Metal layer comprising lithium through grains or lithium alloy through grains

Abstract

The invention more specifically relates to a metal layer comprising lithium metal through grains or lithium alloy through grains having improved electrochemical properties, a simple and easy-to-industrialize method for manufacturing such a metal layer, the use of such a metal layer as a negative electrode to improve the battery life of lithium metal, and a method for manufacturing such a metal layer. And a lithium metal battery comprising such a metal layer as a negative electrode.

Description

[0001] This invention relates to the field of lithium rechargeable batteries, particularly for the production of electric vehicles and / or storage of intermittent energy sources such as wind and / or solar energy.

[0002] More specifically, this invention relates to a metal layer comprising lithium metal through-grains or lithium alloy through-grains, having improved electrochemical performance; a simple and readily industrializable method for manufacturing such a metal layer; the use of such a metal layer as a negative electrode to improve the lifespan of lithium metal batteries; and a lithium metal battery comprising such a metal layer as a negative electrode.

[0003] Currently available lithium metal polymer (or LMP®) batteries are "all-solid-state" batteries, typically in the form of multiple wound thin films or multiple stacked thin films. These wound or stacked films generally contain at least four functional films: a negative electrode (anode) that ensures lithium-ion supply during discharge; a positive electrode (cathode) that acts as a lithium-ion intercalation container; a solid polymer electrolyte that conducts lithium ions and is located between the positive and negative electrodes; and a current collector connected to the positive electrode to ensure electrical connection. The negative electrode is typically composed of a lithium metal sheet or lithium alloy sheet; the solid polymer electrolyte is typically composed of a polyethylene oxide (PEO)-based polymer and at least one lithium salt; the positive electrode contains an active electrode material, typically based on a metal oxide (e.g., V₂O₅, LiV₃O₈, LiCoO₂, LiNiO₂, LiMn₂O₄, or LiNi 0.5 Mn 0.5 O2) or phosphate-based solutions such as LiMPO4, where M represents a metal cation selected from Fe, Mn, Co, Ni, and Ti and combinations thereof, and optionally carbon; the current collector is typically made of a metal sheet. In particular, the presence of a solid polymer electrolyte can eliminate the dendrite problem that rapidly occurs in conventional separators impregnated with liquid electrolytes, such as those used in lithium-ion batteries. For lithium metal batteries, during charging, fresh lithium metal (Li) 0 The layer is deposited on the negative electrode and then consumed during discharge.

[0004] Currently, the production of lithium metal anodes for all-solid-state batteries involves extruding lithium metal ingots and rolling the extruded lithium to form lithium metal sheets. Specifically, lithium metal ingots are extruded to form a coil with a thickness of approximately 250 µm; the resulting extruded coil is then fed into a rolling mill. Rolling can be performed using a lubricant to obtain the rolled coil. The rolling thickness is typically 58 to 72 µm. Current processes for large-scale production of lithium metal anodes have drawbacks due to the properties of the lithium metal itself, which may react with and / or deform and adhere to the contacting rolls, and / or the extreme ductility of lithium or its alloys, which reduces the tensile stress that can be applied to the lithium film at the roll exit to prevent the lithium film from cracking or tearing.

[0005] Furthermore, current solid-state lithium metal batteries on the market are not entirely satisfactory due to their still high cost and limited lifespan (or cycle performance). In particular, several issues have been raised related to the use of lithium metal anodes: the lithium plating and dissolution process of the anode, and the reactivity of lithium metal with battery components (mainly the electrolyte). Specifically, it is known that the lifespan of all-solid-state batteries is largely related to the degradation of the lithium metal anode.

[0006] Many solutions have been considered to overcome the problems associated with using lithium metal, such as designing solid electrolytes with improved mechanical and ion conduction properties, designing novel anode structures, or applying a protective layer to the surface of lithium metal anodes.

[0007] For example, patent application US2021 / 265618 describes a layer located at the interface between a lithium metal anode and a solid electrolyte layer, the layer comprising a specific surface area greater than 500 m² facing the solid electrolyte layer. 2 / g porous carbon; and nanostructures facing the lithium metal anode layer and penetrating the porous carbon. Such interface layers can be prepared using 3D printing techniques as well as complex and expensive physical, chemical, or electrochemical deposition methods. Furthermore, adding an extra layer to the battery can be a drawback when attempting to minimize battery size.

[0008] A recent publication, Storelli et al., J. Electrochem. Soc., 2021, 168, 040505, describes the use of two types of lithium foil with polyethylene oxide (PEO) electrolyte and discloses that reducing the surface roughness of the lithium foil can improve the lifespan of lithium batteries. Furthermore, a surface pretreatment involving subjecting the lithium foil to a first cycle at a low current density, followed by a significant increase in the cycle current density, further improves battery life. However, this approach appears difficult to industrialize.

[0009] Therefore, new, lower-cost, and easier-to-implement technologies, especially on an industrial scale, are needed to improve the lifespan of solid lithium metal batteries.

[0010] The object of the present invention is achieved by the following description of a metal layer based on lithium metal or a metal alloy and a method for manufacturing the same.

[0011] Specifically, the inventors of this application have unexpectedly discovered that a metal layer can be provided in which lithium metal or lithium alloy is in the form of through grains of a specific size, so that the layer has a microstructure suitable for improving the life of lithium batteries.

[0012] The metal layer of the present invention has a uniform microstructure, thereby improving mechanical and electrochemical properties.

[0013] Therefore, the first subject of the present invention is a metal layer comprising lithium or a lithium alloy, preferably for use in lithium metal batteries, said metal layer having a diameter D along the normal direction. N The extended thickness e, along the lateral direction D T The width L of the extension and the rolling direction D L The length of the extension is l, and the direction is D. N D T and D L They are orthogonal to each other, characterized by:

[0014] * The metal layer contains lithium through grains or lithium alloy through grains.

