CN111916825B - Non-aqueous electrolyte for lithium ion battery and lithium ion battery using same - Google Patents
Non-aqueous electrolyte for lithium ion battery and lithium ion battery using same Download PDFInfo
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- CN111916825B CN111916825B CN202010615112.3A CN202010615112A CN111916825B CN 111916825 B CN111916825 B CN 111916825B CN 202010615112 A CN202010615112 A CN 202010615112A CN 111916825 B CN111916825 B CN 111916825B
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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
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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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
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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
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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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
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
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- 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
Abstract
The invention provides a non-aqueous electrolyte for a lithium ion battery and the lithium ion battery using the same. The nonaqueous electrolytic solution used in the present invention comprises (a) a lithium salt, (b) a nonaqueous organic solvent and (c) at least one compound represented by formula 1,
wherein the nonaqueous electrolytic solution further comprises at least one of the following components (d) and (e): (d) at least one compound represented by the formula 2,
Description
Technical Field
The invention belongs to the technical field of electrolyte for lithium ion batteries, and particularly relates to a non-aqueous electrolyte for a lithium ion battery and the lithium ion battery using the same.
Background
Since commercialization, lithium ion batteries have been widely used in the fields of digital, energy storage, power, military space and communication equipment, due to their portability, high specific energy, no memory effect, and good cycle performance. With the wide application of lithium ion batteries, consumers have made higher demands on the energy density, cycle life, high temperature performance, safety and other performances of lithium ion batteries.
Most lithium ion battery products have the problem that the high-temperature performance and the low-temperature performance can not be considered at the same time, so that the high-temperature and low-temperature performance of the lithium ion battery is improved by adding an additive into an electrolyte, but when the common additive has better high-temperature action, the impedance is larger, and the high-temperature effect of a low-impedance additive is deficient, so that the better high-temperature and low-temperature performance is obtained by the combination optimization of the additive.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a nonaqueous electrolyte for a lithium ion battery and the lithium ion battery using the same. The nonaqueous electrolytic solution includes (a) a lithium salt, (b) a nonaqueous organic solvent, and (c) at least one compound represented by formula 1, wherein the nonaqueous electrolytic solution further includes at least one of the following components (d) and (e): (d) at least one compound represented by formula 2, and (e) an acid anhydride-based compound; through the synergistic effect of the lithium ion battery and the lithium ion battery, the impedance of the battery can be reduced while the electrical performance under the high-temperature condition is ensured, so that the lithium ion battery has excellent high-temperature storage performance, cycle performance and low-temperature charge and discharge performance.
The invention is realized by the following technical scheme:
a nonaqueous electrolytic solution comprising (a) a lithium salt, (b) a nonaqueous organic solvent, and (c) at least one compound represented by formula 1, wherein the nonaqueous electrolytic solution further comprises at least one of the following components (d) and (e):
(d) at least one compound represented by formula 2, and
(e) acid anhydride compounds;
in the formula 1, R1、R2Identical or different, independently of one another, from hydrogen, halogen substituted or unsubstituted C1-C6Alkyl, halogen substituted or unsubstituted C2-C5Or halogen substituted or unsubstituted C2-C5Alkynyl of (a);
in formula 2, M1、M2、M3Identical or different, independently of one another, from halogen substituted or unsubstituted C1-C5Alkyl, halogen substituted or unsubstituted C2-C5Or halogen substituted or unsubstituted C2-C5And at least one halogen substituted or unsubstituted C2-C5Or halogen substituted or unsubstituted C2-C5Alkynyl group of (1).
According to the invention, the acid anhydride compound is selected from one or more of succinic anhydride, glutaric anhydride, adipic anhydride, pimelic anhydride, phthalic anhydride, maleic anhydride, citraconic anhydride, citric anhydride and 2, 3-dimethyl maleic anhydride, or is one or more of fluoro compounds of the acid anhydride compound. The fluorinated compound of the acid anhydride compound is perfluoroglutaric anhydride, for example.
