Electrolyte, battery, and energy storage device

Abstract

Provided are an electrolyte, a battery, and an energy storage device, for use in solving the problem in existing batteries of poor high-voltage cycling stability and safety of electrolytes. The electrolyte comprises a lithium salt, a solvent, and additives. The additives include a first additive and a second additive. The first additive is one or more of compounds as shown in formula I, and the second additive is one or more of compounds as shown in formula II. R1-R6 are each independently selected from F, a C6-C26 fluoro-substituted phenoxy group, and a C1-C20 fluoro-substituted alkoxy group, R7-R12 are each independently selected from halogen, a C1-C20 fluoro-substituted alkyl group, a cyano group, and an amino group, at least one of R7-R12 is selected from the cyano group, and the halogen includes one or more of fluorine, chlorine, bromine and iodine.

Description

Electrolyte, battery and energy storage device

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on March 13, 2024, with application number 202410286270.7 and invention name “An electrolyte, battery and energy storage device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the field of electrolyte technology, and specifically relates to an electrolyte, a battery, and an energy storage device. Background Art

[0003] With the development of electric vehicles, the demand for battery energy density has increased significantly. The narrow voltage window of electrolytes has become a key limitation to the further development of next-generation high-energy-density batteries. Therefore, the development of new high-voltage and safe electrolyte systems to increase energy density has become a research focus for high-energy-density lithium batteries.

[0004] To develop a safe electrolyte system, the primary method for improving the safety of secondary battery electrolytes is to add flame retardant additives to conventional electrolytes. While a wide variety of flame retardant additives have been reported, such as phosphate compounds and halogenated compounds, these additives have yet to fully meet the requirements for use. These additives can exhibit high viscosity, low conductivity, and poor compatibility with electrode materials, or they can be added in high amounts, affecting SEI film stability and resulting in poor cycling performance. Therefore, further development of novel multi-element composite flame-retardant electrolytes is crucial for safe battery applications. Summary of the Invention

[0005] To address the problems of poor high-voltage cycling stability and safety of electrolytes in existing batteries, the present application provides an electrolyte, a battery, and an energy storage device.

[0006] The technical solutions adopted by this application to solve the above technical problems are as follows:

[0007] In one aspect, the present application provides an electrolyte comprising a lithium salt, a solvent, and an additive, wherein the additive comprises a first additive and a second additive, wherein the first additive is one or more compounds represented by formula I, and the second additive is one or more compounds represented by formula II;

[0008] wherein said R1-R6 are each independently selected from F, C6-C26 fluorine-substituted phenoxy, C1-C20 fluorine-substituted alkoxy, said R7-R 12 are independently selected from halogen, C1-C20 fluorine-substituted alkyl, cyano, amino, and said R7-R 12At least one of the halogens is selected from cyano, and the halogen includes one or more of fluorine, chlorine, bromine and iodine.

[0009] Optionally, the sum of the added amounts of the first additive and the second additive is 0.5% to 15% of the mass of the electrolyte.

[0010] Optionally, the mass ratio of the first additive to the second additive is (0.1-50):(50-0.1).

[0011] Optionally, the first additive includes one or more of hexaethoxyfluorophosphazene (HEPN), hexamethoxyphosphazene (HMPN), bis(2(2-methoxyethoxy)ethoxy)phosphazene (MEEP), ethoxypentafluorocyclotriphosphazene (PFPN), hexafluorocyclotriphosphazene (HFPN), phenoxypentafluorocyclotriphosphazene (FPPN), trifluoroethoxypentafluorocyclotriphosphazene (TFPN), 4-methoxy-phenoxypentafluorocyclotriphosphazene (4-MPPFPP), hexaphenoxycyclotriphosphazene (HPCTP), and hexa(2,2,2-trifluoroethoxy)cyclotriphosphazene;

[0012] The second additive includes p-fluorobenzonitrile, o-fluorobenzonitrile, 3,4-difluorobenzonitrile (34FBN), 3,5-difluorobenzonitrile (35FBN), 2,3-difluorobenzonitrile (23FBN), 2,4,6-trifluorobenzonitrile (246TFBN), 3,4,5-trifluorobenzonitrile (345TFBN), 2,3,4,5,6-pentafluorobenzonitrile (5FBN), 4-bromo-2-fluorobenzonitrile (4B2FBN), 2,4-difluorobenzonitrile (24 One or more of 4-(trifluoromethyl)benzonitrile, 4-bromo-2,3,5,6-tetrafluorobenzonitrile and 4-amino-2-(trifluoromethyl)benzonitrile.

