CN111342135B - Electrochemical device and electronic device comprising same - Google Patents

Electrochemical device and electronic device comprising same Download PDF

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CN111342135B
CN111342135B CN202010177667.4A CN202010177667A CN111342135B CN 111342135 B CN111342135 B CN 111342135B CN 202010177667 A CN202010177667 A CN 202010177667A CN 111342135 B CN111342135 B CN 111342135B
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electrochemical device
lithium
electrolyte
carbonate
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CN111342135A (en
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栗文强
管明明
郑建明
郑湘岭
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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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/626—Metals
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

The present application relates to an electrochemical device. The electrochemical device of the present application comprises a positive electrode, a negative electrode and an electrolytic solution, wherein the electrolytic solution contains an anion having a phosphoric anhydride functional group of a specific structure. By adding the anions into the electrolyte, the low-temperature discharge performance and the high-temperature storage performance of the electrochemical device can be improved and considered at the same time, and the cycle stability of the electrochemical device at normal temperature and high temperature is improved.

Description

Electrochemical device and electronic device comprising same
Technical Field
The present disclosure relates to the field of energy storage technologies, and more particularly, to an electrochemical device and an electronic device including the same.
Background
With the popularization and application of intelligent products, the demand of people on electronic products such as mobile phones, notebook computers, cameras and the like is increasing year by year, and electrochemical devices as power sources of the electronic products play more and more important roles in daily life. Among them, the lithium ion battery is widely used in the consumer electronics field by virtue of its advantages of large specific energy, high operating voltage, low self-discharge rate, small volume, light weight, etc.
However, with the wide application of electrochemical devices in electric vehicles, mobile electronic devices and unmanned aerial vehicles, people not only require that electrochemical devices can work normally in normal temperature environments, but also require that electrochemical devices can be used safely in severe environments. For example, how to ensure that an electrochemical device can be normally used under an extremely low temperature condition without causing instantaneous power failure of an electronic product, how to reduce the risk of swelling of the electrochemical device under a high temperature condition so as to ensure safe use of the electronic product under a high temperature environment, how to enable the electrochemical device to realize high-rate charge and discharge, and the like are urgently needed to be solved. In addition, the prior art is not able to achieve the electrochemical performance of the electrochemical device in a high temperature environment while trying to ensure the normal use of the electrochemical device in a low temperature environment. Therefore, how to make an electrochemical device have excellent electrochemical performance under both high-temperature and low-temperature environments is also a problem to be considered and solved.
Disclosure of Invention
In order to solve at least the above problems, the present application introduces anions having phosphoric anhydride functional groups into an electrolyte of an electrochemical device. First, by utilizing the electron-rich property of phosphorus-oxygen double bonds (P ═ O bonds) in the phosphoric anhydride functional groups, it is possible to promote rapid transport of lithium ions, thereby improving rate performance of the electrochemical device and its discharge performance at low temperatures. Secondly, the bridging structure of the phosphoric anhydride functional group and negative charges carried by anions are utilized to be beneficial to forming a protective film on the positive electrode in an oriented manner, so that the cycle stability and the high-temperature storage performance of the electrochemical device are improved.
According to one aspect of the present application, there is provided an electrochemical device comprising: a positive electrode including a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material; a negative electrode including a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer including a negative electrode active material; and an electrolyte comprising lithium ions and anions represented by formula I:
Figure BDA0002411353700000021
wherein n is an integer ranging from 0 to 5;
R1selected from substituted or unsubstituted C1-C12Alkyl, substituted or unsubstituted C2-C12Alkenyl, substituted or unsubstituted C6-C20Aryl, substituted or unsubstituted C1-C12Hydrocarbyloxy, wherein when substituted, the substituents are independently selected from silane groups, siloxane groups, amino groups, ether groups, ester groups, carboxyl groups, sulfonic acid groups, mercapto groups, cyano groups, halogens, or combinations thereof.
According to an embodiment of the present application, wherein the anion represented by formula I comprises:
Figure BDA0002411353700000022
Figure BDA0002411353700000031
Figure BDA0002411353700000032
at least one of;
according to the embodiment of the present application, the anion represented by the formula I is contained in an amount of 0.001 to 7% by mass based on the total weight of the electrolyte.
According to an embodiment of the present application, the electrolyte further includes one or more of a fluoro carbonate, a fluoro carboxylate, a sulfur-containing additive, a nitrile-containing additive, or a lithium salt additive.
According to an embodiment of the present application, wherein the fluoro carbonate comprises at least one of propylene 3,3, 3-trifluorocarbonate, ethylene fluoro carbonate, methyl 2,2,3, 3-tetrafluoropropyl carbonate, ethyl 2,2,3,3, 3-pentafluoropropyl carbonate, bis (2,2, 2-trifluoroethyl) carbonate, bis (2-fluoroethyl) carbonate, trifluoromethyl carbonate or ethylene bis fluoro carbonate.
According to an embodiment of the present application, the content of the fluoro carbonate is 0.01 to 20% based on the total weight of the electrolyte.
According to an embodiment of the present application, the fluorocarboxylic acid ester includes at least one of acetylhypofluorite, 2-fluoroethyl fluoroacetate, ethyl fluorohexanoate, methyl fluoroacetate, ethyl fluoroacetate, butyl fluoroacetate, 2,2, 2-trifluoroethyl trifluoroacetate, 2-fluoroethyl 5-fluorohexanoate, 2,2, 2-trifluoroethyl difluoroacetate, 2, 2-difluoroethyl trifluoroacetate, 2-fluoroethyl 4-fluorobutyrate, ethyl trifluoropropionate, ethyl 2-fluoropropionate, ethyl 2, 2-difluoroacetate, ethyl difluoropropionate, methyl difluoroacetate, or methyl 2-fluoropropionate.
According to an embodiment of the present application, the fluorocarboxylate is contained in an amount of 0.01 to 30% based on the total weight of the electrolyte.
According to an embodiment of the present application, the sulfur-containing additive includes at least one of 1, 3-butylidene sulfate, vinyl sulfate, 1, 3-propane sultone, 1, 3-propanediol cyclic sulfate, 2, 4-butane sultone, 1, 3-butane sultone, 1-methyl-1, 3-propane sultone, 2-methyl-1, 3-propane sultone, 3-methyl-1, 3-propane sultone, 1-fluoro-1, 3-propane sultone, 2-fluoro-1, 3-propane sultone, or 3-fluoro-1, 3-propane sultone.
According to an embodiment of the present application, the sulfur-containing additive is contained in an amount of 0.01 to 10% based on the total weight of the electrolyte.
