WO2021190388A1 - 电化学装置及包括其的电子装置 - Google Patents

电化学装置及包括其的电子装置 Download PDF

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WO2021190388A1
WO2021190388A1 PCT/CN2021/081455 CN2021081455W WO2021190388A1 WO 2021190388 A1 WO2021190388 A1 WO 2021190388A1 CN 2021081455 W CN2021081455 W CN 2021081455W WO 2021190388 A1 WO2021190388 A1 WO 2021190388A1
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substituted
electrolyte
unsubstituted
group
electrochemical device
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PCT/CN2021/081455
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English (en)
French (fr)
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崔辉
栗文强
熊亚丽
郑建明
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宁德新能源科技有限公司
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Priority to EP21774244.4A priority Critical patent/EP4131546A4/en
Priority to US17/475,704 priority patent/US20220006122A1/en
Publication of WO2021190388A1 publication Critical patent/WO2021190388A1/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
    • H01M10/05—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
    • 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
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • H01M10/44—Methods for charging or discharging
    • 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
    • H01M4/46—Alloys based on magnesium or aluminium
    • H01M4/463—Aluminium based
    • 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, in particular to electrochemical devices and electronic devices including them.
  • Electrochemical devices for example, lithium ion batteries
  • electrochemical devices are widely used in wearable devices, smart phones, drones, notebook computers and other fields because of their high working voltage, high energy density, environmental friendliness, stable cycle, and safety.
  • higher requirements are put forward for lithium-ion batteries, that is, high energy density, long cycle life and excellent storage characteristics.
  • the interaction between the electrolyte and the positive and negative electrodes will affect these properties, especially when the working voltage is increased to 4.4V to improve the energy density of the lithium-ion battery, the instability of the interface between the electrolyte and the positive electrode active material increases, and the lithium ion The battery swells severely at high temperature, and the cycle performance and charge-discharge performance are reduced, which severely restricts the performance of the lithium-ion battery.
  • the existing lithium-ion battery technology usually only optimizes the electrolyte or improves the positive electrode active material, but lacks in-depth exploration of the entire lithium-ion battery system, so that the overall performance of the lithium-ion battery cannot be improved.
  • the present application provides an electrochemical device in an attempt to solve at least one problem existing in the related field at least to some extent.
  • This application optimizes the entire electrochemical device system by adding a nitrile compound in the electrolyte and adjusting the relationship between the cyano group content and the transition metal ion content in the electrolyte, thereby improving the high-temperature cycle performance and floating performance of the electrochemical device.
  • this application also studies the influence of the relationship between the content of doping elements in the positive electrode active material and the content of cyano groups in the electrolyte on the high-temperature cycle performance and floating performance of the electrochemical device.
  • the present application provides an electrochemical device, which includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte includes a nitrile compound and a transition metal ion, and satisfies: 5 ⁇ A/B ⁇ 30000, wherein, based on the total moles of the electrolyte, the mole percentage of cyano groups in the electrolyte is A%, and based on the total weight of the electrolyte, the transition metal in the electrolyte The weight percentage of ions is B%.
  • the transition metal ion includes at least one of iron ion, cobalt ion, nickel ion, manganese ion, or copper ion.
  • the transition metal ion includes at least one of cobalt ion or copper ion.
  • the nitrile compound includes at least one of a compound of formula I, a compound of formula II, or a compound of formula III:
  • R 1 is selected from substituted or unsubstituted C 1 to C 10 alkylene, substituted or unsubstituted C 1 to C 10 alkyleneoxy, substituted or unsubstituted C 2 to C 10 alkenylene, substituted or Unsubstituted C 6 to C 12 arylene, substituted or unsubstituted C 6 to C 10 cycloalkylene, wherein when substituted, the substituent is selected from at least one of halogen, cyano or carboxy; wherein R 21 , R 22 , and R 23 are each independently selected from a single bond, a substituted or unsubstituted C 1 to C 5 alkylene group, a substituted or unsubstituted C 1 to C 10 alkyleneoxy group, and when substituted, substituted The group is selected from at least one of halogen, cyano or carboxy; wherein R 31 is selected from substituted or unsubstituted C 1 to C 5 alkylene, substituted or unsubstitute
  • the weight percentage of the cobalt ions in the electrolyte is less than or equal to 0.1%, and the weight percentage of the copper ions in the electrolyte is less than or equal to 0.1%.
  • the positive electrode includes a positive electrode active material, the positive electrode active material contains aluminum element, and based on the total weight of the positive electrode active material, the weight percentage of the aluminum element is C%, the The numerical range of C is: 0.001 ⁇ C ⁇ 1.
  • the A and C satisfy the following relationship: 0.01 ⁇ A/C ⁇ 170.
  • the curve obtained by the differential scanning calorimetry test of the positive electrode active material includes a first exothermic peak and a second exothermic peak, wherein the temperature corresponding to the first exothermic peak is X, 240°C ⁇ X ⁇ 280°C, the temperature corresponding to the second exothermic peak is Y, and 280°C ⁇ Y ⁇ 340°C.
  • the peak area of the first exothermic peak is less than or equal to 50 J/g, and the peak area of the second exothermic peak is less than or equal to 800 J/g.
  • the electrolyte further includes a compound of formula IV:
  • R 41 is selected from substituted or unsubstituted C 1 to C 12 alkyl, substituted or unsubstituted C 3 to C 12 cycloalkyl, substituted or unsubstituted C 2 to C 12 alkenyl, substituted or unsubstituted C 2 to C 12 alkynyl, substituted or unsubstituted C 6 to C 22 aryl, substituted or unsubstituted C 5 to C 22 heteroaryl, wherein when substituted, the substituent is selected from halogen, cyano or carboxyl At least one of; wherein based on the weight of the electrolyte, the weight percentage of the compound of formula IV is 0.001% to 5%.
  • the electrolyte further includes a first additive
  • the first additive includes vinyl ethylene carbonate, fluorobenzene, lithium difluorophosphate, lithium tetrafluoroborate, 1,3,2-dioxazole thiophene At least one of -2,2-dioxide, fluoroethylene carbonate, vinylene carbonate or 1,3-propane sultone, based on the total weight of the electrolyte, the first additive The weight percentage is 0.001% to 13%.
  • the transition metal ions of the positive electrode active material are eluted and the structural distortion of the positive electrode active material during the charge and discharge process is stabilized, thereby Improve the high temperature cycle performance and floating charge performance of electrochemical devices.
  • the present application also provides an electronic device, which includes any one of the electrochemical devices described above.
  • FIG. 1 is a differential scanning calorimetry (DSC) test curve diagram of the positive active material of Example 30 of the application.
  • the terms “approximately”, “substantially”, “substantially” and “about” are 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 ⁇ 10% of the stated value, such as less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, Less than or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%.
  • the difference between two values is less than or equal to ⁇ 10% of the average value of the value (for example, less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, less than Or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%), then the two values can be considered "substantially" the same.
  • a list of items connected by the terms “at least one of”, “at least one of”, “at least one of” or other similar terms may mean the listed items Any combination of. For example, if items A and B are listed, then the phrase “at least one of A or B” means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, or C” means only A; or only B; only C; A and B (excluding C); A and C (exclude B); B and C (exclude A); or all of A, B, and C.
  • Project A can contain a single component or multiple components.
  • Project B can contain a single component or multiple components.
  • Item C can contain a single component or multiple components.
  • alkyl is intended to be a linear saturated hydrocarbon structure having 1 to 20 carbon atoms.
  • Alkyl is also expected to be a branched or cyclic hydrocarbon structure having 3 to 20 carbon atoms.
  • the alkyl group may be an alkyl group of 1 to 20 carbon atoms, an alkyl group of 1 to 10 carbon atoms, an alkyl group of 1 to 5 carbon atoms, an alkyl group of 5 to 20 carbon atoms, and an alkyl group of 5 to 15 carbon atoms.
  • butyl means to include n-butyl, sec-butyl, isobutyl, and tert-butyl And cyclobutyl
  • propyl includes n-propyl, isopropyl and cyclopropyl.
  • 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 Base and so on.
  • the alkyl group may be optionally substituted.
  • alkylene means a linear or branched divalent saturated hydrocarbon group.
  • the alkylene group may be an alkylene group of 1 to 20 carbon atoms, an alkylene group of 1 to 15 carbon atoms, an alkylene group of 1 to 10 carbon atoms, and an alkylene group of 1 to 5 carbon atoms.
