CN116114097A - Electrolyte and electrochemical device comprising the same - Google Patents

Electrolyte and electrochemical device comprising the same Download PDF

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Publication number
CN116114097A
CN116114097A CN202080105132.4A CN202080105132A CN116114097A CN 116114097 A CN116114097 A CN 116114097A CN 202080105132 A CN202080105132 A CN 202080105132A CN 116114097 A CN116114097 A CN 116114097A
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electrolyte
compound
substituted
formula
lithium
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彭谢学
郑建明
唐超
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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
    • H01M10/056—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
    • 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

An electrolyte, and an electrochemical device and an electronic device including the same. The electrolyte comprises at least one compound of formula I. The electrolyte can improve the high-temperature storage performance of an electrochemical device.

Description

Electrolyte and electrochemical device comprising the same Technical Field
The present disclosure relates to the field of energy storage technologies, and in particular, to an electrolyte and an electrochemical device including the same.
Background
Electrochemical devices, such as lithium ion batteries, have been widely focused on such characteristics as high energy density, low maintenance, relatively low self-discharge, long cycle life, no memory effect, stable operating voltage, and environmental friendliness, and are widely used in the fields of portable electronic devices (including electronic products such as cellular phones, notebooks, cameras), electric tools, and electric automobiles. However, with the rapid development of technology and the diversity of market demands, more demands are also put on power supplies of electronic products, such as thinner, lighter, more diversified shapes, higher safety, higher power, etc.
Increasing the charge voltage/increasing the capacity of the active material is the primary method of increasing the energy density of the battery, and these all accelerate the decomposition of the electrolyte, resulting in gassing of the battery. How to stabilize the transition metal in high valence state and inhibit the decomposition of electrolyte is a technical problem to be solved in the prior art.
Disclosure of Invention
The present application solves at least one problem existing in the related art by providing an electrolyte and an electrochemical device using the same. In particular, the electrolyte provided by the present application can significantly improve the high temperature performance and the float performance of an electrochemical device.
The electrolyte according to the present application comprises a compound of formula I:
Figure PCTCN2020115604-APPB-000001
wherein:
ring A is C 3 -C 10 Cyclic hydrocarbons, R 11 Each independently selected from: substituted or unsubstituted C 1 -C 10 Alkylene, substituted or unsubstituted C 2 -C 10 Alkenylene or substituted or unsubstituted C 2 -C 10 Alkynylene; wherein, when substituted, the substituent is halogen;
R 12 each independently selected from the following: 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; wherein, when substituted, the substituent is halogen;
n is an integer from 1 to 7 and m is an integer from 1 to 19.
In some embodiments, the compound of formula I comprises at least one of the following compounds:
Figure PCTCN2020115604-APPB-000002
Figure PCTCN2020115604-APPB-000003
in some embodiments, the compound of formula I is present in an amount of 0.01% to 5% based on the total weight of the electrolyte.
In some embodiments, the electrolyte further comprises at least one of: a compound containing a sulfur-oxygen double bond, a polynitrile compound, a lithium salt containing a P-O bond or fluoroethylene carbonate.
In some embodiments, the sulfur-oxygen double bond containing compound includes at least one of the following: sulfolane, 1, 3-propane sultone, 1, 4-butane sultone, methyl disulfonate, 1, 3-propane disulfonate, vinyl sulfate, 4-methyl vinyl sulfate, 2, 4-butane sultone, 1, 3-butane sultone, 1-fluoro-1, 3-propane sultone, 2-fluoro-1, 3-propane sultone, 3-fluoro-1, 3-propane sultone, propenyl-1, 3-sulfonic acid lactone, propylene sulfate or vinyl fluorosulfate.
In some embodiments, the polynitrile compound comprises at least one of the following: 1,2, 3-tris (2-cyanoethoxy) propane, 1,3, 6-hexanetrinitrile, 1, 2-bis (2-cyanoethoxy) ethane, succinonitrile or adiponitrile.
In some embodiments, the lithium salt containing a P-O bond comprises at least one of lithium difluorophosphate, lithium difluorobis oxalato phosphate, or lithium tetrafluorooxalato phosphate.
In some embodiments, when the electrolyte includes a compound having a sulfur-oxygen double bond, the content of the compound having a sulfur-oxygen double bond is 0.01% to 10% based on the total weight of the electrolyte; when the electrolyte comprises a polynitrile compound, the mass ratio of the compound of formula I to the polynitrile compound is less than or equal to 1; when the electrolyte comprises a lithium salt containing P-O bonds, the mass ratio of the compound of formula I to the lithium salt containing P-O bonds is less than 5; when the electrolyte includes fluoroethylene carbonate, the content of fluoroethylene carbonate is 1% to 10% based on the total weight of the electrolyte.
The present application also provides an electrochemical device comprising an electrolyte according to the present application.
In some embodiments, the electrochemical device further comprises a separator comprising a porous polymer layer having a fluoropolymer disposed thereon.
In some embodiments, the separator of the electrochemical device further comprises inorganic particles comprising boehmite, mg (OH) 2 、SrTiO 3 、SnO 2 、CeO 2 、MgO、NiO、CaO、ZnO、ZrO 2 、Y 2 O 3 、Al 2 O 3 、TiO 2 Or SiC.
In some embodiments, the separator has a porosity of 20% to 65% in the electrochemical device.
The present application also provides an electronic device comprising an electrochemical device according to the present application.
Detailed Description
For the purposes of making the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be clearly and completely described below in conjunction with the embodiments, and it is apparent that the described embodiments are some, but not all, embodiments of the present application. The related embodiments described herein are of illustrative nature and are intended to provide a basic understanding of the present application. The examples of the present application should not be construed as limiting the present application. Based on the technical solution provided in the present application and the embodiments given, all other embodiments obtained by a person skilled in the art without making any inventive effort are within the scope of protection of the present application.
As used herein, the term "about" is used to describe and illustrate small 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%. For example, two values may be considered "about" the same if the difference between the two values is less than or equal to ±10% (e.g., 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%) of the average value of the values.
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.
In the detailed description and claims, a list of items connected by the terms "one of," "one of," or other similar terms may mean any of the listed items. For example, if items a and B are listed, the phrase "one of a and B" means either only a or only B. In another example, if items A, B and C are listed, one of the phrases "A, B and C" means only a; only B; or only C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements.