According to embodiments herein, the nitrile-containing additive comprises at least one of the following compounds:
Figure BDA0002411353700000041
wherein M is selected from C, Si;
wherein R is51、R61、R62、R63Each independently selected from substituted or unsubstituted C1-C12Alkylene, substituted or unsubstituted C2-C12Alkenylene radical, R0-S-R group or R0-O-R group, wherein R0R is independently selected from substituted or unsubstituted C1-C6Alkylene, wherein when substituted, the substituents are selected from halogen;
wherein R is64Selected from H, substituted or unsubstituted C1-C12Alkylene, substituted or unsubstituted C2-C12Alkenylene radical, R0-S-R group or R0-O-R group, wherein R0R is independently selected from substituted or unsubstituted C1-C6Alkylene, wherein when substituted, the substituents are selected from halogen.
According to embodiments of the present application, wherein the nitrile-containing additive comprises at least one of adiponitrile, succinonitrile, glutaronitrile, malononitrile, 2-methylglutaronitrile, pimelonitrile, sebaconitrile, nonanedionitrile, 1, 4-dicyano-2-butene, ethylene glycol bis (propionitrile) ether, 3' -oxydiproponitrile, thiomalononitrile, hexa-2-enedinitrile, butenedinitrile, 2-pentenenitrile, ethylsuccinonitrile, hexa-3-enedinitrile, 2-methyleneglutaronitrile, 4-cyanoheptanedinitrile, 1,3, 6-hexanetricarbonitrile, 1,3, 5-hexanetricarbonitrile, 1,2, 3-propanetricitrile, or 1,2, 3-tris (2-cyanato) propane.
According to an embodiment of the present application, the nitrile containing additive is present in an amount of 0.01 to 10% based on the total weight of the electrolyte.
According to an embodiment of the present application, the lithium salt additive comprises at least one of lithium bistrifluoromethanesulfonylimide, lithium bis (fluorosulfonyl) imide, lithium bis (oxalato) borate, lithium tetrafluorophosphate oxalate, lithium difluorooxalato borate, lithium hexafluorocaesinate or lithium difluorophosphate.
According to an embodiment of the present application, the lithium salt additive is included in an amount of 0.01 to 5% based on the total weight of the electrolyte.
According to an embodiment of the present application, wherein the anode active material layer contains a metal element including at least one of Co, Mn, Ni, Al, or Cu.
According to an embodiment of the present application, the content of the metal element is 200ppm or less based on the total weight of the anode active material layer.
Detailed Description
Embodiments of the present application will be described in detail below. The embodiments of the present application should not be construed as limiting the present application.
As used herein, the terms "comprises," "comprising," and "includes" are used in their open, non-limiting sense.
The term "about" is 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 terms can refer to a range of variation of less than or equal to ± 10 wt% of the stated numerical value, such as less than or equal to ± 5 wt%, less than or equal to ± 4 wt%, less than or equal to ± 3 wt%, less than or equal to ± 2 wt%, less than or equal to ± 1 wt%, less than or equal to ± 0.5 wt%, less than or equal to ± 0.1 wt%, or less than or equal to ± 0.05 wt%. Additionally, amounts, ratios, and other numerical values are sometimes presented herein in a range format. It is to be understood that such range format is used for convenience and brevity, and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.
The term "alkyl" encompasses both straight-chain and branched-chain alkyl groups. For example, the alkyl group may be C1-C50Alkyl radical, C1-C40Alkyl radical, C1-C30Alkyl radical, C1-C20Alkyl radical, C1-C12Alkyl radical, C1-C10Alkyl radical, C1-C6Alkyl radical, C2-C6Alkyl radical, C2-C5An alkyl group. In some embodiments, alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, and the like. In addition, the alkyl group may be optionally substituted.
The term "alkenyl" encompasses straight-chain and branched alkenyl groups. For example, the alkenyl group may be C2-C50Alkenyl radical, C2-C40Alkenyl radical, C2-C30Alkenyl radical, C2-C20Alkenyl radical, C2-C12Alkenyl radical, C2-C10Alkenyl radical, C2-C6An alkenyl group. In addition, the alkenyl group may be optionally substituted.
The term "aryl" encompasses monocyclic and polycyclic ring systems. Polycyclic rings can 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., the other rings can be cycloalkyls, cycloalkenyls, aryls, heterocyclics, and/or heteroaryls. For example, the aryl group may be C6-C50Aryl radical, C6-C40Aryl radical, C6-C30Aryl radical, C6-C20Aryl or C6-C10And (4) an aryl group.In addition, the aryl group may be optionally substituted.
The term "hydrocarbyloxy" is an organic group having-O-R, where R is a straight or branched chain hydrocarbyl group. For example, R may be C1-C50Hydrocarbyl radical, C1-C40Hydrocarbyl radical, C1-C30Hydrocarbyl radical, C1-C20Hydrocarbyl radical, C1-C12Hydrocarbyl radical, C1-C10Hydrocarbyl radical, C1-C6Hydrocarbyl radical, C2-C6Hydrocarbyl radical, C2-C5A hydrocarbyl group. For example, the hydrocarbyl group may include an alkyl group, an alkenyl group, an alkynyl group, or an aryl group. Further, the hydrocarbyloxy group may be optionally substituted.
The term "alkylene" encompasses straight and branched chain alkylene groups. For example, the alkylene group may be C1-C50Alkylene radical, C1-C40Alkylene radical, C1-C30Alkylene radical, C1-C20Alkylene radical, C1-C10Alkylene radical, C1-C6Alkylene radical, C2-C6Alkylene radical, C2-C5An alkylene group. In addition, the alkylene group may be optionally substituted.
The term "alkenylene" encompasses both straight-chain and branched alkenylene groups. For example, alkenylene may be C2-C50Alkenylene radical, C2-C40Alkenylene radical, C2-C30Alkenylene radical, C2-C20Alkenylene radical, C2-C10Alkenylene radical, C1-C6Alkenylene radical, C2-C6An alkenylene group. In addition, alkenylene may be optionally substituted.
When the above groups are substituted, the substituents may be independently selected from the group consisting of silane groups, siloxane groups, amino groups, ether groups, ester groups, carboxyl groups, sulfonic acid groups, mercapto groups, cyano groups, halogens, or combinations thereof.
The present application relates to an electrochemical device comprising: a positive electrode; a negative electrode; and an electrolyte.
In some embodiments, the positive electrode of the present application may include a positive electrode current collector and a positive electrode active material layer. In some embodiments, the positive active material layer is disposed on a positive current collector. In some embodiments, the positive active material layer comprises a positive active material.