[0015] * Each penetrating grain is formed by at least one direction D parallel to the normal. N The grain size d extending in the direction of the direction GN (unit: µm) and by D T and D L At least one grain surface area S on the defined plane G (Unit: mm) 2 Defined by ), such that:

[0016] * d GN = e (unit: µm), and

[0017] * S G ≥ 1.5 × π × [(2.9 × e) / 2] 2 S is preferred G ≥ 2.0 × π × [(2.9 × e) / 2] 2 S is the preferred choice G ≥ 2.5 × π × [(2.9 × e) / 2] 2 S is a more preferred choice G ≥ 3 × π × [(2.9 × e) / 2] 2 .

[0018] The metal layer of the first subject of the present invention is a single layer, i.e., a single layer.

[0019] Because along the direction parallel to the normal, D N The grain size d extending in the direction of the direction GN and in D T and D L The grain surface area S on the defined plane G Lithium grains or lithium alloy grains impart a specific microstructure to the metal layer, thereby producing better electrochemical performance.

[0020] In this invention, along the direction parallel to the normal D N The grain size d extending in the direction of the directionGN Measurements can be taken by microscopes (especially optical and / or electron microscopes), tomography, or using a measuring probe, with microscopes (especially optical and / or electron microscopes) being preferred.

[0021] In this invention, the grain surface area S G It can be determined using microscopy (especially optical and / or electron microscopy) combined with image processing software. Grain surface area S G The value corresponds to the average value of the 100 grains analyzed.

[0022] In this invention, S G ≥ 1.5 × π × [(2.9 × e) / 2] 2 S is preferred G ≥ 2.0 × π ×[(2.9 × e) / 2] 2 S is the preferred choice G ≥ 2.5 × π × [(2.9 × e) / 2] 2 S is a more preferred choice G ≥ 3 ×π × [(2.9 × e) / 2] 2 .

[0023] According to a preferred embodiment of the invention, the metal layer of the invention is a self-supporting layer. In other words, it has sufficient mechanical strength to not require a support or substrate. According to this preferred embodiment of the invention, such a metal layer is therefore not deposited on a support or substrate. This also means that the metal layer of the invention has sufficient conductivity to eliminate the need for a current collector when manufacturing a battery containing such a layer as a negative electrode. According to this preferred embodiment of the invention, such a metal layer is therefore not deposited on a current collector.

[0024] The thickness e of the lithium or lithium alloy-containing metal layer of the present invention can be 100 µm or less, preferably 90 µm or less, and particularly preferably 80 µm or less. Beyond 100 µm, the microstructure of the metal layer has a smaller impact on improving cycle performance.

[0025] The metal layer preferably has a thickness e of 1µm or greater, particularly preferably 2µm or greater, and more preferably 5µm or greater.

[0026] In the metal layer, lithium or lithium alloy may account for at least about 90% by weight of the total weight of the metal layer containing lithium or lithium alloy, preferably at least about 95% by weight, and particularly preferably about 96% to 99% by weight of the total weight of the metal layer containing lithium or lithium alloy.

[0027] According to a particularly preferred embodiment of the invention, the metal layer is composed of lithium or a lithium alloy (i.e., it contains about 100% by weight of lithium or a lithium alloy relative to the total weight of the metal layer).

[0028] In this invention, the characteristic of penetrating the grain is that at least one direction D is parallel to the normal. N The grain size d extending in the direction of the direction GN (Unit: µm), where d GN = e (unit: µm), where e is the thickness of the metal layer.

[0029] According to a preferred embodiment of the invention, the metal layer comprises at least 90% by weight, preferably at least 95% by weight, and particularly preferably only (i.e., 100%) lithium through grains or lithium alloy through grains, accounting for at least 90% by weight of the total weight of lithium grains or lithium alloy grains present in the metal layer.

[0030] Lithium metal corresponds to lithium (Li) with an oxidation state of zero. 0 ).

[0031] Lithium alloys can be lithium alloys, such as alloys of lithium with elements selected from silicon (Si), tin (Sn), aluminum (Al), germanium (Ge), lead (Pb), bismuth (Bi), antimony (Sb), silver (Ag), zinc (Zn), indium (In), magnesium (Mg), and mixtures of at least two of the above elements.

[0032] Lithium preferably accounts for at least about 40% of the total weight of the lithium alloy, particularly preferably at least about 80% by weight, and more preferably at least about 90% by weight.

[0033] In one specific implementation, the average extrapolated diameter d throughout the grain is... G (Unit: µm) ≥ 3.5 × e, preferably d G (Unit: µm) ≥ 5 × e. In the metal layer of the present invention, the lithium or lithium alloy grains are larger than those in lithium-based metal layers of the prior art. This endows the metal layer of the present invention with a specific microstructure that is beneficial to improving cycle performance.

[0034] In this invention, the average extrapolated diameter of the grain can be derived from the grain surface area S as defined above. G This is determined by modeling lithium or lithium alloy grains as circular. The average extrapolated diameter of the grains can then be obtained using the following relationship: S G =π × (d G / 2) 2 [or d] G = 2 × √(S G / π).

[0035] Because the size and / or surface area of ​​lithium-through grains or lithium alloy-through grains are larger than the surface area in prior art metal layers, the through grain density can be reduced. Through grain density depends on the thickness of the metal layer.