According to the invention, R1、R2Identical or different, independently of one another, from hydrogen, halogen substituted or unsubstituted C1-C5Alkyl group of (1).
Preferably, R1、R2Identical or different, independently of one another, from hydrogen, fluorine, methyl, ethyl or propyl.
According to the invention, the compound shown in the formula 1 is selected from at least one of the following compounds A1-A5:
according to the invention, M1、M2、M3Identical or different, independently of one another, from halogen substituted or unsubstituted C1-C3Alkyl, halogen substituted or unsubstituted C2-C3Or halogen substituted or unsubstituted C2-C3And at least one halogen substituted or unsubstituted C2-C3Or halogen substituted or unsubstituted C2-C3Alkynyl group of (1).
Preferably, M1、M2、M3Identical or different, independently of one another, from the group consisting of methyl, ethyl, propyl, ethenyl, propenyl, ethynyl, propynyl or isobutenyl and which contains at least one ethenyl, ethynyl, propynyl or isobutenyl group.
According to the invention, the compound shown in the formula 2 is selected from at least one of the following compounds B1-B8:
according to the invention, the content of the compound represented by the formula 1 is 0.1 to 10 wt% based on the total mass of the nonaqueous electrolytic solution, for example, 0.1 wt%, 0.2 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 10 wt%.
According to the invention, the content of the compound represented by the formula 2 is 0 to 3 wt%, preferably 0.1 to 3 wt%, for example, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt% of the total mass of the nonaqueous electrolytic solution.
According to the present invention, the content of the acid anhydride-based compound is 0 to 2 wt%, preferably 0.1 to 2 wt%, for example, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2 wt% of the total mass of the nonaqueous electrolytic solution.
According to the invention, the nonaqueous electrolyte further comprises one or more of the following additives: vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, ethylene sulfite, methylene methanedisulfonate, vinyl sulfate, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, sebacic dinitrile, 1,3, 6-hexanetrinitrile, 1, 2-bis (2-cyanoethoxy) ethane, 1, 3-propanesultone, propenyl-1, 3-sultone.
According to the present invention, the lithium salt is selected from one or two or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalato borate, lithium difluorosulfonimide, lithium bistrifluoromethylsulfonyl imide, lithium difluorobis-oxalato phosphate, lithium tetrafluoroborate, lithium bisoxalato borate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis (trifluoromethylsulfonyl) imide, lithium bis (pentafluoroethylsulfonyl) imide, lithium tris (trifluoromethylsulfonyl) methide or lithium bis (trifluoromethylsulfonyl) imide.
According to the present invention, the content of the lithium salt is 12 to 18 wt%, for example, 12 wt%, 12.5 wt%, 13 wt%, 13.5 wt%, 14 wt%, 14.5 wt%, 15 wt%, 15.5 wt%, 16 wt%, 16.5 wt%, 17 wt%, 17.5 wt%, 18 wt% of the total mass of the nonaqueous electrolytic solution.
According to the invention, the non-aqueous organic solvent is selected from carbonates and/or carboxylates.
Illustratively, the carbonate is selected from one or more of the following fluorinated or unsubstituted solvents: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.
Illustratively, the carboxylic acid ester is selected from one or more of the following fluorinated or unsubstituted solvents: propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isoamyl acetate, ethyl propionate, n-propyl propionate, methyl butyrate, ethyl n-butyrate.
The invention also provides a preparation method of the non-aqueous electrolyte, which comprises the following steps:
mixing (a) a lithium salt, (b) a non-aqueous organic solvent, (c) at least one compound represented by formula 1, and (d) at least one compound represented by formula 2; alternatively, the first and second electrodes may be,
mixing (a) a lithium salt, (b) a nonaqueous organic solvent, (c) at least one compound represented by formula 1, and (e) an acid anhydride compound; alternatively, the first and second electrodes may be,
mixing (a) a lithium salt, (b) a nonaqueous organic solvent, (c) at least one compound represented by formula 1, (d) at least one compound represented by formula 2, and (e) an acid anhydride compound;
and preparing the non-aqueous electrolyte.