The positive active material of the present application is capable of reversibly intercalating and deintercalating lithium ions. The specific kind of the positive electrode active material is not particularly limited and may be selected as desired. The positive active material may include lithium and at least one active metal, including, but not limited to, for example, a composite oxide including metallic lithium and at least one active metal, wherein the active metal element includes or is selected from at least one of the following elements: cobalt (Co), nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), lanthanum (La), and zirconium (Zr).
In some embodiments, the positive active material may include, but is not limited to, at least one of lithium cobaltate, lithium iron phosphate, lithium iron manganese phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadyl phosphate, sodium vanadyl phosphate, lithium vanadate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium rich manganese based materials, lithium nickel cobalt aluminate, and lithium titanate.
The positive electrode current collector may be a positive electrode current collector commonly used in the art, and in some embodiments, includes, but is not limited to, an aluminum foil or a nickel foil.
In some embodiments, the positive electrode active material layer may further include a binder and/or a conductive agent.
The binder can improve the bonding between the positive active material particles and the bonding between the positive active material and the positive current collector. In some embodiments, the binder may include, but is not limited to, at least one of 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.
Conductive agents may be used to enhance the conductivity of the electrode. Any conductive material may be employed as the conductive agent so long as the conductive material does not cause unwanted chemical changes. In some embodiments, the conductive material may include, but is not limited to, at least one of a carbon-based material (e.g., natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, etc.), a metal-based material (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), a conductive polymer (e.g., a polyphenylene derivative), and mixtures thereof.
The negative electrode of the electrochemical device of the present application may include a negative electrode current collector and a negative electrode active material layer. In some embodiments, the negative active material layer is disposed on a negative current collector. In some embodiments, the negative active material layer comprises a negative active material.
The negative active material of the present application is capable of reversibly intercalating and deintercalating lithium ions. The specific kind of the negative electrode active material is not particularly limited and may be selected as desired. In some embodiments, the negative active material may include or be selected from one or more of the following materials: carbonaceous material, siliceous material, alloy material, lithium metal-containing composite oxide material. In some embodiments, the carbonaceous material may include, but is not limited to, crystalline carbon, amorphous carbon, and mixtures thereof. The crystalline carbon may be natural graphite or artificial graphite in an amorphous form or in a form of a flake, a platelet, a sphere or a fiber. The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, or the like.
In some embodiments, the negative active material may include, but is not limited to, natural graphite, artificial graphite, mesophase micro carbon spheres (abbreviated as MCMB), hard carbon, soft carbon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO2Spinel-structured lithiated TiO2-Li4Ti5O12And Li-Al alloy.
The negative electrode current collector may be a negative electrode current collector commonly used in the art. In some embodiments, the negative current collector includes, but is not limited to, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrates coated with conductive metals, and combinations thereof.
In some embodiments, the negative active material layer may further include a binder and/or a conductive agent. The binder and the conductive agent can be the materials disclosed in the foregoing positive electrode, and will not be described in detail herein.
The electrolyte can be divided into an aqueous electrolyte and a non-aqueous electrolyte, wherein compared with the aqueous electrolyte, an electrochemical device adopting the non-aqueous electrolyte can work under a wider voltage window, so that higher energy density is achieved.
The nonaqueous electrolyte may include an organic solvent. According to the present application, the organic solvent may be any organic solvent known in the art that can be used as a solvent for an electrolyte. In some embodiments, the organic solvent of the present application comprises or is selected from: at least one of Ethylene Carbonate (EC), Propylene Carbonate (PC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC), and dimethyl carbonate (DMC).
Through extensive research, the electrochemical device has excellent cycle stability and excellent low-temperature discharge performance and high-temperature storage performance when lithium ions and anions represented by the following formula I are contained in the electrolyte:
Figure BDA0002411353700000081
wherein n is an integer ranging from 0 to 5;
R1selected from the group consisting of substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted aryl groups, substituted or unsubstituted alkoxy groups, wherein when substituted, the substituents are independently selected from the group consisting of silane groups, siloxane groups, amino groups, ether groups, ester groups, carboxyl groups, sulfonic acid groups, mercapto groups, cyano groups, halogens, or combinations thereof.
In some embodiments, R1Selected from substituted or unsubstituted C1-C12Alkyl, substituted or unsubstituted C2-C12Alkenyl, substituted or notSubstituted C6-C20Aryl or substituted or unsubstituted C1-C12A hydrocarbyloxy group.
In some embodiments, R1Selected from substituted or unsubstituted C1-C10Alkyl, substituted or unsubstituted C2-C10Alkenyl, substituted or unsubstituted C6-C10Aryl or substituted or unsubstituted C1-C10A hydrocarbyloxy group.
Although the detailed mechanism of action for obtaining such effects is not clear, the following is conceivable: the anions represented by the formula I can promote the rapid transmission of lithium ions at the interface of the anode and the electrolyte, so that the discharge performance of the electrochemical device at low temperature is improved; and the method is favorable for directionally forming a stable passive film on the surface of the anode, thereby improving the cycling stability of the electrochemical device in the charging and discharging processes and reducing the gas generation expansion degree under the high-temperature storage condition so as to improve the high-temperature storage performance of the electrochemical device.
In some embodiments, the anion represented by formula I described herein includes or is selected from one or more of the following anions, but is not limited thereto:
Figure BDA0002411353700000091
in some embodiments, the mass percentage content of the anion represented by formula I is in a range of: 0.001 wt% to 7 wt%, 0.01 wt% to 5 wt%, 0.1 wt% to 3 wt%, or 0.1 wt% to 2 wt%. In some embodiments, the anion represented by formula I is present in any one of the above ranges by mass based on the total weight of the electrolyte. For example, the anion represented by formula I is present in an amount of about 0.001 wt%, about 0.01 wt%, about 0.1 wt%, about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, about 5 wt%, about 6 wt%, or about 7 wt% by mass.
In some embodiments, the anion represented by formula I herein forms a lithium salt with lithium ions, and is added to the electrolyte as a lithium salt.
In some embodiments, the anion represented by formula I herein can be a decomposition product of 1-propyl phosphoric anhydride, 1-acetonitrile phosphoric anhydride, 1-ethyl phosphoric anhydride.
In some embodiments, the electrolytes of the present application optionally further comprise one or more of a fluoro-carbonate, a fluoro-carboxylate, a sulfur-containing additive, a nitrile-containing additive, and a lithium salt additive to facilitate better functioning of the electrolyte in electrochemical devices in combination with the anions of formula I. The above components, and the contents and effects thereof will be described in detail as follows.
