WO2018120793A1 - 电解液及二次电池 - Google Patents

电解液及二次电池 Download PDF

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Publication number
WO2018120793A1
WO2018120793A1 PCT/CN2017/093863 CN2017093863W WO2018120793A1 WO 2018120793 A1 WO2018120793 A1 WO 2018120793A1 CN 2017093863 W CN2017093863 W CN 2017093863W WO 2018120793 A1 WO2018120793 A1 WO 2018120793A1
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group
carbon atoms
electrolyte
compound
secondary battery
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PCT/CN2017/093863
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English (en)
French (fr)
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王小梅
付成华
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宁德时代新能源科技股份有限公司
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Publication of WO2018120793A1 publication Critical patent/WO2018120793A1/zh

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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
    • 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
    • H01M10/0569—Liquid materials characterised by the solvents
    • 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

  • the present invention relates to the field of battery technologies, and in particular, to an electrolyte and a secondary battery.
  • a widely used electrolyte for a lithium ion secondary battery includes lithium hexafluorophosphate as a conductive lithium salt and a mixture of a cyclic carbonate and a chain carbonate.
  • the above electrolyte still has many disadvantages, particularly at a high temperature. Under the voltage, the performance of the lithium ion secondary battery is poor, such as poor high temperature cycle performance, poor high temperature storage performance, poor safety performance, and poor rate performance.
  • an object of the present invention is to provide an electrolyte and a secondary battery, which can simultaneously improve the rate performance and high-temperature storage performance of the secondary battery when the electrolyte is applied to the secondary battery. High temperature cycle performance and overcharge safety.
  • the present invention provides an electrolyte comprising an electrolyte salt, an organic solvent, and an additive.
  • the organic solvent includes a carboxylate compound.
  • the additive includes a dinitrile compound, an aromatic compound overcharge additive, and a cyclic sulfate and/or a cyclic sulfonate.
  • the invention provides a secondary battery comprising an electrolyte according to an aspect of the invention.
  • the electrolytic solution of the present invention includes a carboxylate compound, a dinitrile compound, an aromatic compound overcharge additive, and a cyclic sulfate ester and/or a cyclic sulfonate, which are applied to a secondary battery after the application thereof Synergistically, it can simultaneously improve the rate performance, high temperature storage performance, high temperature cycle performance and overcharge safety performance of the secondary battery.
  • the electrolytic solution according to the first aspect of the invention includes an electrolyte salt, an organic solvent, and an additive.
  • the organic solvent includes a carboxylate compound.
  • the additive includes a dinitrile compound, an aromatic compound overcharge additive, and a cyclic sulfate and/or a cyclic sulfonate.
  • the carboxylate compound is used for improving the rate performance of the secondary battery, but when the carboxylate compound is applied to a secondary battery of a high voltage system, it is easily oxidized.
  • the secondary battery using the carboxylic acid ester compound is decomposed and used in a high-temperature environment, the capacity loss after repeated cycles of the secondary battery is severe, and the high-temperature storage performance of the secondary battery is seriously deteriorated.
  • the dinitrile compound can be complexed with the positive electrode of the secondary battery, and the side reaction at the time of reducing the high temperature also reduces the kinetic performance of the secondary battery, and the dinitrile compound is easy to be in the negative electrode due to its strong electron absorption characteristics.
  • the electron reduction reaction is obtained, and the product obtained by the reduction is unstable and can be deposited on the negative electrode, thereby affecting the high temperature cycle performance and the rate performance of the secondary battery.
  • the cyclic sulfate and/or cyclic sulfonate has a high reduction potential, and can preferentially form a film on the surface of the negative electrode to inhibit the reduction of the carboxylate compound, thereby improving the high-temperature cycle performance of the secondary battery, but when the content thereof is higher than
  • the aromatic compound overcharge additive can improve the overcharge safety performance of the secondary battery, but when the content thereof increases, the viscosity of the electrolyte increases and deteriorates.
  • the dynamic performance of the secondary battery When the above substances are simultaneously included in the electrolyte, under the synergistic action of the above substances, the rate performance, high temperature storage performance, high temperature cycle performance, and overcharge safety performance of the secondary battery can be simultaneously
  • the carboxylic acid ester compound is selected from one or more of the compounds represented by Formula 1.
  • R 1 and R 2 are each independently selected from the group consisting of an alkane group having 1 to 10 carbon atoms and a halogenated alkane group having 1 to 10 carbon atoms.
  • the halogen atom in the halogenated alkane group is one or more selected from the group consisting of F, Cl, Br, and I.
  • the alkane group having 1 to 10 carbon atoms may be a chain alkane group or a cyclic alkane group.
  • the chain alkane group further includes a linear alkane group and a branched alkane group.
  • the cyclic alkane group may have a substituent or may not contain a substituent.
  • a preferred lower limit of the number of carbon atoms may be 1, 2, and 3, and a preferred upper limit of the number of carbon atoms may be 4, 5, 6, 7, 8, 9, or 10.
  • R 1 and R 2 are each independently selected from a chain alkane group having 1 to 6 carbon atoms or a cyclic alkane group having 3 to 8 carbon atoms. Still more preferably, R 1 and R 2 are each independently selected from a chain alkane group having 1 to 4 carbon atoms or a cyclic alkane group having 5 to 7 carbon atoms.
  • the alkane group having 1 to 10 carbon atoms may be selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, Cyclobutyl, n-pentyl, isopentyl, tert-amyl, neopentyl, cyclopentyl, 2,2 dimethylpropyl, 1-ethylpropyl, 1-methylbutyl, 2-methyl Butyl, n-hexyl, isohexyl, 2-hexyl, 3-hexyl, cyclohexyl, 2-methylpentyl, 3-methylpentyl, 1,1,2-trimethylpropyl, 3,3 - dimethylbutyl, n-heptyl, 2-heptyl, 3-heptyl, 2-methylhexyl, 3-methylhexyl,
  • the number of substitution of the halogen atom in the halogenated alkane group having 1 to 10 carbon atoms and the position of substitution thereof are not particularly limited, and may be selected according to actual needs.
  • the number of halogen atoms may be one, two, three or four.
  • the types of the halogen atoms may be the same, or they may be completely different or partially the same.
  • the haloalkane group may be a chain haloalkane group or a cyclic haloalkane group.
  • the chain haloalkane group in turn includes a linear haloalkane group and a branched haloalkane group.
  • the cyclic haloalkane group may or may not have a substituent.
  • a preferred lower limit of the number of carbon atoms may be 1, 2, and 3, and a preferred upper limit of the number of carbon atoms may be 4, 5, 6, 7, 8, 9, or 10.
