A lithium metal battery

Abstract

The present invention relates to the technical field of batteries, and particularly to a lithium metal battery. A lithium metal battery of the present invention includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; the positive electrode sheet includes a lithium-rich manganese-based positive electrode material, and the lithium-rich manganese-based positive electrode material includes a matrix material and an antioxidant layer coated on the surface of the matrix material; the matrix material includes xLi2MnO3·(1-x)LiMO2, where M is at least one of Ni, Co and Mn, and 0 < x < 1; the antioxidant layer includes a hindered amine light stabilizer; the electrolyte includes a solvent, and the solvent includes a cyclic ether containing an electron-withdrawing group. The lithium metal battery provided by the present invention improves the antioxidant ability of the battery at high voltages by improving the positive electrode sheet and the electrolyte, and realizes the long-cycle performance of the battery at high voltages.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and more particularly to a lithium metal battery. Background Art

[0002] The lithium-rich manganese-based (LMR) material xLi2MnO3·(1-x)LiMO2 (0 < x < 1, M = Ni, Co, Mn and other transition metals and their combinations) is one of the preferred materials for high specific energy batteries. The LMR material has a high capacity and a higher energy density compared to cathode materials such as LMO, LFP, LCO, NCM, and NCA. The formation of its high capacity is due to the combined action of two mechanisms, namely the redox reaction of transition metals and the redox reaction of oxygen ions.

[0003] However, the LMR material has the following problems: 1) During the cycling process, Mn 3+ migrates into the lithium vacancies, causing the layered structure to transform into a spinel structure, resulting in a continuous decrease in the average discharge voltage, serious energy loss, and a huge challenge to battery management; 2) The low electronic conductivity of Li2MnO3 makes the LMR material have poor rate performance; 3) The low density of the LMR material results in a low volumetric energy density of the material; 4) The LMR material needs to operate at a high voltage (>4.55V) to exhibit a high capacity, but at high voltages, the electrolyte is prone to oxidative decomposition, and at the same time, lattice oxygen is oxidized to O2 and escapes.

[0004] Constructing a stable CEI film at the cathode - electrolyte interface using an electrolyte is an effective strategy to improve cycling stability and safety. The CEI film not only protects the bulk structure from irreversible phase changes caused by electrolyte erosion but also inhibits the catalytic decomposition of the electrolyte caused by the dissolution of transition metal ions. However, the CEI film is attacked by the reactive oxygen released from the lattice surface, leading to the destruction of the interface and the bulk structure. The instability of the CEI film is manifested as spatial and chemical inhomogeneities and an excessive thickness, which usually results in the degradation of the cathode structure and an increase in impedance. Therefore, the electrochemical performance and safety performance decrease sharply.

[0005] Currently, there are mainly two methods to improve the cathode - electrolyte interface. One is to improve the cathode surface, such as using oxide or phosphate coatings, molecular or atomic layer deposition, and using solid-state electrolytes. The main purpose of this method is to establish a physical barrier on the material surface to prevent adverse interactions between the cathode and the electrolyte. However, their impact on improving interface stability is limited because they ignore two key points. One is the key chemical factors, free radicals and singlet oxygen, that cause degradation, and the other is that as the accumulation of cation mixing and the continuous dissolution of transition metals progress, surface phase changes gradually develop into large particles, resulting in the collapse of the layered structure, hindering Li +Furthermore, surface coating strategies often result in capacity loss or conductivity degradation, which cannot meet the requirements of cost-effective production.

[0006] The other is from the perspective of electrolyte. Carbonate electrolytes are more commonly used, but carbonate electrolytes have poor compatibility with metallic lithium and react with lithium to form an organic SEI film of alkyl lithium carbonate (ROCO2Li); and this SEI film cannot withstand the volume expansion of repeated lithium deposition and will continue to thicken, causing the lithium negative electrode to fail rapidly. Compared with carbonate electrolytes, ether-based electrolytes such as 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) produce flat and large lithium particles during the electroplating process, thereby reducing the contact area between the electrolyte and the plated lithium, thereby achieving higher coulombic efficiency (CE). However, the limited oxidative stability of ether-based electrolytes limits their application in high voltage applications.