  • alkylene groups include, for example, methylene, ethane-1,2-diyl ("ethylene”), propane-1,2-diyl, propane-1,3-diyl, butane -1,4-diyl, pentane-1,5-diyl and so on.
  • the alkylene group may be optionally substituted.
  • 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 10 carbon atoms, or a cycloalkyl group of 3 to 6 carbon atoms.
  • the cycloalkyl group may be cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like.
  • cycloalkyl groups may be optionally substituted.
  • cycloalkylene alone or as part of another substituent means a divalent radical derived from a cycloalkyl group.
  • alkenyl refers to a monovalent unsaturated hydrocarbon group that can be straight or branched and has at least one and usually 1, 2, or 3 carbon-carbon double bonds. Unless otherwise defined, the alkenyl group usually contains 2-20 carbon atoms, for example, it can be an alkenyl group of 2 to 20 carbon atoms, an alkenyl group of 6 to 20 carbon atoms, or an alkenyl group of 2 to 10 carbon atoms. Group or alkenyl group of 2 to 6 carbon atoms.
  • alkenyl groups include, for example, vinyl, n-propenyl, isopropenyl, n-but-2-enyl, but-3-enyl, n-hex-3-enyl, and the like. In addition, alkenyl groups may be optionally substituted.
  • alkenylene encompasses straight chain and branched chain alkenylene groups. When an alkenylene group having a specific carbon number is specified, it is expected to encompass all geometric isomers having that carbon number.
  • the alkenylene group may be an alkenylene group of 2 to 20 carbon atoms, an alkenylene group of 2 to 15 carbon atoms, an alkenylene group of 2 to 10 carbon atoms, or an alkenylene group of 2 to 5 carbon atoms.
  • Representative alkylene groups include, for example, vinylene, propenylene, butenylene, and the like.
  • alkenylene groups may be optionally substituted.
  • alkynyl refers to a monovalent unsaturated hydrocarbon group that can be straight or branched and has at least one and usually 1, 2, or 3 carbon-carbon triple bonds. Unless otherwise defined, the alkynyl group usually contains 2 to 20 carbon atoms, for example, an alkynyl group of 2 to 20 carbon atoms, an alkynyl group of 6 to 20 carbon atoms, or an alkynyl group of 2 to 10 carbon atoms. Alkynyl or alkynyl of 2 to 6 carbon atoms.
  • alkynyl groups include, for example, ethynyl, prop-2-ynyl (n-propynyl), n-but-2-ynyl, n-hex-3-ynyl, and the like. In addition, alkynyl groups may be optionally substituted.
  • alkoxy refers to the group L-O-, where L is an alkyl group.
  • the alkoxy group herein may be an alkoxy group having 1 to 12 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or an alkoxy group having 5 to 12 carbon atoms. Alkoxy or alkoxy of 5 to 10 carbon atoms.
  • alkyleneoxy alone or as part of another substituent means a divalent radical derived from an alkoxy group.
  • 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 to C 50 aryl group, a C 6 to C 40 aryl group, a C 6 to C 30 aryl group, a C 6 to C 20 aryl group, or a C 6 to C 10 aryl group.
  • aryl groups include, for example, phenyl, methylphenyl, propylphenyl, isopropylphenyl, benzyl and naphth-1-yl, naphth-2-yl, and the like. In addition, aryl groups may be optionally substituted.
  • arylene alone or as part of another substituent means a divalent radical derived from an aryl group.
  • heteroaryl encompasses monocyclic heteroaromatic groups that may include one to three heteroatoms, such as pyrrole, furan, thiophene, imidazole, oxazole, thiazole, triazole, pyrazole, pyridine, pyrazine, and pyrimidine Wait.
  • heteroaryl also includes polycyclic heteroaromatic systems having two or more rings shared by two adjacent rings (the rings are "fused") in which two atoms are At least one is heteroaryl, and the other ring may be cycloalkyl, cycloalkenyl, aryl, heterocycle, and/or heteroaryl.
  • the heteroaryl group may be a C 6 to C 50 heteroaryl group, a C 6 to C 40 heteroaryl group, a C 6 to C 30 heteroaryl group, a C 6 to C 20 heteroaryl group, or a C 6 to C 10 heteroaryl group .
  • heteroaryl groups may be optionally substituted.
  • heterocyclic group encompasses aromatic and non-aromatic cyclic groups. Heteroaromatic cyclic group also means heteroaryl. In some embodiments, the heteroaromatic ring group and the heteronon-aromatic ring group are a C 1 to C 50 heterocyclic group, a C 1 to C 40 heterocyclic group, a C 1 to C 30 heterocyclic group including at least one heteroatom. Heterocyclic group, C 1 to C 20 heterocyclic group, C 1 to C 10 heterocyclic group, C 1 to C 6 heterocyclic group.
  • morpholinyl for example, morpholinyl, piperidinyl, pyrrolidinyl, etc., and cyclic ethers, such as tetrahydrofuran, tetrahydropyran, and the like.
  • the heterocyclic group may be optionally substituted.
  • heterocyclylene alone or as part of another substituent means a divalent radical derived from a heterocyclic group.
  • heteroatom encompasses O, S, P, N, B or isosteres thereof.
  • halogen can be F, Cl, Br, or I.
  • the present application provides an electrochemical device.
  • the electrochemical device includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte of the electrochemical device includes a nitrile compound and a transition metal ion, and satisfies: 5 ⁇ A/B ⁇ 30000, where based on the total moles of the electrolyte, the mole percentage of cyano groups in the electrolyte is A%, and based on the total weight of the electrolyte, the total weight percentage of transition metal ions in the electrolyte is B% .
  • the transition metal ion includes at least one of iron ion, cobalt ion, nickel ion, manganese ion, or copper ion.
  • the transition metal ion includes at least one of cobalt ion or copper ion.
  • the nitrile compound includes at least one of a compound of formula I, a compound of formula II, or a compound of formula III:
  • R 1 is selected from substituted or unsubstituted C 1 to C 10 alkylene, substituted or unsubstituted C 1 to C 10 alkyleneoxy, substituted or unsubstituted C 2 to C 10 alkenylene Group, substituted or unsubstituted C 6 to C 12 arylene group, substituted or unsubstituted C 6 to C 10 cycloalkylene group, wherein when substituted, the substituent is selected from at least one of halogen, cyano or carboxyl kind.
  • R 21 , R 22 and R 23 are each independently selected from a single bond, a substituted or unsubstituted C 1 to C 5 alkylene group, a substituted or unsubstituted C 1 to C 10 alkyleneoxy group, When substituted, the substituent is selected from at least one of halogen, cyano or carboxyl.
  • R 31 is selected from substituted or unsubstituted C 1 to C 5 alkylene, substituted or unsubstituted C 1 to C 5 alkoxy, substituted or unsubstituted C 2 to C 10 Alkenylene, substituted or unsubstituted C 3 to C 6 cycloalkylene, substituted or unsubstituted C 6 to C 10 arylene, substituted or unsubstituted C 1 to C 6 heterocyclic ring
  • the substituent is selected from at least one of halogen, cyano or carboxyl, wherein the heteroatom in the heterocyclylene group is selected from at least one of O, N, P or S.
  • the nitrile compound of formula I may include, but is not limited to, malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelaonitrile, and sunflower dinitrile.
  • the nitrile compound of formula II may include
  • the nitrile compound of formula III may include
  • the transition metal ions include at least one of cobalt (Co) ions or copper (Cu) ions, wherein based on the weight of the electrolyte, the weight percentage of cobalt ions is less than or equal to about 0.1%, and the weight of copper ions The percentage is less than or equal to about 0.1%. In some embodiments, based on the weight of the electrolyte, the weight percentage of cobalt ions is less than or equal to about 0.08%, less than or equal to about 0.05%, less than or equal to about 0.03%, less than or equal to about 0.02%, or less than or equal to about 0.001%.
  • the weight percentage of copper ions is less than or equal to about 0.08%, less than or equal to about 0.05%, less than or equal to about 0.03%, less than or equal to about 0.02%, or less than or equal to about 0.001%.
  • the electrochemical device can maintain better cycle performance and floating performance.
  • the weight percentage of cobalt ions in the electrolyte exceeds 0.1%, the structure of the positive electrode active material is destroyed, causing the transition metal ions in the positive electrode active material to dissolve, depositing on the negative electrode through the electrolyte and catalyzing the decomposition of the negative electrode protective film, deteriorating the electrochemical device Performance.
  • the negative electrode current collector is copper foil.
  • the copper foil is not covered and protected before formation. It is exposed to the electrolyte and is easily corroded by the electrolyte.