[0013] Optionally, the solvent includes an organic solvent, and the organic solvent includes one or more of an amide solvent, a silane solvent, a sulfone solvent, a nitrile solvent, a carbonate solvent, an ether solvent, and a phosphate solvent.

[0014] Optionally, the amide solvent includes one or more of 2,2,2-trifluoro-N,N-dimethylacetamide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-dimethylpropionamide, formamide, N,N-diethylacetamide, N,N-dimethylisobutyramide, N,N-diethylacetoacetamide, N-methyl-N-vinylacetamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N,N-dimethylfluorosulfonamide and N,N-dimethyltrifluoromethanesulfonamide;

[0015] The silane solvent includes one or more of vinyltrimethoxysilane, vinyltriethoxysilane, tris(trimethylsilyl)borate, dimethoxydimethylsilane, diethoxydimethylsilane, triethoxymethylsilane, methoxytrimethylsilane and 1,1,3,3-tetramethyldisiloxane;

[0016] The sulfone solvent includes one or more of dimethyl sulfoxide, tetramethylene sulfone, ethyl vinyl sulfone, methyl vinyl sulfone and allyl methyl sulfone;

[0017] The nitrile solvent includes one or more of succinonitrile, 1,3,6-hexanetrinitrile, acetonitrile, glutaronitrile, adiponitrile, butyronitrile, 2-methylglutaronitrile, fluoroacetonitrile, p-fluorophenylacetonitrile, o-fluorobenzonitrile, 3-(trifluoromethyl)phenylacetonitrile, 3,5-bis(trifluoromethyl)phenylacetonitrile, 2,3,4,5,6-pentafluorobenzonitrile, and 3,5-bis(trifluoromethyl)phenylacetonitrile;

[0018] The carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, difluoroethylene carbonate, trifluoropropylene carbonate, trifluoroethyl methyl carbonate and 2,2,2-trifluoroethyl ethyl carbonate;

[0019] The ether solvent includes one or more of 2-dimethoxyethane, ethylene glycol dimethyl ether, dimethoxydimethyl ether, diethylene glycol dimethyl ether, 1,3-dioxolane, triethylene glycol monoethyl ether, tetrahydrofuran and 2-methyl-tetrahydrofuran;

[0020] The phosphate ester solvent includes one or more of trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, 4-isopropylphenyl diphenyl phosphate, diphenyl octyl phosphate, trioctyl phosphate and dimethyl methylphosphonate.

[0021] Optionally, the lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bisfluorosulfonylimide, lithium trifluoromethylsulfonyl-perfluorobutylsulfonylimide, lithium fluorosulfonyl-perfluorobutylsulfonylimide, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium difluorophosphate and lithium nitrate.

[0022] On the other hand, the present application provides a battery comprising a positive electrode, a negative electrode, a separator and the electrolyte as described in any one of the above.

[0023] Optionally, the diaphragm includes one or more of polypropylene, polyethylene, PP / PE / PP composite film, polyvinylidene fluoride, polyacrylonitrile, ceramic diaphragm, ceramic polyamide, aramid and non-woven fabric;

[0024] The positive electrode comprises one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, ternary material, lithium-rich manganese base, lithium nickel manganese oxide, and lithium vanadium phosphate;

[0025] The negative electrode includes one or more of a graphite negative electrode, a silicon-oxygen negative electrode, a silicon-carbon negative electrode, a silicon negative electrode, a tin negative electrode, a tin oxide negative electrode, a tin alloy negative electrode, a lithium metal negative electrode, a lithium alloy negative electrode and a lithium-free negative electrode.

[0026] On the other hand, the present application provides a battery comprising a positive electrode, a negative electrode, a separator and a gel electrolyte, wherein the gel electrolyte comprises the electrolyte described in any one of the above items, and the mass of the electrolyte is 0.5% to 50% of the mass of the gel electrolyte.

[0027] On the other hand, the present application provides a battery comprising a positive electrode, a negative electrode, a separator, a solid electrolyte and an electrolyte as described above, wherein the mass of the electrolyte is 0.5% to 50% of the mass of the solid electrolyte.

