CN113812027B - Electrolyte, electrochemical device and electronic device comprising same - Google Patents

Electrolyte, electrochemical device and electronic device comprising same Download PDF

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CN113812027B
CN113812027B CN202080034030.8A CN202080034030A CN113812027B CN 113812027 B CN113812027 B CN 113812027B CN 202080034030 A CN202080034030 A CN 202080034030A CN 113812027 B CN113812027 B CN 113812027B
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substituted
electrolyte
group
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compound
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CN113812027A (en
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熊亚丽
唐超
栗文强
王荣
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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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
    • 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
    • H01M10/42—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
    • 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

Abstract

The present application relates to an electrolyte, and an electrochemical device and an electronic device including the same. The electrolyte comprises a compound of formula I, wherein R 1 、R 2 And R is 3 Each independently selected from the group consisting of hydrogen, halogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, and substituted or unsubstituted heteroatom-containing group; wherein, when substituted, the substituent is selected from halogen; the heteroatom includes at least one of O, S, P, N, si and B; r is R 1 、R 2 And R is 3 Having an unsaturated functional group. The electrolyte can improve the high-temperature cycle and high-temperature storage performance of the high-voltage battery.

Description

Electrolyte, electrochemical device and electronic device comprising same
Technical Field
The present disclosure relates to the field of energy storage technologies, and in particular, to an electrolyte, and an electrochemical device and an electronic device including the electrolyte.
Background
The lithium ion battery has the advantages of high energy density, long cycle life, low self-discharge rate, no memory effect, stable discharge voltage, quick charge and discharge, environmental protection and the like, and is now becoming a main unit of 3C portable electronic equipment. However, with the development of society, requirements for lithium ion batteries are becoming higher and higher, such as high energy density, rapid charging, and the main direction of research by many scientific research institutions and battery companies.
Since the power and energy that can be provided by a lithium battery are proportional to the operating voltage, increasing the voltage of the battery is the simplest and most straightforward method to solve the above-mentioned problems. However, when the operating voltage is increased, there is a problem in that the electrode material structure collapses, the organic carbonate is easily oxidized and decomposed to generate gas, and the internal pressure of the battery increases, resulting in rapid deterioration of the electrical properties. Therefore, research into preparing lithium ion electrolytes capable of withstanding high voltages is of great importance for developing high energy density batteries.
Disclosure of Invention
The present application aims to provide an electrolyte and an electrochemical device comprising the same to solve the problems of cycle and high-temperature storage of a high-voltage lithium ion battery. The electrolyte provided by the application can obviously improve the high-temperature circulation and high-temperature storage performance of the high-voltage battery.
In a first aspect of the present application, there is provided an electrolyte comprising a compound of formula I,
in the formula I, R 1 、R 2 And R is 3 Each independently selected from the group consisting of hydrogen, halogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, and substituted or unsubstituted heteroatom-containing group; wherein, when substituted, the substituent is selected from halogen; the heteroatom includes at least one of O, S, P, N, si and B; r is R 1 、R 2 And R is 3 Having an unsaturated functional group.
According to some embodiments of the present application, the unsaturated functional group comprises at least one of a carbon-carbon double bond, a carbon-carbon triple bond.
According to some embodiments of the present application, in formula I, R 1 、R 2 And R is 3 Each independently selected from hydrogen, halogen, substituted or unsubstituted C 1- C 10 Alkyl, substituted or unsubstituted C 2- C 10 Alkenyl, substituted or unsubstituted C 2- C 10 Alkynyl and substituted or unsubstituted C 1- C 10 Containing hetero atom groups.
According to some embodiments of the present application, in formula I, the heteroatom-containing groups include ester groups, ketone groups, aldehyde groups, amino groups, amine groups, borate groups, alkoxy groups, thiol groups, and cyano groups.
According to some further preferred embodiments of the present application, the compound of formula I is selected from one or more of the following compounds:
according to some embodiments of the present application, the mass percentage of the compound of formula I is 0.01% to 2% based on the mass of the electrolyte.
According to some embodiments of the present application, the electrolyte further includes at least one of a polynitrile compound having a cyano group number of not less than 2, a sulfonate compound, and a boron-containing lithium salt compound.
According to some embodiments of the present application, the amount of cyano groups is 0.10% -15% by mass of the polynitrile compound having an amount of cyano groups of 2 or more, based on the mass of the electrolyte.
According to some embodiments of the present application, the sulfonate compound is present in an amount of 0.10% to 10% by mass based on the mass of the electrolyte.
According to some embodiments of the present application, the mass percentage of the boron-containing lithium salt compound is 0.01% to 5% based on the mass of the electrolyte.
According to some preferred embodiments of the present application, the polynitrile compound having a cyano number of not less than 2 comprises at least one of compounds represented by the formulae (II) to (V):
N≡C-R 21 -C≡N
formula (II)
Wherein R is 21 Selected from substituted or unsubstituted C 1 ～C 12 Alkylene, substituted or unsubstituted C 1 ～C 12 An alkyleneoxy group; r is R 31 And R is 32 Each independently selected from a single bond or substituted or unsubstituted C 1 ～C 12 An alkylene group; r is R 41 、R 42 And R is 43 Each independently selected from single bond, substituted or unsubstituted C 1 ～C 12 Alkylene, substituted or unsubstituted C 1 ～C 12 An alkyleneoxy group; r is R 51 Selected from substituted or unsubstituted C 1 ～C 12 Alkylene, substituted or unsubstituted C 2 ～C 12 Alkenylene, substituted or unsubstituted C 6～ C 26 Arylene, substituted or unsubstituted C 2- C 12 A heterocyclylene group; wherein when substituted, the substituent is a halogen atom.
According to some further preferred embodiments of the present application, the polynitrile compound having a cyano number of not less than 2 includes at least one of the following:
According to some embodiments of the present application, the sulfonate compound is selected from cyclic sulfonate compounds comprising one or more of cyclic monosulfonates and cyclic disulfonates.
