CN111697266B

CN111697266B - Electrolyte solution, and electrochemical device and electronic device including the same

Info

Publication number: CN111697266B
Application number: CN202010575699.XA
Authority: CN
Inventors: 熊亚丽; 管明明; 崔辉; 郑建明
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2020-06-22
Filing date: 2020-06-22
Publication date: 2022-02-15
Anticipated expiration: 2040-06-22
Also published as: CN111697266A

Abstract

The present application relates to an electrolyte solution, and an electrochemical device and an electronic device including the same. The electrolyte includes a cyano-containing carboxylic acid ester. The electrochemical device of the present application, which contains the electrolyte, can satisfy high voltage use requirements and has improved high temperature cycle performance and high temperature storage performance.

Description

Electrolyte solution, and electrochemical device and electronic device including the same

Technical Field

The present disclosure relates to the field of energy storage technologies, and more particularly, to an electrolyte, and an electrochemical device and an electronic device including the same.

Background

Compared with other rechargeable batteries, the lithium ion battery has the advantages of high energy density, high working voltage, long cycle life, low self-discharge and the like. At present, small-capacity lithium ion batteries are successfully applied to mobile phones, digital cameras and notebook computers, and large-capacity high-power lithium ion power batteries also have good application prospects. However, when the conventional lithium ion battery is applied in a high-temperature environment, a side reaction is easily generated to generate gas, so that the expansion thickness of the battery is increased, and the normal use is influenced.

With the continuous deepening of practical application, the demand for high energy density lithium ion batteries is more and more urgent. The energy density is affected by two factors, the gram capacity exertion and the operating voltage of the electrode material. Currently, the voltage range of the lithium ion battery is mainly 3.0V to 4.2V, and the gram capacity of the electrode material is improved while the working upper limit voltage of the lithium ion battery is improved (for example, the working upper limit voltage is improved to 4.45V or more than 4.48V), so that the energy density of the lithium ion battery is improved.

However, in the case of high voltage application, the positive electrode potential is relatively increased, so that the reactivity of the positive electrode active material is enhanced, and the electrolyte is likely to undergo oxidation reaction, particularly in the case of high temperature application. By using some additives, the storage performance of the battery can be improved, but the impedance of the battery is greatly increased, and the rate performance and cycle performance thereof are deteriorated. Therefore, in order to meet the use requirements of high voltage batteries, it is necessary to develop a novel electrolyte for lithium ion batteries to improve the high temperature storage performance of the lithium ion batteries without significant deterioration or improvement of other electrical properties of the batteries.

Disclosure of Invention

The present application provides an electrolyte and an electrochemical device including the same in an attempt to solve at least one of the problems existing in the related art to at least some extent.

The application provides an electrolyte comprising cyano carboxylic ester, which can improve the high-temperature cycle performance and the high-rate discharge performance of an electrochemical device and reduce the internal resistance of a battery, and is used for solving the problems of the cycle and the high-rate charge of the electrochemical device.

According to an embodiment of the present application, there is provided an electrolyte including a cyano-containing carboxylic acid ester represented by formula I

Wherein R is₁₁Is substituted or unsubstituted C₁To C₆Straight or branched alkyl, substituted or unsubstituted C₂To C₇Straight or branched alkenyl, substituted or unsubstituted C₃To C₈Straight or branched alkynyl, substituted or unsubstituted C₃To C₈Cycloalkyl or substituted or unsubstituted C₆To C₁₂Aryl, wherein when substituted, the substituent is a halogen atom or cyano; wherein R is₁₂、R₁₃Each independently selected from a halogen atom, a substituted or unsubstituted C₁To C₆Straight or branched alkyl, substituted or unsubstituted C₂To C₇Straight or branched alkenyl, substituted or unsubstituted C₃To C₈Straight or branched alkynyl, substituted or unsubstituted C₁To C₆Straight or branched alkoxy or substituted or unsubstituted C₆To C₁₂Aryl, wherein when substituted, the substituent is a halogen atom.

According to an embodiment of the present application, in the electrolyte, the cyano group-containing carboxylic acid ester includes:

at least one of; wherein the weight percentage of the cyano-containing carboxylic ester is 0.01 wt% to 6 wt% based on the weight of the electrolyte.

According to an embodiment of the present application, the electrolyte further comprises lithium difluorophosphate in a weight percentage of 0.01 wt% to 1 wt% based on the weight of the electrolyte.

According to an embodiment of the present application, a weight percentage X of the cyano-containing carboxylic acid ester to a weight percentage Y of the lithium difluorophosphate satisfy X + Y <5.5 wt% and X/Y >1/5, based on the weight of the electrolyte.

According to an embodiment of the application, the electrolyte further comprises a cyclic sulfur-containing compound represented by formula II:

wherein R is₂₁、R₂₂、R₂₃、R₂₄Each independently selected from a hydrogen atom, a substituted or unsubstituted C₁To C₆Straight or branched alkyl, substituted or unsubstituted C₂To C₆Straight or branched alkenyl, substituted or unsubstituted C₂To C₆Straight or branched alkynyl, substituted or unsubstituted C₁To C₆Straight or branched alkoxy, substituted or unsubstituted C₆To C₁₂Aryl, substituted or unsubstituted C₁To C₆Heterocyclic radical, sulfonyl, substituted or unsubstituted C₂To C₇Alkylcarbonyl, substituted or unsubstituted C₂To C₇Alkenylcarbonyl, substituted or unsubstituted C₃To C₇Alkynylcarbonyl or substituted or unsubstituted C₇To C₁₃An arylcarbonyl group, wherein the heterocyclic group comprises at least one of O, S, N or P, wherein when substituted, the substituent is at least one of a halogen atom or a vinyl sulfate group; wherein n1 and n2 are each independently 0 or 1; wherein B is carbonyl, ester, sulfonate, sulfate, substituted or unsubstitutedSubstituted C₁To C₆Alkylene, substituted or unsubstituted C₂To C₆Alkenylene, substituted or unsubstituted C₂To C₆Alkynylene or vinyl sulfate, wherein when substituted, the substituent is halogen atom, C₁To C₆Alkyl ester group, C₂To C₆Alkenyl ester group, C₂To C₆Alkynyl ester group or C₇To C₁₃At least one of aryl ester groups; wherein the weight percentage of the cyclic sulfur compound is 0.1 wt% to 6 wt% based on the weight of the electrolyte.