[0036] Preferably, the lithium through-grain or lithium alloy through-grain density of the metal layer according to the present invention is expressed in units of grains per mm. 2 < 151230 × (layer thickness, unit: µm) -2 Therefore, for a given thickness, the metal layer according to the invention preferably has a lithium through-grain or lithium alloy through-grain density lower than the grain density obtained according to Frost's law (the power law relationship between film thickness). In contrast, prior art metal layers follow Frost's law.

[0037] More specifically, lithium through-grain or lithium alloy through-grain density, in units of grains / mm. 2 ≤ 101786 × (layer thickness, unit: µm) -2 More specifically, lithium through-grain or lithium alloy through-grain density, in units of grains / mm. 2 ≤50893 × (layer thickness, unit: µm) -2 .

[0038] The metal layer according to the invention is preferably in the form of a film or foil.

[0039] A second aspect of the present invention is a method for manufacturing a metal layer according to the first aspect, characterized by comprising at least the following steps:

[0040] - Step i) Prepare a metal laminate comprising at least three metal layers containing lithium or lithium alloy, each metal layer containing lithium through grains or lithium alloy through grains and having initial thicknesses ei1, ei2, ei3, and

[0041] - Step ii) Roll the metal laminate to a final thickness ef = e, such that ef ≤ ei1, ef ≤ ei2, and ef ≤ ei3.

[0042] The method of the present invention enables the formation of a single metal layer conforming to the first subject matter of the present invention from at least three metal layers.

[0043] Step i)

[0044] The method of the present invention is easy to implement and industrialize, and can obtain a metal layer that conforms to the first subject of the present invention, i.e. has a specific microstructure that leads to improved cycle performance, in just a few steps.

[0045] According to a preferred embodiment of the method of the present invention, step i) includes extruding a lithium or lithium alloy ingot i-1) and rolling i-2) to form the at least three lithium or lithium alloy-containing metal layers, followed by compositing the metal layers i-3), preferably at a pressure of 0.1 N / mm. 2 Up to 1.0 N / mm 2 The operation was carried out at speeds ranging from 0.5 m / min to 50 m / min.

[0046] Therefore, each metal layer containing lithium or lithium alloy is formed according to steps i-1) and i-2), and then the metal layers are aggregated together for composite step i-3).

[0047] Extrusion (i-1) is preferably carried out in a temperature range of 20°C to 100°C.

[0048] The rolling of the extruded ingot (i-2) can be carried out in a temperature range of 20°C to 130°C.

[0049] The rolling of the extruded ingot (i-2) can be carried out at speeds ranging from 1 m / min to 70 m / min.

[0050] The rolling of the extruded ingot (i-2) can be carried out in the force range of 5kN to 35kN.

[0051] The rolling process in step i) i-2) is preferably performed using a rolling mill containing at least two work rolls. This allows the extruded ingot to pass between the two rolls.

[0052] Preferably, the rolling i-2) in step i) is performed using a lubricant and / or an anti-stick co-wound film.

[0053] It is preferable to add it at the entrance of the mill, and advantageously before the extruded ingot passes through the two rolls.

[0054] The lubricant can be selected from volatile siloxanes, such as methylsiloxanes, particularly polydimethylsiloxane, hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane and dodecyl dihydrohexasiloxane.

[0055] The composite of the at least three metal layers (i-3) can be carried out in a temperature range of 20°C to 130°C.

[0056] Lamination can be performed using a laminating machine, which is known in the prior art and to those skilled in the art.

[0057] At the end of the composite process, each metal layer of the metal laminate contains lithium through grains or lithium alloy through grains and has an initial thickness ei1, ei2, ei3.

[0058] Each metal layer of the laminate obtained in steps i), i-2), or i-3) contains a through grain. This means that the through grain in each layer i is characterized by at least one through grain along a direction parallel to the normal D. N The grain size d extending in the direction of the direction GNi (Unit: µm), where d GNi = ei (unit: µm), where ei is the thickness of the metal layer. In other words, for a laminate containing three metal layers (each with an initial thickness ei1, ei2, ei3), the first metal layer contains lithium through grains or lithium alloy through grains, characterized in that at least one is located along a direction parallel to the normal D. N Extended grain size d GNi1 (Unit: µm), where d GNi1 = ei1 (unit: µm); the second metal layer comprises lithium through grains or lithium alloy through grains, characterized in that at least one along the direction parallel to the normal D N Extended grain size d GNi2 (Unit: µm), where d GNi2 = ei2 (unit: µm); the third metal layer comprises lithium through grains or lithium alloy through grains, characterized in that at least one along the direction parallel to the normal D N Extended grain size d GNi3 (Unit: µm), where d GNi3 = ei3 (unit: µm).

[0059] Preferably, the at least three metal layers of the metal laminate have substantially the same initial thickness ei1, ei2, ei3, i.e., the thickness variation between them is in the range of 0 to 10%.

[0060] At the end of step i), particularly at the end of composite i-3), the thickness of the metal laminate is 300µm or less, preferably 250µm or less, and particularly preferably 200µm or less.

[0061] The thickness of metal laminates is typically 30µm or greater.

[0062] In each of the at least three lithium or lithium alloy-containing metal layers obtained or forming the laminate at the end of step i-2), lithium or lithium alloy may account for at least about 90% by weight of the total weight of the lithium or lithium alloy-containing metal layers, preferably at least about 95% by weight, and particularly preferably about 96% to 99% by weight of the total weight of the lithium or lithium alloy-containing metal layers.

[0063] The thickness of each of the at least three lithium or lithium alloy metal layers obtained at the end of step i-2) may be 100µm or less, preferably 90µm or less, and particularly preferably 80µm or less.

[0064] Each of the at least three lithium or lithium alloy metal layers obtained in step i-2) preferably has a thickness of 1µm or greater, particularly preferably 2µm or greater, and more preferably 5µm or greater.