According to some preferred embodiments of the present application, the sulfonate compound comprises at least one of the compounds represented by formula VI:
in formula VI, A and BEach independently represents an alkylene or fluoroalkylene group, and L represents a single bond or-OSO 2 -a radical.
According to some embodiments of the present application, A and B each independently represent C 1 -C 8 Alkylene or C of (2) 1 -C 8 Is a fluorinated alkylene group of (2).
According to some preferred embodiments of the present application, the compound of formula VI includes a cyclic monosulfonate compound represented by formula VI-1:
wherein R is 611 And R is 612 Each independently represents a hydrogen atom, a fluorine atom or C 1 -C 4 Alkyl, and n is 1, 2, 3 or 4;
according to some further preferred embodiments of the present application, the compound represented by formula VI includes a cyclic disulfonate compound represented by the following formula VI-2.
Wherein R is 621 And R is 622 Each independently represents an atom, a fluorine atom or C 1 -C 4 Alkyl, and n is 1, 2, 3 or 4, and if n is 2 or more, a plurality of R 623 May be the same or different from each other, and the plurality of R624 may be the same or different from each other.
According to some further preferred embodiments of the present application, the cyclic sulfonate comprises at least one of 1, 3-propane sultone, 1, 2-propane sultone, 1, 4-butane sultone, 1, 2-butane sultone, 1, 3-butane sultone, 2, 4-butane sultone, 1, 3-pentane sultone, methane disulfonic acid methylene ester and methane disulfonic acid ethylene ester.
According to some embodiments of the present application, the boron-containing lithium salt compound comprises a compound of formula VII:
wherein M is + Represents an alkali metal cation.
According to some embodiments of the present application, the electrolyte further comprises a cyclic carbonate compound.
According to some embodiments of the present application, the cyclic carbonate comprises at least one of a fluorinated cyclic carbonate and/or an unsaturated cyclic carbonate.
According to some embodiments of the present application, the fluorinated cyclic carbonate includes a fluoride of a cyclic carbonate having an alkylene group of 2 to 6 carbon atoms.
According to some embodiments of the present application, the fluorinated cyclic carbonate includes at least one of fluoroethylene carbonate, 4-difluoroethylene carbonate, 4, 5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4, 5-difluoro-4-methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, 4-difluoro-5-methylethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene carbonate, 4- (trifluoromethyl) -ethylene carbonate, 4- (fluoromethyl) -4-fluoroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4-fluoro-4, 5-dimethylethylene carbonate, 4, 5-difluoro-4, 5-dimethylethylene carbonate, and 4, 4-difluoro-5, 5-dimethylethylene carbonate.
In a second aspect of the present application, there is also provided an electrochemical device comprising a positive electrode, a negative electrode and an electrolyte according to the present application.
According to some embodiments, the positive electrode includes a current collector, and an active material layer and an insulating layer disposed on a surface of the current collector.
In a third aspect of the present application, the present application further provides an electronic device comprising the electrochemical device according to the second aspect of the present application.
The electrolyte and the electrochemical device comprising the electrolyte can remarkably improve the high-temperature circulation and high-temperature storage performance of a high-voltage battery.
Drawings
Fig. 1 shows a positive electrode of an electrochemical device according to an embodiment of the present application, wherein the positive electrode includes a positive electrode current collector (1), a first surface positive electrode active material layer (2), a second surface active material layer (3), and an insulating layer (4).
Detailed Description
The present application is further described below in conjunction with the detailed description. It should be understood that these specific embodiments are presented by way of example only and are not intended to limit the scope of the present application.
For simplicity, only a few numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form a range not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and any upper limit may be combined with any other upper limit to form a range not explicitly recited. Furthermore, each separately disclosed point or individual value may itself be combined as a lower limit or upper limit with any other point or individual value or with other lower limit or upper limit to form a range not explicitly recited.
In the description herein, unless otherwise indicated, "above" and "below" are intended to include the present number, and the meaning of "several" in "one or several" means two or more.
Unless otherwise indicated, terms used in the present application have well-known meanings commonly understood by those skilled in the art. Unless otherwise indicated, the numerical values of the parameters set forth in this application may be measured by various measurement methods commonly used in the art (e.g., may be tested according to the methods set forth in the examples of this application).
The term "about" is used to describe and illustrate minor variations. When used in connection with an event or circumstance, the terms can refer to instances where the event or circumstance occurs precisely and instances where it occurs to the close approximation. For example, when used in connection with a numerical value, the term can refer to a range of variation of less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. Additionally, amounts, ratios, and other numerical values are sometimes presented herein in a range format. It is to be understood that such range format is used for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.
The term "hydrocarbyl" encompasses alkyl, alkenyl, alkynyl.
The term "alkyl" is intended to be a straight chain saturated hydrocarbon structure having from 1 to 20 carbon atoms. "alkyl" is also intended to be a branched or cyclic hydrocarbon structure having 3 to 20 carbon atoms. When alkyl groups having a specific carbon number are specified, all geometric isomers having that carbon number are contemplated; thus, for example, reference to "butyl" is intended to include n-butyl, sec-butyl, isobutyl, tert-butyl and cyclobutyl; "propyl" includes n-propyl, isopropyl and cyclopropyl. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, methylcyclopentyl, ethylcyclopentyl, n-hexyl, isohexyl, cyclohexyl, n-heptyl, octyl, cyclopropyl, cyclobutyl, norbornyl, and the like.
The term "alkenyl" refers to a monovalent unsaturated hydrocarbon group that may be straight or branched and has at least one and typically 1, 2, or 3 carbon-carbon double bonds. Unless otherwise defined, the alkenyl groups typically contain from 2 to 20 carbon atoms and include, for example, -C2-4 alkenyl, -C2-6 alkenyl, and-C2-10 alkenyl. Representative alkenyl groups include, for example, vinyl, n-propenyl, isopropenyl, n-but-2-enyl, but-3-enyl, n-hex-3-enyl, and the like.