According to an embodiment of the present application, in the electrolyte, the cyclic sulfur compound includes:

at least one of (1).

According to an embodiment of the present application, the electrolyte further comprises a fluorocarboxylate ester represented by formula III:

wherein R is₃₁、R₃₂Each independently selected from substituted or unsubstituted straight or branched C₁To C₆Alkyl, substituted or unsubstituted straight or branched C₂To C₆Alkenyl or substituted or unsubstituted, straight or branched C₂To C₆Alkynyl, wherein when substituted, the substituent is an F atom; wherein the fluorocarboxylic acid ester represented by the formula III contains at least one F atom; wherein the fluorocarboxylic acid ester is present in an amount of 0.01 to 20% by weight, based on the weight of the electrolyte.

According to an embodiment of the present application, in the electrolyte, the fluorocarboxylic acid ester includes:

at least one of (1).

According to an embodiment of the present application, there is provided an electrochemical device including a positive electrode, a negative electrode, a separator, and any one of the above-described electrolytic solutions.

According to an embodiment of the present application, in an electrochemical device, the negative electrode includes a negative electrode current collector and a negative electrode active material layer, and the content of the fluorocarboxylate is 0.045g to 0.65g per gram of the negative electrode active material layer.

According to an embodiment of the present application, there is provided an electronic device including any one of the electrochemical devices described above.

Additional aspects and advantages of embodiments of the present application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of the present application.

Detailed Description

Embodiments of the present application will be described in detail hereinafter, and the embodiments of the present application should not be construed as limiting the present application.

As used herein, the terms "substantially", "substantially" and "about" are used to describe and illustrate minor variations. When used in conjunction with an event or circumstance, the terms can refer to instances where the event or circumstance occurs precisely as well as instances where the event or circumstance occurs in close proximity. For example, when used in conjunction with numerical values, the term can refer to a range of variation that is less than or equal to ± 10% of the stated 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 numerical values are considered to be "substantially" identical if the difference between the two numerical 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 mean 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 linked by the term "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 a only; only B; or A and B. In another example, if items A, B and C are listed, the phrase "at least one of A, B and C" means a only; 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 component or multiple components. Item B may comprise a single component or multiple components. Item C may comprise a single component or multiple components.

The term "alkyl" is intended to be a straight chain saturated hydrocarbon structure having from 1 to 20 carbon atoms. "alkyl" is also contemplated to be a branched or cyclic hydrocarbon structure having from 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 an alkyl group having a particular carbon number is specified, all geometric isomers having that carbon number are intended to be encompassed; thus, for example, "butyl" is meant 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 "cycloalkyl" encompasses cyclic alkyl groups. The cycloalkyl group may be a cycloalkyl group of 2 to 20 carbon atoms, a cycloalkyl group of 6 to 20 carbon atoms, a cycloalkyl group of 2 to 10 carbon atoms, a cycloalkyl group of 2 to 6 carbon atoms. For example, cycloalkyl groups can be cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. In addition, cycloalkyl groups may be optionally substituted.

The term "alkenyl" refers to a monovalent unsaturated hydrocarbon group that can be straight or branched chain 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, and may be, for example, 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, by way of example, ethenyl, n-propenyl, isopropenyl, n-but-2-enyl, but-3-enyl, n-hex-3-enyl, and the like. In addition, the alkenyl group may be optionally substituted.

The term "alkynyl" refers to a monovalent unsaturated hydrocarbon group that can be straight-chain 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 may be, for example, an alkynyl group of 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, the alkynyl group may be optionally substituted.

The term "aryl" encompasses monocyclic and polycyclic ring systems. Polycyclic rings may have two or more rings in which two carbons are common to two adjoining rings (the rings are "fused"), wherein at least one of the rings is aromatic, e.g., as it isThe ring may be cycloalkyl, cycloalkenyl, aryl, heterocycle and/or heteroaryl. For example, the aryl group may be C₆To C₅₀Aryl radical, C₆To C₄0 aryl radical, C₆To C₃₀Aryl radical, C₆To C₂₀Aryl or C₆To C₁₀And (4) an aryl group. Representative aryl groups include, for example, phenyl, methylphenyl, propylphenyl, isopropylphenyl, benzyl, and naphthalen-1-yl, naphthalen-2-yl, and the like. In addition, the aryl group may be optionally substituted.

The term "heterocyclyl" encompasses aromatic and non-aromatic cyclic groups. Heteroaromatic cyclic groups also mean heteroaryl groups. In some embodiments, the heteroaromatic ring group and the heteronon-aromatic ring group are C including at least one heteroatom₁To C₅₀Heterocyclic group, C₁To C₄₀Heterocyclic group, C₁To C₃₀Heterocyclic group, C₁To C₂₀Heterocyclic group, C₁To C₁₀Heterocyclic group, C₁To C₆A heterocyclic group. Such as morpholinyl, piperidinyl, pyrrolidinyl, and the like, as well as cyclic ethers, such as tetrahydrofuran, tetrahydropyran, and the like. In addition, the heterocyclic group may be optionally substituted.

