WO2021179300A1 - 电化学装置及包含其的电子装置 - Google Patents

电化学装置及包含其的电子装置 Download PDF

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WO2021179300A1
WO2021179300A1 PCT/CN2020/079264 CN2020079264W WO2021179300A1 WO 2021179300 A1 WO2021179300 A1 WO 2021179300A1 CN 2020079264 W CN2020079264 W CN 2020079264W WO 2021179300 A1 WO2021179300 A1 WO 2021179300A1
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Prior art keywords
lithium
substituted
electrolyte
electrochemical device
active material
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PCT/CN2020/079264
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English (en)
French (fr)
Inventor
栗文强
管明明
郑建明
郑湘岭
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宁德新能源科技有限公司
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Priority to EP20866935.8A priority Critical patent/EP3907804A4/en
Priority to US17/281,881 priority patent/US20220149431A1/en
Priority to PCT/CN2020/079264 priority patent/WO2021179300A1/zh
Publication of WO2021179300A1 publication Critical patent/WO2021179300A1/zh

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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
    • H01M10/42—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
    • 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
    • H01M10/056—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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application relates to the field of energy storage technology, and more specifically, to an electrochemical device and an electronic device containing the same.
  • lithium-ion batteries are widely used in the field of consumer electronics due to their advantages of large specific energy, high working voltage, low self-discharge rate, small size, and light weight.
  • the present application introduces an anion having a phosphoric anhydride functional group into the electrolyte of the electrochemical device.
  • the rapid transmission of lithium ions can be promoted, thereby improving the rate performance of the electrochemical device and its discharge performance at low temperatures.
  • the bridging structure of the phosphoric anhydride functional group and the negative charge of the anion it is helpful to form a protective film on the positive electrode, thereby improving the cycle stability and high-temperature storage performance of the electrochemical device.
  • the present application provides an electrochemical device, including: a positive electrode, the positive electrode including a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer including a positive electrode active material; a negative electrode, the negative electrode including A negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer comprising a negative electrode active material; and an electrolyte, the electrolyte comprising lithium ions and an anion represented by formula I:
  • n is an integer in the range of 0-5;
  • R 1 is selected from substituted or unsubstituted C 1 -C 12 alkyl, substituted or unsubstituted C 2 -C 12 alkenyl, substituted or unsubstituted C 6 -C 20 aryl, A substituted or unsubstituted C 1 -C 12 hydrocarbyloxy group, wherein when substituted, the substituents are independently selected from the group consisting of silyl groups, siloxane groups, amino groups, ether groups, ester groups, carboxyl groups, sulfonic acid groups, Mercapto, cyano, halogen, or a combination thereof.
  • anion represented by formula I comprises:
  • the mass percentage of the anion represented by Formula I is 0.001% to 7%.
  • the electrolyte further includes one or more of fluorocarbonate, fluorocarboxylate, sulfur-containing additives, nitrile-containing additives, or lithium salt additives.
  • the fluorocarbonate includes 3,3,3-trifluoropropylene carbonate, fluoroethylene carbonate, 2,2,3,3-tetrafluoropropyl methyl carbonate, 2 ,2,3,3,3-Pentafluoropropyl ethyl carbonate, bis(2,2,2-trifluoroethyl) carbonate, bis(2-fluoroethyl) carbonate, trifluoromethyl carbonate Or at least one of ethylene bisfluorocarbonate.
  • the content of the fluorocarbonate is 0.01% to 20%.
  • the fluorocarboxylic acid ester includes acetyl hypofluorite, 2-fluoroethyl fluoroacetate, ethyl fluorohexanoate, methyl fluoroacetate, ethyl fluoroacetate, butyl fluoroacetate Ester, 2,2,2-trifluoroethyl trifluoroacetic acid, 2-fluoroethyl 5-fluorohexanoic acid, 2,2,2-trifluoroethyl difluoroacetic acid, 2,2-di Fluoroethyl trifluoroacetate, 2-fluoroethyl 4-fluorobutyrate, ethyl trifluoropropionate, ethyl 2-fluoropropionate, ethyl 2,2-difluoroacetate, difluoropropionic acid At least one of ethyl ester, methyl difluoroacetate, or methyl 2-fluoroacetic acid, methyl
  • the content of the fluorocarboxylic acid ester is 0.01% to 30%.
  • the sulfur-containing additives include 1,3-butanesulfide, vinyl sulfate, 1,3-propane sultone, 1,3-propanediol cyclic sulfate, 2,4-butane sultone Esters, 1,3-butane sultone, 1-methyl-1,3-propane sultone, 2-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone At least one of lactone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, or 3-fluoro-1,3-propane sultone.
  • the content of the sulfur-containing additive is 0.01% to 10%.
  • the nitrile-containing additive includes at least one of the following compounds:
  • M is selected from C and Si;
  • R 51 , R 61 , R 62 , R 63 are each independently selected from substituted or unsubstituted C 1 -C 12 alkylene, substituted or unsubstituted C 2 -C 12 alkenylene, R 0 -SR group or R 0 -OR group, wherein R 0 and R are each independently selected from substituted or unsubstituted C 1 -C 6 alkylene, wherein when substituted, the substituent is selected from halogen;
  • R 64 is selected from H, substituted or unsubstituted C 1 -C 12 alkylene, substituted or unsubstituted C 2 -C 12 alkenylene, R 0 -SR group or R 0 -OR A group, wherein R 0 and R are each independently selected from substituted or unsubstituted C 1 -C 6 alkylene, wherein when substituted, the substituent is selected from halogen.
  • the nitrile-containing additives include adiponitrile, succinonitrile, glutaronitrile, malononitrile, 2-methylglutaronitrile, pimelonitrile, sebaconitrile, azelaonitrile, 1,4-dicyano-2-butene, ethylene glycol bis(propionitrile) ether, 3,3'-oxydipropionitrile, thiomalononitrile, hex-2-ene dinitrile, butene dinitrile Nitrile, 2-pentanedionitrile, ethyl succinonitrile, hex-3-enedionitrile, 2-methylene glutaronitrile, 4-cyanopimenitrile, 1,3,6-hexanetricarbonitrile , At least one of 1,3,5-hexanetricarbonitrile, 1,2,3-propanetricarbonitrile, or 1,2,3-tris(2-cyanooxy)propane.
  • the content of the nitrile-containing additive is 0.01% to 10%.
  • the lithium salt additives include lithium bis(trifluoromethanesulfonimide), lithium bis(fluorosulfonyl)imide, lithium bisoxalate, lithium tetrafluorophosphate, lithium difluorooxalate, At least one of lithium hexafluorocesium oxide or lithium difluorophosphate.
  • the content of the lithium salt additive is 0.01% to 5%.
  • the anode active material layer contains a metal element
  • the metal element includes at least one of Co, Mn, Ni, Al, or Cu.
  • the content of the metal element is 200 ppm or less.
  • the term "about” is used to describe and illustrate small changes.
  • the term may refer to an example in which the event or situation occurs precisely and an example in which the event or situation occurs very closely.
  • the term can refer to a range of variation less than or equal to ⁇ 10wt% of the stated value, such as less than or equal to ⁇ 5wt%, less than or equal to ⁇ 4wt%, less than or equal to ⁇ 3wt%, 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%.
  • alkyl encompasses straight and branched chain alkyl groups.
  • the alkyl group may be C 1 -C 50 alkyl, C 1 -C 40 alkyl, C 1 -C 30 alkyl, C 1 -C 20 alkyl, C 1 -C 12 alkyl, C 1 -C 10 alkyl group, C 1 -C 6 alkyl group, C 2 -C 6 alkyl group, C 2 -C 5 alkyl group.
  • the alkyl group includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, and the like.
  • the alkyl group may be optionally substituted.
  • alkenyl encompasses straight and branched chain alkenyl groups.
  • the alkenyl group may be C 2 -C 50 alkenyl, C 2 -C 40 alkenyl, C 2 -C 30 alkenyl, C 2 -C 20 alkenyl, C 2 -C 12 alkenyl, C 2 -C 10 alkenyl, C 2 -C 6 alkenyl.
  • alkenyl groups may be optionally substituted.
  • aryl encompasses both monocyclic and polycyclic ring systems.
  • a polycyclic ring may have two or more rings in which two carbons are shared by two adjacent rings (the rings are "fused"), wherein at least one of the rings is aromatic, such as others
  • the ring can be a cycloalkyl, cycloalkenyl, aryl, heterocyclic, and/or heteroaryl group.
  • the aryl group may be a C 6 -C 50 aryl group, a C 6 -C 40 aryl group, a C 6 -C 30 aryl group, a C 6 -C 20 aryl group, or a C 6 -C 10 aryl group.
  • aryl groups may be optionally substituted.
  • hydrocarbyloxy is an organic group having -OR, where R is a straight or branched chain hydrocarbyl group.
  • R may be a C 1 -C 50 hydrocarbyl group, a C 1 -C 40 hydrocarbyl group, a C 1 -C 30 hydrocarbyl group, a C 1 -C 20 hydrocarbyl group, a C 1 -C 12 hydrocarbyl group, a C 1 -C 10 hydrocarbyl group, a C 1- C 6 hydrocarbon group, C 2 -C 6 hydrocarbon group, C 2 -C 5 hydrocarbon group.
  • the hydrocarbyl group may include an alkyl group, an alkenyl group, an alkynyl group, or an aryl group.
  • the hydrocarbyloxy group may be optionally substituted.
  • alkylene encompasses straight and branched chain alkylenes.
  • the alkylene group may be a C 1 -C 50 alkylene group, a C 1 -C 40 alkylene group, a C 1 -C 30 alkylene group, a C 1 -C 20 alkylene group, a C 1 -C 10 alkylene group Group, C 1 -C 6 alkylene, C 2 -C 6 alkylene, C 2 -C 5 alkylene.
  • the alkylene group may be optionally substituted.
  • alkenylene encompasses straight chain and branched chain alkenylene groups.
  • the alkenylene group may be C 2 -C 50 alkenylene, C 2 -C 40 alkenylene, C 2 -C 30 alkenylene, C 2 -C 20 alkenylene, C 2 -C 10 alkenylene Group, C 1 -C 6 alkenylene, C 2 -C 6 alkenylene.
  • alkenylene groups may be optionally substituted.
  • the substituents can be independently selected from a silyl group, a siloxane group, an amino group, an ether group, an ester group, a carboxyl group, a sulfonic acid group, a mercapto group, a cyano group, a halogen group, or a combination thereof.
  • This application relates to an electrochemical device, which includes: a positive electrode; a negative electrode; and an electrolyte.
  • the positive electrode of the present application may include a positive electrode current collector and a positive electrode active material layer.
  • the positive electrode active material layer is disposed on the positive electrode current collector.
  • the positive active material layer includes a positive active material.
  • the cathode active material of the present application can reversibly insert and extract lithium ions.
  • the specific types of positive electrode active materials are not subject to specific restrictions, and can be selected according to requirements.