The term "alkynyl" refers to a monovalent unsaturated hydrocarbon group that may be straight or branched and has at least one and typically 1,2, or 3 carbon-carbon triple bonds. Unless otherwise defined, the alkynyl group typically contains 2 to 20 carbon atoms and includes, for example, C2-4 alkynyl, -C3-6 alkynyl, and-C3-10 alkynyl. Representative alkynyl groups include, for example, ethynyl, prop-2-ynyl (n-propynyl), n-but-2-ynyl, n-hex-3-ynyl, and the like.
The term "alkylene" means a divalent saturated hydrocarbon group that may be straight or branched. Unless otherwise defined, the alkylene groups typically contain from 2 to 10 carbon atoms and include, for example, -C2-3 alkylene and-C2-6 alkylene-. Representative alkylene groups include, for example, methylene, ethane-1, 2-diyl ("ethylene"), propane-1, 2-diyl, propane-1, 3-diyl, butane-1, 4-diyl, pentane-1, 5-diyl, and the like.
As used herein, the content of each component is based on the total weight of the electrolyte.
1. Electrolyte solution
The present application provides an electrolyte comprising a compound of formula I.
The inventors of the present application have found that the compounds of formula I can improve high temperature cycle and high temperature storage properties. This is because the non-common electron pair on N in the compound of formula I can stabilize the anions of the salt in the electrolyte, sulfur can react with active oxygen, inhibit the electrolyte from decomposing to form an interface film rich in sulfur, promote the mechanical stability of the interface film, and improve the cycle performance; in addition, the oxidation potential of the compound shown in the formula I is lower, a solid electrolyte phase interface film (namely CEI film) can be formed on the surface of the positive electrode preferentially, the positive electrode is protected, chemical gas production caused by contact of the positive electrode material and electrolyte is reduced, and the cycle and high-temperature storage performance are improved. Meanwhile, the compound of the formula I can widen the oxidation window of the solvent, improve the oxidation resistance of the solvent and improve the high-temperature performance.
1. Compounds of formula I
In the formula I, R 1 、R 2 And R is 3 Each independently selected from the group consisting of hydrogen, halogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, and substituted or unsubstituted heteroatom-containing group; wherein, when substituted, the substituent is selected from halogen; the hetero atomComprises at least one of O, S, P, N, si and B; r is R 1 、R 2 And R is 3 Having an unsaturated functional group.
According to some embodiments of the present application, in some examples, R 1 Having unsaturated functional groups. In some embodiments, R 2 Having unsaturated functional groups. In some embodiments, R 3 Having unsaturated functional groups.
According to some preferred embodiments of the present application, the unsaturated functional group is selected from the group consisting of a carbon-carbon double bond and a carbon-carbon triple bond. In some embodiments, the unsaturated functional group is a carbon-carbon double bond. In some embodiments, the unsaturated functional group is a carbon-carbon triple bond.
According to some embodiments of the present application, in formula I, R 1 、R 2 And R is 3 Each independently selected from hydrogen, halogen, substituted or unsubstituted C 1- C 10 Alkyl, substituted or unsubstituted C 2- C 10 Alkenyl, substituted or unsubstituted C 2- C 10 Alkynyl and substituted or unsubstituted C 1- C 10 Containing hetero atom groups.
According to some embodiments of the present application, in formula I, the heteroatom-containing groups include ester groups, ketone groups, aldehyde groups, amino groups, amine groups, borate groups, alkoxy groups, thiol groups, and cyano groups.
According to some further embodiments of the present application, the compound of formula I comprises at least one of the following compounds:
according to some embodiments of the present application, the mass percentage of the compound of formula I is 0.01% to 2% based on the mass of the electrolyte. According to some embodiments of the present application, the mass percentage of the compound of formula I in the electrolyte is 0.1% to 1.5%. According to some preferred embodiments of the present application, the mass percentage of the compound of formula I in the electrolyte is 0.3% to 1.0%.
2. Additive agent
According to some embodiments of the present application, the electrolyte may further comprise an additive. According to some embodiments, the additive comprises at least one of a polynitrile compound, a sulfonate compound, a cyclic carbonate compound, and a boron-containing lithium salt compound having a nitrile number of greater than or equal to 2.
(1) Polynitrile compound with nitrile number more than or equal to 2
According to the application, the electrolyte can further comprise polynitrile compounds with nitrile number more than or equal to 2, wherein the mass percentage of the polynitrile compounds with nitrile number more than or equal to 2 in the electrolyte is as follows: 0.10% -15%.
According to some embodiments of the present application, the polynitrile compound having a cyano number of not less than 2 comprises at least one of compounds represented by formulas (II) to (V):
N≡C-R 21 -C≡N
formula (II)
Wherein R is 21 Selected from substituted or unsubstituted C 1 ～C 12 Alkylene, substituted or unsubstituted C 1 ～C 12 An alkyleneoxy group; r is R 31 And R is 32 Each independently selected from a single bond or substituted or unsubstituted C 1 ～C 12 An alkylene group; r is R 41 、R 42 And R is 43 Each independently selected from single bond, substituted or unsubstituted C 1 ～C 12 Alkylene, substituted or unsubstituted C 1 ～C 12 An alkyleneoxy group; r is R 51 Selected from substituted or unsubstituted C 1 ～C 12 Alkylene, substituted or unsubstituted C 2 ～C 12 Alkenylene, substituted or unsubstituted C 6～ C 26 Arylene, substituted or unsubstituted C 2- C 12 A heterocyclylene group; wherein when substituted, the substituent is a halogen atom.
According to some embodiments of the present application, the polynitrile compound having a cyano number of 2 or more includes at least one of the following:
(2) Sulfonate compounds
According to the application, the electrolyte may further comprise a sulfonate compound. According to some embodiments, the mass percentage of the sulfonate compound in the electrolyte is: 0.10% -10%.
According to some embodiments of the present application, the sulfonate compound comprises one or more of a cyclic monosulfonate, a cyclic disulfonate.
According to some embodiments of the present application, the sulfonate compound comprises at least one of the compounds represented by formula vi:
wherein A and B each independently represent an alkylene or fluoroalkylene group, and L represents a single bond or-OSO 2 -a radical.
