WO2021180135A1 - 锂二次电池电解液及其制备方法、锂二次电池和终端 - Google Patents

锂二次电池电解液及其制备方法、锂二次电池和终端 Download PDF

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WO2021180135A1
WO2021180135A1 PCT/CN2021/080039 CN2021080039W WO2021180135A1 WO 2021180135 A1 WO2021180135 A1 WO 2021180135A1 CN 2021080039 W CN2021080039 W CN 2021080039W WO 2021180135 A1 WO2021180135 A1 WO 2021180135A1
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secondary battery
lithium secondary
compound
cyclotriphosphazene
battery electrolyte
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PCT/CN2021/080039
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English (en)
French (fr)
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马强
秦德君
李阳兴
邓耀明
刘中波
谢封超
邓永红
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华为技术有限公司
深圳新宙邦科技股份有限公司
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application relates to the technical field of lithium secondary batteries, in particular to lithium secondary battery electrolytes and preparation methods thereof, lithium secondary batteries and terminals.
  • the embodiment of the application discloses an electrolyte for a lithium secondary battery.
  • the additives can fully play a synergistic effect, which can effectively take into account the electrochemical performance and safety performance of the battery. .
  • the first aspect of the embodiments of the present application discloses an electrolyte for a lithium secondary battery, including a lithium salt, a non-aqueous organic solvent, and a functional additive.
  • the functional additive includes the following in the electrolyte for the lithium secondary battery: Components of:
  • the mass percentage of the cyclotriphosphazene compound is 5%-10%.
  • the mass percentage of the fluorocarbonate is 5%-7%.
  • the mass percentage of the sulfur-containing ester compound is 3%-5%.
  • the mass percentage of the nitrile compound is 3% to 5%.
  • the mass ratio of the cyclotriphosphazene compound to the nitrile compound is 0.5:1 to 4:1.
  • the mass ratio of the fluorocarbonate to the nitrile compound is 1:1 to 4:1.
  • the mass ratio of the sulfur-containing ester compound to the nitrile compound is 0.5:1 to 3:1.
  • the ratio of the mass of the cyclotriphosphazene compound to the sum of the masses of the sulfur-containing ester compound and the nitrile compound is 0.5:1 to 2:1.
  • R 1 , R 2 , R 3 , R 4 , R 5 , R 6 can be selected from fluorine, chlorine, bromine, alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, respectively , Alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy, haloaryloxy, substituted phosphate, substituted sulfonic acid, substituted imide, and substituted sulfonimide Any of the bases.
  • the cyclotriphosphazene compound includes methoxy (pentafluoro) cyclotriphosphazene, ethoxy (pentafluoro) cyclotriphosphazene (FPN), and phenoxy (pentafluoro) cyclotriphosphazene.
  • PFPN phosphazene
  • trifluoroethoxy (pentafluoro) cyclotriphosphazene methylsulfonic acid (pentafluoro) cyclotriphosphazene and ethylsulfonic acid (pentafluoro) cyclotriphosphazene
  • PFPN phosphazene
  • methylsulfonic acid pentafluoro
  • ethylsulfonic acid ethylsulfonic acid
  • the fluorocarbonate includes one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), and trifluoromethyl ethylene carbonate (TFEC).
  • FEC fluoroethylene carbonate
  • DFEC difluoroethylene carbonate
  • TFEC trifluoromethyl ethylene carbonate
  • the sulfur-containing compound includes dimethyl sulfite, diethyl sulfite, vinyl sulfite (ES), vinyl sulfate (DTD), methylene disulfonate (MMDS), One or more of 1,3-propane sultone (PS), 1,4-butane sultone (BS), dimethyl sulfate, and diethyl sulfate.
  • the nitrile compounds include mononitrile and/or polynitrile compounds.
  • the polynitrile compound includes succinonitrile (SN), glutaronitrile (GLN), adiponitrile (ADN), 1,2-bis(2-cyanoethoxy)ethane (DENE ), one or more of 1,3,6-hexanetrinitrile (HTCN).
  • the lithium salt includes LiClO 4 , LiBF 4 , LiPF 6 , LiAsF 6 , LiPF 2 O 2 , LiCF 3 SO 3 , LiTDI, LiB(C 2 O 4 ) 2 (LiBOB), LiBF 2 C 2 O 4 (LiDFOB), Li[(CF 3 SO 2 ) 2 N], Li[(FSO 2 ) 2 N] and Li[(C m F 2m+1 SO 2 )(C n F 2n+1 SO 2 ) One or more of N], where m and n are natural numbers.
  • the molar concentration of the lithium salt in the electrolyte of the lithium secondary battery is 0.01 mol/L-2.0 mol/L.
  • the non-aqueous organic solvent includes one or more of carbonate-based solvents, ether-based solvents, and carboxylate-based solvents.
  • the second aspect of the embodiments of the present application provides a method for preparing an electrolyte for a lithium secondary battery, which includes the following steps:
  • the functional additives include the following components in the lithium secondary battery electrolyte with the following mass percentages:
  • the third aspect of the embodiments of the present application provides a lithium secondary battery, including a positive electrode, a negative electrode, a separator, and an electrolyte.
  • the electrolyte uses the lithium secondary battery electrolyte described in the first aspect of the embodiments of the present application.
  • An embodiment of the present application also provides a terminal, including a housing, and a display module, an electronic component module, and a battery housed in the housing, and the battery is the display module and the electronic component module.
  • the battery is powered by the group, and the battery includes the lithium secondary battery described in the third aspect of the embodiment of the present application.
  • the additives can fully exert a synergistic effect, so that the electrolyte can effectively take into account the high Voltage cycle performance, high safety performance, high temperature storage performance, rate performance and other aspects of performance, ultimately make the overall performance of the battery at a better level.
  • FIG. 1 is a schematic diagram of the structure of a lithium ion secondary battery provided by an embodiment of the present application
  • FIG. 2 is a schematic structural diagram of a terminal provided by an embodiment of the present application.
  • Fig. 3 is a graph of the cycle performance test of batteries prepared in Examples 1-3 of the present application.
  • the core components of a lithium ion secondary battery include a positive electrode material 101, a negative electrode material 102, an electrolyte 103, a separator 104, and corresponding connecting accessories and circuits.
  • the positive electrode material 101 and the negative electrode material 102 can deintercalate lithium ions to realize energy storage and release.
  • the electrolyte 103 is a medium for lithium ions to be transported between the positive and negative electrodes, which plays an important role in the electrochemical performance and safety performance of the battery. effect.
  • the electrolyte is mainly composed of lithium salt, non-aqueous organic solvent (normally carbonate solvent) and additives.
  • the lithium secondary battery electrolyte provided by the embodiments of the present application includes a lithium salt, a non-aqueous organic solvent, and a functional additive, wherein the functional additive includes the following components in the lithium secondary battery electrolyte with the following mass percentages:
  • the lithium secondary battery electrolyte provided by the embodiments of the present application contains a variety of functional additives.
  • the cyclotriphosphazene compound has excellent flame retardant properties and can improve battery safety; fluorocarbonate has a good negative electrode film-forming function, It can improve battery cycle performance; sulfur-containing ester compounds can inhibit high-temperature gas production and improve the high-temperature storage performance of high-voltage batteries; nitrile compounds can improve battery high-voltage cycle performance.
  • the added amount of each functional additive directly affects the performance of each additive, and also affects other aspects of the battery performance, such as battery low-temperature performance and rate performance.
  • the added amount of each additive is appropriately controlled, wherein the content of cyclotriphosphazene compound is 3%-12%, the content of fluorocarbonate is 3%-9%, and the content of sulfur-containing ester compounds is 2%- 6%, the content of nitrile compounds is 1%-6%, so as to give full play to the synergy between various additives, so that the battery has excellent high-voltage cycle performance, high-temperature storage performance and high safety performance, but also has excellent low-temperature performance. Performance and rate performance, and the electrolyte has good compatibility with the positive and negative materials, which effectively takes into account the electrochemical performance and safety performance of the battery, so that the overall performance of the battery is at a better level.
  • the mass percentage of the cyclotriphosphazene compound is 5%-10%.
  • the mass percentage of fluorocarbonate is 5%-7%.
  • the mass percentage of sulfur-containing ester compounds is 3% to 5%.
  • the mass percentage of the nitrile compound is 3% to 5%.
  • the mass ratio of the cyclotriphosphazene compound to the nitrile compound may be 0.5:1 to 4:1.
  • the mass ratio of the cyclotriphosphazene compound to the nitrile compound may also be 1:1 to 3:1, or 1.5:1 to 2.5:1.
  • the mass ratio of the fluorocarbonate to the nitrile compound may be 1:1 to 4:1.
  • the mass ratio of the fluorocarbonate to the nitrile compound is controlled at 1:1 to 4:1, which can effectively take into account the balance between the film-forming performance of the positive electrode and the film-forming performance of the negative electrode of the electrolyte. If the ratio is too small, the fluorocarbonate will not be able to form an effective and stable SEI film to cope with the side reactions of nitrile compounds on the negative electrode; if the ratio is too large, the fluorocarbonate will produce gas under high voltage and high temperature conditions. , Is not conducive to obtaining high-temperature storage performance and high-voltage cycle performance.
  • the mass ratio of the fluorocarbonate to the nitrile compound may also be 1.25:1 to 3.5:1, or 2:1 to 3:1.
  • the mass ratio of the sulfur-containing ester compound to the nitrile compound may be 0.5:1 to 3:1.