[0065] Step ii)

[0066] The subsequent step ii) involves performing a new rolling step to reduce the thickness of the laminate and form a final thickness ef, which is equal to the thickness e of the metal layer as defined in the first subject matter of this invention.

[0067] Step ii) is preferably carried out under conditions where the force f is between 5 kN and 35 kN.

[0068] Step ii) is preferably carried out at a speed v of 1 m / min to 70 m / min.

[0069] Step ii) can be performed in a temperature range of 20°C to 130°C.

[0070] Step ii) is preferably performed using a rolling mill containing at least two work rolls. This allows the laminate to pass between the two rolls.

[0071] Preferably, step ii) is performed using a lubricant and / or an anti-stick co-wound film.

[0072] The lubricant can be selected from volatile siloxanes, such as methylsiloxanes, particularly polydimethylsiloxane, hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane and dodecylhexasiloxane.

[0073] The lubricant is preferably added at the mill inlet, advantageously before the laminate passes through the two rolls.

[0074] According to a preferred embodiment of the invention, the final thickness ef is equal to the smallest of the initial thicknesses ei1, ei2 and ei3.

[0075] The third subject of the present invention is the use of a metal layer according to the first subject of the present invention or a metal layer obtained by the method according to the second subject of the present invention as a negative electrode to improve the cycle performance of a lithium metal battery.

[0076] As described above, the metal layer of the present invention has a specific microstructure of lithium or lithium alloy grains, which endows it with good electrochemical performance, especially when used as the negative electrode or anode of a lithium metal battery.

[0077] Therefore, the fourth subject of the present invention is a lithium metal battery, which comprises:

[0078] - At least one positive electrode,

[0079] - At least one negative electrode, and

[0080] - At least one solid or quasi-solid electrolyte located between the positive and negative electrodes.

[0081] The negative electrode is characterized by being a metal layer according to the first subject of the present invention or a metal layer obtained by a method according to the second subject of the present invention.

[0082] In this invention, the "solid or quasi-solid" electrolyte is in solid or gel form at room temperature (i.e., a temperature of 18°C ​​to 25°C), preferably in solid form.

[0083] The solid or quasi-solid electrolyte of the battery of the present invention preferably contains one or more polymer materials.

[0084] The polymeric material of the solid or quasi-solid electrolyte (or multiple polymeric materials when there are multiple types) preferably accounts for at least about 30% by weight of the total weight of the solid or quasi-solid electrolyte, and particularly preferably at least about 40% by weight.

[0085] Solid or quasi-solid electrolytes may be polymer electrolytes, which contain:

[0086] - At least one lithium salt and at least one polyethylene oxide (PEO) based polymer material, or

[0087] - At least one cationic monopolar conductive polymer.

[0088] Polymer materials based on polyethylene oxide (PEO) can be selected from polystyrene-polyethylene oxide (PS-b-PEO) block copolymers, polystyrene-polyethylene oxide-polystyrene (PS-b-PEO-b-PS) block copolymers, random poly(ethylene oxide-co-propylene oxide) copolymers (i.e., PEO-ran-PPO), random poly(ethylene oxide-co-butene oxide) copolymers (i.e., PEO-ran-PBO), polyethylene oxide and mixtures thereof.

[0089] Lithium salts used in combination with polyethylene oxide-based polymer materials can be selected from lithium fluoride (LiFO3), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium metaborate (LiBO2), lithium perchlorate (LiClO4), lithium nitrate (LiNO3), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(pentafluoroethylsulfonyl)imide (LiBETI), LiAsF6, LiCF3SO3, LiSbF6, LiSbCl6, Li2TiCl6, Li2SeCl6, and Li2B. 10 Cl 10 Li2B 12 Cl 12 One of lithium bis(oxalato)borate (LiBOB) and its mixtures.

[0090] The lithium salt preferably accounts for 5% to 30% of the total weight of the polymer electrolyte, more preferably 10% to 25% by weight.

[0091] The polyethylene oxide (PEO)-based polymer material can be combined with reinforcing agents. This allows for the modification of the polymer material's mechanical properties.

[0092] The reinforcing agent is preferably selected from cellulose nanofibers, ceramic nanoparticles such as titanium dioxide, alumina or silica nanoparticles, and fluorinated polymers and copolymers such as polyvinylidene fluoride (PVdF) or a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-co-HFP).

[0093] A unipolar conductive polymer can be a polymer (homogeneous polymer or copolymer) comprising at least one organic polymer chain, an organic anionic functional group forming a covalent bond with the organic polymer chain, and a metal cation (ionicly) bonded to the organic anionic functional group.

[0094] In this invention, a cationic unipolar conductive polymer refers to a polymer (homogeneous polymer or copolymer) comprising at least one organic polymer chain, an organic anionic functional group forming a covalent bond with the organic polymer chain, and a metal cation bonded to the organic anionic functional group. These metal cations are mobile species responsible for polymer ion conduction.

[0095] The term "organic polymer chain" refers to a polymer chain that does not contain metals or metalloids. In other words, an organic polymer chain does not contain metals or metalloids such as silicon, or is different from a polysiloxane chain, or does not contain Si-O bonds.

[0096] The term "organic anionic functional group" refers to anionic functional groups that do not contain metals or metalloids. In other words, organic anionic functional groups do not contain metals or metalloids such as silicon, or do not contain Si-O bonds.

[0097] The cationic unipolar conductive polymer of the present invention is a polymer comprising an organic anionic repeating unit (an organic polymer chain and an organic anionic functional group covalently bonded to the organic chain), wherein the organic anionic repeating unit is ionicly bonded to a metal cation.