  • the copper foil is oxidized to form copper ions and dissolve in the electrolyte;
  • copper ions are reduced to copper and deposited on the negative electrode, which catalyzes the decomposition of the solid electrolyte interface (SEI) film of the negative electrode and deteriorates the performance of the electrochemical device.
  • SEI solid electrolyte interface
  • the electrochemical device of the present application can still maintain good high-temperature cycle performance and floating charge performance when the upper charging voltage is increased to 4.4V.
  • the nitrile compound of the present application can effectively separate the easily oxidizable components in the electrolyte from the positive electrode active material, thereby stabilizing the structure of the positive electrode active material, reducing the dissolution of transition metal ions in the positive electrode active material, and improving the high temperature cycle of the electrochemical device And floating charge performance.
  • the nitrile compound can form a stable polymer on the negative electrode (for example, the exposed copper foil surface), thereby protecting the negative electrode interface and alleviating the corrosion of the copper foil, thereby improving high-temperature storage and floating performance.
  • the mole percentage A% of the cyano group in the electrolyte and the total weight percentage B% of the first metal ion in the electrolyte satisfy the following proportional relationship: 5 ⁇ A/B ⁇ 30000. When the A/B is in this range, the electrochemical device will have good high temperature cycling and floating charge performance.
  • the electrolyte may further include a compound of formula IV
  • R 41 is selected from substituted or unsubstituted C 1 to C 12 alkyl, substituted or unsubstituted C 3 to C 12 cycloalkyl, substituted or unsubstituted C 2 to C 12 alkenyl, substituted Or unsubstituted C 2 to C 12 alkynyl, substituted or unsubstituted C 6 to C 22 aryl, substituted or unsubstituted C 5 to C 22 heteroaryl, wherein when substituted, the substituent is selected from halogen, At least one of a cyano group or a carboxyl group; wherein the content of the compound of formula IV is 0.001% to 5% based on the total weight of the electrolyte.
  • the compound of formula IV comprises
  • the electrolyte further includes a first additive
  • the first additive includes vinyl ethylene carbonate (VEC), fluorobenzene, lithium difluorophosphate (LiPO 2 F 2 ), lithium tetrafluoroborate, 1,3,2-Dioxazolethiophene-2,2-dioxide (DTD), fluoroethylene carbonate (FEC), vinylene carbonate (VC) or 1,3-propane sultone (PS ) At least one of.
  • the weight percentage of the first additive is about 0.01% to about 13% based on the weight of the electrolyte.
  • the weight percentage of the first additive is about 0.01%, about 0.05%, about 0.1%, about 0.5%, about 1%, about 2%, about 3%. %, about 5%, about 8%, about 10%, about 11%, or about 12%, etc.
  • the weight percentage of the lithium difluorophosphate is less than 1%. In some embodiments, based on the total weight of the electrolyte, the weight percentage of the lithium difluorophosphate is less than 0.5%.
  • the positive electrode of the electrochemical device includes a positive active material containing aluminum element, wherein the weight percentage of the aluminum element is 0.001%-1% based on the weight of the positive active material. In some embodiments, based on the weight of the positive active material, the weight percentage of aluminum is about 0.005%, about 0.01%, about 0.05%, about 0.08%, about 0.1%, about 0.5%, about 0.8%, 0.001% -0.05%, 0.001%-0.1%, 0.001%-0.5%, 0.01%-0.05%, 0.01%-0.1%, 0.01%-0.5% or 0.001%-0.05%, etc. In some embodiments, the positive active material includes lithium cobalt oxide doped with aluminum.
  • the positive active material aluminum element, it can stabilize the internal structure, thereby improving the electrochemical performance.
  • the weight percentage of aluminum element is less than 0.001%, the improvement effect of the positive electrode active material is not obvious; when the weight percentage of aluminum element is greater than 1%, the discharge capacity of the positive electrode active material will be deteriorated due to the excessively high doping amount, which is not conducive to electricity. Recycling and floating performance of chemical equipment.
  • the molar percentage A% of cyano groups in the electrolyte and the weight percentage C% of aluminum ions in the electrolyte satisfy: 0.01 ⁇ A/C ⁇ 170, which can effectively improve the cycle performance of the electrochemical device And floating charge performance.
  • A/C is less than 0.01, it is not obvious to stabilize the structure of the positive electrode active material and increase the corrosion resistance of the copper foil, and it is impossible to significantly improve the cycle and floating charge performance; when the A/C is greater than 170, the discharge capacity of the positive electrode active material is too low and electrical The polarization of the chemical device is too large, so that the cycle performance and floating charge performance cannot be improved.
  • the positive active material may be selected from lithium cobalt oxide, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, or any combination thereof.
  • the curve obtained by the differential scanning calorimetry test of the positive electrode active material includes a first exothermic peak and a second exothermic peak, wherein the first The temperature corresponding to the exothermic peak is X, 240°C ⁇ X ⁇ 280°C, and the temperature corresponding to the second exothermic peak is Y, 280°C ⁇ Y ⁇ 340°C.
  • the peak area of the first exothermic peak is ⁇ 50 J/g
  • the peak area of the second exothermic peak is ⁇ 800 J/g.
  • the positive electrode active material has more excellent thermal stability, so that the cycle performance and floating performance of the electrochemical device can be improved.
  • the positive active materials of the examples subjected to the DSC test are all fully discharged (de-lithium state) positive active materials.
  • Fig. 1 shows the DSC test curve of the positive electrode active material of Example 30.
  • the electrolyte further includes a second additive, the second additive includes a phosphorus-containing compound, and the phosphorus-containing compound includes trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, phosphoric acid Methyl diethyl, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tris(2,2, At least one of 2-trifluoroethyl) ester or tris(2,2,3,3,3-pentafluoropropyl)phosphate.
  • the second additive includes a phosphorus-containing compound
  • the phosphorus-containing compound includes trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, phosphoric acid Methyl diethyl, ethylene methyl phosphate, ethylene ethyl
  • the weight percentage of the second additive is 1% to 15%.
  • the electrolyte further includes a third additive
  • the third additive includes a fluorine-containing aromatic compound
  • the fluorine-containing aromatization includes fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, At least one of pentafluorobenzene, hexafluorobenzene, or trifluoromethylbenzene.
  • the weight percentage of the third additive is 1% to 15%.
  • the negative electrode used in the electrochemical device includes a negative electrode active material, and the specific type of the negative electrode active material is not subject to specific restrictions, and can be selected according to requirements.
  • the negative electrode active material can be selected from lithium metal, structured lithium metal, natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, Li -At least one of Sn 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 electrochemical device is a lithium ion secondary battery.
  • the capacity of the negative electrode active material capable of inserting and extracting lithium ions is preferably greater than the capacity of the positive electrode active material. Therefore, the amounts of the positive electrode active material and the negative electrode active material need to be adjusted accordingly to obtain a high energy density.
  • the ratio of the negative electrode capacity to the positive electrode capacity may be 1.01-1.2.
  • the electrochemical device of the present application is provided with a separator between the positive electrode and the negative electrode to prevent short circuits.
  • the material and shape of the isolation membrane used in the electrochemical device of the present application are not particularly limited, and it may be any technology 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 separator may include a porous substrate and a surface treatment layer.
  • the porous substrate is a non-woven fabric, film or composite film with a porous structure, and the material of the porous substrate is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide.
  • a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be selected.
  • a surface treatment layer is provided on at least one surface of the porous substrate.
  • the surface treatment layer may be a polymer layer or an inorganic substance layer, or a layer formed by a mixed polymer and an inorganic substance.
  • the inorganic layer includes inorganic particles and a binder.
  • the inorganic particles are selected from alumina, silica, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, One or a combination of yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.
  • the binder is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, One or a combination of polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
  • the polymer layer contains a polymer, and the material of the polymer includes polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly( At least one of vinylidene fluoride-hexafluoropropylene).
  • the electrochemical device of the present application is a lithium ion battery.
  • the positive electrode of the lithium ion battery includes a positive electrode current collector and a positive electrode active material layer coated on the positive electrode current collector, and the negative electrode includes a negative electrode current collector and a coating The negative active material layer on the negative current collector.
  • the electrochemical device described in this application is suitable for electronic devices in various fields.
  • the electrochemical device of the present application is not particularly limited, and it can be used for any purpose known in the prior art.
  • the electrochemical device of the present application can be used in, but not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, and headsets.