According to some embodiments of the present application, in formula vi, the alkylene group has a carbon number of 1 to 8, preferably 1 to 6, and more preferably 1 to 4. Fluoroalkylene means that at least one hydrogen atom of an unsubstituted alkylene group is replaced with a fluorine atom. In formula VI, the number of carbon atoms of the fluorinated alkylene group is, for example1 to 8, preferably 1 to 6, and more preferably 1 to 4. the-OSO 2 The radical may be in any orientation.
In formula VI, if L is a single bond, the cyclic sulfonate is a cyclic monosulfonate, which is a compound represented by the following formula VI-1.
Wherein R is 611 And R is 612 Each independently represents a hydrogen atom, a fluorine atom or an alkyl group having 1 to 4 carbon atoms, and n is 1, 2, 3 or 4.
In formula VI, if L is-OSO 2 -group, then the cyclic sulfonate is a cyclic disulfonate, and the cyclic disulfonate is preferably a compound represented by the following formula vi-2.
Wherein R is 621 And R is 622 Each independently represents a hydrogen atom, a fluorine atom or an alkyl group having 1 to 4 carbon atoms, and n is 1, 2, 3 or 4, and if n is 2 or more, a plurality of R 623 May be the same or different from each other, and a plurality of R 624 May be the same or different from each other.
Examples of the cyclic sulfonate include monosulfonates (when X in formula VI is a single bond) such as 1, 3-propane sultone, 1, 2-propane sultone, 1, 4-butane sultone, 1, 2-butane sultone, 1, 3-butane sultone, 2, 4-butane sultone, 1, 3-pentane sultone and disulfonate (when X in formula VI is-OSO) 2 -methyl-and ethylene methane disulfonate). Among them, 1, 3-Propane Sultone (PS), 1, 4-Butane Sultone (BS) and Methylene Methane Disulfonate (MMDS) are preferable in view of the effect of forming a film, availability easiness and cost. In particular, the cyclic disulfonate has a characteristic of easily forming a film having excellent quality on the anode.
The cyclic sulfonate compound is further added into the electrolyte, so that the high-temperature cycle and high-temperature storage performance of the lithium ion battery can be further improved by improving the lithium ion, and the floating charge performance can be further improved; the cyclic sulfate compound can form an interfacial film with excellent mechanical stability at the positive electrode and the negative electrode, and the interfacial film can obviously inhibit side reactions at the positive electrode and the negative electrode, so that the thermal stability and the mechanical stability of the interfacial film are further improved, and the cycle performance and the high-temperature storage performance are improved; in particular, the cyclic disulfonate has a characteristic of easily forming a film having excellent quality on the anode, and the use in combination with the cyclic monosulfonate can bring about more excellent improvement.
(3) Cyclic carbonate compounds
According to the present application, the electrolyte may further include a cyclic carbonate compound in an amount of 0.01 to 10% by mass in the electrolyte.
According to some embodiments of the present application, the cyclic carbonate compound includes at least one of a fluorinated cyclic carbonate and/or an unsaturated cyclic carbonate. According to some embodiments, the fluorinated cyclic carbonate is selected from the group consisting of fluorides of cyclic carbonates of alkylene groups having 2 to 6 carbon atoms. Examples of the fluorinated cyclic carbonates include, but are not limited to, fluoroethylene carbonate, 4-difluoroethylene carbonate, 4, 5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4, 5-difluoro-4-methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, 4-difluoro-5-methylethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene carbonate, 4- (trifluoromethyl) -ethylene carbonate, 4- (fluoromethyl) -4-fluoroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4-fluoro-4, 5-dimethylethylene carbonate, 4, 5-difluoro-4, 5-dimethylethylene carbonate and 4, 4-difluoro-5, 5-dimethylethylene carbonate.
(4) Boron-containing lithium salt compound
According to the present application, the electrolyte may further comprise a boron-containing lithium salt compound, preferably a metal tetraborate compound. In some embodiments, the content of the boron-containing lithium salt compound is 0.01wt% to 1wt% based on the total weight of the electrolyte.
In some embodiments of the present application, the boron-containing lithium salt compound is a metal tetraborate compound, which may be specifically selected from the group consisting of compounds represented by formula VII:
wherein M is + Represents an alkali metal cation. Examples of alkali metal cations include, but are not limited to, lithium ion, sodium ion, potassium ion, cesium ion.
In some embodiments of the present application, the compound of formula VII is selected from one or more of the following compounds:
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(5) In addition, the electrolyte may further include fluoropyridine such as: difluoropyridine, pentafluoropyridine, and the like.
3. Lithium salt
The electrolyte lithium salt used in the electrolyte of the present application is selected from one or more of inorganic lithium salt and organic lithium salt.
According to some embodiments of the present application, the lithium salt is selected from lithium hexafluorophosphate (LiPF) 6 ) Lithium tetrafluoroborate (LiBF 4), lithium difluorosulfonimide (LiFSI), lithium bistrifluoromethanesulfonimide (LiTFSI), lithium difluorophosphate (LiPO) 2 F 2 ) Further preferably, the lithium salt is selected from lithium hexafluorophosphate (LiPF) 6 )。
4. Solvent(s)
The solvent used in the electrolyte of the present application may be any nonaqueous solvent known in the art that can be used as a solvent for the electrolyte.
In some embodiments of the present application, the nonaqueous solvent includes, but is not limited to, cyclic carbonates, chain carbonates, cyclic carboxylates, chain carboxylates, cyclic ethers, chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and aromatic fluorine-containing solvents.
In some embodiments of the present application, cyclic carbonates include, but are not limited to, ethylene carbonate (ethylene carbonate, EC), propylene carbonate (propylene carbonate, PC), and butylene carbonate. In some embodiments, the cyclic carbonate has 3 to 6 carbon atoms.