[0098] Cationic monopolar conductive polymers can be:

[0099] - A homopolymer capable of being prepared from: a) a monomer comprising at least one organic anionic functional group covalently grafted onto the monomer and at least one metal cation bonded to the organic anionic functional group; or

[0100] - A copolymer that can be prepared from: a) a monomer comprising at least one organic anionic functional group covalently grafted onto the monomer and at least one metal cation bound to the organic anionic functional group, and b) at least one monomer other than monomer a), selected from b1) a monomer comprising at least one organic anionic functional group covalently grafted onto the monomer and at least one metal cation bound to the organic anionic functional group, and b2) an organic monomer.

[0101] The term "organic monomer (b2)" refers to a monomer that does not contain metals or metalloids. In other words, an organic monomer does not contain metals or metalloids such as silicon, and / or is not a compound containing Si-O bonds.

[0102] The (monomer) metal cation or (polymer) metal cation bonded to an organic anionic functional group is preferably Li. + cation.

[0103] Monomer a) or b1), i.e., a monomer comprising at least one organic anionic functional group covalently grafted onto the monomer and at least one metal cation bonded to the organic anionic functional group, may be selected from aromatic and non-aromatic vinyl monomers comprising at least one organic anionic functional group covalently grafted onto the organic monomer and at least one metal cation bonded to the organic anionic functional group.

[0104] Examples of aromatic vinyl monomers include styrene and its derivatives.

[0105] The styrene derivatives are preferably derivatives in which the phenyl portion of styrene is replaced by one or more groups selected from methyl, ethyl and tert-butyl.

[0106] Examples of non-aromatic vinyl monomers include acrylates, methacrylates, acrylamides, methacrylamides, ethylene, propylene, dienes, or maleimides.

[0107] Organic monomer b2) can be vinylidene fluoride, phosphate ester, phosphonate ester, ether, carbonate ester, malonic ester, amide, acrylate, acid anhydride or ester.

[0108] In this embodiment, the copolymer, in addition to containing repeating organic anionic units that bind to metal cations, also contains repeating units of vinylidene fluoride, phosphate esters, phosphonates, ethers, carbonates, malonic esters, amides, acrylates, acid anhydrides, or esters.

[0109] The organic anionic functional groups of (monomers a) and b1) or (polymers) may be selected from sulfonate, borate and imine anionic functional groups.

[0110] The organic anionic functional group is preferably an imine anion, particularly preferably a bis(sulfonyl)imide anion, even more preferably a bis(trifluoromethanesulfonyl)imide anion (TFSI) or a sulfonyl(fluorosulfonyl)imide anion (FSI), even more preferably a bis(trifluoromethanesulfonyl)imide anion (TFSI).

[0111] When the polymer electrolyte contains a cationic monopolar conductive polymer, it preferably does not contain an additional lithium salt.

[0112] The cationic monopolar conductive polymer can be combined with a reinforcing agent. This allows for the tuning of its mechanical properties.

[0113] The reinforcing agent is preferably selected from cellulose nanofibers, ceramic nanoparticles such as titanium dioxide, alumina or silica nanoparticles, and fluorinated polymers and copolymers such as polyvinylidene fluoride (PVdF) or a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-co-HFP).

[0114] The polymer electrolyte may also contain at least one plasticizer or non-aqueous solvent. This allows the formation of a gel-like polymer electrolyte (i.e., gel form).

[0115] The non-aqueous solvent or plasticizer may be selected from linear and cyclic carbonates such as propylene carbonate, ethylene carbonate or dimethyl carbonate; fluorinated carbonates such as fluoroethylene carbonate, nitriles such as succinic acid, lactones such as γ-butyrolactone, linear or cyclic polyethers, fluorinated polyethers, sulfur-containing solvents such as sulfolane and dimethyl sulfoxide; and mixtures thereof.

[0116] Such non-aqueous solvents or plasticizers specifically include dimethyl ether, polyethylene glycol dimethyl ether (or PEGDME) such as tetraethylene glycol dimethyl ether (TEGDME), dioxolane, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl isopropyl carbonate (MiPC), ethyl acetate, ethyl butyrate (EB), or a mixture thereof.

[0117] Preferably, the solvent or plasticizer accounts for about 10% to 70% of the total weight of the polymer electrolyte, more preferably about 20% to 60% by weight.

[0118] Solid or quasi-solid electrolytes are preferably in membrane form.

[0119] Preferably, the thickness of the solid or quasi-solid electrolyte membrane is 5µm to 45µm, more preferably 10µm to 25µm.

[0120] Solid or quasi-solid electrolytes can be prepared by any technique known to those skilled in the art, such as by coating, extrusion, or pressing (cold pressing or hot pressing).

[0121] The positive electrode may include a positive electrode active material, an optional electronically conductive agent, and an optional polymer material.

[0122] The active material of the positive electrode is a reversible lithium-ion active material. In other words, lithium ions can be reversibly inserted or extracted.

[0123] The positive electrode active material can be:

[0124] - Metal oxides, such as vanadium oxide (VO) x (2 ≤ x ≤ 2.5), LiV3O8, Li y Ni 1-x Co x O2 (0 ≤ x ≤ 1; 0 ≤ y ≤ 1), manganese spinel Li y Mn 1-x M x O2 (M = Cr, Al, V, Ni, 0 ≤ x ≤ 0.5; 0 ≤ y≤ 2), V2O5, LiCoO2, LiNiO2, LiMn2O4 and LiNi 0.5 Mn 0.5 O2, Li(Ni) 1-x-y Mn x Co y O2, LiNi x CO y Al z O2 (x + y + z = 1), or

[0125] - Phosphosilicates or metal phosphates, such as LiMPO4, where M represents a metal cation selected from Fe, Mn, Co, Ni, and Ti, and combinations thereof, such as LiFePO4 or LiMnFePO4, or

[0126] - Metal sulfates, such as ferric sulfate Fe2(SO4)3.