In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items a and B are listed, the phrase "at least one of a and B" means only a; only B; or A and B. In another example, if items A, B and C are listed, then the phrase "at least one of A, B and C" means only a; or only B; only C; a and B (excluding C); a and C (excluding B); b and C (excluding A); or A, B and C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements.
The following definitions are used in this application (unless explicitly stated otherwise):
for simplicity, a "Cn-Cm" group refers to a group having from "n" to "m" carbon atoms, where "n" and "m" are integers. For example, "C 1- C 10 Alkyl "is an alkyl group having 1 to 10 carbon atoms.
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. For example, the alkyl group may be an alkyl group of 1 to 20 carbon atoms, an alkyl group of 1 to 10 carbon atoms, an alkyl group of 1 to 5 carbon atoms, an alkyl group of 5 to 20 carbon atoms, an alkyl group of 5 to 15 carbon atoms, or an alkyl group of 5 to 10 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. In addition, the alkyl group may be optionally substituted.
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 group typically contains 2 to 20 carbon atoms, for example, can be an alkenyl group of 2 to 20 carbon atoms, an alkenyl group of 6 to 20 carbon atoms, an alkenyl group of 2 to 10 carbon atoms, or an alkenyl group of 2 to 6 carbon atoms. Representative alkenyl groups include, for example, vinyl, n-propenyl, isopropenyl, n-but-2-enyl, but-3-enyl, n-hex-3-enyl, and the like. In addition, alkenyl groups may be optionally substituted.
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, for example, an alkynyl group which may be 2 to 20 carbon atoms, an alkynyl group of 6 to 20 carbon atoms, an alkynyl group of 2 to 10 carbon atoms, or an alkynyl group of 2 to 6 carbon atoms. Representative alkynyl groups include, for example, ethynyl, prop-2-ynyl (n-propynyl), n-but-2-ynyl, n-hex-3-ynyl, and the like. In addition, alkynyl groups may be optionally substituted.
The term "alkylene" means a divalent saturated hydrocarbon group that may be straight or branched. Unless otherwise defined, the alkylene group typically contains 1 to 10, 1 to 6, 1 to 4, or 2 to 4 carbon atoms and includes, for example, -C 2-3 Alkylene and-C 2-6 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.
The term "alkenylene" means a difunctional group obtained by removing one hydrogen atom from the alkenyl group defined above. Preferred alkenylenes include, but are not limited to, -ch=ch-, -C (CH 3 )＝CH-、-CH＝CHCH 2 –、
Figure PCTCN2020115604-APPB-000004
Etc.
The term "aryl" means a monovalent aromatic hydrocarbon having a single ring (e.g., phenyl) or a fused ring. Fused ring systems include those that are fully unsaturated (e.g., naphthalene) and those that are partially unsaturated (e.g., 1,2,3, 4-tetrahydronaphthalene). Unless otherwise defined, the aryl groups typically contain 6 to 26, 6 to 20, 6 to 15, or 6 to 10 carbon ring atoms and include, for example, -C 6-10 Aryl groups. Representative aryl groups include, for example, phenyl, methylphenyl, propylphenyl, isopropylphenyl, benzyl, and naphthalen-1-yl, naphthalen-2-yl, and the like.
The term "heterocycle" or "heterocyclyl" means a substituted or unsubstituted 5-to 8-membered mono-or bicyclic non-aromatic hydrocarbon in which 1 to 3 carbon atoms are replaced by heteroatoms selected from nitrogen, oxygen or sulfur atoms. Examples include pyrrolidin-2-yl; pyrrolidin-3-yl; a piperidinyl group; morpholin-4-yl, etc., which groups may then be substituted. "heteroatom" means an atom selected from N, O and S.
"cycloaliphatic" refers to a cyclic hydrocarbon having aliphatic character, and cycloaliphatic is a group having a closed carbocyclic ring in the molecule.
As used herein, the term "halogen" may be F, cl, br or I.
As used herein, the term "cyano" encompasses organics containing an organic group-CN.
When the above substituents are substituted, the substituents may be selected from the group consisting of: halogen, alkyl, alkenyl, aryl, and heteroaryl.
1. Electrolyte solution
1. Compounds of formula I
The electrolyte of the present application comprises at least one compound of formula I:
Figure PCTCN2020115604-APPB-000005
wherein:
ring A is C 3 -C 10 Cyclic hydrocarbons, R 11 Each independently selected from: substituted or unsubstituted C 1 -C 10 Alkylene, substituted or unsubstituted C 2 -C 10 Alkenylene or substituted or unsubstituted C 2 -C 10 Alkynylene; wherein, when substituted, the substituent isHalogen;
R 12 each independently selected from the following: 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; wherein, when substituted, the substituent is halogen;
n is an integer from 1 to 7 and m is an integer from 1 to 19.
In some embodiments, R in a compound of formula I 11 Each independently selected from substituted or unsubstituted C 1 -C 10 Alkylene, when substituted, the substituent is fluorine or chlorine. N in formula I may be 1,2,3,4,5,6 or 7, for example, n may be an integer from 2 to 6.
In some embodiments, R in a compound of formula I 12 Each independently selected from hydrogen, halogen, substituted or unsubstituted C 1 -C 10 At least one of the alkyl groups, e.g. R 12 May be substituted or unsubstituted C 1 -C 10 An alkyl group; wherein, when substituted, the substituent is fluorine or chlorine. M in formula I may be 1,2,3,4,5,6, 7, 8, 9, 10, 12, 15, 17, or 19, for example, m may be an integer from 3 to 10.
In some embodiments, the compound of formula I in the electrolyte comprises at least one of the following compounds:
Figure PCTCN2020115604-APPB-000006
Figure PCTCN2020115604-APPB-000007
in some embodiments, the compound of formula I comprises at least one of the following compounds: 3,3' - (cyclohex-4-ene-1, 2-diyl) dipropionitrile (I-3), 3"- (cyclohexane-1, 2, 3-diyl) tripropionitrile (I-6), 3',3", 3' - (cyclohexane-1, 2,3, 4-tetrayl) tetrapropionitrile (I-8), 3', 3%, 3' - (cyclohex-1-en-1, 2,4, 5-tetrayl) tetrapropionitrile (I-10), 3', 3' - (cyclobutane-1, 2,3, 4-tetrayl) tetrapropionitrile (I-15), 3', 3' - (cyclopent 2, 4-diene-1, 2,3, 4-pentyl) valeronitrile (I-17), 3', 3' - (cyclopent 2, 4-diene-1, 2,3, 4-pentyl) valeronitrile (I-17), 3',3",3 '".