In some embodiments of the present application, the chain carbonates include, but are not limited to, dimethyl carbonate, methylethyl carbonate, diethyl carbonate (diethyl carbonate, DEC), methyl n-propyl carbonate, ethyl n-propyl carbonate, di-n-propyl carbonate, and the like, as the chain carbonate substituted with fluorine, for example, bis (fluoromethyl) carbonate, bis (difluoromethyl) carbonate, bis (trifluoromethyl) carbonate, bis (2-fluoroethyl) carbonate, bis (2, 2-difluoroethyl) carbonate, bis (2, 2-trifluoroethyl) carbonate, 2-fluoroethyl methyl carbonate, 2-difluoroethyl methyl carbonate, and 2, 2-trifluoroethyl methyl carbonate.
In some embodiments of the present application, cyclic carboxylic acid esters include, but are not limited to, gamma-butyrolactone and gamma-valerolactone. In some embodiments, a portion of the hydrogen atoms of the cyclic carboxylic acid ester may be substituted with fluorine.
In some embodiments of the present application, the chain carboxylic acid esters include, but are not limited to, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate, and ethyl pivalate. In some embodiments, a portion of the hydrogen atoms of the chain carboxylate may be substituted with fluorine. In some embodiments, the fluoro-substituted chain carboxylic acid esters include, but are not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and 2, 2-trifluoroethyl trifluoroacetate.
In some embodiments of the present application, cyclic ethers include, but are not limited to, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, 2-methyl-1, 3-dioxolane, 4-methyl-1, 3-dioxolane, 1, 3-dioxane, 1, 4-dioxane, and dimethoxypropane.
In some embodiments of the present application, the chain ethers include, but are not limited to, dimethoxymethane, 1-dimethoxyethane, 1, 2-dimethoxyethane, diethoxymethane, 1-diethoxyethane, 1, 2-diethoxyethane, ethoxymethoxymethane, 1-ethoxymethoxyethane, and 1, 2-ethoxymethoxyethane.
In some embodiments of the present application, the phosphorus-containing organic solvents include, but are not limited to, trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tris (2, 2-trifluoroethyl) phosphate, and tris (2, 3-pentafluoropropyl) phosphate.
In some embodiments of the present application, the sulfur-containing organic solvent includes, but is not limited to, sulfolane, 2-methylsulfonic acid, 3-methylsulfonic acid, dimethyl sulfone, diethyl sulfone, ethyl methyl sulfone, methyl propyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate, and dibutyl sulfate. In some embodiments, a portion of the hydrogen atoms of the sulfur-containing organic solvent may be replaced with fluorine.
In some embodiments of the present application, aromatic fluorine-containing solvents include, but are not limited to, fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and trifluoromethylbenzene.
In some embodiments of the present application, the solvent used in the electrolyte of the present application includes one or more of the solvents described above. In some embodiments, the solvent used in the electrolyte of the present application is selected from the group consisting of cyclic carbonates, chain carbonates, cyclic carboxylates, chain carboxylates, and combinations thereof. In some embodiments, the solvent used in the electrolyte of the present application comprises an organic solvent selected from the group consisting of: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, n-propyl acetate, ethyl acetate, and combinations thereof.
In some embodiments, the solvent used in the electrolyte of the present application is selected from the group consisting of: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, gamma-butyrolactone, and combinations thereof.
In some preferred embodiments, the solvent used in the electrolyte of the present application is a combination of ethylene carbonate, propylene carbonate, diethyl carbonate.
2. Electrochemical device
The electrochemical device of the present application refers to any device capable of electrochemical reaction, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery. In some embodiments, the electrochemical device of the present application comprises a positive electrode having a positive electrode active material capable of occluding and releasing metal ions; a negative electrode having a negative electrode active material capable of occluding and releasing metal ions; and the electrolyte of the present application.
1. Electrolyte solution
The electrolyte used in the lithium ion battery of the present application is any of the electrolytes described above of the present application. In addition, the electrolyte used in the lithium ion battery of the present application may also include other electrolytes within the scope not departing from the gist of the present application.
2. Electrode
(1) Negative electrode
The anode of the electrochemical device according to the embodiment of the present application includes a current collector and an anode active material layer formed on the current collector, the anode active material layer including an anode active material, which may include a material that reversibly intercalates/deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping/deintercalating lithium, or a transition metal oxide, such as Si, siOx, or the like. The material that reversibly intercalates/deintercalates lithium ions may be a carbon material. The carbon material may be any carbon-based anode active material commonly used in lithium ion rechargeable electrochemical devices. Examples of carbon materials include crystalline carbon, amorphous carbon, and combinations thereof. The crystalline carbon may be amorphous or plate-shaped, platelet-shaped, spherical or fibrous natural or artificial graphite. Amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonized product, fired coke, and the like. Both low crystalline carbon and high crystalline carbon may be used as the carbon material. As the low crystalline carbon material, soft carbon and hard carbon may be generally included. As the high crystalline carbon material, natural graphite, crystalline graphite, pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microbeads, mesophase pitch, and Gao Wenduan char (e.g., petroleum or coke derived from coal tar pitch) may be generally included.
The negative electrode active material layer contains a binder, and the binder may include various binder polymers such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an ethyleneoxy-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like, but is not limited thereto.
The anode active material layer further includes a conductive material to improve electrode conductivity. Any conductive material may be used as the conductive material as long as it does not cause chemical change. Examples of conductive materials include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, and the like; metal-based materials such as metal powders or metal fibers including copper, nickel, aluminum, silver, and the like; conductive polymers such as polyphenylene derivatives and the like; or mixtures thereof. The current collector may be copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.
(2) Positive electrode
According to some embodiments, an electrochemical device of the present application includes a current collector, and an active material layer and an insulating layer disposed on a surface of the current collector.
According to some embodiments, the positive electrode comprises: the positive electrode current collector may be Al, but is not limited thereto; a positive electrode active material layer; and an insulating layer disposed on the positive electrode current collector.