  • Lithium cobaltate doped with aluminum see Table 2 and Table 3 for the weight percentage of aluminum in specific examples
  • acetylene black and polyvinylidene fluoride in a weight ratio of 96:2:2 in an appropriate amount of N-methyl
  • the pyrrolidone solvent is fully stirred and mixed to form a uniform positive electrode slurry; the slurry is coated on the positive electrode current collector aluminum foil, dried, and cold pressed to obtain the positive electrode.
  • Isolation membrane A polyethylene porous film is used as the isolation membrane.
  • Preparation of lithium-ion battery stack the positive electrode, separator film, and negative electrode in order, so that the separator film is located between the positive electrode and the negative electrode for isolation, and then wind to obtain the electrode assembly; place the electrode assembly in the packaging case
  • the electrolyte prepared above is injected into the dried packaging shell, and the preparation of the lithium-ion battery is completed through the steps of vacuum packaging, standing, forming, and shaping.
  • the lithium ion batteries of Examples 1 to 55 and Comparative Example 1 were prepared according to the above preparation method, and the lithium ion battery was subjected to a high temperature cycle test, a float charge test, and a DSC test.
  • Disassemble the lithium-ion battery after discharging wash the disassembled positive pole piece with dimethyl carbonate (DMC) three times, dry it for 24 hours and perform a DSC test to obtain the DSC curve of the positive electrode active material, the position of the exothermic peak and The area of the exothermic peak.
  • DSC test procedure Take 3 mg of the dried sample and heat it from room temperature to 450°C at a rate of 10°C/min in a nitrogen atmosphere.
  • the electrolyte After discharging the lithium ion battery, the electrolyte is centrifuged, and the liquid obtained after centrifugation is tested by gas chromatography-mass spectrometry (GC-MS). The mass (M) of each nitrile compound is detected, and then the relative atomic mass (M0) of each nitrile compound is detected. Calculate the number of moles: M/M0 (mol), and use the same method to get the number of moles of other components in the electrolyte.
  • GC-MS gas chromatography-mass spectrometry
  • the cyano group content of a nitrile compound in the electrolyte is: (number of moles of nitrile compound/total number of moles of substances in the electrolyte)*number of cyano groups of a single nitrile compound molecule*100%.
  • the cyano group content in the electrolyte is the sum of the cyano group content of various nitrile compounds in the electrolyte.
  • ICP inductively coupled plasma spectroscopy
  • Table 1 shows the test results of the lithium ion batteries of Examples 1 to 22 and Comparative Example 1.
  • the electrolyte of Comparative Example 1 in Table 1 has no nitrile compound added, and its lithium-ion battery has a low high-temperature cycle capacity retention rate and a large floating charge thickness growth rate.
  • Table 2 shows the test results of the lithium ion batteries of Examples 23 to 29 and Example 16. The difference between Example 23-Example 29 and Example 16 lies in the data shown in the table.
  • Example 16 0 7.00 / 70.80% 16.30%
  • Example 23 0.05 7.00 140 72.30% 15.20%
  • Example 24 0.10 7.00 70 73.80% 14.80%
  • Example 25 0.30 7.00 twenty three 74.50% 14.10%
  • Example 26 0.50 7.00 14 74.60% 13.90%
  • Example 27 1 7.00 7 71.80% 16.10%
  • Example 28 1 1.40 1.4 71.20% 15.70%
  • Example 29 0.05 8.50 170 70.90% 15.90%
  • the positive electrode prepared with the positive electrode active material doped with aluminum element can effectively improve the high temperature cycle and floating charge performance of the lithium ion battery. This is because the Al-O bond is stronger than the Co-O bond.
  • the aluminum element can stabilize the structure of the positive electrode active material after lithium removal, improve the structure collapse, and improve the high temperature cycle of the lithium ion battery Performance and floating charge performance.
  • the weight percentage of aluminum element is increased to 1%, because the doping amount of aluminum element is too high, the discharge capacity of the positive electrode will be deteriorated, thereby weakening the improvement effect of the high temperature cycle and floating charge performance of the lithium ion battery.