  • the positive electrode active material may include lithium and at least one active metal, for example including, but not limited to, 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).
  • the positive active material may include, but is not limited to, lithium cobaltate, lithium iron phosphate, lithium iron manganese phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadyl phosphate, vanadium phosphate At least one of sodium oxide, 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, it includes, but is not limited to, aluminum foil or nickel foil.
  • the positive active material layer may further include a binder and/or a conductive agent.
  • the binder can not only improve the bond between the particles of the positive electrode active material, but also enhance the bond between the positive electrode active material and the positive electrode current collector.
  • the binder may include, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-containing Oxygen-based polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylic (ester) styrene butadiene rubber, epoxy resin , At least one of nylon.
  • the conductive agent can be used to enhance the conductivity of the electrode.
  • This application can use any conductive material as the conductive agent, as long as the conductive material does not cause unwanted chemical changes.
  • the conductive material may include, but is not limited to, carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal Powders, metal fibers, etc., including, for example, at least one of copper, nickel, aluminum, silver, etc.), conductive polymers (for example, polyphenylene derivatives), and mixtures thereof.
  • carbon-based materials e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.
  • metal-based materials e.g., metal Powders, metal fibers, etc., including, for example, at least one of copper, nickel, aluminum, silver, etc.
  • 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.
  • the negative active material layer is disposed on the negative current collector.
  • the negative active material layer includes a negative active material.
  • the negative active material of the present application can reversibly insert and extract lithium ions.
  • the specific types of negative electrode active materials are not subject to specific restrictions, and can be selected according to requirements.
  • the negative active material may include or be selected from one or more of the following materials: carbonaceous materials, siliceous materials, alloy-based materials, and lithium-containing metal composite oxide materials.
  • the carbonaceous material may include, but is not limited to, crystalline carbon, amorphous carbon, and mixtures thereof.
  • the crystalline carbon may be amorphous or flake-shaped, flake-shaped, spherical or fibrous natural graphite or artificial graphite.
  • Amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, and the like.
  • the negative electrode active material may include, but is not limited to, natural graphite, artificial graphite, mesophase carbon microspheres (referred to as MCMB for short), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn At least one of alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , spinel structure lithiated TiO 2 -Li 4 Ti 5 O 12 , and Li-Al alloy.
  • the negative electrode current collector may be a negative electrode current collector commonly used in the art.
  • the negative electrode current collector includes, but is not limited to, copper foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, polymer substrate coated with conductive metal, and combinations thereof.
  • the negative active material layer may further include a binder and/or a conductive agent.
  • the binder and the conductive agent can use the materials disclosed in the foregoing positive electrode, and will not be repeated here.
  • the electrolyte of the present application can be divided into water-based electrolyte and non-aqueous electrolyte. Compared with water-based electrolyte, electrochemical devices using non-aqueous electrolyte can work under a wider voltage window to achieve higher energy. density.
  • the non-aqueous electrolyte may include an organic solvent.
  • the organic solvent can be any organic solvent known in the prior art that can be used as a solvent for the electrolyte.
  • the organic solvent of the present application includes or is selected from: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC) at least one.
  • the electrochemical device has excellent cycle stability, and at the same time has excellent low-temperature discharge performance and high-temperature storage performance:
  • n is an integer in the range of 0-5;
  • R 1 is selected from a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted hydrocarbyloxy group, and when substituted,
  • the substituents are independently selected from a silyl group, a siloxane group, an amino group, an ether group, an ester group, a carboxyl group, a sulfonic acid group, a mercapto group, a cyano group, a halogen group, or a combination thereof.
  • R 1 is selected from substituted or unsubstituted C 1 -C 12 alkyl, substituted or unsubstituted C 2 -C 12 alkenyl, substituted or unsubstituted C 6- A C 20 aryl group or a substituted or unsubstituted C 1 -C 12 hydrocarbyloxy group.
  • R 1 is selected from substituted or unsubstituted C 1 -C 10 alkyl, substituted or unsubstituted C 2 -C 10 alkenyl, substituted or unsubstituted C 6- A C 10 aryl group or a substituted or unsubstituted C 1 -C 10 hydrocarbyloxy group.
  • the anion represented by formula I of the present application can not only promote the rapid transport of lithium ions at the interface between the positive electrode and the electrolyte, thereby improving the discharge performance of the electrochemical device at low temperatures. ; And it helps to form a stable passivation film on the surface of the positive electrode, thereby improving the cycle stability of the electrochemical device during the charge and discharge process and reducing the degree of gas expansion under high temperature storage conditions to improve the high temperature storage of the electrochemical device performance.
  • the anion represented by formula I described in this application includes or is selected from one or more of the following anions, but is not limited thereto:
  • the range of the mass percentage of the anion represented by Formula I is: 0.001 wt% to 7 wt%, 0.01 wt% to 5 wt%, 0.1 wt% to 3 wt% % Or 0.1wt% to 2wt%. In some embodiments, based on the total weight of the electrolyte, the mass percentage of the anion represented by Formula I is any value in the above range.
  • the mass percentage of the anion represented by the formula I is about 0.001% by weight, about 0.01% by weight, about 0.1% by weight, about 1% by weight, about 2% by weight, about 3% by weight, about 4% by weight, about 5% by weight, About 6wt% or about 7wt%.
  • the anion represented by Formula I of the present application forms a lithium salt with lithium ions, and is added to the electrolyte in the form of a lithium salt.
  • the anion represented by Formula I of the present application may be a decomposition product of 1-propyl phosphoric anhydride, 1-acetonitrile phosphoric anhydride, and 1-ethyl phosphoric anhydride.
  • the electrolyte of the present application optionally further includes one or more of fluorocarbonate, fluorocarboxylate, sulfur-containing additives, nitrile-containing additives, and lithium salt additives to combine the formula
  • fluorocarbonate fluorocarbonate
  • fluorocarboxylate sulfur-containing additives
  • nitrile-containing additives sulfur-containing additives
  • lithium salt additives lithium salt additives
  • the electrolyte of the present application further includes fluorocarbonate.
  • the fluorocarbonate combined with the anion of the formula I in the electrolyte can simultaneously take into account the rapid transmission of lithium ions at the interface between the positive and negative electrodes and the stability of the positive and negative electrodes during charge and discharge, thereby improving the cycle performance of the electrochemical device And low temperature discharge performance.
  • the fluorocarbonate includes or is selected from 3,3,3-trifluoropropylene carbonate, fluoroethylene carbonate, 2,2,3,3-tetrafluoropropyl methyl carbonate, 2,2,3,3,3-pentafluoropropyl ethyl carbonate, bis(2,2,2-trifluoroethyl) carbonate, bis(2-fluoroethyl) carbonate, trifluoromethyl carbonate At least one of ester or ethylene bisfluorocarbonate.
  • the content of the fluorocarbonate is 0.01 wt% to 40 wt%, 0.01 wt% to 30 wt%, 0.01 wt% to 20 wt%, 0.01 wt% to 10 wt% %, 0.01wt% to 5wt%, 0.1wt% to 40wt%, 0.1wt% to 30wt%, 0.1wt% to 20wt%, 0.1wt% to 10wt%, 0.1wt% to 5wt%, 1wt% to 40wt%, 1 wt% to 30 wt%, 1 wt% to 20 wt%, 1 wt% to 10 wt%, or 1 wt% to 5 wt%.
  • the electrolyte solution of the present application further includes fluorocarboxylic acid ester.
  • the interaction of the fluorocarboxylic acid ester with the anion of formula I can further improve the high temperature storage performance.
  • the detailed mechanism of this effect is not clear, it can be considered as follows: the interaction of the fluorocarboxylic acid ester and the anion of formula I improves the oxidation resistance of the electrolyte, which can effectively reduce the degree of oxidation of the positive electrode active material to the electrolyte.
  • a composite SEI film can be formed on the surface of the positive electrode to enhance the protection of the positive electrode.
  • the fluorocarboxylic acid ester includes or is selected from acetyl hypofluorite, 2-fluoroethyl fluoroacetate, ethyl fluorohexanoate, methyl fluoroacetate, ethyl fluoroacetate, fluoroacetate Butyl acetate, 2,2,2-trifluoroethyl trifluoroacetic acid, 2-fluoroethyl 5-fluorohexanoic acid, 2,2,2-trifluoroethyl difluoroacetic acid, 2,2 -Difluoroethyl trifluoroacetate, 2-fluoroethyl 4-fluorobutyrate, ethyl trifluoropropionate, ethyl 2-fluoropropionate, ethyl 2,2-difluoroacetate, difluoro At least one of ethyl propionate, methyl difluoroacetate, or methyl 2-fluoro a
  • the content of the fluorocarboxylic acid ester is 0.01 wt% to 50 wt%, 0.01 wt% to 40 wt%, 0.01 wt% to 30 wt%, 0.01 wt% to 20wt%, 0.01wt% to 10wt%, 0.01wt% to 5wt%, 0.1wt% to 50wt%, 0.1wt% to 40wt%, 0.1wt% to 30wt%, 0.1wt% to 20wt%, 0.1wt% to 10wt% %, 0.1wt% to 5wt%, 1wt% to 50wt%, 1wt% to 40wt%, 1wt% to 30wt%, 1wt% to 20wt%, 1wt% to 10wt%, or 1wt% to 5wt%.
  • the electrolyte of the present application further includes sulfur-containing additives.
  • sulfur-containing additives can also form a stable SEI film on the surface of the positive electrode to protect the positive electrode.
  • the sulfur-containing additive can form a composite protective film on the surface of the positive electrode, which further strengthens the protection of the positive electrode and improves the stability of the electrochemical device.
  • the sulfur-containing additives include 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 At least one of ester, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, or 3-fluoro-1,3-propane sultone.
  • the content of the sulfur-containing additive is 0.01 wt% to 20 wt%, 0.01 wt% to 10 wt%, 0.01 wt% to 5 wt%, 0.1 wt% to 20 wt% , 0.1wt% to 10wt%, 0.1wt% to 5wt%, 1wt% to 20wt%, 1wt% to 10wt%, or 1wt% to 5wt%.
  • the electrolyte of the present application further includes a nitrile-containing additive.
  • the nitrile-containing additive contains a cyano (-CN) functional group.
  • the nitrile-containing additive and the anion represented by formula I can form an excellent nitrile protective film on the surface of the positive electrode, stabilize the active metal in the positive electrode active material, inhibit the dissolution of the active metal, and improve the cycle performance of the electrochemical device .
  • the nitrile-containing additive includes at least one of the following compounds:
  • the element M can be selected from one of C and Si;
  • R 51 , R 61 , R 62 , R 63 are each independently selected from substituted or unsubstituted C 1 -C 12 alkylene, substituted or unsubstituted C 2 -C 12 alkenylene, R 0 -SR group or R 0 -OR group, wherein R 0 and R are each independently selected from substituted or unsubstituted C 1 -C 6 alkylene, wherein when substituted, the substituent is selected from halogen;
  • R 64 is selected from H, substituted or unsubstituted C 1 -C 12 alkylene, substituted or unsubstituted C 2 -C 12 alkenylene, R 0 -SR group or R 0 -OR A group, wherein R 0 and R are each independently selected from substituted or unsubstituted C 1 -C 6 alkylene, wherein when substituted, the substituent is selected from halogen.