In some embodiments, the electrolytes of the present application further comprise a fluorinated carbonate. The fluoro-carbonate is combined with the anion of the formula I in the electrolyte, and the rapid transmission of lithium ions at the interface of the positive electrode and the negative electrode and the stability of the positive electrode and the negative electrode in the charging and discharging processes can be simultaneously considered, so that the cycle performance and the low-temperature discharge performance of the electrochemical device are improved.
In some embodiments, the fluoro carbonate includes or is selected from at least one of propylene 3,3, 3-trifluorocarbonate, ethylene fluoro carbonate, methyl 2,2,3, 3-tetrafluoropropyl carbonate, ethyl 2,2,3,3, 3-pentafluoropropyl carbonate, bis (2,2, 2-trifluoroethyl) carbonate, bis (2-fluoroethyl) carbonate, trifluoromethyl carbonate, or ethylene bis-fluorocarbonate.
In some embodiments, the fluoro-carbonate is present in an amount of 0.01 to 40 wt%, 0.01 to 30 wt%, 0.01 to 20 wt%, 0.01 to 10 wt%, 0.01 to 5 wt%, 0.1 to 40 wt%, 0.1 to 30 wt%, 0.1 to 20 wt%, 0.1 to 10 wt%, 0.1 to 5 wt%, 1 to 40 wt%, 1 to 30 wt%, 1 to 20 wt%, 1 to 10 wt%, or 1 to 5 wt%, based on the total weight of the electrolyte.
In some embodiments, the electrolytes of the present application further comprise a fluorocarboxylic acid ester. Interaction of the fluorocarboxylic acid ester with the anion of formula I can further improve high temperature storage properties. Although the detailed mechanism of action for obtaining such effects is not clear, the following is conceivable: the mutual action of the fluorocarboxylate and the anion shown in the formula I improves the oxidation resistance of the electrolyte, can effectively reduce the oxidation degree of the anode active substance to the electrolyte, and can form a composite SEI film on the surface of the anode to enhance the protection of the anode.
In some embodiments, the fluorocarboxylic acid ester comprises or is selected from at least one of acetylhypofluorite, 2-fluoroethyl fluoroacetate, ethyl fluorohexanoate, methyl fluoroacetate, ethyl fluoroacetate, butyl fluoroacetate, 2,2, 2-trifluoroethyl trifluoroacetate, 2-fluoroethyl 5-fluorohexanoate, 2,2, 2-trifluoroethyl difluoroacetate, 2, 2-difluoroethyl trifluoroacetate, 2-fluoroethyl 4-fluorobutyrate, ethyl trifluoropropionate, ethyl 2-fluoropropionate, ethyl 2, 2-difluoroacetate, ethyl difluoropropionate, methyl difluoroacetate, or methyl 2-fluoropropionate.
In some embodiments, the fluorocarboxylic acid ester is present in an amount of 0.01 to 50 wt%, 0.01 to 40 wt%, 0.01 to 30 wt%, 0.01 to 20 wt%, 0.01 to 10 wt%, 0.01 to 5 wt%, 0.1 to 50 wt%, 0.1 to 40 wt%, 0.1 to 30 wt%, 0.1 to 20 wt%, 0.1 to 10 wt%, 0.1 to 5 wt%, 1 to 50 wt%, 1 to 40 wt%, 1 to 30 wt%, 1 to 20 wt%, 1 to 10 wt%, or 1 to 5 wt%, based on the total weight of the electrolyte.
In some embodiments, the electrolytes of the present application further comprise a sulfur-containing additive. The sulfur-containing additive can also form a stable SEI film on the surface of the positive electrode, so that the positive electrode is protected. In combination with the anion shown in formula I, the sulfur-containing additive can form a composite protective film on the surface of the positive electrode, so that the protection of the positive electrode is further enhanced, and the stability of the electrochemical device is improved.
In some embodiments, the sulfur-containing additive comprises at least one of 1, 3-butylidene sulfate, vinyl sulfate, 1, 3-propane sultone, 1, 3-propanediol episulfate, 2, 4-butane sultone, 1, 3-butane sultone, 1-methyl-1, 3-propane sultone, 2-methyl-1, 3-propane sultone, 3-methyl-1, 3-propane sultone, 1-fluoro-1, 3-propane sultone, 2-fluoro-1, 3-propane sultone, or 3-fluoro-1, 3-propane sultone.
In some embodiments, the sulfur-containing additive is present in an amount of 0.01 to 20 wt%, 0.01 to 10 wt%, 0.01 to 5 wt%, 0.1 to 20 wt%, 0.1 to 10 wt%, 0.1 to 5 wt%, 1 to 20 wt%, 1 to 10 wt%, or 1 to 5 wt%, based on the total weight of the electrolyte.
In some embodiments, the electrolytes of the present application further comprise a nitrile-containing additive. Wherein the nitrile containing additive comprises a cyano (-CN) functional group. The nitrile-containing additive and the anion shown in the formula I act together to form a nitrile protective film with excellent performance on the surface of the positive electrode, well stabilize active metal in the positive electrode active material, inhibit the dissolution of the active metal and improve the cycle performance of an electrochemical device.
In some embodiments, the nitrile containing additive comprises at least one of the following compounds:
Figure BDA0002411353700000111
wherein the element M can be one selected from C, Si;
wherein R is51、R61、R62、R63Each independently selected from substituted or unsubstituted C1-C12Alkylene, substituted or unsubstituted C2-C12Alkenylene radical, R0-S-R group or R0-O-R group, wherein R0And each R is independently selected from substituted or unsubstituted C1-C6Alkylene, wherein when substituted, the substituents are selected from halogen;
wherein R is64Selected from H, substituted or unsubstituted C1-C12Alkylene, substituted or unsubstituted C2-C12Alkenylene radical, R0-S-R group or R0-O-R group, wherein R0And each R is independently selected from substituted or unsubstituted C1-C6Alkylene, wherein when substituted, the substituents are selected from halogen. In some embodiments, the nitrile-containing additive comprises adiponitrile, succinonitrile, glutaronitrile, malononitrile, 2-methylglutaronitrile, pimelonitrile, sebaconitrile, nonadinitrile1, 4-dicyano-2-butene, ethylene glycol bis (propionitrile) ether, 3' -oxydiproponitrile, thiomalononitrile, hexa-2-enedinitrile, butenedinitrile, 2-pentenenitriles, ethylsuccinonitrile, hexa-3-enedinitrile, 2-methyleneglutaronitrile, 4-cyanoheptanedinitrile, 1,3, 6-hexanetricarbonitrile, 1,3, 5-hexanetricarbonitrile, 1,2, 3-propanetricitrile, or 1,2, 3-tris (2-cyanato) propane.