  • the ratio When the ratio is lower than 0.01, the cyano group content is too low, it is not obvious to stabilize the structure of the positive electrode active material and increase the corrosion resistance of the copper foil, and cannot significantly improve the cycle and floating charge performance; when the ratio is higher than 170, the positive electrode is active The content of aluminum in the material is too low, and the content of cyano in the electrolyte is too high, resulting in the discharge capacity of the positive electrode active material is too low and the polarization of the lithium ion battery is too large, thereby making the high temperature cycle and floating charge performance of the lithium ion battery The improvement effect is weakened.
  • Table 3 shows the test results of the lithium ion batteries of Examples 16, 25, 30 to 38 and Comparative Example 1. The difference between Example 30 to Example 37 and Example 25 lies in the data shown in the table.
  • the DSC test curves of the positive electrode active materials of Example 25 and Examples 30 to 36 include at least two exothermic peaks, and the temperature X corresponding to the first exothermic peak: 240°C ⁇ X ⁇ 280°C, The peak area of the first exothermic peak ⁇ 50J/g; the temperature Y corresponding to the second exothermic peak: 280°C ⁇ Y ⁇ 340°C, and the peak area of the second exothermic peak ⁇ 800J/g.
  • Table 4 shows the test results of the lithium ion batteries of Examples 38 to 57 and Example 25.
  • the compound of formula IV and/or the first additive was further added to the electrolyte.
  • references to “some embodiments”, “partial embodiments”, “one embodiment”, “another example”, “examples”, “specific examples” or “partial examples” throughout the specification mean 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 “exemplified”, 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

一种电化学装置及包括其的电子装置。所述电化学装置包含正极、负极、隔离膜及电解液，其中所述电解液包含腈化合物和过渡金属离子，并满足：5≤A/B≤30000，其中以电解液的摩尔量计，所述电解液中的氰基的摩尔百分比为A％，以电解液的重量计，电解液中的过渡金属离子的重量百分比为B％。所述电化学装置通过确定电解液中氰基与过渡金属离子满足一定的关系来减少正极活性物质的过渡金属离子溶出并稳定正极活性物质在充放电过程中的结构畸变，从而改善电化学装置的高温循环性能及浮充性能。

Description

电化学装置及包括其的电子装置 技术领域
本申请涉及储能技术领域，尤其涉及电化学装置及包括其的电子装置。
背景技术
电化学装置(例如，锂离子电池)因其具有高工作电压、高能量密度、环境友好、循环稳定、安全等优点，被广泛应用于穿戴设备、智能手机、无人机，笔记本电脑等领域。随着现代信息技术的发展及锂离子电池应用的拓展，对锂离子电池提出了更高的要求，即高的能量密度、长的循环寿命以及优异的储存特性。电解液与正负极之间的相互作用会影响这些性能，特别是为改善锂离子电池的能量密度将工作电压提升至4.4V时，电解液及正极活性物质界面的不稳定性加剧，锂离子电池在高温下气胀严重，循环性能及充放电性能降低，严重制约了锂离子电池性能的发挥。为改善锂离子电池的特性，现有锂离子电池技术通常单一优化电解液或改善正极活性物质，而缺少对整个锂离子电池体系的深入探究，从而无法实现锂离子电池性能的整体提升。
发明内容
本申请提供一种电化学装置以试图在至少某种程度上解决至少一个存在于相关领域中的问题。
本申请通过在电解液中加入腈化合物并调整电解液中氰基含量与过渡金属离子含量之间的关系来优化整个电化学装置体系，从而改善电化学装置的高温循环性能及浮充性能。另外，本申请还研究了正极活性物质中掺杂元素的含量和电解液中氰基含量的关系对电化学装置的高温循环性能及浮充性能影响。
根据本申请的实施例，本申请提供了一种电化学装置，其包含正极、负极、隔离膜及电解液，其中所述电解液包含腈化合物和过渡金属离子，并满足：5≤A/B≤30000，其中，以所述电解液的总摩尔量计，所述电解液中氰基的摩尔百分比为A％，以所述电解液的总重量计，所述电解液中的所述过渡金属离子的重量百分比为B％。
根据本申请的实施例，在本申请的电化学装置中，所述过渡金属离子包括铁离子、钴离子、镍离子、锰离子或铜离子中的至少一种。
根据本申请的实施例，在本申请的电化学装置中，所述过渡金属离子包括钴离子或铜离子中的至少一种。
根据本申请的实施例，在本申请的电化学装置中，腈化合物包含式I化合物、式II化合物或式III化合物中的至少一种：
Figure PCTCN2021081455-appb-000001
其中R 1选自取代或未取代的C 1至C 10亚烷基、取代或未取代的C 1至C 10亚烷氧基、取代或未取代的C 2至C 10亚烯基、取代或未取代的C 6至C 12亚芳基、取代或未取代的C 6至C 10亚环烷基，其中经取代时，取代基选自卤素、氰基或羧基中的至少一种；其中R 21、R 22、R 23各自独立地选自单键、取代或未取代的C 1至C 5亚烷基、取代或未取代的C 1至C 10亚烷氧基，其中经取代时，取代基选自卤素、氰基或羧基中的至少一种；其中，R 31选自取代或未取代的C 1至C 5的亚烷基、取代或未取代的C 1至C 5的亚烷氧基、取代或未取代的C 2至C 10的亚烯基、取代或未取代的C 3至C 6的亚环烷基、取代或未取代的C 6至C 10的亚芳基、取代或未取代的C 1至C 6的亚杂环基团，其中经取代时，取代基选自卤素、氰基或羧基中的至少一种，其中亚杂环基团中的杂原子选自O、N、P或S中的至少一种。
根据本申请的实施例，以所述电解液的总重量计，所述电解液中的所述钴离子的重量百分比小于等于0.1％，所述电解液中的所述铜离子的重量百分比小于等于0.1％。
根据本申请的实施例，所述正极包含正极活性物质，所述正极活性物质中含有铝元素，其中以所述正极活性物质的总重量计，所述铝元素的重量百分比为C％，所述C的 数值范围为：0.001<C<1。
根据本申请的实施例，所述A与所述C满足如下关系：0.01≤A/C≤170。
根据本申请的实施例，所述正极活性物质经过差示扫描量热法测试得到的曲线包含第一放热峰和第二放热峰，其中所述第一放热峰对应的温度为X，240℃≤X≤280℃，所述第二放热峰对应的温度为Y，280℃＜Y≤340℃。
根据本申请的实施例，所述第一放热峰的峰面积≤50J/g，所述第二放热峰的峰面积≤800J/g。
根据本申请的实施例，电解液还包含式IV化合物：
Figure PCTCN2021081455-appb-000002
其中R 41选自取代或未取代的C 1至C 12烷基、取代或未取代的C 3至C 12环烷基、取代或未取代的C 2至C 12烯基、取代或未取代的C 2至C 12炔基、取代或未取代的C 6至C 22芳基、取代或未取代的C 5至C 22杂芳基，其中经取代时，取代基选自卤素、氰基或羧基中的至少一种；其中以所述电解液的重量计，所述式IV化合物的重量百分比为0.001％至5％。
根据本申请的实施例，电解液还包含第一添加剂，所述第一添加剂包含乙烯基碳酸乙烯酯、氟苯、二氟磷酸锂、四氟硼酸锂、1,3,2-二噁唑噻吩-2,2-二氧化物、氟代碳酸乙烯酯、碳酸亚乙烯酯或1,3-丙烷磺酸内酯中的至少一种，以所述电解液的总重量计，所述第一添加剂的重量百分比为0.001％至13％。