[0007] In view of this, the present invention is proposed. Summary of the Invention

[0008] The purpose of the present invention is to provide a lithium metal battery, which improves the battery's antioxidant capacity at high voltage by improving the positive electrode sheet and electrolyte, and realizes the battery's long cycle performance at high voltage.

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0010] The present invention provides a lithium metal battery, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte;

[0011] The positive electrode sheet comprises a lithium-rich manganese-based positive electrode material, and the lithium-rich manganese-based positive electrode material comprises a base material and an anti-oxidation layer coated on the surface of the base material;

[0012] The matrix material includes xLi2MnO3·(1-x)LiMO2, wherein M is at least one of Ni, Co and Mn, <x<1;

[0013] The anti-oxidation layer includes a hindered amine light stabilizer;

[0014] The electrolyte includes a solvent, and the solvent includes a cyclic ether containing an electron-withdrawing group.

[0015] Furthermore, the hindered amine light stabilizer includes a piperidine derivative.

[0016] Preferably, the piperidine derivatives include N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-N,N'-dialdehyde hexanediamine, 3-methyl-1-(2-(1-piperidinyl)phenyl)butylamine adipate, N,N'-bis(2,2,6,6-tetramethylpiperidin-4-yl)hexane-1,6-diamine, N1-(3-(piperidin-1-yl)propyl)benzene-1,2-diamine, N1-cyclohexyl-4-(1-piperidinylmethyl)-1,2-phenylenediamine, N,N,N-trimethyl-N-piperidin-4-yl-1,2-ethylenediamine, N-(4-fluorobenzyl)-N-(1 -methyl-piperidin-4-yl)-N'-(4-[(3-hydroxy)-isobutyl]benzyl)carbodiamide, N-(4-fluorobenzyl)-N-(1-methylpiperidin-4-yl)-N'-[4-(2-hydroxy)isobutylbenzyl]carbodiamide, N-(4-fluorobenzyl)-N-(1-methyl-1-oxopiperidin-4-yl)-N'-(4-isobutylbenzyl)carbodiamide and N4-(5-cyclopropyl-1H-pyrazol-3-yl)-N2-[[3-isopropyl-5-isoxazolyl]methyl]-6-(4-methyl-1-piperazinyl)-2,4-pyrimidinediamine.

[0017] Furthermore, the mass ratio of the hindered amine light stabilizer to the base material is (0.1-3): (97-99.9).

[0018] Furthermore, the preparation method of the lithium-rich manganese-based positive electrode material comprises the following steps:

[0019] The hindered amine light stabilizer, the catalyst and the matrix material are mixed to obtain the lithium-rich manganese-based positive electrode material.

[0020] Furthermore, the catalyst includes a compound containing a benzene ring.

[0021] Preferably, the catalyst comprises at least one of 2,5-dihydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5-dihydroxy-1,4-benzenediacetic acid, 2,5-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 3-(2,5-dihydroxyphenyl)acrylic acid, 3-hydroxybenzoic acid, Z-hydroxy-phenylheptanoic acid, 3-hydroxyphenylacetic acid and 2-hydroxybenzenesulfonic acid.

[0022] Furthermore, the mass ratio of the hindered amine light stabilizer to the catalyst is (97-99.9): (0.1-3).

[0023] Furthermore, the cyclic ether containing an electron-withdrawing group includes at least one of 2,2-bis(trifluoromethyl)-1,3-dioxolane, 4-(trifluoromethyl)-1,3-dioxolane and 2-(trifluoromethyl)dioxolane.

[0024] Furthermore, the electrolyte further comprises a lithium salt; the molar ratio of the lithium salt to the solvent is 1:(0.5-3).

[0025] Furthermore, the electrolyte also includes a diluent and an additive.

[0026] Preferably, the molar ratio of the lithium salt to the diluent is 1:(0.5-9).

