CN111600065A - Electrolyte solution and electrochemical device using the same - Google Patents

Electrolyte solution and electrochemical device using the same Download PDF

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CN111600065A
CN111600065A CN202010461964.1A CN202010461964A CN111600065A CN 111600065 A CN111600065 A CN 111600065A CN 202010461964 A CN202010461964 A CN 202010461964A CN 111600065 A CN111600065 A CN 111600065A
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electrolyte
carbon atoms
compound
silicon
group
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CN111600065B (en
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文倩
唐超
刘俊飞
郑建明
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Ningde Amperex Technology Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • H01M4/625—Carbon or graphite
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The present application relates to an electrolyte and an electrochemical device using the same. The electrolyte of the present application comprises a fluorosilicone compound and a trinitrile compound, wherein the fluorosilicone compound comprises a compound of formula I:
Figure DDA0002511302490000011
and wherein the trinitrile compound comprises at least one of a compound of formula II or a compound of formula III:

Description

Electrolyte solution and electrochemical device using the same
Technical Field
The present application relates to the technical field of electrochemical devices, and more particularly, to an electrolyte and an electrochemical device using the same.
Background
With the rapid development of information technology and the proliferation of various mobile devices, the development of lithium ion batteries has received much attention. Lithium ion batteries have higher operating voltages, greater energy densities, faster charge speeds and longer operating lifetimes than other secondary batteries. In order to meet the requirements of people on light weight and small volume of equipment, a high-energy density secondary battery becomes a necessary trend for the development of lithium ion batteries.
Silicon has a reversible capacity of up to 4200mAh/g, and is the most promising negative electrode material for increasing the energy density of lithium ion batteries. However, the use of silicon-containing negative electrodes also faces many challenges, for example, the large volume expansion of silicon during charging and discharging causes the Solid Electrolyte Interface (SEI) film on the silicon surface to be damaged, the side reaction of the silicon negative electrode material and the electrolyte is aggravated, the gas generation and capacity of the battery are rapidly attenuated, and the cyclic expansion rate is increased.
Disclosure of Invention
Embodiments of the present application provide an electrolyte and an electrochemical device using the same, in an attempt to solve at least one of the problems occurring in the related art to at least some extent. The embodiment of the application also provides an electrochemical device and an electronic device using the electrolyte.
In one embodiment, the present application provides an electrolyte comprising a fluorosilicone compound and a trinitrile compound, wherein the fluorosilicone compound comprises a compound of formula I:
Figure BDA0002511302480000011
wherein R is1、R2、R3、R4、R5、R6Each independently selected from hydrogen, fluorine atoms, alkyl groups of 1 to 12 carbon atoms, fluoroalkyl groups of 3 to 12 carbon atomsA cycloalkyl group, a fluorocycloalkyl group of 3 to 12 carbon atoms, an alkenyl group of 2 to 12 carbon atoms, a fluoroalkenyl group of 2 to 12 carbon atoms, a heterocyclic group of 3 to 12 carbon atoms or a fluorinated heterocyclic group of 3 to 12 carbon atoms, and wherein R is1、R2、R3、R4、R5、R6At least one of which is a fluorine atom, a fluoroalkyl group of 1 to 12 carbon atoms, a fluorocycloalkyl group of 3 to 12 carbon atoms, a fluoroalkenyl group of 2 to 12 carbon atoms or a fluoroheterocyclic group of 3 to 12 carbon atoms;
and wherein the trinitrile compound comprises at least one of a compound of formula II or a compound of formula III:
Figure BDA0002511302480000021
wherein a, b, c, d, e, f, g, h and i are integers from 0 to 5.
In some embodiments, the fluorosilicone compound includes at least one of:
Figure BDA0002511302480000022
in some embodiments, the trinitrile compound comprises at least one of:
Figure BDA0002511302480000023
Figure BDA0002511302480000031
in some embodiments, the fluorosilicone compound is present in an amount of 0.01 wt% to 6 wt% and the nitrile compound is present in an amount of 0.01 wt% to 8 wt%, based on the total weight of the electrolyte.
In some embodiments, the electrolyte further comprises an additive comprising at least one of the following compounds: vinylene carbonate, 1, 3-propane sultone, vinyl sulfate, succinonitrile, adiponitrile or fluoroethylene carbonate, wherein the weight percentage of the additive is 0.01-20 wt% based on the total weight of the electrolyte.
In another embodiment, the present application provides an electrochemical device comprising a positive electrode, a negative electrode, and an electrolyte according to embodiments of the present application.
In some embodiments, the anode comprises a silicon-based anode active material comprising a silicon-containing matrix comprising Si, silicon oxide SiOxOr Si-M alloy, wherein x is more than or equal to 0.6 and less than or equal to 2, and M is selected from at least one of Al, Ti, Fe or Ni.
