METHOD FOR PRODUCING AN ELECTROCHEMICAL CELL

Abstract

A method of manufacturing an electrochemical cell, the method comprising: Providing a porous or non-porous metal substrate; Exposing a surface of the metal substrate to a chalcogen in the gas phase so that a conformal metal chalcogenide layer forms on the surface of the metal substrate; Providing a lithium metal foil having a first surface and an opposite second surface; and Laminating the lithium metal foil onto the metal chalcogenide layer on the surface of the metal substrate, so that the first surface of the lithium metal foil physically and chemically bonds to the metal chalcogenide layer on the surface of the metal substrate, wherein the surface of the metal substrate and the metal chalcogenide layer are heated to a temperature above a melting point of lithium, so that when the lithium metal foil is laminated to the metal chalcogenide layer on the surface of the metal substrate, the first surface of the lithium metal foil melts locally and actively wets the metal chalcogenide layer on the surface of the metal substrate without melting the second surface of the lithium metal foil, wherein the surface of the metal substrate and the metal chalcogenide layer are heated to a temperature in the range of 250 °C to 450 °C before the lithium metal foil is laminated to the metal chalcogenide layer on the surface of the metal substrate, and wherein the second surface of the lithium metal foil is maintained at a temperature below 180 °C before the lithium metal foil is laminated to the metal chalcogenide layer on the surface of the metal substrate.

Description

INTRODUCTION

[0001] A battery is a device that converts chemical energy into electrical energy through electrochemical reduction-oxidation (redox) reactions. In secondary or rechargeable batteries, these electrochemical reactions are reversible, allowing the batteries to undergo multiple charge and discharge cycles.

[0002] Secondary lithium batteries generally comprise one or more electrochemical cells containing a negative electrode, a positive electrode, a porous separator, an electrolyte, a negative current collector, and a positive current collector. These batteries are powered by the cooperative movement of lithium ions and electrons between the negative and positive electrodes of each electrochemical cell. The electrolyte is ionically conductive and provides a medium for conducting the lithium ions through the electrochemical cell between the negative and positive electrodes. The current collectors are electrically conductive and allow the electrons to move simultaneously from one electrode to the other via an external circuit. The porous separator physically separates the electrodes and electrically insulates them while allowing free flow of ions between them.

[0003] Uniform and continuous physical contact between the negative and positive electrodes and their respective current collectors is required to ensure effective charge transfer between them and efficient battery operation throughout the battery's lifetime.

[0004] DE 696 36 385 T2 describes a non-aqueous secondary battery comprising a positive electrode sheet comprising a layer primarily comprising a lithium-containing transition metal oxide. The secondary battery further comprises a negative electrode sheet comprising a negative electrode material layer primarily comprising a metal or non-metal oxide and / or a chalcogenide and at least one auxiliary layer comprising water-insoluble particles.

[0005] US 2017 / 0 324 113 A1 describes negative electrode assemblies containing lithium sulfide anolyte layers, electrochemical cells containing these assemblies, and a method for their production. SUMMARY

[0006] In a method for manufacturing an electrochemical cell, a porous or non-porous metal substrate and a lithium metal foil having a first surface and an opposite second surface may be provided. A surface of the metal substrate may be exposed to a chalcogen in the gas phase, such that a conformal metal chalcogenide layer forms on the surface of the metal substrate. The lithium metal foil may be laminated to the metal chalcogenide layer on the surface of the metal substrate, such that the first surface of the lithium metal foil is physically and chemically bonded to the metal chalcogenide layer on the surface of the metal substrate.

[0007] The surface of the metal substrate and the metal chalcogenide layer can be heated to a temperature above the melting point of lithium, so that when the lithium metal foil is laminated to the metal chalcogenide layer on the surface of the metal substrate, the first surface of the lithium metal foil melts locally and actively wets the metal chalcogenide layer on the surface of the metal substrate without melting the second surface of the lithium metal foil. For example, the surface of the metal substrate and the metal chalcogenide layer can be heated to a temperature in the range of 250°C to 450°C before the lithium metal foil is laminated to the metal chalcogenide layer on the surface of the metal substrate.In one form, the second surface of the lithium metal foil can be maintained at a temperature below 180 °C while the lithium metal foil is laminated to the metal chalcogenide layer on the surface of the metal substrate.

[0008] The lithium metal foil can be laminated to the metal chalcogenide layer on the surface of the metal substrate by positioning the lithium metal foil adjacent to the metal substrate so that the first surface of the lithium metal foil faces the surface of the metal substrate. The metal substrate and the lithium metal foil can then be passed between a pair of metal rollers.

[0009] The metal substrate may comprise a non-porous metal foil, a perforated sheet, or a porous metal mesh.

[0010] The metal substrate may comprise copper. In this case, the metal chalcogenide layer may comprise copper oxide, copper sulfide, copper selenide, or a combination thereof.

[0011] The chalcogen may comprise oxygen, sulfur, selenium, or a combination thereof. In this case, the metal chalcogenide layer may comprise a metal oxide, a metal sulfide, a metal selenide, or a combination thereof.