As used herein, the term "heteroatom" encompasses O, S, P, N, B or an isostere thereof.

As used herein, the term "halogen" may be F, Cl, Br or I.

Embodiments of the present application provide an electrolyte including a cyano carboxylic acid ester and an electrochemical device including the same. In some embodiments, the electrochemical device is a lithium ion battery.

First, electrolyte

An electrolyte is provided that includes a cyano-containing carboxylic acid ester.

Carboxylic acid esters containing cyano groups

In some embodiments, the cyano-containing carboxylic acid ester has the structure shown in formula I:

in the formula I, R₁₁Is substituted or unsubstituted C₁To C₆Straight or branched alkyl, substituted or unsubstituted C₂To C₇Straight or branched alkenyl, substituted or unsubstituted C₃To C₈Straight or branched alkynyl, substituted or unsubstituted C₃To C₈Cycloalkyl or substituted or unsubstituted C₆To C₁₂Aryl, wherein when substituted, the substituent is a halogen atom or cyano; r₁₂、R₁₃Each independently selected from a halogen atom, a substituted or unsubstituted C₁To C₆Straight or branched alkyl, substituted or unsubstituted C₂To C₇Straight or branched alkenyl, substituted or unsubstituted C₃To C₈Straight or branched alkynyl, substituted or unsubstituted C₁To C₆Straight or branched alkoxy or substituted or unsubstituted C₆To C₁₂Aryl, wherein when substituted, the substituent is a halogen atom.

In some embodiments, the cyano-containing carboxylic acid ester comprises:

at least one of (1).

The alpha hydrogen attached to the carbonyl (C ═ O) and cyano (-CN) groups in formula I is completely substituted (i.e., R₁₂And R₁₃) And (4) substitution. The alpha-position H atom is very active and can easily generate H in the formation stage₂The gas causes the electrochemical device to generate gas expansion deformation, and the active H at the alpha position in the formula I is completely replaced, so that the gas generation problem in the formation stage can be inhibited, and the safety performance of the electrochemical device is improved.

The energy level of the lone pair electrons of the cyano-group in the formula I is close to the energy level of the vacant orbit at the outermost layer of the transition metal atom in the anode active material, so that organic molecules containing the cyano-group can be subjected to complex adsorption on the surface of the anode. The organic molecules adsorbed on the surface of the anode can well separate the easily-oxidized components in the electrolyte from the surface of the anode, so that the oxidation of the anode surface of the electrochemical device in a charging state to the electrolyte is greatly reduced, and the high-temperature storage performance of the electrochemical device is effectively improved. In addition, the cyano-containing carboxylic ester has a low oxidation potential, is easy to preferentially oxidize at a positive electrode to form a film under high voltage, reduces the oxidation of electrolyte at the positive electrode, and further improves the high-temperature storage performance of the electrochemical device.

In some embodiments, the weight percent of the cyano-containing carboxylic acid ester is about 0.01 wt% to about 6 wt% based on the weight of the electrolyte. In some embodiments, the weight percent of cyano-containing carboxylic acid ester is about 0.05 weight percent, about 0.1 weight percent, about 0.2 weight percent, about 0.3 weight percent, about 0.4 weight percent, about 0.5 weight percent, about 1 weight percent, about 2 weight percent, about 3 weight percent, about 4 weight percent, about 5 weight percent, about 6 weight percent, about 0.01 weight percent to about 0.5 weight percent, about 0.1 weight percent to about 1 weight percent, about 0.1 weight percent to about 3 weight percent, about 1 weight percent to about 5 weight percent, or about 3 weight percent to about 6 weight percent, and the like, based on the weight of the electrolyte. When the weight percentage of the cyano carboxylic acid ester is less than 0.01 wt%, the formed protective film is insufficient, and the influence on the performance of the electrochemical device is small; when the weight percentage of the cyano carboxylic acid ester is more than 6 wt%, the formed film resistance is large, and the performance of the electrochemical device is deteriorated.

Lithium difluorophosphate

In some embodiments, the electrolyte may include lithium difluorophosphate (LiPO) in addition to the cyano-containing carboxylic acid ester₂F₂). Lithium difluorophosphate can increase LiF component in the organic protective film and increase the stability of the organic protective layer in the interface film, thereby improving the cycle performance and reducing the impedance.

In some embodiments, the weight percentage of lithium difluorophosphate is 0.01 wt% to 1 wt% based on the weight of the electrolyte. In some embodiments, the weight percentage of lithium difluorophosphate is less than about 0.5 wt% based on the weight of the electrolyte. In some embodiments, the weight percentage of lithium difluorophosphate is less than about 0.05 wt%, less than about 0.1 wt%, less than about 0.2 wt%, less than about 0.3 wt%, or less than about 0.4 wt%, etc., based on the weight of the electrolyte.

In some embodiments, the weight percent X of the cyano-containing carboxylic acid ester and the weight percent Y of the lithium difluorophosphate satisfy X + Y <5.5 wt% and X/Y >1/5, based on the weight of the electrolyte.