[0028] Optionally, the solid electrolyte includes an inorganic solid electrolyte, a polymer solid electrolyte and a composite solid electrolyte;

[0029] The inorganic solid electrolyte includes one or more of an oxide solid electrolyte, a sulfide solid electrolyte, and a halide solid electrolyte;

[0030] The polymer solid electrolyte includes one or more of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate;

[0031] The composite solid electrolyte includes an inorganic filler and a polymer matrix, wherein the inorganic filler includes one or more of an oxide solid electrolyte, a sulfide solid electrolyte, and a halide solid electrolyte; and the polymer matrix includes one or more of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0032] Optionally, the oxide solid electrolyte includes one or more of LLZO, LLTO, LATP, and LAGP; the sulfide solid electrolyte includes one or more of LGPS, LPS, and LPSCl; and the halide solid electrolyte includes one or more of Li3YCl6, Li3ScCl6, and Li3YBr6.

[0033] On the other hand, the present application provides an energy storage device, comprising a battery as described in any one of the above items.

[0034] In this application, by adding a first additive and a second additive with high-efficiency flame retardant properties to the electrolyte, the high-voltage oxidation stability and anti-overcharge performance of the electrolyte are synergistically optimized, while the flame retardancy of the electrolyte is improved, and the safety of the battery is improved in situ through the electrolyte system. The first additive belongs to the phosphazene class of compounds. Phosphazene compounds not only have high flame retardant efficiency, but also contain a large number of electron-withdrawing F atoms and electron-donating -P=N- groups in the molecules. They can interact with other solvents containing lone pairs of electrons or electron-deficient atoms, thereby changing the Li + The solvated structure is first defluorinated on the negative electrode surface to form a LiF-rich SEI film. In addition, the generated alkoxyphosphazene migrates to the positive electrode and undergoes an oxidation reaction (high HOMO energy level -7.44eV) to form a uniform and dense interface layer (CEI) rich in P and N, which inhibits side reactions and structural damage to the high-voltage positive electrode, and effectively inhibits the decomposition of the electrolyte. The second additive belongs to the fluorobenzonitrile compound. The cyano group contained in the fluorobenzonitrile compound can generate specifically adsorbed nitriles or nitrile derivatives on the positive electrode surface. In addition, the cyano group can complex with the oxidized metal ions on the positive electrode surface, reducing the occurrence of side reactions such as electrolyte decomposition under high voltage, and can also generate a LiF-rich SEI film on the negative electrode surface. The first additive and the second additive act synergistically on the positive and negative electrodes, which can effectively improve the high-voltage cycle stability and safety of the battery, while improving the anti-overcharge performance of the electrolyte. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects solved by this application more clearly understood, this application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0036] One embodiment of the present application provides an electrolyte, including a lithium salt, a solvent, and an additive, wherein the additive includes a first additive and a second additive, the first additive being one or more of the compounds shown in Formula I, and the second additive being one or more of the compounds shown in Formula II.

[0037] wherein said R1-R6 are each independently selected from F, C6-C26 fluorine-substituted phenoxy, C1-C20 fluorine-substituted alkoxy, said R7-R 12 are independently selected from halogen, C1-C20 fluorine-substituted alkyl, cyano, amino, and said R7-R 12 At least one of the halogens is selected from cyano, and the halogen includes one or more of fluorine, chlorine, bromine and iodine.

[0038] In this application, by adding a first additive and a second additive with high-efficiency flame retardant properties to the electrolyte, the high-voltage oxidation stability and anti-overcharge performance of the electrolyte are synergistically optimized, while the flame retardancy of the electrolyte is improved, and the safety of the battery is improved in situ through the electrolyte system. The first additive belongs to the phosphazene class of compounds. Phosphazene compounds not only have high flame retardant efficiency, but also contain a large number of electron-withdrawing F atoms and electron-donating -P=N- groups in the molecules. They can interact with other solvents containing lone pairs of electrons or electron-deficient atoms, thereby changing the Li + The solvated structure is first defluorinated on the negative electrode surface to form a LiF-rich SEI film. In addition, the generated alkoxyphosphazene migrates to the positive electrode and undergoes an oxidation reaction (high HOMO energy level -7.44eV) to form a uniform and dense interface layer (CEI) rich in P and N, which inhibits side reactions and structural damage to the high-voltage positive electrode, and effectively inhibits the decomposition of the electrolyte. The second additive belongs to the fluorobenzonitrile compound. The cyano group contained in the fluorobenzonitrile compound can generate specifically adsorbed nitriles or nitrile derivatives on the positive electrode surface. In addition, the cyano group can complex with the oxidized metal ions on the positive electrode surface, reducing the occurrence of side reactions such as electrolyte decomposition under high voltage, and can also generate a LiF-rich SEI film on the negative electrode surface. The first additive and the second additive act synergistically on the positive and negative electrodes, which can effectively improve the high-voltage cycle stability and safety of the battery, while improving the anti-overcharge performance of the electrolyte.