In some embodiments, the silicon-based anode active material further includes an oxide MeaObLayer of said oxide MeaObA layer is located on at least a portion of the surface of the silicon-containing substrate, wherein Me comprises at least one of Al, Si, Ti, Mn, V, Cr, Co, or Zr, a is 1-3, b is 1-4, and wherein the oxide Me isaObThe thickness of the layer is 1nm-500 nm.
In some embodiments, the negative electrode further comprises a conductive agent comprising at least one of carbon nanotubes, graphene, or carbon black, wherein the carbon nanotubes have a diameter of 1-100nm and a length of 1-50 μm.
In some embodiments, the silicon-based negative active material further comprises a carbon layer on at least a portion of the surface of the silicon-containing matrix, and the carbon layer has a thickness of 1-500 nm.
In another embodiment, the present application provides an electronic device comprising an electrochemical device according to an embodiment of the present application.
The electrolyte provided by the application can form a stable Solid Electrolyte Interface (SEI) protective layer on the surfaces of the positive electrode and the negative electrode, and can obviously improve the normal-temperature and high-temperature cycle performance of the lithium ion secondary battery. Particularly when the silicon-based active material is applied to a battery with a negative electrode containing a silicon-based active material, the good stability of an SEI (solid electrolyte interphase) protective layer of the negative electrode after the battery is cycled can be ensured, so that the cycle performance of the battery is improved.
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 below. The embodiments of the present application should not be construed as limiting the present application.
In the detailed description and claims, a list of items connected by the terms "one of," "one of," or other similar terms may mean any one of the listed items. For example, if items a and B are listed, the phrase "one of a and B" means a alone or B alone. In another example, if items A, B and C are listed, the phrase "one of A, B and C" means only a; only B; or only C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements.
In the detailed description and claims, a list of items 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 element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements.
As used herein, 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 can 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.
As used herein, the term "cycloalkyl" encompasses cyclic alkyl groups. The cycloalkyl group may be a cycloalkyl group of 3 to 20 carbon atoms, a cycloalkyl group of 6 to 20 carbon atoms, a cycloalkyl group of 3 to 12 carbon atoms, a cycloalkyl group of 3 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" as used herein 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 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 12 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.
As used herein, the term "heterocyclic group" 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 heteroatom3-C20Heterocyclic group, C3-C150Heterocyclic group, C3-C10Heterocyclic group, C5-C20Heterocyclic group, C5-C10Heterocyclic group, C3-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 "trinitrile compound" refers to a compound containing three-CN functional groups.
As used herein, the term "heteroatom" encompasses O, S, P, N, B or an isostere thereof.
As used herein, the term "halogen" encompasses F, Cl, Br, I.
When the above substituents are substituted, their substituents may each be independently selected from the group consisting of: halogen, alkyl, alkenyl, aryl.
As used herein, the content of each component is obtained based on the total weight of the electrolyte.
As used herein, the term "substituted" or "substituted" means that it may be substituted with 1 or more (e.g., 2, 3) substituents. For example, "fluoro" means that it may be substituted with 1 or more (e.g., 2, 3) F.
First, electrolyte
In some embodiments, the present application provides an electrolyte comprising a fluorosilicone compound and a trinitrile compound, wherein the fluorosilicone compound comprises a compound of formula I:
Figure BDA0002511302480000061
wherein R is1、R2、R3、R4、R5、R6Each independently selected from hydrogen, fluorine atom, alkyl group of 1 to 12 carbon atoms, fluoroalkyl group of 1 to 12 carbon atoms, cycloalkyl group of 3 to 12 carbon atoms, fluorocycloalkyl group of 3 to 12 carbon atoms, alkenyl group of 2 to 12 carbon atoms, fluoroalkenyl group of 2 to 12 carbon atoms, heterocyclic group of 3 to 12 carbon atoms or fluorinated heterocyclic group of 3 to 12 carbon atoms, and wherein R is1、R2、R3、R4、R5、R6At least one of which is a fluorine atom, a fluoroalkyl group of 1 to 12 carbon atoms, a fluorocycloalkyl group of 3 to 12 carbon atoms, a fluoroalkenyl group of 2 to 12 carbon atoms or a fluoroheterocyclic group of 3 to 12 carbon atoms;
and wherein the trinitrile compound comprises or is selected from at least one of a compound of formula II or a compound of formula III:
Figure BDA0002511302480000062
wherein a, b, c, d, e, f, g, h and i are integers from 0 to 5.
In some embodiments, the fluorosilicone compound includes or is selected from at least one of the following compounds:
Figure BDA0002511302480000063
Figure BDA0002511302480000071
in some embodiments, the trinitrile compound comprises or is selected from at least one of the following compounds:
Figure BDA0002511302480000072
in some embodiments, the weight percentage of the fluorosilicone compound is 0.01 wt% to 6 wt% based on the total weight of the electrolyte. In some embodiments, the weight percent of the fluorosilicone compound is 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 6 wt%, or a range consisting of any two of these values, based on the total weight of the electrolyte.