  • the mass ratio of sulfur-containing ester compounds and nitrile compounds is controlled at 0.5:1 to 3:1, which can effectively balance high-temperature storage performance and high-voltage cycle performance. If the ratio is too small, sulfur-containing ester compounds cannot effectively suppress high-temperature gas production, which is not conducive to the improvement of high-temperature storage performance; if the ratio is too large, the battery impedance is too large, which will affect battery cycle performance, rate performance, and low-temperature performance .
  • the mass ratio of sulfur-containing ester compounds to nitrile compounds may also be 0.75:1 to 2.5:1, or 1:1 to 2:1.
  • the ratio of the mass of the cyclotriphosphazene compound to the total mass of the sulfur-containing ester compound and the nitrile compound may be 0.5:1 to 2:1.
  • the ratio of the mass of cyclotriphosphazene compound to the total mass of sulfur-containing ester compound and nitrile compound is controlled at 0.5:1 to 2:1, which can effectively take into account the balance between electrolyte conductivity and pole piece wettability. If the ratio is too small, it will greatly affect the battery safety and electrode wettability; if the ratio is too large, it will affect the battery's low temperature and rate performance.
  • the cyclotriphosphazene compound is a kind of phosphazene compound with a stable six-membered heterocyclic ring and conjugated structure. Single and double bonds are connected, the cyclotriphosphazene compound can be hexachlorocyclotriphosphazene or a derivative of hexachlorocyclotriphosphazene.
  • the molecular structure of the cyclotriphosphazene compound can be as shown in formula (I):
  • R 1 , R 2 , R 3 , R 4 , R 5 , R 6 can be selected from fluorine, chlorine, bromine, alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, respectively , Alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy, haloaryloxy, substituted phosphate, substituted sulfonic acid, substituted imide, and substituted sulfonimide Any of the bases.
  • the substituted sulfonic acid group forms a PO bond chemical bond with the phosphorus atom in the six-membered ring structure through the oxygen atom.
  • Substituted sulfonic acid group, substituted imide group and substituted sulfonimide group contains halogen-containing substituents.
  • the halogen can be fluorine, chlorine, bromine, or iodine.
  • the halogenation can be either full or partial Halogenated.
  • Alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, and haloalkenyloxy may be linear or branched.
  • R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are all chlorine
  • the formula (I) is hexachlorocyclotriphosphazene.
  • the formula (I) is a hexachlorocyclotriphosphazene derivative.
  • the cyclotriphosphazene compound may specifically be methoxy (pentafluoro) cyclotriphosphazene, ethoxy (pentafluoro) cyclotriphosphazene (FPN), phenoxy (pentafluoro) Cyclotriphosphazene (PFPN), trifluoroethoxy (pentafluoro) cyclotriphosphazene, methylsulfonic acid (pentafluoro) cyclotriphosphazene and ethylsulfonic acid (pentafluoro) cyclotriphosphazene One or more of.
  • the electrolyte may contain one or more cyclotriphosphazene compounds.
  • the fluorocarbonate may be ethylene carbonate substituted with a fluorine-containing group, and the fluorine-containing group may be a fluorine atom or a fluorine-containing hydrocarbon group.
  • the fluorocarbonate may include one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), and trifluoromethyl ethylene carbonate (TFEC).
  • the sulfur-containing ester compound may be a sulfate compound, a sulfite compound, or a sulfonate compound.
  • the sulfur-containing ester compound may be dimethyl sulfite, diethyl sulfite, vinyl sulfite (ES), vinyl sulfate (DTD), methylene disulfonate One or more of (MMDS), 1,3-propane sultone (PS), 1,4-butane sultone (BS), dimethyl sulfate, and diethyl sulfate.
  • the nitrile compounds include mononitrile and/or polynitrile compounds.
  • Mononitrile compounds are nitrile compounds containing one cyano group in the molecular structure
  • polynitrile compounds are nitrile compounds containing multiple cyano groups (for example, two or three) in the molecular structure.
  • the polynitrile compound may be succinonitrile (SN), glutaronitrile (GLN), adiponitrile (ADN), 1,2-bis(2-cyanoethoxy)ethane ( DENE), one or more of 1,3,6-hexanetrinitrile (HTCN).
  • the functional additives only include cyclotriphosphazene compounds, fluorocarbonates, sulfur-containing ester compounds, and nitrile compounds. In other embodiments of the present application, the functional additives can also be added with other types of substances according to actual needs.
  • the lithium salt includes LiClO 4 , LiBF 4 , LiPF 6 , LiAsF 6 , LiPF 2 O 2 , LiCF 3 SO 3 , LiTDI, LiB(C 2 O 4 ) 2 (LiBOB), LiBF 2 C 2 O 4 (LiDFOB), Li[(CF 3 SO 2 ) 2 N], Li[(FSO 2 ) 2 N] and Li[(C m F 2m+1 SO 2 )(C n F 2n+1 SO 2 )N One or more of ], where m and n are natural numbers.
  • the molar concentration of the lithium salt in the electrolyte of the lithium secondary battery is 0.01 mol/L-2.0 mol/L. Further, it may be 0.05 mol/L-1.5 mol/L, 0.5 mol/L-1.0 mol/L.
  • the non-aqueous organic solvent includes one or more of carbonate-based solvents, ether-based solvents, and carboxylate-based solvents.
  • Non-aqueous organic solvents can be mixed in any ratio.
  • carbonate solvents include cyclic carbonates or chain carbonates.
  • the cyclic carbonates may specifically be ethylene carbonate (EC), propylene carbonate (PC), ⁇ -butyrolactone (GBL), butylene carbonate.
  • EC ethylene carbonate
  • PC propylene carbonate
  • GBL ⁇ -butyrolactone
  • BC butylene carbonate
  • the chain carbonate can specifically be dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate (DPC) One or more of.
  • Ether solvents include cyclic ethers or chain ethers.
  • Cyclic ethers can specifically be 1,3-dioxolane (DOL), 1,4-dioxane (DX), crown ether, tetrahydrofuran (THF), One or more of 2-methyltetrahydrofuran (2-CH 3 -THF) and 2-trifluoromethyltetrahydrofuran (2-CF 3 -THF); the chain ether may specifically be dimethoxymethane One or more of (DMM), 1,2-dimethoxyethane (DME), and diglyme (TEGDME).
  • DOL 1,3-dioxolane
  • DX 1,4-dioxane
  • crown ether tetrahydrofuran
  • THF tetrahydrofuran
  • 2-CH 3 -THF 2-methyltetrahydrofuran
  • 2-CF 3 -THF 2-trifluoromethyltetrahydrofuran
  • the carboxylic acid ester solvent may specifically be one of methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), butyl propionate or Many kinds.
  • the lithium secondary battery electrolyte provided by the embodiments of the application contains a variety of functional additives, and the added amount of each additive is accurately controlled within a suitable range, so that the additives can fully play a synergistic effect and effectively take into account the electrochemical performance and safety of the battery Performance, the overall performance of the battery is at a better level; in addition, the lithium secondary battery electrolyte provided in the embodiments of the present application can better take into account all aspects of performance by further adjusting the mass ratio between the additives.
  • the embodiment of the present application also provides a method for preparing the above-mentioned lithium secondary battery electrolyte, which includes the following steps:
  • the functional additives include the following components in the lithium secondary battery electrolyte with the following mass percentages:
  • the embodiments of the present application also provide a lithium secondary battery, including a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte adopts the lithium secondary battery electrolyte provided above in the embodiments of the present application.
  • the lithium secondary battery provided by the embodiments of the present application has excellent high-voltage cycle performance, high safety, and excellent low temperature due to the addition of various functional additives to the electrolyte and the precise adjustment of the added amount of each additive within a suitable range. Performance and rate performance.
  • the battery may be a lithium ion battery.
  • the battery provided in the embodiments of this application can be used in terminal consumer products, such as mobile phones, tablet computers, mobile power supplies, portable computers, notebook computers, and other wearable or movable electronic devices, and automobiles, to improve product safety and reliability .
  • the positive electrode includes a positive electrode active material capable of reversibly intercalating/deintercalating lithium ions.
  • the selection of the positive electrode active material in this application is not particularly limited. It can be a conventionally used positive electrode active material for existing lithium secondary batteries.
  • the positive electrode active material may be lithium cobalt oxide (LiCoO 2 ), lithium iron phosphate (LiFePO 4 ), lithium nickel cobalt manganese oxide (LiNi 0.6 Co 0.2 Mn 0.2 ), polyanionic lithium compound LiM x (PO 4 ) y ( M is Ni, Co, Mn, Fe, Ti, V, 0 ⁇ x ⁇ 5, 0 ⁇ y ⁇ 5), etc.
  • the negative electrode includes a negative electrode active material capable of accepting or releasing lithium ions.
  • the selection of the negative electrode active material in this application is not particularly limited, and it may be a negative electrode active material conventionally used in existing lithium secondary batteries.
  • the negative electrode active material can be metallic lithium, lithium alloy, lithium titanate, natural graphite, artificial graphite, mesophase carbon microsphere graphite, amorphous carbon, carbon fiber, carbon nanotube, hard carbon, soft carbon, graphene, graphene oxide , Silicon, silicon carbon, silicon oxygen compound, silicon metal compound, lithium titanate (Li 4 Ti 5 O 12 ), one or more of them.
  • the diaphragm can be an existing conventional diaphragm, including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP/PE, double-layer PP/PP, and three-layer PP/ Diaphragm such as PE/PP.