[0012] In one form, the chalcogen may comprise oxygen. In this case, the surface of the metal substrate can be exposed to gaseous oxygen by heating the metal substrate in air, causing the gaseous oxygen to chemically react and bond with the surface of the metal substrate.

[0013] In another form, the chalcogen may comprise sulfur or selenium. In this case, the surface of the metal substrate may be exposed to gaseous sulfur or selenium by heating a volume of solid-phase sulfur or selenium to release a volume of gaseous sulfur or selenium. The surface of the metal substrate may then be exposed to the volume of gaseous sulfur or selenium, causing the gaseous sulfur or selenium to chemically react and bond with the surface of the metal substrate.

[0014] The metal substrate may be non-porous and may include a first major surface and an opposite second major surface. In this case, the metal chalcogenide layer may be formed on at least one of the first or second major surfaces of the metal substrate.

[0015] The metal substrate can have a thickness in the range of 8-20 µm.

[0016] The metal chalcogenide layer can have a thickness in the range of 1-500 nm. The lithium metal foil can have a thickness in the range of 5-100 µm.

[0017] The metal substrate can be formed into a negative electrode current collector having a desired size and shape and having at least one negative lithium metal electrode layer physically and chemically bonded thereto.

[0018] In another method for fabricating an electrochemical cell, a porous or non-porous metal substrate having a first surface and an opposite second surface may be provided. Furthermore, a first lithium metal foil and a second lithium metal foil may be provided, each of the first and second lithium metal foils having a first surface and an opposite second surface. The first and second surfaces of the metal substrate may be exposed to a chalcogen in the gas phase, forming a first metal chalcogenide layer on the first surface of the metal substrate and a second metal chalcogenide layer on the second surface of the metal substrate.The first and second lithium metal foils may be laminated to the first and second metal chalcogenide layers on the first and second surfaces of the metal substrate, respectively, such that the first surface of the first lithium metal foil physically and chemically bonds to the first metal chalcogenide layer on the first surface of the metal substrate and the first surface of the second lithium metal foil physically and chemically bonds to the second metal chalcogenide layer on the second surface of the metal substrate.

[0019] The metal substrate and the first and second metal chalcogenide layers can be heated to a temperature above a melting point of lithium such that when the first and second lithium metal foils are respectively laminated to the first and second metal chalcogenide layers on the first and second surfaces of the metal substrate, the first surface of the first lithium metal foil locally melts and actively wets the first metal chalcogenide layer on the first surface of the metal substrate without melting the second surface of the first lithium metal foil, and the first surface of the second lithium metal foil locally melts and actively wets the second metal chalcogenide layer on the second surface of the metal substrate without melting the second surface of the second lithium metal foil.

[0020] The first and second lithium metal foils can be laminated to the first and second metal chalcogenide layers on the first and second surfaces of the metal substrate, respectively, by positioning the first and second lithium metal foils adjacent to the metal substrate such that the first surface of the first lithium metal foil faces the first surface of the metal substrate and the first surface of the second lithium metal foil faces the second surface of the metal substrate. Subsequently, the metal substrate and the first and second lithium metal foils can be passed between a pair of metal rollers. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an exploded perspective view of an electrochemical cell for a lithium metal secondary battery, the electrochemical cell including a negative lithium metal electrode layer coupled to a negative electrode current collector, a positive electrode layer coupled to a positive electrode current collector, a porous separator layer disposed between the negative and positive electrode layers, and an electrolyte in ionic contact with the positive and negative electrode layers; Fig. 2 is a side cross-sectional view of a negative electrode current collector having a first negative lithium metal electrode layer and a first intermediate metal chalcogenide layer formed on a first major surface thereof, and a second negative lithium metal electrode layer and a second intermediate metal chalcogenide layer formed on a second major surface thereof; Fig. 3 is a cross-sectional view of an embodiment of an apparatus for forming a metal oxide layer on a surface of a negative electrode current collector by exposing the surface of the negative electrode current collector to an air flow; Fig. 4 is a cross-sectional view of another embodiment of an apparatus for forming a metal sulfide layer or a metal selenide layer on a surface of a negative electrode current collector by exposing the surface of the negative electrode current collector to gaseous sulfur or selenium; and Fig. 5 is a cross-sectional view of an embodiment of an apparatus for forming a metal chalcogenide layer on a surface of a metal substrate and then laminating a lithium metal foil onto the metal chalcogenide layer on the surface of the metal substrate. DETAILED DESCRIPTION

[0021] The presently disclosed electrochemical cell incorporates lithium metal as the negative electrode material and thus exhibits a relatively high energy density compared to electrochemical cells that incorporate other elements or compounds as negative electrode materials. During fabrication of the electrochemical cell, a robust physical and chemical bond is established between the lithium metal and a surface of a negative electrode current collector by forming a metallic chalcogenide interlayer.In particular, the metal chalcogenide layer enables the formation of a better bond between the negative lithium metal electrode layer and the negative electrode current collector, while simultaneously improving the coulombic efficiency of the negative electrode layer without negatively affecting the impedance of the electrochemical cell compared to electrochemical cells that include negative lithium metal electrode layers formed directly on their negative electrode current collectors.