The protective effect of the nitrile-containing additives is somewhat dependent on their amount. In some embodiments, the nitrile containing additive is present in an amount of 0.01 to 20 wt%, 0.01 to 10 wt%, 0.1 to 20 wt%, 0.1 to 10 wt%, 1 to 20 wt%, or 1 to 10 wt%, based on the total weight of the electrolyte.
In some embodiments, since LiF can enhance the stability of the SEI film, the electrolyte of the present application may further include a lithium salt additive that can increase the LiF component in the SEI film, thereby achieving the effect of improving the cycle stability of the electrochemical device.
In some embodiments, the lithium salt additive comprises or is selected from lithium bistrifluoromethanesulfonylimide LiN (CF)3SO2)2(abbreviated as LiTFSI), lithium bis (fluorosulfonyl) imide Li (N (SO)2F)2) (abbreviated as LiFSI) and lithium LiB (C) bis (oxalato-borate2O4)2(abbreviated as LiBOB) and lithium tetrafluorophosphate oxalate (LiPF)4C2O2) Lithium difluorooxalato borate LiBF2(C2O4) (abbreviated as LiDFOB) and lithium hexafluorocaesium acid (LiCSF)6) Or lithium difluorophosphate (LiPO)2F2) At least one of (1).
In some embodiments, the lithium salt additive is present in an amount of 0.01 to 20 wt%, 0.01 to 10 wt%, 0.01 to 5 wt%, 0.01 to 3 wt%, 0.1 to 20 wt%, 0.1 to 10 wt%, 0.1 to 5 wt%, 0.1 to 3 wt%, 1 to 20 wt%, 1 to 10 wt%, 1 to 5 wt%, or 1 to 3 wt%, based on the total weight of the electrolyte.
In some embodiments, a surface of the anode active material layer of the electrochemical device includes a trace amount of a metal element. In some embodiments, the metal element is distributed on the surface of the negative electrode active material layer, for example, the metal element is distributed to a depth of not more than 5mm with respect to the surface of the negative electrode (the side away from the negative electrode current collector). The metal on the surface of the negative electrode active material layer is partially derived from the metal element in the positive electrode active material and partially derived from the electrolyte system. For example, after the electrolyte is injected, the metal element distributed on the surface of the anode active material layer can be controlled by controlling the high-temperature baking time of the electrolyte and the water content in the dry battery. In addition, during charge and discharge of the electrochemical device, the electrolyte chemically reacts with the positive electrode active material to some extent, thereby causing the metal in the positive electrode active material to be dissolved in the electrolyte in the form of ions. During the charging process, the dissolved metal ions are reduced and deposited on the surface of the negative active material layer of the electrochemical device.
Since a part of the metal elements of the surface of the anode active material layer is derived from the cathode active material, in some embodiments of the present application, the metal elements may include or be selected from at least one of cobalt (Co), nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), lanthanum (La), and zirconium (Zr).
In the present application, since the anion represented by formula I contained in the electrolyte solution contributes to the formation of a strong and stable SEI film on the surface of the positive electrode to protect the positive electrode active material, the metal elements dissolved from the positive electrode active material and distributed to the surface of the negative electrode are generally in a trace amount. The content of metal ions added to the electrolyte is also very small. In some embodiments, the content of the metal element ranges below about 200ppm based on the total weight of the anode active material layer.
In fact, the trace amount of metal elements distributed on the surface of the negative electrode enhances the conductivity of the surface of the negative electrode to some extent, which facilitates the rapid transmission of electrons and lithium ions, thereby improving the rate characteristics and low-temperature discharge performance of the electrochemical device.
In some embodiments, the electrochemical device of the present application further comprises a separator disposed between the positive electrode and the negative electrode to prevent short circuit. The material and shape of the separation film used in the electrochemical device are not particularly limited, and may be any of those 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.
In some embodiments, the release film 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. The material of the substrate layer may include or be selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, a polyethylene porous film, a polypropylene porous film, a polyethylene nonwoven fabric, a polypropylene-polyethylene-polypropylene porous composite film, or the like can be used.
The surface treatment layer may be, but is not limited to, a polymer layer, an inorganic layer, or a mixed layer formed of a polymer and an inorganic substance.
The inorganic layer may include inorganic particles and a binder, among others. The inorganic particles may comprise or be selected from one or a combination of more of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminium hydroxide, magnesium hydroxide, calcium hydroxide and barium sulphate. The binder may comprise or be selected from one or a combination of polyvinylidene fluoride, copolymers of vinylidene fluoride-hexafluoropropylene, polyamides, polyacrylonitriles, polyacrylates, polyacrylic acids, polyacrylates, polyvinylpyrollidones, polyvinyl ethers, polymethyl methacrylates, polytetrafluoroethylene, and polyhexafluoropropylene.
Wherein the polymer layer may comprise a polymer. The material of the polymer may include or be selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, poly (vinylidene fluoride-hexafluoropropylene).
Those skilled in the art will appreciate that the electrochemical devices of the present application may be lithium ion batteries, but may also be any other suitable electrochemical devices. The electrochemical device in the embodiments of the present application includes any device in which an electrochemical reaction occurs, and specific examples thereof include all kinds of primary batteries, secondary batteries, solar cells, or capacitors, without departing from the disclosure of the present application. 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.
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. According to some embodiments of the present application, the electrochemical device of the present application may be used in an electronic device, including, but not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a cellular phone, a portable facsimile machine, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power source, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large-sized household battery, a lithium ion capacitor, and the like.
The technical solution of the present invention will be further described with reference to the following comparative examples and specific examples, but is not limited thereto. It will be understood by those skilled in the art that the preparation methods described in the present application are only exemplary embodiments, and that modifications or substitutions to the technical solution of the present invention can be made without departing from the scope of the technical solution of the present invention.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
The following describes a method for preparing a lithium ion battery and a method for testing performance in examples and comparative examples of the present application.
Preparation of lithium ion battery
(1) Preparing an electrolyte: at water content<In a 10ppm argon atmosphere glove box, Ethylene Carbonate (EC), diethyl carbonate (DEC) and Propylene Carbonate (PC) are uniformly mixed according to the mass ratio of 3:4:3, and then fully dried lithium salt LiPF6Dissolved in the above non-aqueous solvent, wherein LiPF6In an amount of 1mol/L to obtain a base electrolyte. Finally, additives of a certain mass were added to the base electrolyte as shown in tables 1 to 8 below to prepare the electrolyte in the examples.
(2) Preparation of the positive electrode: the positive electrode active material lithium cobaltate (LiCoO)2) The conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in a proper amount of N-methyl pyrrolidone (NMP) solvent according to the weight ratio of 96:2:2 to form uniform anode slurry; and then coating the positive electrode slurry on a positive electrode current collector aluminum foil, drying and cold pressing to obtain a positive electrode active material layer, and then cutting and welding tabs to obtain the positive electrode.