In some embodiments, the compound of formula I is present in an amount of 0.01% to 5% based on the total weight of the electrolyte; for example, the compound of formula I may be present in an amount of about 0.01%, about 0.05%, about 0.1%, about 0.2%, about 0.3%, about 0.4%, about 0.5%, about 0.6%, about 0.7%, about 0.8%, about 0.9%, about 1.0%, about 2.0%, about 3.0%, about 4.0%, about 5.0%, or in a range between any two of the foregoing values.
The compound of formula I with the cyclic hydrocarbon structure can enhance the stability of the transition metal with a positive electrode and a high valence state. Therefore, the electrolyte of the present application can significantly improve the high-temperature storage performance of the electrochemical device.
2. Other additives
In some embodiments, the electrolyte further comprises at least one of: a compound containing a sulfur-oxygen double bond, a polynitrile compound, a lithium salt containing a P-O bond or fluoroethylene carbonate.
(1) Compounds containing sulfur-oxygen double bonds
The electrolyte of the present application may further comprise a sulfur-oxygen double bond containing compound comprising at least one compound of formula II-a:
Figure PCTCN2020115604-APPB-000008
wherein,
R 21 and R is 22 Each independently selected from substituted or unsubstituted C 1 -C 5 Alkyl, substituted or unsubstituted C 2 -C 10 Alkenyl, substituted or unsubstituted C 2 -C 10 Alkynyl, substituted or unsubstituted C 3 -C 10 Alicyclic, substituted or unsubstituted C 6 -C 10 Aryl, substituted or unsubstituted C 1 -C 6 Heterocyclic groups (heterocyclic groups include alicyclic and aromatic heterocyclic groups), wherein, when substituted, the substituent is one or more of a halogen atom or a heteroatom-containing functional group, wherein R 21 And R is 22 The ring closure structure may be formed, and the atoms in the heteroatom-containing functional group may be selected from one or more of H, B, C, N, O, F, si, P and S (excluding functional groups containing only two atoms, C and H).
In some embodiments, the sulfur-oxygen double bond containing compound includes, but is not limited to, at least one of the following:
Figure PCTCN2020115604-APPB-000009
Figure PCTCN2020115604-APPB-000010
in some embodiments, the sulfur-oxygen double bond containing compound includes at least one of the following: sulfolane (II-7), 1, 3-propane sultone (II-12), 1, 4-butane sultone, methylene methylsulfonate (II-21), 1, 3-propane disulfonic anhydride, vinyl sulfate (II-18), 4-methyl vinyl sulfate, 2, 4-butane sultone, 2-methyl-1, 3-propane sultone, 1, 3-butane sultone, 1-fluoro-1, 3-propane sultone, 2-fluoro-1, 3-propane sultone, 3-fluoro-1, 3-propane sultone, propenyl-1, 3-propane sultone (II-17), propylene sulfate or vinyl fluorosulfate.
In some embodiments, the sulfur-oxygen double bond containing compound includes at least one of the following: sulfolane (II-7), 1, 3-propane sultone (II-12), propenyl-1, 3-sultone (II-17), vinyl sulfate (II-18) or methylene methylsulfonate (II-21).
In some embodiments, when the electrolyte includes a compound containing a sulfur-oxygen double bond, the content of the compound containing a sulfur-oxygen double bond is 0.01% to 10%, more preferably 0.1% to 8%, based on the total weight of the electrolyte; for example, the content of the sulfur-oxygen double bond containing compound may be about 0.01%, about 0.05%, about 0.1%, about 0.2%, about 0.3%, about 0.4%, about 0.5%, about 0.6%, about 0.7%, about 0.8%, about 0.9%, about 1.0%, about 2.0%, about 3.0%, about 4.0%, about 5.0%, about 6.0%, about 8.0%, or about 10.0%, or a range between any two of the above.
According to the application, the compound in the formula I and the compound containing the sulfur-oxygen double bond act together, so that the oxidation resistance of the electrolyte is enhanced, the anode material is not easy to oxidize, on the other hand, in the case of lithium precipitation of the anode, the compound can be reduced on the surface of the metal lithium to form a protective film, thereby inhibiting heat generation caused by decomposition reaction of the metal lithium and the electrolyte, and further enhancing protection of the active material.
(2) Polynitrile compound
In some embodiments, the electrolyte may further include a polynitrile compound including at least one of a dinitrile or a tri-nitrile compound. In some embodiments, the polynitrile compound comprises at least one of the following: 1,2, 3-tris (2-cyanoethoxy) propane (TCEP), 1,3, 6-Hexanetrinitrile (HTCN), 1, 2-bis (2-cyanoethoxy) ethane (DENE) or Adiponitrile (ADN), the structures of which are shown below:
Figure PCTCN2020115604-APPB-000011
Figure PCTCN2020115604-APPB-000012
in some embodiments, when the electrolyte comprises a polynitrile compound, the mass ratio of the compound of formula I to the polynitrile compound is less than or equal to 1; for example, the mass ratio of the compound of formula I to the polynitrile compound may be about 1, about 0.9, about 0.8, about 0.7, about 0.6, about 0.5, about 0.4, about 0.3, about 0.2, about 0.1, or a range between any two of the above values.
The use of the polynitrile compound in combination with the compound of formula I having a cyclic hydrocarbon structure according to the present application can effectively reduce the viscosity and cost of the electrolyte. By providing a combination of a polynitrile compound and a compound of formula I, it is possible to ensure that the excellent properties of the compound of formula I can be reflected while simultaneously improving other properties.
(3) Lithium salt containing P-O bond
The lithium salt containing the P-O bond can form a stable interface film on the surfaces of the positive electrode and the negative electrode, stabilize the interface between the electrode and the electrolyte, inhibit the decomposition of the electrolyte, reduce gas production and improve the performance of the battery.
In some embodiments, the electrolyte may further comprise a lithium salt containing a P-O bond. In some embodiments, the phosphate lithium salt compound comprises lithium difluorophosphate (LiPO) 2 F 2 ) At least one of lithium difluorobis (oxalato) phosphate (LiDFOP) or lithium tetrafluoro (oxalato) phosphate (LiTFOP).
In some embodiments, when the electrolyte includes a lithium salt containing P-O bonds, the content of the lithium salt containing P-O bonds is no more than about 3%, for example, may be no more than about 2%, no more than about 1.5%, no more than about 1.2%, no more than about 1%, no more than about 0.9%, no more than about 0.8%, no more than about 0.5%, or no more than about 0.1%, or a range between any two of the foregoing values, based on the total weight of the electrolyte.