  • R 1 and R 2 are each independently selected from a chain halogenated alkane group having 1 to 6 carbon atoms or a cyclic halogenated alkane group having 3 to 8 carbon atoms. Still more preferably, each of R 1 and R 2 is independently selected from a chain halogenated alkane group having 1 to 4 carbon atoms or a cyclic halogenated alkane group having 5 to 7 carbon atoms.
  • the halogenated alkane group having 1 to 10 carbon atoms is selected from the group consisting of chloromethyl, dichloromethyl, trichloromethyl, 1-chloroethyl, 1,2-dichloroethyl, 2-chloro-n-propyl , 2,2-dichloro-n-propyl, 1-chloroisopropyl, monochlorocyclopropyl, 1-chloro-n-butyl, 2-chloroisobutyl, monochlorocyclobutyl, 1-chloro-n-pentane Base, 2-chloro-n-pentyl, 1-chloroisopentyl, 2,2-dichloromethylpropyl, monochlorocyclopentyl, 3-chloro-2,2-dimethylpropyl, 1-chloro 1-ethylpropyl, 1-chloro-1-methylbutyl, 2-chloro-2-methylbutyl, 2-chloro-n-hexy
  • the carboxylic acid ester compound may be selected from the group consisting of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, and propionic acid.
  • the carboxylic acid ester compound is selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and the aforementioned carboxylate compound is F, Cl, Br, One or more of one or more partially substituted or fully substituted compounds of I.
  • the dinitrile compound is selected from one or more of the compounds represented by Formula 2.
  • R 21 is selected from the group consisting of an alkylene group having 1 to 20 carbon atoms, a halogenated alkylene group having 1 to 20 carbon atoms, an alkyleneoxy group having 1 to 20 carbon atoms, and a carbon atom.
  • the halogen atom is selected from one or more of F, Cl, Br, and I.
  • R 21 is selected from the group consisting of an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, and a carbon number.
  • One of the halogen atoms selected from one or more of F, Cl, and Br.
  • the number of oxygen atoms may be one, two or more.
  • the dinitrile compound is selected from the group consisting of malononitrile, succinonitrile, 2-methylsuccinonitrile, tetramethylsuccinonitrile, glutaronitrile, 2- Methylglutaronitrile, adiponitrile, fumaronitrile, 2-methylene glutaronitrile, 3,5-dioxa-heptonitrile, ethylene glycol bis(2-cyanoethyl) ether, Diethylene glycol bis(2-cyanoethyl)ether, triethylene glycol bis(2-cyanoethyl)ether, tetraethylene glycol bis(2-cyanoethyl)ether, 1,2-di (2-Cyanoethoxy)ethane, 1,3-bis(2-cyanoethoxy)propane, 1,4-bis(2-cyanoethoxy)butane, 1,5-di ( 2-cyanoethoxy)pentane, ethylene glycol bis(4-
  • the aromatic compound overcharge additive is selected from the group consisting of biphenyl, cyclohexylbenzene, toluene, xylene, fluorobenzene, t-butylbenzene, and tert-amylbenzene. kind or several.
  • the cyclic sulfate is selected from one or more of the compounds represented by Formula 3:
  • n is an integer within 1 to 3; and R 31 , R 32 , R 33 and R 34 are each independently selected from H, F, Cl, Br, I, an alkyl group having 1 to 10 carbon atoms. And one of the alkoxy groups having 1 to 10 carbon atoms, wherein the H on the alkyl group or the alkoxy group may be substituted with one or more of F, Cl, Br, and I.
  • the cyclic sulfate may be selected from one or more of the following compounds:
  • the cyclic sulfonate is selected from one or more of the compounds represented by Formula 4:
  • n is an integer within 1 to 3; and R 41 , R 42 , R 43 , R 44 , R 45 and R 46 are each independently selected from H, F, Cl, Br, I, and the number of carbon atoms is One of an alkyl group having 1 to 10 carbon atoms and an alkoxy group having 1 to 10 carbon atoms, and an alkyl group or an alkoxy group H may be substituted by one or more of F, Cl, Br, and I. .
  • the cyclic sulfonate may be selected from one or more of the following compounds:
  • the volume of the carboxylate compound is 5% to 50% of the total volume of the organic solvent.
  • the volume of the carboxylic acid ester compound is from 10% to 40% of the total volume of the organic solvent.
  • the volume of the carboxylate compound is from 20% to 35% of the total volume of the organic solvent.
  • the content of the dinitrile compound is 0.5% to 10% by weight based on the total weight of the electrolytic solution, and preferably, the content of the dinitrile compound is the electrolytic 1% to 5% of the total weight of the liquid.
  • the aromatic compound overcharge additive is contained in an amount of from 0.5% to 15% by weight based on the total mass of the electrolytic solution.
  • the content of the aromatic compound overcharge additive is from 1% to 5% of the total weight of the electrolyte.
  • the total content of the cyclic sulfate and/or cyclic sulfonate is from 0.5% to 10% by weight based on the total weight of the electrolytic solution.
  • the content of the cyclic sulfate is 0.5% to 10% of the total weight of the electrolyte.
  • the content of the cyclic sulfonate is from 0.5% to 10% by weight based on the total weight of the electrolyte.
  • the total content of the two is 0.5% to 10% of the total weight of the electrolyte.
  • the total content of the cyclic sulfate and/or cyclic sulfonate is from 1% to 5% of the total weight of the electrolyte.
  • the electrolyte salt may be selected from a lithium salt, a sodium salt or a zinc salt, which varies depending on the secondary battery to which the electrolyte is applied.
  • the content of the electrolyte salt is 6.2% to 25% of the total weight of the electrolytic solution.
  • the content of the electrolyte salt is 6.25% to 18.8% of the total weight of the electrolyte.
  • the content of the electrolyte salt is the electrolyte 10% to 15% of the total weight.
  • the specific kind of the organic solvent is not particularly limited and may be selected according to actual needs.
  • a non-aqueous organic solvent is used.
  • the non-aqueous organic solvent may include any kind of carbonate and a halogenated compound of a carbonate.
  • the carbonate may include a cyclic carbonate and a chain carbonate.
  • the organic solvent may be selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, pentylene carbonate, fluoroethylene carbonate, dimethyl carbonate (DMC), One or more of diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), ⁇ -butyrolactone (BL), and tetrahydrofuran (THF).
  • EC ethylene carbonate
  • PC propylene carbonate
  • butylene carbonate pentylene carbonate
  • fluoroethylene carbonate fluoroethylene carbonate
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • BL ⁇ -butyrolactone
  • THF tetrahydrofuran
  • the electrolytic solution may be prepared by a conventional method, for example, mixing the respective materials in the electrolytic solution uniformly.
  • a secondary battery according to a second aspect of the invention includes the electrolytic solution according to the first aspect of the invention.