Illustratively, the method comprises the steps of:
uniformly mixing (b) a nonaqueous organic solvent, (c) at least one compound shown as a formula 1 and (d) at least one compound shown as a formula 2, detecting moisture, freezing at a low temperature of about-10 ℃ for 2-5 hours after the moisture is qualified, quickly adding (a) a lithium salt, and preparing the nonaqueous electrolytic solution after the moisture and a free acid are detected to be qualified.
Illustratively, the method comprises the steps of:
uniformly mixing (b) a nonaqueous organic solvent, (c) at least one compound shown as a formula 1, (d) at least one compound shown as a formula 2 and (f) other additives, detecting moisture, freezing at a low temperature of about-10 ℃ for 2-5 hours after the moisture is qualified, rapidly adding (a) a lithium salt, and detecting the moisture and a free acid to be qualified to prepare the nonaqueous electrolytic solution.
Illustratively, the method comprises the steps of:
uniformly mixing (b) a nonaqueous organic solvent, (c) at least one compound shown as a formula 1 and (e) an anhydride compound, detecting moisture, freezing at a low temperature of about-10 ℃ for 2-5 hours after the moisture is qualified, rapidly adding (a) a lithium salt, and preparing the nonaqueous electrolytic solution after the moisture and free acid are detected to be qualified.
Illustratively, the method comprises the steps of:
uniformly mixing (b) a nonaqueous organic solvent, (c) at least one compound shown as a formula 1, (e) an anhydride compound and (f) other additives, detecting moisture, freezing at a low temperature of about-10 ℃ for 2-5 hours after the moisture is qualified, rapidly adding (a) a lithium salt, and preparing the nonaqueous electrolytic solution after the moisture and a free acid are detected to be qualified.
Illustratively, the method comprises the steps of:
uniformly mixing (b) a nonaqueous organic solvent, (c) at least one compound shown as a formula 1, (d) at least one compound shown as a formula 2 and (e) an anhydride compound, detecting water content, freezing at a low temperature of about-10 ℃ for 2-5 hours after the water content is qualified, quickly adding (a) a lithium salt, and preparing the nonaqueous electrolytic solution after the water content and a free acid are detected to be qualified.
Illustratively, the method comprises the steps of:
uniformly mixing (b) a nonaqueous organic solvent, (c) at least one compound shown as a formula 1, (d) at least one compound shown as a formula 2, (e) an anhydride compound and (f) other additives, detecting the moisture, freezing at the low temperature of about-10 ℃ for 2-5 hours after the moisture is qualified, rapidly adding (a) a lithium salt, and preparing the nonaqueous electrolytic solution after the moisture and free acid are detected to be qualified.
The invention also provides a lithium ion battery which comprises the non-aqueous electrolyte.
According to the present invention, the lithium ion battery further includes a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, and a lithium ion separator.
According to the invention, the positive active material is selected from one or more of layered lithium transition metal composite oxide, lithium manganate and lithium cobaltate mixed ternary materials; the chemical formula of the layered lithium transition metal composite oxide is Li1+ xNiyCozM(1-y-z)Q2Wherein x is more than or equal to-0.1 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, and y + z is more than or equal to 0 and less than or equal to 1; wherein M is one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo and Zr; q is one or more of O, F, P, S.
According to the invention, the negative active material is selected from one or more of carbon materials, silicon-based materials, tin-based materials or alloy materials corresponding to the carbon materials, the silicon-based materials and the tin-based materials.
According to the invention, the working voltage range of the lithium ion battery is 4.2V and above.