In some embodiments, when the electrolyte includes a lithium salt containing P-O bonds, the mass ratio of the compound of formula I to the lithium salt containing P-O bonds is less than 10, e.g., the mass ratio may be less than about 10, less than about 8, less than about 6, less than about 5, less than about 4, less than about 3, less than about 2, less than about 1, or a range between any two of the foregoing.
(4) Cyclic carbonate additives
In some embodiments, the electrolyte may further comprise a cyclic carbonate compound comprising at least one compound of formula III-a:
Figure PCTCN2020115604-APPB-000013
Wherein R is 3 Selected from substituted C 2 -C 6 Alkylene, unsubstituted C 3 -C 6 Alkylene or substituted or unsubstituted C 2 -C 6 Alkenylene; when substituted, the substituents are selected from halogen, C 1 -C 6 Alkyl or C 2 -C 6 Alkenyl groups.
In some embodiments, the cyclic carbonate compound includes at least one of the following compounds, but is not limited thereto:
Figure PCTCN2020115604-APPB-000014
Figure PCTCN2020115604-APPB-000015
in some embodiments, the cyclic carbonate additive includes at least one of fluoroethylene carbonate (FEC) or Vinylene Carbonate (VC).
In some embodiments, when the electrolyte includes a cyclic carbonate additive, such as fluoroethylene carbonate, the content of the cyclic carbonate compound is from 1% to 10%, for example, the content of the cyclic carbonate additive (e.g., fluoroethylene carbonate) may be about 0.01%, about 0.05%, about 0.1%, about 0.2%, about 0.3%, about 0.4%, about 0.5%, about 0.6%, about 0.7%, about 0.8%, about 0.9%, about 1.0%, about 2.0%, about 3.0%, about 4.0%, about 5.0%, about 6.0%, about 8.0%, about 9.0%, or about 10.0%, or a range between any two of the foregoing, based on the total weight of the electrolyte.
In this application, the compound of formula I in combination with the cyclic carbonate additive may further help to enhance the stability of the SEI film. In some embodiments, the cyclic carbonate additive may include at least one compound of formula III-a. The cyclic carbonate compound can increase the flexibility of the SEI film, enhance the protection effect on the active material, and reduce the interface contact probability of the active material and the electrolyte, thereby improving the impedance increase generated by the accumulation of byproducts in the circulation process.
3. Organic solvents
The electrolyte of the present application may further comprise a nonaqueous organic solvent.
In some embodiments of the present invention, in some embodiments, the non-aqueous organic solvent may comprise dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, ethyl acetate, n-propyl acetate, n-butyl acetate, ethyl propionate, gamma-butyrolactone, 2-difluoroethyl acetate, valerolactone, ethylene carbonate, propylene carbonate, butylene carbonate, ethyl acetate, n-propyl acetate, n-butyl acetate, ethyl propionate, valerolactone, ethylene carbonate, propylene carbonate, butylene carbonate, ethylene carbonate, propylene carbonate, and the like butyrolactone, 2-difluoroethyl propionate, methyl 3, 3-difluoropropionate, ethyl 4, 4-difluorobutyrate, 3-difluoropropyl acetate at least one of 3, 3-difluoropropyl propionate, 2-trifluoroethyl acetate, 2-difluoroethyl formate, 2-trifluoroethyl formate, and 2, 3-tetrafluoropropyl propionate.
In some embodiments, one non-aqueous organic solvent may be used in the electrolyte, or a mixture of a plurality of non-aqueous organic solvents may be used, and when a mixed solvent is used, the mixing ratio may be controlled according to desired electrochemical device performance.
4. Lithium salt
The electrolyte of the present application may further comprise a lithium salt including or selected from at least one of an organolithium salt or an inorganic lithium salt. In some embodiments, the lithium salt contains at least one of a fluorine element, a boron element, or a phosphorus element.
In some embodiments, the lithium salts herein include or are selected from lithium hexafluorophosphate (LiPF) 6 ) Boron tetrafluorideLithium acid (LiBF) 4 ) Lithium bissulfonylimide (LiN (C) x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ) Wherein x and y are natural numbers), lithium chloride (LiCl) or lithium fluoride (LiF).
In some embodiments, the concentration of lithium salt in the electrolyte of the present application is: 0.5mol/L to 3mol/L, 0.5mol/L to 2mol/L or 0.8mol/L to 1.5mol/L.
In some embodiments, the electrolyte may comprise a combination of the following additives: compounds of formula I and compounds containing a sulfur-oxygen double bond; a compound of formula I and a lithium salt containing a P-O bond; a compound of formula I and a polynitrile compound; compounds of formula I, compounds containing a thiooxy double bond and lithium salts containing a P-O bond; compounds of formula I, compounds containing a sulfur-oxygen double bond and polynitrile compounds; compounds of formula I, polynitrile compounds and lithium salts containing P-O bonds.
In some embodiments, the electrolyte comprises a compound of formula I and at least one of the following compounds: 1, 3-propane sultone, propenyl-1, 3-sultone, vinyl sulfate, methylene methyldisulfonate, fluoroethylene carbonate or vinylene carbonate.
2. Electrochemical device
The present application also provides an electrochemical device comprising an electrolyte according to the present application.
In some embodiments, the electrochemical device further comprises a separator comprising a porous polymer layer having a fluoropolymer disposed thereon.
In some embodiments, the separator of the electrochemical device further comprises inorganic particles comprising boehmite, mg (OH) 2 、SrTiO 3 、SnO 2 、CeO 2 、MgO、NiO、CaO、ZnO、ZrO 2 、Y 2 O 3 、Al 2 O 3 、TiO 2 Or SiC.
In some embodiments, the porosity of the separator in the electrochemical device is 20% to 65%, e.g., the porosity is about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, or 65%, or a range between any two of the above.
In some embodiments, the fluoropolymer comprises at least one of polyvinylidene fluoride or vinylidene fluoride-hexafluoropropylene copolymer.
In some embodiments, the porous polymer layer of the separator of the electrochemical device comprises a polyolefin-based microporous membrane of a single layer or multiple layers composed of one or more of Polyethylene (PE), ethylene-propylene copolymer, polypropylene (PP), ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-methyl methacrylate copolymer.
In some embodiments, an electrochemical device according to the present application further comprises a positive electrode and a negative electrode.