  • single-layer PP polypropylene
  • PE polyethylene
  • double-layer PP/PE double-layer PP/PP
  • three-layer PP/ Diaphragm such as PE/PP.
  • an embodiment of the present application also provides a terminal.
  • the terminal 200 may be a mobile phone, a tablet computer, a notebook computer, a portable computer, a smart wearable product, a car, etc., including a housing 201 and a housing 201.
  • the battery provides power for the electronic components.
  • the battery is the lithium secondary battery provided in the above embodiment of the application.
  • the housing 201 may include With the front cover on the front side and the rear case assembled on the rear side, the battery can be fixed inside the rear case.
  • ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC) and propyl propionate (PP) are mixed to form an organic solvent, and then fully dried lithium hexafluorophosphate (LiPF 6 ) and lithium difluoroborate (LiDFOB) were dissolved in the above solvent, stirred and mixed into a uniform solution, and then ethoxy (pentafluoro) cyclotriphosphazene (FPN), fluoroethylene carbonate (FEC), 1,3-Propane sultone (PS), succinonitrile (SN), and adiponitrile (ADN) were added to the above-mentioned solution, and mixed uniformly to prepare a lithium secondary battery electrolyte.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • PC propylene carbonate
  • PP propyl propionate
  • PP propyl propionate
  • the concentration of LiPF 6 is 1.0 mol/L
  • the concentration of LiDFOB is 0.05 mol/L
  • the mass percentages of EC, DEC, PC and PP are 25:25:10:40
  • FPN, FEC, PS, SN and ADN The mass percentages are 5%, 5%, 3%, 2% and 2% respectively.
  • PVDF polyvinylidene fluoride
  • NMP N-methylpyrrolidone
  • the positive pole piece, negative pole piece and commercial PE separator prepared above are made into batteries, and polymer packaging is used, and the lithium secondary battery electrolyte prepared in Example 1 above is poured into a 4Ah soft pack after chemical conversion and other processes. Lithium secondary battery.
  • ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC) and propyl propionate (PP) are mixed to form an organic solvent, and then fully dried lithium hexafluorophosphate (LiPF6) and lithium difluoroborate (LiDFOB) are dissolved in the above solvent, stirred and mixed into a uniform solution, and then ethoxy (pentafluoro) cyclotriphosphazene (FPN), fluoroethylene carbonate (FEC), 1 ,3-Propane sultone (PS), succinonitrile (SN), adiponitrile (ADN) and 1,2-bis(2-cyanoethoxy)ethane (DENE) were added to the above solution and mixed
  • the electrolyte of the lithium secondary battery is uniformly prepared.
  • the concentration of LiPF6 is 1.0 mol/L
  • the concentration of LiDFOB is 0.05 mol/L
  • the mass percentages of EC, DEC, PC and PP are 25:25:10:40
  • the mass percentages of DENE are 6%, 5%, 3%, 2%, 1% and 1% respectively.
  • the lithium secondary battery was prepared using the lithium secondary battery electrolyte prepared in Example 2, and the preparation method was the same as that in Example 1.
  • ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC) and propyl propionate (PP) are mixed to form an organic solvent, and then fully dried lithium hexafluorophosphate (LiPF 6 ) is dissolved in the above solvent, stirred and mixed into a uniform solution, and then ethoxy (pentafluoro) cyclotriphosphazene (FPN), fluoroethylene carbonate (FEC), 1,3-propanesulfonic acid Ester (PS), succinonitrile (SN), adiponitrile (ADN) and 1,2-bis(2-cyanoethoxy)ethane (DENE) were added to the above solutions respectively, and mixed uniformly to prepare the examples of this application 3 of the electrolyte.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • PC propylene carbonate
  • PP propyl propionate
  • LiPF 6 lithium hexafluorophosphate
  • FPN e
  • the concentration of LiPF 6 is 1.05 mol/L
  • the mass percentages of EC, DEC, PC and PP are 25:25:10:40
  • the mass percentages of FPN, FEC, PS, SN, AND and DENE are 7% respectively. , 5%, 3%, 1%, 2% and 1%.
  • a lithium secondary battery was prepared using the lithium secondary battery electrolyte prepared in Example 3, and the preparation method was the same as that in Example 1.
  • ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC) and propyl propionate (PP) are mixed to form an organic solvent, and then fully dried lithium hexafluorophosphate (LiPF 6 ) is dissolved in the above solvent, stirred and mixed into a uniform solution, and then phenoxy (pentafluoro) cyclotriphosphazene (PFPN), fluoroethylene carbonate (FEC), 1,3-propanesulfonic acid Ester (PS), succinonitrile (SN), adiponitrile (ADN), and 1,3,6-hexanetrinitrile (HTCN) were added to the above solutions and mixed uniformly to prepare the electrolyte of Example 4 of the present application.
  • PFPN phenoxy (pentafluoro) cyclotriphosphazene
  • FEC fluoroethylene carbonate
  • PS 1,3-propanesulfonic acid Ester
  • PS succinonitrile
  • ADN
  • the concentration of LiPF 6 is 1.05 mol/L
  • the mass percentages of EC, DEC, PC and PP are 25:25:10:40
  • the mass percentages of PFPN, FEC, PS, SN, AND and HTCN are 10% respectively. , 7%, 5%, 1%, 2% and 1%.
  • Example 4 The lithium secondary battery electrolyte prepared in Example 4 was used to prepare a lithium secondary battery, and the preparation method was the same as that in Example 1.
  • ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC) and propyl propionate (PP) are mixed to form an organic solvent, and then fully dried lithium hexafluorophosphate (LiPF 6 ) is dissolved in the above solvent, stirred and mixed into a uniform solution, and then ethoxy (pentafluoro) cyclotriphosphazene (FPN), fluoroethylene carbonate (FEC), vinyl sulfate (DTD), butyl Dinitrile (SN) and 1,3,6-hexanetrinitrile (HTCN) were added to the above solutions respectively, and mixed uniformly to prepare the electrolyte of Example 5 of the present application.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • PC propylene carbonate
  • PP propyl propionate
  • the concentration of LiPF 6 is 1.05 mol/L
  • the mass percentages of EC, DEC, PC and PP are 25:25:10:40
  • the mass percentages of FPN, FEC, DTD, SN and HTCN are 10% and 7 respectively. %, 3%, 2% and 1%.
  • a lithium secondary battery was prepared using the lithium secondary battery electrolyte prepared in Example 5, and the preparation method was the same as that in Example 1.
  • ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC) and propyl propionate (PP) are mixed to form an organic solvent, and then fully dried lithium hexafluorophosphate (LiPF 6 ) is dissolved in the above solvent, stirred and mixed into a uniform solution, and then ethoxy (pentafluoro) cyclotriphosphazene (FPN), fluoroethylene carbonate (FEC), 1,3-propanesulfonic acid Ester (PS) and adiponitrile (ADN) were added to the above solutions separately, and mixed uniformly to prepare the electrolyte of Example 6 of the present application.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • PC propylene carbonate
  • PP propyl propionate
  • LiPF 6 lithium hexafluorophosphate
  • FPN ethoxy (pentafluoro) cyclotriphosphazene
  • FPN fluoroethylene
  • the concentration of LiPF 6 is 1.05 mol/L
  • the mass percentages of EC, DEC, PC and PP are 25:25:10:40
  • the mass percentages of FPN, FEC, PS and AND are 12%, 7%, 5% and 2%.
  • Example 6 The lithium secondary battery electrolyte prepared in Example 6 was used to prepare a lithium secondary battery, and the preparation method was the same as that in Example 1.
  • ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC) and propyl propionate (PP) are mixed to form an organic solvent, and then fully dried lithium hexafluorophosphate (LiPF 6 ) is dissolved in the above solvent, stirred and mixed into a uniform solution, and then ethoxy (pentafluoro) cyclotriphosphazene (FPN), fluoroethylene carbonate (FEC), 1,3-propanesulfonic acid Ester (PS) and adiponitrile (ADN) were added to the above solutions separately, and mixed uniformly to prepare the electrolyte of Example 7 of the present application.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • PC propylene carbonate
  • PP propyl propionate
  • LiPF 6 lithium hexafluorophosphate
  • FPN ethoxy (pentafluoro) cyclotriphosphazene
  • FPN fluoroethylene
  • the concentration of LiPF 6 is 1.05 mol/L
  • the mass percentages of EC, DEC, PC and PP are 25:25:10:40
  • the mass percentages of FPN, FEC, PS and AND are 8%, 9%, 3% and 2%.
  • Example 7 The lithium secondary battery electrolyte prepared in Example 7 was used to prepare a lithium secondary battery, and the preparation method was the same as that in Example 1.
  • ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC) and propyl propionate (PP) are mixed to form an organic solvent, and then fully dried lithium hexafluorophosphate (LiPF 6 ) is dissolved in the above solvent, stirred and mixed into a uniform solution, and then ethoxy (pentafluoro) cyclotriphosphazene (FPN), fluoroethylene carbonate (FEC), 1,3-propanesulfonic acid Ester (PS), adiponitrile (ADN) and 1,3,6-hexanetrinitrile (HTCN) were added to the above solutions respectively, and mixed uniformly to prepare the electrolyte of Example 8 of the present application.
  • FPN ethoxy (pentafluoro) cyclotriphosphazene
  • FPN fluoroethylene carbonate
  • PS 1,3-propanesulfonic acid Ester
  • ADN adiponitrile
  • HTCN 1,3,6
  • the concentration of LiPF 6 is 1.05 mol/L
  • the mass percentages of EC, DEC, PC and PP are 25:25:10:40
  • the mass percentages of FPN, FEC, PS, AND and HTCN are 8% and 7 respectively. %, 2%, 3% and 2%.