  • the secondary battery further includes: a positive electrode sheet, a negative electrode sheet, and a separator.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film disposed on the positive electrode current collector, and the positive electrode film includes a positive electrode active material, a binder, and a conductive agent.
  • the negative electrode sheet includes a negative electrode current collector and an negative electrode film disposed on the negative electrode current collector, and the negative electrode film includes a negative electrode active material, a binder, and may also include a conductive agent.
  • the separator is spaced between the positive electrode tab and the negative electrode tab.
  • the separator may be any separator material used in the existing secondary battery, such as polyethylene, polypropylene, polyvinylidene fluoride, and multilayers thereof. Composite membranes, but are not limited to these.
  • the secondary battery may be a lithium ion secondary battery, a sodium ion secondary battery, or a zinc ion secondary battery.
  • the electrolyte salt may be selected from a lithium salt
  • the lithium salt is LiPF 6 .
  • the positive electrode active material may be selected from lithium cobaltate (LiCoO 2 ), lithium nickelate (LiNiO 2 ), spinel-type LiMn 2 O 4 , olivine-type LiMPO 4 , one of ternary positive electrode materials LiNi x A y B (1-xy) O 2 and Li 1-x' (A' y' B' z' C 1-y'-z' ) O 2 or Several.
  • M is selected from one or more of Co, Ni, Fe, Mn, and V; and in the ternary positive electrode material LiNi x A y B (1-xy) O 2 , A and B are each independently selected from one of Co, Al, and Mn, and A and B are not the same, 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1 and x+y ⁇ 1; in the ternary positive electrode material Li 1 -x' (A' y' B' z' C 1-y'-z' ) In O 2 , A', B', and C are each independently selected from one of Co, Ni, Fe, and Mn, 0 ⁇ x' ⁇ 1, 0 ⁇ y' ⁇ 1, 0 ⁇ z' ⁇ 1 and y'+z' ⁇ 1, and A', B', and C are different.
  • the anode active material may be selected from metallic lithium.
  • the negative active material may also be selected from materials capable of intercalating lithium at ⁇ 2 V (vs. Li/Li + ).
  • the negative active material may be selected from natural graphite, artificial graphite, mesophase micro carbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , spinel structure lithiated TiO 2 -Li 4 Ti 5 One or more of O 12 and Li-Al alloys.
  • the secondary battery is a sodium ion secondary battery or a zinc ion secondary battery, it is only necessary to change the corresponding positive electrode active material, negative electrode active material, and electrolyte salt.
  • the lithium ion secondary batteries of Examples 1 to 14 and Comparative Examples 1 to 15 were each prepared in the following manner.
  • the positive electrode active material lithium cobaltate (LiCoO 2 ), the binder polyvinylidene fluoride, and the conductive agent acetylene black were mixed at a weight ratio of 98:1:1, and N-methylpyrrolidone (NMP) was added under the action of a vacuum mixer.
  • NMP N-methylpyrrolidone
  • the negative electrode active material artificial graphite, thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber were mixed at a weight ratio of 98:1:1, added to deionized water, and a negative electrode was obtained under the action of a vacuum mixer.
  • the slurry was uniformly coated on a negative electrode current collector copper foil having a thickness of 8 ⁇ m; the copper foil was air-dried at room temperature, transferred to an oven at 120 ° C for 1 hour, and then subjected to cold pressing and slitting to obtain a negative electrode sheet.
  • the content of LiPF 6 is 12.5% of the total weight of the electrolyte.
  • the specific types and contents of the carboxylate compound, the dinitrile compound, the aromatic compound overcharge additive, the cyclic sulfate, and the cyclic sulfonate used in the electrolytic solution are shown in Table 1.
  • the content of the carboxylate compound is a volume percentage calculated based on the total volume of the organic solvent
  • the content of the dinitrile compound, the aromatic compound overcharge additive, the cyclic sulfate, and the cyclic sulfonate is based on the electrolyte.
  • the total weight is calculated as a percentage by weight.
  • a 16 ⁇ m thick polypropylene separator (model C210, supplied by Celgard) was used.
  • the positive electrode sheet, the separator film and the negative electrode sheet are stacked in order, so that the separator is in a role of isolation between the positive and negative electrode sheets, and then wound to obtain a bare cell; the bare cell is placed in the outer packaging foil, The prepared electrolyte solution is injected into the dried bare cell, and subjected to vacuum encapsulation, standing, formation, shaping, and the like to obtain a lithium ion secondary battery.
  • the lithium ion secondary battery was charged at a constant current of 1 C (nominal capacity) to a voltage of 4.3 V at 25 ° C, and then charged at a constant voltage of 4.3 V until the current was less than or equal to 0.05 C. After leaving for 5 minutes, the constant current was 0.2 C. Discharge to the cut-off voltage of 3V, at which point the actual discharge capacity is recorded as D0.
  • the lithium ion secondary battery is charged at a constant current of 1 C to a voltage of 4.3 V, and then charged at a constant voltage of 4.3 V until the current is less than or equal to 0.05 C. After being left for 5 minutes, the battery is discharged at a constant current of 2 C to a voltage of 3 V, and the discharge is performed at this time. The capacity is recorded as D1.
  • Lithium ion secondary battery 2C/0.2C rate performance D1/D0 ⁇ 100%. 15 lithium ion secondary batteries were tested in each group and averaged.
  • the lithium ion secondary battery was charged at a constant current of 1 C to a voltage of 4.3 V at 45 ° C, further charged at a constant voltage of 4.3 V until the current was 0.05 C, and then discharged at a constant current of 1 C to a voltage of 3.0 V, which is a During the charge and discharge cycle, this discharge capacity is the discharge capacity of the first cycle.
  • the lithium ion secondary battery was subjected to 300 cycles of charge/discharge test in accordance with the above method, and the discharge capacity at the 300th cycle was detected.
  • the capacity retention ratio (%) of the lithium ion secondary battery after circulating at 45 ° C for 300 times (discharge capacity of 300 cycles of lithium ion secondary battery discharge / discharge capacity of the first cycle of lithium ion secondary battery) ⁇ 100%. 15 lithium ion secondary batteries were tested in each group and averaged.
  • the lithium ion secondary battery was charged at a constant current of 0.5 C to a voltage of 4.3 V at 25 ° C, and then charged at a constant voltage of 4.3 V until the current was 0.05 C. At this time, the thickness of the lithium ion secondary battery was measured and recorded as h. 0; after the lithium ion secondary battery is placed in a thermostat 60 deg.] C, removed after 30 days storage, the thickness of the test case and a lithium ion secondary battery is referred to as h 1.
  • the thickness expansion ratio of the lithium ion secondary battery after storage at 60 ° C for 30 days [(h 1 -h 0 ) / h 0 ] ⁇ 100%. 15 lithium ion secondary batteries were tested in each group and averaged.