[0127] The active material for the positive electrode is preferably selected from iron phosphate and its derivatives, especially LiFePO4.

[0128] The electronic conductive agent can be selected from carbon black, acetylene black, carbon fibers and nanofibers, carbon nanotubes, graphene, graphite, metal particles and metal fibers of at least one conductive metal such as aluminum, platinum, iron, cobalt and nickel, and mixtures thereof.

[0129] The active material of the positive electrode can account for about 60% to 95% of the total weight of the positive electrode, preferably about 70% to 90% by weight.

[0130] The electronically conductive agent may account for about 0.1% to 10% of the total mass of the positive electrode, preferably about 0.3% to 5% by mass.

[0131] The polymeric materials may be selected from ethylene homopolymers and copolymers, propylene homopolymers and copolymers; ethylene oxide (e.g., PEO, PEO copolymers), formaldehyde, propylene oxide, epichlorohydrin, allyl glycidyl ether homopolymers and copolymers thereof; halogenated polymers such as vinyl chloride, vinylidene fluoride (PVdF), vinylidene chloride, tetrafluoroethylene or trifluorochloroethylene homopolymers and copolymers, vinylidene fluoride and hexafluoropropylene copolymer (PVdF-co-HFP) or mixtures thereof; electronically nonconductive anionic polymers such as poly(styrene sulfonic acid), poly(acrylic acid), poly(glutamic acid), alginate, pectin, gelatin or mixtures thereof; cationic polymers such as polyethyleneimine (PEI), polyaniline in the form of emeraldine salt (ES), quaternized poly(N-vinylimidazolium), poly(acrylamide-diallyldimethylammonium chloride) (AMAC) or mixtures thereof; polyacrylates; lithium salt anionic substituted anionic polymers; and mixtures thereof.

[0132] Anionic polymers substituted with lithium salt anions are as defined in this invention.

[0133] Polymer materials can be, in particular, polyethylene oxide (PEO) based polymers or anionic polymers substituted with lithium salt anions.

[0134] The active material of the positive electrode can account for about 1% to 25% of the total weight of the positive electrode, preferably about 5% to 20% by weight.

[0135] According to a particularly preferred embodiment of the invention, the active material of the positive electrode is coated with a carbon layer. The presence of the carbon layer improves the interface between the active material and the polymer material.

[0136] The carbon coating of the active material preferably accounts for about 0.1% to 5% by weight of the active material.

[0137] The carbon layer is preferably in the form of a layer with a thickness variation of about 1 nm to 4 nm.

[0138] The cathode may also contain lithium salt, preferably 1% to 20% by weight of lithium salt based on the total weight of the cathode, and more preferably 1% to 10% by weight of lithium salt.

[0139] Lithium salts can be as defined in this invention.

[0140] The positive electrode is preferably in membrane form.

[0141] Preferably, the thickness of the positive electrode is 20µm to 100µm, and more preferably 40µm to 50µm.

[0142] Lithium batteries may also include a current collector connected to the positive electrode.

[0143] Current collectors are typically composed of metal sheets.

[0144] The current collector is preferably made of stainless steel or aluminum and optionally covered with a carbon base layer (anti-corrosion layer).

[0145] In the battery of the present invention, the negative electrode is preferably in direct physical contact with the solid or quasi-solid electrolyte. In other words, this means that preferably no intermediate layer is inserted between the negative electrode and the solid or quasi-solid electrolyte.

[0146] In the battery of the present invention, the positive electrode is preferably in direct physical contact with the solid or quasi-solid electrolyte. In other words, this means that preferably no intermediate layer is inserted between the positive electrode and the solid or quasi-solid electrolyte.

[0147] The present invention is illustrated by the following embodiments, but is not limited thereto.

[0148] Brief description of the attached figures

[0149] The accompanying drawings illustrate the present invention.

[0150] Figure 1 The metal layer according to the invention is shown, having a D along the normal direction. N The extended thickness e, along the lateral direction D T The width L of the extension and the rolling direction D L The length of the extension is l, and the direction is D. N D T and D L Orthogonal to each other; and lithium through grains or lithium alloy through grains within the metal layer, which are formed by D along a direction parallel to the normal. N The grain size d extending in the direction of the direction GN (unit: µm) and in D T and D L The grain surface area S on the defined plane G (Unit: mm)2 ) is defined such that d GN = e (unit: µm).

[0151] Figure 2 The display shows a surface area S G Lithium-penetrating grains or lithium alloy-penetrating grains, and their average extrapolated diameter d G Modeling in the form of a circle.

[0152] Figure 3 The display shows the changes in capacity (in mAh / g) and efficiency (in %) of batteries that do not conform to the present invention as a function of the number of cycles.

[0153] Figure 4 The internal resistance Ri (unit: Ohm / cm) of the battery does not conform to the present invention. 2 (This varies with the number of iterations.)

[0154] Figure 5 The battery capacity (in mAh / g) and efficiency (in %) according to the present invention are shown as a function of the number of cycles.

[0155] Figure 6 The internal resistance Ri (unit: Ohm / cm) of the battery according to the present invention is shown. 2 (This varies with the number of iterations.)

[0156] Figure 7 The battery capacity (in mAh / g) and efficiency (in %) according to the present invention are shown as a function of the number of cycles.

[0157] Figure 8 The internal resistance Ri (unit: Ohm / cm) of the battery according to the present invention is shown. 2 (This varies with the number of iterations.) Example

[0158] Unless otherwise stated, all materials listed herein are for use as received from the manufacturer.