  • Example 8 The lithium secondary battery electrolyte prepared in Example 8 was used to prepare a lithium secondary battery, and the preparation method was the same as that in Example 1.
  • ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC) and propyl propionate (PP) are mixed to form an organic solvent, and then fully dried lithium hexafluorophosphate (LiPF 6 ) is dissolved in the above solvent, stirred and mixed into a uniform solution, and then ethoxy (pentafluoro) cyclotriphosphazene (FPN), fluoroethylene carbonate (FEC), 1,3-propanesulfonic acid Ester (PS), adiponitrile (ADN) and 1,3,6-hexanetrinitrile (HTCN) were added to the above solutions respectively, and mixed uniformly to prepare the electrolyte of Example 9 of the present application.
  • FPN ethoxy (pentafluoro) cyclotriphosphazene
  • FPN fluoroethylene carbonate
  • PS 1,3-propanesulfonic acid Ester
  • ADN adiponitrile
  • HTCN 1,3,6
  • the concentration of LiPF 6 is 1.05 mol/L
  • the mass percentages of EC, DEC, PC and PP are 25:25:10:40
  • the mass percentages of FPN, FEC, PS, AND and HTCN are 3% and 7 respectively. %, 3%, 2% and 2%.
  • Example 9 The lithium secondary battery electrolyte prepared in Example 9 was used to prepare a lithium secondary battery, and the preparation method was the same as that in Example 1.
  • the battery Under the condition of an ambient temperature of 25°C ⁇ 3°C, the battery was subjected to a charge-discharge cycle test at a charge-discharge rate of 1.0/1.0C .
  • the voltage range of the graphite/LiCoO 2 battery was 3.0-4.5V, and the 100-week capacity retention rate was recorded.
  • the lithium secondary battery Under the condition of an ambient temperature of 25°C ⁇ 3°C, the lithium secondary battery is tested for rate performance at 0.2/0.2C, 0.2/0.5C, 0.2/1.0C, 0.2/1.5C and 0.2/2.0C charge and discharge rates,
  • the voltage range of the graphite/LiCoO 2 battery is 3.0-4.5V, and the 2C rate retention rate is recorded (2C discharge capacity/0.2C discharge capacity*100%).
  • the battery Under the condition of an ambient temperature of 25°C ⁇ 3°C, the battery is charged and discharged once at 0.2C/0.2C, this time the capacity is the initial capacity; the battery is fully charged again at 0.2C, and the charged battery is at 70°C Leave it for 24 hours, then leave it open for 2 hours at room temperature, discharge at a constant current of 0.2C to the termination voltage, and record it as the remaining capacity.
  • the voltage range of the graphite/LiCoO 2 battery is 3.0-4.5V. Record the remaining capacity retention rate (remaining capacity) /Initial capacity*100%).
  • Example 1-9 The test results of Examples 1-9 are listed in Table 1, and the cyclic test results of Examples 1-3 are listed in FIG. 3.
  • the electrolytes of Examples 1-9 of the present application have both certain flame resistance, high-voltage cycle performance, rate performance, and high-temperature storage performance. This is due to the performance of Examples 1-9 of the present application.
  • the electrolyte is simultaneously added with four functional additives including cyclotriphosphazene compound, fluorocarbonate, sulfur-containing ester compound and nitrile compound. Among them, when the electrolyte is heated, the phosphazene group of the cyclotriphosphazene compound will decompose to produce P-based free radicals.
  • Fluorocarbonate has a good negative electrode film-forming function, which can improve battery cycle performance; sulfur-containing ester compounds can inhibit high-temperature gas production and improve the high-temperature storage performance of high-voltage batteries; nitrile compounds can improve battery high-voltage Cycle performance.
  • Examples 1-9 of this application can give full play to the synergy between various additives by controlling the content of each additive within a suitable range, so that the battery performance can be fully exerted, and the electrochemical performance and safety performance of the battery are taken into account, where the electrolyte ignition time is ⁇ 3s, self-extinguishing time ⁇ 23s, the capacity retention rate of the battery after 100 weeks of cycling is above 90%, the 2C rate retention rate is ⁇ 71%, and the remaining capacity retention rate after high temperature storage is ⁇ 72%.