In some embodiments, the weight percentage of the trinitrile compound is 0.01 wt% to 8 wt% based on the total weight of the electrolyte. In some embodiments, the weight percentage of the trinitrile compound is 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 8 wt%, or a range consisting of any two of these values, based on the total weight of the electrolyte.
In some embodiments, the electrolyte further comprises an additive comprising at least one of the following compounds: vinylene carbonate, 1, 3-propane sultone, vinyl sulfate, succinonitrile, adiponitrile or fluoroethylene carbonate.
In some embodiments, the weight percentage of the additive is 0.01 wt% to 20 wt% based on the total weight of the electrolyte. In some embodiments, the weight percent of the additive is 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 10 wt%, 11 wt%, 15 wt%, 18 wt%, 20 wt%, or a range consisting of any two of these values, based on the total weight of the electrolyte.
In some embodiments, the electrolyte further comprises a cyclic ether. The cyclic ether can form a film on the cathode and the anode simultaneously, and the reaction of the electrolyte and the active material is reduced.
In some embodiments, the cyclic ethers include, but are not limited to: tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, 2-methyl-1, 3-dioxolane, 4-methyl-1, 3-dioxolane, 1, 3-dioxane, 1, 4-dioxane, dimethoxypropane.
In some embodiments, the weight percentage of the cyclic ether is 0.1 wt% to 10 wt% based on the total weight of the electrolyte. In some embodiments, the weight percentage of the cyclic ether is not less than 0.1 wt% based on the total weight of the electrolyte. In some embodiments, the weight percentage of the cyclic ether is not less than 0.5 wt% based on the total weight of the electrolyte. In some embodiments, the weight percentage of the cyclic ether is no greater than 2 wt% based on the total weight of the electrolyte. In some embodiments, the weight percentage of the cyclic ether is no greater than 5 wt% based on the total weight of the electrolyte.
In some embodiments, the electrolyte further comprises a chain ether. In some embodiments, chain ethers include, but are not limited to: dimethoxymethane, 1-dimethoxyethane, 1, 2-dimethoxyethane, diethoxymethane, 1-diethoxyethane, 1, 2-diethoxyethane, ethoxymethoxymethane, 1-ethoxymethoxyethane, 1, 2-ethoxymethoxyethane.
In some embodiments, the weight percentage of the chain ether is 0.1 wt% to 10 wt% based on the total weight of the electrolyte. In some embodiments, the weight percentage of the chain ether is not less than 0.5 wt% based on the total weight of the electrolyte. In some embodiments, the weight percentage of the chain ether is not less than 2 wt% based on the total weight of the electrolyte. In some embodiments, the weight percentage of the chain ether is not less than 3 wt% based on the total weight of the electrolyte. In some embodiments, the weight percentage of the chain ethers is not greater than 10 wt% based on the total weight of the electrolyte. In some embodiments, the weight percentage of the chain ethers is not greater than 5 wt% based on the total weight of the electrolyte.
In some embodiments, the electrolyte further comprises a phosphorus-containing organic solvent. The phosphorus-containing organic solvent can enhance the safety performance of the electrolyte. In some embodiments, the phosphorus-containing organic solvent includes, but is not limited to: trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphate, tris (2,2, 2-trifluoroethyl) phosphate, tris (2,2,3,3, 3-pentafluoropropyl) phosphate.
In some embodiments, the weight percentage of the phosphorus-containing organic solvent is 0.1 wt% to 10 wt% based on the total weight of the electrolyte. In some embodiments, the weight percentage of the phosphorus-containing organic solvent is not less than 0.1 wt% based on the total weight of the electrolyte. In some embodiments, the weight percentage of the phosphorus-containing organic solvent is not less than 0.5 wt% based on the total weight of the electrolyte. In some embodiments, the weight percentage of the phosphorus-containing organic solvent is no greater than 2 wt%, based on the total weight of the electrolyte. In some embodiments, the weight percentage of the phosphorus-containing organic solvent is no greater than 3 wt%, based on the total weight of the electrolyte. In some embodiments, the weight percentage of the phosphorus-containing organic solvent is no greater than 5 wt%, based on the total weight of the electrolyte.
In some embodiments, the electrolyte further comprises an aromatic fluorine-containing solvent. The aromatic fluorine-containing solvent can quickly form a film to protect the active material, and the fluorine-containing substance can improve the wetting performance of the electrolyte on the active material. In some embodiments, the aromatic fluorine-containing solvent includes, but is not limited to: fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene and trifluoromethylbenzene.
In some embodiments, the weight percent of the aromatic fluorine-containing solvent is about 0.1 wt% to 10 wt% based on the total weight of the electrolyte. In some embodiments, the weight percent of the aromatic fluorine-containing solvent is not less than 0.5 wt% based on the total weight of the electrolyte. In some embodiments, the weight percent of the aromatic fluorine-containing solvent is not less than 2 wt% based on the total weight of the electrolyte. In some embodiments, the weight percent of the aromatic fluorine-containing solvent is not greater than 4 wt% based on the total weight of the electrolyte. In some embodiments, the weight percent of the aromatic fluorine-containing solvent is not greater than 8 wt% based on the total weight of the electrolyte.