Cyclic sulfur-containing compounds

In some embodiments, the electrolyte may include a cyclic sulfur-containing compound as shown in formula II in addition to the cyano-containing carboxylic acid ester:

in formula II, R₂₁、R₂₂、R₂₃、R₂₄Each independently selected from a hydrogen atom, a substituted or unsubstituted C₁To C₆Straight or branched alkyl, substituted or unsubstituted C₂To C₆Straight or branched alkenyl, substituted or unsubstituted C₂To C₆Straight or branched alkynyl, substituted or unsubstituted C₁To C₆Straight or branched alkoxy, substituted or unsubstituted C₆To C₁₂Aryl, substituted or unsubstituted C₁To C₆Heterocyclic radical, sulfonyl, substituted or unsubstituted C₂To C₇Alkylcarbonyl, substituted or unsubstituted C₂To C₇Alkenylcarbonyl, substituted or unsubstituted C₃To C₇Alkynylcarbonyl or substituted or unsubstituted C₇To C₁₃An arylcarbonyl group, wherein the heterocyclic group comprises at least one of O, S, N or P, wherein when substituted, the substituent is at least one of a halogen atom or a vinyl sulfate group; n1 and n2 are each independently 0 or 1; b is carbonyl, ester, sulfonate, sulfate, substituted or unsubstituted C₁To C₆Alkylene, substituted or unsubstituted C₂To C₆Alkenylene, substituted or unsubstituted C₂To C₆Alkynylene or vinyl sulfate, wherein when substituted, the substituent is halogen atom, C₁To C₆Alkyl ester group, C₂To C₆Alkenyl ester group, C₂To C₆Alkynyl estersRadical or C₇To C₁₃At least one aryl ester group.

In some embodiments, the cyclic sulfur-containing compound comprises:

at least one of (1).

The annular sulfur-containing compound can form a film on the anode, the film is a sulfur-containing substance, a passivation layer formed by the substances has strong polarity, good adhesion to the anode and difficult shedding, and can well separate easily-oxidizable components in the electrolyte from the surface of the anode, so that the oxidation of the anode surface of the lithium ion battery in a charging state to the electrolyte is greatly reduced, and the cycle performance of the lithium ion battery can be effectively improved; at the same time, the excellent space structure is beneficial to Li⁺The impedance of the electrochemical device may be reduced by the transmission.

In some embodiments, the weight percent of the cyclic sulfur compound is from about 0.1 wt% to about 6 wt% based on the weight of the electrolyte. In some embodiments, the weight percent of the cyclic sulfur-containing compound is about 0.1 wt%, about 0.5 wt%, about 0.8 wt%, about 1 wt%, about 1.5 wt%, about 2 wt%, about 2.5 wt%, about 3 wt%, about 3.5 wt%, about 4 wt%, about 4.5 wt%, about 5 wt%, about 5.5 wt%, about 1 wt% to about 2 wt%, about 2 wt% to about 3 wt%, or about 2 wt% to about 5 wt%, etc., based on the weight of the electrolyte.

Fluorocarboxylic acid esters

In some embodiments, the electrolyte may further comprise a fluorocarboxylate ester as shown in formula III:

in formula III, R₃₁、R₃₂Each independently selected from substituted or unsubstituted straight or branched C₁To C₆Alkyl, substituted or unsubstituted straight or branched C₂To C₆Alkenyl or substituted or unsubstituted, straight or branched C₂To C₆Alkynyl radical, in whichWhen substituted, the substituent is an F atom; wherein the fluorocarboxylic acid ester represented by the formula III contains at least one F atom.

In some embodiments, the fluorocarboxylic acid ester comprises:

at least one of (1).

The stability of the fluorocarboxylate is good, and the oxidation resistance of an electrochemical device system can be improved by means of the strong oxidation property of fluorine atoms, so that the effect of improving safety is achieved.

In some embodiments, the weight percent of the fluorocarboxylic acid ester is from about 0.01 to about 20 weight percent, based on the weight of the electrolyte. In some embodiments, the weight percent of fluorocarboxylic acid ester is about 0.05 wt%, about 1 wt%, about 3 wt%, about 5 wt%, about 10 wt%, about 12 wt%, about 15 wt%, about 18 wt%, about 1 wt% to about 5 wt%, about 5 wt% to about 10 wt%, about 1 wt% to about 10 wt%, about 5 wt% to about 15 wt%, or about 5 wt% to about 20 wt%, etc., based on the weight of the electrolyte. When the weight percentage of the fluorocarboxylate is less than 0.01 wt%, the positive and negative electrodes cannot be effectively passivated, and thus the side reaction between the nonaqueous electrolytic solution and the positive and negative electrodes cannot be effectively prevented. When the weight percentage of the fluorocarboxylate is greater than 20 wt%, the formed interface resistance of the positive and negative electrodes is large, which deteriorates the dynamic properties of the electrolyte and the low-temperature properties of the electrochemical device.

In some embodiments, the electrolyte further comprises a non-aqueous organic solvent, which may comprise a carbonate. The carbonate may be any kind of carbonate as long as it can be used as the nonaqueous electrolyte organic solvent, for example, cyclic carbonate or chain carbonate, and the like. In some embodiments, the cyclic carbonate may be ethylene carbonate, propylene carbonate, butylene carbonate, γ -butyrolactone, pentylene carbonate, fluoroethylene carbonate, and the like. In some embodiments, the chain carbonate may be dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, or the like, but it is not limited thereto, and may also be a halogenated derivative thereof. In addition, these compounds may be used alone or in combination.

In some embodiments, the electrolyte further comprises a lithium salt selected from at least one or more of inorganic lithium salts and organic lithium salts. In some embodiments, the lithium salt is selected from lithium hexafluorophosphate (LiPF)₆) Lithium tetrafluoroborate (LiBF)₄) Lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), lithium bis (oxalato) borate (LiBOB), or lithium difluoro (oxalato) borate (lidob). In some embodiments, the lithium salt in the electrolyte is lithium hexafluorophosphate.