[0039] Furthermore, the concentration of the lithium salt in the electrolyte is 0.5M-1.5M, specifically, the concentration of the lithium salt is 0.5M, 1M, 1.2M, and 1.5M.

[0040] In one embodiment, the sum of the added amounts of the first additive and the second additive is 0.5% to 15% of the mass of the electrolyte.

[0041] In a preferred embodiment, the sum of the added amounts of the first additive and the second additive is 5% to 10% of the mass of the electrolyte.

[0042] In one embodiment, the mass ratio of the first additive to the second additive is (0.1-50):(50-0.1). Specifically, the mass ratio of the first additive to the second additive can be 1:1, 2:1, 3:1, 4:1, 5:1, 10:1, 15:1 or 20:1.

[0043] In a preferred embodiment, the mass ratio of the first additive to the second additive is (1-20):(1-10).

[0044] In some embodiments, the first additive includes one or more of hexaethoxyfluorophosphazene (HEPN), hexamethoxyphosphazene (HMPN), bis(2(2-methoxyethoxy)ethoxy)phosphazene (MEEP), ethoxypentafluorocyclotriphosphazene (PFPN), hexafluorocyclotriphosphazene (HFPN), phenoxypentafluorocyclotriphosphazene (FPPN), trifluoroethoxypentafluorocyclotriphosphazene (TFPN), 4-methoxy-phenoxypentafluorocyclotriphosphazene (4-MPPFPP), hexaphenoxycyclotriphosphazene (HPCTP), hexa(2,2,2-trifluoroethoxy)cyclotriphosphazene;

[0045] The second additive includes p-fluorobenzonitrile, o-fluorobenzonitrile, 3,4-difluorobenzonitrile (34FBN), 3,5-difluorobenzonitrile (35FBN), 2,3-difluorobenzonitrile (23FBN), 2,4,6-trifluorobenzonitrile (246TFBN), 3,4,5-trifluorobenzonitrile (345TFBN), 2,3,4,5,6-pentafluorobenzonitrile (5FBN), 4-bromo-2-fluorobenzonitrile (4B2FBN), 2,4-difluorobenzonitrile (24 One or more of 4-(trifluoromethyl)benzonitrile, 4-bromo-2,3,5,6-tetrafluorobenzonitrile and 4-amino-2-(trifluoromethyl)benzonitrile.

[0046] It should be noted that the above compounds are only preferred compounds of the present application and do not represent limitations on the present application.

[0047] In some embodiments, the solvent includes an organic solvent, and the organic solvent includes one or more of an amide solvent, a silane solvent, a sulfone solvent, a nitrile solvent, a carbonate solvent, an ether solvent, and a phosphate solvent. By selecting an amide solvent, a silane solvent, a sulfone solvent, a nitrile solvent, a carbonate solvent, an ether solvent, or a phosphate solvent to adapt to different high-voltage positive electrodes, the wettability of the battery electrode is improved, the cycle stability of the battery is improved, and a high-voltage foundation is provided for the battery. Different solvent types are matched with different addition ratios of the first additive and the second additive to ensure the excellent electrochemical performance and safety of the battery.

[0048] In some embodiments, the amide solvent includes one or more of 2,2,2-trifluoro-N,N-dimethylacetamide (FDMA), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), N,N-diethylformamide (DEFA), N,N-dimethylpropionamide (DMA), formamide (FA), N,N-diethylacetamide (DEAC), N,N-dimethylisobutyramide (DMSA), N,N-diethylacetoacetamide (DEAC), N-methyl-N-vinylacetamide (MVAC), N,N-dimethylacrylamide (DMAA), N,N-diethylacrylamide (DEAA), N,N-dimethylfluorosulfonamide (DMFSA), and N,N-dimethyltrifluoromethanesulfonamide (DMTMSA).

[0049] The silane solvent includes one or more of vinyltrimethoxysilane (VTMS), vinyltriethoxysilane (VTES), tris(trimethylsilyl)borate (TMSB), dimethoxydimethylsilane (DMDMS), diethoxydimethylsilane (DEDMS), triethoxymethylsilane (TEMS), methoxytrimethylsilane (MTMS), and 1,1,3,3-tetramethyldisiloxane (DHTMS).