[0027] Preferably, in the electrolyte, the content of the additive is 0.1 wt% to 2 wt%.

[0028] Furthermore, the lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium metaphosphate and lithium difluorobis(oxalophosphate).

[0029] Preferably, the diluent includes at least one of difluoromethyl 2,2,3,3-tetrafluoropropyl ether, heptafluoropropyl 1,2,2,2-tetrafluoroethyl ether, 2,2,3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ester, heptafluoroane, 1,2-dibromopentafluoropropyl-2,2,3,3-tetrafluoropropyl ether, bis-(1,2,2,2-tetrafluoroethyl) ether, 1,1,2,3,3,3-pentafluoropropyl difluoromethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.

[0030] Preferably, the additive comprises lithium bis(fluorosulfonyl)imide and / or lithium bis(trifluoromethylsulfonyl)imide.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The lithium metal battery of the present invention improves the oxidation resistance of the battery at high voltage by improving the positive electrode sheet and the electrolyte, thereby achieving long-cycle performance of the battery at high voltage.

[0033] For the positive electrode, by using hindered amine light stabilizers to construct an antioxidant layer on the surface of the lithium-rich manganese-based material, it can effectively capture free radicals and reactive oxygen species, stabilize the bulk and surface structures of the material, reduce interfacial side reactions, reduce the release of reactive oxygen, ensure a stable CEI structure, and inhibit irreversible rock salt phase change.

[0034] As for the electrolyte, cyclic ethers containing electron-withdrawing groups are used as the main solvent of the electrolyte, which improves the antioxidant ability, hinders the ring-opening polymerization of cyclic ethers, reduces the solvation ability, enhances the coordination between Li and FSI ions, promotes the formation of a stable SEI layer, and achieves highly reversible Li deposition / stripping. DETAILED DESCRIPTION

[0035] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0036] A lithium metal battery according to an embodiment of the present invention is described in detail below.

[0037] In some embodiments of the present invention, a lithium metal battery is provided, comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte;

[0038] The positive electrode sheet includes a lithium-rich manganese-based positive electrode material, and the lithium-rich manganese-based positive electrode material includes a base material and an anti-oxidation layer coated on the surface of the base material;

[0039] The matrix material includes xLi2MnO3·(1-x)LiMO2, wherein M is at least one of Ni, Co and Mn, 0 <x<1;

[0040] The antioxidant layer includes a hindered amine light stabilizer;

[0041] The electrolyte includes a solvent, and the solvent includes a cyclic ether containing an electron-withdrawing group.

[0042] The lithium metal battery of the present invention improves the oxidation resistance of the battery at high voltage by improving the positive electrode sheet and the electrolyte, thereby achieving long-cycle performance of the battery at high voltage.

[0043] For the positive electrode sheet, the present invention improves the lithium-rich manganese-based positive electrode material in the positive electrode sheet. By using a hindered amine light stabilizer, an anti-oxidation layer is constructed on the surface of the lithium-rich manganese-based (LMR) material to capture the active oxygen species generated by the oxidative decomposition of the electrolyte and escaping from the material lattice during the circulation process, thereby stabilizing the bulk and surface structures of the material, reducing interfacial side reactions, reducing the release of active oxygen, and inhibiting irreversible rock salt phase transitions.

[0044] For the electrolyte, cyclic ethers containing electron-withdrawing groups are used as the main solvent of the electrolyte. By introducing electron-withdrawing groups on the cyclic ether, not only can the ring-opening polymerization of the cyclic ether be effectively hindered and the solvation capacity be reduced, but the coordination between Li and FSI ions can also be enhanced, promoting the formation of a stable SEI layer derived from anions and achieving highly reversible Li deposition / stripping.

[0045] In some embodiments of the present invention, the hindered amine light stabilizer includes a piperidine derivative.