(3) Preparation of a negative electrode: fully stirring and mixing a negative active material graphite, a binder Styrene Butadiene Rubber (SBR) and a thickener sodium carboxymethyl cellulose (CMC) in a proper amount of deionized water according to a weight ratio of 97:2:1 to form uniform negative slurry; and then coating the negative electrode slurry on a copper foil of a negative electrode current collector, drying and cold pressing to obtain a negative electrode active material layer, and then cutting and welding a tab to obtain a negative electrode.
(4) And (3) isolation film: polyethylene (PE) porous polymer films were used as separators.
(5) Preparing a lithium ion battery: and sequentially stacking the anode, the isolating membrane and the cathode to enable the isolating membrane to be positioned between the anode and the cathode to play an isolating role, then winding, placing in an outer packaging foil for drying, injecting the prepared electrolyte, and performing the procedures of vacuum packaging, standing, formation, shaping and the like to finish the preparation of the lithium ion battery.
Test method of (II) lithium ion battery
(1) Low temperature discharge test
The lithium ion battery was discharged to 3.0V at a current of 0.5C at a temperature of 25 ℃, left to stand for 5 minutes, then charged to 4.45V at a current of 0.5C, and further charged to 0.05C at a constant voltage of 4.45V. The discharge capacity was recorded as C1, also at a temperature of 25 ℃ and a current of 0.2C to 3.0V.
The lithium ion battery was charged to 4.45V at a temperature of 25 ℃ with a current of 0.5C, and then charged to 0.05C at a constant voltage of 4.45V. And then, placing the lithium ion battery at the temperature of-20 ℃ and standing for 30 minutes to keep the temperature of the lithium ion battery consistent with the external temperature. The discharge was recorded as C2 at-20 ℃ with a current of 0.2C to 3.0V.
The low-temperature discharge performance of the lithium ion battery is measured by calculating the discharge percentage of the lithium ion battery at the temperature of-20 ℃ through the following formula: (C2/C1). times.100%.
(2) High temperature storage expansion test
The lithium ion battery was discharged to 3.0V at 25 ℃ with a current of 0.5C, and left to stand for 5 minutes. And then charging to 4.45V at the current of 0.5C, then charging to 0.05C at a constant voltage of 4.45V, and testing the thickness of the lithium ion battery at the full charge by using a PPG soft package battery thickness gauge, wherein the thickness is marked as a. The lithium ion battery was placed in an oven at 80 ℃ for 8 hours and tested for thickness after 8 hours, denoted b.
The thickness expansion rate of the lithium ion battery at 80 ℃ is calculated by the following formula to measure the high-temperature storage performance of the lithium ion battery: (b-a)/a X100%.
(3) Cycle test at 25 deg.C
The lithium ion battery was discharged to 3.0V at 25 ℃ with a current of 0.5C, and left to stand for 5 minutes. Then charging to 4.45V by 0.5C current, and then charging to 0.05C by constant voltage under the voltage of 4.45V; after the charging is completed, the battery is discharged to 3.0V at a current of 0.5C, which is a charge-discharge cycle (i.e., one cycle).
And cycling at 25 ℃ for 800 circles according to the charge-discharge flow, wherein the discharge capacity of the first circle is marked as C1, and the discharge capacity of the 800 th circle is marked as C800. The cycle performance of the lithium ion battery is measured by calculating the cycle capacity retention rate of the lithium ion battery at 25 ℃ through the following formula: (C800/C1). times.100%.
(4) Cycling test at 45 deg.C
The lithium ion battery was discharged to 3.0V at 45 ℃ with a current of 0.5C, and left to stand for 5 minutes. Then charging to 4.45V by 0.5C current, and then charging to 0.05C by constant voltage under the voltage of 4.45V; after the charging is completed, the battery is discharged to 3.0V at a current of 0.5C, which is a charge-discharge cycle (i.e., one cycle).
And cycling the mixture at 45 ℃ for 500 circles according to the charge-discharge flow, wherein the discharge capacity of the first circle is marked as C1, and the discharge capacity of the 500 th circle is marked as C500. The cycle performance of the lithium ion battery at high temperature is measured by calculating the cycle capacity retention rate of the lithium ion battery at 45 ℃ through the following formula: (C500/C1). times.100%.
(5) Elemental metal testing
The lithium ion battery is discharged to 3.0V at a current of 0.5C, left for 5 minutes, and then discharged to 2.8V at a current of 0.05C. And disassembling the lithium ion battery after discharging in a glove box, rinsing the surface of the negative electrode for 2-3 times by using a small amount of dimethyl carbonate (DMC) solvent, removing the electrolyte remained on the surface of the negative electrode, airing the pole piece of the negative electrode, and performing an Inductively Coupled Plasma (ICP) test on the middle area of the negative electrode to measure the content of the metal element in the negative electrode.
Examples 1 to 19 and comparative example 1
The electrolytes and lithium ion batteries of examples 1 to 19 and comparative example 1 were prepared according to the above preparation method, wherein comparative example 1 used a base electrolyte, and examples 1 to 19 added components and contents shown in table 1, respectively, in the base electrolyte, wherein the contents are mass percentages of the components based on the total weight of the electrolyte, wherein the substances of formulae I-2, I-3, I-4, I-7 were added in the form of lithium salts. In addition, table 1 also shows the electrochemical test results of the lithium ion batteries in examples 1 to 19 and comparative example 1.
TABLE 1
Figure BDA0002411353700000161
Figure BDA0002411353700000171
Referring to the electrochemical test results in table 1, it can be seen that the electrolytes of examples 1 to 19 of the present application have significantly improved discharge performance at low temperature and storage performance at high temperature of the resulting electrochemical device due to the presence of a certain amount of the anion of formula I described in the present application, as compared to comparative example 1. That is, by introducing the anion of formula I into the electrolyte, the resulting electrochemical device has excellent electrochemical performance both in a low temperature environment and in a high temperature condition.
Regarding the improvement of the low-temperature discharge performance, this is because the P ═ O bond contained in the anion represented by formula I has an electron-rich property, and the transfer and transport of lithium ions at the cathode interface can be accelerated to some extent even at a low temperature of-20 ℃.
Regarding the improvement of high-temperature storage performance, the anion represented by formula I helps to directionally form a strong and stable SEI film on the surface of the positive electrode, thereby being capable of well protecting the positive electrode active material and the positive electrode, so that the electrochemical device does not suffer from severe gassing expansion even when stored at a high temperature of 80 ℃ for a long time.
