] Various approaches to prelithiation have been proposed in the literature. The use of electrochemical prelithiation has been suggested [2]. This allows for precise control of the amount of Li used in prelithiation. However, this approach involves the use of roll-to-roll (R2R) electrochemical cells, an organic solvent, and Li salts that exhibit Disadvantages include: 1) complicated installation, 2) operating protocols, and 3) loss of Li salts and organic solvents, which increase cost and reduce safety. Another approach proposes the use of stabilized lithium metal powder (SLMP) for the prelithiation strategy [3,4]. However, producing very fine Li particles is difficult. Furthermore, these particles have a high surface area, making them extremely reactive. They therefore require special passivation treatments, and their transport and handling demand numerous precautions. Another proposed approach relies on the use of physical vapor deposition (PVD) methods to deposit a known quantity of Li onto the anode surface [5]. However, this approach involves the use of complex machines and high-vacuum atmospheres, which increases production costs.

[0005] There is a need for improved methods for anode prelithiation. In particular, there is a need for methods that are both efficient and cost-effective. SUMMARY OF THE INVENTION

[0006] The inventors propose a simple and practical method for prelithing an anode material. A thin, controlled layer of molten lithium is deposited onto the surface of a transfer sheet. This surface possesses lithiophilic properties, which facilitates the deposition of the thin lithium layer. The anode material to be prelithied is then brought into contact with the transfer sheet, resulting in the prelithiation of the material. The transfer sheet can be metallic, composite, or polymer.

[0007] In embodiments of the invention, a lithium protective layer is applied to the surface of the transfer sheet and the lithium metal or lithium alloy layer is deposited on the lithium protective layer.

[0008] In embodiments of the invention, at least one layer of lithiophilic material is applied to the lithium protective layer, and the lithium metal or lithium-containing alloy layer is deposited on the lithiophilic material layer. The lithiophilic material layer may consist of a nickel (Ni) layer and / or a tin (Sn) layer.

[0009] In embodiments of the invention, the transfer sheet comprises a metal such as copper (Cu), nickel (Ni); a polymer or a heat-resistant composite material.

[0010] In embodiments of the invention, the transfer sheet, after contacting the transfer sheet with the anode material or the negative electrode, can be reused at least twice.

[0011] In embodiments of the invention, the prelithiated transfer sheet can be stored for future use. In this embodiment of the invention, the transfer sheet can be stored in roll form under conditions that prevent any reaction between the metallic lithium and substances such as nitrogen, oxygen, or water. For example, the transfer sheet can be stored under an inert atmosphere (Ar).