[0159] Example 1: Manufacturing a lithium metal film

[0160] An 18µm thick lithium metal film conforming to the present invention was prepared according to the detailed operating conditions below.

[0161] Three lithium metal layers with a thickness of approximately 18 µm were obtained by extruding lithium ingots at 30°C and rolling them at 20°C while applying a rolling speed of 50 m / min and a force of 5 kN.

[0162] These lithium metal layers were then subjected to a pressure of 0.5 N / mm. 2The lithium metal laminate was formed by combining the lithium metal layers at a temperature of 60°C and a speed of 0.5 m / min, resulting in a lithium metal laminate containing three lithium metal layers each with a thickness of 18 µm.

[0163] The lithium metal laminate thus formed is rolled between two rolls at 30°C in air (dew point -40°C) while a rolling speed of 2 m / min and a force of 10 kN are applied to form a lithium metal film F1 with a thickness of 18 µm.

[0164] A comparative 18µm thick lithium metal film F, which does not conform to the present invention, was prepared according to the detailed operating conditions below. c .

[0165] A lithium metal layer with a thickness of approximately 18 µm was obtained by extruding lithium ingots at 30°C and rolling them at 20°C while applying a rolling speed of 50 m / min and a force of 5 kN, thus forming a lithium metal film F with a thickness of 18 µm. c .

[0166] Table 1 lists the two types of thin films formed in this way, F1 and F2. c The microstructural characteristics.

[0167]

[0168] Table 1

[0169] As can be seen from Table 1, compared with thin film F c It has a smaller grain area and a smaller average extrapolated grain diameter. More specifically, the thin film F1 according to the invention contains lithium through-grains, whose average extrapolated diameter is greater than that of the comparative thin film F. c The average extrapolated diameter of lithium penetrating the grains is 2.5 times larger. Due to the dynamic recrystallization that occurs in steps i) and ii) of the method, film F1 has the same characteristics as film F. c Different microstructures. This dynamic recrystallization can be observed under an optical microscope.

[0170] Example 2: Manufacturing a battery from a lithium metal film

[0171] A polymer electrolyte was prepared by extrusion and rolling between two silicone-coated PET films at 130°C. The electrolyte comprised 50 wt% of a copolymer of polyvinylidene fluoride and hexafluoropropylene sold by Solvay under the brand name "PVdF-HFP 21512", 48 wt% of polyethylene oxide sold by Sumitomo Seika under the brand name "POE 1L", and 12 wt% of LiTFSI sold by Solvay. A polymer electrolyte membrane with a thickness of approximately 14 µm was obtained after rolling.

[0172] A positive electrode was prepared by extrusion at 80°C, comprising 76 wt% LiFePO4 (LFP) sold by Sumitomo Osaka Cernent, 1 wt% carbon black sold by Akzo Nobel under the brand name "Ketjenblack EC600JD", 5.5 wt% LiTFSI sold by Solvay, and 17.5 wt% POE sold by Sumitomo Seika under the brand name "POE 1L". The resulting mixture was then rolled at 80°C onto an aluminum-coated current collector sold by Armor to form a positive electrode film.

[0173] The first battery is then assembled by sequentially combining the following components:

[0174] - Thin film F prepared in Example 1 c The negative electrode is formed.

[0175] - The polymer electrolyte film prepared as described above, and

[0176] - The positive electrode film prepared as described above.

[0177] Composite at pressure 5.10 3 Under the conditions of Pa, temperature 80°C, and air (dew point -40°C), in a volume of approximately 10 cm³ 3 It is carried out in small batteries (called "pouch batteries").

[0178] Then the first battery was placed at 80°C in "Bitrode" ® "The cycle tester was used to evaluate the electrochemical performance. The first cycle used a charge / discharge system equal to C / 10-D / 10, and subsequent cycles used a charge / discharge system equal to C / 4-D / 2."

[0179] The results obtained are as follows Figure 3 and Figure 4 As shown.

[0180] Figure 3 This shows the changes in relative capacity (in mAh / g) and efficiency (in %) with the number of cycles. The gray curve (corresponding to the arrow) represents the change in capacity, while the black curve (corresponding to the arrow) represents the change in efficiency.

[0181] Internal resistance (Ri, unit: Ohm.cm) 2 The change with the number of iterations is as follows: Figure 4 As shown.

[0182] Figure 3 The results presented indicate that the thin film F cThe efficiency and relative capacity of the battery, acting as the negative electrode, remained stable over approximately 520 cycles. Battery efficiency began to decline around the 400th cycle. Figure 4 Around the 400th cycle, an increase in Ri was observed (an increase of 32%, corresponding to an increase of 0.1% in Ri per cycle).

[0183] Then, the second battery is assembled in exactly the same manner as in Scheme 2 above, and the following components are sequentially combined:

[0184] - The negative electrode is composed of the thin film F1 prepared in Example 1.

[0185] - The polymer electrolyte membrane prepared as described above, and

[0186] - The positive electrode film prepared as described above.

[0187] The performance of the second battery according to the present invention is compared with the performance of the first battery prepared as described above.

[0188] The cycling conditions are the same as those used for the first battery.

[0189] The results obtained are as follows Figure 5 and Figure 6 As shown.

[0190] Figure 5 This shows the changes in relative capacity (in mAh / g) and efficiency (in %) with the number of cycles. The gray curve (corresponding to the arrow) represents the change in capacity, while the black curve (corresponding to the arrow) represents the change in efficiency.

[0191] Figure 6 The internal resistance Ri (unit: Ohm.cm) is shown. 2 (This varies with the number of iterations.)