  • the nitrile-containing additives include adiponitrile, succinonitrile, glutaronitrile, malononitrile, 2-methylglutaronitrile, pimelic nitrile, sebaconitrile, azelaonitrile, 1, 4-Dicyano-2-butene, ethylene glycol bis(propionitrile) ether, 3,3'-oxydipropionitrile, thiomalononitrile, hex-2-ene dinitrile, butenedionitrile, 2-Pentene dinitrile, ethyl succinonitrile, hex-3-ene dinitrile, 2-methylene glutaronitrile, 4-cyanopimelonitrile, 1,3,6-hexanetricarbonitrile, 1 , At least one of 3,5-hexanetricarbonitrile, 1,2,3-propanetricarbonitrile, or 1,2,3-tris(2-cyanooxy)propane.
  • the protective effect of nitrile-containing additives has a certain correlation with its dosage.
  • the content of the nitrile-containing additive is 0.01 wt% to 20 wt%, 0.01 wt% to 10 wt%, 0.1 wt% to 20 wt%, 0.1 wt% to 10 wt% , 1wt% to 20wt% or 1wt% to 10wt%.
  • the electrolyte of the present application may further include a lithium salt additive capable of increasing the LiF component in the SEI film, thereby achieving the effect of improving the cycle stability of the electrochemical device.
  • the lithium salt additive includes or is selected from lithium bistrifluoromethanesulfonimide LiN(CF 3 SO 2 ) 2 (LiTFSI for short), lithium bis(fluorosulfonyl)imide Li(N (SO 2 F) 2 ) (LiFSI in abbreviation), LiB(C 2 O 4 ) 2 (LiBOB in abbreviation), lithium tetrafluorophosphate oxalate (LiPF 4 C 2 O 2 ), lithium difluorooxalate borate At least one of LiBF 2 (C 2 O 4 ) (abbreviated as LiDFOB), lithium hexafluorocesium oxide (LiCsF 6 ), or lithium difluorophosphate (LiPO 2 F 2 ).
  • LiDFOB LiBF 2
  • LiCsF 6 lithium hexafluorocesium oxide
  • LiPO 2 F 2 lithium difluorophosphate
  • the content of the lithium salt additive is 0.01 wt% to 20 wt%, 0.01 wt% to 10 wt%, 0.01 wt% to 5 wt%, 0.01 wt% to 3 wt% , 0.1wt% to 20wt%, 0.1wt% to 10wt%, 0.1wt% to 5wt%, 0.1wt% to 3wt%, 1wt% to 20wt%, 1wt% to 10wt%, 1wt% to 5wt% or 1wt% to 3wt%.
  • the surface of the negative active material layer of the electrochemical device contains a trace amount of metal elements.
  • the above-mentioned metal elements are distributed on the surface of the negative electrode active material layer. For example, based on the negative electrode surface (the side away from the negative electrode current collector), the distribution depth of the above-mentioned metal elements is not greater than 5 mm.
  • Part of the metal on the surface of the negative electrode active material layer is derived from the metal elements in the positive electrode active material, and part is derived from the electrolyte system. For example, after the electrolyte is injected, the metal elements distributed on the surface of the negative electrode active material layer can be adjusted by adjusting the high-temperature baking time of the electrolyte and the water content in the dry battery.
  • the electrolyte will chemically react with the positive electrode active material to a certain extent, so that the metal in the positive electrode active material is dissolved in the electrolyte in the form of ions.
  • the dissolved metal ions are reduced and deposited on the surface of the negative electrode active material layer of the electrochemical device.
  • the metal elements may include or be selected from 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 ( At least one of Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), lanthanum (La), and zirconium (Zr).
  • the anion represented by formula I contained in the electrolyte helps to form a strong and stable SEI film on the surface of the positive electrode to protect the positive electrode active material, it is dissolved from the positive electrode active material and distributed to the negative electrode.
  • the metal elements on the surface are usually trace amounts.
  • the content of metal ions added to the electrolyte is also very small. In some embodiments, based on the total weight of the negative active material layer, the content of the metal element ranges below about 200 ppm.
  • the trace metal elements distributed on the surface of the negative electrode will enhance the conductivity of the negative electrode surface to a certain extent, which is conducive to the rapid transmission of electrons and lithium ions, thereby improving the rate characteristics and low-temperature discharge performance of the electrochemical device.
  • the electrochemical device of the present application further includes a separator film disposed between the positive electrode and the negative electrode to prevent short circuits.
  • the present application does not particularly limit the material and shape of the isolation membrane used in the electrochemical device, and it can be any material and shape disclosed in the prior art.
  • the isolation membrane includes a polymer or an inorganic substance formed of a material that is stable to the electrolyte of the present application.
  • the isolation film may include a substrate layer and a surface treatment layer.
  • the substrate layer is a non-woven fabric, film or 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.
  • a polyethylene porous film, a polypropylene porous film, a polyethylene non-woven fabric, a polypropylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be selected.
  • the surface treatment layer may be, but is not limited to, a polymer layer, an inorganic substance layer, or a mixed layer formed of a polymer and an inorganic substance.
  • the inorganic layer may include inorganic particles and a binder.
  • Inorganic particles may include or be selected from aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehm
  • the binder may include or be selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, poly One or a combination of vinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
  • the polymer layer may include a polymer.
  • the material of the polymer may include or be selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, poly(vinylidene fluoride- At least one of hexafluoropropylene).
  • the electrochemical device of the present application may be a lithium ion battery or any other suitable electrochemical device.
  • the electrochemical device in the embodiments of the present application includes any device that undergoes an electrochemical reaction, and specific examples thereof include all kinds of primary batteries, secondary batteries, solar cells, or capacitors.
  • 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 can be used for any purpose known in the prior art. According to some embodiments of the present application, the electrochemical device of the present application can be used in electronic devices, where electronic devices include, but are not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable phones, and portable faxes.
  • Printers Portable copiers, portable printers, stereo headsets, video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, spares Power supplies, motors, automobiles, motorcycles, power-assisted bicycles, bicycles, lighting equipment, toys, game consoles, clocks, electric tools, flashlights, cameras, large household storage batteries, lithium-ion capacitors, etc.
  • the positive electrode active material lithium cobalt oxide (LiCoO 2 ), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) in an appropriate amount of N-methyl at a weight ratio of 96:2:2 Pyrrolidone (NMP) solvent is fully stirred and mixed to form a uniform positive electrode slurry; then the positive electrode slurry is coated on the positive electrode current collector aluminum foil, dried and cold pressed to obtain the positive electrode active material layer, and then cut into pieces , Weld the tabs to obtain the positive electrode.
  • NMP Pyrrolidone
  • the negative electrode active material graphite, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are fully mixed in an appropriate amount of deionized water at a weight ratio of 97:2:1 Stir and mix to form a uniform negative electrode slurry; then coat the negative electrode slurry on the copper foil of the negative electrode current collector, dry and cold press to obtain the negative electrode active material layer, and then cut and weld the tabs to obtain negative electrode.
  • Preparation of lithium ion battery stack the positive electrode, separator film, and negative electrode in order, so that the separator film is between the positive electrode and the negative electrode for isolation, and then wound, placed in the outer packaging foil to dry, and inject the above
  • the prepared electrolyte undergoes vacuum packaging, standing, forming, shaping and other processes to complete the preparation of the lithium ion battery.
  • the lithium-ion battery was charged to 4.45V at a current of 0.5C, and then charged to 0.05C at a constant voltage at a voltage of 4.45V. After that, place the lithium ion battery at a temperature of -20°C and stand still for 30 minutes to keep the temperature of the lithium ion battery consistent with the outside temperature. Discharge to 3.0V at a current of 0.2C under the condition of -20°C, and record the discharge capacity as C2 at this time.
  • the low-temperature discharge performance of the lithium-ion battery is measured by the following formula to calculate the discharge percentage of the lithium-ion battery at -20°C: (C2/C1) ⁇ 100%.
  • the lithium ion battery was discharged to 3.0V at a current of 0.5C at 25°C, and left to stand for 5 minutes. Then charge to 4.45V with a current of 0.5C, and then charge to 0.05C at a constant voltage at a voltage of 4.45V.
  • Use a PPG soft-pack battery thickness gauge to test the thickness of the lithium-ion battery when fully charged, and record it as a. Place the lithium-ion battery in an oven at 80°C for 8 hours, test the thickness after 8 hours, and record it as b.
  • the following formula is used to calculate the thickness expansion rate of the lithium-ion battery at 80°C to measure the high-temperature storage performance of the lithium-ion battery: (b-a)/a ⁇ 100%.
  • the lithium ion battery was discharged to 3.0V at a current of 0.5C at 25°C, and left to stand for 5 minutes. Then charge to 4.45V at a current of 0.5C, and then charge to 0.05C at a constant voltage at a voltage of 4.45V; after charging, discharge to 3.0V at a current of 0.5C, which is a charge-discharge cycle (ie, cycle one lock up).
  • cycle 800 cycles at 25°C.
  • the discharge capacity of the first cycle is recorded as C1
  • the discharge capacity of the 800th cycle is recorded as C800.
  • the cycle capacity retention rate of the lithium ion battery at 25°C is calculated by the following formula to measure the cycle performance of the lithium ion battery: (C800/C1) ⁇ 100%.
  • the lithium ion battery was discharged to 3.0V at a current of 0.5C at 45°C, and left to stand for 5 minutes. Then charge to 4.45V at a current of 0.5C, and then charge to 0.05C at a constant voltage at a voltage of 4.45V; after charging, discharge to 3.0V at a current of 0.5C, which is a charge-discharge cycle (ie, cycle one lock up).
  • cycle 500 cycles at 45°C where the discharge capacity of the first cycle is recorded as C1, and the discharge capacity of the 500th cycle is recorded as C500.
  • the cycle capacity retention rate of the lithium ion battery at 45°C is calculated by the following formula to measure the cycle performance of the lithium ion battery at high temperature: (C500/C1) ⁇ 100%.
  • DMC dimethyl carbonate
  • the electrolytes and lithium-ion batteries of Examples 1-19 and Comparative Example 1 were prepared according to the above-mentioned preparation method.
  • Comparative Example 1 used the basic electrolyte, and Examples 1-19 were added to the basic electrolyte as shown in Table 1.
  • the components and contents shown are the mass percentages of the components based on the total weight of the electrolyte, and the substances of formula I-2, I-3, I-4, and I-7 are added in the form of lithium salts.
  • Table 1 also shows the electrochemical test results of the lithium ion batteries in Examples 1-19 and Comparative Example 1.
  • the electrolyte in Examples 1-19 of the present application contains a certain amount of the anion of Formula I described in the present application, which corresponds to the obtained electricity.