According to some embodiments, the insulating layer satisfies at least one of the conditions (a) to (c): (a) A gap is formed between the insulating layer and the positive electrode active material layer, and the width of the gap is 0mm to 2mm; (b) The insulating layer includes inorganic particles including at least one of aluminum oxide, silicon dioxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium dioxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate; (c) The insulating layer includes a polymer including at least one of a homopolymer of vinylidene fluoride, a copolymer of hexafluoropropylene, polystyrene, polyphenylacetylene, sodium polyvinyl, potassium polyvinyl, polymethyl methacrylate, polyethylene, polypropylene, or polytetrafluoroethylene.
The materials, compositions, and methods of making the positive electrode used in the electrochemical devices of the present application may include any of the techniques disclosed in the prior art.
In some embodiments, the positive electrode active material includes, but is not limited to, sulfides, phosphate compounds, and lithium transition metal complex oxides. In some embodiments, the positive electrode active material includes a lithium transition metal compound having a structure capable of releasing and inserting lithium ions.
In some embodiments, the positive electrode comprises any of the structures disclosed in the prior art. In some embodiments, the positive electrode is made by forming a positive electrode material with a positive electrode active material layer including a lithium transition metal-based compound powder and a binder on a current collector.
In some embodiments, the positive electrode active material layer is typically fabricated by: the positive electrode material and the binder (if necessary, a conductive material, a thickener, and the like) are dry-mixed to form a sheet, the obtained sheet is pressed against the positive electrode current collector, or these materials are dissolved or dispersed in a liquid medium to form a slurry, and the slurry is applied to the positive electrode current collector and dried. In some embodiments, the positive electrode active material layer comprises any of the materials disclosed in the prior art.
3. Diaphragm
In some embodiments, the electrochemical device of the present application is provided with a separator between the positive electrode and the negative electrode to prevent short circuit. The material and shape of the separator used in the electrochemical device of the present application are not particularly limited, and may be any of the techniques disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic, etc., formed from a material that is stable to the electrolyte of the present application.
For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer is at least one selected from polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric or a polypropylene-polyethylene-polypropylene porous composite membrane can be selected.
The surface treatment layer is provided on at least one surface of the base material layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer formed by mixing a polymer and an inorganic substance.
The inorganic layer comprises inorganic particles and a binder, wherein the inorganic particles are selected from one or a combination of more of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate. The binder is selected from one or more of polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxy, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
The polymer layer contains a polymer, and the material of the polymer is at least one selected from polyamide, polyacrylonitrile, acrylic polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl alkoxy, polyvinylidene fluoride and poly (vinylidene fluoride-hexafluoropropylene).
3. Electronic device
The electrolyte according to the present application can suppress an increase in the direct-current internal resistance of an electrochemical device, so that the electrochemical device manufactured thereby is suitable for various fields of electronic equipment or devices.
The electronic apparatus or device of the present application is not particularly limited. In some embodiments, the electronic devices of the present application include, but are not limited to, notebook computers, pen-input computers, mobile computers, electronic book players, cellular telephones, portable fax machines, portable copiers, portable printers, headsets, video recorders, liquid crystal televisions, hand-held cleaners, portable CD players, mini-compact discs, transceivers, electronic notepads, calculators, memory cards, portable audio recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting fixtures, toys, gaming machines, watches, power tools, flashlights, cameras, home-use large storage batteries, lithium ion capacitors, and the like.
The following describes the technical solution of the present application by way of specific embodiments:
1. battery preparation
1) Preparation of electrolyte: at the water content<In a 10ppm argon atmosphere glove box, ethylene carbonate (abbreviated as EC), propylene carbonate (abbreviated as PC) and diethyl carbonate (abbreviated as DEC) were uniformly mixed in a mass ratio of 3:3:4, and then a sufficiently dried lithium salt LiPF was prepared 6 (1M) dissolving in the nonaqueous solvent, and finally adding a certain mass of additive to prepare the electrolyte in the embodiment.
Wherein the additive in comparative example 3 is
2) Preparing a positive electrode plate: the positive electrode active material LCO (LiCoO) 2 ) Fully stirring and mixing conductive carbon black and a binder polyvinylidene fluoride (PVDF) in a weight ratio of 97.1:1.3:1.6 in a proper amount of N-methylpyrrolidone (NMP) solvent to form uniform anode slurry; coating the slurry on an Al foil of a positive electrode current collector, drying, cold pressing to obtain a positive electrode plate, wherein the compacted density of the positive electrode is 4.15g/cm 3 。
3) Preparing a negative electrode plate: fully stirring and mixing negative electrode active material graphite, binder Styrene Butadiene Rubber (SBR) and thickener sodium carboxymethylcellulose (CMC) in a proper amount of deionized water solvent according to a weight ratio of 97.7:1.3:1.0 to form uniform negative electrode slurry; coating the slurry on a Cu foil of a negative electrode current collector, drying, cold pressing to obtain a negative electrode plate, wherein the compacted density of the negative electrode is 1.75g/cm 3 。
4) Preparation of a separator film
A Polyethylene (PE) separator film 7 μm thick was selected.
5) Preparation of a lithium ion battery: sequentially stacking the positive electrode plate, the diaphragm and the negative electrode plate, enabling the diaphragm to be positioned between the positive electrode plate and the negative electrode plate to play a role in isolation, and then winding to obtain a bare cell; and placing the bare cell in an outer packaging foil, injecting the prepared electrolyte into the dried cell, and performing the procedures of vacuum packaging, standing, formation, shaping and the like to prepare the lithium ion cell.
2. Test method
1) Expansion rate of 85 ℃ storage battery
The cell was charged to 4.5v at 25C at 0.5C and to 0.05C at constant voltage at 4.5v, the thickness of the cell was measured and recorded as H11 with a micrometer, and placed in an oven at 85℃, and after 12 hours the thickness of the cell was measured and recorded with a micrometer as H12.