In some embodiments, a positive electrode of an electrochemical device includes a current collector and a positive electrode active material layer disposed on the current collector. The positive electrode active material layer includes a positive electrode active material including a compound that reversibly intercalates and deintercalates lithium ions (i.e., lithiated intercalation compound). In some embodiments, the positive electrode active material may include a composite oxide including lithium and at least one selected from cobalt, manganese, and nickel.
In some embodiments, the positive electrode material comprises Li (Ni a Co b Mn c M 1-a-b-c )O 2 (a is more than or equal to 0 and less than or equal to 1, b is more than or equal to 0 and less than or equal to 1, c is more than or equal to 0 and less than or equal to 1, a+b+c is more than or equal to 0 and less than or equal to 1, M is Mg, al, ti, cr or a combination thereof). In the electrochemical device of the present application, when the electrochemical device is 100% soc, the positive electrode active material layer is subjected to TG-MS test, and the weight loss of the positive electrode active material layer is not more than 30% when heated to 400 ℃.
In some embodiments, the positive electrode active material layer has a compacted density of 3.4g/cm 3 -4.4g/cm 3 . In some embodiments, the positive electrode active material layer of the present application has a compacted density of: 3.4g/cm 3 、3.5g/cm 3 、3.6g/cm 3 、3.61g/cm 3 、3.75g/cm 3 、3.85g/cm 3 、4.0g/cm 3 、4.1g/cm 3 、4.15g/cm 3 、4.27g/cm 3 、4.35g/cm 3 、4.4g/cm 3 Or a range between any two of the above values.
In some embodiments, the positive electrode active material layer may include a positive electrode material, a binder, and a conductive material. The binder improves the adhesion properties of the positive electrode active material particles to each other and to the current collector. In some embodiments, non-limiting examples of binders include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy or nylon, and the like.
The conductive material is used to provide conductivity to the electrode. The conductive material may comprise any conductive material so long as it does not cause unwanted chemical changes. In some embodiments, examples of conductive materials include mixtures of one or more of the conductive materials such as: natural graphite; artificial graphite; carbon black; acetylene black; black ketjen; a carbon fiber; metal powders, metal fibers, etc., such as copper, nickel, aluminum, silver, etc.; or a polyphenylene derivative, etc. In some embodiments, the current collector of the positive electrode may include aluminum, but is not limited thereto.
In some embodiments, a negative electrode of an electrochemical device includes a current collector and a negative electrode active material layer formed on the current collector. The anode active material layer includes an anode active material, and the anode active material 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. 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.
In some embodiments, the anode active material layer may include 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, or the like, but is not limited thereto.
In some embodiments, 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 an unwanted chemical change. In some embodiments, 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. In some embodiments, the current collector of the negative electrode may comprise 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.
In some embodiments, the lithium metal alloy comprises lithium and at least one metal selected from Na, K, rb, cs, fr, be, mg, ca, sr, si, sb, pb, in, zn, ba, ra, ge, al or Sn. Can be doped withExamples of hetero/dedoping lithium materials include Si, siO x (0<x<2) Si/C composite, si-Q alloy (wherein Q is an alkali metal, alkaline earth metal, group 13 to group 16 element, transition element, rare earth element or combination thereof, but not Si), sn, snO z Sn-C complexes, sn-R (where R is an alkali metal, alkaline earth metal, group 13 to group 16 element, transition element, rare earth element, or a combination thereof, but is not Sn), and the like. In some embodiments, exemplary elements of Q and R include Mg, ca, sr, ba, ra, sc, Y, ti, zr, hf, rf, V, nb, ta, db, cr, mo, W, sg, tc, re, bh, fe, pb, ru, os, hs, rh, ir, pd, pt, cu, ag, au, zn, cd, B, al, ga, sn, in, tl, ge, P, as, sb, bi, S, se, te, po or a combination thereof. In some embodiments, the transition metal oxide may be vanadium oxide, lithium vanadium oxide, or the like.
In some embodiments, the negative electrode active material layer has a compacted density of 1.6g/cm 3 -1.9g/cm 3 . In some embodiments, the negative electrode active material layer of the present application has a compacted density of: 1.6g/cm 3 、1.7g/cm 3 、1.75g/cm 3 、1.8g/cm 3 、1.85g/cm 3 、1.9g/cm 3 Or a range between any two of the above values.
In some embodiments, the above SiO x (0<x<2) Is a porous silicon negative electrode active material, porous SiO x Average particle diameter of particles (D 50 ) 1 μm to 20 μm, siO when measured on a surface x The average diameter of the pores of the particles is 30nm to 500nm, siO x The specific surface area of the particles was 5m 2 /g to 50m 2 /g, the porous SiO x The particulate silicon-based negative electrode active material may contain Li 2 SiO 3 Li (lithium ion battery) 4 SiO 4 At least one of them.
In some embodiments, the carbon in the above Si/C composite may not be agglomerated and dispersed in a bulk form inside the Si particles, but be uniformly dispersed in an atomic state inside the Si particles, and the molar ratio of C to Si (C/Si ratio) may be in the range of 0 to 18 (excluding 0 and 18), the content of the carbon may be 1% to 50% with respect to the entire weight (wt) of the above Si/C composite, and the particle size of the Si/C composite may be 10nm to 100 μm.
The application achieves the following unexpected technical effects: the compound of the formula I provided by the application can stabilize the transition metal in the positive high valence state, and can enhance the stability of the transition metal in the positive high valence state due to the cyclic hydrocarbon group structure and the increased cyano group number. Thus, the electrolyte of the present application significantly improves the high temperature storage performance of an electrochemical device (e.g., a lithium ion battery).
Examples
The present application is further illustrated below in conjunction with the examples. It should be understood that these examples are illustrative only of the present application and are not intended to limit the scope of the present application.
Example I
1. Synthesis of Compound I-6
21.6g of 1,2, 3-cyclohexanetricarboxylic acid, 38.4g of methanol, 2mL of concentrated sulfuric acid and 120mL of 1, 2-dichloroethane are introduced into a 500mL round-bottomed flask, stirred and refluxed for 30h. Then, a mixture of water and chloroform was added to dissolve all solids, and washed successively with water, 5% sodium bicarbonate and water, and the organic layers were combined, filtered and concentrated with anhydrous magnesium sulfate and activated carbon to give 19.3g of methyl 1,2, 3-cyclohexanecarboxylate.