  • the discharge performance of the chemical device at low temperature and the storage performance at high temperature have been significantly improved. That is, by introducing the anion of Formula I in the electrolyte, the obtained electrochemical device has excellent electrochemical performance no matter in a low temperature environment or a high temperature condition.
  • anion represented by formula I helps to form a strong and stable SEI film on the surface of the positive electrode, which can protect the positive electrode active material and the positive electrode well, making the electrochemical device even at 80 Long-term storage at a high temperature of °C will not cause serious gas expansion.
  • Examples 20-26 are improvements based on Example 5. Specifically, in Examples 20-26, fluorocarbonate is further added to the electrolyte described in Example 5. For the specific components and content added and the performance test results of the resulting lithium ion battery, please refer to the following table 2.
  • the electrolytes in Examples 20-26 of the present application contain a certain content of fluorocarbonate, which corresponds to the electrochemical device obtained at low temperature. Both the discharge performance and the cycle stability at room temperature have been improved to a certain extent. This is because the anion represented by formula I and the fluorocarbonate work together to make the electrolyte have a higher reduction potential, and the SEI film can be formed on the surface of the negative electrode in advance to protect the negative electrode active material, thereby improving the cycle performance of the electrochemical device .
  • the formation of the SEI film helps to reduce the reverse generation of side reactions at the negative electrode interface, thereby suppressing the increase in impedance caused by the accumulation of by-products generated by the side reactions on the electrode surface, and promoting the rapid acceleration of lithium ions at the negative electrode interface. Transmission, which can improve the discharge performance of the electrochemical device at low temperatures.
  • Examples 27-33 are improvements based on Example 5. Specifically, in Examples 27-33, the fluorocarboxylic acid ester was further added to the electrolyte described in Example 5. For the specific components and content added and the performance test results of the resulting lithium ion battery, please refer to the following table 3.
  • the electrolytes in Examples 27-33 of the present application contain a certain content of fluorocarboxylic acid esters, and the corresponding electrochemical devices obtained are in The degree of expansion experienced by storage at a high temperature of 80°C for 8 hours will be further reduced.
  • the anion represented by formula I and the fluorocarboxylic acid ester work together to improve the oxidation resistance of the electrolyte, which can effectively resist the oxidation of the positive electrode active material and reduce the occurrence of gas generation; at the same time, it can be formed on the surface of the positive electrode.
  • the composite SEI film further strengthens the protection of the positive electrode, thereby further suppressing the occurrence of gas expansion.
  • Examples 34-41 are improvements based on Example 5. Specifically, in Examples 34-41, sulfur-containing additives are further added to the electrolyte described in Example 5. For the specific components and contents added and the performance test results of the resulting lithium ion battery, please refer to the following Table 4 .
  • the electrolytes in Examples 34-41 of the present application contain a certain amount of sulfur-containing additives, which corresponds to the electrochemical device obtained at 80°C.
  • the degree of expansion experienced by storage for 8 hours at a high temperature will be further reduced.
  • the sulfur-containing additives can also form a stable SEI film on the surface of the positive electrode, and cooperate with the anion shown in formula I of the present application to form a composite protective film on the surface of the positive electrode to further strengthen the protection of the positive electrode, thereby further Suppress the occurrence of gas expansion.
  • Examples 42-63 are improvements based on Example 5. Specifically, in Examples 42-63, the electrolyte described in Example 5 was further added with nitrile-containing additives. For the specific components and contents added, and the performance test results of the resulting lithium ion battery, please refer to the following Table 5. .
  • the electrolytes in Examples 42-63 of the present application contain a certain amount of nitrile-containing additives, which corresponds to the electrochemical device obtained at 45°C.
  • the cycle performance at higher temperatures has been further improved.
  • the nitrile-containing additive can form an excellent nitrile protective film on the surface of the positive electrode and improve the stability of the positive electrode material during charge and discharge.
  • the nitrile-containing additive can well stabilize the active metal in the positive electrode active material, inhibit the dissolution of the active metal, and improve the cycle performance of the electrochemical device.
  • Examples 64-73 are improvements based on Example 5. Specifically, in Examples 64-73, a lithium salt additive was further added to the electrolyte described in Example 5. For the specific components and content added and the performance test results of the resulting lithium ion battery, please refer to the following Table 6. .