[0050] The sulfone solvent includes one or more of dimethyl sulfoxide (DMSO), tetramethylene sulfone (SUL), ethyl vinyl sulfone (EVS), methyl vinyl sulfone (MVS), and allyl methyl sulfone (AMS).

[0051] The nitrile solvent includes one or more of succinonitrile (SN), 1,3,6-hexanetricarbonitrile (HTCN), acetonitrile (AN), glutaronitrile (GLN), adiponitrile (ADN), butyronitrile (BN), 2-methylglutaronitrile (MGN), fluoroacetonitrile, p-fluorophenylacetonitrile, o-fluorobenzonitrile, 3-(trifluoromethyl)phenylacetonitrile, 3,5-bis(trifluoromethyl)phenylacetonitrile, 2,3,4,5,6-pentafluorobenzonitrile, and 3,5-bis(trifluoromethyl)phenylacetonitrile.

[0052] The carbonate solvent includes one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoropropylene carbonate, trifluoroethyl methyl carbonate and 2,2,2-trifluoroethyl ethyl carbonate.

[0053] The ether solvent includes one or more of 2-dimethoxyethane (DME), ethylene glycol dimethyl ether (EDG), dimethoxydimethyl ether (DMM), diethylene glycol dimethyl ether (DG), 1,3-dioxolane (DOL), triethylene glycol monoethyl ether (Trig), tetrahydrofuran (THF), and 2-methyl-tetrahydrofuran (2-Me-THF).

[0054] The phosphate ester solvent includes one or more of trimethyl phosphate (TMP), triethyl phosphate (TEP), tributyl phosphate (TBP), triphenyl phosphate (TPP), 4-isopropylphenyl diphenyl phosphate (IPPP), diphenyl octyl phosphate (DPOF), trioctyl phosphate (TOP), and dimethyl methylphosphonate (DMMP).

[0055] In some embodiments, the lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bisfluorosulfonyl imide (LiFSI), lithium trifluoromethylsulfonyl-perfluorobutylsulfonyl imide (LiTNFSI), lithium fluorosulfonyl-perfluorobutylsulfonyl imide (LiFNFSI), lithium bisoxalatoborate (LiBOB), lithium difluorooxalatoborate (LiDFOB), lithium difluorophosphate (LiPO2F2), and lithium nitrate (LiNO3).

[0056] In a preferred embodiment, the lithium salt includes at least two of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonyl-perfluorobutylsulfonylimide, lithium fluorosulfonyl-perfluorobutylsulfonylimide, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorophosphate, and lithium nitrate. The selection of multiple lithium salts significantly improves the cycling performance of batteries containing high-nickel cathodes under high voltage, and the appropriate control of the ratio of the double salt addition significantly increases the ionic conductivity of the electrolyte.

[0057] In some embodiments, the electrolyte further includes a functional additive, wherein the functional additive includes one or more of fluoroethylene carbonate, 1,3-propane sultone, vinylene carbonate, and vinyl sulfate.

[0058] In some embodiments, based on the total mass of the electrolyte being 100%, the mass percentage of the functional additive is 0.01% to 30%.

[0059] On the other hand, an embodiment of the present application provides a battery, comprising a positive electrode, a negative electrode, a separator, and the electrolyte as described in any one of the above.

[0060] In some embodiments, the separator includes one or more of polypropylene, polyethylene, PP / PE / PP composite film, polyvinylidene fluoride, polyacrylonitrile, ceramic separator, ceramic polyamide, aramid and non-woven fabric.

[0061] The positive electrode includes one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobaltate, lithium manganese oxide, lithium nickel oxide, ternary material, lithium-rich manganese base, lithium nickel manganese oxide, and lithium vanadium oxyphosphate.

[0062] The negative electrode includes one or more of a graphite negative electrode, a silicon-oxygen negative electrode, a silicon-carbon negative electrode, a silicon negative electrode, a tin negative electrode, a tin oxide negative electrode, a tin alloy negative electrode, a lithium metal negative electrode, a lithium alloy negative electrode and a lithium-free negative electrode.

[0063] On the other hand, an embodiment of the present application provides a battery comprising a positive electrode, a negative electrode, a separator and a gel electrolyte, wherein the gel electrolyte comprises the electrolyte described in any one of the above items, and the mass of the electrolyte is 0.5% to 50% of the mass of the gel electrolyte.