In some embodiments, the electrolyte further comprises a lithium salt additive. In some embodiments, the lithium salt additive includes, but is not limited to, lithium trifluoromethanesulfonylimide 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), lithium oxalate tetrafluorophosphate (LiPF4C2O2), lithium difluoroborate LiBF2(C2O4) (abbreviated as LiDFOB) and lithium hexafluorocaesium acid (LiCSF)6)。
In some embodiments, the weight percentage of the lithium salt additive is 0.01 wt% to 10 wt% based on the total weight of the electrolyte. In some embodiments, the weight percentage of the lithium salt additive is 0.1 wt% to 5 wt% based on the total weight of the electrolyte. In some embodiments, the weight percentage of the lithium salt additive is 0.1 wt%, 1 wt%, 3 wt%, 5 wt%, 7 wt%, 9 wt%, 10 wt%, or a range consisting of any two of these values, based on the total weight of the electrolyte.
The application provides an electrolyte containing a fluorosilicone compound and a trinitrile compound, which can form a stable SEI (solid electrolyte interphase) protective layer on the surfaces of a positive electrode and a negative electrode and can obviously improve the normal-temperature and high-temperature cycle performance of a secondary battery. Particularly when the silicon-based active material is applied to a battery with a negative electrode containing a silicon-based active material, the good stability of an SEI (solid electrolyte interphase) protective layer of the negative electrode after the battery is cycled can be ensured, so that the cycle performance of the battery is improved.
II, electrolyte
The electrolyte used in the electrolyte of the embodiment of the present application may be an electrolyte known in the art, and the electrolyte includes, but is not limited to: inorganic lithium salts, e.g. LiClO4、LiAsF6、LiPF6、LiBF4、LiSbF6、LiSO3F、LiN(FSO2)2Etc.; organic lithium salts containing fluorine, e.g. LiCF3SO3、LiN(FSO2)(CF3SO2)、LiN(CF3SO2)2、LiN(C2F5SO2)2Cyclic 1, 3-hexafluoropropane disulfonimide lithium, cyclic 1, 2-tetrafluoroethane disulfonimide lithium, LiN (CF)3SO2)(C4F9SO2)、LiC(CF3SO2)3、LiPF4(CF3)2、LiPF4(C2F5)2、LiPF4(CF3SO2)2、LiPF4(C2F5SO2)2、LiBF2(CF3)2、LiBF2(C2F5)2、LiBF2(CF3SO2)2、LiBF2(C2F5SO2)2(ii) a The dicarboxylic acid complex-containing lithium salt may, for example, be lithium bis (oxalato) borate, lithium difluorooxalato borate, lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate, or the like. The electrolyte may be used alone or in combination of two or more. For example, in some embodiments, the electrolyte comprises LiPF6And LiBF4Combinations of (a) and (b). In some embodiments, the electrolyte comprises LiPF6Or LiBF4An inorganic lithium salt and LiCF3SO3、LiN(CF3SO2)2、LiN(C2F5SO2)2And the like, a combination of fluorine-containing organic lithium salts. In some embodiments, the concentration of the electrolyte is in the range of 0.8 to 3mol/L, such as in the range of 0.8 to 2.5mol/L, in the range of 0.8 to 2mol/L, in the range of 1 to 2mol/L, 0.5 to 1.5mol/L, 0.8 to 1.3mol/L, 0.5 to 1.2mol/L, and again, such as 1mol/L, 1.15mol/L, 1.2mol/L, 1.5mol/L, 2mol/L, or 2.5 mol/L.
Third, negative pole
In some embodiments, the present application provides an anode comprising a current collector and a coating on the current collector, the coating comprising a silicon-based anode active material.
In some embodiments, the silicon-based negative active material comprises a silicon-containing matrix comprising Si, silicon oxide SiOxAnd at least one of Si-M alloy, wherein x is more than or equal to 0.6 and less than or equal to 2, and M is selected from at least one of Al, Ti, Fe or Ni.
In some embodiments, the silicon-containing matrix comprises Si, SiO2At least one of SiO or SiC.
In some embodiments, the silicon-based anode active material further includes an oxide MeaObLayer of said oxide MeaObA layer is on at least a portion of a surface of the silicon-containing substrate, wherein Me comprises at least one of Al, Si, Ti, Mn, V, Cr, Co, or Zr, anda is 1-3, b is 1-4.
In some embodiments, the oxide MeaObThe thickness of the layer is 1nm-500 nm. In some embodiments, the oxide MeaObThe thickness of the layer is 1nm, 5nm, 10nm, 20nm, 30nm, 50nm, 80nm, 120nm, 150nm, 200nm, 300nm, 400nm, 450nm, 500nm, or a range consisting of any two of these values.