To a 1000mL round bottom flask equipped with a Soxhlet extractor, 800mL of diethyl ether (dry) and 13.3g of LiAlH4 were charged, the Soxhlet extractor (comprising a glass wool plug) was charged with 19.3g of methyl 1,2, 3-cyclohexanecarboxylate, and then the solvent was heated to reflux, slowly extracting the ester compound in the cannula, and reacting to reflux for 30h. Cooling to room temperature, adding saturated potassium sodium tartrate, dissolving, stirring for 1h, extracting with dichloromethane, drying, and concentrating to obtain 10.7g of 1,2, 3-cyclohexanedimethanol.
Into a 200mL round bottom flask was added 10.7g of 1,2, 3-cyclohexanediol and 100g of pyridine, and placed in an ice bath, 39.1g of p-toluenesulfonyl chloride was added in portions over 40min, stirred at 0℃for 3h, the mixture was brought to room temperature, and the mixture was poured into 400mL of cooled 6M hydrochloric acid, the mixture was suction filtered, washed with dilute hydrochloric acid and water, dried under vacuum at room temperature and recrystallized from chloroform to give 33.4g of 1,2, 3-cyclohexanedicarboxylate ((methylene) p-toluenesulfonate).
A500 mL autoclave was charged with 33.4g of 1,2, 3-cyclohexanetrica ((methylene) p-toluenesulfonate), 18g of lithium bromide and 200mL of acetone, and heated at 110℃for 14.5 hours. The mixture was cooled and filtered, and the filter cake was washed with 4 portions of 100mL of carbon tetrachloride, the organic layers were combined, concentrated, and recrystallized from carbon tetrachloride to give 8.5g of 1,2, 3-tris (bromomethyl) cyclohexane.
Divalent 2-cyanomalonate (11.8 g) and 1,2, 3-tris (bromomethyl) cyclohexane (8.5 g) were dissolved in 20mL of acetone and added to a solution of 16.3g of potassium carbonate in acetone (100 mL), stirred at room temperature for 72 hours, acetone was removed in vacuo, saturated ammonium chloride was added, filtered, the filter cake was washed with water, the filtrate was extracted with dichloromethane, the solvent was removed, the solids were combined, and dried in vacuo. The crude product was purified by column chromatography on silica gel to give 9g of hexamethyl 2,2' - (cyclohexane-1, 2, 3-triyltri (methylene)) tris (2-cyanomalonate).
9g of hexamethyl 2,2' - (cyclohexane-1, 2, 3-triyltri (methylene)) tris (2-cyanomalonate), water (5 mL), 0.7g of sodium chloride and 15mL of dimethyl sulfoxide were heated to 140℃and reacted for 24 hours. Water and dimethyl sulfoxide were removed under high vacuum, water was added, extracted with dichloromethane, dried, and the solvent was removed to give 2.9g of 3,3',3"- (cyclohexane-1, 2, 3-triyl) tripropionitrile (I-6). Testing High Resolution Mass Spectrometry (HRMS), C 15 H 21 N 3 +K + Theoretical 282.1367 and test 282.1359.
2. Synthesis of Compound I-19
66g of cyclopentadiene, 100g of 1, 4-dioxane and 4g of benzyltrimethylammonium hydroxide (40% aqueous solution) were charged in a 300mL round bottom flask, 106g of acrylonitrile was slowly added dropwise to the mixture over 2h, and the temperature was maintained at 20-25℃and then reacted at 20℃for 3h. Acidifying with dilute hydrochloric acid, filtering, and recrystallizing with ethylene glycol monomethyl ether to 30g of 3,3',3"',3" ",3" "' - (cyclopent 2, 4-diene-1,1,2,3,4,5-hexyl) hexapropionitrile (I-19). Testing High Resolution Mass Spectrometry (HRMS), C 23 H 24 N 6 +K + Theoretical 423.1694 and test 423.1688.
Example II
1. Preparation method
1) Preparation of electrolyte
Basic electrolyte one: at the water content<In a 10ppm argon atmosphere glove box, ethylene Carbonate (EC), propylene Carbonate (PC), diethyl carbonate (DEC), ethyl Propionate (EP) and Propyl Propionate (PP) were uniformly mixed in a mass ratio of 1:1:1:1:1, and then a sufficiently dried lithium salt LiPF was prepared 6 (1 mol/L) was dissolved in the above mixture to obtain a first base electrolyte.
And (2) a base electrolyte II: 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 (1 mol/L) was dissolved in the above mixture to obtain a second base electrolyte.
And (3) a base electrolyte III: at the water content<In a 10ppm argon atmosphere glove box, ethylene carbonate (abbreviated as EC), propylene carbonate (abbreviated as PC), diethyl carbonate (abbreviated as DEC) and ethyl propionate (abbreviated as EP) are uniformly mixed according to a mass ratio of 1:2:6:1, and then fully dried lithium salt LiPF is prepared 6 (1 mol/L) was dissolved in the above mixture to obtain a base electrolyte III.
To each of the above-described base electrolytes, a compound containing formula I, other additives, or a combination thereof is added, respectively, to obtain the electrolytes of each of the embodiments. The types and amounts of specific additives are provided in the tables below.
2) Preparation of positive electrode:
positive electrode one: the positive electrode active material NCM811 (molecular formula LiNi 0.8 Mn 0.1 Co 0.1 O 2 ) Acetylene black as conductive agent and binderPolyvinylidene fluoride (PVDF) is fully stirred and mixed in a proper amount of N-methyl pyrrolidone (NMP) according to the mass ratio of 96:2:2, so that uniform positive electrode slurry is formed; coating the slurry on an aluminum foil of a positive electrode current collector, drying, and cold pressing to obtain a positive electrode I with a compacted density of 3.50g/cm 3 。
And a second positive electrode: the positive electrode active material LCO (LiCoO) 2 ) Mixing conductive carbon black, conductive slurry and polyvinylidene fluoride (PVDF) as binder in a mass ratio of 97.9:0.4:0.5:1.2 in a proper amount of N-methyl pyrrolidone (NMP) under stirring to form uniform anode slurry; coating the slurry on an aluminum foil of a positive electrode current collector, drying, and cold pressing to obtain a positive electrode II with a compacted density of 4.15g/cm 3 。
3) Preparation of negative electrode
Negative electrode one: the preparation method comprises the steps of fully stirring and mixing negative electrode active material graphite, binder styrene butadiene rubber (SBR for short) and thickener sodium carboxymethylcellulose (CMC for short) in a proper amount of deionized water according to a mass ratio of 97.4:1.4:1.2, so that uniform negative electrode slurry is formed; coating the slurry on a copper foil of a negative electrode current collector, drying, and cold pressing to obtain a negative electrode I with a compacted density of 1.80g/cm 3 。
And a second negative electrode: fully stirring and mixing negative electrode active substances graphite, silicon oxide (SiO), thickener sodium carboxymethylcellulose (CMC for short) and modified polyacrylic acid in a proper amount of deionized water according to a mass ratio of 87:10:0.6:2.4, so that uniform negative electrode slurry is formed; coating the slurry on a copper foil of a negative electrode current collector, drying, and cold pressing to obtain a second negative electrode with a compacted density of 1.70g/cm 3 。
3) Isolation film
In the examples, a single-layer PE porous polymer film was used as the separator (S), which had a thickness of 5 μm and a porosity of 39%. The isolating film comprises an inorganic coating and organic particles, wherein the inorganic coating is Al 2 O 3 The organic particles are polyvinylidene fluoride, and the granularity D50 of the organic particles is less than or equal to 10 microns.