[0012] The invention therefore provides the following in accordance with certain aspects thereof: (1) A method for prelithiating an anode material, comprising providing a transfer sheet having a layer of lithium (Li) metal or lithium-containing alloy deposited on a surface thereof, and bringing the transfer sheet into contact with the anode material; optionally molten lithium or a molten lithium-containing alloy is used to effect the deposition of the layer of Li or lithium-containing alloy on the transfer sheet. (2) Method according to point (1) above, wherein a lithium protective layer is applied to the surface of the transfer sheet and the lithium metal or lithium alloy layer is deposited on the lithium protective layer. (3) Method according to point (2) above, wherein at least one layer of lithiphilic material is applied over the lithium protective layer and the lithium metal or lithium alloy layer is deposited over the lithiphilic material layer; optionally the lithiphilic material layer is a nickel (Ni) layer or a tin (Sn) layer; optionally a Ni layer is applied followed by an Sn layer. (4) Method according to any one of points (1) to (3) above, in which a compressive force is applied between the transfer sheet and the anode material; Optionally the compression process includes the application of a heat source; preferably having a temperature below the melting point of lithium; preferably a temperature of about 150°C to about 160°C. (5) Method according to any one of points (1) to (4) above, wherein the transfer sheet comprises a metal such as copper (Cu), nickel (Ni); a heat-resistant polymer or composite material; preferably a decomposition temperature of the polymer or composite material is above about 180°C. (6) Method according to any one of points (1) to (4) above, wherein the transfer sheet comprises: polyimide (PI); optionally the transfer sheet comprises polyimide and copper (Cu). (7) Method according to any one of points (1) to (4) above, wherein the transfer sheet comprises: polyimide and nickel (Pl-Ni); polyimide, copper, and nickel (Pi-Cu-Ni); polyimide, nickel, and tin (Pl-Ni-Sn); or polyimide, copper, nickel, and tin (Pl-Cu-Ni-Sn). (8) Method according to any one of points (1) to (4) above, wherein the transfer foil is a copper foil or a nickel foil or a copper foil coated with a layer of nickel (Cu-Ni) or a copper foil coated with a layer of nickel and a layer of tin (Cu-Ni-Sn). (9) Method according to any one of points (1) to (8) above, wherein a thickness of the lithium protective layer applied to the surface of the transfer foil is about 100 to about 1200 nm; preferably about 300 to about 500 nm. (10) Method according to any one of points (1) to (9) above, wherein a thickness of the lithium (Li) metal or lithium-containing alloy layer deposited on the surface of the transfer sheet is about 2 to about 15 pm; preferably about 3 to about 10 pm. (11) Method according to any one of points (1) to (10) above, wherein a thickness of the layer of lithiophilic material applied over the lithium protective layer is about 10 to about 100 nm; preferably about 30 to about 40 nm. (12) Method for prelithing a lithium battery anode, the method comprising the following steps: deposition of a protective Li layer on a foil surface transfer; application of at least one layer of a lithiphilic material on the Li protective layer; application of molten Li or a molten alloy containing lithium onto the layer of the lithiphilic material; and bringing the transfer sheet into contact with the negative electrode. (13) Method according to any one of points (1) to (12) above, further comprising a step of reusing the transfer sheet after the transfer sheet has been brought into contact with the anode material or the negative electrode; optionally the transfer sheet is used at least twice. (14) Method for preparing a transfer sheet used for prelithing a lithium battery anode, the method comprising the following steps: deposition of a protective Li layer on a surface of a transfer sheet; application of at least one layer of a lithiophile material on the protective Li layer; and application of molten Li or a molten alloy containing lithium on the layer of the lithiophile material. (15) Method according to point (14) above, further comprising a step of storing the resulting transfer sheet for future use; optionally the transfer sheet is stored in the form of a roll; preferably the transfer sheet is stored under conditions enabling any reaction between the Li metal and entities such as N2, O2 or H2O; preferably the transfer sheet is stored under an inert atmosphere, for example under argon (Ar). (16) Transfer sheet obtained by the method as defined in point (14) or (15) above. (17) Prelithied anode material obtained by the method as defined in any of points (1) to (11) above. (18) Prelithiated lithium battery anode obtained by the method as defined in point (12) above. (19) Use of the transfer sheet obtained by the method as defined in point (14) or (15) above for the prelithiation of an anode material or a lithium battery anode. (20) Use of a prelithiated anode material obtained by the method as defined in point (17) above and / or of a prelithiated anode obtained by the method as defined in point (18) above in the manufacture of a lithium battery. (21) Plant incorporating the method of manufacturing the transfer sheet as defined in point (16) above; optionally the plant is an anode manufacturing plant. (22) Anode manufacturing plant incorporating the method for manufacturing prelithiated anode material as defined in point (17) above and / or the method for manufacturing prelithiated lithium battery anode as defined in point (18) above. (23) Device adapted to carry out the method as defined in any one of points (1) to (15) above.

[0013] Other objects, advantages, and features of the present invention will become more apparent upon reading the following non-limiting description of its specific embodiments, given by way of example only with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The patent or publication application file must contain at least one color drawing. Copies of this file with the color drawing(s) will be provided by the Patent Office upon request and payment of the necessary fees.

[0015] In the attached drawings:

[0016] Figure 1: Photo of a prelithiated graphite electrode + water droplet.

[0017] Figure 2: dQ / dV of the conventional graphite electrode versus the Li metal for the first cycle (started with a negative current).

[0018] Figure 3: dQ / dV of the pre-laminated graphite electrode with lithium metal prepared by melt deposition relative to Li metal (started with a negative current).

[0019] Figure 4: dQ / dV of the pre-laminated graphite electrode with lithium metal prepared by molten deposition relative to Li metal for 5 cycles (started with a negative current).

[0020] Figure 5: Scanning Electron Microscopy (SEM) images of the commercial polyimide-copper (Pl-Cu) sheet with the electrodeposited Ni layer.

[0021] Figure 6: Contact angle of liquid Li on the Pl-Cu-Ni-Sn sheet.