[0064] On the other hand, an embodiment of the present application provides a battery, comprising a positive electrode, a negative electrode, a separator, a solid electrolyte and an electrolyte as described above, wherein the mass of the electrolyte is 0.5% to 50% of the mass of the solid electrolyte.

[0065] In some embodiments, the solid electrolyte includes an inorganic solid electrolyte, a polymer solid electrolyte, and a composite solid electrolyte.

[0066] The inorganic solid electrolyte includes one or more of an oxide solid electrolyte, a sulfide solid electrolyte, and a halide solid electrolyte.

[0067] The polymer solid electrolyte includes one or more of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate;

[0068] The composite solid electrolyte includes an inorganic filler and a polymer matrix, wherein the inorganic filler includes one or more of an oxide solid electrolyte, a sulfide solid electrolyte, and a halide solid electrolyte; and the polymer matrix includes one or more of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0069] In some embodiments, the oxide solid electrolyte includes one or more of LLZO, LLTO, LATP, and LAGP; the sulfide solid electrolyte includes one or more of LGPS, LPS, and LPSCl; and the halide solid electrolyte includes one or more of Li3YCl6, Li3ScCl6, and Li3YBr6.

[0070] On the other hand, an embodiment of the present application provides an energy storage device, comprising a battery as described above. It should be noted that the battery can be a liquid, semi-solid laminate, wound or cylindrical battery.

[0071] The present application is further described below through examples.

[0072] Example 1

[0073] This example is used to illustrate the electrolyte disclosed in this application, and includes the following steps:

[0074] Electrolyte: The solvents FEC, DMC, and EMC are mixed in a mass ratio of 1:1:1, the first additive ethoxypentafluorocyclotriphosphazene (PFPN) and the second additive 3,4-difluorobenzonitrile (34FBN) are mixed in a mass ratio of 7:3, and then the lithium salt LiPF6 is added at a concentration of 1 mol / L.

[0075] Battery preparation

[0076] Preparation of positive electrode

[0077] The positive electrode active material NCM811, conductive carbon black Super-P, and binder polyvinylidene fluoride (PVDF) described in claim 1 are mixed in a mass ratio of 93:4:3, and then dispersed in an appropriate amount of N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry. The resulting slurry is evenly coated on both sides of an aluminum foil, dried, rolled, and vacuum-dried, and then welded with aluminum lead wires using an ultrasonic welder to obtain a positive electrode sheet. The thickness of the positive electrode sheet is between 120 and 150 μm.

[0078] Preparation of negative electrode sheet

[0079] The negative electrode uses a metallic lithium negative electrode.

[0080] Preparation of battery cells

[0081] A three-layer separator with a thickness of 20 μm was placed between the positive and negative electrodes prepared above, and then the sandwich structure consisting of the positive, negative and separators was stacked and encapsulated with aluminum-plastic film to produce a soft-pack battery cell with a capacity of 1 Ah ready for liquid injection.

[0082] The battery is obtained after the battery core is injected with liquid and formed.

[0083] Example 2-20

[0084] Examples 2-20 are used to illustrate the electrolyte disclosed in this application, including most of the operating steps in the above-mentioned Example 1, with the difference being that the formula in Table 1 is used.

[0085] Comparative Examples 1-3

[0086] The comparative example is used to compare and illustrate the electrolyte disclosed in the present application, and includes most of the operating steps in Example 1, except that the formula in Table 1 is used.

[0087] Table 1

[0088] Performance Testing

[0089] 1. The batteries prepared in the above examples and comparative examples were subjected to the following performance tests:

[0090] (1) Flame retardancy test of electrolyte: immerse a spherical glass fiber cotton core (about 1 cm in diameter) in the electrolyte, take it out, drain and weigh it, calculate the amount of liquid absorbed by the cotton ball, and ignite the cotton ball after absorbing the liquid with a spray gun. Use a stopwatch to record the burning time of the cotton ball after the spray gun is removed, and calculate the SET value. If the self-extinguishing time is more than 20 seconds, it is considered flammable, 5-20 seconds is flame retardant, and less than 5 seconds is non-flammable.