In some embodiments, the oxide MeaObIncluding Al2O3、TiO2CoO and ZrO2At least one of (1).
In some embodiments, the negative electrode further comprises a conductive agent comprising at least one of carbon nanotubes, graphene, or carbon black.
In some embodiments, the carbon nanotubes have a diameter of 1-100 nm. In some embodiments, the carbon nanotubes have a diameter of 1nm, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 70nm, 80nm, 90nm, 100nm, or a range consisting of any two of these values.
In some embodiments, the carbon nanotubes have a length of 1-50 μm. In some embodiments, the carbon nanotubes have a length of 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 45 μm, 50 μm, or a range consisting of any two of these values.
In some embodiments, the carbon nanotubes have an aspect ratio of 0.1 to 5000. In some embodiments, the carbon nanotubes have an aspect ratio of 0.1, 7, 10, 50, 100, 200, 500, 1000, 2000, 2500, 2800, 3000, 3500, 4000, 4500, 5000, or a range consisting of any two of these values.
In some embodiments, the silicon-based negative active material further comprises a carbon layer on at least a portion of a surface of the silicon-containing matrix. In some embodiments, the carbon layer has a thickness of 1-500 nm. In some embodiments, the carbon layer has a thickness of 1nm, 5nm, 10nm, 30nm, 40nm, 50nm, 80nm, 100nm, 150nm, 200nm, 250nm, 300nm, 400nm, 500nm, or a range consisting of any two of these values.
In some embodiments, the carbon layer comprises at least one of amorphous carbon, graphite, hard carbon, soft carbon, carbon black, acetylene black, or carbon nanotubes.
In some embodiments, the coating further comprises graphite particles. In some embodiments, the weight ratio of the silicon-based negative active material to the graphite particles is 1:30 to 1: 10. In some embodiments, the weight ratio of the silicon-based negative active material to the graphite particles is 1:30, 1:25, 1:20, 1:15, 1:10, or a range consisting of any two of these values.
In some embodiments, the coating further comprises a thickening agent. In some embodiments, the thickener comprises at least one of sodium carboxymethylcellulose (CMC-Na), lithium carboxymethylcellulose (CMC-Li), and cellulose.
In some embodiments, the coating further comprises a binder comprising polyacrylate, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, styrene butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, or any combination thereof.
In some embodiments, the current collector comprises copper, aluminum, nickel, a copper alloy, an aluminum alloy, a nickel alloy, or a combination thereof.
In some embodiments, a silicon-based negative active material (which includes a silicon-containing matrix and an oxide Me on at least a portion of a surface of the silicon-containing matrixaObLayer) comprising:
(1) mixing silicon-containing matrix and oxide precursor MeTnForming a mixed solution in the presence of an organic solvent and deionized water;
(2) drying the mixed solution to obtain powder; and
(3) sintering the powder at the temperature of 200-1000 ℃ for 0.5-25h to obtain the silicon-based negative active material;
wherein a is 1-3, b is 1-4,
wherein Me comprises at least one of Al, Si, Ti, Mn, Cr, V, Co or Zr,
wherein T comprises at least one of methoxy, ethoxy, isopropoxy, or halogen, and
wherein n is 1,2, 3 or 4.
In some embodiments, the oxide precursor MeTnIncluding isopropyl titanate, aluminum isopropoxide, or combinations thereof.
In some embodiments, the silicon-containing matrix is as defined above.
In some embodiments, the sintering temperature is 250-. In some embodiments, the sintering temperature is 300-. In some embodiments, the sintering temperature is 350-. In some embodiments, the sintering temperature is 400 ℃, 500 ℃, 600 ℃, or 700 ℃.
In some embodiments, the sintering time is 1-25 hours. In some embodiments, the sintering time is 1-119 h. In some embodiments, the sintering time is 1-14 hours. In some embodiments, the sintering time is 1.5 to 5 hours. In some embodiments, the sintering time is 2h, 3h, 4h, 5h, 6h, 8h, or 10 h.
In some embodiments, the organic solvent comprises at least one of: ethanol, methanol, N-hexane, N-dimethylformamide, pyrrolidone, acetone, toluene, isopropanol or N-propanol. In some embodiments, the organic solvent is ethanol.
In some embodiments, the halogen comprises F, Cl, Br, or a combination thereof.
In some embodiments, the sintering is performed under an inert gas blanket. In some embodiments, the inert gas comprises nitrogen, argon, or a combination thereof.
In some embodiments, the drying is spray drying at a drying temperature of 100-.
In some embodiments, the negative electrode may be obtained by: the negative active material, the conductive agent, the thickener, and the binder are mixed in a solvent to prepare an active material composition slurry, and the slurry is coated on a current collector.
In some embodiments, the oxide MeaObThe thickness of the layer is controlled by controlling the oxideThe weight of the precursor.
In some embodiments, the solvent may include, but is not limited to: n-methyl pyrrolidone and deionized water.