[0022] Figure 7: Image of the Pl-Cu-Ni-Sn sheet after the application of the Li layer using a coating slit. DESCRIPTION OF ILLUSTRATIVE METHODS OF IMPLEMENTATION

[0023] Before describing the present invention in more detail, it is understood that the invention is not limited to the particular embodiments described below, as variations of these embodiments may be made while remaining within the scope of the appended claims. It is also understood that the terminology used is intended to describe particular embodiments and is not meant to be restrictive. On the contrary, the scope of the present invention will be established by the appended claims.

[0024] To provide a clear and consistent understanding of the terms used in this specification, several definitions are provided below. Furthermore, unless otherwise stated, all technical and scientific terms used herein have the same meaning as that commonly understood by a person with ordinary competence in the art to which this invention relates.

[0025] The use of the word "a" or "an" when used in conjunction with the term "including" in the claims and / or specification may mean "one," but is also compatible with the meanings of "one or more," "at least one," and "one or more than one." Similarly, the word "another" may mean "at least a second or more."

[0026] As used in this specification and the claims, the words "including" (and any form of including, such as "include" and "include"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "include" and "include") or "containing" (and any form of containing, such as "contain" and "contains"), are inclusive or open and do not exclude additional, unmentioned process elements or steps.

[0027] The inventors have designed and developed a method for prelithiating an anode material. The method comprises providing a transfer sheet having a layer of lithium metal deposited on one of its surfaces, and bringing the transfer sheet into contact with the anode material. In some embodiments of the invention, a lithium protective layer is applied to the surface of the transfer sheet, and the lithium metal layer is deposited on the lithium protective layer. In other embodiments, a layer of lithiophilic material is applied on the lithium protective layer, and the lithium metal layer is deposited on the lithiophilic material layer. Example 1: Preparation of the Cu-Ni-Sn-Li transfer sheet

[0028] A 500 nm nickel (Ni) layer followed by a 40 nm tin (Sn) layer was electrodeposited onto an 8 µm thick and 100 mm wide copper (Cu) foil in a reverse reverse (R2R) configuration. The prepared foil was then used in another R2R configuration placed in a special glove box (with purified argon (Ar) gas containing less than 1 ppm of H₂O, O₂, and N₂) where molten lithium metal was applied to the surface of the Cu-Ni-Sn foil using a special rolling device capable of applying a thin layer of Li metal at a Li application rate of 1.8 m / min. Measurement of the thickness of the deposited Li layer at various locations on the Cu-Ni-Sn-Li foil confirmed the deposition of a Li layer with an average thickness of 3.7 µm and a standard deviation of approximately 10%. Example 2: Prelithiation of the graphite electrode using the Cu-Ni-Sn-Li transfer sheet

[0029] The Cu-Ni-Sn-Li sheet prepared in Example 1 was used as a transfer sheet to prelithate a commercial copper-graphite (Cu-Gr) lithium-ion anode electrode. A standard commercial graphite electrode was then laminated to the Cu-Ni-Sn-Li sheet using a roller press at 130°C.

[0030] To verify the presence of lithium in the graphite electrode, a few drops of water were placed on the surface of the prelithiated electrode. Bubbles appeared on the surface, demonstrating the incorporation of lithium into the graphite electrode (Figure 1).

[0031] Two half-button cells were prepared with a liquid electrolyte based on carbonate and LiPF6 salt: • a cell with a graphite electrode prior to prelithiation compared to a standard lithium metal sheet, and • another with a pre-laminated graphite electrode with Cu-Ni-Sn-Li foil relative to lithium metal.

[0032] The cells were first cycled in discharge, then in charge at C / 10 and 25°C. Figure 2 shows the dQ / dV derivative of the first cycle for a conventional graphite electrode, with three typical reaction peaks during discharge and three during charge.

[0033] Figure 3 shows the dQ / dV derivative of the first cycle for a graphite electrode assumed to be prelithied according to our proposed approach. The absence of the first reduction peak around 0.18 vs. Li7Li, whose oxidation peak reappears during charging, indicates efficient prelithiation of the graphite using our ultrafine lithium prepared by molten Li deposition.

[0034] To verify the cycle life of the prelithiated graphite, the cells were cycled over several cycles. Figure 4 shows the dQ / dV curves over five cycles for the prelithiated graphite electrode. We observe that subsequent cycles show the reduction peak close to 0.18 vs. Li7Li, unlike the first discharge, which confirms the good cycle life of the prelithiated electrode over several cycles.