[0022] Fig. 1 illustrates an idealized exploded view of an electrochemical cell 10 for a secondary lithium metal battery (not shown) including a negative lithium metal electrode layer 12, a positive electrode layer 14, a porous separator layer 16 disposed between the negative and positive electrode layers 12, 14, and a non-aqueous electrolyte 18 in ionic contact with the positive and negative electrode layers 12, 14. A negative electrode current collector 20 having a first major surface 22 and an opposite second major surface 24 is physically and electrically coupled to the negative electrode layer 12. In addition, a positive electrode current collector 26 having a first major surface 28 and an opposite second major surface 30 is physically and electrically coupled to the positive electrode layer 14.The electrochemical cell 10 may have a thickness that, measured from a second major surface 24 of the negative electrode current collector 20 to an opposite second major surface 30 of the positive electrode current collector 26, is between less than 100 micrometers to about one millimeter.

[0023] The lithium metal layer of the negative electrode 12 is chemically and physically bonded to the first major surface 22 of the negative electrode current collector 20 via a metal chalcogenide interlayer 32. The metal chalcogenide layer 32 may be "lithiophilic," meaning that lithium has an affinity for the metal chalcogenide layer 32 and actively wets the chalcogenide layer 32. As a result, the metal chalcogenide layer 32 may help adhere the negative electrode layer 12 to the surface 22 of the negative electrode current collector 20 and may also help maintain electrical contact between the negative electrode layer 12 and the negative electrode current collector 20 during operation and / or movement of the electrochemical cell 10.For example, the chalcogenide layer 32 can help prevent delamination or separation of the negative electrode layer 12 from the negative electrode current collector 20 during bending or deformation of the electrochemical cell 10. Furthermore, the chalcogenide layer 32 can promote wetting of the negative lithium metal electrode layer 12 on the first major surface 22 of the negative electrode current collector 20 during fabrication of the electrochemical cell 10 and during subsequent charging cycles.

[0024] In Fig. 1, a single negative electrode layer 12 is formed on the first major surface 22 of the negative electrode current collector 20 and a single positive electrode layer 14 is formed on the first major surface 28 of the positive electrode current collector 26. However, in further embodiments, both the first and second major surfaces 22, 24, 28, 30 of the negative and positive electrode current collectors 20, 26 may be coated with first and second negative and positive electrode layers (not shown), respectively, for example, when the electrochemical cell 10 is combined with several other electrochemical cells in an electrochemical cell stack (not shown). In this case, the first and second negative electrode layers may be connected to the first and second major surfaces 22, 24 of the negative electrode current collector 20, respectively, via first and second chalcogenide interlayers (not shown).

[0025] The lithium metal negative electrode layer 12 may consist essentially of lithium (Li) metal. For example, the lithium metal negative electrode layer 12 may comprise more than 97% lithium by weight, or more preferably, more than 99% lithium. However, the negative electrode layer 12 preferably does not comprise other elements or compounds that undergo a reversible redox reaction with lithium during operation of the electrochemical cell 10. For example, the negative electrode layer 12 preferably does not comprise an intercalation host material formulated to undergo the reversible introduction or intercalation of lithium ions, or an alloying material capable of electrochemically alloying to form lithium compound phases.Furthermore, the negative electrode layer 12 preferably does not include a transition material or an alloying material that can electrochemically alloy and form lithium compound phases. Some examples of materials that are preferably excluded from the negative electrode layer 12 of the present disclosure include carbon-based materials (e.g., graphite, activated carbon, carbon black, and graphene), silicon and silicon-based materials, tin oxide, aluminum, indium, zinc, cadmium, lead, germanium, tin, antimony, titanium oxide, lithium titanium oxide, lithium titanate, lithium oxide, metal oxides (e.g., iron oxide, cobalt oxide, manganese oxide, copper oxide, nickel oxide, chromium oxide, ruthenium oxide, and / or molybdenum oxide), metal phosphides, metal sulfides, and metal nitrides (e.g., phosphides, sulfides, and / or nitrides, or iron, manganese, nickel, copper, and / or cobalt). Furthermore, the negative electrode layer 12 preferably does not comprise a polymeric binder.Some examples of polymeric binders that are preferably excluded from the negative electrode layer 12 of the present disclosure include polyvinylidene fluoride (PVdF), ethylene propylene diene monomer (EPDM) rubber, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), and polyacrylic acid.