  • Example 6 it can also be known from the test results of Examples 1-9 that when the added amount of each additive is controlled at a suitable ratio, all aspects of the battery performance can be better considered.
  • Examples 1-5 and Examples 7-9 have better rate performance, because the mass ratio of cyclotriphosphazene compound and nitrile compound is controlled at 0.5:1 to 4:1 Within the range, in Example 6, because the mass ratio of the cyclotriphosphazene compound to the nitrile compound was greater than 4:1, the battery rate performance decreased.
  • Example 7 Examples 1-6 and Example 9 have better high-temperature storage performance.
  • Example 7 This is because the mass ratio of fluorocarbonate to nitrile compound is controlled in the range of 1:1 to 4:1, and In Example 7, because the mass ratio of the fluorocarbonate to the nitrile compound was greater than 4:1, the high-temperature storage performance of the battery decreased.
  • Examples 1-6 and Example 9 have better high-temperature storage performance, because the mass ratio of sulfur-containing ester compounds to nitrile compounds is controlled within the range of 0.5:1 to 3:1
  • Example 8 because the mass ratio of sulfur-containing ester compounds to nitrile compounds was less than 0.5:1, the battery produced more gas at high temperature, and the capacity retention rate decreased after high-temperature storage.
  • Examples 1-8 have more excellent flame resistance.

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Abstract

本申请实施例提供一种锂二次电池电解液，包括锂盐、非水有机溶剂和功能添加剂，所述功能添加剂包括以下在所述锂二次电池电解液中具有如下质量百分比的各组分：环三磷腈化合物3％-12％、氟代碳酸酯3％-9％、含硫的酯类化合物2％-6％、腈类化合物1％-6％。本申请实施例提供的锂二次电池电解液，含有多种功能添加剂，且各添加剂的加入量精确控制在适合范围，从而使各添加剂充分发挥协同作用，有效兼顾电池的电化学性能和安全性能，使电池综合性能处于较优水平。本申请实施例还提供了上述锂二次电池电解液的制备方法、锂二次电池和终端。

Description

锂二次电池电解液及其制备方法、锂二次电池和终端
本申请要求于2020年3月10日提交中国专利局、申请号为2020101639855、申请名称为“锂二次电池电解液及其制备方法、锂二次电池和终端”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及锂二次电池技术领域，特别是涉及锂二次电池电解液及其制备方法、锂二次电池和终端。
背景技术
随着科学技术的日新月异，3C消费类电子产品(如终端手机)对电池能量密度的要求越来越高。开发高电压正极材料可以显著提高电池能量密度，但目前常规碳酸酯类电解液体系很难维持电池在>4.40V条件下的长期循环和高温存储性能，另外随着高能量密度电池的发展，安全问题日渐突出。因此，兼具高电压循环和高安全性能电解液的开发已迫在眉睫。
发明内容
本申请实施例公开了一种锂二次电池电解液，通过加入多种功能添加剂，并精确控制各添加剂的加入量，使各添加剂充分发挥协同作用，可有效兼顾电池的电化学性能和安全性能。
本申请实施例第一方面公开了一种锂二次电池电解液，包括锂盐、非水有机溶剂和功能添加剂，所述功能添加剂包括以下在所述锂二次电池电解液中具有如下质量百分比的各组分：
环三磷腈化合物3％-12％、
氟代碳酸酯3％-9％、
含硫的酯类化合物2％-6％、
腈类化合物1％-6％。
本申请实施方式中，所述环三磷腈化合物的质量百分比为5％-10％。
本申请实施方式中，所述氟代碳酸酯的质量百分比为5％-7％。
本申请实施方式中，所述含硫的酯类化合物的质量百分比为3％-5％。
本申请实施方式中，所述腈类化合物的质量百分比为3％-5％。
本申请实施方式中，所述环三磷腈化合物与所述腈类化合物的质量比为0.5∶1至4∶1。
本申请实施方式中，所述氟代碳酸酯与所述腈类化合物的质量比为1∶1至4∶1。
本申请实施方式中，所述含硫的酯类化合物与所述腈类化合物的质量比为0.5∶1至3∶1。
本申请实施方式中，所述环三磷腈化合物的质量与所述含硫的酯类化合物和所述腈类化合物两者的质量总和之比为0.5∶1至2∶1。
本申请实施方式中，所述环三磷腈化合物的分子结构如式(Ⅰ)所示：
Figure PCTCN2021080039-appb-000001
其中，R 1、R 2、R 3、R 4、R 5、R 6可分别选自氟、氯、溴、烷基、卤代烷基、烷氧基、卤代烷氧基、烯基、卤代烯基、烯氧基、卤代烯氧基、芳基、卤代芳基、芳氧基、卤代芳氧基、取代磷酸酯基、取代磺酸基、取代酰亚胺基和取代磺酰亚胺基中的任意一种。
本申请实施方式中，所述环三磷腈化合物包括甲氧基(五氟)环三磷腈、乙氧基(五氟)环三磷腈(FPN)、苯氧基(五氟)环三磷腈(PFPN)、三氟乙氧基(五氟)环三磷腈、甲基磺酸基(五氟)环三磷腈和乙基磺酸基(五氟)环三磷腈中的一种或多种。
本申请实施方式中，所述氟代碳酸酯包括氟代碳酸乙烯酯(FEC)、二氟代碳酸乙烯酯(DFEC)、三氟甲基碳酸乙烯酯(TFEC)中的一种或多种。
本申请实施方式中，所述含硫化合物包括亚硫酸二甲酯、亚硫酸二乙酯、亚硫酸乙烯酯(ES)、硫酸乙烯酯(DTD)、甲烷二磺酸亚甲酯(MMDS)、1,3-丙磺酸内酯(PS)、1,4-丁磺酸内酯(BS)、硫酸二甲酯、硫酸二乙酯中的一种或多种。
本申请实施方式中，所述腈类化合物包括单腈和/或多腈化合物。
本申请实施方式中，所述多腈化合物包括丁二腈(SN)、戊二腈(GLN)、己二腈(ADN)、1，2-二(2-氰乙氧基)乙烷(DENE)、1，3，6-已烷三腈(HTCN)中的一种或多种。
本申请实施方式中，所述锂盐包括LiClO 4、LiBF 4、LiPF 6、LiAsF 6、LiPF 2O 2、LiCF 3SO 3、LiTDI、LiB(C 2O 4) 2(LiBOB)、LiBF 2C 2O 4(LiDFOB)、Li[(CF 3SO 2) 2N]、Li[(FSO 2) 2N]和Li[(C mF 2m+1SO 2)(C nF 2n+1SO 2)N]中的一种或多种，其中，m和n为自然数。
本申请实施方式中，所述锂盐在所述锂二次电池电解液中的摩尔浓度为0.01mol/L-2.0mol/L。
本申请实施方式中，所述非水有机溶剂包括碳酸酯类溶剂、醚类溶剂、羧酸酯类溶剂中的一种或多种。
本申请实施例第二方面提供一种锂二次电池电解液的制备方法，包括以下步骤：
在惰性环境或密闭环境中，将充分干燥的锂盐溶解于非水有机溶剂中，搅拌混合成均匀溶液，然后将功能添加剂加入到所述均匀溶液中，混合均匀后，得到锂二次电池电解液；所述功能添加剂包括以下在所述锂二次电池电解液中具有如下质量百分比的各组分：
环三磷腈化合物3％-12％、
氟代碳酸酯3％-9％、
含硫的酯类化合物2％-6％、
腈类化合物1％-6％。
本申请实施例第三方面提供一种锂二次电池，包括正极、负极、隔膜和电解液，所述 电解液采用本申请实施例第一方面所述的锂二次电池电解液。
本申请实施例还提供一种终端，包括壳体、以及收容于所述壳体内的显示模组、电子元器件模组和电池，所述电池为所述显示模组和所述电子元器件模组供电，所述电池包括本申请实施例第三方面所述的锂二次电池。
本申请实施例提供的锂二次电池电解液，通过同时加入多种功能添加剂，并将各添加剂的加入量精确控制在适合范围，可使各添加剂充分发挥协同作用，从而使电解液有效兼顾高电压循环性能、高安全性能，以及高温存储性能、倍率性能等方面性能，最终使电池综合性能处于较优水平。
附图说明
图1是本申请实施例提供的锂离子二次电池的结构示意图；
图2是本申请实施例提供的终端的结构示意图；
图3是本申请实施例1-3制备的电池的循环性能测试图。
具体实施方式
下面结合本申请实施例中的附图对本申请实施例进行描述。