4) Preparation of a lithium ion battery:
sequentially stacking the positive electrode, the isolating film and the negative electrode, enabling the isolating film to be positioned between the positive electrode and the negative electrode to play a role of 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 and test result
Examples 1 to 100 and comparative examples 1 to 7
Lithium ion batteries were prepared using the base electrolyte one, the positive electrode two, and the negative electrode one in examples 1 to 100 and comparative examples 1 to 7, and subjected to a cycle test and a high temperature storage test. The specific test method is as follows:
and (3) a cyclic test flow: the battery was charged to 4.45v at 0.7C and to 0.05C at constant voltage at 4.45v at 25C. Then, the discharge was performed at a current of 1C to 3.0V, and the flow of charging at 0.7C and discharging at 1C was repeated for 800 cycles, and the capacity retention rate at this time was recorded.
And (3) floating charge test flow: the battery was discharged to 3.0V at 25C at 0.5C, charged to 4.45V at 0.5C, and charged to 0.05C at constant voltage at 4.45V, and the thickness of the lithium ion battery was measured and recorded as D 0 Placing the mixture in a 45 ℃ oven, charging for 50 days at a constant voltage of 4.45V, monitoring thickness change, recording the thickness as D, and calculating the thickness expansion rate of the floating charge according to the following formula:
thickness expansion ratio (%) = (D-D) of float 0 )÷D 0 ×100％。
And (3) a high-temperature storage test flow: the battery was charged to 4.45V at 25C with a constant current of 0.5C and then charged at constant voltage to a current of 0.05C, and the thickness of the lithium ion battery was tested and recorded as D 1 Placing in an oven at 85deg.C for 24 hr, monitoring the thickness, and recording as D 2 . The thickness expansion rate of the lithium ion battery after being stored for 24 hours at high temperature is calculated according to the following formula:
thickness expansion ratio (%) = (D) 2 -D 1 )÷D 1 ×100％。
The specific test results are shown in the following table.
Table 1 electrolytes of examples 1 to 39 and comparative examples 1 to 3 and test results
Figure PCTCN2020115604-APPB-000016
Figure PCTCN2020115604-APPB-000017
As can be seen from the examples and comparative examples of table 1, the compound of formula I according to the present application can significantly improve the float and high temperature storage properties of the battery. Since the compound of formula I contains cyano groups and cyclic hydrocarbons, the probability of contact of the transition metal with the electrolyte is on the one hand smaller and on the other hand the oxidizing power of the transition metal is reduced (partial lone pair electrons on the cyano groups are obtained). The above test results show that the improvement effect is more excellent when the content of the compound of formula I is 0.01 to 10 wt%.
Examples 15 to 38 additionally contain compounds containing a sulfur-oxygen double bond. From the test results, it can be seen that the combination of the compound of formula I and the compound containing a sulfur-oxygen double bond can further improve the high-temperature storage performance and the floating charge performance.
Table 2 electrolytes of examples 6, 40 to 63 and test results
Figure PCTCN2020115604-APPB-000018
Examples 40 to 63 above show examples of the use of the compounds of formula I of the present application in combination with lithium phosphate salt compounds. Lithium difluorophosphate and lithium tetrafluorooxalate phosphate are positive and negative film forming additives, which can reduce the contact between electrolyte and positive electrode, reduce the consumption of electrolyte and inhibit the gas production. As can be seen from the test results of table 2, the additional addition of the lithium phosphate compound can further improve the high-temperature storage performance and cycle performance of the battery.
Table 3 electrolytes of examples 5, 14, 15, 64 to 84 and comparative examples 4 to 7 and test results
Figure PCTCN2020115604-APPB-000019
Figure PCTCN2020115604-APPB-000020
As the number of cyano groups increases, the solubility of the compounds of formula I decreases. The inventors of the present application have surprisingly found that by using in combination with other polynitrile compounds, it is possible to ensure that the compound of formula I is able to obtain good solubility in the electrolyte, thus exerting its excellent properties. As shown in table 3 above, the combined use of the polynitrile compound and the compound of formula I can effectively and significantly improve the high temperature storage performance and the floating charge performance of the electrochemical device.
Table 4 electrolytes of examples 85 to 100 and test results
Figure PCTCN2020115604-APPB-000021
Figure PCTCN2020115604-APPB-000022
Examples 85 to 100 show examples in which the compound of formula I is used in combination with at least two of a compound containing a sulfur-oxygen double bond, a lithium phosphate salt compound, or a polynitrile compound. The above test results show that the combination of the compound of formula I and at least two of the compound containing a double bond of oxygen and sulfur, the lithium phosphate compound or the polynitrile compound can further improve the high-temperature storage performance and the cycle performance of the electrochemical device.
Examples 101 to 107 and comparative examples 8 to 9
Lithium ion batteries were prepared using the base electrolyte two, the positive electrode one, and the negative electrode one in examples 101 to 107 and comparative examples 8 to 9, and subjected to overcharge tests. The specific test method is as follows:
and (3) an overcharge test flow: the batteries were discharged to 2.8V at 25 ℃ at 0.5C, charged to different voltages as shown in the table at a constant current of 2C (6.8A), charged for 3 hours at a constant voltage, the surface temperature change of the batteries was monitored, the batteries were passed without ignition or smoking, 10 batteries were tested per group, and the number of passing batteries was counted. The specific test results are shown in Table 5.