[0026] The positive electrode layer 14 may comprise one or more electrochemically active materials capable of undergoing a reversible redox reaction with lithium at a higher electrochemical potential than the material of the negative electrode layer 12, such that an electrochemical potential difference exists between the electrodes 12, 14. In one form, the positive electrode material 14 may comprise an intercalation host material capable of undergoing the reversible insertion or intercalation of lithium ions. In this case, the intercalation host material of the positive electrode layer 14 may comprise a layered oxide of the formula LiMeO2, an olivine-type oxide of the formula LiMePO4, a spinel-type oxide represented by the formula LiMe2O4, a tavorite represented by one or both of the following formulas LiMeSO4F or LiMePO4F, or a combination of both, where Me is a transition metal (e.g.,Co, Ni, Mn, Fe, Al, V or a combination thereof). More specifically, the host material for the intercalation can be a layered lithium transition metal oxide, such as lithium cobalt oxide (LiCoO2) and lithium nickel magnesium cobalt oxide [Li(Ni. X Mn V Co Z )O2], a spinel lithium transition metal oxide, such as spinel lithium manganese oxide (LiMn2O4), lithium iron phosphate (LiFePO4), or lithium fluorophosphate (Li2FePO4F), lithium nickel oxide (LiNiO2), lithium aluminum manganese oxide (LixAl Y Mn 1-YO2), lithium vanadium oxide (LiV2O5), or a combination thereof. In another form, the positive electrode layer 14 may comprise a conversion material including a component capable of undergoing a reversible electrochemical reaction with lithium, wherein the component undergoes a phase change or a change in crystalline structure with a change in oxidation state. In this case, the conversion material of the positive electrode layer 14 may comprise sulfur, selenium, tellurium, iodine, a halide (e.g., a fluoride or chloride), sulfide, selenide, telluride, iodide, phosphide, nitride, oxide, oxysulfide, oxyfluoride, sulfur fluoride, sulfur oxyfluoride, or a lithium and / or metal compound thereof. Examples of suitable metals for inclusion in the conversion material of the positive electrode layer 14 include iron, manganese, nickel, copper, and cobalt.

[0027] The electrochemically active material of the positive electrode layer 14 may be mixed with a polymeric binder to provide structural integrity to the positive electrode layer 14. Some examples of suitable polymeric binders include polyvinylidene fluoride (PVdF), ethylene propylene diene monomer rubber (EPDM), styrene butadiene rubber (SBR), carboxymethoxycellulose (CMC), polyacrylic acid, and mixtures thereof. The positive electrode layer 14 may optionally include particles of an electrically conductive material, which may include very fine particles of, for example, high-surface-area carbon black.

[0028] The porous separation layer 16 may comprise any organic or inorganic material capable of physically separating and electrically insulating the electrode layers 12, 14 from each other while allowing free flow of lithium ions therebetween. For example, the separation layer 16 may comprise a nonwoven material, such as a fabricated sheet, fabric, or mat of directional or randomly oriented fibers. As another example, the separation layer 16 may comprise a microporous polymeric material, such as a microporous polyolefin-based membrane or film. The separation layers 16 may comprise a single polyolefin or a combination of polyolefins, such as polyethylene (PE), polypropylene (PP), polyamide (PA), poly(tetrafluoroethylene) (PTFE), polyvinylidine fluoride (PVdF), and / or poly(vinyl chloride) (PVC).In one form, the porous separating layer 16 may comprise a laminate of one or more polymeric materials, such as a laminate of PE and PP. The separating layer 16 may have a thickness in the range of 10 µm to 30 µm.

[0029] The non-aqueous electrolyte 18 may comprise any material capable of effectively conducting lithium ions through the separator 16 and between the negative and positive electrodes 12, 14. For example, the electrolyte 18 may comprise a non-aqueous liquid electrolyte. In this case, the non-aqueous electrolyte 18 may comprise a solution including a lithium salt dissolved or ionized in a non-aqueous, aprotic, organic solvent or a mixture of non-aqueous, aprotic organic solvents. Some suitable lithium salts that may be used to create the electrolyte 18 include LiClO4, LiAlCl4, LiI, LiBr, LiSCN, LiBF4, LiB(C6H5)4, LiAsF6, LiCF3SO3, LiN(CF3SO2)2, LiPF6, and combinations thereof. The non-aqueous, aprotic organic solvent in which the lithium salt is dissolved can be a cyclic carbonate (i.e. ethylene carbonate, propylene carbonate), an acyclic carbonate (i.e.The electrolyte 18 may be a carboxylic acid ester (e.g., dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate), an aliphatic carboxylic acid ester (e.g., methyl formate, methyl acetate, methyl propionate), a γ-lactone (e.g., γ-butyrolactone, γ-valerolactone), an acyclic ether (e.g., 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane), a cyclic ether (e.g., tetrahydrofuran, 2-methyltetrahydrofuran), or a mixture thereof. As another example, the non-aqueous electrolyte 18 may comprise a gel or a plasticized polymer electrolyte. In this case, the non-aqueous electrolyte 18 may comprise a polymer host material impregnated with a non-aqueous electrolytic solution. Some examples of suitable polymer host materials include poly(vinylidene) (PVdF), poly(acrylonitrile) (PAN), poly(methyl methacrylate) (PMMA), poly(ethylene oxide) (PEO), polyacrylates, and poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP).The electrolyte 18 may also include one or more additives formulated to improve the performance, lifetime, and safety of the electrochemical cell 10. Some examples of suitable additives for incorporation into the electrolyte 18 include vinylene carbonate, propylene carbonate, and / or lithium bis-oxalatoborate salt.

[0030] The negative and positive electrode current collectors 20, 26 may comprise any material capable of collecting and reversibly passing free electrons to and from their respective electrode material layers 12, 14. For example, the negative and / or positive electrode current collectors 20, 26 may comprise an electrically conductive metal or metal alloy, such as a transition metal or an alloy thereof. In some specific examples, the negative electrode current collector 20 may comprise copper, nickel, an iron alloy (e.g., stainless steel), or titanium, and the positive electrode current collector 26 may comprise aluminum, nickel, or an iron alloy (e.g., stainless steel). Of course, other electrically conductive metals may be used if desired.