In some embodiments, the concentration of the lithium salt in the electrolyte is from about 0.6mol/L to about 2 mol/L. In some embodiments, the concentration of the lithium salt in the electrolyte is from about 1mol/L to about 1.25mol/L, from about 0.6mol/L to about 1mol/L, from about 1mol/L to about 1.5mol/L, from about 1mol/L to about 2mol/L, about 0.8mol/L, about 1.2mol/L, or about 1.8mol/L, and the like.

Two, electrochemical device

Embodiments of the present application also provide an electrochemical device comprising a positive electrode, a negative electrode, a separator, and an electrolyte of the present application. The electrochemical device of the present application may include any device in which electrochemical reactions occur, 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 includes 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; a separator interposed between the positive electrode and the negative electrode; and an electrolyte of the present application.

Electrolyte solution

The electrolyte used in the electrochemical device of the present application is any of the electrolytes described above in the present application. In addition, the electrolyte used in the electrochemical device of the present application may further include other electrolytes within a range not departing from the gist of the present application.

Positive electrode

In some embodiments, the positive electrode includes a current collector and a positive active material layer on the current collector, the positive active material layer including a positive active material. The positive electrode active material includes at least one lithiated intercalation compound that reversibly intercalates and deintercalates lithium ions. In some embodiments, the positive electrode active material includes a composite oxide. In some embodiments, the composite oxide contains lithium and at least one element selected from cobalt, manganese, and nickel.

In some embodiments, the positive active material is selected from lithium cobaltate (LiCoO)₂) Lithium Nickel Cobalt Manganese (NCM) ternary material, lithium iron phosphate (LiFePO)₄) Lithium manganate (LiMn)₂O₄) Or any combination thereof. In some embodiments, the positive active material is a mixture of lithium cobaltate and a lithium nickel manganese cobalt ternary material, wherein the mixture is mixed in a ratio of 1:9<Lithium cobaltate-lithium nickel manganese cobalt<9:1. In some embodiments, the mixture is mixed at a ratio of 2:8<Lithium cobaltate-lithium nickel manganese cobalt<4:6. The mixture of the lithium cobaltate and the lithium nickel manganese cobalt ternary material is used as the positive active material, so that the safety performance of the positive active material can be improved. Meanwhile, the quantity of transition metals is increased after the lithium cobaltate and the lithium nickel manganese cobalt ternary material are mixed, the transition metals play a certain catalytic role in film formation of the electrolyte, and the additive can play a more effective film formation effect.

In some embodiments, the positive electrode active material may have a coating layer on a surface thereof, or may be mixed with another compound having a coating layer. The coating may comprise at least one coating element compound selected from the group consisting of an oxide of the coating element, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element and an oxycarbonate of the coating element. The compounds used for the coating may be amorphous or crystalline.

In some embodiments, the coating elements contained in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Ti, Sn, Ge, Ga, B, As, Ti, Sn, Ge, Ga, Ti, Ge, Ga, B, As, Ti, Sn, Ti, Ge, Ti, Ge, Ga, Ti, and Ga, Ti, Si, Ti, Si, Ge, Si, Ge, Si, Ge, Ga, Si, Ge, and As, Si, Ge, Ga, Ti, Si,Zr, P, or any combination thereof. In some embodiments, the coating in the coating layer may be AlPO₄、Mg₃(PO₄)₂、Co₃(PO₄)₂、AlF₃、MgF₂、CoF₃、NaF、B₂O₃At least one of (1). In some embodiments, the coating element is present in the coating layer in an amount of about 0.01% to about 10% based on the weight of the positive electrode active material. The coating layer may be applied by any method as long as the method does not adversely affect the properties of the positive electrode active material. For example, the method may include any coating method known to the art, such as spraying, dipping, and the like.

The positive active material layer further includes a binder, and optionally a conductive material. The binder improves the binding of the positive electrode active material particles to each other, and also improves the binding of the positive electrode active material to the current collector.

In some embodiments, the adhesive includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1, 1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy, nylon, and the like.

In some embodiments, the conductive material includes, but is not limited to: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from the group consisting of metal powder, metal fiber, copper, nickel, aluminum, silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

In some embodiments, the current collector may be, but is not limited to, aluminum.

The positive electrode may be prepared by a preparation method well known in the art. For example, the positive electrode can be obtained by: the active material, the conductive material, and the binder are mixed in a solvent to prepare an active material composition, and the active material composition is coated on a current collector. In some embodiments, the solvent may include, but is not limited to, N-methylpyrrolidone, and the like.

In some embodiments, the positive electrode is made by forming a positive electrode material on a current collector using a positive electrode active material layer including a lithium transition metal-based compound powder and a binder.

In some embodiments, the positive active material layer may be generally fabricated by: the positive electrode active material and a binder (a conductive material, a thickener, and the like, which are used as needed) are dry-mixed to form a sheet, and the obtained sheet is pressure-bonded to a positive electrode current collector, or these materials are dissolved or dispersed in a liquid medium to form a slurry, which is applied to the positive electrode current collector and dried. In some embodiments, the material of the positive electrode active material layer includes any material known in the art.

Negative electrode

The negative electrode used in the electrochemical device of the present application includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer contains a negative electrode active material, and the specific kind of the negative electrode active material is not particularly limited and can be selected as required. Specifically, the negative active material may be selected from lithium metal, structured lithium metal, natural graphite, artificial graphite, mesophase micro carbon spheres (MCMB), hard carbon, soft carbon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO₂Spinel-structured lithiated TiO₂-Li₄Ti₅O₁₂And Li-Al alloy.

In some embodiments, the fluorocarboxylate is present in an amount of about 0.045g to about 0.65g per gram of anode active material layer. In some embodiments, the amount of fluorocarboxylate is about 0.05g, about 0.1g, about 0.2g, about 0.3g, about 0.4g, about 0.5g, about 0.6g, about 0.1g to about 0.45g, or about 0.1g to about 0.6g, etc., per gram of anode active material layer.