如图1所示，锂离子二次电池的核心部件包括正极材料101、负极材料102、电解液103、隔膜104以及相应的连通辅件和回路。其中，正极材料101、负极材料102可以脱嵌锂离子实现能量的存储和释放，电解液103是锂离子在正负极之间传输的介质，对电池的电化学性能和安全性能起到重要的作用。电解液主要由锂盐、非水有机溶剂(常规为碳酸酯类溶剂)和添加剂组成。目前常规碳酸酯类电解液在高电压正极材料(>4.4V)的使用下，会发生不可逆的氧化分解，导致电池性能的恶化，从而很难维持电池在>4.40V条件下的长期循环和高温存储性能；另外随着高能量密度电池的发展，当电池在滥用(热冲击、过充、针刺和外部短路等)状态下因其电解液存在易挥发、易燃烧等隐患，极易引起电池热失控而导致安全问题。为解决上述问题，本申请提供一种兼具高电压和高安全性的锂二次电池电解液。
本申请实施例提供的锂二次电池电解液，包括锂盐、非水有机溶剂和功能添加剂，其中，功能添加剂包括以下在锂二次电池电解液中具有如下质量百分比的各组分：
环三磷腈化合物3％-12％、
氟代碳酸酯3％-9％、
含硫的酯类化合物2％-6％、
腈类化合物1％-6％。
本申请实施例提供的锂二次电池电解液，含有多种功能添加剂，其中环三磷腈化合物具有优异的阻燃特性，可以提升电池安全性；氟代碳酸酯具有良好的负极成膜功能，可以提升电池循环性能；含硫的酯类化合物能够抑制高温产气，改善高电压电池的高温存储性能；腈类化合物可以改善电池高电压循环性能。而各功能添加剂的加入量直接影响着各添加剂性能的发挥，同时也会影响电池其他方面性能，如电池低温性能和倍率性能等。本申请通过将各添加剂的加入量进行适合控制，其中环三磷腈化合物含量为3％-12％、氟代碳 酸酯含量为3％-9％、含硫的酯类化合物含量为2％-6％、腈类化合物含量为1％-6％，从而充分发挥多种添加剂之间的协同作用，使电池在具备优异高电压循环性能、高温存储性能和高安全性能的同时，还具备优异低温性能和倍率性能，而且电解液与正负极材料兼容性好，从而有效兼顾了电池的电化学性能和安全性能，使电池综合性能处于较优水平。
具体地，本申请一些实施方式中，环三磷腈化合物的质量百分比为5％-10％。
本申请一些实施方式中，氟代碳酸酯的质量百分比为5％-7％。
本申请一些实施方式中，含硫的酯类化合物的质量百分比为3％-5％。
本申请一些实施方式中，腈类化合物的质量百分比为3％-5％。
本申请实施方式中，为了使各种添加剂更好地发挥协同作用，保证电解液在满足高电压工作需求和高安全性的同时，使电池其它性能处于更优水平，还可以进一步精确调控多种添加剂之间的添加比例。
具体地，本申请实施方式中，环三磷腈化合物与腈类化合物的质量比可以是0.5∶1至4∶1。通过将环三磷腈化合物与腈类化合物的质量比控制在0.5∶1至4∶1，可以有效兼顾电池高电压循环性能、安全性能、低温性能、倍率性能之间的平衡。若比例太小，不利于电池获得高安全性能；比例太大，不利于电池获得高电压循环、低温、倍率等性能。本申请实施方式中，环三磷腈化合物与腈类化合物的质量比也可以是1∶1至3∶1，还可以是1.5∶1至2.5∶1。
本申请实施方式中，氟代碳酸酯与腈类化合物的质量比可以是1∶1至4∶1。将氟代碳酸酯与腈类化合物质量比控制在1∶1至4∶1，可以有效兼顾电解液正极成膜性能和负极成膜性能之间的平衡。若比例太小，氟代碳酸酯不能很好地形成有效稳定SEI膜应对腈类化合物对负极产生的副反应；若比例太大，会因氟代碳酸酯在高电压和高温条件下的产气，不利于获得高温存储性能和高电压循环性能。本申请实施方式中，氟代碳酸酯与腈类化合物的质量比也可以是1.25∶1至3.5∶1，还可以是2∶1至3∶1。
本申请实施方式中，含硫的酯类化合物与腈类化合物的质量比可以是0.5∶1至3∶1。将含硫的酯类化合物与腈类化合物质量比控制在0.5∶1至3∶1，可以有效兼顾高温存储性能和高电压循环性能。若比例太小，不能很好地通过含硫的酯类化合物抑制高温产气，不利于高温存储性能的提高；若比例太大，电池阻抗太大，会影响电池循环性能、倍率性能、低温性能。本申请实施方式中，含硫的酯类化合物与腈类化合物的质量比也可以是0.75∶1至2.5∶1，还可以是1∶1至2∶1。
本申请实施方式中，环三磷腈化合物的质量与含硫的酯类化合物和腈类化合物两者的质量总和之比可以是0.5∶1至2∶1。将环三磷腈化合物质量与含硫的酯类化合物和腈类化合物的质量总和之比控制在0.5∶1至2∶1，可以有效兼顾电解液电导率和极片浸润性之间的平衡，若比例太小，会较大影响电池安全和极片浸润性；若比例太大，会影响电池低温和倍率性能。
本申请实施方式中，环三磷腈化合物是一类具有稳定的六元杂环、共轭结构的磷腈类化合物，其六元杂环由三个氮原子和三个磷原子以磷-氮单双键连接构成，环三磷腈化合物可以是六氯环三磷腈，也可以是六氯环三磷腈衍生物。具体地，环三磷腈化合物分子结构可以是如式(Ⅰ)所示：
Figure PCTCN2021080039-appb-000002
其中，R 1、R 2、R 3、R 4、R 5、R 6可分别选自氟、氯、溴、烷基、卤代烷基、烷氧基、卤代烷氧基、烯基、卤代烯基、烯氧基、卤代烯氧基、芳基、卤代芳基、芳氧基、卤代芳氧基、取代磷酸酯基、取代磺酸基、取代酰亚胺基和取代磺酰亚胺基中的任意一种。
其中，取代磺酸基表示为-O-S(＝O) 2-R，R选自氟、氯、溴、烷基、卤代烷基、烷氧基、卤代烷氧基、烯基、卤代烯基、烯氧基、卤代烯氧基、芳基、卤代芳基、芳氧基、卤代芳氧基、取代磷酸酯基、取代酰亚胺基和取代磺酰亚胺基中的任意一种，取代磺酸基通过氧原子与六元环结构中的磷原子形成P-O键化学键合。
本发明实施方式中，取代酰亚胺基可表示为-NH-C(＝O)-X，其中取代基团X可选自烷基、卤代烷基、烷氧基、卤代烷氧基、烯基、卤代烯基、烯氧基、卤代烯氧基、芳基、卤代芳基、芳氧基、卤代芳氧基中的任意一种；取代磺酰亚胺基可表示为-NH-S(＝O) 2-Y,其中取代基团Y可选自烷基、卤代烷基、烷氧基、卤代烷氧基、烯基、卤代烯基、烯氧基、卤代烯氧基、芳基、卤代芳基、芳氧基、卤代芳氧基中的任意一种。取代磺酸基、取代酰亚胺基和取代磺酰亚胺基中的含有卤素的取代基团，其卤素可以是氟、氯、溴、碘，卤代可以是全卤代，也可以是部分卤代。烷基、卤代烷基、烷氧基、卤代烷氧基、烯基、卤代烯基、烯氧基、卤代烯氧基可以是直链的也可以是支链的。
其中，当R 1、R 2、R 3、R 4、R 5、R 6均为氯时，式(Ⅰ)为六氯环三磷腈。当R 1、R 2、R 3、R 4、R 5、R 6中至少一个为非氯原子的其他基团时，式(Ⅰ)为六氯环三磷腈衍生物。
本申请一些具体实施方式中，环三磷腈化合物具体可以是甲氧基(五氟)环三磷腈、乙氧基(五氟)环三磷腈(FPN)、苯氧基(五氟)环三磷腈(PFPN)、三氟乙氧基(五氟)环三磷腈、甲基磺酸基(五氟)环三磷腈和乙基磺酸基(五氟)环三磷腈中的一种或多种。
本申请实施方式中，电解液中可以包含一种或多种环三磷腈化合物。
本申请实施方式中，氟代碳酸酯可以是含氟基团取代的碳酸乙烯酯，含氟基团可以是氟原子也可以是含氟烃基。具体地，氟代碳酸酯可包括氟代碳酸乙烯酯(FEC)、二氟代碳酸乙烯酯(DFEC)、三氟甲基碳酸乙烯酯(TFEC)中的一种或多种。
本申请实施方式中，含硫的酯类化合物可以是硫酸酯类化合物、亚硫酸酯类化合物、磺酸酯类化合物。本申请一些具体实施方式中，含硫的酯类化合物可以是亚硫酸二甲酯、亚硫酸二乙酯、亚硫酸乙烯酯(ES)、硫酸乙烯酯(DTD)、甲烷二磺酸亚甲酯(MMDS)、1,3-丙磺酸内酯(PS)、1,4-丁磺酸内酯(BS)、硫酸二甲酯、硫酸二乙酯中的一种或多种。
本申请实施方式中，腈类化合物包括单腈和/或多腈化合物。单腈化合物为分子结构中包含一个氰基的腈类化合物，而多腈化合物为分子结构中包含多个氰基(例如两个或三个)的腈类化合物。本申请一些具体实施方式中，多腈化合物可以是丁二腈(SN)、戊二腈(GLN)、 己二腈(ADN)、1，2-二(2-氰乙氧基)乙烷(DENE)、1，3，6-已烷三腈(HTCN)中的一种或多种。
本申请一些实施方式中，功能添加剂仅包括环三磷腈化合物、氟代碳酸酯、含硫的酯类化合物和腈类化合物。本申请另一些实施方式中，功能添加剂也可以根据实际需要添加其他类的物质。
本申请实施方式中，锂盐包括LiClO 4、LiBF 4、LiPF 6、LiAsF 6、LiPF 2O 2、LiCF 3SO 3、LiTDI、LiB(C 2O 4) 2(LiBOB)、LiBF 2C 2O 4(LiDFOB)、Li[(CF 3SO 2) 2N]、Li[(FSO 2) 2N]和Li[(C mF 2m+1SO 2)(C nF 2n+1SO 2)N]中的一种或多种，其中，m和n为自然数。
本申请实施方式中，锂盐在锂二次电池电解液中的摩尔浓度为0.01mol/L-2.0mol/L。进一步地，可以是0.05mol/L-1.5mol/L、0.5mol/L-1.0mol/L。
本申请实施方式中，非水有机溶剂包括碳酸酯类溶剂、醚类溶剂、羧酸酯类溶剂中的一种或多种。非水有机溶剂可以按照任意比例混合。其中，碳酸酯类溶剂包括环状碳酸酯或链状碳酸酯，环状碳酸酯具体可以是碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、γ-丁内酯(GBL)、碳酸亚丁酯(BC)中的一种或多种；链状碳酸酯具体可以是碳酸二甲酯(DMC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)中的一种或多种。醚类溶剂包括环状醚或链状醚，环状醚具体可以是1,3-二氧戊烷(DOL)、1,4-二氧惡烷(DX)、冠醚、四氢呋喃(THF)、2-甲基四氢呋喃(2-CH 3-THF)，2-三氟甲基四氢呋喃(2-CF 3-THF)中的一种或多种；所述链状醚具体可以是二甲氧基甲烷(DMM)、1,2-二甲氧基乙烷(DME)、二甘醇二甲醚(TEGDME)中的一种或多种。羧酸酯类溶剂具体可以是乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(EP)、乙酸丁酯、丙酸丙酯(PP)、丙酸丁酯中的一种或多种。
本申请实施例提供的锂二次电池电解液，含有多种功能添加剂，且各添加剂的加入量精确控制在适合范围，从而使各添加剂能充分发挥协同作用，有效兼顾电池的电化学性能和安全性能，使电池综合性能处于较优水平；另外，本申请实施例提供的锂二次电池电解液通过进一步调控各添加剂之间的质量比可以更好地兼顾各方面性能。
相应地，本申请实施例还提供上述锂二次电池电解液的制备方法，包括以下步骤：