[0031] The negative and positive electrode current collectors 20, 26 may each be in the form of a thin and flexible porous or non-porous metal substrate. For example, the negative and positive electrode current collectors 20, 26 may be in the form of thin and flexible non-porous metal foils, porous metal meshes, or perforated sheets. The specific configuration of the negative and positive electrode current collectors 20, 26 may depend on the intended application of the electrochemical cell 10. In some embodiments, the negative and positive electrode current collectors 20, 26 may have thicknesses ranging from 8 micrometers to 20 micrometers.

[0032] The intermetal chalcogenide layer 32 may comprise a transition metal chalcogenide (e.g., an oxide, sulfide, and / or selenide of copper (Cu), nickel (Ni), iron (Fe), and / or titanium (Ti)). For example, the intermetal chalcogenide layer 32 may comprise a transition metal chalcogenide represented by one or more of the following formulas: Me2Ch, MeCh2, MeCh, or Me2Ch3, where Me is a transition metal (e.g., Cu, Ni, Fe, and / or Ti) and Ch is a chalcogen (e.g., O, S, and / or Se). The composition of the chalcogenide layer 32 may depend on the composition of the negative electrode current collector 20. In embodiments where the negative electrode current collector 20 comprises copper (Cu), the chalcogenide layer 32 may comprise, for example, copper oxide (e.g., CuO and / or Cu2O), copper sulfide (e.g., CuS and / or Cu2S), and / or copper selenide (e.g., CuSe and / or Cu2Se).Additionally or additionally, the metal chalcogenide layer 32 may comprise a lithium chalcogenide (e.g., an oxide, sulfide, and / or selenide of lithium). For example, the metal chalcogenide layer 32 may comprise a lithium (Li) chalcogenide having the formula Li2Ch, where Ch is a chalcogen (e.g., O, S, and / or Se). In some embodiments, the metal chalcogenide layer 32 may comprise a composition of one or more transition metal chalcogenides and one or more lithium chalcogenides. The chalcogenides included in the metal chalcogenide layer 32 may be stoichiometric or non-stoichiometric. The metal chalcogenide layer 32 may have a thickness in the range of one nanometer to 500 nanometers.

[0033] As in Fig. 1, the negative electrode current collector 20 may include a negative polarity tab 34, and the positive electrode current collector 26 may include a positive polarity tab 36. The negative and positive polarity tabs 34, 36 may be integrally formed in a one-piece construction with their respective negative and positive electrode current collectors 20, 26. Or, the negative and positive polarity tabs 34, 36 may be separately fabricated and subsequently coupled, for example, by welding, to their respective negative and positive electrode current collectors 20, 26. In practice, the negative and positive polarity tabs 34, 36 of the electrochemical cell 10 may be electrically connected to the corresponding negative and positive polarity tabs of one or more other electrochemical cells (not shown) to form a lithium metal battery (not shown).The negative and positive polarity tabs 34, 36 may also be electrically connected to an electrical device 38 via an interruptible external circuit 40. The electrical device 38 may comprise an electrical load that can be powered by the electrochemical cell 10 or a power source that can recharge the electrochemical cell 10 through an applied external voltage.

[0034] During discharge of the electrochemical cell 10, the negative electrode layer 12 contains a relatively high concentration of elemental lithium, which is oxidized into lithium ions and electrons. The lithium ions migrate from the negative electrode layer 12 through the pores of the porous separating layer 16 and across the ionically conductive electrolyte 18 to the positive electrode layer 14. At the same time, the electrons pass through the external circuit 40 from the negative electrode layer 12 to the positive electrode layer 14. The lithium ions are incorporated into the active material of the positive electrode layer 14 through electrochemical reduction. The electrochemical cell 10 can be recharged after a full or partial discharge of its available capacity by an external power source that reverses the electrochemical reactions that took place during the discharge.

[0035] During recharging of the electrochemical cell 10, intercalated lithium in the positive electrode layer 14 is oxidized into lithium ions and electrons. The lithium ions migrate from the positive electrode layer 14 to the negative electrode layer 12 through the porous separator 16 via the electrolyte 18, with the electrons flowing through the external circuit 40 to the negative electrode layer 12. The lithium cations are reduced to elemental lithium at the negative electrode layer 12 and stored on the surface 22 of the negative electrode current collector 20 for reuse.

[0036] Fig. 2 illustrates a side cross-sectional view of a negative electrode current collector 120 comprising an electrically conductive metal (e.g., copper) and including a first major surface 122 and a second major surface 124. A thin first metal chalcogenide layer 132 is formed directly on the first major surface 122 of the current collector 120, and a thin second metal chalcogenide layer 142 is formed on the second major surface 124 of the current collector 120. In addition, a first negative lithium metal electrode layer 112 is formed directly on the first metallic chalcogenide layer 132 over the first major surface 122 of the current collector 120, and a second negative lithium metal electrode layer 144 is formed directly on the second metallic chalcogenide layer 142 over the second major surface 124 of the current collector 120.