  • the lithium ion secondary battery was charged at a constant current of 3 C (nominal capacity) to a voltage of 7.5 V at 25 ° C, and then subjected to constant voltage charging at 7.5 V for 5 hours, and the state of the lithium ion secondary battery was observed.
  • the pass rate of the lithium ion secondary battery can be calculated by taking no fire, no burning, or no explosion as a criterion.
  • the electrolyte of the present invention can simultaneously improve the high temperature cycle performance, high temperature storage performance, rate performance, and overcharge safety of the lithium ion secondary battery after being applied to the lithium ion secondary battery. performance.
  • the addition of the carboxylate compound and the dinitrile compound in Comparative Example 6 can improve the rate performance while improving the high temperature storage performance, but the high temperature cycle performance is deteriorated.
  • the simultaneous addition of the carboxylate compound and the aromatic compound overcharge additive can achieve both the rate performance and the overcharge safety performance, but the high temperature cycle performance and the high temperature storage performance deteriorate.
  • the addition of a carboxylate compound and a cyclic sulfate in Comparative Example 8 can improve rate performance and high temperature cycle performance, but deteriorates high temperature storage performance.
  • the addition of a dinitrile compound and an aromatic compound overcharge additive can improve high temperature storage performance and overcharge safety performance, but the rate performance and high temperature cycle performance deteriorate.
  • Simultaneous addition of a dinitrile compound and a cyclic sulfate in Comparative Example 10 can improve high temperature storage performance and high temperature. Cyclic performance, but the rate performance is poor.
  • the addition of the aromatic compound overcharge additive and the cyclic sulfate ester in Comparative Example 11 can improve high temperature cycle performance and overcharge safety performance, but deteriorates high temperature storage performance.
  • the addition of a carboxylate compound, a dinitrile compound, and an aromatic compound overcharge additive in Comparative Example 12 can improve rate performance, high temperature storage performance, and overcharge safety performance, but the high temperature cycle performance deteriorates.
  • the simultaneous addition of a carboxylate compound, a dinitrile compound, and a cyclic sulfate in Comparative Example 13 can improve rate performance, high temperature storage performance, and high temperature cycle performance, but the lithium ion secondary battery cannot pass the overcharge test.
  • the simultaneous addition of a carboxylate compound, an aromatic compound overcharge additive, and a cyclic sulfate in Comparative Example 14 can improve rate performance, overcharge safety performance, and high temperature cycle performance, but deteriorates high temperature storage performance.