According to the invention, the lithium ion battery has a thickness change rate of less than or equal to 8 percent (for example, less than or equal to 7 percent) after circulating for 400 circles at 0 ℃ according to a charge-discharge system of 0.7C/0.7C; the capacity retention rate is more than or equal to 94 percent.
According to the invention, the thickness change rate of the lithium ion battery is less than or equal to 9 percent (for example, less than or equal to 8.6 percent) after the lithium ion battery is cycled for 800 circles under a charging and discharging system of 1C/1C at 25 ℃; the capacity retention rate is more than or equal to 79 percent (for example, more than or equal to 79.5 percent).
According to the invention, the change rate of the thickness of the lithium ion battery is less than or equal to 9 percent (for example, less than or equal to 8.9 percent) after the lithium ion battery is cycled for 600 circles under a charging and discharging system of 1C/1C at 45 ℃; the capacity retention rate is more than or equal to 76% (for example, more than or equal to 76.7%).
According to the invention, the lithium ion battery is charged to 4.3V at 60 ℃ according to 0.7C, then charged to 0.05C at a constant voltage of 4.3V until a cut-off current, then discharged to 3.0V at a constant current of 0.5C, then charged to 4.3V at 0.7C, and then charged to 0.05C at a constant voltage of 4.3V until a cut-off current is reached, and the rate of change in the thickness of the battery after being left for 14 days is less than or equal to 9% (e.g., less than or equal to 8.5%).
Terms and explanations:
the term "halogen" refers to F, Cl, Br and I.
The term "C1-C6The alkyl group of (A) is understood to preferably denote a straight-chain or branched saturated monovalent hydrocarbon group having 1 to 6 carbon atoms, preferably C1-C5Alkyl group of (1). "C1-C6Alkyl groups "are understood to preferably denote straight-chain or branched, saturated monovalent hydrocarbon radicals having 1,2, 3, 4, 5 or 6 carbon atoms. The alkyl group is, for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a 2-methylbutyl group, a 1-ethylpropyl group, a1, 2-dimethylpropyl group, a neopentyl group, a1, 1-dimethylpropyl group, a 4-methylpentyl group, a 3-methylpentyl group, a 2-ethylbutyl group, a 1-ethylbutyl group, a 3, 3-dimethylbutyl group, a 2, 2-dimethylbutyl group, a1, 1-dimethylbutyl group, a 2, 3-dimethylbutyl group, a1, 3-dimethylbutyl group or a1, 2-dimethylbutyl group, or the like, or isomers thereof. In particular, such groups are, for example, methyl, ethyl, propyl, butyl, isopropyl, isobutyl, sec-butyl, tert-butyl, more particularly such groups having 1,2 or 3 carbon atoms ("C)1-3Alkyl groups of (a) such as methyl, ethyl, n-propyl or isopropyl.
The term "C2-5Alkenyl "is understood to preferably mean a straight-chain or branched, monovalent hydrocarbon radical which contains one or more double bonds and has 2,3, 4 or 5 carbon atoms, in particular 2 or 3 carbon atoms (" C)2-3Alkenyl groups) it is understood that where the alkenyl group contains more than one double bond, the double bonds may be separated from each other or conjugated. Alkenyl is, for example, vinyl, allyl, (E) -2-methylvinyl, (Z) -2-methylvinyl, (E) -but-2-enyl, (Z) -but-2-enyl, (E) -but-1-enyl, (Z) -but-1-enyl, pent-4-enyl, (E) -pent-3-eneA radical, (Z) -pent-3-enyl, (E) -pent-2-enyl, (Z) -pent-2-enyl, (E) -pent-1-enyl, (Z) -pent-1-enyl, hex-5-enyl, (E) -hex-4-enyl, (Z) -hex-4-enyl, (E) -hex-3-enyl, (Z) -hex-3-enyl, (E) -hex-2-enyl, (Z) -hex-2-enyl, (E) -hex-1-enyl, (Z) -hex-1-enyl, isopropenyl, 2-methylprop-2-enyl, 