在本申请的电化学装置中，通过确定电解液中氰基与过渡金属离子满足一定的关系，以减少正极活性物质的过渡金属离子溶出并稳定正极活性物质在充放电过程中的结构畸变，从而改善电化学装置的高温循环性能及浮充性能。
根据本申请的实施例，本申请还提供了一种电子装置，所述电子装置包含上述任一种电化学装置。
本申请实施例的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
附图说明
在下文中将简要地说明为了描述本申请实施例或现有技术所必要的附图以便于描述本申请的实施例。显而易见地，下文描述中的附图仅只是本申请中的部分实施例。对本领域技术人员而言，在不需要创造性劳动的前提下，依然可以根据这些附图中所例示的结构来获得其他实施例的附图。
图1为本申请实施例30的正极活性物质的差示扫描量热法(DSC)测试曲线图。
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。在本申请说明书全文中，将相同或相似的组件以及具有相同或相似的功能的组件通过类似附图标记来表示。在此所描述的有关附图的实施例为说明性质的、图解性质的且用于提供对本申请的基本理解。本申请的实施例不应该被解释为对本申请的限制。
如本文中所使用，术语“大致”、“大体上”、“实质”及“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±10％的变化范围，例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％。举例来说，如果两个数值之间的差值小于或等于所述值的平均值的±10％(例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％)，那么可认为所述两个数值“大体上”相同。
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。
在具体实施方式及权利要求书中，由术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A或B中的至少一者”意味着仅A；仅B；或 A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B或C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个组分或多个组分。项目B可包含单个组分或多个组分。项目C可包含单个组分或多个组分。
术语“烷基”预期是具有1至20个碳原子的直链饱和烃结构。“烷基”还预期是具有3至20个碳原子的支链或环状烃结构。例如，烷基可为1至20个碳原子的烷基、1至10个碳原子的烷基、1至5个碳原子的烷基、5至20个碳原子的烷基、5至15个碳原子的烷基或5至10个碳原子的烷基。当指定具有具体碳数的烷基时，预期涵盖具有该碳数的所有几何异构体；因此，例如，“丁基”意思是包括正丁基、仲丁基、异丁基、叔丁基和环丁基；“丙基”包括正丙基、异丙基和环丙基。烷基实例包括，但不限于甲基、乙基、正丙基、异丙基、环丙基、正丁基、异丁基、仲丁基、叔丁基、环丁基、正戊基、异戊基、新戊基、环戊基、甲基环戊基、乙基环戊基、正己基、异己基、环己基、正庚基、辛基、环丙基、环丁基、降冰片基等。另外，烷基可以是任选地被取代的。
如本文所用，术语“亚烷基”意指直链或具支链的二价饱和烃基。例如，亚烷基可为1至20个碳原子的亚烷基、1至15个碳原子的亚烷基、1至10个碳原子的亚烷基、1至5个碳原子的亚烷基、5至20个碳原子的亚烷基、5至15个碳原子的亚烷基或5至10个碳原子的亚烷基。代表性亚烷基包括(例如)亚甲基、乙烷-1,2-二基(“亚乙基”)、丙烷-1,2-二基、丙烷-1,3-二基、丁烷-1,4-二基、戊烷-1,5-二基等等。另外，亚烷基可以是任选地被取代的。
术语“环烷基”涵盖环状烷基。环烷基可为3至20个碳原子的环烷基、6至20个碳原子的环烷基、3至10个碳原子的环烷基、3至6个碳原子的环烷基。例如，环烷基可为环丙基、环丁基、环戊基、环己基等。另外，环烷基可以是任选地被取代的。
术语“亚环烷基”单独地或作为另一个取代基的一部分意指衍生自环烷基的二价自由基。
术语“烯基”是指可为直链或具支链且具有至少一个且通常1个、2个或3个碳碳双键的单价不饱和烃基团。除非另有定义，否则所述烯基通常含有2-20个碳原子，例如可以为2至20个碳原子的烯基、6至20个碳原子的烯基、2至10个碳原子的烯基或2至6个碳原子的烯基。代表性烯基包括(例如)乙烯基、正丙烯基、异丙烯基、正-丁-2-烯基、丁-3-烯基、正-己-3-烯基等。另外，烯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。当指定具有具体碳数的亚烯基时，预期涵盖具有该碳数的所有几何异构体。例如，亚烯基可为2至20个碳原子的亚烯基、2至15个碳原子的亚烯基、2至10个碳原子的亚烯基、2至5个碳原子的亚烯基，5至20个碳原子的亚烯基、5至15个碳原子的亚烯基、或5至10个碳原子的亚烯基。代表性亚烷基包括(例如)亚乙烯基、亚丙烯基、亚丁烯基等。另外，亚烯基可以是任选地被取代的。
术语“炔基”是指可为直链或具支链且具有至少一个且通常具有1个、2个或3个碳碳三键的单价不饱和烃基团。除非另有定义，否则所述炔基通常含有2个到20个碳原子，例如可以为2至20个碳原子的炔基、6至20个碳原子的炔基、2至10个碳原子的炔基或2至6个碳原子的炔基。代表性炔基包括(例如)乙炔基、丙-2-炔基(正-丙炔基)、正-丁-2-炔基、正-己-3-炔基等。另外，炔基可以是任选地被取代的。
术语“烷氧基”指L-O-基团，其中L为烷基。本文中烷氧基可为1至12个碳原子的烷氧基，还可以为1至10个碳原子的烷氧基、1至5个碳原子的烷氧基、5至12个碳原子的烷氧基或5至10个碳原子的烷氧基。
术语“亚烷氧基”单独地或作为另一个取代基的一部分意指衍生自烷氧基的二价自由基。
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至C 50芳基、C 6至C 40芳基、C 6至C 30芳基、C 6至C 20芳基或C 6至C 10芳基。代表性芳基包括(例如)苯基、甲基苯基、丙基苯基、异丙基苯基、苯甲基和萘-1-基、萘-2-基等等。另外，芳基可以是任选地被取代的。
术语“亚芳基”单独地或作为另一个取代基的一部分意指衍生自芳基的二价自由基。
术语“杂芳基”涵盖可以包括一到三个杂原子的单环杂芳香族基团，例如吡咯、呋喃、噻吩、咪唑、噁唑、噻唑、三唑、吡唑、吡啶、吡嗪和嘧啶等。术语杂芳基还包括具有其中两个原子为两个邻接环(所述环是“稠合的”)共用的两个或更多个环的多环杂芳香族系统，其中所述环中的至少一者是杂芳基，其它环可以是环烷基、环烯基、芳基、杂环和/或杂芳基。例如杂芳基可为C 6至C 50杂芳基、C 6至C 40杂芳基、C 6至C 30 杂芳基、C 6至C 20杂芳基或C 6至C 10杂芳基。另外，杂芳基可以是任选地被取代的。
术语“杂环基”涵盖芳香族和非芳香族环状基团。杂芳香族环状基团还意指杂芳基。在一些实施例中，杂芳香族环基团和杂非芳香族环基团为包括至少一个杂原子的C 1至C 50杂环基、C 1至C 40杂环基、C 1至C 30杂环基、C 1至C 20杂环基、C 1至C 10杂环基、C 1至C 6杂环基。例如吗啉基、哌啶基、吡咯烷基等，以及环醚，例如四氢呋喃、四氢吡喃等。另外，杂环基可以是任选地被取代的。
术语“亚杂环基”单独地或作为另一个取代基的一部分意指衍生自杂环基的二价自由基。
如本文所用，术语“杂原子”涵盖O、S、P、N、B或其电子等排体。
如本文所用，术语“卤素”可为F、Cl、Br或I。
一、电化学装置
本申请提供了一种电化学装置，所述电化学装置包含正极、负极、隔离膜及电解液，其中，电化学装置的电解液包含腈化合物和过渡金属离子，并满足：5≤A/B≤30000，其中以电解液的总摩尔量计，所述电解液中的氰基的摩尔百分比为A％，以电解液的总重量计，电解液中的过渡金属离子的总重量百分比为B％。
在一些实施例中，所述过渡金属离子包括铁离子、钴离子、镍离子、锰离子或铜离子中的至少一种。
在一些实施例中，所述过渡金属离子包括钴离子或铜离子中的至少一种。
在一些实施例中，腈化合物包含式I化合物、式II化合物或式III化合物中的至少一种：
Figure PCTCN2021081455-appb-000003
在式I中，R 1选自取代或未取代的C 1至C 10亚烷基、取代或未取代的C 1至C 10亚烷氧基、取代或未取代的C 2至C 10亚烯基，取代或未取代的C 6至C 12亚芳基、取代或未取代的C 6至C 10亚环烷基，其中经取代时，取代基选自卤素、氰基或羧基中的至少一种。
在式II中，R 21、R 22、R 23各自独立地选自单键、取代或未取代的C 1至C 5亚烷基、取代或未取代的C 1至C 10亚烷氧基，其中经取代时，取代基选自卤素、氰基或羧基中的至少一种。
在式III中，R 31选自取代或未取代的C 1至C 5的亚烷基、取代或未取代的C 1至C 5的亚烷氧基、取代或未取代的C 2至C 10的亚烯基、取代或未取代的C 3至C 6的亚环烷基、取代或未取代的C 6至C 10的亚芳基、取代或未取代的C 1至C 6的亚杂环基团，其中经取代时，取代基选自卤素、氰基或羧基中的至少一种，其中亚杂环基团中的杂原子选自O、N、P或S中的至少一种。
在一些实施例中，结构式为式I的腈化合物可以包含，但不限于，丙二腈、丁二腈、戊二腈、己二腈、庚二腈、辛二腈、壬二腈、葵二腈、甲基丙二腈、乙基丙二腈、异丙基丙二腈、叔丁基丙二腈、甲基丁二腈、2,2-二甲基丁二腈、2,3-二甲基丁二腈、2,3,3-三甲基丁二腈、2,2,3,3-四甲基丁二腈、2,3-二乙基-2,3-二甲基丁二腈、2,2-二乙基-3,3-二甲基丁二腈、双环己基-1,1-二甲腈、双环己基-2,2-二甲腈、双环己基-3,3-二甲腈、2,5-二甲基-2,5-己烷二甲腈、2,3-二异丁基-2,3-二甲基丁二腈、2,2-二异丁基-3,3-二甲基丁二腈、2-甲基戊二腈、2,3-二甲基戊二腈、2,4-二甲基戊二腈、2,2,3,3-四甲基戊二腈、2,2,4,4-四甲基戊二腈、2,2,3,4-四甲基戊二腈、2,3,3,4-四甲基戊二腈、马来腈、富马腈、1,4-二氰基戊烷、2,6-二氰基庚烷、2,7-二氰基辛烷、2,8-二氰基壬烷、1,6-二氰基癸烷、1,2-二氰基苯、1,3-二氰基苯、1,4-二氰基苯中的至少一种。
