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US-12626914-B2 - Anode protection layer

US12626914B2US 12626914 B2US12626914 B2US 12626914B2US-12626914-B2

Abstract

An electrochemical cell assembly comprising: at least one electrochemical cell or cells comprising—a cathode comprising an electrochemically active material; —an anode comprising an alkali metal or alkali metal alloy layer and a protection layer containing a first layer and a second layer; wherein the first layer comprises a metal and/or non-metal that alloys with an alkali metal and is formed on the alkali metal or alkali metal alloy layer, and an second layer deposited on the first layer, wherein the second layer is an ionically conducting layer having an electronic conductivity of less than 10 −5 S cm −1 ; and—an electrolyte, and wherein the cell assembly further comprises a means of applying pressure to the at least one electrochemical cell or cells.

Inventors

  • Jacob LOCKE
  • Jokin RICARTE
  • Marco Carboni
  • Rachel LEAR
  • Ulderico ULISSI

Assignees

  • GELION TECHNOLOGIES PTY LTD

Dates

Publication Date
20260512
Application Date
20200709
Priority Date
20190710

Claims (19)

  1. 1 . An electrochemical cell assembly comprising: at least one electrochemical cell or cells comprising a cathode comprising an electrochemically active material; an anode comprising an alkali metal or alkali metal alloy layer and a protection layer containing a first layer and a second layer; wherein the first layer comprises a metal and/or non-metal that alloys with an alkali metal and is formed on the alkali metal or alkali metal alloy layer, and the second layer deposited on the first layer, wherein the second layer is an ionically conducting layer having an electronic conductivity of less than 10 −5 S cm −1 ; and an electrolyte, and wherein the cell assembly is further configured to apply a force comprising at least 0.5 MPa of pressure continuously to at least 80% of a surface of the anode; and wherein the first layer has a thickness of 1 nm to 5000 nm.
  2. 2 . The electrochemical cell assembly as claimed in claim 1 , wherein the alkali metal or alkali metal alloy comprises a lithium metal or metal alloy or a sodium metal or metal alloy.
  3. 3 . The electrochemical cell assembly as claimed in claim 1 , wherein the anode further comprises a current collector.
  4. 4 . The electrochemical cell assembly as claimed in claim 1 , wherein the first layer comprises at least one metal or non-metal selected from aluminium, boron, zinc, gallium, indium, carbon, silicon, germanium, tin, lead, antimony, silver, gold, sodium, potassium, magnesium, calcium, and mixtures thereof, preferably indium or zinc.
  5. 5 . The electrochemical cell assembly as claimed in claim 1 , wherein the first layer has an electronic conductivity of more than 10 −5 S cm −1 .
  6. 6 . The electrochemical cell assembly as claimed in claim 1 , wherein the first layer has a lithium diffusivity, during cycling, of more than 10 −15 cm 2 s −1 .
  7. 7 . The electrochemical cell assembly as claimed in claim 1 , wherein the first layer has an ionic conductivity of greater than 10 −9 S cm −1 .
  8. 8 . The electrochemical cell assembly as claimed in claim 1 , wherein the second layer comprises at least one of a ceramic material, a polymer material, a polymer and ceramic composite material, and combinations thereof.
  9. 9 . The electrochemical cell assembly as claimed in claim 1 , wherein the second layer comprises an oxynitride, sulphide, phosphate, oxide, oxysulfide, thiophosphate, borate, oxyborate, borohydride, silicate, aluminate, or thioaluminate compound, or a combination thereof.
  10. 10 . The electrochemical cell assembly as claimed in claim 9 , wherein the ceramic material is LiPON.
  11. 11 . The electrochemical cell assembly as claimed in claim 8 , wherein the polymer material is polyethylene oxide.
  12. 12 . The electrochemical cell assembly as claimed in claim 1 , wherein the second layer has an ionic conductivity of greater than 10 −9 S cm −1 .
  13. 13 . The electrochemical cell assembly as claimed in claim 1 wherein the second layer has a thickness of between 1 nm and 1000 nm.
  14. 14 . The electrochemical cell assembly as claimed in claim 1 wherein a total amount of alkali metal able to be stored within the first layer is less than 10% of a electrochemical alkali metal storage capacity of the electroactive material within the cathode.
  15. 15 . The electrochemical cell assembly as claimed in claim 1 wherein the pressure is applied using a band, wrap or tubing positioned on the outside of the cell.
  16. 16 . The electrochemical cell assembly as claimed in claim 1 wherein the cell or cells are selected from a lithium sulphur cell or a sodium sulphur cell, a lithium air cell or a sodium air cell, or a lithium ion cell or a sodium ion cell.
  17. 17 . The electrochemical cell assembly as claimed in claim 3 , wherein the current collector is a copper or nickel current collector.
  18. 18 . A method of forming an electrochemical cell assembly in accordance with claim 1 , said method comprising the steps of: a) providing an alkali metal or alkali metal alloy layer; b) contacting at least one metal and/or non-metal that forms an alloy with an alkali metal with the alkali metal or alkali metal alloy layer to form a continuous first layer, wherein the first layer has a thickness of between 1 nm and 5000 nm; c) depositing an ionically conducting layer having an electronic conductivity of less than 10 −5 S cm −1 on the surface of the first layer to form a continuous second layer; wherein steps a) to c) form an anode; d) providing an electrolyte; e) providing a cathode; wherein steps a) to e) form an electrochemical cell, f) applying continuous pressure to at least 80% of a surface of the anode of the at least one cell formed in accordance with steps a) to e), wherein the pressure applied is at least 0.5 MPa.
  19. 19 . The method as claimed in claim 18 , wherein at least one of the first and second layers is formed by physical vapour deposition.