[0046] In some embodiments of the present invention, piperidine derivatives include N, N'-bis (2,2,6,6-tetramethyl-4-piperidinyl) -N, N'-dialdehyde hexanediamine, 3-methyl-1- (2- (1-piperidinyl) phenyl) butylamine adipate, N, N'-bis (2,2,6,6-tetramethylpiperidin-4-yl) hexane-1,6-diamine, N1- (3- (piperidin-1-yl) propyl) benzene-1,2-diamine, N1-cyclohexyl-4- (1-piperidinylmethyl) -1,2-phenylenediamine, N, N, N-trimethyl-N-piperidin-4-yl-1,2-ethylenediamine, N- (4-fluorobenzyl) - At least one of N-(1-methyl-piperidin-4-yl)-N'-(4-[(3-hydroxy)-isobutyl]benzyl)carbodiamide, N-(4-fluorobenzyl)-N-(1-methylpiperidin-4-yl)-N'-[4-(2-hydroxy)isobutylbenzyl]carbodiamide, N-(4-fluorobenzyl)-N-(1-methyl-1-oxopiperidin-4-yl)-N'-(4-isobutylbenzyl)carbodiamide and N4-(5-cyclopropyl-1H-pyrazol-3-yl)-N2-[[3-isopropyl-5-isoxazolyl]methyl]-6-(4-methyl-1-piperazinyl)-2,4-pyrimidinediamine.

[0047] The mechanism of action of hindered amine light stabilizers is as follows: the functional structural unit tetramethylpiperidine (TMP) in hindered amine light stabilizers is excited by photoelectrons and oxidized into nitroxide free radicals (TMPO), which can effectively capture the free radical R· in the polymer degradation chain reaction to generate TMPO·R, and then scavenge the peroxide free radical ROO· to ​​generate the inert ROOR.

[0048] A piperidine derivative is used to form an antioxidant layer on the surface of the substrate. This layer stabilizes the bulk and surface structure of the material by scavenging free radicals and singlet oxygen, minimizing interfacial side reactions, reducing the release of reactive oxygen species, and inhibiting the irreversible rock-salt phase transition. The creation of a stable surface and the elimination of reactive oxygen species also result in reduced gas release and improved thermal performance. More importantly, the construction of a chemical barrier on the surface not only effectively improves the structural stability determined by the interface but also provides a solution to thermal runaway caused by oxygen release.

[0049] Constructing a stable surface is key to addressing the harmful crosstalk effect. The antioxidant layer attached to the surface of the LMR material particles exhibits strong chemical stability by resisting attack by free radicals and singlet oxygen. This ensures a stable CEI structure during long-term cycling, which not only mitigates the H2 to H3 phase transition in the bulk phase but also suppresses the irreversible salt rock phase transition and the dissolution of transition metals on the surface.

[0050] In some embodiments of the present invention, the mass ratio of the hindered amine light stabilizer to the matrix material is (0.1-3): (97-99.9); typically but not limitatively, the mass ratio of the hindered amine light stabilizer to the matrix material can be 0.1:99.9, 0.5:99.5, 1:98, 1.5:98.5, 2:98, 2.5:97.5, 3:97 or a range of any two thereof.

[0051] In some embodiments of the present invention, a method for preparing a lithium-rich manganese-based positive electrode material comprises the following steps:

[0052] After the hindered amine light stabilizer, the catalyst and the matrix material are mixed, a lithium-rich manganese-based positive electrode material is obtained.

[0053] In some embodiments of the present invention, the catalyst comprises a compound containing a benzene ring.

[0054] In some embodiments of the present invention, the catalyst includes at least one of 2,5-dihydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5-dihydroxy-1,4-benzenediacetic acid, 2,5-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 3-(2,5-dihydroxyphenyl)acrylic acid, 3-hydroxybenzoic acid, Z-hydroxy-phenylheptanoic acid, 3-hydroxyphenylacetic acid and 2-hydroxybenzenesulfonic acid.

[0055] In some embodiments of the present invention, the mass ratio of the hindered amine light stabilizer to the catalyst is (97-99.9): (0.1-3); typically but not limitatively, for example, the mass ratio of the hindered amine light stabilizer to the catalyst can be 97:3, 97.5:2.5, 98:2, 98.5:1.5, 99:1, 99.5:0.5, 99.9:0.1 or a range of any two thereof.