Example 5 and examples 20 to 26
Examples 20 to 26 are modifications made on the basis of example 5. Specifically, in examples 20 to 26, a fluoro carbonate was further added to the electrolyte described in example 5, wherein the specific components and contents added and the performance test results of the obtained lithium ion battery are shown in table 2 below.
TABLE 2
Figure BDA0002411353700000181
Referring to the electrochemical test results in table 2, it can be seen that the electrolytes of examples 20 to 26 of the present application, compared to example 5, have improved discharge performance at low temperature and cycle stability at normal temperature to some extent due to the presence of a certain amount of fluorinated carbonate. The anion represented by the formula I and the fluoro carbonate act together to enable the electrolyte to have a higher reduction potential, an SEI film can be formed on the surface of the negative electrode in advance, and the protection is provided for the active material of the negative electrode, so that the cycle performance of an electrochemical device can be improved. In addition, the formation of the SEI film helps to reduce the generation of side reactions at the negative electrode interface, thereby suppressing an increase in resistance caused by accumulation of by-products generated by the side reactions on the electrode surface, facilitating rapid transport of lithium ions at the negative electrode interface, and thus enabling improvement in discharge performance of the electrochemical device at low temperatures.
Example 5 and examples 27 to 33
Examples 27 to 33 are modifications based on example 5. Specifically, in examples 27 to 33, fluorocarboxylic acid esters were further added to the electrolyte described in example 5, wherein the specific components and contents added thereto, and the results of performance tests of the resulting lithium ion battery were shown in table 3 below.
TABLE 3
Figure BDA0002411353700000182
Figure BDA0002411353700000191
Referring to the electrochemical test results in table 3, it can be seen that the electrolytes of examples 27 to 33 of the present application undergo a further decrease in the degree of expansion, which corresponds to the expansion experienced by the resulting electrochemical device stored at a high temperature of 80 ℃ for 8 hours, due to the presence of a certain amount of fluorocarboxylate, as compared to example 5. The anion represented by the formula I and the fluorocarboxylic ester act together to improve the oxidation resistance of the electrolyte, so that the electrolyte can effectively resist oxidation from a positive electrode active material and reduce the occurrence of a gas generation phenomenon; meanwhile, a composite SEI film can be formed on the surface of the anode, so that the protection of the anode is further enhanced, and the gas production expansion phenomenon is further inhibited.
Example 5 and examples 34 to 41
Examples 34 to 41 are modifications based on example 5. Specifically, in examples 34 to 41, sulfur-containing additives were further added to the electrolyte described in example 5, wherein the specific components and contents thereof and the performance test results of the obtained lithium ion battery are shown in table 4 below.
Referring to the electrochemical test results in table 4, it can be seen that the electrolytes of examples 34 to 41 of the present application undergo a further reduction in the degree of expansion, as compared to example 5, due to the presence of a certain amount of sulfur-containing additive, which corresponds to the resulting electrochemical device undergoing 8h of storage at a high temperature of 80 ℃. The sulfur-containing additive can also form a stable SEI film on the surface of the positive electrode, and the sulfur-containing additive is matched with anions shown in formula I of the application to form a composite protective film on the surface of the positive electrode, so that the protection of the positive electrode is further enhanced, and the gas generation expansion phenomenon is further inhibited.
TABLE 4
Figure BDA0002411353700000192
Example 5 and examples 42 to 63
Examples 42 to 63 are modifications made on the basis of example 5. Specifically, in examples 42 to 63, nitrile-containing additives were further added to the electrolyte described in example 5, wherein the specific components and contents thereof and the performance test results of the obtained lithium ion battery are shown in table 5 below.
TABLE 5
Figure BDA0002411353700000201
Referring to the electrochemical test results in table 5, it can be seen that the electrolytes of examples 42 to 63 of the present application have a further improved cycling performance at a higher temperature of 45 ℃ due to the presence of a certain amount of the nitrile-containing additive, compared to example 5. The nitrile-containing additive can form a nitrile protective film with excellent performance on the surface of the positive electrode, and the stability of the positive electrode material in the charging and discharging process is improved. Meanwhile, the nitrile-containing additive can well stabilize the active metal in the positive active material, inhibit the dissolution of the active metal and improve the cycle performance of the electrochemical device.
Example 5 and examples 64 to 73
Examples 64 to 73 are modifications based on example 5. Specifically, in examples 64 to 73, lithium salt additives were further added to the electrolyte described in example 5, wherein the specific components and contents added and the performance test results of the obtained lithium ion battery are shown in table 6 below.
TABLE 6
Figure BDA0002411353700000211
Referring to the electrochemical test results in table 6, it can be seen that the electrochemical devices of examples 64 to 73 of the present application have somewhat deteriorated discharge performance at low temperature compared to example 5, but their cycle stability at higher temperature is further improved. This is because the added lithium salt additive can increase the LiF component in the SEI film, thereby enhancing the stability of the SEI film and achieving the effect of improving the cycle stability of the electrochemical device.
Example 5 and examples 74 to 78
Examples 74 to 78 are modifications made on the basis of example 5. Specifically, the water content of the cell before electrolyte injection was controlled by the high-temperature baking time to 80ppm, 100ppm, 140ppm, 200ppm, 240ppm and 270ppm, respectively, to obtain example 5 and examples 74 to 78 of Table 7, respectively. In comparison with example 5, the surface of the negative electrodes of examples 74 to 78 had a certain content of metallic cobalt element at a depth of not more than 10 μm, wherein the specific content and the results of the performance test of the resulting lithium ion batteries are shown in table 7 below.
TABLE 7
Figure BDA0002411353700000221
Referring to the electrochemical test results in table 7, it can be seen that the surface distribution of the negative electrodes in examples 74 to 78 of the present application has a greater content of cobalt element than that in example 5, which corresponds to a further improvement in the discharge performance of the resulting electrochemical device at low temperature. This is because the metal elements distributed on the surface of the negative electrode enhance the conductivity of the surface of the negative electrode to some extent, which facilitates the rapid transport of electrons and lithium ions, thereby improving the low-temperature discharge performance of the electrochemical device.
Example 21 and examples 79 to 84
Examples 79-84 were prepared by adding sulfur-containing additives, fluorocarboxylate, nitrile additives, or combinations thereof, respectively, to example 21, wherein the specific components and amounts added, and the results of performance tests of the resulting lithium ion batteries, are shown in tables 8-1 and 8-2 below.