  • Example 6 Referring to the electrochemical test results in Table 6, it can be seen that compared with Example 5, the discharge performance of the electrochemical devices in Examples 64-73 of the present application at low temperature is slightly deteriorated, but their cycling performance at higher temperatures Stability has been 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.
  • Examples 74-78 are improvements based on Example 5. Specifically, the water content of the battery before the electrolyte injection was controlled to be 80 ppm, 100 ppm, 140 ppm, 200 ppm, 240 ppm, and 270 ppm through the high temperature baking time to obtain Example 5 and Examples 74-78 of Table 7, respectively. Compared with Example 5, there is a certain content of metallic cobalt on the surface of the negative electrode of Examples 74-78 at a depth not greater than 10 ⁇ m. For specific content and performance test results of the obtained lithium ion battery, please refer to Table 7 below.
  • Example 7 Referring to the electrochemical test results in Table 7, it can be seen that compared with Example 5, the surface of the anode in Examples 74-78 of the present application has more cobalt distributed on the surface, which corresponds to the electrochemical device obtained at low temperature. The discharge performance has been further improved. This is because the metal elements distributed on the surface of the negative electrode will enhance the conductivity of the negative electrode surface to a certain extent, which is conducive to the rapid transmission of electrons and lithium ions, thereby improving the low-temperature discharge performance of the electrochemical device.
  • Examples 79-84 were added with sulfur-containing additives, fluorocarboxylic acid esters, nitrile additives or a combination thereof on the basis of Example 21, the specific components and contents added therein, and the performance test results of the resulting lithium ion battery Please refer to the following Table 8-1 and Table 8-2.
  • references to “embodiments”, “parts of embodiments”, “one embodiment”, “another example”, “examples”, “specific examples” or “partial examples” throughout the specification mean that At least one embodiment or example in this application includes the specific feature, structure, material, or characteristic described in the embodiment or example. Therefore, descriptions appearing in various places throughout the specification, such as: “in some embodiments”, “in embodiments”, “in one embodiment”, “in another example”, “in an example “In”, “in a specific example” or “exemplary”, which are not necessarily quoting the same embodiment or example in this application.
  • the specific features, structures, materials or characteristics herein can be combined in one or more embodiments or examples in any suitable manner.

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Abstract

一种电化学装置，包含正极、负极和电解液，其中电解液包含具有特定结构的磷酸酐官能团的阴离子。通过在电解液中添加上述阴离子，可以同时改善并兼顾电化学装置的低温放电性能和高温存储性能，并且改善电化学装置在常温和高温下的循环稳定性。

Description

电化学装置及包含其的电子装置 技术领域
本申请涉及储能技术领域，更具体地，涉及一种电化学装置及包含其的电子装置。
背景技术
随着智能产品的普及和应用，人们对手机、笔记本电脑、相机等电子产品的需求逐年增加，而电化学装置作为电子产品的电源在我们日常生活中扮演着越来越重要的角色。其中，锂离子电池凭借其具有比能量大、工作电压高、自放电率低、体积小、重量轻等优势而在消费电子领域中广泛应用。
然而，随着电化学装置在电动汽车、可移动电子设备和无人机中的广泛应用，人们不仅要求电化学装置在常温环境下能够正常工作，还要求电化学装置在恶劣环境下也能够安全使用。例如，如何确保电化学装置在极端低温条件下能够正常使用而不会导致电子产品瞬间断电，如何降低电化学装置在高温条件下发生鼓胀的风险从而确保电子产品在高温环境下的安全使用，以及如何使电化学装置能够实现大倍率充放电等问题急需得到解决。此外，现有技术在致力于确保低温环境下电化学装置正常使用的同时，是无法兼顾到电化学装置在高温环境下的电化学性能的。因此，如何使得电化学装置在高温和低温的环境下均兼顾有优异的电化学性能也是人们需要考虑和解决的一个问题。
发明内容
至少为了解决上述问题，本申请在电化学装置的电解液中引入了具有磷酸酐官能团的阴离子。首先，通过利用磷酸酐官能团中磷氧双键(P＝O键)的富电子特性，能够促使锂离子的快速传输，从而改善电化学装置的倍率性能以及其在低温下的放电性能。其次，通过利用磷酸酐官能团的桥联结构和阴离子所带的负电荷，有助于在正极定向形成保护膜，从而改善电化学装置的循环稳定性和高温存储性能。
根据本申请的一个层面，本申请提供一种电化学装置，包括：正极，所述正极包括正极集流体和正极活性材料层，所述正极活性材料层包含正极活性材料；负极，所述负极包括负极集流体和负极活性材料层，所述负极活性材料层包含负极活性材料；和电解液，所述电解液包括锂离子和式I表示的阴离子：
Figure PCTCN2020079264-appb-000001
其中，n为0-5范围内的整数；
R 1选自经取代或未经取代的C 1-C 12烷基、经取代或未经取代的C 2-C 12烯基、经取代或未经取代的C 6-C 20芳基、经取代或未经取代的C 1-C 12烃氧基，其中经取代时，所述取代基独立地选自硅烷基、硅氧烷基、氨基、醚基、酯基、羧基、磺酸基、巯基、氰基、卤素或其组合。
根据本申请的实施例，其中所述式I表示的阴离子包含：
Figure PCTCN2020079264-appb-000002
Figure PCTCN2020079264-appb-000003
Figure PCTCN2020079264-appb-000004
中的至少一种；
根据本申请的实施例，基于所述电解液的总重量，所述式I表示的阴离子的质量百分含量为0.001％至7％。
根据本申请的实施例，所述电解液中进一步包括氟代碳酸酯、氟代羧酸酯、含硫添加剂、含腈添加剂或锂盐添加剂中的一种或多种。
根据本申请的实施例，其中所述氟代碳酸酯包括3,3,3-三氟碳酸丙烯酯、氟代碳酸乙烯酯、2,2,3,3-四氟丙基碳酸甲酯、2,2,3,3,3-五氟丙基碳酸乙酯、二(2,2,2-三氟乙基)碳酸酯、二(2-氟乙基)碳酸酯、三氟甲基碳酸酯或双氟碳酸乙烯酯中的至少一种。
根据本申请的实施例，基于所述电解液的总重量，所述氟代碳酸酯的含量为0.01％至20％。
根据本申请的实施例，所述氟代羧酸酯包括乙酰基次氟酸酯、氟乙酸-2-氟乙酯、氟己酸乙酯、氟乙酸甲酯、氟乙酸乙酯、氟乙酸丁酯、三氟乙酸-2,2,2-三氟乙酯、5-氟己酸-2-氟乙酯、二氟乙酸-2,2,2-三氟乙基酯、2,2-二氟乙基三氟乙酸酯、2-氟乙基4-氟丁酸酯、三氟丙酸乙酯、2-氟丙酸乙酯、2,2-二氟乙酸乙酯、二氟丙酸乙酯、二氟乙酸甲酯或2-氟丙酸甲酯中的至少一种。
根据本申请的实施例，基于所述电解液的总重量，所述氟代羧酸酯的含量为0.01％至30％。
根据本申请的实施例，所述含硫添加剂包括1,3-丁亚基硫酸酯、硫酸乙烯酯、1,3-丙烷磺内酯、1,3-丙二醇环硫酸酯、2,4-丁磺内酯、1,3-丁磺内酯、1-甲基-1,3-丙烷磺内酯、2-甲基-1,3-丙烷磺内酯、3-甲基-1,3-丙烷磺内酯、1-氟-1,3-丙烷磺内酯、2-氟-1,3-丙烷磺内酯或3-氟-1,3-丙烷磺内酯中的至少一种。
根据本申请的实施例，基于所述电解液的总重量，所述含硫添加剂的含量 为0.01％至10％。
根据本申请的实施例，所述含腈添加剂包括以下化合物中的至少一种：
Figure PCTCN2020079264-appb-000005
其中M选自C、Si；
其中R 51、R 61、R 62、R 63各自独立地选自经取代或未经取代的C 1-C 12亚烷基、经取代或未经取代的C 2-C 12亚烯基、R 0-S-R基团或R 0-O-R基团，其中R 0、R各自独立地选自经取代或未经取代的C 1-C 6亚烷基，其中经取代时，取代基选自卤素；
其中R 64选自H、经取代或未经取代的C 1-C 12亚烷基、经取代或未经取代的C 2-C 12亚烯基、R 0-S-R基团或R 0-O-R基团，其中R 0、R各自独立地选自经取代或未经取代的C 1-C 6亚烷基，其中经取代时，取代基选自卤素。
根据本申请的实施例，其中所述含腈添加剂包括己二腈、丁二腈、戊二腈、丙二腈、2-甲基戊二腈、庚二腈、癸二腈、壬二腈、1,4-二氰基-2-丁烯、乙二醇双(丙腈)醚、3,3'-氧二丙腈、硫代丙二腈、己-2-烯二腈、丁烯二腈、2-戊烯二腈、乙基丁二腈、己-3-烯二腈、2-亚甲基戊二腈、4-氰基庚二腈、1,3,6-己烷三甲腈、1,3,5-己烷三甲腈、1,2,3-丙三甲腈或1,2,3-三(2-氰氧基)丙烷中的至少一种。
根据本申请的实施例，基于所述电解液的总重量，所述含腈添加剂的含量为0.01％至10％。