According to the electrolyte disclosed by the application, a stable SEI (solid electrolyte interphase) protective layer can be generated on the surface of the silicon-based negative electrode active material, and compared with an SEI layer formed by the traditional fluoroethylene carbonate (FEC) or ethylene carbonate (VC), the SEI protective layer is not easy to peel off from the silicon-based negative electrode active material in a circulation process, so that the circulation capacity retention rate of a lithium ion battery (silicon negative electrode lithium ion battery) using the silicon-based negative electrode active material can be effectively improved, the expansion of the battery in the circulation process is relieved, the high-temperature resistance of the battery after circulation can be improved, and the thermal runaway of the silicon negative electrode lithium ion battery is avoided.
On the other hand, although the electrolyte can effectively improve the stability of the SEI protective layer, the SEI protective layer needs to continuously consume additives for repairing due to the huge volume expansion of the silicon-based negative active material particles, and the consumption rate of the additives is increased. In view of the above, the present application provides an oxide Me on the surface of a silicon-containing substrate of a part of silicon-based anode active materialaObLayer and/or carbon layer, the oxide MeaObThe layer or the carbon layer has certain mechanical strength, can effectively inhibit the volume expansion of the silicon-based negative active material, and can also inhibit the etching of HF in the electrolyte on the surface of the silicon-based negative active material. An electrolyte containing an SEI film-forming additive of a fluorosilicone and a trinitrile compound and an oxide Me on the surfaceaObThe silicon-based negative active material of the layer or the carbon layer is combined for use, so that the cycle stability and the cycle capacity retention rate of the lithium ion battery can be effectively improved, and the cycle thickness expansion rate of the lithium ion battery is reduced.
In addition, the conductivity of the silicon-based negative active material is not ideal, and the silicon-based negative active material cannot support the high-rate charging performance in the full battery cycle and also has a certain influence on the cycle performance. The carbon material has good conductivity, mechanical strength and ductility, so in order to improve the conductivity of the negative electrode containing the silicon-based negative electrode active material, the carbon layer is arranged on the surface of a silicon-containing matrix of part of the silicon-based negative electrode active material, and the carbon nanotube conductive agent is doped in the negative electrode active material, so that the cycle performance of the battery is effectively improved.
Four, electrochemical device
The electrochemical device of the present application includes 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, an electrochemical device according to the present application is an electrochemical device including a positive electrode having a positive electrode active material capable of occluding and releasing metal ions and a negative electrode having a negative electrode active material capable of occluding and releasing metal ions, and includes an electrolytic solution according to any one of the embodiments described above.
1. Electrolyte solution
The electrolyte used in the electrochemical device of the present application is the electrolyte of any of the embodiments 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.
2. Negative electrode
The negative electrode used in the electrochemical device of the present application is a conventional negative electrode in the prior art, or a negative electrode according to any of the above embodiments in the present application. The negative electrode used in the electrochemical device of the present application may further include other negative electrodes within a range not departing from the gist of the present application.
3. Positive electrode
The material of the positive electrode used in the electrochemical device of the present application may be prepared using materials, configurations, and manufacturing methods well known in the art. In some embodiments, the positive electrode of the present application can be prepared using the techniques described in US9812739B, which is incorporated by reference in its entirety.
In some embodiments, the positive electrode includes a current collector and a positive active material layer on the current collector. 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 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, Zr, F, or any combination thereof. 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 aluminum, but is not limited thereto.
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 electrode active material layer may be generally fabricated by: the positive electrode 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, and the slurry is applied to a 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.
4. 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 separation film 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 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, 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).
Fifth, application
The electrolyte solution provided by the embodiment of the application can be used for improving the rate performance, the normal-temperature storage capacity retention rate and the cycle and high-temperature storage performance of a battery, and is suitable for being used in electronic equipment comprising an electrochemical device.
The use of the electrochemical device of the present application is not particularly limited, and the electrochemical device can be used for various known uses. Such as 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 supply, a 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 battery for home use, or a lithium ion capacitor.
While the following lithium ion battery is taken as an example and the specific examples for preparing the electrolyte and the test method for electrochemical devices are combined to illustrate the preparation and performance of the lithium ion battery, those skilled in the art will understand that the preparation method described in the present application is only an example, and any other suitable preparation method is within the scope of the present application.
Although illustrated as a lithium ion battery, one skilled in the art will appreciate after reading this application that the cathode materials of the present application may be used in other suitable electrochemical devices. Such an electrochemical device includes 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.
Examples
The present application will be described in more detail below with reference to examples and comparative examples, but the present application is not limited to these examples as long as the gist thereof is not deviated.
Preparation of lithium ion battery
(1) Preparing an electrolyte:
in a drying room, Ethylene Carbonate (EC), Propylene Carbonate (PC) and diethyl carbonate (DEC) are uniformly mixed according to the weight ratio of 20:10:70, and then the fully dried lithium salt LiPF6Dissolving the mixed solvent to obtain a basic electrolyte, wherein LiPF is contained in the basic electrolyte6The concentration of (2) is 1 mol/L. To the base electrolyte, fluorosilicones, a trinitrile compound and fluoroethylene carbonate (FEC) were added in different amounts as shown in table 1 to obtain electrolytes of different examples and comparative examples. The contents of each substance in the electrolyte described below were calculated based on the total weight of the electrolyte.