In some embodiments, the electrochemical device is a lithium ion secondary battery. In order to prevent unintentional precipitation of lithium metal on the anode during charging, the electrochemical equivalent of the anode active material capable of intercalating and extracting lithium ions is preferably larger than that of the cathode. Therefore, the amounts of the positive electrode active material and the negative electrode active material need to be adjusted accordingly to obtain a high energy density. In some embodiments, the ratio of the negative electrode capacity to the positive electrode capacity may be from about 1.01 to about 1.2.

Isolation film

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 substance or the like formed of a material 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 film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used.

At least one surface of the substrate layer is provided with a surface treatment layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or 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 more of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium dioxide, 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 a combination of more of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene. The polymer layer comprises a polymer, and the material of the polymer comprises at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene).

In some embodiments, the present application provides a lithium ion battery comprising the above-described positive electrode, negative electrode, separator, and electrolyte, the electrolyte being any of the electrolytes described previously herein.

In some embodiments, the present application also provides a lithium ion battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, an electrolyte, and a packaging foil; the positive electrode comprises a positive current collector and a positive film layer coated on the positive current collector; the negative electrode comprises a negative electrode current collector and a negative electrode film layer coated on the negative electrode current collector; the electrolyte is any one of the electrolytes described in the application.

Third, application

The electrochemical device has excellent high-temperature cycle performance, high-rate discharge performance and reduced internal resistance, so that the electrochemical device manufactured by the electrochemical device is suitable for electronic equipment in various fields.

The use of the electrochemical device of the present application is not particularly limited, and it may be used for any use known in the art. In one embodiment, the electrochemical device of the present application can be used in, but is not limited to, notebook computers, pen-input computers, mobile computers, electronic book players, cellular phones, portable facsimile machines, portable copiers, portable printers, headphones, video recorders, liquid crystal televisions, portable cleaners, portable CDs, mini-discs, transceivers, electronic organizers, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting fixtures, toys, game machines, clocks, power tools, flashlights, cameras, household large batteries, lithium ion capacitors, and the like.

Fourth, example

The following describes performance evaluation according to examples and comparative examples of lithium ion batteries of the present application.

Preparation of lithium ion battery

(1) Preparation of the Positive electrode

Mixing lithium cobaltate, conductive carbon black and polyvinylidene fluoride according to a weight ratio of 96:2:2, adding N-methyl pyrrolidone, and stirring under the action of a vacuum stirrer until a system becomes uniform and transparent to obtain anode slurry, wherein the solid content of the anode slurry is 75 wt%; uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil; drying the aluminum foil at 85 ℃, then carrying out cold pressing, cutting into pieces, slitting, and drying for 4h at 85 ℃ under a vacuum condition to obtain the anode.

(2) Preparation of the negative electrode

Mixing artificial graphite, sodium carboxymethylcellulose and styrene butadiene rubber according to a weight ratio of 97:1:2, adding deionized water, and obtaining negative electrode slurry under the action of a vacuum stirrer, wherein the solid content of the negative electrode slurry is 54 wt%; uniformly coating the negative electrode slurry on a copper foil of a negative electrode current collector; and drying the copper foil at 85 ℃, then carrying out cold pressing, cutting and slitting, and drying for 12h at 120 ℃ under a vacuum condition to obtain the cathode.

(3) Preparation of the electrolyte

Mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) in a dry argon atmosphere glove box according to the mass ratio of EC to EMC to DEC to 30:50:20, adding an additive, dissolving and fully stirring, and adding lithium salt LiPF₆And mixing uniformly to obtain the electrolyte. In the electrolyte, LiPF₆The concentration of (2) is 1 mol/L. The specific types and weight percentages of the additives in the electrolyte are shown in the following table. In each table, the weight percentage of the additive is a weight percentage calculated based on the weight of the electrolyte.

(4) Preparation of the separator

A7 μm thick polyethylene film was used.

(5) Preparation of lithium ion battery

Stacking the anode, the isolating film and the cathode in sequence to enable the isolating film to be positioned between the anode and the cathode to play an isolating role, and then winding to obtain a bare cell; and (3) after welding a tab, placing the bare cell in an outer packaging foil aluminum-plastic film, injecting the prepared electrolyte into the dried bare cell, and performing vacuum packaging, standing, formation (charging to 3.3V at a constant current of 0.02C and then charging to 3.6V at a constant current of 0.1C), shaping, capacity testing and other processes to obtain the soft package lithium ion battery (with the thickness of 3.3mm, the width of 39mm and the length of 96 mm).

Test method

The following electrolytes and lithium ion batteries of examples and comparative examples were prepared according to the above-described methods, and the following tests were performed on the lithium ion batteries, respectively.

(1) High-temperature storage performance test of lithium ion battery

Discharging the lithium ion battery to 3.0V at 25 deg.C at 0.5C, charging to 4.45V at 0.7C, constant-voltage charging to current of 0.05C at 4.45V, and measuring and recording the thickness H of the lithium ion battery with micrometer₁₁Placing the lithium ion battery in an oven at 85 ℃, standing for 16H, and testing and recording the thickness H of the lithium ion battery by using a micrometer after the lithium ion battery is finished₁₂. Thickness expansion ratio ═ H₁₂-H₁₁)/H₁₁×100％。

(2) High temperature cycle testing of lithium ion batteries

Placing the lithium ion battery in a constant temperature box at 45 ℃, standing for 30 minutes to keep the temperature of the lithium ion battery constant, charging the lithium ion battery at the constant temperature of 0.7 ℃ to 4.45V, and then keeping the voltage constant to 0.05 ℃; the discharge conditions were: discharging to 3.0V at 0.5C, and standing for 5 minutes. The capacity retention rate after the battery was cycled 500 times was calculated by such charge/discharge with the discharge capacity of the first cycle as 100%.