Thickness expansion ratio= (H12-H11)/h11×100%
2) High temperature cycle test of lithium ion battery
And placing the lithium ion battery in a 45 ℃ incubator, and standing for 30 minutes to keep the lithium ion battery at a constant temperature. Charging the lithium ion battery with constant temperature to 4.5V at 45 ℃ under constant current of 0.2C, charging to 0.05C under constant voltage of 4.5V, standing for 5 minutes, discharging to 3.0V under constant current of 0.2C, and standing for 5 minutes; then charging to 4.15V with a constant current of 1.3C, and then charging to 1C with a constant voltage of 4.15V; then charging to 4.25V with 1C constant current, and then charging to 0.8C with 4.25V constant voltage; charging to 4.5V with constant current of 0.8C, and charging to 0.05C with constant voltage of 4.5V; standing for 5 minutes; then discharging at a constant current of 1C until the voltage is 3.0V, and standing for 3 minutes; this is a charge-discharge cycle. The capacity retention after N cycles of the battery was calculated by thus charging/discharging.
Capacity retention (%) =discharge capacity of nth cycle/discharge capacity of 1 st cycle×100% after N cycles of lithium ion battery.
3) DC impedance DCR (0 ℃) test for lithium ion battery
Standing the lithium ion battery in a high-low temperature box at 0 ℃ for 1 hour to keep the lithium ion battery constant temperature; charging to 4.2V with 0.5C constant current, charging to 4.5V with 0.3C constant current, charging to 0.02C with 4.5V constant voltage, and standing for 30 min; then discharging to 3.4V with constant current of 0.1C, and standing for 30 minutes, wherein the capacity is taken as a reference. Charging to 4.2V at 0 deg.C under constant current of 0.5C, charging to 4.5V at constant current of 0.3C, charging to 0.02C under constant voltage of 4.5V, and standing for 30 min; the constant current discharge of 0.1C was carried out for 60min (calculated by the actual capacity obtained in the previous step), and the voltage at this time was recorded as V 1 The method comprises the steps of carrying out a first treatment on the surface of the Then 1C constant current discharge is carried out for 1s (the capacity is calculated by the battery label capacity), and the voltage at the moment is recorded as V 2 The 20% soc state of the battery is calculated as corresponding to the dc impedance.
20% soc dc impedance= (V 1 -V 2 )/1C。
4) Hot box test
At 25 ℃, the lithium ion battery is charged to 4.5v at a constant current of 0.7C and charged to a constant voltage of 4.5v at a current of 0.05C. The battery was placed in a high temperature box, heated to 135 ℃ with a temperature rise rate of 5±2 ℃/min, and then held for 1 hour, and the voltage, temperature, and change in the temperature of the hot box were recorded. The battery passes the test without ignition, explosion and smoking. Each group was tested for 10 cells and the number of cells passing the test was recorded.
5) 45 ℃ float charge test for lithium ion battery
Charging the battery to 4.15V at 25 ℃ with a constant current of 1.3C, and then charging the battery to 1C with a constant voltage of 4.15V; charging to 4.25V at a constant current of 1C, and then charging to 0.8 at a constant voltage of 4.25V; charging to 4.5V with constant current of 0.8C, and charging to 0.05C with constant voltage of 4.5V; the thickness of the battery was measured and recorded by a micrometer and recorded as D 11 The method comprises the steps of carrying out a first treatment on the surface of the Standing at 45deg.C for 1 hr, charging to 4.55V with constant current of 0.4C, then charging at constant voltage of 4.55V for 1000 hr, testing with micrometer, and recording thickness of battery as D 12 ；
Thickness expansion ratio= (D 12 -D 11 )/D 11 ×100％。
3. Test results
As is clear from comparative examples 1 to 5 and comparative examples 1 and 2, the compound of formula I can improve high temperature cycle and high temperature storage properties, since the non-common electron pair of N in the compound I can stabilize anions of salts in the electrolyte, and the unsaturated functional group included in the particular compound of formula I can be reduced on the surface of the anode to form a stable ion conductive film; meanwhile, the oxidation potential of the compound of the formula I is lower, a solid electrolyte phase interface film (namely CEI film) can be formed on the surface of the positive electrode preferentially, the positive electrode is protected, chemical gas production caused by contact of a positive electrode material and electrolyte is reduced, and the cycle and high-temperature storage performance are improved; it is understood from comparative examples 3 and 3 that the introduction of the unsaturated bond can further improve the cycle performance and the high-temperature storage thickness expansion rate because the introduction of the unsaturated functional group can preferentially reduce the stable SEI film at the anode, inhibit the side reaction of the electrolyte with the electrode interface, and thus improve the cycle performance and the high-temperature storage performance.
As is apparent from comparative examples 1 to 7 and comparative examples 1 and 2, by using the compound of formula I in combination with the polynitrile compound, it is possible to further improve the high temperature cycle and high temperature storage performance and to further improve the hot box performance, which is mainly due to the presence of polynitrile, which makes the thermal stability of the positive electrode interface higher, which is advantageous for improving the stability of the positive electrode structure at high temperature and high pressure, and the improvement of the stability of the positive electrode structure further reduces the oxidative decomposition of the electrolyte at the positive electrode interface, thereby reducing the generation of reaction heat. In addition, on the basis of ensuring the safety performance of the battery, the usage amount of the compound of the formula I is reduced by introducing the polynitrile to be used in combination with the compound of the formula I; the two are combined mutually, so that the thermal stability and the mechanical stability of the interface film are improved, and the cycle performance, the high-temperature storage performance and the safety performance are improved.
It can be seen from comparative examples 5 to 10 that too high a nitrile content of tri-or higher nitrile causes corrosion of copper foil, and that combining it with di-nitrile and adjusting the ratio of the two can avoid this phenomenon.
As can be seen by comparing examples 1-7 with examples 11-14, different compounds of formula I can perform similarly.
(2) Table 2 shows the effect of cyclic sulfonate additives on cell performance.
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As can be seen from comparative examples 23 to 27 and comparative examples 6 to 7, DCR and high temperature storage properties of the electrolyte containing the tetraborate compound are significantly improved because the tetraborate compound can form a dense and stable interface film at the negative electrode, and the formed interface film has higher ionic conductivity and stronger electronic insulation, significantly improves interface impedance, and reduces DCR; the organic-inorganic interfacial film is formed by the synergistic effect of the structural additive, the impedance of the interfacial film is reduced, the mechanical strength of the interfacial film is improved, and the thermal stability and the chemical stability are higher.