根据本申请的实施例，所述锂盐添加剂包括双三氟甲烷磺酰亚胺锂、双(氟磺酰)亚胺锂、双草酸硼酸锂、四氟磷酸草酸锂、二氟草酸硼酸锂、六氟铯酸锂或二氟磷酸锂中的至少一种。
根据本申请的实施例，基于所述电解液的总重量，所述锂盐添加剂的含量为0.01％至5％。
根据本申请的实施例，其中所述负极活性材料层含有金属元素，所述金属元素包括Co、Mn、Ni、Al或Cu中的至少一种。
根据本申请的实施例，基于所述负极活性材料层的总重量，所述金属元素的含量为200ppm以下。
具体实施方式
本申请的实施例将会被详细的描示在下文中。本申请的实施例不应该被解释为对本申请的限制。
如本申请所用，术语“包括”、“含有”和“包含”以其开放、非限制性含义使用。
术语“约”用以描述及说明小的变化。当与事件或情形结合使用时，所述术语可指代其中事件或情形精确发生的例子以及其中事件或情形极近似地发生的例子。举例来说，当结合数值使用时，术语可指代小于或等于所述数值的±10wt％的变化范围，例如小于或等于±5wt％、小于或等于±4wt％、小于或等于±3wt％、小于或等于±2wt％、小于或等于±1wt％、小于或等于±0.5wt％、小于或等于±0.1wt％、或小于或等于±0.05wt％。另外，有时在本文中以范围格式呈现量、比率和其它数值。应理解，此类范围格式是用于便利及简洁起见，且应灵活地理解，不仅包含明确地指定为范围限制的数值，而且包含涵盖于所述范围内的所有个别数值或子范围，如同明确地指定每一数值及子范围一般。
术语“烷基”涵盖直链和支链烷基。例如，烷基可为C 1-C 50烷基、C 1-C 40烷基、C 1-C 30烷基、C 1-C 20烷基、C 1-C 12烷基、C 1-C 10烷基、C 1-C 6烷基、C 2-C 6烷基、C 2-C 5烷基。在一些实施例中，烷基包括甲基、乙基、丙基、异丙基、丁基、异丁基、叔丁基、戊基、己基、庚基、辛基等。另外，烷基可以是任选地被取代的。
术语“烯基”涵盖直链和支链烯基。例如，烯基可为C 2-C 50烯基、C 2-C 40烯基、C 2-C 30烯基、C 2-C 20烯基、C 2-C 12烯基、C 2-C 10烯基、C 2-C 6烯基。另外，烯基可以是任选地被取代的。
术语“芳基”涵盖单环系统和多环系统。多环可以具有其中两个碳为两个邻接环(所述环是“稠合的”)共用的两个或更多个环，其中所述环中的至少一者是芳香族的，例如其它环可以是环烷基、环烯基、芳基、杂环和/或杂芳基。例如，芳基可为C 6-C 50芳基、C 6-C 40芳基、C 6-C 30芳基、C 6-C 20芳基或C 6-C 10芳基。另外，芳基可以是任选地被取代的。
术语“烃氧基”为具有-O-R的有机物基团，其中R为直链或支链烃基。例如，R可为C 1-C 50烃基、C 1-C 40烃基、C 1-C 30烃基、C 1-C 20烃基、C 1-C 12烃基、 C 1-C 10烃基、C 1-C 6烃基、C 2-C 6烃基、C 2-C 5烃基。例如，烃基可包括烷基、烯基、炔基或者芳基。另外，烃氧基可以是任选地被取代的。
术语“亚烷基”涵盖直链和支链亚烷基。例如，亚烷基可为C 1-C 50亚烷基、C 1-C 40亚烷基、C 1-C 30亚烷基、C 1-C 20亚烷基、C 1-C 10亚烷基、C 1-C 6亚烷基、C 2-C 6亚烷基、C 2-C 5亚烷基。另外，亚烷基可以是任选地被取代的。
术语“亚烯基”涵盖直链和支链亚烯基。例如，亚烯基可为C 2-C 50亚烯基、C 2-C 40亚烯基、C 2-C 30亚烯基、C 2-C 20亚烯基、C 2-C 10亚烯基、C 1-C 6亚烯基、C 2-C 6亚烯基。另外，亚烯基可以是任选地被取代的。
当上述基团经取代时，取代基可独立地选自由硅烷基、硅氧烷基、氨基、醚基、酯基、羧基、磺酸基、巯基、氰基、卤素或其组合。
本申请涉及一种电化学装置，其包括：正极；负极；和电解液。
在一些实施例中，本申请的正极可包括正极集流体和正极活性材料层。在一些实施例中，所述正极活性材料层设置在正极集流体上。在一些实施例中，所述正极活性材料层包含正极活性材料。
本申请的正极活性材料能够可逆地嵌入和脱出锂离子。正极活性材料的具体种类均不受到具体的限制，可根据需求进行选择。正极活性材料可包括锂和至少一种活性金属，例如包括，但不限于为包括金属锂和至少一种活性金属的复合氧化物，其中活性金属元素包括或选自以下元素中的至少一种：钴(Co)、镍(Ni)、锰(Mn)、镁(Mg)、铝(Al)、硼(B)、钛(Ti)、钒(V)、铬(Cr)、铁(Fe)、铜(Cu)、锌(Zn)、钼(Mo)、锡(Sn)、钙(Ca)、锶(Sr)、钨(W)、钇(Y)、镧(La)和锆(Zr)。
在一些实施例中，所述正极活性材料可包括，但不限于，钴酸锂、磷酸铁锂、磷酸锰铁锂、磷酸铁钠、磷酸钒锂、磷酸钒钠、磷酸钒氧锂、磷酸钒氧钠、钒酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、富锂锰基材料、镍钴铝酸锂及钛酸锂中的至少一种。
所述正极集流体可以是本领域常用的正极集流体，在一些实施例中，其包括，但不限于，铝箔或镍箔。
在一些实施例中，所述正极活性材料层可进一步包含粘结剂和/或导电剂。
粘合剂不仅可以提高正极活性材料颗粒间的结合，还可以提高正极活性材料与正极集流体的结合。在一些实施例中，粘合剂可包括，但不限于，聚 乙烯醇、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1,1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂、尼龙中的至少一种。
导电剂可以用于增强电极的导电性。本申请可以采用任何导电材料作为导电剂，只要该导电材料不引起不想要的化学变化。在一些实施例中，导电材料可包括，但不限于，基于碳的材料(例如，天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维等)、基于金属的材料(例如，金属粉、金属纤维等，包括例如铜、镍、铝、银等)、导电聚合物(例如，聚亚苯基衍生物)及其混合物中的至少一种。
本申请的电化学装置的负极可包括负极集流体和负极活性材料层。在一些实施例中，所述负极活性材料层设置在负极集流体上。在一些实施例中，所述负极活性材料层包含负极活性材料。
本申请的负极活性材料能够可逆地嵌入和脱出锂离子。负极活性材料的具体种类均不受到具体的限制，可根据需求进行选择。在一些实施例中，负极活性材料可包括或选自以下材料的一种或多种：碳质材料、硅质材料、合金系材料、含锂金属的复合氧化物材料。在一些实施例中，碳质材料可包括，但不限于，结晶碳、非晶碳及其混合物。结晶碳可以是无定形的或片形的、小片形的、球形的或纤维状的天然石墨或人造石墨。非晶碳可以是软碳、硬碳、中间相沥青碳化物、煅烧焦等。
在一些实施例中，负极活性材料可以包括，但不限于，天然石墨、人造石墨、中间相微碳球(简称为MCMB)、硬碳、软碳、硅、硅-碳复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化TiO 2-Li 4Ti 5O 12、Li-Al合金中的至少一种。
所述负极集流体可以是本领域常用的负极集流体。在一些实施例中，所述负极集流体包括，但不限于，铜箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜、覆有导电金属的聚合物基底及其组合。
在一些实施例中，所述负极活性材料层可进一步包含粘结剂和/或导电剂。粘结剂和导电剂可以采用前述正极中所揭示的材料，在此不做过多赘述。
本申请的电解液可以分为水系电解液和非水系电解液，其中相较于水系 电解液，采用非水系电解液的电化学装置可以在较宽的电压窗口下工作，从而达到较高的能量密度。
非水系电解液可包括有机溶剂。根据本申请，有机溶剂可为现有技术中已知的任何可作为电解液的溶剂的有机溶剂。在一些实施例中，本申请的有机溶剂包括或选自：碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸二甲酯(DMC)的至少一种。
本申请经过大量研究发现，当电解液中包含锂离子和下述式I表示的阴离子时，电化学装置具有优异的循环稳定性，且同时具有优异的低温放电性能和高温存储性能：
Figure PCTCN2020079264-appb-000006
其中，n为0-5范围内的整数；
R 1选自经取代或未经取代的烷基、经取代或未经取代的烯基、经取代或未经取代的芳基、经取代或未经取代的烃氧基，其中经取代时，所述取代基独立地选自硅烷基、硅氧烷基、氨基、醚基、酯基、羧基、磺酸基、巯基、氰基、卤素或其组合。
在一些实施例中，R 1选自经取代或未经取代的C 1-C 12烷基、经取代或未经取代的C 2-C 12烯基、经取代或未经取代的C 6-C 20芳基或者经取代或未经取代的C 1-C 12烃氧基。
在一些实施例中，R 1选自经取代或未经取代的C 1-C 10烷基、经取代或未经取代的C 2-C 10烯基、经取代或未经取代的C 6-C 10芳基或者经取代或未经取代的C 1-C 10烃氧基。
得到这样的效果的详细作用机理虽然不明，但可考虑如下：本申请式I表示的阴离子不仅能够促使锂离子在正极和电解液界面处的快速传输，从而改善电化学装置在低温下的放电表现；而且有助于在正极表面定向形成稳定的钝化膜，从而改善电化学装置在充放电过程中的循环稳定性并降低在高温存储条件下产气膨胀的程度以提高电化学装置的高温存储性能。
在一些实施例中，本申请所述的式I表示的阴离子包括或选自以下阴离子中 的一种或多种，但不限于此：
Figure PCTCN2020079264-appb-000007
在一些实施例中，基于所述电解液的总重量，所述式I表示的阴离子的质量百分含量的范围为：0.001wt％至7wt％、0.01wt％至5wt％、0.1wt％至3wt％或者0.1wt％至2wt％。在一些实施例中，基于所述电解液的总重量，所述式I表示的阴离子的质量百分含量为上述范围中的任一点值。例如，所述式I表示的阴离子的质量百分含量为约0.001wt％、约0.01wt％、约0.1wt％、约1wt％、约2wt％、约3wt％、约4wt％、约5wt％、约6wt％或者约7wt％。
在一些实施例中，本申请式I表示的阴离子与锂离子形成锂盐，以锂盐方式加入电解液中。
在一些实施例中，本申请式I表示的阴离子可以为1-丙基磷酸酐、1-乙腈基磷酸酐、1-乙基磷酸酐的分解产物。
在一些实施例中，本申请电解液任选地还包括氟代碳酸酯、氟代羧酸酯、含硫添加剂、含腈添加剂和锂盐添加剂中的一种或多种，以结合所述式I的阴离子促使电解液在电化学装置中发挥出更佳的作用。如下将针对上述成分、及其含量和作用进行详细描述。
在一些实施例中，本申请电解液还包括氟代碳酸酯。其中氟代碳酸酯结合电解液中的所述式I的阴离子，可以同时兼顾锂离子在正负极界面处的快速传输和在充放电过程中正负极的稳定性，从而改善电化学装置的循环性能和低温放电性 能。
在一些实施例中，所述氟代碳酸酯包括或选自3,3,3-三氟碳酸丙烯酯、氟代碳酸乙烯酯、2,2,3,3-四氟丙基碳酸甲酯、2,2,3,3,3-五氟丙基碳酸乙酯、二(2,2,2-三氟乙基)碳酸酯、二(2-氟乙基)碳酸酯、三氟甲基碳酸酯或双氟碳酸乙烯酯中的至少一种。
在一些实施例中，基于所述电解液的总重量，所述氟代碳酸酯的含量为0.01wt％至40wt％、0.01wt％至30wt％、0.01wt％至20wt％、0.01wt％至10wt％、0.01wt％至5wt％、0.1wt％至40wt％、0.1wt％至30wt％、0.1wt％至20wt％、0.1wt％至10wt％、0.1wt％至5wt％、1wt％至40wt％、1wt％至30wt％、1wt％至20wt％、1wt％至10wt％或者1wt％至5wt％。
在一些实施例中，本申请电解液还包括氟代羧酸酯。氟代羧酸酯与式I的阴离子相互作用可进一步提高高温存储性能。得到这样的效果的详细作用机理虽然不明，但可考虑如下：氟代羧酸酯与式I的阴离子相互作用提高了电解液的耐氧化性，能够有效地降低正极活性物质对电解液的氧化程度，同时还可以在正极表面形成复合SEI膜，增强对正极的保护。
在一些实施例中，所述氟代羧酸酯包括或选自乙酰基次氟酸酯、氟乙酸-2-氟乙酯、氟己酸乙酯、氟乙酸甲酯、氟乙酸乙酯、氟乙酸丁酯、三氟乙酸-2,2,2-三氟乙酯、5-氟己酸-2-氟乙酯、二氟乙酸-2,2,2-三氟乙基酯、2,2-二氟乙基三氟乙酸酯、2-氟乙基4-氟丁酸酯、三氟丙酸乙酯、2-氟丙酸乙酯、2,2-二氟乙酸乙酯、二氟丙酸乙酯、二氟乙酸甲酯或2-氟丙酸甲酯中的至少一种。
在一些实施例中，基于所述电解液的总重量，所述氟代羧酸酯的含量为0.01wt％至50wt％、0.01wt％至40wt％、0.01wt％至30wt％、0.01wt％至20wt％、0.01wt％至10wt％、0.01wt％至5wt％、0.1wt％至50wt％、0.1wt％至40wt％、0.1wt％至30wt％、0.1wt％至20wt％、0.1wt％至10wt％、0.1wt％至5wt％、1wt％至50wt％、1wt％至40wt％、1wt％至30wt％、1wt％至20wt％、1wt％至10wt％或者1wt％至5wt％。