The capacity retention (%) after 500 cycles of the lithium ion battery was equal to the discharge capacity at 500 cycles/the discharge capacity at 1 cycle × 100%.

(3) High voltage lithium ion battery DC impedance DCR (0 ℃) test

The lithium ion battery is tested according to the following steps: 1) standing for 4h in a high-low temperature box at 0 ℃; 2) charging at 0.1 deg.C and constant current for 4.45V, charging at constant voltage to 0.05 deg.C, and standing for 10 min; 3) discharging to 3.4V at constant current of 0.1C, and standing for 5min (to obtain actual capacity); 4) standing for 5min, charging to 4.45V at constant current of 0.1C, and charging to 0.05C at constant voltage (calculated by actual capacity obtained in step 3); 5) standing for 10 min; 6) constant current discharge at 0.1C for 8h (calculated from the actual capacity obtained in step 3), and recording the voltage at this time as V1; 7)1C constant current discharge for 1s (the capacity is calculated by the marked capacity of the battery), and the voltage at the moment is recorded as V2; 8) and calculating the direct current impedance corresponding to the 20% SOC state of the battery, wherein the 20% SOC direct current impedance is (V1-V2)/1C.

(4) Overcharge test

The lithium ion battery was discharged to 3.0V at 25 ℃ at 0.5C, left to rest for 5 minutes, then charged to 7V at 3C constant current, and charged at 7V for 1h at constant voltage. And if the lithium ion battery passes the test, taking 5 lithium ion batteries in each test, and recording the number of the lithium ion batteries passing the test.

Test results

Table 1 shows electrolyte parameters of examples 1 to 19 and comparative examples 1 to 4, and table 2 shows electrical property test results of the lithium ion batteries of examples 1 to 19 and comparative examples 1 to 4.

TABLE 1

TABLE 2

Comparing examples 1 to 7 with comparative example 1, it can be seen that the addition of the cyano-containing carboxylic acid ester (e.g., the compound of formula I) to the electrolyte has a better effect of improving the high-temperature performance of the lithium ion battery.

As can be seen from comparative example 4 and comparative example 1, LiPO was added to the electrolyte₂F₂Can improve the high-temperature cycle performance and reduce the impedance of the lithium ion battery because it can increase the LiF component in the organic protective film and increase the organic protective filmThe stability of the overcoat, but the high temperature storage performance is deteriorated.

As can be seen by comparing examples 8 to 19 with comparative example 1, the cyano group-containing carboxylic acid ester and LiPO₂F₂Has synergistic effect, and cyano-containing carboxylic ester and LiPO are added into the electrolyte₂F₂The high-temperature cycle performance of the lithium ion battery can be further improved, the direct-current impedance of the lithium ion battery is reduced, and the high-temperature storage performance is improved.

As can be seen by comparing examples 1 to 15 with comparative examples 2 to 3, when the sum X + Y of the weight percentage X of the cyano-containing carboxylic acid ester and the weight percentage Y of lithium difluorophosphate is greater than 5.5 wt%, the transmission of lithium ions is affected and the performance of the lithium ion battery is deteriorated due to an excessive amount of the additive added; when X/Y < 1/5 (for example, X/Y ═ 1/10), the effect of improvement is not obtained because the amount of cyano-containing carboxylic acid ester added is small.

Table 3 shows the electrolyte parameters of examples 3 and 20 to 31, and table 4 shows the electrical property test results of the lithium ion batteries of examples 3 and 20 to 31.

TABLE 3

TABLE 4

It can be seen from comparing examples 20 to 24 with example 3 that the addition of a cyclic sulfur compound to the electrolyte can improve the high-temperature cycle performance of the lithium ion battery and reduce the dc resistance of the lithium ion battery.

As is clear from comparing example 30 with example 31, when the weight percentage of the cyclic sulfur compound in the electrolyte exceeds 6 wt%, the high-temperature cycle performance improvement effect of the lithium ion battery is reduced because the high-temperature cycle characteristics are reduced due to excessive formation of the coating film on the electrode.

Table 5 shows the electrolyte parameters of examples 4, 27, and 32 to 44, and table 6 shows the electrical property test results of the lithium ion batteries of examples 4, 27, and 32 to 44.

TABLE 5

TABLE 6

It can be seen from comparing examples 32 to 35 with example 4 that the overcharge performance of the lithium ion battery can be significantly improved by adding a fluorocarboxylic acid ester to the electrolyte. The fluorine-containing fluorocarboxylic acid ester has strong oxidizing property due to the fluorine atom contained therein, and can significantly improve the oxidation resistance of the system, thereby improving the safety performance. And a cyano group-containing carboxylic acid ester and LiPO are bonded₂F₂And the good interface protection effect of the cyclic sulfur-containing compound can further improve the safety performance of the battery.

However, when the weight percentage of the fluorocarboxylic acid ester in the electrolyte is too large, the high-temperature cycle performance of the lithium ion battery is significantly deteriorated, mainly because the too high content of the fluorocarboxylic acid ester affects the dynamic performance of the lithium ion battery, thereby deteriorating the cycle performance and limiting the use thereof.

Table 7 shows the negative electrode parameters and electrical property test results of example 39, examples 45 to 49. Examples 45 to 49 differ from example 39 in the content of fluorocarboxylic acid ester.