As is clear from comparative examples 23 to 27, the electrical properties are optimal when the tetraborate-containing compound is contained in an amount of 0.3%, the electrical properties are superior when the tetraborate-containing compound is contained in an amount of 0.1%, the electrical properties are general when the tetraborate-containing compound is contained in an amount of 0.5% or 0.7%, but the electrical properties are deteriorated when the tetraborate-containing compound is contained in an amount exceeding 1%; this is because when the content of the additive containing the tetraborate compound is too low, it is difficult to sufficiently form a dense, thin and uniform protective film on the surface of the pole piece, so that the oxidative decomposition reaction of the metal ion-catalyzed electrolyte cannot be effectively suppressed; when the content of the tetraborate-containing compound additive is too high, the protective film formed is too thick, resulting in an increase in resistance and a decrease in electrical properties.
(4) Table 4 shows the effect of the positive electrode insulating coating on the battery performance.
Table 4 electrolytes of examples 28 to 31
The insulating coating of examples 30 and 31 was positioned between two adjacent first surface positive electrode active material layers, with a gap of 1mm between the two ends of the insulating layer and the first surface active material layers, the insulating layer being made of alumina and having a thickness of 10um.
From the data in table 4, it can be seen that the presence of the insulating coating can improve the thermal stability of the battery without any deterioration of other electrical properties. The action mechanism is not clear at present, and the existence of the insulating coating is presumed to reduce the exposure of the metal aluminum substrate and the contact with the electrolyte. Because the positive electrode of the full charge battery is in a high potential state, the corresponding high potential metallic aluminum is in contact with the electrolyte, so that the chemical reaction is easy to occur, the heat generation quantity is promoted to be increased, and the heat generation quantity can be reduced to a certain extent by reducing the exposure of the base material, so that the passing rate of the heat box is improved.

Claims (15)

1. An electrolyte comprising a compound of formula I,
in the formula I, R 1 、R 2 And R is 3 Each independently selected from the group consisting of hydrogen, halogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, and substituted or unsubstituted heteroatom-containing group;
Wherein, when substituted, the substituent is selected from halogen;
the heteroatom includes at least one of O, S, N and B;
R 2 and R is 3 At least one of which has an unsaturated functional group,
wherein the electrolyte also comprises a polynitrile compound with the cyano number more than or equal to 2, and the unsaturated functional group comprises at least one of a carbon-carbon double bond and a carbon-carbon triple bond.
2. The electrolyte of claim 1, wherein in formula I, R 1 、R 2 And R is 3 Each independently selected from hydrogen, halogen, substituted or unsubstituted C 1- C 10 Alkyl, substituted or unsubstituted C 2- C 10 Alkenyl, substituted or unsubstituted C 2- C 10 Alkynyl and substituted or unsubstituted C 1- C 10 Containing hetero atom groups.
3. The electrolyte of claim 1, wherein the heteroatom-containing group is selected from the group consisting of an ester group, a ketone group, an aldehyde group, an amino group, an amine group, a borate group, an alkoxy group, a thiol group, and a cyano group.
4. The electrolyte of claim 1, wherein the compound of formula I is selected from one or more of the following:
5. the electrolyte of claim 1, wherein the mass percent of the compound of formula I is 0.01% to 2% based on the mass of the electrolyte.
6. The electrolyte of claim 1, further comprising at least one of a sulfonate compound and a boron-containing lithium salt compound.
7. The electrolyte according to claim 6, wherein the polynitrile compound having a cyano group number of 2 or more is 0.10 to 15% by mass, the sulfonate compound is 0.10 to 10% by mass, and the boron-containing lithium salt compound is 0.01 to 5% by mass, based on the mass of the electrolyte.
8. The electrolyte according to claim 1, wherein the polynitrile compound having a cyano number of not less than 2 contains at least one of compounds represented by formulas (II) to (V):
wherein R is 21 Selected from substituted or unsubstituted C 1 ～C 12 Alkylene, substituted or unsubstituted C 1 ～C 12 An alkyleneoxy group; r is R 31 And R is 32 Each independently selected from a single bond or substituted or unsubstituted C 1 ～C 12 An alkylene group; r is R 41 、R 42 And R is 43 Each independently selected from single bond, substituted or unsubstituted C 1 ～C 12 Alkylene, substituted or unsubstituted C 1 ～C 12 An alkyleneoxy group; r is R 51 Selected from substituted or unsubstitutedSubstituted C 1 ～C 12 Alkylene, substituted or unsubstituted C 2 ～C 12 Alkenylene, substituted or unsubstituted C 6～ C 26 Arylene, substituted or unsubstituted C 2- C 12 A heterocyclylene group; wherein when substituted, the substituent is a halogen atom.
9. The electrolyte according to claim 8, wherein the polynitrile compound having a cyano number of 2 or more comprises at least one of:
10. The electrolyte of claim 6, wherein the sulfonate compound comprises at least one of the compounds of formula VI:
in formula VI, A and B each independently represent C 1 -C 8 Alkylene or fluoro C 1 -C 8 Alkylene group, and L represents a single bond or-OSO 2 -a radical.
11. The electrolyte of claim 10, wherein the sulfonate compound comprises at least one of 1, 3-propane sultone, 1, 2-propane sultone, 1, 4-butane sultone, 1, 2-butane sultone, 1, 3-butane sultone, 2, 4-butane sultone, 1, 3-pentane sultone, methane disulfonic acid methylene ester, and methane disulfonic acid ethylene ester.
12. The electrolyte of claim 6, wherein the boron-containing lithium salt compound comprises at least one of the compounds of formula VII:
wherein M is + Represents an alkali metal cation.
13. An electrochemical device comprising a positive electrode, a negative electrode, and the electrolyte of any one of claims 1-12.
14. The electrochemical device according to claim 13, wherein the positive electrode includes a current collector, and an active material layer and an insulating layer provided on a surface of the current collector.
15. An electronic device comprising the electrochemical device of claim 13 or 14.
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