[0037] In Fig. In Figure 2, the first and second major surfaces 122, 124 of the current collector 120 are illustrated as substantially flat, which may be the case in embodiments where the current collector 120 comprises a metal foil or a perforated sheet. However, in other embodiments, such as where the current collector 120 comprises a metal mesh, the surfaces 122, 124 of the current collector 120 may be contoured, and the layers 132, 142, 112, 144 may substantially conform to the contours.

[0038] The first and second major surfaces 122, 124 of the current collector 120 may be lightly abraded (e.g., ground) prior to forming the first and second metal chalcogenide layers 132, 142 and the first and second negative lithium metal electrode layers 144 on the first and second major surfaces 122, 124 of the current collector 120.

[0039] The first and second metal chalcogenide layers 132, 142 may be applied, deposited, or otherwise formed onto the first and second major surfaces 122, 124 of the negative electrode current collector 120 by exposing the surfaces 122, 124 to a gaseous chalcogen. Exposing the surfaces 122, 124 of the current collector 120 to a gaseous chalcogen allows the chalcogen to chemically react with the surfaces 122, 124 of the current collector 120 and effectively form the first and second metal chalcogenide layers 132, 142 on the surfaces 122, 124, such that the layers 132, 142 uniformly and effectively conform to the contours of the surfaces 122, 124, regardless of their configuration.Furthermore, in embodiments where the current collector 120 is porous, exposing the current collector 120 to a gaseous chalcogen may cause the chalcogen to chemically react with the major surfaces 122, 124 of the current collector 120 and effectively and uniformly form the first and second metal chalcogenide layers 132, 142 thereon without physically clogging or blocking the pores of the current collector 120. The surfaces 122, 124 of the negative electrode current collector 120 may be exposed to a gaseous chalcogen for a sufficient duration for the metal on the surfaces 122, 124 of the current collector 120 to chemically react with the chalcogen and form the first and second metal chalcogenide layers 132, 142 on the surfaces 122, 124 of the current collector 120, respectively. The thicknesses of the first and second metal chalcogenide layers 132, 142 can be controlled or adjusted by controlling the duration of chalcogen exposure.The duration of chalcogen exposure may depend on the composition of the current collector 120 (e.g., copper, nickel, iron-based, and / or titanium), the temperature at which the current collector 120 is exposed to the gaseous chalcogen, and the rate at which the current collector 120 reacts with the gaseous chalcogen to form a chalcogenide.

[0040] As in Fig. 3, the chalcogen may comprise oxygen (O2) in one form, and the first and second major surfaces 122, 124 of the negative electrode current collector 120 may be exposed to gaseous oxygen by placing the current collector 120 in a closed chamber 146 and then directing an air stream 148 (about 20-22 vol.% O2) over and around the first and second major surfaces 122, 124 of the current collector 120. The air stream 148 and the current collector 120 may be heated in the chamber 146 at a sufficient temperature and for a sufficient duration to form a first metal oxide layer on the first major surface 122 of the current collector 120 and a second metal oxide layer on the second major surface 124 of the current collector 120.In particular, the air stream 148 and the current collector 120 may be heated within the chamber 146 to a temperature sufficient to promote the oxidation of the first and second major surfaces 122, 124 of the current collector 120 without melting or adversely affecting the structural integrity of the current collector 120. For example, the air stream 148 may be heated to a temperature greater than 200°C, and the current collector 120 may be heated within the chamber 146 to a temperature in the range of 200°C to 1050°C and exposed to the air stream 148 for a duration in the range of 0.1 seconds to 10 minutes to form the first metal oxide layer on the first major surface 122 of the current collector 120 and the second metal oxide layer on the second major surface 124 of the current collector 120.In one form, the current collector 120 may be heated in the chamber 146 to a temperature of approximately 900°C while exposed to the air stream 148 for a duration of approximately 10 seconds. The duration of oxygen exposure may depend on the composition of the current collector 120, the temperature at which the current collector 120 is exposed to the air stream 148, and the rate at which the current collector 120 reacts with oxygen to form an oxide.

[0041] As in Fig. 4, in other embodiments, the chalcogen may comprise sulfur (S) and / or selenium (Se), and the first and second major surfaces 122, 124 of the negative electrode current collector 120 may be exposed to gaseous sulfur and / or selenium by placing the current collector 120 together with a volume of solid-phase sulfur and / or selenium 152 in a closed chamber 150. The solid-phase sulfur and / or selenium 152 may be provided in elemental and / or compound form. The solid-phase sulfur and / or selenium 152 may be heated in the chamber 150 at a temperature in the range of 100°C to 550°C to release gaseous sulfur and / or selenium 154 into the chamber 150 around the current collector 120.The current collector 120 may be heated in the chamber 150 at a sufficient temperature and for a sufficient duration to form a first metal sulfide and / or selenide layer on the first major surface 122 of the current collector 120 and a second metal sulfide and / or selenide layer on the second major surface 124 of the current collector 120. In particular, the current collector 120 may be heated in the chamber 150 at a temperature and for a duration that allows a chemical reaction between the gaseous sulfur and / or selenium and the first and second major surfaces 122, 124 of the current collector 120 without melting or adversely affecting the structural integrity of the current collector 120.For example, the current collector 120 may be heated in the chamber 150 to a temperature in the range of 100°C to 550°C and held therein for a duration in the range of 0.1 seconds to 10 minutes to form the first metal sulfide and / or selenide layer on the first major surface 122 of the current collector 120 and the second metal sulfide and / or selenide layer on the second major surface 124 of the current collector 120.