(2) Preparation of the positive electrode:
1.42kg of solvent N-methyl-2-pyrrolidone (NMP), 1.2kg of binder polyvinylidene fluoride (PVDF) with a mass fraction of 10%, 0.16kg of conductive graphite as a conductive agent, and 7.2kg of positive electrode active material LiCoO were weighed2Fully mixing and stirring to obtain anode slurry, uniformly coating the anode slurry on an anode current collector aluminum foil with the thickness of 10 mu m, baking for 1h at 120 ℃ to obtain an anode diaphragm, and compacting and cutting to obtain the anode.
(3) And (3) isolation film: polyethylene (PE) porous polymer films were used as separators.
(4) Preparing a 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) placing the bare cell in an outer packaging foil, injecting the prepared electrolyte into the dried cell, and performing vacuum packaging, standing, formation, shaping and other processes to complete the preparation of the lithium ion battery.
(5) Preparation of a negative electrode:
1) dispersing 100g of silica (SiO, Dv50 is 7 μm) powder in 300ml of ethanol which is an organic solvent, and stirring for 0.5-1h until a uniform suspension is formed;
2) adding 0.5-10g of oxide precursor aluminum isopropoxide into the suspension, stirring for 0.5-1h until a uniform mixed solution is formed, dropwise adding deionized water into the mixed solution, wherein the weight of the deionized water is about 3 times of that of the precursor, and continuously stirring for 4h after dropwise adding completely to obtain the mixed solution;
3) spray drying (inlet temperature 220 ℃, outlet temperature about 110 ℃) the mixed solution to obtain powder;
4) sintering the powder at 600 ℃ for 2h to obtain the oxide Me with the surfaceaOb(Here, it isAl2O3) Silicon-based particles of the layer as a silicon-based negative active material;
5) weighing 1.2kg of thickener sodium carboxymethylcellulose (CMC-Na) solution with the mass fraction of 1.5%, 0.07kg of binder styrene-butadiene rubber emulsion with the mass fraction of 50%, 2.0kg of graphite powder negative electrode active material, 0.01kg of conductive carbon nano tube and 0.4kg of silicon-based negative electrode active material (commercially available, and the Dv50 is 7 mu m) with the surface coated with a hard carbon layer on a silicon-containing matrix (SiO); fully mixing and stirring the materials to obtain negative electrode slurry; and
6) and uniformly coating the negative electrode slurry on a negative electrode current collector copper foil with the thickness of 8 mu m, baking for 1h at 120 ℃ to obtain a negative electrode diaphragm, and compacting and slitting to obtain the negative electrode.
Table 1 shows the kinds and contents of the relevant substances of the electrolytes in examples 1 to 65 and comparative examples 1 to 4 and the kinds and amounts of the respective substances used in steps 1) to 5) in examples 1 to 65 and comparative examples 1 to 4 and the relevant parameters. The order of the kind and content of the additives in Table 1 is the same, for example, the kind and content of the additive in example 22 are FEC:5 wt% + PS:0.5 wt% + SN:1.5 wt%. Oxide MeaObThe thickness of the layer is controlled by controlling the weight of the oxide precursor.
TABLE 1
Figure BDA0002511302480000181
Figure BDA0002511302480000191
Figure BDA0002511302480000201
Wherein "-" represents the absence of the substance.
The full names of the English abbreviations in Table 1 are as follows:
FEC: fluoroethylene carbonate
PS: 1, 3-propane sultone
SN: succinonitrile and its use
The lithium ion secondary batteries of examples 1 to 65 and comparative examples 1 to 4 were subjected to the following performance tests:
(1) and (3) testing the normal-temperature cycle performance:
the lithium ion secondary battery is stood for 30 minutes at 25 ℃, charged with a constant current of 0.5C until the voltage is 4.45V, charged with a constant voltage of 4.45V until the current is 0.05C, stood for 5 minutes, and discharged with a constant current of 0.5C until the voltage is 3.0V, and the discharge capacity is taken as a charge-discharge cycle process, and the discharge capacity is the first discharge capacity of the lithium ion secondary battery. And (4) carrying out a cyclic charge-discharge test on the lithium ion secondary battery according to the above mode until the capacity retention rate is less than 80%, and stopping the test, and recording the number of cycle turns of different groups.
The capacity retention (%) after N cycles of the lithium ion secondary battery was equal to the discharge capacity/first discharge capacity of the N-th cycle × 100%.