在一些实施例中，本申请电解液还包括含硫添加剂。其中含硫添加剂也能够在正极表面形成稳定的SEI膜，实现对正极的保护。结合本申请式I所示的阴离子，含硫添加剂可以在正极表面上形成复合保护膜，进一步加强对正极的保护，提高电化学装置的稳定性。
在一些实施例中，所述含硫添加剂包括1,3-丁亚基硫酸酯、硫酸乙烯酯、1,3-丙烷磺内酯、1,3-丙二醇环硫酸酯、2,4-丁磺内酯、1,3-丁磺内酯、1-甲基-1,3-丙烷磺内酯、2-甲基-1,3-丙烷磺内酯、3-甲基-1,3-丙烷磺内酯、1-氟-1,3-丙烷磺内酯、2-氟-1,3-丙烷磺内酯或3-氟-1,3-丙烷磺内酯中的至少一种。
在一些实施例中，基于所述电解液的总重量，所述含硫添加剂的含量为0.01wt％至20wt％、0.01wt％至10wt％、0.01wt％至5wt％、0.1wt％至20wt％、0.1wt％至10wt％、0.1wt％至5wt％、1wt％至20wt％、1wt％至10wt％或者1wt％至5wt％。
在一些实施例中，本申请电解液还包括含腈添加剂。其中，含腈添加剂包含氰基(-CN)官能团。含腈添加剂与式I所示的阴离子共同作用，可以在正极表面形成性能优良的腈保护膜，很好地稳定正极活性材料中的活性金属，抑制活性金属的溶出，改善电化学装置的循环性能。
在一些实施例中，所述含腈添加剂包括以下化合物中的至少一种：
Figure PCTCN2020079264-appb-000008
其中元素M可选自C、Si中的一种；
其中R 51、R 61、R 62、R 63各自独立地选自经取代或未经取代的C 1-C 12亚烷基、经取代或未经取代的C 2-C 12亚烯基、R 0-S-R基团或R 0-O-R基团，其中R 0和R各自独立地选自经取代或未经取代的C 1-C 6亚烷基，其中经取代时，取代基选自卤素；
其中R 64选自H、经取代或未经取代的C 1-C 12亚烷基、经取代或未经取代的C 2-C 12亚烯基、R 0-S-R基团或R 0-O-R基团，其中R 0和R各自独立地选自经取代或未经取代的C 1-C 6亚烷基，其中经取代时，取代基选自卤素。在一些实施例中，所述含腈添加剂包括己二腈、丁二腈、戊二腈、丙二腈、2-甲基戊二腈、庚二腈、癸二腈、壬二腈、1,4-二氰基-2-丁烯、乙二醇双(丙腈)醚、3,3'-氧二丙腈、硫代丙二腈、己-2-烯二腈、丁烯二腈、2-戊烯二腈、乙基丁二腈、己-3-烯二腈、2-亚甲基戊二腈、4-氰基庚二腈、1,3,6-己烷三甲腈、1,3,5-己烷三甲腈、1,2,3-丙 三甲腈或1,2,3-三(2-氰氧基)丙烷中的至少一种。
含腈添加剂的保护效果与其用量有一定的相关性。在一些实施例中，基于所述电解液的总重量，所述含腈添加剂的含量为0.01wt％至20wt％、0.01wt％至10wt％、0.1wt％至20wt％、0.1wt％至10wt％、1wt％至20wt％或者1wt％至10wt％。
在一些实施例中，由于LiF能够增强SEI膜的稳定性，本申请电解液还可包括能够增加SEI膜中的LiF成分的锂盐添加剂，从而实现改善电化学装置循环稳定性的效果。
在一些实施例中，所述锂盐添加剂包括或者选自双三氟甲烷磺酰亚胺锂LiN(CF 3SO 2) 2(简写为LiTFSI)、双(氟磺酰)亚胺锂Li(N(SO 2F) 2)(简写为LiFSI)、双草酸硼酸锂LiB(C 2O 4) 2(简写为LiBOB)、四氟磷酸草酸锂(LiPF 4C 2O 2)、二氟草酸硼酸锂LiBF 2(C 2O 4)(简写为LiDFOB)、六氟铯酸锂(LiCsF 6)或二氟磷酸锂(LiPO 2F 2)中的至少一种。
在一些实施例中，基于所述电解液的总重量，所述锂盐添加剂的含量为0.01wt％至20wt％、0.01wt％至10wt％、0.01wt％至5wt％、0.01wt％至3wt％、0.1wt％至20wt％、0.1wt％至10wt％、0.1wt％至5wt％、0.1wt％至3wt％、1wt％至20wt％、1wt％至10wt％、1wt％至5wt％或者1wt％至3wt％。
在一些实施例中，所述电化学装置的所述负极活性材料层的表面包含微量的金属元素。在一些实施例中，上述金属元素分布在所述负极活性材料层的表面，例如，以负极表面(远离负极集流体的一侧)为基准，上述金属元素的分布深度不大于5mm。负极活性材料层表面的金属一部分源自于正极活性材料中的金属元素，一部分源自于电解液体系。例如，在注入电解液后，通过调控电解液的高温烘焙时间和干电池中的水含量可以调控在负极活性材料层的表面所分布的金属元素。此外，在电化学装置进行充放电的过程中，电解液会在一定程度上与正极活性材料发生化学反应从而导致正极活性材料中的金属以离子的形式溶解于电解液中。而在充电过程中，溶出的金属离子会被还原并在电化学装置的负极活性材料层的表面沉积。
由于负极活性材料层表面的金属元素中的一部分源自于正极活性材料，因此在本申请的一些实施例中，所述金属元素可以包括或选自钴(Co)、镍(Ni)、锰(Mn)、镁(Mg)、铝(Al)、硼(B)、钛(Ti)、钒(V)、铬(Cr)、铁(Fe)、铜(Cu)、锌(Zn)、钼(Mo)、锡(Sn)、钙(Ca)、锶(Sr)、钨(W)、钇(Y)、镧(La) 和锆(Zr)中的至少一种。
在本申请中，由于电解液中含有的式I所表示的阴离子有助于在正极表面形成坚固稳定的SEI膜以对正极活性材料实施保护，因此从正极活性材料中溶解出的并且分布至负极表面的金属元素通常是微量的。并且，在电解液中添加的金属离子的含量也是微量的。在一些实施例中，基于所述负极活性材料层的总重量，所述金属元素的含量范围在约200ppm以下。
事实上，在负极表面分布的微量的金属元素在一定程度上会增强负极表面的导电性，这有利于电子和锂离子的快速传输，从而改善电化学装置的倍率特性和低温放电性能。
在一些实施例中，本申请的电化学装置还包括设置在正极与负极之间的隔离膜以防止短路。本申请对电化学装置中使用的隔离膜的材料和形状没有特别限制，其可为现有技术中公开的任何材料和形状。在一些实施例中，隔离膜包括由对本申请的电解液稳定的材料形成的聚合物或无机物等。
在一些实施例中，隔离膜可包括基材层和表面处理层。基材层为具有多孔结构的无纺布、膜或复合膜。基材层的材料可以包括或者选自聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯和聚酰亚胺中的至少一种。具体地，可选用聚乙烯多孔膜、聚丙烯多孔膜、聚乙烯无纺布、聚丙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜等。
表面处理层可以是，但不限制于，聚合物层、无机物层或者由聚合物与无机物形成的混合层。
其中，无机物层可以包括无机颗粒和粘结剂。无机颗粒可以包括或者选自氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙和硫酸钡中的一种或几种的组合。粘结剂可以包括或者选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯和聚六氟丙烯中的一种或几种的组合。
其中，聚合物层可以包括聚合物。聚合物的材料可以包括或者选自聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚偏氟乙烯、聚(偏氟乙烯-六氟丙烯)中的至少一种。
本领域的技术人员将理解，本申请的电化学装置可以为锂离子电池，也可以为其他任何合适的电化学装置。在不背离本申请公开的内容的基础上，本申请实施例中的电化学装置包括发生电化学反应的任何装置，它的具体实例包括所有种类的一次电池、二次电池、太阳能电池或电容器。特别地，所述电化学装置是锂二次电池，包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
本申请电化学装置的用途没有特别限定，其可用于现有技术中已知的任何用途。根据本申请的一些实施例，本申请的电化学装置可以用于电子装置，其中电子装置包括，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
下面结合对比例及具体实施例对本发明的技术方案作进一步的说明，但并不局限于此。本领域的技术人员将理解，本申请中描述的制备方法仅是示范实施例，凡是对本发明技术方案进行修改或者同替换，而不脱离本发明技术方案的范围，均应涵盖在本发明的保护范围中。
具体实施例
以下说明本申请的实施例和对比例中的锂离子电池的制备方法和性能测试方法。
(一)锂离子电池的制备
(1)电解液的制备：在含水量<10ppm的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)和碳酸丙烯酯(PC)按照3:4:3的质量比混合均匀，再将充分干燥的锂盐LiPF 6溶解于上述非水溶剂中，其中LiPF 6的含量为1mol/L，以得到基础电解液。最后，按照下述表1-8所示，在基础电解液中加入一定质量的添加剂，配成实施例中的电解液。
(2)正极的制备：将正极活性材料钴酸锂(LiCoO 2)、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比96:2:2在适量的N-甲基吡咯烷酮(NMP)溶剂中充分搅拌混合，使其形成均匀的正极浆料；随后将该正极浆料涂覆于正极 集流体铝箔上，烘干、冷压，得到正极活性材料层，再经过裁片、焊接极耳，得到正极。
(3)负极的制备：将负极活性材料石墨、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照重量比97:2:1在适量的去离子水中充分搅拌混合，使其形成均匀的负极浆料；随后将该负极浆料涂覆于负极集流体铜箔上，烘干、冷压，得到负极活性材料层，再经过裁片、焊接极耳，得到负极。
(4)隔离膜：以聚乙烯(PE)多孔聚合物薄膜作为隔离膜。
(5)锂离子电池的制备：将正极、隔离膜、负极按顺序叠好，使隔离膜处于正极和负极之间以起到隔离作用，然后卷绕，置于外包装箔中干燥，注入上述制备好的电解液，经过真空封装、静置、化成、整形等工序，即完成锂离子电池的制备。
(二)锂离子电池的测试方法
(1)低温放电测试
在25℃的温度下，将锂离子电池以0.5C的电流放电至3.0V，静置5分钟，之后以0.5C的电流充电至4.45V，再在4.45V的电压下恒压充电至0.05C。同样在25℃的温度下，以0.2C的电流放电至3.0V，此时记录放电容量为C1。
在25℃的温度下，以0.5C的电流对锂离子电池充电至4.45V，再在4.45V的电压下恒压充电至0.05C。之后，将锂离子电池放置于-20℃温度下，静止30分钟以使得锂离子电池的温度与外界温度保持一致。在-20℃的条件下，以0.2C的电流放电至3.0V，此时记录放电容量为C2。
通过以下公式计算锂离子电池在-20℃条件下的放电百分比来衡量锂离子电池的低温放电性能：(C2/C1)×100％。
(2)高温存储膨胀测试
将锂离子电池在25℃下以0.5C的电流放电至3.0V，静置5分钟。之后以0.5C的电流充电至4.45V，再在4.45V的电压下恒压充电至0.05C，使用PPG软包电池测厚仪测试满充时锂离子电池的厚度，记为a。将锂离子电池放置到80℃的烘箱中存储8小时，测试8小时之后的厚度，记为b。
通过以下公式计算锂离子电池在80℃条件下的厚度膨胀率来衡量锂离子电池的高温存储性能：(b-a)/a×100％。
(3)25℃下的循环测试
将锂离子电池在25℃下以0.5C的电流放电至3.0V，静置5分钟。之后以0.5C的电流充电至4.45V，再在4.45V的电压下恒压充电至0.05C；充电完毕后，以0.5C的电流放电至3.0V，此为一个充放电循环(即，循环一圈)。
按此充放电流程在25℃下循环800圈，其中第一圈的放电容量记为C1，第800圈的放电容量记为C800。通过以下公式计算锂离子电池在25℃下的循环容量保持率来衡量锂离子电池的循环性能：(C800/C1)×100％。
(4)45℃下的循环测试
将锂离子电池在45℃下以0.5C的电流放电至3.0V，静置5分钟。之后以0.5C的电流充电至4.45V，再在4.45V的电压下恒压充电至0.05C；充电完毕后，以0.5C的电流放电至3.0V，此为一个充放电循环(即，循环一圈)。
按此充放电流程在45℃下循环500圈，其中第一圈的放电容量记为C1，第500圈的放电容量记为C500。通过以下公式计算锂离子电池在45℃下的循环容量保持率来衡量锂离子电池在高温下的循环性能：(C500/C1)×100％。
(5)金属元素测试
将锂离子电池以0.5C的电流放电至3.0V，静置5分钟，之后以0.05C的电流继续放电至2.8V。将放完电之后的锂离子电池在手套箱中进行拆解，使用少量的碳酸二甲酯(DMC)溶剂淋洗负极表面2-3次，去除负极表面残留的电解液，将负极极片晾干后，取负极的中间区域进行感应耦合等离子体(ICP)测试以测得金属元素在负极中的含量。
实施例1-19和对比例1