[0042] A flow of a shielding gas (e.g., argon) 156 may be passed through the chamber 150 while heating the current collector 120 and the solid-phase sulfur and / or selenium 152 within the chamber 150 to promote physical contact between the gaseous sulfur and / or selenium 154 and the surfaces 122, 124 of the negative electrode current collector 120. In some embodiments, a negative pressure environment may be created within the chamber 150 to promote the release of gaseous sulfur and / or selenium 154 from the volume of solid-phase sulfur and / or selenium 152.In further embodiments, the solid phase sulfur and / or selenium 152 may be heated in a separate chamber (not shown) to generate a stream of gaseous sulfur and / or selenium that is supplied to the chamber 150 to promote physical contact between the gaseous sulfur and / or selenium 154 and the surfaces 122, 124 of the negative electrode current collector 120.

[0043] In some embodiments, the negative electrode current collector 120, including the first and second metal chalcogenide layers 132, 142 and the overlying first and second negative lithium metal electrode layers 112, 144, may be formed in a continuous process. Referring to Fig. 5, in a first stage of the process, an electrically conductive metal substrate 320 having a first major surface 322 and an opposite second major surface 324 may be provided. For example, the metal substrate 320 may comprise a continuous metal foil, a metal mesh, or a perforated sheet. The surfaces 322, 324 of the metal substrate 320 may be exposed to a chalcogen in the gas phase by passing the metal substrate 320 through a heated chamber 368 comprising a gaseous chalcogen 370. As described with respect to Fig. 3 and Fig.4, the metal substrate 320 may be heated to a sufficient temperature and exposed to gaseous oxygen, sulfur, and / or selenium within the chamber 368 for a duration that enables the formation of a first metal chalcogenide layer 332 on the first major surface 322 of the metal substrate 320 and a second metal chalcogenide layer 342 on the second major surface 324 of the metal substrate 320. For example, the first and second metal chalcogenide layers 332, 342 may comprise metal oxide, sulfide, and / or selenide layers.

[0044] After forming the first and second metal chalcogenide layers 332, 342 on the first and second major surfaces 322, 324 of the metal substrate 320, a first lithium metal foil 372 and / or a second lithium metal foil 374 may be provided. The first and second lithium metal foils 372, 374 may have thicknesses in the range of 5-100 µm. The first lithium metal foil 372 may be laminated to the first metal chalcogenide layer 332 on the first major surface 322 of the metal substrate 320 to form a first lithium metal layer 312, and the second lithium metal foil 374 may be laminated to the second metal chalcogenide layer 342 on the second major surface 324 of the metal substrate 320 to form a second lithium metal layer 344. The first lithium metal foil 372 may have a first side 376 and an opposite second side 378, and the second lithium metal foil 374 may have a first side 380 and an opposite second side 382.Prior to lamination, the first lithium metal foil 372 may be positioned adjacent to the metal substrate 320 such that the first side 376 of the first lithium metal foil 372 faces the first major surface 322 of the metal substrate 320 and the first side 380 of the second lithium metal foil 374 faces the second major surface 324 of the metal substrate 320. Thereafter, the first and / or second lithium metal foils 372, 374 may be laminated to the first and second metal chalcogenide layers 332, 342 on the first and second major surfaces 322, 324 of the metal substrate 320, respectively, by passing the metal substrate 320 and the first and / or second lithium metal foils 372, 374 between a pair of metal rollers 384.

[0045] Bonding the first and / or second lithium metal foils 372, 374 to the first and second metal chalcogenide layers 332, 342 may be facilitated by heating and / or maintaining the first and second metal chalcogenide layers 332, 342 to a temperature above a melting point of lithium before and / or during the lamination process. For example, the metal substrate 320 and the first and second metal chalcogenide layers 332, 342 may be heated to a temperature above the melting point of lithium before and / or during the lamination process, such that the first sides 376, 380 of the first and second lithium metal foils 372, 374 locally melt and actively wet the first and second metal chalcogenide layers 332, 342 on the metal substrate 320 during the lamination process without melting the second sides 378, 382 of the first and second lithium metal foils 372, 374.The selective and local melting of the first sides 376, 380 of the first and second lithium metal foils 372, 374 helps to create a strong chemical and physical bond between the metal foils 372, 374 and the metal chalcogenide layers 332, 342 on the metal substrate 320. The temperature of the metal substrate 320 and the first and second metal chalcogenide layers 332, 342 can be controlled during the lamination process to prevent melting of the second sides 378, 382 of the first and second lithium metal foils 372, 374, thus maintaining the structural integrity of the foils 372, 374 during the lamination process. For example, the metal substrate 320 and the first and second metal chalcogenide layers 332, 342 may be heated to a temperature in the range of 250°C to 450°C immediately before and / or during the lamination process.The specific temperature at which the metal substrate 320 and the first and second metal chalcogenide layers 332, 342 are heated depends on the composition of the metal substrate 320 and the first and second metal chalcogenide layers 332, 342. The second sides 378, 382 of the first and second lithium metal foils 372, 374 may be maintained at a temperature below the melting point of lithium, e.g., below 180°C, during the lamination process.