Description

The present invention relates to an electrochemical cell. The present invention also relates to a method of forming an electrochemical cell, in particular a method of forming a coating on an anode of an electrochemical cell. BACKGROUND Electrodes comprising alkali and alkaline earth metals have been used in both primary and secondary electrochemical cells. In particular, lithium has been found to be a desirable material for the formation of electrodes, as it is a lightweight material that can provide a high energy density. This can enable construction of cells that are suitable for a wide range of applications, including those where minimising the weight of the cell is of great importance. In a lithium-sulphur cell, for instance, lithium metal foil may be used as the anode of the cell. However, despite the advantages provided by the use of such electrodes, alkali and alkaline earth metals have certain disadvantages when employed in electrochemical cells. Using lithium metal foil as an example, lithium may react with the electrolyte within a cell. This may form a resistive layer over the electrode and decrease battery performance over time. Lithium dendrites and/or mossy deposits may also be formed on the surface of the lithium metal foil during cycling, which can result in short-circuiting and decreased cycling performance, and may ultimately lead to reduction of the lifetime of the cell. In view of the above difficulties, the inclusion of a protective layer on the surface of an anode may be desirable. Various protective layers have been proposed. Such a protective layer is required to conduct alkali metal ions, whilst reducing or preventing contact between the surface of the anode and the bulk electrolyte. For example, an alloy layer on top of the anode has been suggested as a means of improving the cycling or capacity characteristics of a cell. However, alkali metal alloy layers may react with the electrolyte over time, resulting in the formation of a resistive layer on top of the electrode. Alkali metal plating on top of the alloy layer may also be observed, along with uneven stripping. Ceramic materials have also been proposed as a candidate for forming a protection layer on an anode. U.S. Pat. No. 6,025,094 discloses a negative electrode having an alkali metal layer and a glassy or amorphous protective layer coating the alkali metal layer, wherein the protective layer conducts alkali metal ions. However, the use of a ceramic layer may increase charge transfer resistance of an anode, which may result in inhomogeneous stripping and plating of the alkali metal and alkali metal deposition on the top of the protective layer. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 provides SEM images of the surface of a lithium metal electrode. FIG. 2 provides SEM images and impedance graphs of a lithium anode having an alloy layer formed on the surface. FIG. 3 provides SEM images and impedance graphs of a lithium anode having a ceramic layer formed on the surface. FIG. 4 provides digital photographs and SEM images of a protected lithium anode after completion of a lithium plating step under application of a force of 0 MPa, 0.5 MPa and 1 MPa in accordance with an embodiment of the invention. FIG. 5 provides digital photographs, SEM images and cross sections of a protected lithium anode following a lithium stripping step in accordance with an embodiment of the invention. FIG. 6 provides digital photographs and SEM images of a protected lithium anode in accordance with an embodiment of the present invention. FIG. 7 provides electrochemical data for a protected lithium anode in accordance with an embodiment of the present invention. DESCRIPTION Before particular examples of the present invention are described, it is to be understood that the present disclosure is not limited to the particular cell, method or material disclosed herein. It is also to be understood that the terminology used herein is used for describing particular examples only and is not intended to be limiting, as the scope of protection will be defined by the claims and equivalents thereof. In describing and claiming the cell and method of the present invention, the following terminology will be used: the singular forms “a”, “an”, and “the” include plural forms unless the context clearly dictates otherwise. Thus, for example, reference to “an anode” includes reference to one or more of such elements. In accordance with a first aspect of the present invention, there is provided an electrochemical cell assembly comprising: at least one electrochemical cell or cells comprising a cathode comprising an electrochemically active material;an anode comprising an alkali metal or alkali metal alloy layer and a protection layer containing a first layer and a second layer; wherein the first layer comprises a metal and/or non-metal that alloys with an alkali metal and is formed on the alkali metal or alkali metal alloy layer, and wherein the second layer is deposited o