  • the addition of the dinitrile compound, the aromatic compound overcharge additive, and the cyclic sulfate ester in Comparative Example 15 can improve high temperature storage performance, overcharge safety performance, and high temperature cycle performance, but the rate performance deteriorates.

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Abstract

一种电解液及二次电池。所述电解液包括电解质盐、有机溶剂以及添加剂。所述有机溶剂包括羧酸酯化合物。所述添加剂包括二腈化合物、芳香化合物过充添加剂以及环状硫酸酯和/或环状磺酸酯。当所述电解液应用到二次电池中后能够同时提高二次电池的倍率性能、高温存储性能、高温循环性能以及过充安全性能。

Description

电解液及二次电池 技术领域
本发明涉及电池技术领域，尤其涉及一种电解液及二次电池。
背景技术
在飞速发展的信息时代中，对手机、笔记本、相机等电子产品的需求逐年增加。二次电池尤其是锂离子二次电池作为电子产品的工作电源，具有能量密度高、无记忆效应、工作电压高等特点，正逐步取代传统的Ni-Cd、MH-Ni电池。然而随着电子产品市场需求的扩大及动力、储能设备的发展，人们对锂离子二次电池的要求不断提高，开发具有高能量密度和满足快速充放电的锂离子二次电池成为当务之急。目前，有效的方法是提高电极活性材料的电压、压实密度和选择合适的电解液。
目前，锂离子二次电池广泛应用的电解液包括以六氟磷酸锂为导电锂盐和以环状碳酸酯和链状碳酸酯的混合物有机溶剂，然而上述电解液仍存在诸多的不足，特别的是在高电压下，锂离子二次电池的性能较差，例如高温循环性能差、高温存储性能差、安全性能差以及倍率性能差。
发明内容
鉴于背景技术中存在的问题，本发明的目的在于提供一种电解液及二次电池，当所述电解液应用到二次电池中后，能够同时提高二次电池的倍率性能、高温存储性能、高温循环性能以及过充安全性能。
为了达到上述目的，在本发明的一方面，本发明提供了一种电解液，其包括电解质盐、有机溶剂以及添加剂。所述有机溶剂包括羧酸酯化合物。所述添加剂包括二腈化合物、芳香化合物过充添加剂以及环状硫酸酯和/或环状磺酸酯。
在本发明的另一方面，本发明提供了一种二次电池，其包括根据本发明一方面所述的电解液。
相对于现有技术，本发明的有益效果包括，但不限于：
本发明的电解液同时包括羧酸酯化合物、二腈化合物、芳香化合物过充添加剂以及环状硫酸酯和/或环状磺酸酯，当将其应用到二次电池中后，在上述物质的协同作用下，能够同时提高二次电池的倍率性能、高温存储性能、高温循环性能以及过充安全性能。
具体实施方式
下面详细说明根据本发明的电解液及二次电池。
首先说明根据本发明第一方面的电解液。
根据本发明第一方面的电解液包括电解质盐、有机溶剂以及添加剂。所述有机溶剂包括羧酸酯化合物。所述添加剂包括二腈化合物、芳香化合物过充添加剂以及环状硫酸酯和/或环状磺酸酯。
在根据本发明第一方面所述的电解液中，所述羧酸酯化合物用于改善二次电池的倍率性能，但当羧酸酯化合物应用于高电压体系的二次电池时，容易被氧化分解，另外使用羧酸酯化合物的二次电池在高温环境下使用时，二次电池多次循环后的容量损失严重，且二次电池的高温存储性能劣化严重。二腈化合物可与二次电池的正极络合，在减小高温时界面副反应的同时也降低了二次电池的动力学性能，同时二腈化合物由于具有较强的吸电子特性，容易在负极得到电子发生还原反应，其还原得到的产物不稳定，可沉积到负极上，从而影响二次电池的高温循环性能和倍率性能。环状硫酸酯和/或环状磺酸酯具有较高的还原电位，能优先在负极表面成膜，抑制羧酸酯化合物的还原，从而改善二次电池的高温循环性能，但当其含量较高时由于增大了二次电池正负极的阻抗从而恶化倍率性能；芳香化合物过充添加剂可以改善二次电池的过充安全性能，但是其含量增多时会导致电解液的粘度增大从而恶化二次电池的动力学性能。当电解液中同时包括上述物质时，在上述物质的协同作用下，能够同时提高二次电池的倍率性能、高温存储性能、高温循环性能以及过充安全性能。
在根据本发明第一方面所述的电解液中，所述羧酸酯化合物选自式1所示的化合物中的一种或几种。在式1中，R1、R2各自独立地选自碳原子数为 1～10的烷烃基、碳原子数为1～10的卤代烷烃基中的一种。其中，卤代烷烃基中的卤原子选自F、Cl、Br、I中的一种或几种。
Figure PCTCN2017093863-appb-000001
在根据本发明第一方面所述的电解液中，所述碳原子数为1～10的烷烃基可为链状烷烃基，也可为环状烷烃基。其中，链状烷烃基又包括直链烷烃基和支链烷烃基。另外，环状烷烃基上可以有取代基，也可以不含有取代基。在所述烷烃基中，碳原子数的优选的下限值可为1、2、3，碳原子数的优选的上限值可为4、5、6、7、8、9、10。优选地，R1、R2各自独立地选自碳原子数为1～6的链状烷烃基或碳原子数为3～8的环状烷烃基。更进一步优选地，R1、R2各自独立地选自碳原子数为1～4的链状烷烃基或碳原子数为5～7的环状烷烃基。
具体地，碳原子数为1～10的烷烃基可选自甲基、乙基、正丙基、异丙基、环丙基、正丁基、异丁基、仲丁基、叔丁基、环丁基、正戊基、异戊基、叔戊基、新戊基、环戊基、2,2二甲基丙基、1-乙基丙基、1-甲基丁基、2-甲基丁基、正己基、异己基、2-己基、3-己基、环己基、2-甲基戊基、3-甲基戊基、1,1,2-三甲基丙基、3,3-二甲基丁基、正庚基、2-庚基、3-庚基、2-甲基己基、3-甲基己基、4-甲基己基、异庚基、环庚基、正辛基、环辛基、壬基、癸基中的一种。
在根据本发明第一方面所述的电解液中，所述碳原子数为1～10的卤代烷烃基中卤原子的取代个数及其取代位置并没有特别的限制，可根据实际需求进行选择。具体地，卤原子的个数可为1个、2个、3个或4个。当卤原子的个数为2个以上时，卤原子的种类可以相同，也可以完全不同，也可以部分相同。卤代烷烃基可为链状卤代烷烃基也可为环状卤代烷烃基。链状卤代烷烃基又包括直链卤代烷烃基和支链卤代烷烃基。环状卤代烷烃基上可以有取代基，也可以不含有取代基。在所述卤代烷烃基中，碳原子数的优选的下限值可为1、2、3，碳原子数的优选的上限值可为4、5、6、7、8、9、10。优选地，R1、R2各自独立地选自碳原子数为1～6的链状卤代烷烃基或碳原子数为3～8的环状卤代烷烃基。更进一步优选地，R1、R2各自独立地选自碳原 子数为1～4的链状卤代烷烃基或碳原子数为5～7的环状卤代烷烃基。
具体地，碳原子数为1～10的卤代烷烃基选自氯甲基、二氯甲基、三氯甲基、1-氯乙基、1,2-二氯乙基、2-氯正丙基、2,2-二氯-正丙基、1-氯异丙基、一氯环丙基、1-氯正丁基、2-氯异丁基、一氯环丁基、1-氯正戊基、2-氯正戊基、1-氯异戊基、2,2-二氯甲基丙基、一氯环戊基、3-氯-2,2-二甲基丙基、1-氯-1-乙基丙基、1-氯-1-甲基丁基、2-氯-2-甲基丁基、2-氯正己基、一氯环己基、2-氯甲基戊基、3-氯-3-甲基戊基、2-氯-1,1,2-三甲基丙基、4-氯-3,3-二甲基丁基、2-氯正庚基中的一种。在上述的基团中，卤代烷烃基中的Cl原子还可被F、Br、I中的一种或几种部分取代或全部取代。