[0035] Thus, it is possible to pre-lithiumize an electrode by simple compression of lithium prepared by molten deposition. Example 3: Preparation of the polymeric transfer sheet

[0036] A commercially available 25 pm thick polyimide film with a 2 pm copper layer on one side was used to electrodeposit a 400-500 nm thick Ni layer, as can be seen in Figure 5, using a nickel sulfate solution.

[0037] The copper-nickel polyimide (Pl-Cu-Ni) sheet was then subjected to a further electrodeposition step using a tin (Sn) plating solution to deposit a very thin tin layer (110 nm) as a lithiophilic layer. The lithiophilicity of the Pl-Cu-Ni-Sn sheet sample was tested by measuring the contact angle of the Li liquid (heated to 250°C) deposited on the sheet (heated to 270°C), as can be seen in Figure 6.

[0038] The contact angle measured after 5 seconds of molten Li deposition was approximately 79°, showing relatively good lithiophily of the surface towards molten Li (non-lithophilic surfaces exhibit contact angles of approximately 100° to approximately 110°).

[0039] After confirming the lithiophilicity of the surface, the Pl-Cu-Ni-Sn sheet was placed on a heated plate (set to 200°C), and molten Li was applied to its surface using a 50 mm wide coating slot (heated to 250°C). Figure 7 below shows an image of the Pl-Cu-Ni-Sn-Li sheet prepared by the described method. This example clearly demonstrates the feasibility of producing Pi-Cu-Ni-Sn-Li transfer sheets in an industrial R2R configuration. The Li layer thickness obtained in this example was determined to be approximately 18 pm without any optimization. It is clear that much thinner Li thicknesses can be achieved through further optimization.

[0040] As a person versed in the art will understand, after prelithing the anode material or the anode, the transfer sheet (strip) can be recovered to redeposit lithium or lithium-containing alloy and proceed again to prelithify an anode material or an anode, thus constituting a closed loop.

[0041] As anyone familiar with the craft will understand, the metal strip can be stored in a roll for later use. Typically, this period can extend to several months if precautions are taken to prevent the reaction of the lithium metal with elements such as N2, O2, or H2O, for example, by packaging it in a well-sealed metal-plastic bag in the presence of a relatively unreactive atmosphere (Ar, or other gases that do not react with lithium metal).

[0042] As a person versed in the art will understand, the invention also relates to a device adapted for carrying out the method according to the invention.

[0043] As a person versed in the art will understand, other variations and combinations can be made to the various realizations of the invention as described above.

[0044] Although this disclosure has been described in connection with specific embodiments, it is understood that it is subject to further modifications and that this application is intended to cover all variations, uses, or adaptations including such deviations from this disclosure, as falling within known or customary practice in the art and applicable to the essential features set forth above, and as follows within the scope of the appended claims. The features described in the context of separate aspects and embodiments of the invention may be used together and / or interchangeably. Similarly, the features described in the context of a single embodiment may also be provided separately or in any appropriate sub-combination.

[0045] The scope of the claims should not be limited by the preferred embodiments described above; but should receive the broadest interpretation consistent with the description as a whole.

[0046] This description refers to a number of documents, the contents of which are incorporated herein by reference in their entirety. REFERENCES: 1. Tan, DHS et al. Carbon-free high-loading silicon anodes enabled by sulfide solid electrolytes. Science 373, 1494-1499 (2021). 2. Min, X. et al. Challenges of prelithiation strategies for next generation high energy lithium-ion batteries. Energy Storage Mater. 47, 297-318 (2022). 3. Pan, Q. et al. Improved electrochemical performance of microsized SiO-based composite anode by prelithiation of stabilized lithium metal powder. J. Power Sources 347, 170-177 (2017). 4. Gao Liu et al., Anode structure with binders for silicon and stabilized lithium metal powder, WO2017123443A1. 5. Bo Peng et al., Controlled roll to roll pre-lithiation by lithium vacuum vapor deposition for high performance silicon-based lithium-ion battery, Materials Letters, Vol. 358, 2024, 1356606, https: / / doi.Org / 10.1016 / j.matlet.2O23.135606.

Claims

DEMANDS:

1. A method for prelithiating an anode material, comprising providing a transfer sheet having a layer of lithium (Li) metal or lithium-containing alloy deposited on a surface thereof, and bringing the transfer sheet into contact with the anode material; optionally molten lithium or a molten lithium-containing alloy is used to effect the deposition of the layer of Li or lithium-containing alloy on the transfer sheet.

2. Method according to claim 1, wherein a lithium protective layer is applied to the surface of the transfer sheet and the lithium metal or lithium alloy layer is deposited on the lithium protective layer.