TABLE 7

As can be seen from comparison of examples 39, 45 to 49, when the mass of the corresponding fluorocarboxylate per unit mass of the negative active material is within a certain range, the lithium ion battery has good overcharge performance; when the mass of the fluorocarboxylate corresponding to each gram of the anode active material layer exceeds 0.65g, the high-temperature cycle performance of the lithium ion battery may be deteriorated because the fluorocarboxylate content is excessively high, which affects the kinetic performance of the lithium ion battery, thereby deteriorating the cycle performance of the lithium ion battery.

Reference throughout this specification to "some embodiments," "one embodiment," "another example," "an example," "a specific example," or "some examples" means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. Thus, throughout the specification, descriptions appear, for example: "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in one example," "in a particular example," or "by example," which do not necessarily refer to the same embodiment or example 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 illustrated and described, it will be appreciated by those skilled in the art that the above embodiments are not to be construed as limiting the application and that changes, substitutions and alterations can be made to the embodiments without departing from the spirit, principles and scope of the application.

Claims

1. An electrolyte comprising lithium difluorophosphate and a cyano-containing carboxylic acid ester of formula I:

wherein R is₁₁Is substituted or unsubstituted C₁To C₆Straight or branched alkyl, substituted or unsubstituted C₂To C₇Straight or branched alkenyl, substituted or unsubstituted C₃To C₈Straight or branched alkynyl, substituted or unsubstituted C₃To C₈Cycloalkyl or substituted or unsubstituted C₆To C₁₂Aryl, wherein when substituted, the substituent is a halogen atom or cyano;

wherein R is₁₂、R₁₃Each independently selected from a halogen atom, a substituted or unsubstituted C₁To C₆Straight or branched alkyl, substituted or unsubstituted C₂To C₇Straight or branched alkenyl, substituted or unsubstituted C₃To C₈Straight or branched alkynyl, substituted or unsubstituted C₁To C₆Straight or branched alkoxy or substituted or unsubstituted C₆To C₁₂Aryl, wherein when substituted, the substituent is a halogen atom,

wherein a weight percentage X of the cyano-containing carboxylic acid ester to a weight percentage Y of the lithium difluorophosphate satisfies X + Y <5.5 wt% and X/Y >1/5, based on the weight of the electrolyte.

2. The electrolyte of claim 1, wherein the cyano-containing carboxylic acid ester comprises:

at least one of;

wherein the weight percentage of the cyano-containing carboxylic ester is 0.01 wt% to 6 wt% based on the weight of the electrolyte.

3. The electrolyte of claim 1, wherein the weight percent of the lithium difluorophosphate is 0.01 wt% to 1 wt% based on the weight of the electrolyte.

4. The electrolyte of claim 1, wherein the electrolyte further comprises a cyclic sulfur-containing compound represented by formula II:

wherein R is₂₁、R₂₂、R₂₃、R₂₄Each independently selected from a hydrogen atom, a substituted or unsubstituted C₁To C₆Straight or branched alkyl, substituted or unsubstituted C₂To C₆Straight or branched alkenyl, substituted or unsubstituted C₂To C₆Straight or branched alkynyl, substituted or unsubstituted C₁To C₆Straight or branched alkoxy, substituted or unsubstituted C₆To C₁₂Aryl, substituted or unsubstituted C₁To C₆Heterocyclic radical, sulfonyl, substituted or unsubstituted C₂To C₇Alkylcarbonyl, substituted or unsubstituted C₂To C₇Alkenylcarbonyl, substituted or unsubstituted C₃To C₇Alkynylcarbonyl or substituted or unsubstituted C₇To C₁₃An arylcarbonyl group, wherein the heterocyclic group comprises at least one of O, S, N or P, wherein when substituted, the substituent is at least one of a halogen atom or a vinyl sulfate group;

wherein n1 and n2 are each independently 0 or 1;

wherein B is carbonyl, ester, sulfonate, sulfate, substituted or unsubstituted C₁To C₆Alkylene, substituted or unsubstituted C₂To C₆Alkenylene, substituted or unsubstituted C₂To C₆Alkynylene or vinyl sulfate, wherein when substituted, the substituent isHalogen atom, C₁To C₆Alkyl ester group, C₂To C₆Alkenyl ester group, C₂To C₆Alkynyl ester group or C₇To C₁₃At least one of aryl ester groups;

wherein the weight percentage of the cyclic sulfur compound is 0.1 wt% to 6 wt% based on the weight of the electrolyte.

5. The electrolyte of claim 4, wherein the cyclic sulfur-containing compound comprises:

at least one of (1).

6. The electrolyte of claim 1, wherein the electrolyte further comprises a fluorocarboxylate ester according to formula III:

wherein R is₃₁、R₃₂Each independently selected from substituted or unsubstituted straight or branched C₁To C₆Alkyl, substituted or unsubstituted straight or branched C₂To C₆Alkenyl or substituted or unsubstituted, straight or branched C₂To C₆Alkynyl, wherein when substituted, the substituent is an F atom;

wherein the fluorocarboxylic acid ester represented by the formula III contains at least one F atom;

wherein the fluorocarboxylic acid ester is present in an amount of 0.01 to 20% by weight, based on the weight of the electrolyte.

7. The electrolyte of claim 6, wherein the fluorocarboxylic acid ester comprises:

at least one of (1).

8. An electrochemical device comprising a positive electrode, a negative electrode, a separator and the electrolyte of any one of claims 1-7.

9. The electrochemical device according to claim 8, wherein the negative electrode includes a negative electrode current collector and a negative electrode active material layer, and the content of the fluorocarboxylate is 0.045g to 0.65g per gram of the negative electrode active material layer.

10. An electronic device comprising the electrochemical device according to claim 8 or 9.