在一些实施例中，结构式为式II的腈化合物可以包含
Figure PCTCN2021081455-appb-000004
Figure PCTCN2021081455-appb-000005
中的至少一种。
在一些实施例中，结构式为式III的腈化合物可以包含
Figure PCTCN2021081455-appb-000006
Figure PCTCN2021081455-appb-000007
中的至少一种。
在一些实施例中，过渡金属离子包括钴(Co)离子或铜(Cu)离子中的至少一种，其中以电解液的重量计，钴离子的重量百分比小于等于约0.1％，铜离子的重量百分比小于等于约0.1％。在一些实施例中，以电解液的重量计，钴离子的重量百分比小于等于约0.08％、小于等于约0.05％、小于等于约0.03％、小于等于约0.02％或小于等于约0.001％。在一些实施例中，以电解液的重量计，铜离子的重量百分比小于等于约0.08％、小于等于约0.05％、小于等于约0.03％、小于等于约0.02％或小于等于约0.001％。
当电解液中钴离子的重量百分比为小于等于0.1％时，电化学装置能够保持较优的循环性能及浮充性能。当电解液中钴离子的重量百分比超过0.1％时，正极活性物质结构被破坏，导致正极活性物质中的过渡金属离子溶出，通过电解液沉积到负极并催化负极保护膜的分解，恶化电化学装置的性能。
在电化学装置中，负极集流体为铜箔，在化成前铜箔没有被覆盖保护，暴露在电解液中，容易受到电解液的腐蚀，铜箔氧化成为铜离子溶解到电解液中；在化成充电过程中，铜离子还原为铜沉积到负极，催化负极固体电解质界面(SEI)膜的分解，恶化电化学装置的性能。当铜离子的重量百分比为小于等于0.1％时，对电化学装置性能的影响无明显的差异，当铜离子的重量百分比超过0.1％时，将恶化电化学装置的电化学性能。
当电化学装置的充电上限电压提升至4.4V时，过渡金属钴离子溶出量增加，正极活性物质的结构稳定性变差，电化学装置的循环性能及浮充性能会变差。而本申请的电化学装置可以在充电上限电压提升至4.4V时仍然保持良好的高温循环性能和浮充性能。本申请的腈化合物可以有效地将电解液中易氧化组分与正极活性物质隔开，从而稳定正极活性物质的结构，降低正极活性物质中过渡金属离子的溶出，从而改善电化学装置的 高温循环和浮充性能。
另外，腈化合物可以在负极(例如，暴露的铜箔表面)形成稳定的聚合物，从而保护负极界面，缓解铜箔的腐蚀，从而改善高温存储及浮充性能。电解液中氰基的摩尔百分比A％与电解液中的第一金属离子的总重量百分比B％满足如下的比例关系：5≤A/B≤30000。当A/B在此范围内电化学装置会具有良好的高温循环和浮充性能。
在一些实施例中，为了进一步改进电化学装置的性能，电解液还可以包含式IV化合物
Figure PCTCN2021081455-appb-000008
在式IV中，R 41选自取代或未取代的C 1至C 12烷基、取代或未取代的C 3至C 12环烷基、取代或未取代的C 2至C 12烯基、取代或未取代的C 2至C 12炔基、取代或未取代的C 6至C 22芳基、取代或未取代的C 5至C 22杂芳基，其中经取代时，取代基选自卤素、氰基或羧基中的至少一种；其中以所述电解液的总重量计，所述式IV化合物的含量为0.001％至5％。
在一些实施例中，式IV化合物包含
Figure PCTCN2021081455-appb-000009
Figure PCTCN2021081455-appb-000010
中的至少一种。
在一些实施例中，所述电解液还包含第一添加剂，所述第一添加剂包含乙烯基碳酸乙烯酯(VEC)、氟苯、二氟磷酸锂(LiPO 2F 2)、四氟硼酸锂、1,3,2-二噁唑噻吩-2,2-二氧化物(DTD)、氟代碳酸乙烯酯(FEC)、碳酸亚乙烯酯(VC)或1,3-丙烷磺酸内酯(PS)中的至少一种。在一些实施例中，以所述电解液的重量计，所述第一添加剂的 重量百分比为约0.01％至约13％。在一些实施例中，基于所述电解液的总重量，所述第一添加剂的重量百分比为约0.01％、约0.05％、约0.1％、约0.5％、约1％、约2％、约3％、约5％、约8％、约10％、约11％或约12％等。
在一些实施例中，以所述电解液的总重量计，所述二氟磷酸锂的重量百分比为小于1％。在一些实施例中，以所述电解液的总重量计，所述二氟磷酸锂的重量百分比为小于0.5％。
在一些实施例中，电化学装置的正极包含正极活性物质，所述正极活性物质中含有铝元素，其中以正极活性物质的重量计，铝元素的重量百分比为0.001％-1％。在一些实施例中，以正极活性物质的重量计，铝元素的重量百分比为约0.005％、约0.01％、约0.05％、约0.08％、约0.1％、约0.5％、约0.8％、0.001％-0.05％、0.001％-0.1％、0.001％-0.5％、0.01％-0.05％、0.01％-0.1％、0.01％-0.5％或0.001％-0.05％等。在一些实施例中，所述正极活性物质包含掺杂铝元素的钴酸锂。
当正极活性物质铝元素后，能够稳定内部结构，从而改善电化学性能。当铝元素的重量百分比小于0.001％时，正极活性物质的改善作用不明显；当铝元素的重量百分比大于1％时，由于掺杂量过高，将恶化正极活性物质的放电容量，不利于电化学装置的循环及浮充性能。
在一些实施例中，电解液中的氰基的摩尔百分比A％与电解液中的铝离子的重量百分比C％满足：0.01≤A/C≤170，从而能够有效地改善电化学装置的循环性能及浮充性能。当A/C小于0.01时，稳定正极活性物质结构及增加铜箔抗腐蚀性能不明显，无法明显提升循环及浮充性能；当A/C大于170时，正极活性物质的放电容量过低及电化学装置的极化过大，从而无法提升循环性能及浮充性能。
在一些实施例中，正极活性物质可以选自钴酸锂、镍钴锰酸锂、镍钴铝酸锂或它们的任意组合。在一些实施例中，为进一步提升电化学装置的性能，所述正极活性物质经过差示扫描量热法测试得到的曲线包含第一放热峰和第二放热峰，，其中所述第一放热峰对应的温度为X，240℃≤X≤280℃，所述第二放热峰对应的温度为Y，280℃＜Y≤340℃。在一些实施例中，所述第一放热峰的峰面积≤50J/g，所述第二放热峰的峰面积≤800J/g。当其满足上述条件时，正极活性物质具有更优异的热稳定性，从而可以提升电化学装置的循环性能及浮充性能。在本申请的实施例中，进行DSC测试的实施例的正极活性物质均为满放(脱锂态)正极活性物质。图1示出了实施例30的正极活性物质的DSC测 试曲线。在一些实施例中，所述电解液还包含第二添加剂，所述第二添加剂包含含磷化合物，所述含磷化合物包含磷酸三甲酯、磷酸三乙酯、磷酸二甲基乙酯、磷酸甲基二乙酯、磷酸亚乙基甲酯、磷酸亚乙基乙酯、磷酸三苯酯、亚磷酸三甲酯、亚磷酸三乙酯、亚磷酸三苯酯、磷酸三(2,2,2-三氟乙基)酯或磷酸三(2,2,3,3,3-五氟丙基)酯中的至少一种。
在一些实施例中，以所述电解液的总重量计，所述第二添加剂的重量百分比为1％至15％。
在一些实施例中所述电解液还包含第三添加剂，所述第三添加剂包含含氟芳香族化合物，所述含氟芳香族化包括氟苯、二氟苯、三氟苯、四氟苯、五氟苯、六氟苯或三氟甲基苯中的至少一种。
在一些实施例中，以所述电解液的总重量计，所述第三添加剂的重量百分比为1％至15％。
在一些实施例中，电化学装置中使用的负极包括负极活性物质，负极活性物质的具体种类均不受到具体的限制，可根据需求进行选择。具体地，所述负极活性物质可以选自锂金属、结构化的锂金属、天然石墨、人造石墨、中间相微碳球(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。
在一些实施例中，电化学装置为锂离子二次电池。为了防止在充电时锂金属无意地析出在负极上，能够插入和脱出锂离子的负极活性物质的容量优选大于正极活性物质的容量。因此，需要相应地调节正极活性物质和负极活性物质的量，以获得高的能量密度。在一些实施例中，负极容量与正极容量之比可以为1.01-1.2。
在一些实施例中，本申请的电化学装置在正极与负极之间设有隔离膜以防止短路。本申请的电化学装置中使用的隔离膜材料和形状没有特别限制，其可为任何现有技术中公开的技术。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。
例如隔离膜可包括多孔基材和表面处理层。多孔基材为具有多孔结构的无纺布、膜或复合膜，多孔基材的材料选自聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯或聚酰亚胺中的至少一种。具体的，可选用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。
多孔基材的至少一个表面上设置有表面处理层，表面处理层可以是聚合物层或无机 物层，也可以是混合聚合物与无机物所形成的层。
无机物层包括无机颗粒和粘结剂，无机颗粒选自氧化铝、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。聚合物层中包含聚合物，聚合物的材料包括聚酰胺、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、聚偏氟乙烯或聚(偏氟乙烯-六氟丙烯)中的至少一种。
在一些实施例中，本申请的电化学装置是锂离子电池，所述锂离子电池的正极包括正极集流体及涂布在正极集流体上的正极活性物质层，负极包括负极集流体及涂布在负极集流体上的负极活性物质层。
二、电子装置
由本申请所述的电化学装置适用于各种领域的电子装置。
本申请的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。在一个实施例中，本申请的电化学装置可用于，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。