TABLE 8-1
Figure BDA0002411353700000222
TABLE 8-2
Figure BDA0002411353700000223
Figure BDA0002411353700000231
Referring to the electrochemical test results in tables 8-1 and 8-2, it can be seen that an electrochemical device having excellent low-temperature discharge performance and high-temperature storage performance, which can exhibit excellent cycle performance at both normal and higher temperatures, can be obtained using a combination of various additives of the present application.
Reference throughout this specification to "an embodiment," "some embodiments," "one embodiment," "another example," "an example," "a specific example," or "some examples" means that at least one embodiment or example in this application includes a particular feature, structure, material, or characteristic described in the embodiment or example. 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 (11)

1. An electrochemical device, comprising:
a positive electrode including a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material;
a negative electrode including a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer including a negative electrode active material; and
an electrolyte comprising lithium ions, an anion represented by formula I, a fluoro carbonate, and a nitrile-containing additive, wherein the fluoro carbonate comprises fluoro ethylene carbonate, and wherein the nitrile-containing additive comprises 1,3, 6-hexanetricarbonitrile:
Figure FDA0003326410340000011
wherein the content of the first and second substances,
n is an integer in the range of 1-5;
R1selected from substituted or unsubstituted C1-C12Alkyl, substituted or unsubstituted C2-C12Alkenyl, substituted or unsubstituted C6-C20Aryl, substituted or unsubstituted C1-C12Hydrocarbyloxy, wherein when substituted, the substituents are independently selected from silane groups, siloxane groups, amino groups, ether groups, ester groups, carboxyl groups, sulfonic acid groups, mercapto groups, cyano groups, halogens, or combinations thereof,
the anion represented by the formula I is contained in an amount of 0.001 to 7% by mass based on the total weight of the electrolyte, and
wherein the anode active material layer contains a metal element including at least one of Co, Mn, Ni, Al, or Cu; wherein the content of the metal element is 200ppm or less based on the total weight of the anode active material layer.
2. The electrochemical device of claim 1, wherein the anion represented by formula I comprises:
Figure FDA0003326410340000021
Figure FDA0003326410340000022
at least one of (1).
3. The electrochemical device of claim 1, further comprising one or more of a fluorocarboxylate ester, a sulfur-containing additive, or a lithium salt additive.
4. The electrochemical device of claim 1, wherein the fluoro carbonate further comprises at least one of propylene 3,3, 3-trifluoroparbonate, methyl 2,2,3, 3-tetrafluoropropyl carbonate, ethyl 2,2,3,3, 3-pentafluoropropyl carbonate, bis (2,2, 2-trifluoroethyl) carbonate, bis (2-fluoroethyl) carbonate, trifluoromethyl carbonate, or ethylene bis-fluorocarbonate; wherein the content of the fluoro carbonate is 0.01 to 20% based on the total weight of the electrolyte.
5. The electrochemical device of claim 3, wherein the fluorocarboxylic acid ester comprises at least one of acetylhypofluorite, 2-fluoroethyl fluoroacetate, ethyl fluorohexanoate, methyl fluoroacetate, ethyl fluoroacetate, butyl fluoroacetate, 2,2, 2-trifluoroethyl trifluoroacetate, 2-fluoroethyl 5-fluorohexanoate, 2,2, 2-trifluoroethyl difluoroacetate, 2, 2-difluoroethyltrifluoroacetate, 2-fluoroethyl 4-fluorobutyrate, ethyl trifluoropropionate, ethyl 2-fluoropropionate, ethyl 2, 2-difluoroacetate, ethyl difluoropropionate, methyl difluoroacetate, or methyl 2-fluoropropionate; wherein the fluorocarboxylic acid ester is contained in an amount of 0.01 to 30% based on the total weight of the electrolyte.
6. The electrochemical device of claim 3, wherein the sulfur-containing additive comprises at least one of 1, 3-butylidene sulfate, vinyl sulfate, 1, 3-propane sultone, 1, 3-propanediol cyclic sulfate, 2, 4-butane sultone, 1, 3-butane sultone, 1-methyl-1, 3-propane sultone, 2-methyl-1, 3-propane sultone, 3-methyl-1, 3-propane sultone, 1-fluoro-1, 3-propane sultone, 2-fluoro-1, 3-propane sultone, or 3-fluoro-1, 3-propane sultone; wherein the sulfur-containing additive is contained in an amount of 0.01 to 10% based on the total weight of the electrolyte.
7. The electrochemical device of claim 1, wherein the nitrile-containing additive further comprises at least one of the following compounds:
Figure FDA0003326410340000031
wherein M is selected from C, Si;
wherein R is51、R61、R62、R63Each independently selected from substituted or unsubstituted C1-C12Alkylene, substituted or unsubstituted C2-C12Alkenylene radical, R0-S-R group or R0-O-R group, wherein R0Each R is independently selected from substituted or unsubstitutedC1-C6Alkylene, wherein when substituted, the substituents are selected from halogen;
wherein R is64Selected from H, substituted or unsubstituted C1-C12Alkylene, substituted or unsubstituted C2-C12Alkenylene radical, R0-S-R group or R0-O-R group, wherein R0R is independently selected from substituted or unsubstituted C1-C6Alkylene, wherein when substituted, the substituents are selected from halogen.
8. The electrochemical device of claim 1, wherein the nitrile-containing additive further comprises at least one of adiponitrile, succinonitrile, glutaronitrile, malononitrile, 2-methylglutaronitrile, pimelonitrile, sebaconitrile, nonanenitrile, 1, 4-dicyano-2-butene, ethylene glycol bis (propionitrile) ether, 3' -oxydiproponitrile, thiomalononitrile, hexa-2-enedinitrile, butenenitrile, 2-pentenenitrile, ethylsuccinonitrile, hexa-3-enedinitrile, 2-methyleneglutaronitrile, 4-cyanoheptanedinitrile, 1,3, 5-hexanetricarbonitrile, 1,2, 3-propanetricitrile, or 1,2, 3-tris (2-cyanato) propane; wherein the nitrile containing additive is present in an amount of 0.01 to 10% based on the total weight of the electrolyte.
9. The electrochemical device of claim 3, wherein the lithium salt additive comprises at least one of lithium bistrifluoromethanesulfonylimide, lithium bis (fluorosulfonyl) imide, lithium bis (oxalato) borate, lithium tetrafluorophosphate oxalate, lithium difluorooxalato borate, lithium hexafluorocaesinate, or lithium difluorophosphate; wherein the lithium salt additive is contained in an amount of 0.01 to 5% based on the total weight of the electrolyte.
10. The electrochemical device of any one of claims 1-9, wherein the electrolyte further comprises at least one of the following compounds:
Figure FDA0003326410340000041
11. an electronic device comprising the electrochemical device of any one of claims 1-10.
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