[0192] Figure 5 The improved cycle performance of the second cell according to the invention compared to the first cell is shown. Specifically, the thin film F1 with a larger grain size exhibits a cycle performance of approximately 770 cycles. The efficiency of the second cell according to the invention begins to decline from the 650th cycle. Figure 6 Around the 600th cycle, an increase in Ri was observed (an increase of 24%, corresponding to an increase of 0.05% in Ri per cycle).

[0193] Therefore, the second battery according to the present invention has better operating performance than the first battery in comparison.

[0194] Then, the third battery is assembled in exactly the same manner as in Example 2 above, and the following components are sequentially combined:

[0195] - The negative electrode is composed of the thin film F1 prepared in Implementation Scheme 1.

[0196] - A gel-like polymer electrolyte comprising 70 wt% plasticizer (propylene carbonate), 15 wt% PVdF, and 15 wt% cationic monopolar conductive polymer (PSTFSI). The electrolyte film thickness is 30 µm.

[0197] - Positive electrode membrane, comprising 62% by weight lithium manganese iron phosphate (LMFP), 2.5% by weight carbon black sold by Akzo Nobel under the brand name "Ketjenblack EC600JD", 30% by weight propylene carbonate, 3.5% by weight PVdF and 2% by weight cationic monopolar conductive polymer (PSTFSI).

[0198] The cycling conditions are the same as those used for the first battery, except for the cycling temperature: 40°C and the charging cut-off voltage is 4.2V.

[0199] The results obtained are as follows Figure 7 and Figure 8 As shown.

[0200] Figure 7 This shows the changes in relative capacity (in mAh / g) and efficiency (in %) with the number of cycles. The gray curve (corresponding to the arrow) represents the change in capacity, while the black curve (corresponding to the arrow) represents the change in efficiency.

[0201] Figure 8 The internal resistance Ri (unit: Ohm.cm) is shown. 2 (This varies with the number of iterations.)

[0202] Figure 7 The improved cycle performance of the third battery according to the invention is comparable to that of the second battery. Specifically, the thin film F1 with a larger grain size allows for approximately 630 cycles at 40°C. The performance of the third battery according to the invention did not show a decrease or degradation throughout the cycling process. Figure 8 Around the 500th cycle, an increase in Ri was observed (an increase of 17%, corresponding to an increase of 0.2% in Ri per cycle).

Claims

1. A metal layer comprising lithium or a lithium alloy, preferably used in lithium metal batteries, said metal layer having a diameter D along the normal direction. N The extended thickness e, along the lateral direction D T The width L of the extension and the rolling direction D L The length of the extension is l, and the direction is D. N D T and D L They are orthogonal to each other, characterized by: * The metal layer contains lithium through grains or lithium alloy through grains. * Each penetrating grain is formed by at least one direction D parallel to the normal. N The grain size d extending in the direction of the direction GN (unit: µm) and by D T and D L At least one grain surface area S on the defined plane G (Unit: mm) 2 Defined by ), such that: * d GN = e (unit: µm), and *S G ≥ 1.5 × π × [(2.9 × e) / 2] 2 ,Selection S G ≥ 3 × π × [(2.9 × e) / 2] 2 .

2. The metal layer according to claim 1, characterized in that, It is self-supporting.

3. The metal layer according to claim 1 or 2, characterized in that, The average extrapolated diameter d of the penetrating grain G (Unit: µm) ≥ 3.5 × e.

4. The metal layer according to any one of the preceding claims, characterized in that, The thickness e is less than or equal to 100µm.

5. The metal layer according to any one of the preceding claims, characterized in that, The through-grain density of the metal layer (unit: grain number / mm) 2 ) < 151230 × (layer thickness, unit: µm) -2 .

6. The metal layer according to any one of the preceding claims, characterized in that, The metal layer comprises at least 90% by weight of lithium through grains or lithium alloy through grains, which constitute at least 90% by weight of the total weight of lithium grains or lithium alloy grains present in the metal layer.

7. The metal layer according to any one of the preceding claims, characterized in that, The lithium or lithium alloy comprises at least 90% by weight of the total weight of the metal layer containing the lithium or lithium alloy.

8. A method for manufacturing a metal layer as defined in any of the preceding claims, characterized in that, It includes at least the following steps: - Step i): Prepare a metal laminate containing at least three metal layers comprising lithium or lithium alloy, each metal layer containing lithium through grains or lithium alloy through grains and having initial thicknesses ei1, ei2, ei3, and - Step ii): Roll the metal laminate to a final thickness ef = e, such that ef ≤ ei1, ef ≤ ei2, and ef ≤ ei3.

9. The method according to claim 8, characterized in that, Step i) includes extruding lithium ingots or lithium alloy ingots i-1) and rolling i-2) to form the at least three lithium- or lithium alloy-containing metal layers, followed by compounding the metal layers i-3), preferably at a pressure of 0.1 N / mm. 2 Up to 1.0 N / mm 2 The operation was carried out at speeds ranging from 0.5 m / min to 50 m / min.

10. The method according to claim 8 or 9, characterized in that, Step ii) is carried out at a speed v of 1 m / min to 70 m / min.

11. The method according to any one of claims 8 to 10, characterized in that, Step ii) is carried out under conditions where the force f is between 5 kN and 35 kN.

12. The method according to any one of claims 8 to 11, characterized in that, The thickness of the metal laminate is 300µm or less.

13. Use of the metal layer as defined in any one of claims 1 to 7 as a negative electrode to improve the cycle performance of a lithium metal battery.

14. A lithium metal battery, comprising: - At least one positive electrode, - At least one negative electrode, and - At least one solid or quasi-solid electrolyte located between the positive and negative electrodes. Its features are, The negative electrode is a metal layer as defined in any one of claims 1 to 7.

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