Table 5 electrolytes of examples 101 to 107 and comparative examples 8 to 9 and test results
Figure PCTCN2020115604-APPB-000023
Figure PCTCN2020115604-APPB-000024
As can be seen from the following test results, the compounds of formula I of the present application, when used in combination with a compound containing a sulfur-oxygen double bond, can significantly improve the overcharge performance of the battery. This is because the compound containing the sulfur-oxygen double bond used in the application can improve the oxidation resistance of the electrolyte on one hand, and can form a stable protective film on the surface of the anode on the other hand, so that lithium crystallization is effectively prevented and direct contact with the electrolyte is reduced, and the compound of the formula I can protect the anode, inhibit the decomposition of the electrolyte, and the combination of the compound and the electrolyte can obviously improve the overcharge performance.
Examples 107 to 112 and comparative examples 10 to 11
Lithium ion batteries were prepared using the base electrolyte three, the positive electrode two, and the negative electrode two in examples 107 to 112 and comparative examples 10 to 11, and subjected to a 60 ℃ high temperature storage test. The specific test method is as follows:
the high-temperature storage test flow at 60 ℃ comprises the following steps: the battery was charged to 4.45V at 25C with a constant current of 0.5C and then charged at constant voltage to a current of 0.05C, and the thickness of the lithium ion battery was tested and recorded as D 0 The method comprises the steps of carrying out a first treatment on the surface of the The mixture was placed in an oven at 60℃for 30 days, and the thickness was monitored and designated as D. The thickness expansion rate of the lithium ion battery after 24 hours of high-temperature storage is calculated according to the following formula:
storage thickness expansion ratio (%) = (D-D) at 60 ℃ high temperature 0 )÷D 0 ×100％。
The specific test results are shown in Table 6.
Table 6 electrolytes and test results of examples 107 to 112 and comparative examples 10 to 11
Figure PCTCN2020115604-APPB-000025
From the above results, it can be seen that the high temperature storage performance is significantly improved after the addition of the compound of formula I according to the present application, compared to comparative examples 9 and 10. The compound of the formula I can improve the stability of an interface of the positive electrode material, and in addition, the compound of the formula I can be reduced to form a film on the surface of a silicon material, so that the surface of a silicon electrode is stabilized, the redox decomposition of electrolyte is inhibited, and the effect of improving high-temperature storage is achieved.
Reference throughout this specification to "some embodiments," "one embodiment," "another example," "an example," "a particular example," or "a partial example" means that at least one embodiment or example in the present application includes the particular feature, structure, material, or characteristic described in the embodiment or example. Thus, descriptions appearing throughout the specification, for example: "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in one example," "in a particular example," or "example," which do not necessarily reference the same embodiments or examples in this application. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.
Although illustrative embodiments have been shown and described, it will be understood by those skilled in the art that the foregoing embodiments are not to be construed as limiting the application and that changes, substitutions and alterations of the embodiments may be made without departing from the spirit, principles and scope of the application.

Claims (11)

  1. An electrolyte comprising at least one compound of formula I:
    Figure PCTCN2020115604-APPB-100001
    wherein:
    ring A is C 3 -C 10 Cyclic hydrocarbons, R 11 Each independently selected from: substituted or unsubstituted C 1 -C 10 Alkylene, substituted or unsubstituted C 2 -C 10 Alkenylene or substituted or unsubstituted C 2 -C 10 Alkynylene; wherein, when substituted, the substituent is halogen;
    R 12 each independently selected from the following: 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; wherein, when substituted, the substituent is halogen;
    n is an integer from 1 to 7 and m is an integer from 1 to 19.
  2. The electrolyte of claim 1, wherein the compound of formula I comprises at least one of the following compounds:
    Figure PCTCN2020115604-APPB-100002
    Figure PCTCN2020115604-APPB-100003
  3. the electrolyte of claim 1, wherein the compound of formula I is present in an amount of 0.01% to 5% based on the total weight of the electrolyte.
  4. The electrolyte of claim 1, wherein the electrolyte further comprises at least one of: a compound containing a sulfur-oxygen double bond, a polynitrile compound, a lithium salt containing a P-O bond or fluoroethylene carbonate.
  5. The electrolyte according to claim 4, wherein:
    The compound containing the oxygen-containing double bond comprises at least one of the following substances: sulfolane, 1, 3-propane sultone, 1, 4-butane sultone, methyl disulfonate, 1, 3-propane disulfonate, vinyl sulfate, 4-methyl vinyl sulfate, 2, 4-butane sultone, 1, 3-butane sultone, 1-fluoro-1, 3-propane sultone, 2-fluoro-1, 3-propane sultone, 3-fluoro-1, 3-propane sultone, propenyl-1, 3-sulfonic acid lactone, propylene sulfate or vinyl thiosulfate;
    the polynitrile compound includes at least one of the following: 1,2, 3-tris (2-cyanoethoxy) propane, 1,3, 6-hexanetricarbonitrile, 1, 2-bis (2-cyanoethoxy) ethane, succinonitrile or adiponitrile;
    the lithium salt containing the P-O bond comprises at least one of lithium difluorophosphate, lithium difluorobis (oxalato) phosphate or lithium tetrafluorooxalato phosphate.
  6. The electrolyte according to claim 4, wherein when the electrolyte comprises the compound containing a sulfur-oxygen double bond, the content of the compound containing a sulfur-oxygen double bond is 0.01% to 10% based on the total weight of the electrolyte;
    when the polynitrile compound is included, the mass ratio of the compound of the formula I to the polynitrile compound is less than or equal to 1;
    When the lithium salt containing the P-O bond is included, the mass ratio of the compound of the formula I to the lithium salt containing the P-O bond is less than 5;
    when the fluoroethylene carbonate is included, the content of the fluoroethylene carbonate is 1 to 10% based on the total weight of the electrolyte.
  7. An electrochemical device comprising the electrolyte of any one of claims 1-6.
  8. The electrochemical device of claim 7, wherein the electrochemical device further comprises a separator comprising a porous polymer layer having a fluoropolymer disposed thereon.
  9. The electrochemical device of claim 8, wherein the separator further comprises inorganic particles comprising boehmite, mg (OH) 2 、SrTiO 3 、SnO 2 、CeO 2 、MgO、NiO、CaO、ZnO、ZrO 2 、Y 2 O 3 、Al 2 O 3 、TiO 2 Or SiC.
  10. The electrochemical device of claim 8, wherein the separator has a porosity of 20% to 65%.
  11. An electronic device comprising the electrochemical device of any one of claims 7-10.
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