[0046] After forming the first and second lithium metal layers 312, 344, the metal substrate 320 can be formed into the desired size and shape of one or more negative electrode current collectors (not shown) and used in the manufacture of one or more electrochemical cells of a lithium metal battery. In this case, the first and second lithium metal layers 312, 344 can comprise first and second negative lithium metal electrode layers.

[0047] The above description of the preferred exemplary embodiments, aspects, and specific examples is merely descriptive; it is not intended to limit the scope of the following claims. Each term used in the appended claims should be understood in its ordinary and generic meaning unless expressly and clearly stated otherwise in the specification.

Claims

[1] A method of manufacturing an electrochemical cell, the method comprising: Providing a porous or non-porous metal substrate; Exposing a surface of the metal substrate to a chalcogen in the gas phase so that a conformal metal chalcogenide layer forms on the surface of the metal substrate; Providing a lithium metal foil having a first surface and an opposite second surface; and Laminating the lithium metal foil onto the metal chalcogenide layer on the surface of the metal substrate, so that the first surface of the lithium metal foil physically and chemically bonds to the metal chalcogenide layer on the surface of the metal substrate, wherein the surface of the metal substrate and the metal chalcogenide layer are heated to a temperature above a melting point of lithium, so that when the lithium metal foil is laminated to the metal chalcogenide layer on the surface of the metal substrate, the first surface of the lithium metal foil melts locally and actively wets the metal chalcogenide layer on the surface of the metal substrate without melting the second surface of the lithium metal foil, wherein the surface of the metal substrate and the metal chalcogenide layer are heated to a temperature in the range of 250 °C to 450 °C before the lithium metal foil is laminated to the metal chalcogenide layer on the surface of the metal substrate, and wherein the second surface of the lithium metal foil is maintained at a temperature below 180 °C before the lithium metal foil is laminated to the metal chalcogenide layer on the surface of the metal substrate. [2] The method according to claim 1, wherein the lithium metal foil is laminated to the metal chalcogenide layer on the surface of the metal substrate by positioning the lithium metal foil adjacent to the metal substrate such that the first surface of the lithium metal foil is opposite to the surface of the metal substrate, and then passing the metal substrate and the lithium metal foil between a pair of metal rollers. [3] The method of claim 1, wherein the chalcogen comprises oxygen and the metal chalcogenide layer comprises a metal oxide, and wherein the surface of the metal substrate is exposed to gaseous oxygen by heating the metal substrate in air so that the gaseous oxygen chemically reacts with and bonds to the surface of the metal substrate. [4] A method according to claim 1, wherein the chalcogen comprises sulfur or selenium and the metal chalcogenide layer comprises a metal sulfide or a metal selenide, and wherein the surface of the metal substrate is exposed to gaseous sulfur or selenium by heating a volume of solid phase sulfur or selenium to release a volume of gaseous sulfur or selenium therefrom, and thereafter the surface of the metal substrate is exposed to the volume of gaseous sulfur or selenium such that the gaseous sulfur or gaseous selenium chemically reacts with and bonds to the surface of the metal substrate. [5] The method of claim 1, wherein the metal substrate has a thickness in the range of 8-20 µm, the metal chalcogenide layer has a thickness in the range of 1-500 nm, and the lithium metal foil has a thickness in the range of 5-100 µm. [6] The method of claim 1, comprising forming the metal substrate into a negative electrode current collector having a desired size and shape and having at least one negative lithium metal electrode layer physically and chemically bonded thereto. [7] A method of manufacturing an electrochemical cell, the method comprising: Providing a porous or non-porous metal substrate having a first surface and an opposite second surface; Exposing the first and second surfaces of the metal substrate to a chalcogen in the gas phase such that a first metal chalcogenide layer forms on the first surface of the metal substrate and a second metal chalcogenide layer forms on the second surface of the metal substrate; Providing a first lithium metal foil and a second lithium metal foil, each of the first and second lithium metal foils having a first surface and an opposite second surface; and Laminating the first and second lithium metal foils, respectively, to the first and second metal chalcogenide layers on the first and second surfaces of the metal substrate such that the first surface of the first lithium metal foil physically and chemically bonds to the first metal chalcogenide layer on the first surface of the metal substrate and the first surface of the second lithium metal foil physically and chemically bonds to the second metal chalcogenide layer on the second surface of the metal substrate, wherein the metal substrate and the first and second metal chalcogenide layers are heated to a temperature above a melting point of lithium such that when the first and second lithium metal foils are respectively laminated to the first and second metal chalcogenide layers on the first and second surfaces of the metal substrate,locally melting the first surface of the first lithium metal foil and actively wetting the first metal chalcogenide layer on the first surface of the metal substrate without melting the second surface of the first lithium metal foil, and locally melting the first surface of the second lithium metal foil and actively wetting the second metal chalcogenide layer on the second surface of the metal substrate without melting the second surface of the second lithium metal foil.

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