在根据本发明第一方面所述的电解液中，所述羧酸酯化合物可选自甲酸甲酯、甲酸乙酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丙酸丁酯、丙酸异丁酯、丙酸戊酯、丙酸异戊酯、异丙酸乙酯、丁酸乙酯、异丁酸乙酯、丁酸丁酯、异丁酸丁酯、丁酸戊酯、丁酸异戊酯、戊酸乙酯、异戊酸乙酯、戊酸丙酯、异戊酸丙酯以及前述羧酸酯化合物被F、Cl、Br、I中的一种或几种部分取代或全部取代的化合物中的一种或几种。优选地，所述羧酸酯化合物选自乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯以及前述羧酸酯化合物被F、Cl、Br、I中的一种或几种部分取代或全部取代的化合物中的一种或几种。
在根据本发明第一方面所述的电解液中，所述二腈化合物选自式2所示的化合物中的一种或几种。在式2中，R21选自碳原子数为1～20的亚烷烃基、碳原子数为1～20的卤代亚烷烃基、碳原子数为1～20的亚烷氧基、碳原子数为1～20的卤代亚烷氧基、碳原子数为2～20的亚烯烃基、碳原子数为2～20的卤代亚烯烃基中的一种。其中，卤原子选自F、Cl、Br、I中的一种或几种。
NC-R21-CN  式2
在根据本发明第一方面所述的电解液中，优选地，R21选自碳原子数为1～10的亚烷烃基、碳原子数为1～10的卤代亚烷烃基、碳原子数为1～10的亚烷氧基、碳原子数为1～10的卤代亚烷氧基、碳原子数为2～10的亚烯烃基、碳原子数为2～10的卤代亚烯烃基中的一种，其中，卤原子选自F、Cl、Br中的一种或几种。
在根据本发明第一方面所述的电解液中，亚烷氧基、卤代亚烷氧基中的 氧原子数可以为1个、2个或多个。
在根据本发明第一方面所述的电解液中，所述二腈化合物选自丙二腈、丁二腈、2-甲基丁二腈、四甲基丁二腈、戊二腈、2-甲基戊二腈、己二腈、富马二腈、2-亚甲基戊二腈、3,5-二氧杂-庚二腈、乙二醇二(2-氰基乙基)醚、二乙二醇二(2-氰基乙基)醚、三乙二醇二(2-氰基乙基)醚、四乙二醇二(2-氰基乙基)醚、1,2-二(2-氰乙氧基)乙烷、1,3-二(2-氰基乙氧基)丙烷、1,4-二(2-氰基乙氧基)丁烷、1,5-二(2-氰基乙氧基)戊烷、乙二醇二(4-氰基丁基)醚、1,6-二氰基己烷、1,2-二溴-2,4-二氰基丁烷中的一种或几种。
在根据本发明第一方面所述的电解液中，所述芳香化合物过充添加剂选自联苯、环己基苯、甲苯、二甲苯、氟苯、叔丁基苯、叔戊基苯中的一种或几种。
在根据本发明第一方面所述的电解液中，所述环状硫酸酯选自式3所示的化合物中的一种或几种：
Figure PCTCN2017093863-appb-000002
在式3中，n为1～3内的整数；R31、R32、R33、R34各自独立地选自H、F、Cl、Br、I、碳原子数为1～10的烷基、碳原子数为1～10的烷氧基中的一种，其中，烷基、烷氧基上的H还可被F、Cl、Br、I中的一种或几种取代。
在根据本发明第一方面所述的电解液中，具体地，所述环状硫酸酯可选自下述化合物中的一种或几种：
Figure PCTCN2017093863-appb-000003
Figure PCTCN2017093863-appb-000004
在根据本发明第一方面所述的电解液中，所述环状磺酸酯选自式4所示的化合物中的一种或几种：
Figure PCTCN2017093863-appb-000005
在式4中，n为1～3内的整数；R41、R42、R43、R44、R45、R46各自独立地选自H、F、Cl、Br、I、碳原子数为1～10的烷基、碳原子数为1～10的烷氧基中的一种，烷基、烷氧基上的H还可被F、Cl、Br、I中的一种或几种取代。
在根据本发明第一方面所述的电解液中，具体地，所述环状磺酸酯可选自下述化合物中的一种或几种：
Figure PCTCN2017093863-appb-000006
在根据本发明第一方面所述的电解液中，所述羧酸酯化合物的体积为所述有机溶剂的总体积的5％～50％。优选地，所述羧酸酯化合物的体积为所述有机溶剂的总体积的10％～40％。进一步优选地，所述羧酸酯化合物的体积为所述有机溶剂的总体积的20％～35％。
在根据本发明第一方面所述的电解液中，所述二腈化合物的含量为所述电解液的总重量的0.5％～10％，优选地，所述二腈化合物的含量为所述电解液的总重量的1％～5％。
在根据本发明第一方面所述的电解液中，所述芳香化合物过充添加剂的含量为所述电解液的总重量的0.5％～15％。优选地，所述芳香化合物过充添加剂的含量为所述电解液的总重量的1％～5％。
在根据本发明第一方面所述的电解液中，所述环状硫酸酯和/或环状磺酸酯的总含量为所述电解液的总重量的0.5％～10％。当电解液中仅含有环状硫酸酯时，环状硫酸酯的含量为所述电解液的总重量的0.5％～10％。当电解液中仅含有环状磺酸酯时，环状磺酸酯的含量为所述电解液的总重量的0.5％～10％。当电解液中同时含有环状硫酸酯和环状磺酸酯时，二者的总含量为所述电解液的总重量的0.5％～10％。优选地，所述环状硫酸酯和/或环状磺酸酯的总含量为所述电解液的总重量的1％～5％。
在根据本发明第一方面所述的电解液中，所述电解质盐可选自锂盐、钠盐或锌盐，依据所述电解液应用的二次电池的不同而不同。
在根据本发明第一方面所述的电解液中，所述电解质盐的含量为所述电解液的总重量的6.2％～25％。优选地，所述电解质盐的含量为所述电解液的总重量的6.25％～18.8％。进一步优选地，所述电解质盐的含量为所述电解液 的总重量的10％～15％。
在根据本发明第一方面所述的电解液中，所述有机溶剂的具体种类并没有特别的限制，可根据实际需求进行选择。优选地，使用非水有机溶剂。所述非水有机溶剂可包括任意种类的碳酸酯以及碳酸酯的卤代化合物。碳酸酯可包括环状碳酸酯和链状碳酸酯。具体地，所述有机溶剂可选自碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯、碳酸亚戊酯、氟代碳酸亚乙酯、碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸二丙酯、碳酸甲乙酯(EMC)、γ-丁内酯(BL)、四氢呋喃(THF)中的一种或几种。
在根据本发明第一方面所述的电解液中，电解液采用常规方法制备即可，例如将电解液中的各个物料混合均匀即可。
其次说明根据本发明第二方面的二次电池。
根据本发明第二方面的二次电池包括根据本发明第一方面所述的电解液。
在根据本发明第二方面所述的二次电池中，所述二次电池还包括：正极片、负极片以及隔离膜。所述正极片包括正极集流体和设置于正极集流体上的正极膜片，所述正极膜片包括正极活性材料、粘接剂和导电剂。所述负极片包括负极集流体和设置于负极集流体上的负极膜片，所述负极膜片包括负极活性材料、粘接剂，也可以包括导电剂。所述隔离膜间隔于正极片和负极片之间。