在惰性环境或密闭环境(如填充氩气的手套箱)中，将充分干燥的锂盐溶解于非水有机溶剂中，搅拌混合成均匀溶液，然后将功能添加剂加入到所述均匀溶液中，混合均匀后，得到锂二次电池电解液；其中，功能添加剂包括以下在锂二次电池电解液中具有如下质量百分比的各组分：
环三磷腈化合物3％-12％、
氟代碳酸酯3％-9％、
含硫的酯类化合物2％-6％、
腈类化合物1％-6％。
上述制备方法中的各操作可根据现有常规电解液制备工艺实施，其中，关于锂盐、非水有机溶剂、功能添加剂等原料的具体选择如前文所述，此处不再赘述。
本申请实施例还提供一种锂二次电池，包括正极、负极、隔膜和电解液，其中，电解液采用本申请实施例上述提供的锂二次电池电解液。本申请实施例提供的锂二次电池，由于其电解液中加入了多种功能添加剂，且各添加剂的加入量精确调控在适合范围，因此具 有优异的高电压循环性能、高安全性、优异低温性能和倍率性能。本申请实施方式中，电池可以是锂离子电池。本申请实施例提供的电池，可用于终端消费产品，如手机、平板电脑、移动电源、便携机、笔记本电脑以及其它可穿戴或可移动的电子设备、以及汽车等产品，以提高产品安全可靠性。
本申请实施方式中，正极包括能够可逆地嵌入/脱嵌锂离子的正极活性材料，本申请对正极活性材料的选择无特殊限定，可为现有锂二次电池常规使用的正极活性材料，可选地，正极活性材料可以是钴酸锂(LiCoO 2)、磷酸铁锂(LiFePO 4)、镍钴锰酸锂(LiNi 0.6Co 0.2Mn 0.2)、聚阴离子锂化合物LiM x(PO 4) y(M为Ni、Co、Mn、Fe、Ti、V、0≤x≤5、0≤y≤5)等。
本申请实施方式中，负极包括能够接受或释放锂离子的负极活性材料，本申请对负极活性材料的选择无特殊限定，可为现有锂二次电池常规使用的负极活性材料，可选地，负极活性材料可以是金属锂、锂合金、钛酸锂、天然石墨、人造石墨、中间相碳微球石墨、无定型碳、碳纤维、碳纳米管、硬碳、软碳、石墨烯、氧化石墨烯、硅、硅碳、硅氧化合物、硅金属化合物、钛酸锂(Li 4Ti 5O 12)中的一种或多种。
本申请实施方式中，隔膜可为现有常规隔膜，包括但不限于单层PP(聚丙烯)、单层PE(聚乙烯)、双层PP/PE、双层PP/PP和三层PP/PE/PP等隔膜。
如图2所示，本申请实施例还提供一种终端，该终端200可以是手机、也可以是平板电脑、笔记本电脑、便携机、智能穿戴产品、汽车等产品，包括壳体201、以及收容于壳体201内的电子元器件和电池(图中未示出)，电池为电子元器件供电，其中，电池为本申请实施例上述提供的锂二次电池，壳体201可包括组装在终端前侧的前盖和组装在后侧的后壳，电池可固定在后壳内侧。
下面通过具体实施例对本申请实施例进行进一步的说明。
实施例1
在填充氩气的手套箱中，将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)、碳酸丙烯酯(PC)和丙酸丙酯(PP)混合形成有机溶剂，再将充分干燥的六氟磷酸锂(LiPF 6)和二氟硼酸锂(LiDFOB)溶解于上述溶剂中，搅拌混合成均匀溶液，然后将乙氧基(五氟)环三磷腈(FPN)、氟代碳酸乙烯酯(FEC)、1,3-丙磺酸内酯(PS)、丁二腈(SN)和己二腈(ADN)分别加入上述溶液中，混合均匀制得锂二次电池电解液。其中，LiPF 6的浓度为1.0摩尔/升，LiDFOB的浓度为0.05摩尔/升，EC、DEC、PC和PP的质量百分数分别为25:25:10:40，FPN、FEC、PS、SN和ADN的质量百分数分别为5％、5％、3％、2％和2％。
锂二次电池的制作
称取质量百分含量为2％聚偏氟乙烯(PVDF)、2％导电剂super P和96％钴酸锂(LiCoO2)，依次加入到N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀，将浆料涂布在铝箔集流体上，烘干、冷压、分切制得正极极片；
称取质量百分含量为1.5％CMC、2.5％SBR、1％乙炔黑和95％石墨，依次加入到去离子水中，充分搅拌混合均匀，将浆料涂布在铜箔集流体上，烘干、冷压、分切制得负极极片；
将上述制备的正极极片、负极极片和商用PE隔膜制成电芯，采用聚合物包装，灌注上 述实施例1制备的锂二次电池电解液，经化成等工艺后制成4Ah的软包锂二次电池。
实施例2
在填充氩气的手套箱中，将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)、碳酸丙烯酯(PC)和丙酸丙酯(PP)混合形成有机溶剂，再将充分干燥的六氟磷酸锂(LiPF6)和二氟硼酸锂(LiDFOB)溶解于上述溶剂中，搅拌混合成均匀溶液，然后将乙氧基(五氟)环三磷腈(FPN)、氟代碳酸乙烯酯(FEC)、1,3-丙磺酸内酯(PS)、丁二腈(SN)、己二腈(ADN)和1，2-二(2-氰乙氧基)乙烷(DENE)分别加入上述溶液，混合均匀制得锂二次电池电解液。其中，LiPF6的浓度为1.0摩尔/升，LiDFOB的浓度为0.05摩尔/升，EC、DEC、PC和PP的质量百分数分别为25:25:10:40，FPN、FEC、PS、SN、AND和DENE的质量百分数分别为6％、5％、3％、2％、1％和1％。
采用实施例2制备的锂二次电池电解液制备锂二次电池，制备方法同实施例1。
实施例3
在填充氩气的手套箱中，将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)、碳酸丙烯酯(PC)和丙酸丙酯(PP)混合形成有机溶剂，再将充分干燥的六氟磷酸锂(LiPF 6)溶解于上述溶剂中，搅拌混合成均匀溶液，然后将乙氧基(五氟)环三磷腈(FPN)、氟代碳酸乙烯酯(FEC)、1,3-丙磺酸内酯(PS)、丁二腈(SN)、己二腈(ADN)和1，2-二(2-氰乙氧基)乙烷(DENE)分别加入上述溶液，混合均匀制得本申请实施例3的电解液。其中，LiPF 6的浓度为1.05摩尔/升，EC、DEC、PC和PP的质量百分数分别为25:25:10:40，FPN、FEC、PS、SN、AND和DENE的质量百分数分别为7％、5％、3％、1％、2％和1％。
采用实施例3制备的锂二次电池电解液制备锂二次电池，制备方法同实施例1。
实施例4
在填充氩气的手套箱中，将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)、碳酸丙烯酯(PC)和丙酸丙酯(PP)混合形成有机溶剂，再将充分干燥的六氟磷酸锂(LiPF 6)溶解于上述溶剂中，搅拌混合成均匀溶液，然后将苯氧基(五氟)环三磷腈(PFPN)、氟代碳酸乙烯酯(FEC)、1,3-丙磺酸内酯(PS)、丁二腈(SN)、己二腈(ADN)和1，3，6-已烷三腈(HTCN)分别加入上述溶液，混合均匀制得本申请实施例4的电解液。其中，LiPF 6的浓度为1.05摩尔/升，EC、DEC、PC和PP的质量百分数分别为25:25:10:40，PFPN、FEC、PS、SN、AND和HTCN的质量百分数分别为10％、7％、5％、1％、2％和1％。
采用实施例4制备的锂二次电池电解液制备锂二次电池，制备方法同实施例1。
实施例5
在填充氩气的手套箱中，将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)、碳酸丙烯酯(PC)和丙酸丙酯(PP)混合形成有机溶剂，再将充分干燥的六氟磷酸锂(LiPF 6)溶解于上述溶剂中，搅拌混合成均匀溶液，然后将乙氧基(五氟)环三磷腈(FPN)、氟代碳酸乙烯酯(FEC)、硫酸乙烯酯(DTD)、丁二腈(SN)和1，3，6-已烷三腈(HTCN)分别加入上述溶液，混合均匀制得本申请实施例5的电解液。其中，LiPF 6的浓度为1.05摩尔/升，EC、DEC、PC和PP的质量百分数分别为25:25:10:40，FPN、FEC、DTD、SN和HTCN的质量百分数分别为10％、7％、3％、2％和1％。
采用实施例5制备的锂二次电池电解液制备锂二次电池，制备方法同实施例1。
实施例6
在填充氩气的手套箱中，将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)、碳酸丙烯酯(PC)和丙酸丙酯(PP)混合形成有机溶剂，再将充分干燥的六氟磷酸锂(LiPF 6)溶解于上述溶剂中，搅拌混合成均匀溶液，然后将乙氧基(五氟)环三磷腈(FPN)、氟代碳酸乙烯酯(FEC)、1,3-丙磺酸内酯(PS)和己二腈(ADN)分别加入上述溶液，混合均匀制得本申请实施例6的电解液。其中，LiPF 6的浓度为1.05摩尔/升，EC、DEC、PC和PP的质量百分数分别为25:25:10:40，FPN、FEC、PS和AND的质量百分数分别为12％、7％、5％和2％。
采用实施例6制备的锂二次电池电解液制备锂二次电池，制备方法同实施例1。
实施例7
在填充氩气的手套箱中，将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)、碳酸丙烯酯(PC)和丙酸丙酯(PP)混合形成有机溶剂，再将充分干燥的六氟磷酸锂(LiPF 6)溶解于上述溶剂中，搅拌混合成均匀溶液，然后将乙氧基(五氟)环三磷腈(FPN)、氟代碳酸乙烯酯(FEC)、1,3-丙磺酸内酯(PS)和己二腈(ADN)分别加入上述溶液，混合均匀制得本申请实施例7的电解液。其中，LiPF 6的浓度为1.05摩尔/升，EC、DEC、PC和PP的质量百分数分别为25:25:10:40，FPN、FEC、PS和AND的质量百分数分别为8％、9％、3％和2％。
采用实施例7制备的锂二次电池电解液制备锂二次电池，制备方法同实施例1。
实施例8
在填充氩气的手套箱中，将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)、碳酸丙烯酯(PC)和丙酸丙酯(PP)混合形成有机溶剂，再将充分干燥的六氟磷酸锂(LiPF 6)溶解于上述溶剂中，搅拌混合成均匀溶液，然后将乙氧基(五氟)环三磷腈(FPN)、氟代碳酸乙烯酯(FEC)、1,3-丙磺酸内酯(PS)、己二腈(ADN)和1，3，6-已烷三腈(HTCN)分别加入上述溶液，混合均匀制得本申请实施例8的电解液。其中，LiPF 6的浓度为1.05摩尔/升，EC、DEC、PC和PP的质量百分数分别为25:25:10:40，FPN、FEC、PS、AND和HTCN的质量百分数分别为8％、7％、2％、3％和2％。