[0056] By adding a catalyst, the hindered amine light stabilizer can be better attached to the surface of the base material.

[0057] In some embodiments of the present invention, a method for preparing a lithium-rich manganese-based positive electrode material comprises the following steps:

[0058] The hindered amine light stabilizer, catalyst and organic solvent are stirred at 30-45° C. for 5-16 hours, then cooled to room temperature, and the matrix material is added and fully stirred for 8-36 hours. After stirring evenly, the lithium-rich manganese-based positive electrode material is obtained after solid-liquid separation and drying.

[0059] In some embodiments of the present invention, in the method for preparing the lithium-rich manganese-based positive electrode material, the organic solvent includes but is not limited to methyl pyrrolidone (NMP).

[0060] In some embodiments of the present invention, the positive electrode sheet further includes a conductive agent and a binder.

[0061] In some embodiments of the present invention, the mass ratio of the lithium-rich manganese-based positive electrode material, the conductive agent and the binder is (94-98): (1.5-4): (0.5-1.5).

[0062] In some embodiments of the present invention, the conductive agent includes but is not limited to carbon nanotubes.

[0063] In some embodiments of the present invention, the binder includes, but is not limited to, at least one of polyvinylidene fluoride (PVDF), vinylidene fluoride, polytetrafluoroethylene, and poly(ethylene-chlorotrifluoroethylene).

[0064] In some embodiments of the present invention, a method for preparing a positive electrode sheet comprises the following steps:

[0065] Mixing the lithium-rich manganese-based positive electrode material and the conductive agent to obtain a mixed material;

[0066] Mixing the binder and the organic solvent to obtain a glue solution;

[0067] After the glue solution and the mixed material are evenly mixed, the viscosity and solid content are adjusted to obtain a positive electrode slurry;

[0068] The positive electrode slurry is coated on aluminum foil, and the positive electrode sheet is obtained after baking and die-cutting.

[0069] In some embodiments of the present invention, in the method for preparing the positive electrode sheet, the organic solvent includes but is not limited to methyl pyrrolidone (NMP).

[0070] In some embodiments of the present invention, the cyclic ether containing an electron-withdrawing group includes at least one of 2,2-bis(trifluoromethyl)-1,3-dioxolane, 4-(trifluoromethyl)-1,3-dioxolane, and 2-(trifluoromethyl)dioxolane.

[0071] The introduction of fluorinated electron-withdrawing groups into cyclic ethers changes the structure and electronic properties of the cyclic ethers, improves their antioxidant capacity, inhibits their ring opening, and thus affects the electrochemical window of the electrolyte; the directional functionalization of the electron-withdrawing properties of the electron-withdrawing groups reduces the electron density of the -O- atoms, resulting in a weakening of the solvation ability and promoting the coordination between Li and FSI anions.

[0072] In some embodiments of the present invention, the electrolyte further comprises a lithium salt; the molar ratio of the lithium salt to the solvent is 1:(0.5-3); typically but not limitatively, for example, the molar ratio of the lithium salt to the solvent can be 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3 or a range of any two thereof.

[0073] In some embodiments of the present invention, the electrolyte further includes a diluent and an additive.

[0074] In some embodiments of the present invention, the molar ratio of the lithium salt to the diluent is 1:(0.5-9); typically but not limiting, for example, the molar ratio of the lithium salt to the diluent can be 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or a range consisting of any two thereof.

[0075] In some embodiments of the present invention, the content of the additive in the electrolyte is 0.1wt% to 2wt%; typically but not limitatively, for example, the content of the additive in the electrolyte can be 0.1wt%, 0.3wt%, 0.5wt%, 0.8wt%, 1wt%, 1.3wt%, 1.5wt%, 1.7wt%, 2wt% or a range of any two thereof.

[0076] In some embodiments of the present invention, the lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium metaphosphate, and lithium difluorobisoxalatophosphate.