在根据本发明第二方面所述的二次电池中，所述隔离膜可以是现有二次电池中使用的任何隔离膜材料，例如聚乙烯、聚丙烯、聚偏氟乙烯以及它们的多层复合膜，但不仅限于这些。
在根据本发明第二方面所述的二次电池中，所述二次电池可为锂离子二次电池、钠离子二次电池或锌离子二次电池。
当二次电池为锂离子二次电池时，所述电解质盐可选自锂盐，所述锂盐可选自LiPF6、LiBF4、LiN(SO2F)2(简写为LiFSI)、LiN(CF3SO2)2(简写为LiTFSI)、LiClO4、LiAsF6、LiB(C2O4)2(简写为LiBOB)、LiBF2C2O4(简写为LiDFOB)、LiPO2F2、LiTFOP、LiN(SO2RF)2、LiN(SO2F)(SO2RF)中的一种或几种，其中，RF＝CnF2n+1，表示饱和全氟烷基，n为1～10内的整数。 优选地，所述锂盐为LiPF6。
当二次电池为锂离子二次电池时，所述正极活性材料可选自钴酸锂(LiCoO2)、镍酸锂(LiNiO2)、尖晶石型的LiMn2O4、橄榄石型的LiMPO4、三元正极材料LiNixAyB(1-x-y)O2以及Li1-x’(A’y’B’z’C1-y’-z’)O2中的一种或几种。其中，在橄榄石型的LiMPO4中，M选自Co、Ni、Fe、Mn、V中的一种或几种；在三元正极材料LiNixAyB(1-x-y)O2中，A、B各自独立地选自Co、Al、Mn中的一种，且A和B不相同，0<x<1，0<y<1且x+y<1；在三元正极材料Li1-x’(A’y’B’z’C1-y’-z’)O2中，A’、B’、C各自独立地选自Co、Ni、Fe、Mn中的一种，0<x’<1，0≤y’<1，0≤z’<1且y’+z’<1，且A’、B’、C不相同。
当二次电池为锂离子二次电池时，所述负极活性材料可以选自金属锂。所述负极活性材料也可以选自在＜2V(vs.Li/Li+)时可以嵌入锂的材料，具体地，所述负极活性材料可选自天然石墨、人造石墨、中间相微碳球(MCMB)、硬碳、软碳、硅、硅-碳复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO2、尖晶石结构的锂化TiO2-Li4Ti5O12、Li-Al合金中的一种或几种。
当二次电池为钠离子二次电池或锌离子二次电池时，仅需改变对应的正极活性材料、负极活性材料、电解质盐即可。
下面结合实施例，进一步阐述本申请。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。在实施例中仅示出二次电池为锂离子二次电池的情况，但本发明不限于此。
在以下实施例中，所用到的材料、试剂以及仪器如没有特殊说明，均可从商业途径购买获得。
为了便于说明，在下述实施例中用到的物质简写如下：
A1：丙酸乙酯
A2：丙酸丙酯
B1：己二腈
B2：丁二腈
C1：联苯
C2：叔丁基苯
D1：硫酸乙烯酯
D2：1,3-丙烷磺内酯
实施例1-14以及对比例1-15中的锂离子二次电池均按照下述方法进行制备。
(1)正极片制备
将正极活性材料钴酸锂(LiCoO2)、粘接剂聚偏氟乙烯、导电剂乙炔黑按照重量比98:1:1进行混合，加入N-甲基吡咯烷酮(NMP)，在真空搅拌机作用下搅拌至体系成均一透明状，获得正极浆料；将正极浆料均匀涂覆于厚度为12μm的正极集流体铝箔上；将铝箔在室温晾干后转移至120℃烘箱干燥1h，然后经过冷压、分切得到正极片。
(2)负极片制备
将负极活性材料人造石墨、增稠剂羧甲基纤维素钠(CMC)、粘接剂丁苯橡胶按照重量比98:1:1进行混合，加入到去离子水中，在真空搅拌机作用下获得负极浆料；将负极浆料均匀涂覆在厚度为8μm的负极集流体铜箔上；将铜箔在室温晾干后转移至120℃烘箱干燥1h，然后经过冷压、分切得到负极片。
(3)电解液制备
在含水量<10ppm的氩气气氛手套箱中，将EC、PC、DEC按照体积比为EC:PC:DEC＝1:1:1进行混合，接着将充分干燥的锂盐LiPF6溶解于混合有机溶剂中，之后加入羧酸酯化合物、二腈化合物、芳香化合物过充添加剂以及环状硫酸酯和/或环状磺酸酯，混合均匀后获得电解液。其中，LiPF6的含量为电解液的总重量的12.5％。电解液中所用到的羧酸酯化合物、二腈化合物、芳香化合物过充添加剂、环状硫酸酯、环状磺酸酯的具体种类以及含量如表1所示。在表1中，羧酸酯化合物的含量为基于有机溶剂的总体积计算得到的体积百分数，二腈化合物、芳香化合物过充添加剂、环状硫酸酯、环状磺酸酯的含量为基于电解液的总重量计算得到的重量百分数。
(4)隔离膜的制备
选用16μm厚的聚丙烯隔离膜(型号为C210，由Celgard公司提供)。
(5)锂离子二次电池的制备
将正极片、隔离膜、负极片按顺序叠好，使隔离膜处于正、负极片之间起到隔离的作用，然后卷绕得到裸电芯；将裸电芯置于外包装箔中，将上述制备好的电解液注入到干燥后的裸电芯中，经过真空封装、静置、化成、整形等工序，获得锂离子二次电池。
表1 实施例1-14以及对比例1-15的参数
Figure PCTCN2017093863-appb-000007
Figure PCTCN2017093863-appb-000008
接下来说明锂离子二次电池的测试过程。
(1)锂离子二次电池的倍率性能测试
在25℃下，将锂离子二次电池以1C(标称容量)恒流充电到电压为4.3V，然后以4.3V恒压充电至电流小于等于0.05C，搁置5min后，以0.2C恒流放电至截至电压3V，此时将实际放电容量记为D0。
然后将锂离子二次电池以1C恒流充电到电压为4.3V，再以4.3V恒压充电至电流小于等于0.05C，搁置5min后，以2C恒流放电至截至电压3V，此时的放电容量记为D1。
锂离子二次电池2C/0.2C倍率性能＝D1/D0×100％。每组测试15支锂离子二次电池，取平均值。
(2)锂离子二次电池的高温循环性能测试
在45℃下，将锂离子二次电池以1C恒流充电至电压为4.3V，进一步以4.3V恒压充电至电流为0.05C，然后以1C恒流放电至电压为3.0V，此为一个充放电循环过程，此次的放电容量为首次循环的放电容量。将锂离子二次电池按照上述方法进行300次循环充电/放电测试，检测得到第300次循环的放电容量。
锂离子二次电池45℃循环300次后的容量保持率(％)＝(锂离子二次电池循环300次的放电容量/锂离子二次电池首次循环的放电容量)×100％。每组测试15支锂离子二次电池，取平均值。
(3)锂离子二次电池的高温存储性能测试
在25℃下，将锂离子二次电池以0.5C恒流充电至电压为4.3V，然后以4.3V恒压充电至电流为0.05C，此时测试锂离子二次电池的厚度并记为h0； 之后将锂离子二次电池放入60℃的恒温箱，存储30天后取出，测试此时锂离子二次电池的厚度并记为h1。
锂离子二次电池60℃存储30天后的厚度膨胀率＝[(h1-h0)/h0]×100％。每组测试15支锂离子二次电池，取平均值。
(4)锂离子二次电池的过充性能测试
在25℃下，将锂离子二次电池以3C(标称容量)恒流充电至电压为7.5V，之后以7.5V继续恒压充电5h，观察锂离子二次电池的状态。以不起火、不燃烧、不爆炸为判定标准，计算锂离子二次电池的通过率。
表2 实施例1-14以及对比例1-15的测试结果