1-methylprop-2-enyl, m-E-n-2-enyl, m-propenyl, m-2-enyl, m-propenyl, m-1-2-propenyl, m-1-2-enyl, m-propenyl, m-1-2-propenyl, m-2-enyl, m-propenyl, m-1-2-enyl, m-y-l, m-2-y-l, m-2-y, m-l, m-2-l, m-2-l, m-y, m-l, m-2-l, m-y, m-l, m-l, m-y, m-l, m-y, m-l, m-y, m-l, m-y, 2-methylprop-1-enyl, (E) -1-methylprop-1-enyl, (Z) -1-methylprop-1-enyl, 3-methylbut-3-enyl, 2-methylbut-3-enyl, 1-methylbut-3-enyl, 3-methylbut-2-enyl, (E) -2-methylbut-2-enyl, (Z) -2-methylbut-2-enyl, (E) -1-methylbut-2-enyl, (Z) -1-methylbut-2-enyl, (E) -3-methylbut-1-enyl, (Z) -3-methylbut-1-enyl, (E) -2-methylbut-1-enyl, (Z) -2-methylbut-1-enyl, (E) -1-methylbut-1-enyl, (Z) -1-methylbut-1-enyl, 1-dimethylprop-2-enyl, 1-ethylprop-1-enyl, 1-propylvinyl, 1-isopropylvinyl.
The term "C2-C5Alkynyl "is understood to mean a straight-chain or branched, monovalent hydrocarbon radical which contains one or more triple bonds and has 2 to 5 carbon atoms, in particular 2 or 3 carbon atoms (" C)2-C3Alkynyl group of (a). Said alkynyl group is for example ethynyl, prop-1-ynyl, prop-2-ynyl, but-1-ynyl, but-2-ynyl, but-3-ynyl, pent-1-ynyl, pent-2-ynyl, pent-3-ynyl, pent-4-ynyl, hex-1-ynyl, hex-2-ynyl, hex-3-ynyl, hex-4-ynyl, hex-5-ynyl, 1-methylprop-2-ynyl, 2-methylbut-3-ynyl, 1-methylbut-2-ynyl, 3-methylbut-1-ynyl, 1-ethylprop-2-ynyl. In particular, the alkynyl group is ethynyl, prop-1-ynyl or prop-2-ynyl.
The invention has the beneficial effects that:
the invention provides a non-aqueous electrolyte for a lithium ion battery and the lithium ion battery using the same. The nonaqueous electrolytic solution adopted by the invention comprises (a) lithium salt, (b) nonaqueous organic solvent and (c) at least one compound shown in formula 1, wherein the nonaqueous electrolytic solution also comprises at least one of the following components (d) and (e): (d) at least one compound represented by formula 2, and (e) an acid anhydride-based compound; wherein, (c) at least one compound shown in formula 1 has relatively lower reaction potential and preferentially forms compact and impedance-reduced films on the surfaces of the positive and negative electrodes, (e) the anhydride compound has higher reduction potential, both can form films on the positive and negative electrodes in preference to (d) at least one compound shown in formula 2, and (d) at least one compound shown in formula 2 can further form films on the basis, so that the flexibility of the films is increased, the protection of the positive and negative electrodes is further enhanced, compared with the single compound shown in formula 2 (d), the combination can reduce the using amount of the compound, so that the overall impedance is lower, and the battery has better low-temperature charge and discharge performance while improving the high-temperature storage performance and the cycle performance through the synergistic effect of the compound.
Detailed Description
The present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
Comparative example 1
(1) Preparation of positive plate
Mixing a positive electrode active material 4.35V NCM523, a binder polyvinylidene fluoride (PVDF-5130) and a conductive agent acetylene black according to a weight ratio of 97:1.5:1.5, adding N-methyl pyrrolidone (NMP), and stirring under the action of a vacuum stirrer until a mixed system becomes a uniform and fluid positive electrode slurry; uniformly coating the positive electrode slurry on a copper foil with the thickness of 10 mu m; baking the coated aluminum foil in an oven with different temperature gradients of 15m, drying the aluminum foil in a vacuum oven at 100 ℃ for 9h, and rolling and slitting to obtain the required positive plate.