[0077] In some embodiments of the present invention, the diluent includes at least one of difluoromethyl 2,2,3,3-tetrafluoropropyl ether, heptafluoropropyl 1,2,2,2-tetrafluoroethyl ether, 2,2,3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ester, heptafluoroane, 1,2-dibromopentafluoropropyl-2,2,3,3-tetrafluoropropyl ether, bis-(1,2,2,2-tetrafluoroethyl) ether, 1,1,2,3,3,3-pentafluoropropyldifluoromethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.

[0078] In some embodiments of the present invention, the additive includes lithium bis(fluorosulfonyl)imide and / or lithium bis(trifluoromethylsulfonyl)imide.

[0079] In some embodiments of the present invention, a method for preparing an electrolyte includes the following steps:

[0080] After mixing all the raw materials, an electrolyte is obtained.

[0081] In some embodiments of the present invention, the negative electrode sheet includes a copper-lithium composite tape.

[0082] In some embodiments of the present invention, a method for preparing a lithium metal battery is further provided, including the following steps:

[0083] After the positive electrode sheet, the separator, and the copper-lithium composite tape are laminated, they are successively subjected to encapsulation, electrolyte injection, volume determination, formation, and degassing to obtain a lithium metal battery.

[0084] Example 1

[0085] The method for preparing the lithium metal battery provided in this example includes the following steps:

[0086] After the positive electrode sheet, the uncoated PE separator, and the copper-lithium composite tape are laminated, a lithium metal battery with two positive electrodes and three negative electrodes is fabricated, with a capacity of 1200 mAh. Then, the electrolyte is injected to complete the battery fabrication.

[0087] Among them, the method for preparing the positive electrode sheet includes the following steps:

[0088] N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)-N,N'-dialdehyde hexanediamine and 2,5-dihydroxyterephthalic acid with a molar ratio of 1:1 are added to NMP. After stirring at 40 °C for 10 h, the temperature is lowered to room temperature, and a matrix material (xLi2MnO3·(1-x)LiMO2, M is at least one of Ni, Co, and Mn, 0 < x < 1) is added. The mass ratio of N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)-N,N'-dialdehyde hexanediamine to the matrix material is 0.5:99.5. After充分搅拌12h后,经离心、NMP清洗、真空干燥后得到富锂锰基正极材料;

[0089] The lithium-rich manganese-based positive electrode material and single-walled carbon nanotubes (SWCNTs) are mixed evenly to obtain a mixed material;

[0090] PVDF and NMP are mixed evenly to obtain a glue solution;

[0091] The glue solution and the mixed material are mixed evenly, and then the viscosity and solid content are adjusted to obtain a positive electrode paste;

[0092] The positive electrode paste is coated on an aluminum foil, and after baking and die-cutting, a positive electrode sheet is obtained; in the positive electrode sheet, the mass ratio of the lithium-rich manganese-based positive electrode material, single-walled carbon nanotubes, and PVDF is 97.8:1.6:0.6. It should be noted that there is an unclear expression "充分搅拌12h后,经离心、NMP清洗、真空干燥后得到富锂锰基正极材料;" in the original text which may need to be further clarified for a more accurate translation. The above translation is based on the existing text as much as possible.

[0093] The method for preparing a negative electrode sheet comprises the following steps:

[0094] Lithium is coated on both sides of a copper foil with a thickness of 6 μm (the thickness of the lithium is 20 μm), and then the negative electrode sheet is obtained after trimming and cutting.

[0095] The preparation method of the electrolyte comprises the following steps:

[0096] Lithium hexafluorophosphate, 2-(trifluoromethyl)dioxolane and 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether are mixed in a molar ratio of 1:1.2:3 to obtain a mixed solution, and bisfluorosulfonyl imide lithium salt is added to the mixed solution. The mass ratio of the mixed solution to the bisfluorosulfonyl imide lithium salt is 100:0.5 to obtain an electrolyte.

[0097] Example 2

[0098] The preparation method of the lithium metal battery provided in this embodiment refers to Example 1, with the only difference being that, in the preparation method of the positive electrode sheet, the mass ratio of N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-N,N'-dialdehyde hexamethylenediamine to the matrix material is 0.1:99.9.