Figure PCTCN2017093863-appb-000009
Figure PCTCN2017093863-appb-000010
从上述表2中的相关结果可以得知，本发明的电解液应用到锂离子二次电池中后，可以同时改善锂离子二次电池的高温循环性能、高温存储性能、倍率性能以及过充安全性能。
对比例2中仅加入羧酸酯化合物，锂离子二次电池的倍率性能得到了改善，但是高温循环性能以及高温存储性能恶化。对比例3中仅加入二腈化合物，可以改善高温存储性能，但是对倍率性能有稍许恶化。对比例4中仅加入芳香化合物过充添加剂可以改善过充安全性能，但是其它性能均较差。对比例5中加入环状硫酸酯可以改善高温循环性能，但是其含量增大时会恶化倍率性能。对比例6中同时加入羧酸酯化合物和二腈化合物，可以改善倍率性能的同时改善高温存储性能，但是高温循环性能恶化。对比例7中同时加入羧酸酯化合物和芳香化合物过充添加剂，可以兼顾倍率性能和过充安全性能，但是高温循环性能以及高温存储性能恶化。对比例8中同时加入羧酸酯化合物和环状硫酸酯，可以改善倍率性能和高温循环性能，但是会恶化高温存储性能。对比例9中同时加入二腈化合物和芳香化合物过充添加剂，可以改善高温存储性能和过充安全性能，但是倍率性能和高温循环性能恶化。对比例10中同时加入二腈化合物和环状硫酸酯可以改善高温存储性能和高温 循环性能，但是倍率性能较差。对比例11中同时加入芳香化合物过充添加剂和环状硫酸酯可以改善高温循环性能和过充安全性能，但是会恶化高温存储性能。对比例12中同时加入羧酸酯化合物、二腈化合物和芳香化合物过充添加剂可以改善倍率性能、高温存储性能和过充安全性能，但是高温循环性能恶化。对比例13中同时加入羧酸酯化合物、二腈化合物和环状硫酸酯可以改善倍率性能、高温存储性能和高温循环性能，但是锂离子二次电池无法通过过充测试。对比例14中同时加入羧酸酯化合物、芳香化合物过充添加剂和环状硫酸酯可以改善倍率性能、过充安全性能和高温循环性能，但是会恶化高温存储性能。对比例15中同时加入二腈化合物、芳香化合物过充添加剂和环状硫酸酯可以改善高温存储性能、过充安全性能和高温循环性能，但是倍率性能恶化。

Claims (10)

  1. 一种电解液，包括：
    电解质盐；
    有机溶剂；以及
    添加剂；
    其特征在于，
    所述有机溶剂包括羧酸酯化合物；
    所述添加剂包括：
    二腈化合物；
    芳香化合物过充添加剂；以及
    环状硫酸酯和/或环状磺酸酯。
  2. 根据权利要求1所述的电解液，其特征在于，所述羧酸酯化合物选自式1所示的化合物中的一种或几种；
    Figure PCTCN2017093863-appb-100001
    其中，
    R1、R2各自独立地选自碳原子数为1～10的烷烃基、碳原子数为1～10的卤代烷烃基中的一种；
    卤代烷烃基中的卤原子选自F、Cl、Br、I中的一种或几种。
  3. 根据权利要求2所述的电解液，其特征在于，所述羧酸酯化合物选自选自甲酸甲酯、甲酸乙酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丙酸丁酯、丙酸异丁酯、丙酸戊酯、丙酸异戊酯、异丙酸乙酯、丁酸乙酯、异丁酸乙酯、丁酸丁酯、异丁酸丁酯、丁酸戊酯、丁酸异戊酯、戊酸乙酯、异戊酸乙酯、戊酸丙酯、异戊酸丙酯以及前述羧酸酯化合物被F、Cl、Br、I中的一种或几种部分取代或全部取代的化合物中的一种或几种，优选地，所述羧酸酯化合物选自乙酸甲酯、乙酸乙酯、乙酸丙酯、 丙酸甲酯、丙酸乙酯、丙酸丙酯以及前述羧酸酯化合物被F、Cl、Br、I中的一种或几种部分取代或全部取代的化合物中的一种或几种。
  4. 根据权利要求1所述的电解液，其特征在于，所述二腈化合物选自式2所示的化合物中的一种或几种；
    NC-R21-CN  式2
    其中，
    R21选自碳原子数为1～20的亚烷烃基、碳原子数为1～20的卤代亚烷烃基、碳原子数为1～20的亚烷氧基、碳原子数为1～20的卤代亚烷氧基、碳原子数为2～20的亚烯烃基、碳原子数为2～20的卤代亚烯烃基中的一种，卤原子选自F、Cl、Br、I中的一种或几种。
  5. 根据权利要求4所述的电解液，其特征在于，所述二腈化合物选自丙二腈、丁二腈、2-甲基丁二腈、四甲基丁二腈、戊二腈、2-甲基戊二腈、己二腈、富马二腈、2-亚甲基戊二腈、3,5-二氧杂-庚二腈、乙二醇二(2-氰基乙基)醚、二乙二醇二(2-氰基乙基)醚、三乙二醇二(2-氰基乙基)醚、四乙二醇二(2-氰基乙基)醚、1,2-二(2-氰乙氧基)乙烷、1,3-二(2-氰基乙氧基)丙烷、1,4-二(2-氰基乙氧基)丁烷、1,5-二(2-氰基乙氧基)戊烷、乙二醇二(4-氰基丁基)醚、1,6-二氰基己烷、1,2-二溴-2,4-二氰基丁烷中的一种或几种。
  6. 根据权利要求1所述的电解液，其特征在于，所述芳香化合物过充添加剂选自联苯、环己基苯、甲苯、二甲苯、氟苯、叔丁基苯、叔戊基苯中的一种或几种。
  7. 根据权利要求1所述的电解液，其特征在于，
    所述环状硫酸酯选自式3所示的化合物中的一种或几种：
    Figure PCTCN2017093863-appb-100002
    在式3中，n为1～3内的整数，R31、R32、R33、R34各自独立地选自H、F、Cl、Br、I、碳原子数为1～10的烷基、碳原子数为1～10的烷氧基中的一种，其中，烷基、烷氧基上的H还可被F、Cl、Br、I中的一种或几种取代；
    所述环状磺酸酯选自式4所示的化合物中的一种或几种：
    Figure PCTCN2017093863-appb-100003
    在式4中，n为1～3内的整数，R41、R42、R43、R44、R45、R46各自独立地选自H、F、Cl、Br、I、碳原子数为1～10的烷基、碳原子数为1～10的烷氧基中的一种，烷基、烷氧基上的H还可被F、Cl、Br、I中的一种或几种取代。
  8. 根据权利要求7所述的电解液，其特征在于，
    所述环状硫酸酯选自下述化合物中的一种或几种：
    Figure PCTCN2017093863-appb-100004
    Figure PCTCN2017093863-appb-100005
    所述环状磺酸酯选自下述化合物中的一种或几种：
    Figure PCTCN2017093863-appb-100006
  9. 根据权利要求1所述的电解液，其特征在于，
    所述羧酸酯化合物的体积为所述有机溶剂的总体积的5％～50％，优选为10％～40％，进一步优选为20％～35％；
    所述二腈化合物的含量为所述电解液的总重量的0.5％～10％，优选为1％～5％；
    所述芳香化合物过充添加剂的含量为所述电解液的总重量的0.5％～15％，优选为1％～5％；
    所述环状硫酸酯和/或环状磺酸酯的总含量为所述电解液的总重量的 0.5％～10％，优选为1％～5％。
  10. 一种二次电池，其特征在于，包括根据权利要求1-9中任一项所述的电解液。
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