采用实施例8制备的锂二次电池电解液制备锂二次电池，制备方法同实施例1。
实施例9
在填充氩气的手套箱中，将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)、碳酸丙烯酯(PC)和丙酸丙酯(PP)混合形成有机溶剂，再将充分干燥的六氟磷酸锂(LiPF 6)溶解于上述溶剂中，搅拌混合成均匀溶液，然后将乙氧基(五氟)环三磷腈(FPN)、氟代碳酸乙烯酯(FEC)、1,3-丙磺酸内酯(PS)、己二腈(ADN)和1，3，6-已烷三腈(HTCN)分别加入上述溶液，混合均匀制得本申请实施例9的电解液。其中，LiPF 6的浓度为1.05摩尔/升，EC、DEC、PC和PP的质量百分数分别为25:25:10:40，FPN、FEC、PS、AND和HTCN的质量百分数分别为3％、7％、3％、2％和2％。
采用实施例9制备的锂二次电池电解液制备锂二次电池，制备方法同实施例1。
1、电解液性能测试
1.1、电导率测试
采用电导率仪测试电解液的电导率，取1-5mL的电解液样品置于电导率仪的测试管中，测试温度为25℃，每种电解液样品的电导率测试3次并取其平均值。相关测试数据见表1。
1.2、自熄性能测试
取1.0克电解液置于5.0毫升的坩埚中，点燃测试其自熄时间。用点火装置迅速点燃，记录点燃时间，并记录点火装置移开后至火焰自动熄灭的时间，即为自熄时间(SET)。每种电解液样品的SET测试5次并取其平均值。以单位质量电解液的自熄时间为标准，比较不同阻燃电解液的阻燃性能。
2、锂二次电池性能测试
2.1、循环性能测试
在环境温度25℃±3℃的条件下，以1.0/1.0C充放电倍率对电池进行充放电循环测试，石墨/LiCoO 2电池的电压范围为3.0-4.5V，记录100周的容量保持率。
2.2、倍率性能测试
在环境温度25℃±3℃的条件下，以0.2/0.2C、0.2/0.5C、0.2/1.0C、0.2/1.5C和0.2/2.0C充放电倍率对锂二次电池进行倍率性能测试，石墨/LiCoO 2电池的电压范围为3.0-4.5V，记录2C倍率保持率(2C放电容量/0.2C放电容量*100％)。
2.3、高温存储性能测试
在环境温度25℃±3℃的条件下，电池按照0.2C/0.2C充放电1次，此次的容量为初始容量；电池再次按照0.2C充满电，充电后的电池在70℃温度条件下搁置24小时，然后在室温状态下开路搁置2h，以0.2C恒流放电至终止电压，记为剩余容量，石墨/LiCoO 2电池的电压范围为3.0-4.5V，记录剩余容量保持率(剩余容量/初始容量*100％)。
实施例1-9的测试结果列于表1，实施例1-3的循环测试结果列于图3。
表1实施例1-9的测试数据
Figure PCTCN2021080039-appb-000003
从表1和图3可以看出，本申请实施例1-9的电解液兼具一定的耐燃性、高电压循环性能、倍率性能和高温存储性能，这是由于本申请实施例1-9的电解液同时加入了适合量的环三磷腈化合物、氟代碳酸酯、含硫的酯类化合物和腈类化合物四种功能添加剂。其中，环三磷腈化合物在电解液受热情况下，其磷腈基团会分解产生P系自由基捕获电解液受热分解产生的H或OH自由基，切断链式反应，从而可提高电解液的耐燃性；氟代碳酸酯具 有良好的负极成膜功能，可以提升电池循环性能；含硫的酯类化合物能够抑制高温产气，改善高电压电池的高温存储性能；腈类化合物可以改善电池高电压循环性能。本申请实施例1-9通过将各添加剂含量控制在适合范围可以充分发挥多种添加剂之间的协同作用，使电池性能得到充分发挥，兼顾电池电化学性能和安全性能，其中电解液点燃时间≥3s，自熄时间≤23s，电池循环100周后容量保持率在90％以上，2C倍率保持率≥71％，高温存储后剩余容量保持率≥72％。
另外，从实施例1-9的测试结果也可以获知，当各添加剂的加入量控制在适合配比，可以更好地兼顾电池的各方面性能。其中，相比实施例6，实施例1-5和实施例7-9具有更优的倍率性能，这是由于环三磷腈化合物与腈类化合物的质量比控制在0.5:1至4:1范围内，而实施例6中由于环三磷腈化合物与腈类化合物的质量比>4:1，电池倍率性能有所下降。相比实施例7，实施例1-6和实施例9具有更优的高温存储性能，这是由于氟代碳酸酯与腈类化合物的质量比控制在1:1至4:1范围内，而实施例7中由于氟代碳酸酯与腈类化合物的质量比>4:1，电池高温存储性能有所下降。相比实施例8，实施例1-6和实施例9具有更优的高温存储性能，这是由于含硫的酯类化合物与腈类化合物的质量比控制在0.5:1至3:1范围内，而实施例8中由于含硫的酯类化合物与腈类化合物的质量比＜0.5:1，电池高温产气更多，高温存储后容量保持率有所下降。相比实施例9，实施例1-8具有更优异的耐燃性，这是由于环三磷腈化合物与与含硫的酯类化合物和腈类化合物两者的质量总和之比控制在0.5:1至2:1范围内，而实施例9中由于环三磷腈化合物与与含硫的酯类化合物和腈类化合物两者的质量总和之比<0.5:1，电解液点燃时间有所下降。

Claims (21)

  1. 一种锂二次电池电解液，其特征在于，包括锂盐、非水有机溶剂和功能添加剂，所述功能添加剂包括以下在所述锂二次电池电解液中具有如下质量百分比的各组分：
    环三磷腈化合物3％-12％、
    氟代碳酸酯3％-9％、
    含硫的酯类化合物2％-6％、
    腈类化合物1％-6％。
  2. 如权利要求1所述的锂二次电池电解液，其特征在于，所述环三磷腈化合物的质量百分比为5％-10％。
  3. 如权利要求1或2所述的锂二次电池电解液，其特征在于，所述氟代碳酸酯的质量百分比为5％-7％。
  4. 如权利要求1-3任一项所述的锂二次电池电解液，其特征在于，所述含硫的酯类化合物的质量百分比为3％-5％。
  5. 如权利要求1-4任一项所述的锂二次电池电解液，其特征在于，所述腈类化合物的质量百分比为3％-5％。
  6. 如权利要求1-5任一项所述的锂二次电池电解液，其特征在于，所述环三磷腈化合物与所述腈类化合物的质量比为0.5∶1至4∶1。
  7. 如权利要求1-6任一项所述的锂二次电池电解液，其特征在于，所述氟代碳酸酯与所述腈类化合物的质量比为1∶1至4∶1。
  8. 如权利要求1-7任一项所述的锂二次电池电解液，其特征在于，所述含硫的酯类化合物与所述腈类化合物的质量比为0.5∶1至3∶1。
  9. 如权利要求1-8任一项所述的锂二次电池电解液，其特征在于，所述环三磷腈化合物的质量与所述含硫的酯类化合物和所述腈类化合物两者的质量总和之比为0.5∶1至2∶1。
  10. 如权利要求1-9任一项所述的锂二次电池电解液，其特征在于，所述环三磷腈化合物的分子结构如式(Ⅰ)所示：
    Figure PCTCN2021080039-appb-100001
    其中，R 1、R 2、R 3、R 4、R 5、R 6可分别选自氟、氯、溴、烷基、卤代烷基、烷氧基、卤代烷氧基、烯基、卤代烯基、烯氧基、卤代烯氧基、芳基、卤代芳基、芳氧基、卤代芳氧基、取代磷酸酯基、取代磺酸基、取代酰亚胺基和取代磺酰亚胺基中的任意一种。
  11. 如权利要求10所述的锂二次电池电解液，其特征在于，所述环三磷腈化合物包括甲氧基(五氟)环三磷腈、乙氧基(五氟)环三磷腈、苯氧基(五氟)环三磷腈、三氟乙 氧基(五氟)环三磷腈、甲基磺酸基(五氟)环三磷腈和乙基磺酸基(五氟)环三磷腈中的一种或多种。
  12. 如权利要求1-11任一项所述的锂二次电池电解液，其特征在于，所述氟代碳酸酯包括氟代碳酸乙烯酯、二氟代碳酸乙烯酯、三氟甲基碳酸乙烯酯中的一种或多种。
  13. 如权利要求1-12任一项所述的锂二次电池电解液，其特征在于，所述含硫的酯类化合物包括亚硫酸二甲酯、亚硫酸二乙酯、亚硫酸乙烯酯、硫酸乙烯酯、甲烷二磺酸亚甲酯、1,3-丙磺酸内酯、1,4-丁磺酸内酯、硫酸二甲酯、硫酸二乙酯中的一种或多种。
  14. 如权利要求1-13任一项所述的锂二次电池电解液，其特征在于，所述腈类化合物包括单腈化合物和/或多腈化合物。
  15. 如权利要求14所述的锂二次电池电解液，其特征在于，所述多腈化合物包括丁二腈、戊二腈、己二腈、1，2-二(2-氰乙氧基)乙烷、1，3，6-已烷三腈中的一种或多种。
  16. 如权利要求1-15任一项所述的锂二次电池电解液，其特征在于，所述锂盐包括LiClO 4、LiBF 4、LiPF 6、LiAsF 6、LiPF 2O 2、LiCF 3SO 3、LiTDI、LiB(C 2O 4) 2、LiBF 2C 2O 4、Li[(CF 3SO 2) 2N]、Li[(FSO 2) 2N]和Li[(C mF 2m+1SO 2)(C nF 2n+1SO 2)N]中的一种或多种，其中，m和n为自然数。
  17. 如权利要求1-16任一项所述的锂二次电池电解液，其特征在于，所述锂盐在所述锂二次电池电解液中的摩尔浓度为0.01mol/L-2.0mol/L。
  18. 如权利要求1-17任一项所述的锂二次电池电解液，其特征在于，所述非水有机溶剂包括碳酸酯类溶剂、醚类溶剂、羧酸酯类溶剂中的一种或多种。
  19. 一种锂二次电池电解液的制备方法，其特征在于，包括以下步骤：
    在惰性环境或密闭环境中，将充分干燥的锂盐溶解于非水有机溶剂中，搅拌混合成均匀溶液，然后将功能添加剂加入到所述均匀溶液中，混合均匀后，得到锂二次电池电解液；所述功能添加剂包括以下在所述锂二次电池电解液中具有如下质量百分比的各组分：
    环三磷腈化合物3％-12％、
    氟代碳酸酯3％-9％、
    含硫的酯类化合物2％-6％、
    腈类化合物1％-6％。
  20. 一种锂二次电池，其特征在于，包括正极、负极、隔膜和电解液，所述电解液采用如权利要求1-18任一项所述的锂二次电池电解液。
  21. 一种终端，其特征在于，包括壳体、以及收容于所述壳体内的电子元器件和电池，所述电池为所述电子元器件供电，所述电池包括权利要求20所述的锂二次电池。
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