[0091] (2) Overcharge protection test: At 25±3℃, charge the battery to 100% SOC at a constant current of 0.5C, then overcharge it from 100% SOC to 200% SOC and hold it for 1h, then discharge it to 3.0V at 0.5C. The charge and discharge voltage range is set to 3.0-6.0V. The cycle test is repeated 3 times, and the voltage-time curve is recorded. If the battery voltage does not exceed 4.8V during the test and there is no leakage, fire or explosion during the overcharge process, the battery has passed the overcharge protection test. Otherwise, the battery is deemed to have failed the overcharge protection test.

[0092] (3) High pressure cycle temperature test:

[0093] The battery was tested for cyclic charge and discharge at 25°C and 0.2C / 0.5D in the voltage range of 3.0V to 4.4V, and the capacity retention rate after 100 cycles was recorded.

[0094] The test results are shown in Table 2.

[0095] Table 2

[0096] It can be seen from the test results of Examples 1-20 that if the sum of the amounts of the first additive and the second additive in the electrolyte is not within the range of 0.5%-15%, smoke may occur, posing a safety hazard.

[0097] The test results of Comparative Example 2 show that if only fluorobenzonitrile additives are used, the overcharge protection performance of lithium metal batteries without phosphazene additives does not meet the requirements, and the flame retardancy is reduced. The test results of Example 1 and Comparative Examples 1 and 2 show that the phosphazene additives provided by this application and the fluorobenzonitrile additives work synergistically to effectively improve the safety and cycle life of lithium metal batteries.

[0098] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. An electrolyte, characterized in that: The method comprises a lithium salt, a solvent and an additive, wherein the additive comprises a first additive and a second additive, wherein the first additive is one or more compounds represented by formula I, and the second additive is one or more compounds represented by formula II; wherein said R1-R6 are each independently selected from F, C6-C26 fluorine-substituted phenoxy, C1-C20 fluorine-substituted alkoxy, said R7-R 12 are independently selected from halogen, C1-C20 fluorine-substituted alkyl, cyano, amino, and said R7-R 12 At least one of the halogens is selected from cyano, and the halogen includes one or more of fluorine, chlorine, bromine and iodine.

2. The electrolyte according to claim 1, characterized in that The sum of the added amounts of the first additive and the second additive is 0.5% to 15% of the mass of the electrolyte.

3. The electrolyte according to claim 2, characterized in that The mass ratio of the first additive to the second additive is (0.1-50):(50-0.1).

4. The electrolyte according to claim 1, characterized in that The first additive comprises one or more of hexaethoxyfluorophosphazene (HEPN), hexamethoxyphosphazene (HMPN), bis(2(2-methoxyethoxy)ethoxy)phosphazene (MEEP), ethoxypentafluorocyclotriphosphazene (PFPN), hexafluorocyclotriphosphazene (HFPN), phenoxypentafluorocyclotriphosphazene (FPPN), trifluoroethoxypentafluorocyclotriphosphazene (TFPN), 4-methoxy-phenoxypentafluorocyclotriphosphazene (4-MPPFPP), hexaphenoxycyclotriphosphazene (HPCTP), and hexa(2,2,2-trifluoroethoxy)cyclotriphosphazene; The second additive includes p-fluorobenzonitrile, o-fluorobenzonitrile, 3,4-difluorobenzonitrile (34FBN), 3,5-difluorobenzonitrile (35FBN), 2,3-difluorobenzonitrile (23FBN), 2,4,6-trifluorobenzonitrile (246TFBN), 3,4,5-trifluorobenzonitrile (345TFBN), 2,3,4,5,6-pentafluorobenzonitrile (5FBN), 4-bromo-2-fluorobenzonitrile (4B2FBN), 2,4-difluorobenzonitrile (24 One or more of 4-(trifluoromethyl)benzonitrile, 4-bromo-2,3,5,6-tetrafluorobenzonitrile and 4-amino-2-(trifluoromethyl)benzonitrile.

5. The electrolyte according to claim 1, characterized in that The solvent includes an organic solvent, and the organic solvent includes one or more of an amide solvent, a silane solvent, a sulfone solvent, a nitrile solvent, a carbonate solvent, an ether solvent, and a phosphate solvent.