(2) Preparation of negative plate
Mixing a negative electrode active material graphite, a thickening agent sodium carboxymethyl cellulose (CMC-Na), a binder styrene butadiene rubber and a conductive agent acetylene black according to a weight ratio of 97:1.5:1.5:1, adding deionized water, and obtaining negative electrode slurry under the action of a vacuum stirrer; uniformly coating the negative electrode slurry on a copper foil with the thickness of 8 mu m; and baking the coated aluminum foil in an oven with a temperature gradient at a certain speed, drying the aluminum foil in a vacuum oven at 80 ℃ for 8h, and then carrying out cold pressing and slitting to obtain the negative plate.
(3) Preparation of electrolyte
Uniformly mixing ethylene carbonate, diethyl carbonate and methyl ethyl carbonate according to the mass ratio of 30:45:25 in a glove box filled with argon and qualified in water oxygen content (the solvent and the additive need to be normalized together), freezing the solvent at the low temperature of about-10 ℃ for 2-5h, and then rapidly adding 13 wt% of fully dried lithium hexafluorophosphate (LiPF)6) And dissolving the electrolyte in an organic solvent, and uniformly stirring, and obtaining the electrolyte of the comparative example 1 after the water and the free acid are detected to be qualified.
(4) Preparation of the separator
A3 μm oily mixed coating membrane was coated on a substrate made of Asahi chemical 7 μm.
(5) Preparation of lithium ion battery
Stacking the prepared positive plate, the prepared isolating membrane and the prepared negative plate in sequence to ensure that the isolating membrane is positioned between the positive plate and the negative plate to play an isolating role, and then winding to obtain a naked battery cell without liquid injection; placing the bare cell in an outer packaging foil, injecting the prepared electrolyte into the dried bare cell, and performing vacuum packaging, standing, formation, shaping, sorting and other processes to obtain the required lithium ion battery.
Examples 1 to 14 and comparative examples 2 to 9
The preparation processes of examples 1 to 14 and comparative examples 2 to 9 are the same as in comparative example 1, except that the components and contents of the electrolyte are different, and the specific components and contents to be added are shown in table 1 below.
TABLE 1 compositions and contents of electrolytes of examples 1 to 14 and comparative examples 1 to 9
And (3) performance testing:
(1) low temperature cycle test at 0 deg.C
Testing full electricity before testingThickness D of the core0Placing the battery in an environment of (0 +/-2) DEG C, standing for 3 hours, charging the battery to 4.3V according to 0.7C when the battery core body reaches (0 +/-2) DEG C, charging the battery to a cut-off current of 0.05C at a constant voltage of 4.3V, discharging to 3V at 0.7C, and recording the initial capacity Q0When the circulation reaches the required times or the capacity decay rate is lower than 80 percent or the thickness exceeds the thickness required by the test, the previous discharge capacity is taken as the capacity Q of the battery1Calculating capacity retention rate (%), taking out the battery full, standing for 3 hours at normal temperature, and testing full thickness D1The thickness change rate (%) was calculated, and the results are shown in Table 2. The calculation formula used therein is as follows:
thickness change rate (%) - (D)1-D0)/D0X is 100%; capacity retention (%) ═ Q1/Q0×100％。
(2) Normal temperature cycle test at 25 deg.C
Thickness D of full-electricity cell before test0Placing the battery in an environment of (25 +/-3) DEG C, standing for 2 hours, charging the battery to 4.3V according to 1C when the battery core body reaches (25 +/-3) DEG C, charging the battery to a cut-off current of 0.05C at a constant voltage of 4.3V, discharging the battery to 3V at 1C, and recording the initial capacity Q0When the circulation reaches the required times or the capacity decay rate is lower than 80 percent or the thickness exceeds the thickness required by the test, the previous discharge capacity is taken as the capacity Q of the battery2Calculating capacity retention rate (%), taking out the battery full, standing for 3 hours at normal temperature, and testing full thickness D2The thickness change rate (%) was calculated, and the results are shown in Table 2. The calculation formula used therein is as follows:
thickness change rate (%) - (D)2-D0)/D0X is 100%; capacity retention (%) ═ Q2/Q0×100％。
(3) High temperature cycle test at 45 deg.C
Thickness D of full-electricity cell before test0Placing the battery in an environment of (45 +/-3) DEG C, standing for 3 hours, charging the battery 1C to 4.3V when the battery core body reaches (45 +/-3) DEG C, charging the battery to a cut-off current of 0.05C at a constant voltage of 4.3V, discharging the battery to 3V at 1C, and recording the initial capacity Q0And cycling in such a way that when the required number of cycles is reached or the capacity fading rate is lower than 80% or the thickness exceeds the thickness required by the test, the previous discharge capacity is taken as the capacity Q of the battery3Calculating capacity retention rate (%), taking out the battery full charge and core, standing for 3 hr at normal temperature, and testing full charge thickness D3The thickness change rate (%) was calculated, and the results are shown in Table 2. The calculation formula used therein is as follows:
thickness change rate (%) - (D)3-D0)/D0X is 100%; capacity retention (%) ═ Q3/Q0×100％。
(4) High temperature storage experiment at 60 deg.C
The thickness D of the fully charged cell was measured at 25 deg.C0Charging the sorted batteries to 4.3V according to 0.7C, charging to 0.05C of cutoff current at constant voltage of 4.3V, discharging to 3.0V with constant current of 0.5C, charging to 4.3V at 0.7C, charging to 0.05C of cutoff current at constant voltage of 4.3V, standing at 60 deg.C for 14 days, and testing full charge thickness D4The thickness change rate (%) was calculated, and the results are shown in Table 2. The calculation formula used therein is as follows:
thickness change rate (%) - (D)4-D0)/D0×100％。
TABLE 2 comparison of experimental results for batteries of examples 1-14 and comparative examples 1-9
As can be seen from table 2, the batteries prepared in the examples of the present application all achieve better electrical properties, and the specific analysis is as follows:
compared with comparative examples 2-4, the addition of the compound shown in formula 1 can improve the cycle and high-temperature storage performance of the battery, and can give consideration to low-temperature cycle performance; it was found by comparing comparative example 1 with comparative examples 5 to 7 that the addition of the compound represented by formula 2 improves cycle performance and high-temperature storage performance, but deteriorates low-temperature cycle performance; it was found by comparing comparative example 1 with comparative examples 8 to 9 that the addition of the acid anhydride compound can improve the cycle and high-temperature storage performance of the battery, but deteriorate the low-temperature performance.
Through comparative examples 2, 5-7 and examples 1-5, it can be seen that the compound of formula 1 and the compound of formula 2 or the combination of the compound of formula 1 and the acid anhydride compound have better cycle performance and high-temperature storage performance than the single compound of formula 2 or acid anhydride compound, and simultaneously have low-temperature cycle performance.
Through comparison of example 1 and example 6, example 2 and example 7, and example 3 and examples 8-9, respectively, it is found that the cycle and high-temperature storage performance can be further improved and the low-temperature cycle performance can be improved by properly adding an anhydride compound to the compound represented by formula 1 and the compound represented by formula 2; comparing example 9 and example 10, it can be seen that, by appropriately decreasing the content of the compound represented by formula 2, the low-temperature cycle performance can be further improved while the cycle and storage performance are compatible.