按照上述制备方法制备实施例1-19以及对比例1的电解液及锂离子电池，其中对比例1采用的是基础电解液，而实施例1-19在基础电解液中分别加入如表1所示的组分和含量，其中含量为该组分基于电解液的总重量的质量百分含量，其中式I-2、I-3、I-4、I-7的物质以锂盐形式加入。此外，表1还示出了实施例1-19和对比例1中的锂离子电池的电化学测试结果。
表1
Figure PCTCN2020079264-appb-000009
Figure PCTCN2020079264-appb-000010
参见表1中的电化学测试结果可以看出，相较于对比例1，本申请实施例1-19中的电解液由于存在一定含量的本申请所述式I的阴离子，其对应得到的电化学装置在低温下的放电性能和在高温下的存储性能均得到了明显的提高。也即，通过在电解液中引入所述式I的阴离子，所得到的电化学装置无论是在低温环境下还是在高温条件下均具有优异的电化学表现。
关于低温放电性能的改进，这是由于式I表示的阴离子中含有的P＝O键具有富电子特性，即便在-20℃的低温下，也能够在一定程度上加速锂离子在正极界面处的转移和传输。
关于高温存储性能的改进，这是由于式I表示的阴离子有助于在正极表面定向形成坚固稳定的SEI膜，从而能够对正极活性物质和正极实施很好的保护，使得电化学装置即便在80℃的高温下长时间存储也不会发生严重的产气膨胀现象。
实施例5和实施例20-26
实施例20-26是在实施例5的基础上进行的改进。具体来讲，实施例20-26是在实施例5所述的电解液中进一步加入了氟代碳酸酯，其中具体加入的组分和含量以及所得锂离子电池的性能测试结果请参见下述表2。
表2
Figure PCTCN2020079264-appb-000011
参见表2中的电化学测试结果可以看出，相较于实施例5，本申请实施例20-26中的电解液由于存在一定含量的氟代碳酸酯，其对应得到的电化学装置在低温下的放电性能和在常温下的循环稳定性均得到了一定程度的改进。这是由于式I表示的阴离子与氟代碳酸酯共同作用使电解液具有较高的还原电位，可以在负极表面提前形成SEI膜，对负极活性材料提供保护，从而能够改善电化学装置的循环性能。此外，SEI膜的形成有助于降低在负极界面处副反应的反生，从而抑制由副反应产生的副产物在电极表面的积累所引起的阻抗的增加，促使锂离子在负极界面处的快速传输，从而能够改善电化学装置在低温下的放电性能。
实施例5和实施例27-33
实施例27-33是在实施例5的基础上进行的改进。具体来讲，实施例27-33是在实施例5所述的电解液中进一步加入了氟代羧酸酯，其中具体加入的组分和含量以及所得锂离子电池的性能测试结果请参见下述表3。
表3
Figure PCTCN2020079264-appb-000012
Figure PCTCN2020079264-appb-000013
参见表3中的电化学测试结果可以看出，相较于实施例5，本申请实施例27-33中的电解液由于存在一定含量的氟代羧酸酯，其对应得到的电化学装置在80℃的高温下存储8h所经历的膨胀程度会进一步降低。这是由于式I表示的阴离子与氟代羧酸酯共同作用，提高电解液的耐氧化程度，从而能够有效地抵抗来自正极活性物质的氧化，减轻产气现象的出现；同时可以在正极表面形成复合SEI膜，进一步加强对正极的保护，从而进一步抑制产气膨胀现象的发生。
实施例5和实施例34-41
实施例34-41是在实施例5的基础上进行的改进。具体来讲，实施例34-41是在实施例5所述的电解液中进一步加入了含硫添加剂，其中具体加入的组分和含量以及所得锂离子电池的性能测试结果请参见下述表4。
参见表4中的电化学测试结果可以看出，相较于实施例5，本申请实施例34-41中的电解液由于存在一定含量的含硫添加剂，其对应得到的电化学装置在80℃的高温下存储8h所经历的膨胀程度会进一步降低。这是由于含硫添加剂也能够在正极表面形成稳定的SEI膜，并且与本申请式I所示的阴离子相互配合，可以在正极表面上形成复合的保护膜，进一步加强对正极的保护，从而进一步抑制产气膨胀现象的发生。
表4
Figure PCTCN2020079264-appb-000014
实施例5和实施例42-63
实施例42-63是在实施例5的基础上进行的改进。具体来讲，实施例42-63是在实施例5所述的电解液中进一步加入了含腈添加剂，其中具体加入的组分和含量以及所得锂离子电池的性能测试结果请参见下述表5。
表5
Figure PCTCN2020079264-appb-000015
参见表5中的电化学测试结果可以看出，相较于实施例5，本申请实施例42-63中的电解液由于存在一定含量的含腈添加剂，其对应得到的电化学装置在45℃的较高温度下的循环性能有了进一步的提高。这是由于含腈添加剂可以在正极表面形成性能优良的腈保护膜，提高正极材料在充放电过程中的稳定性。同时， 含腈添加剂可以很好地稳定正极活性材料中的活性金属，抑制活性金属的溶出，改善电化学装置的循环性能。
实施例5和实施例64-73
实施例64-73是在实施例5的基础上进行的改进。具体来讲，实施例64-73是在实施例5所述的电解液中进一步加入了锂盐添加剂，其中具体加入的组分和含量以及所得锂离子电池的性能测试结果请参见下述表6。
表6
Figure PCTCN2020079264-appb-000016
参见表6中的电化学测试结果可以看出，相较于实施例5，本申请实施例64-73的电化学装置在低温下的放电性能稍有恶化，但是其在较高温度下的循环稳定性得到了进一步的改进。这是由于所加入的锂盐添加剂能够增加SEI膜中的LiF成分，从而增强SEI膜的稳定性，实现改善电化学装置循环稳定性的效果。
实施例5和实施例74-78
实施例74-78是在实施例5的基础上进行的改进。具体来讲，通过高温烘烤时间控制注电解液前电池的水含量分别为80ppm、100ppm、140ppm、200ppm、240ppm和270ppm，从而分别得到表7的实施例5和实施例74-78。相较于实施例5，实施例74-78的负极的表面不大于10μm的深度存在一定含量的金属钴元素，其中具体含量以及所得锂离子电池的性能测试结果请参见下述表7。
表7
Figure PCTCN2020079264-appb-000017
参见表7中的电化学测试结果可以看出，相较于实施例5，本申请实施例74-78中的负极的表面分布有更多含量的钴元素，其对应得到的电化学装置在低温下的放电性能得到了进一步的改进。这是由于在负极表面分布的金属元素在一定程度上会增强负极表面的导电性，这有利于电子和锂离子的快速传输，从而改善电化学装置的低温放电性能。
实施例21和实施例79-84
实施例79-84是在实施例21的基础上分别加入了含硫添加剂、氟代羧酸酯、腈类添加剂或其组合，其中具体加入的组分和含量以及所得锂离子电池的性能测试结果请参见下述表8-1和表8-2。
表8-1
Figure PCTCN2020079264-appb-000018
表8-2
Figure PCTCN2020079264-appb-000019
Figure PCTCN2020079264-appb-000020
参见表8-1和表8-2中的电化学测试结果可以看出，采用本申请的多种添加剂的组合，可以得到具有优异的低温放电性能和高温存储性能的电化学装置，且所述电化学装置在常温和较高温度下均能够表现出出色的循环性能。
整个说明书中对“实施例”、“部分实施例”、“一个实施例”、“另一举例”、“举例”、“具体举例”或“部分举例”的引用，其所代表的意思是在本申请中的至少一个实施例或举例包含了该实施例或举例中所描述的特定特征、结构、材料或特性。因此，在整个说明书中的各处所出现的描述，例如：“在一些实施例中”、“在实施例中”、“在一个实施例中”、“在另一个举例中”、“在一个举例中”、“在特定举例中”或“举例”，其不必然是引用本申请中的相同的实施例或示例。此外，本文中的特定特征、结构、材料或特性可以以任何合适的方式在一个或多个实施例或举例中结合。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。

Claims (11)

  1. 一种电化学装置，包括：
    正极，所述正极包括正极集流体和正极活性材料层，所述正极活性材料层包含正极活性材料；
    负极，所述负极包括负极集流体和负极活性材料层，所述负极活性材料层包含负极活性材料；和
    电解液，所述电解液包含锂离子和式I表示的阴离子：
    Figure PCTCN2020079264-appb-100001
    其中，
    n为0-5范围内的整数；
    R 1选自经取代或未经取代的C 1-C 12烷基、经取代或未经取代的C 2-C 12烯基、经取代或未经取代的C 6-C 20芳基、经取代或未经取代的C 1-C 12烃氧基，其中经取代时，所述取代基独立地选自硅烷基、硅氧烷基、氨基、醚基、酯基、羧基、磺酸基、巯基、氰基、卤素或其组合。
  2. 根据权利要求1所述的电化学装置，其中所述式I表示的阴离子包含：
    Figure PCTCN2020079264-appb-100002
    Figure PCTCN2020079264-appb-100003
    Figure PCTCN2020079264-appb-100004
    中的至少一种；
    其中基于所述电解液的总重量，所述式I表示的阴离子的质量百分含量为0.001％至7％。
  3. 根据权利要求1所述的电化学装置，其进一步包括氟代碳酸酯、氟代羧酸酯、含硫添加剂、含腈添加剂或锂盐添加剂中的一种或多种。
  4. 根据权利要求3所述的电化学装置，其中所述氟代碳酸酯包括3,3,3-三氟碳酸丙烯酯、氟代碳酸乙烯酯、2,2,3,3-四氟丙基碳酸甲酯、2,2,3,3,3-五氟丙基碳酸乙酯、二(2,2,2-三氟乙基)碳酸酯、二(2-氟乙基)碳酸酯、三氟甲基碳酸酯或双氟碳酸乙烯酯中的至少一种；其中基于所述电解液的总重量，所述氟代碳酸酯的含量为0.01％至20％。
  5. 根据权利要求3所述的电化学装置，其中所述氟代羧酸酯包括乙酰基次氟酸酯、氟乙酸-2-氟乙酯、氟己酸乙酯、氟乙酸甲酯、氟乙酸乙酯、氟乙酸丁酯、三氟乙酸-2,2,2-三氟乙酯、5-氟己酸-2-氟乙酯、二氟乙酸-2,2,2-三氟乙基酯、2,2-二氟乙基三氟乙酸酯、2-氟乙基4-氟丁酸酯、三氟丙酸乙酯、2-氟丙酸乙酯、2,2-二氟乙酸乙酯、二氟丙酸乙酯、二氟乙酸甲酯或2-氟丙酸甲酯中的至少一种；其中基于所述电解液的总重量，所述氟代羧酸酯的含量为0.01％至30％。
  6. 根据权利要求3所述的电化学装置，其中所述含硫添加剂包括1,3-丁亚基硫酸酯、硫酸乙烯酯、1,3-丙烷磺内酯、1,3-丙二醇环硫酸酯、2,4-丁磺内酯、1,3-丁磺内酯、1-甲基-1,3-丙烷磺内酯、2-甲基-1,3-丙烷磺内酯、3-甲基-1,3-丙烷磺内酯、1-氟-1,3-丙烷磺内酯、2-氟-1,3-丙烷磺内酯或3-氟-1,3-丙烷磺内酯中的至少一种；其中基于所述电解液的总重量，所述含硫添加剂的含量为0.01％至10％。
  7. 根据权利要求3所述的电化学装置，其中所述含腈添加剂包括以下化合物中的至少一种：
    Figure PCTCN2020079264-appb-100005
    其中M选自C、Si；
    其中R 51、R 61、R 62、R 63各自独立地选自经取代或未经取代的C 1-C 12亚烷基、经取代或未经取代的C 2-C 12亚烯基、R 0-S-R基团或R 0-O-R基团，其中R 0、R各自独立地选自经取代或未经取代的C 1-C 6亚烷基，其中经取代时，取代基选自卤素；
    其中R 64选自H、经取代或未经取代的C 1-C 12亚烷基、经取代或未经取代的C 2-C 12亚烯基、R 0-S-R基团或R 0-O-R基团，其中R 0、R各自独立地选自经取代或未经取代的C 1-C 6亚烷基，其中经取代时，取代基选自卤素。
  8. 根据权利要求3所述的电化学装置，其中所述含腈添加剂包括己二腈、丁二腈、戊二腈、丙二腈、2-甲基戊二腈、庚二腈、癸二腈、壬二腈、1,4-二氰基-2-丁烯、乙二醇双(丙腈)醚、3,3'-氧二丙腈、硫代丙二腈、己-2-烯二腈、丁烯二腈、2-戊烯二腈、乙基丁二腈、己-3-烯二腈、2-亚甲基戊二腈、4-氰基庚二腈、1,3,6-己烷三甲腈、1,3,5-己烷三甲腈、1,2,3-丙三甲腈或1,2,3-三(2-氰氧基)丙烷中的至少一种；其中基于所述电解液的总重量，所述含腈添加剂的含量为0.01％至10％。
  9. 根据权利要求3所述的电化学装置，其中所述锂盐添加剂包括双三氟甲烷磺酰亚胺锂、双(氟磺酰)亚胺锂、双草酸硼酸锂、四氟磷酸草酸锂、二氟草酸硼酸锂、六氟铯酸锂或二氟磷酸锂中的至少一种；其中基于所述电解液的总重量，所述锂盐添加剂的含量为0.01％至5％。
  10. 根据权利要求1所述的电化学装置，其中所述负极活性材料层含有金属元素，所述金属元素包括Co、Mn、Ni、Al或Cu中的至少一种；其中基于所述负极活性材料层的总重量，所述金属元素的含量为200ppm以下。
  11. 一种电子装置，其包含权利要求1-10中任一项所述的电化学装置。
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