[0099] Example 3

[0100] The preparation method of the lithium metal battery provided in this embodiment refers to Example 1, with the only difference being that, in the preparation method of the positive electrode sheet, the mass ratio of N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-N,N'-dialdehyde hexamethylenediamine to the matrix material is 3:97.

[0101] Example 4

[0102] The preparation method of the lithium metal battery provided in this embodiment refers to Example 1, with the only difference being that in the preparation method of the electrolyte, 2-(trifluoromethyl)dioxolane is replaced by 2,2-bis(trifluoromethyl)-1,3-dioxolane.

[0103] Example 5

[0104] The preparation method of the lithium metal battery provided in this embodiment refers to Example 1, except that the preparation method of the electrolyte includes the following steps: lithium hexafluorophosphate, 2-(trifluoromethyl)dioxolane and 1,2-dibromopentafluoropropyl-2,2,3,3-tetrafluoropropyl ether are mixed in a molar ratio of 1:2:5 to obtain a mixed solution, and lithium bis(trifluoromethylsulfonyl)imide is added to the above mixed solution. The mass ratio of the mixed solution to lithium bis(trifluoromethylsulfonyl)imide is 100:0.6 to obtain an electrolyte.

[0105] Comparative Example 1

[0106] The preparation method of the lithium metal battery provided in this comparative example refers to Example 1, with the only difference being that, in the preparation method of the positive electrode sheet, the lithium-rich manganese-based positive electrode material is used as the base material.

[0107] Comparative Example 2

[0108] The preparation method of the lithium metal battery provided in this comparative example refers to Example 1, with the only difference being that in the preparation method of the electrolyte, 2-(trifluoromethyl)dioxolane is replaced by 1,3-epoxypentane (DOL).

[0109] Test Example 1

[0110] The electrochemical properties of the lithium metal batteries prepared in Examples 1 to 5 and Comparative Examples 1 to 2 were tested, and the results are shown in Table 1.

[0111] Normal temperature formation test: Charge at 25°C at a constant current of 0.1C to 4.3V, charge at a constant voltage of 4.3V to a cutoff current of 0.05C, and then discharge the battery at a constant current of 0.1C to 3.0V.

[0112] Room temperature cycling test: At 25°C, charge at a constant current of 0.3C to 4.3V, then charge at a constant voltage of 4.3V to a cutoff current of 0.05C. Then, discharge at a constant current of 0.5C to 3.0V. The discharge capacity is recorded as C1. Repeat the charge and discharge steps for 300 cycles. The discharge capacity in the Nth cycle, CN, is obtained. Capacity retention rate = CN / C1 × 100%. Average coulombic efficiency for the first N cycles = SUM (coulombic efficiency of each of the first N cycles) / N.

[0113] If the capacity retention rate of the cycle test is less than 80% and the coulombic efficiency is less than 98%, the battery test is stopped.

[0114] Table 1

[0115]

[0116] As can be seen from Table 1, the lithium metal battery of the present invention has excellent long-cycle performance at high voltage by improving the positive electrode sheet and the electrolyte.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium metal battery, characterized in that Including positive electrode sheet, negative electrode sheet, separator and electrolyte; The positive electrode sheet comprises a lithium-rich manganese-based positive electrode material, and the lithium-rich manganese-based positive electrode material comprises a base material and an anti-oxidation layer coated on the surface of the base material; The matrix material includes xLi2MnO3·(1-x)LiMO2, wherein M is at least one of Ni, Co and Mn, <x<1; The anti-oxidation layer includes a hindered amine light stabilizer; The electrolyte includes a solvent, and the solvent is a cyclic ether containing an electron-withdrawing group; The mass ratio of the hindered amine light stabilizer to the matrix material is (0.1-3): (97-99.9); The cyclic ether containing an electron-withdrawing group includes at least one of 2,2-bis(trifluoromethyl)-1,3-dioxolane, 4-(trifluoromethyl)-1,3-dioxolane and 2-(trifluoromethyl)dioxolane.