6. The electrolyte according to claim 5, characterized in that The amide solvents include one or more of 2,2,2-trifluoro-N,N-dimethylacetamide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-dimethylpropionamide, formamide, N,N-diethylacetamide, N,N-dimethylisobutyramide, N,N-diethylacetoacetamide, N-methyl-N-vinylacetamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N,N-dimethylfluorosulfonamide and N,N-dimethyltrifluoromethanesulfonamide; The silane solvent includes one or more of vinyltrimethoxysilane, vinyltriethoxysilane, tris(trimethylsilyl)borate, dimethoxydimethylsilane, diethoxydimethylsilane, triethoxymethylsilane, methoxytrimethylsilane and 1,1,3,3-tetramethyldisiloxane; The sulfone solvent includes one or more of dimethyl sulfoxide, tetramethylene sulfone, ethyl vinyl sulfone, methyl vinyl sulfone and allyl methyl sulfone; The nitrile solvent includes one or more of succinonitrile, 1,3,6-hexanetrinitrile, acetonitrile, glutaronitrile, adiponitrile, butyronitrile, 2-methylglutaronitrile, fluoroacetonitrile, p-fluorophenylacetonitrile, o-fluorobenzonitrile, 3-(trifluoromethyl)phenylacetonitrile, 3,5-bis(trifluoromethyl)phenylacetonitrile, 2,3,4,5,6-pentafluorobenzonitrile, and 3,5-bis(trifluoromethyl)phenylacetonitrile; The carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, difluoroethylene carbonate, trifluoropropylene carbonate, trifluoroethyl methyl carbonate and 2,2,2-trifluoroethyl ethyl carbonate; The ether solvent includes one or more of 2-dimethoxyethane, ethylene glycol dimethyl ether, dimethoxydimethyl ether, diethylene glycol dimethyl ether, 1,3-dioxolane, triethylene glycol monoethyl ether, tetrahydrofuran and 2-methyl-tetrahydrofuran; The phosphate ester solvent includes one or more of trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, 4-isopropylphenyl diphenyl phosphate, diphenyl octyl phosphate, trioctyl phosphate and dimethyl methylphosphonate.

7. The electrolyte according to claim 1, characterized in that The lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bisfluorosulfonylimide, lithium trifluoromethylsulfonyl-perfluorobutylsulfonylimide, lithium fluorosulfonyl-perfluorobutylsulfonylimide, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium difluorophosphate and lithium nitrate.

8. A battery, characterized in that: The invention comprises a positive electrode, a negative electrode, a separator and the electrolyte according to any one of claims 1 to 7.

9. The battery according to claim 8, characterized in that The diaphragm includes one or more of polypropylene, polyethylene, PP / PE / PP composite film, polyvinylidene fluoride, polyacrylonitrile, ceramic diaphragm, ceramic polyamide, aramid and non-woven fabric; The positive electrode comprises one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobaltate, lithium manganese oxide, lithium nickel oxide, ternary material, lithium-rich manganese base, lithium nickel manganese oxide, and lithium vanadium phosphate; The negative electrode includes one or more of a graphite negative electrode, a silicon-oxygen negative electrode, a silicon-carbon negative electrode, a silicon negative electrode, a tin negative electrode, a tin oxide negative electrode, a tin alloy negative electrode, a lithium metal negative electrode, a lithium alloy negative electrode and a lithium-free negative electrode.

10. A battery, characterized in that: The invention comprises a positive electrode, a negative electrode, a separator and a gel electrolyte, wherein the gel electrolyte comprises the electrolyte according to any one of claims 1 to 7, and the mass of the electrolyte is 0.5% to 50% of the mass of the gel electrolyte.

11. A battery, characterized in that: The invention comprises a positive electrode, a negative electrode, a separator, a solid electrolyte and the electrolyte according to any one of claims 1 to 7, wherein the mass of the electrolyte is 0.5% to 50% of the mass of the solid electrolyte.

12. The battery according to claim 11, characterized in that The solid electrolyte includes inorganic solid electrolyte, polymer solid electrolyte and composite solid electrolyte; The inorganic solid electrolyte includes one or more of an oxide solid electrolyte, a sulfide solid electrolyte, and a halide solid electrolyte; The polymer solid electrolyte includes one or more of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate; The composite solid electrolyte includes an inorganic filler and a polymer matrix, wherein the inorganic filler includes one or more of an oxide solid electrolyte, a sulfide solid electrolyte, and a halide solid electrolyte; and the polymer matrix includes one or more of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

13. The battery according to claim 12, characterized in that The oxide solid electrolyte includes one or more of LLZO, LLTO, LATP, and LAGP; the sulfide solid electrolyte includes one or more of LGPS, LPS, and LPSCl; and the halide solid electrolyte includes one or more of Li3YCl6, Li3ScCl6, and Li3YBr6.

14. An energy storage device, characterized in that: A battery comprising the battery according to any one of claims 8 to 13.

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