3. Method according to claim 2, wherein at least one layer of lithiphilic material is applied over the lithium protective layer and the lithium metal or lithium alloy layer is deposited over the lithiphilic material layer; optionally the lithiphilic material layer is a nickel (Ni) layer or a tin (Sn) layer; optionally a Ni layer is applied followed by an Sn layer.

4. A method according to any one of claims 1 to 3, wherein a compressive force is applied between the transfer sheet and the anode material; optionally the compression process includes the application of a heat source; preferably having a temperature lower than the melting point of lithium; preferably a temperature of about 150°C to about 160°C.

5. A method according to any one of claims 1 to 4, wherein the transfer sheet comprises a metal such as copper (Cu), nickel (Ni); a heat-resistant polymer or composite material; preferably a decomposition temperature of the polymer or composite material is greater than about 180°C.

6. Method according to any one of claims 1 to 4, wherein the transfer sheet comprises: polyimide (PI); optionally the transfer sheet comprises polyimide and copper (Cu).

7. A method according to any one of claims 1 to 4, wherein the transfer sheet comprises: polyimide and nickel (Pl-Ni); polyimide, copper, and nickel (Pi-Cu-Ni); polyimide, nickel, and tin (Pl-Ni-Sn); or polyimide, copper, nickel, and tin (Pl-Cu-Ni-Sn).

8. Method according to any one of claims 1 to 4, wherein the transfer foil is a copper foil or a nickel foil or a copper foil coated with a layer of nickel (Cu-Ni) or a copper foil coated with a layer of nickel and a layer of tin (Cu-Ni-Sn).

9. Method according to any one of claims 1 to 8, wherein a thickness of the lithium protective layer applied to the surface of the transfer sheet is about 100 to about 1200 nm; preferably about 300 to about 500 nm.

10. Method according to any one of claims 1 to 9, wherein a thickness of the lithium (Li) metal or lithium-containing alloy layer deposited on the surface of the transfer sheet is about 2 to about 15 pm; preferably about 3 to about 10 pm.

11. Method according to any one of claims 1 to 10, wherein a thickness of the lithiophilic material layer applied over the lithium protective layer is about 10 to about 100 nm; preferably about 30 to about 40 nm.

12. Method for prelithing a lithium battery anode, the method comprising the following steps: deposition of a protective Li layer on a surface of a transfer sheet; application of at least one layer of a lithiphilic material on the protective Li layer; application of molten Li or a molten alloy containing lithium on the layer of the lithiphilic material; and contacting the transfer sheet and the negative electrode.

13. Method according to any one of claims 1 to 12, further comprising a step of reusing the transfer sheet after the transfer sheet has been brought into contact with the anode material or the negative electrode; optionally the transfer sheet is used at least twice.

14. A method for preparing a transfer sheet used for prelithing a lithium battery anode, the method comprising the following steps: deposition of a protective Li layer on a surface of a transfer sheet; application of at least one layer of a lithiophilic material over the protective Li layer; and application of the Li in melting or of a molten alloy containing lithium on the layer of the lithiophilic material.

15. Method according to claim 14, further comprising a step of storing the transfer sheet obtained for future use; optionally the transfer sheet is stored in the form of a roll; preferably the transfer sheet is stored under conditions enabling any reaction between the Li metal and entities such as N2, O2 or H2O; preferably the transfer sheet is stored under an inert atmosphere, for example under argon (Ar).

16. Transfer sheet obtained by the method as defined in claim 14 or 15.

17. Prelithiated anode material obtained by the method as defined in any one of claims 1 to 11.

18. Prelithiated lithium battery anode obtained by the method as defined in claim 12.

19. Use of the transfer sheet obtained by the method as defined in claim 14 or 15 for the prelithiation of an anode material or a lithium battery anode.

20. Use of a prelithiated anode material obtained by the method as defined in claim 17 and / or of a prelithiated anode obtained by the method as defined in claim 18 in the manufacture of a lithium battery.

21. Plant incorporating the method of manufacturing the transfer sheet as defined in claim 16; optionally the plant is an anode manufacturing plant.

22. Anode manufacturing plant incorporating the method for manufacturing the prelithiated anode material as defined in claim 17 and / or the method for manufacturing the prelithiated lithium battery anode as defined in claim 18.

23. Device adapted to carry out the method for the prelithiation of an anode material as defined in any one of claims 1 to 15.

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