2. The lithium metal battery according to claim 1, characterized in that The hindered amine light stabilizer includes piperidine derivatives.

3. The lithium metal battery according to claim 2, characterized in that The piperidine derivatives include N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-N,N'-dialdehyde hexanediamine, 3-methyl-1-(2-(1-piperidinyl)phenyl)butylamine adipate, N,N'-bis(2,2,6,6-tetramethylpiperidin-4-yl)hexane-1,6-diamine, N1-(3-(piperidin-1-yl)propyl)benzene-1,2-diamine, N1-cyclohexyl-4-(1-piperidinylmethyl)-1,2-phenylenediamine, N,N,N-trimethyl-N-piperidin-4-yl-1,2-ethylenediamine, N-(4-fluorobenzyl)-N-(1-methyl)- At least one of N-(5-cyclopropyl-1H-pyrazol-3-yl)-N2-[[3-isopropyl-5-isoxazolyl]methyl]-6-(4-methyl-1-piperazinyl)-2,4-pyrimidinediamine and N-(4-fluorobenzyl)-N-(1-methylpiperidin-4-yl)-N'-[4-(2-hydroxy)isobutylbenzyl]carbodiamide, N-(4-fluorobenzyl)-N-(1-methyl-1-oxopiperidin-4-yl)-N'-(4-isobutylbenzyl)carbodiamide and N4-(5-cyclopropyl-1H-pyrazol-3-yl)-N2-[[3-isopropyl-5-isoxazolyl]methyl]-6-(4-methyl-1-piperazinyl)-2,4-pyrimidinediamine.

4. The lithium metal battery according to claim 1, characterized in that The method for preparing the lithium-rich manganese-based positive electrode material comprises the following steps: The hindered amine light stabilizer, the catalyst and the matrix material are mixed to obtain the lithium-rich manganese-based positive electrode material.

5. The lithium metal battery according to claim 4, characterized in that The catalyst includes a compound containing a benzene ring.

6. The lithium metal battery according to claim 5, characterized in that The catalyst includes one or more combinations of 2,5-dihydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5-dihydroxy-1,4-benzenediacetic acid, 2,5-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 3-(2,5-dihydroxyphenyl)acrylic acid, 3-hydroxybenzoic acid, Z-hydroxy-phenylheptanoic acid, 3-hydroxyphenylacetic acid, and 2-hydroxybenzenesulfonic acid.

7. The lithium metal battery according to claim 4, characterized in that The mass ratio of the hindered amine light stabilizer to the catalyst is (97-99.9): (0.1-3).

8. The lithium metal battery according to claim 1, characterized in that The electrolyte further includes a lithium salt; the molar ratio of the lithium salt to the solvent is 1:(0.5-3).

9. The lithium metal battery according to claim 8, characterized in that The electrolyte also includes a diluent and additives.

10. The lithium metal battery according to claim 9, characterized in that The molar ratio of the lithium salt to the diluent is 1:(0.5-9).

11. The lithium metal battery according to claim 9, characterized in that In the electrolyte, the content of the additive is 0.1 wt% to 2 wt%.

12. The lithium metal battery according to claim 9, characterized in that The lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium metaphosphate and lithium difluorobisoxalatophosphate.

13. The lithium metal battery according to claim 9, characterized in that The diluent includes at least one of difluoromethyl 2,2,3,3-tetrafluoropropyl ether, heptafluoropropyl 1,2,2,2-tetrafluoroethyl ether, 2,2,3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ester, heptafluoroane, 1,2-dibromopentafluoropropyl-2,2,3,3-tetrafluoropropyl ether, bis-(1,2,2,2-tetrafluoroethyl) ether, 1,1,2,3,3,3-pentafluoropropyl difluoromethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.

14. The lithium metal battery according to claim 9, characterized in that The additive includes lithium bis(fluorosulfonyl)imide and / or lithium bis(trifluoromethylsulfonyl)imide.

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