By comparing example 11 and example 12 with example 10, it can be found that a plurality of compounds represented by formula 1 or a plurality of compounds represented by formula 2 have more excellent cycle and storage properties while simultaneously achieving a balance between low-temperature cycle properties. By comparing examples 13 and 14 with example 10, it was found that the cycle performance and the storage performance can be further improved and the low-temperature cycle performance can be simultaneously achieved by adding ethylene carbonate or ethylene sulfate to the combination of the compound represented by formula 1, the compound represented by formula 2 and the acid anhydride-based compound.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (11)
1. A lithium ion battery comprising a nonaqueous electrolytic solution including (a) a lithium salt, (b) a nonaqueous organic solvent, and (c) at least one compound represented by formula 1, wherein the nonaqueous electrolytic solution further includes at least one of the following components (d) and (e):
(d) at least one compound represented by the formula 2,
(e) acid anhydride compounds;
in the formula 1, R1、R2Identical or different, independently of one another, from hydrogen, halogen substituted or unsubstituted C1-C6Alkyl, halogen substituted or unsubstituted C2-C5Or halogen substituted or unsubstituted C2-C5Alkynyl of (a);
in formula 2, M1、M2、M3Identical or different, independently of one another, from halogen substituted or unsubstituted C1-C5Alkyl, halogen substituted or unsubstituted C2-C5Or halogen substituted or unsubstituted C2-C5And M is alkynyl, and1、M2、M3at least one of which is selected from halogen substituted or unsubstituted C2-C5Or halogen substituted or unsubstituted C2-C5Alkynyl group of (1).
2. The lithium ion battery according to claim 1, wherein the acid anhydride compound is one or more selected from succinic anhydride, glutaric anhydride, adipic anhydride, pimelic anhydride, phthalic anhydride, maleic anhydride, citraconic anhydride, citric anhydride, and 2, 3-dimethylmaleic anhydride, or is one or more selected from fluoro compounds of the acid anhydride compounds.
3. The lithium ion battery according to claim 1, wherein the compound represented by formula 1 is at least one selected from the following compounds a1 to a 5:
4. the lithium ion battery according to claim 1, wherein the compound represented by formula 2 is at least one selected from the following compounds B1 to B8:
5. the lithium ion battery according to any one of claims 1 to 4, wherein the content of the compound represented by formula 1 is 0.1 to 10 wt% based on the total mass of the nonaqueous electrolytic solution.
6. The lithium ion battery according to any one of claims 1 to 4, wherein the content of the compound represented by formula 2 is 0 to 3 wt% based on the total mass of the nonaqueous electrolytic solution.
7. The lithium ion battery according to claim 6, wherein the content of the compound represented by formula 2 is 0.1 to 3 wt% based on the total mass of the nonaqueous electrolytic solution.
8. The lithium ion battery according to any one of claims 1 to 4, wherein the content of the acid anhydride-based compound is 0 to 2 wt% based on the total mass of the nonaqueous electrolytic solution.
9. The lithium ion battery according to claim 8, wherein the content of the acid anhydride-based compound is 0.1 to 2 wt% based on the total mass of the nonaqueous electrolytic solution.
10. The lithium ion battery of claim 1, wherein the lithium ion battery further comprises a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, and a lithium ion separator;
the positive active material is selected from one or more of layered lithium transition metal composite oxides, lithium manganate and lithium cobaltate mixed ternary materials; the chemical formula of the layered lithium transition metal composite oxide is Li1+xNiyCozM(1-y-z)Q2Wherein x is more than or equal to-0.1 and less than or equal to 1; y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, and y + z is more than or equal to 0 and less than or equal to 1; wherein M is one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo and Zr; q is one or more of O, F, P, S;
the negative active material is selected from one or more of carbon materials, silicon-based materials, tin-based materials or alloy materials corresponding to the carbon materials, the silicon-based materials and the tin-based materials.
11. The lithium ion battery of claim 1 or 10, wherein the operating voltage of the lithium ion battery is in the range of 4.2V and above.
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