(2) And (3) testing high-temperature cycle performance:
the lithium ion secondary battery is stood for 30 minutes at the temperature of 45 ℃, charged by a constant current of 0.5C until the voltage is 4.45V, charged by a constant voltage of 4.45V until the current is 0.05C, stood for 5 minutes, and discharged by a constant current of 0.5C until the voltage is 3.0V, and the discharge capacity is taken as a charge-discharge cycle process, and the discharge capacity is the first discharge capacity of the lithium ion secondary battery. And (4) carrying out a cyclic charge-discharge test on the lithium ion secondary battery according to the above mode until the capacity retention rate is less than 80%, and stopping the test, and recording the number of cycle turns of different groups.
The capacity retention (%) after N cycles of the lithium ion secondary battery was equal to the discharge capacity/first discharge capacity of the N-th cycle × 100%.
Table 2 shows the results of performance tests of the lithium ion secondary batteries of examples 1 to 65 and comparative examples 1 to 4.
TABLE 2
Figure BDA0002511302480000211
Figure BDA0002511302480000221
It can be seen from the test results of examples 1 to 65 and comparative examples 1 to 4 that the normal temperature and high temperature cycle performance of the lithium ion secondary battery is significantly improved when the fluorosilicone compound and the trinitrile compound are simultaneously added to the electrolyte. And when the oxide Me isaObWhen the thickness of the layer, the thickness of the carbon layer and the length-diameter ratio of the carbon nano tube are in a certain range, the normal temperature and high temperature cycle performance of the lithium ion secondary battery is further improved.
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 (11)

1. An electrolyte comprising a fluorosilicone compound and a trinitrile compound, wherein the fluorosilicone compound comprises a compound of formula I:
Figure FDA0002511302470000011
wherein R is1、R2、R3、R4、R5Or R6Each independently selected from hydrogen, fluorine atom, alkyl group of 1 to 12 carbon atoms, fluoroalkyl group of 1 to 12 carbon atoms, cycloalkyl group of 3 to 12 carbon atoms, fluorocycloalkyl group of 3 to 12 carbon atoms, alkenyl group of 2 to 12 carbon atoms, fluoroalkenyl group of 2 to 12 carbon atoms, heterocyclic group of 3 to 12 carbon atoms or fluorinated heterocyclic group of 3 to 12 carbon atoms, and wherein R is1、R2、R3、R4、R5Or R6At least one of which is a fluorine atom, a fluoroalkyl group of 1 to 12 carbon atoms, a fluorocycloalkyl group of 3 to 12 carbon atoms, a fluoroalkenyl group of 2 to 12 carbon atoms or a fluoroheterocyclic group of 3 to 12 carbon atoms;
and wherein the trinitrile compound comprises at least one of a compound of formula II or a compound of formula III:
Figure FDA0002511302470000012
wherein a, b, c, d, e, f, g, h and i are integers from 0 to 5.
2. The electrolyte of claim 1, wherein the fluorosilicone compound comprises at least one of:
Figure FDA0002511302470000013
3. the electrolyte of claim 1, wherein the trinitrile compound comprises at least one of:
Figure FDA0002511302470000021
4. the electrolyte of claim 1, wherein the fluorosilicone compound is present in an amount of 0.01 wt% to 6 wt% and the nitrile compound is present in an amount of 0.01 wt% to 8 wt%, based on the total weight of the electrolyte.
5. The electrolyte of claim 1, further comprising an additive comprising at least one of the following compounds: vinylene carbonate, 1, 3-propane sultone, vinyl sulfate, succinonitrile, adiponitrile or fluoroethylene carbonate, wherein the weight percentage of the additive is 0.01-20 wt% based on the total weight of the electrolyte.
6. An electrochemical device, wherein the electrochemical device comprises a positive electrode, a negative electrode, and the electrolyte of any one of claims 1-5.
7. The electrochemical device of claim 6, wherein the negative electrode comprises a silicon-based negative active material comprising a silicon-containing matrix comprising Si, silicon oxide SiOxOr Si-M alloy, wherein x is more than or equal to 0.6 and less than or equal to 2, and M is selected from at least one of Al, Ti, Fe or Ni.
8. The electrochemical device according to claim 7, wherein the silicon-based anode active material further comprises an oxide MeaObLayer of said oxide MeaObA layer is located on at least a portion of the surface of the silicon-containing substrate, wherein Me comprises at least one of Al, Si, Ti, Mn, V, Cr, Co, or Zr, a is 1-3, b is 1-4, and wherein the oxide Me isaObThe thickness of the layer is 1nm-500 nm.
9. The electrochemical device of claim 6, wherein the negative electrode further comprises a conductive agent comprising at least one of carbon nanotubes, graphene, or carbon black, wherein the aspect ratio of the carbon nanotubes is between 0.1 and 50000.
10. The electrochemical device according to claim 7, wherein the silicon-based negative active material further comprises a carbon layer on at least a portion of a surface of the silicon-containing substrate, and the carbon layer has a thickness of 1-500 nm.
11. An electronic device, wherein the electronic device comprises the electrochemical device according to any one of claims 6-10.
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