三、实施例
以下说明根据本申请的锂离子电池的实施例和对比例进行性能评估。
锂离子电池的制备
(1)负极的制备：将人造石墨、丁苯橡胶、羧甲基纤维素钠按照重量比97.4:1.2:1.4在适量的去离子水溶剂中充分搅拌混合，使其形成均匀的负极浆料；将此浆料涂覆于负极集流体铜箔上，烘干、冷压得到负极活性物质层，焊接极耳得到负极。
(2)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、碳酸 丙烯酯、碳酸二乙酯，按照3:3:4的质量比混合均匀，再将充分干燥的六氟磷酸锂溶解于上述非水溶剂，形成基础电解液，其中六氟磷酸锂的浓度为1mol/L。在基础电解液中加入如下各表中所示的不同含量的物质得到不同实施例和对比例的电解液。
(3)正极的制备：
实施例1-22和对比例1的正极的制备：
将钴酸锂、乙炔黑、聚偏二氟乙烯按重量比96:2:2在适量的N-甲基吡咯烷酮溶剂中充分搅拌混合，使其形成均匀的正极浆料；将此浆料涂覆于正极集流体铝箔上，烘干、冷压得到正极活性物质层，焊接极耳得到正极。
实施例23-57的正极的制备：
将铝元素掺杂的钴酸锂(具体实施例中铝元素的重量百分比见表2和表3)、乙炔黑、聚偏二氟乙烯按重量比96:2:2在适量的N-甲基吡咯烷酮溶剂中充分搅拌混合，使其形成均匀的正极浆料；将此浆料涂覆于正极集流体铝箔上，烘干、冷压，得到正极。
(4)隔离膜：以聚乙烯多孔薄膜作为隔离膜。
(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起到隔离的作用，然后卷绕得到电极组件；将电极组件置于包装壳中，将上述制备好的电解液注入到干燥后的包装壳中，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。
测试方法
按照上述制备方法制备实施例1至55以及对比例1的锂离子电池，并对锂离子电池进行高温循环测试、浮充测试和DSC测试。
高温循环测试
将锂离子电池放置45℃恒温箱中，以恒定电流1.5C充电至4.4V，4.4V下恒压充电至0.05C，再以1.0C恒流放电至3.0V，此时为首次充放电循环。按上述方式进行500次循环充放电测试，监控容量保持率，容量保持率＝剩余放电容量/初始放电容量*100％。
浮充测试
将锂离子电池放置45℃恒温箱中，以恒定电流1.5C充电至4.4V，记录此时的初始厚度(D0)，4.4V下恒压充电至0.05C，再以0.05C小电流恒流充电1500h，记录浮充结束后厚度 (D1)，监控浮充过程中厚度增长率，厚度增长率＝(D1-D0)/D0*100％。
DSC测试
将锂离子电池放电后拆解，将拆解后的正极极片用碳酸二甲酯(DMC)清洗三次，干燥24h后进行DSC测试即可得到正极活性物质的DSC曲线、放热峰的位置及放热峰的面积。DSC测试步骤：取干燥后的试样3mg，在氮气气氛下，以10℃/min的速率从室温加热至450℃。
电解液中氰基含量的计算方法
将锂离子电池放电后离心电解液，离心后得到的液体进行气相色谱-质谱(GC-MS)测试，检测出各腈化合物的质量(M)，再根据各腈化合物的相对原子质量(M0)计算出其摩尔数即：M/M0(mol)，采用同样的方法可得到电解液其他成分的摩尔数。电解液中的一种腈化合物的氰基含量即为：(腈化合物摩尔数/电解液中物质总摩尔数)*单个腈化合物分子的氰基数量*100％。电解液中的氰基含量为电解液中各种腈化合物的氰基含量总和。
电解液中过渡金属离子含量的测试方法
将锂离子电池放电后离心，离心后得到的液体进行电感耦合等离子光谱(ICP)测试即可得到电解液中过渡金属离子(例如，钴离子和铜离子)的重量百分含量。
测试结果
表1示出了实施例1至22以及对比例1的锂离子电池的测试结果。
表1
Figure PCTCN2021081455-appb-000011
Figure PCTCN2021081455-appb-000012
Figure PCTCN2021081455-appb-000013
表1中的对比例1的电解液没有添加腈化合物，其锂离子电池的高温循环容量保持率低，浮充厚度增长率大。
通过对比实施例1至7与对比例1可以得知，在电解液中添加腈化合物可有效地改善锂离子电池的高温循环性能和浮充性能。这是由于腈化合物中的氰基可在正极活性物质表面与过渡金属进行络合，降低过渡金属的溶出，从而改善锂离子电池的高温循环性能及浮充性能。从实施例8至11可知，在电解液中添加腈化合物可改善高温循环及浮充性能，但当腈化合物的重量百分比增加至10％时，其改善效果减弱，这主要是由于腈化合物含量增大，导致锂离子电池极化增加，因此高温存储及浮充改善效果会有所减弱。
从实施例12至15与对比例1对比可知，当电解液中铜离子含量增加至0.1％时，电解液中的铜离子会破坏负极结构的稳定性，即使增大电极液中的氰基含量，也无法缓解铜箔腐蚀，因此会使高温循环及浮充性能的改善效果减弱。
通过对比实施例16至18与对比例1可知，当电解液中钴离子的含量增加至0.1％时，正极活性物质开始受到明显破坏，即使增大电解液中的氰基含量，也无法有效地保护正极活性物质，因此会使高温循环及浮充性能的改善效果减弱。
从实施例19-22与对比例1对比可知，当电解液中A/B的数值范围在5≤A/B≤30000 时，锂离子电池具有较优的高温循环及浮充性能。
表2示出了实施例23至29以及实施例16的锂离子电池的测试结果。实施例23-实施例29与实施例16的差异在于表中所示数据。
表2
  C(wt％) A(mol％) A/C 容量保持率 厚度增长率
实施例16 0 7.00 / 70.80％ 16.30％
实施例23 0.05 7.00 140 72.30％ 15.20％
实施例24 0.10 7.00 70 73.80％ 14.80％
实施例25 0.30 7.00 23 74.50％ 14.10％
实施例26 0.50 7.00 14 74.60％ 13.90％
实施例27 1 7.00 7 71.80％ 16.10％
实施例28 1 1.40 1.4 71.20％ 15.70％
实施例29 0.05 8.50 170 70.90％ 15.90％
通过对比实施例23至28与实施例16可以得知，采用铝元素掺杂的正极活性物质制备的正极可有效地改善锂离子电池的高温循环及浮充性能。这是由于Al-O键强大于Co-O键，当正极活性物质掺杂铝元素后，铝元素能够稳定脱锂后的正极活性物质的结构，改善结构坍塌，从而改善锂离子电池的高温循环性能及浮充性能。但当铝元素的重量百分比增大至1％时，由于铝元素的掺杂量过高，会恶化正极放电容量，从而减弱锂离子电池的高温循环及浮充性能的改善效果。
通过实施例27-29与实施例16相比，所述电解液中的氰基含量与正极活性物质中的铝元素含量满足0.01≤A/C≤170关系时，能够有效改善锂离子电池的高温循环性能及浮充性能。当其比值低于0.01时，氰基含量过低，稳定正极活性物质的结构及增加铜箔抗腐蚀性能不明显，无法显著地提升循环及浮充性能；当其比值高于170时，正极活性物质中的铝元素含量过低、电解液中的氰基含量过高，导致正极活性物质的放电容量过低及锂离子电池极化过大，从而使锂离子电池的高温循环及浮充性能的改善效果减弱。
表3示出实施例16、25、30至38以及对比例1的锂离子电池的测试结果。实施例30至实施例37与实施例25的差异在于表中所示数据。
表3
Figure PCTCN2021081455-appb-000014
根据表3可以得知，实施例25以及实施例30至36的正极活性物质的DSC测试曲线至少包含2个放热峰，第一放热峰对应的温度X：240℃≤X≤280℃，第一放热峰的峰面积≤50J/g；第二放热峰对应的温度Y：280℃＜Y≤340℃，第二放热峰的峰面积≤800J/g。与对比例1相比，实施例25以及实施例30至36的正极活性物质的放热峰推迟且放热面积降低，因此其正极活性物质的热稳定性较好，从而可以有效地改善锂离子电池的高温循环性能及浮充性能。
表4示出了实施例38至57以及实施例25的锂离子电池的测试结果。实施例38至57是在实施例25的基础上，在电解液中进一步添加式IV化合物和/或第一添加剂。
表4
Figure PCTCN2021081455-appb-000015
Figure PCTCN2021081455-appb-000016
由表4可以得知，在电解液中添加式IV化合物和/或第一添加剂可以进一步改善锂离子电池的高温循环性能及浮充性能。
整个说明书中对“一些实施例”、“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，其包含正极、负极、隔离膜及电解液，
    其中所述电解液包含腈化合物和过渡金属离子，并满足：5≤A/B≤30000，
    其中，以所述电解液的总摩尔量计，所述电解液中氰基的摩尔百分比为A％，以所述电解液的总重量计，所述电解液中的所述过渡金属离子的重量百分比为B％。
  2. 根据权利要求1所述的电化学装置，其中所述过渡金属离子包括铁离子、钴离子、镍离子、锰离子或铜离子中的至少一种。
  3. 根据权利要求1所述的电化学装置，其中所述腈化合物包含式I化合物、式II化合物或式III化合物中的至少一种：
    Figure PCTCN2021081455-appb-100001
    其中R 1选自取代或未取代的C 1至C 10亚烷基、取代或未取代的C 1至C 10亚烷氧基、取代或未取代的C 2至C 10亚烯基、取代或未取代的C 6至C 12亚芳基、取代或未取代的C 6至C 10亚环烷基，其中经取代时，取代基选自卤素、氰基或羧基中的至少一种；
    其中R 21、R 22、R 23各自独立地选自单键、取代或未取代的C 1至C 5亚烷基、取代或未取代的C 1至C 10亚烷氧基，其中经取代时，取代基选自卤素、氰基或羧基中的至少一种；
    其中，R 31选自取代或未取代的C 1至C 5的亚烷基、取代或未取代的C 1至C 5的亚烷氧基、取代或未取代的C 2至C 10的亚烯基、取代或未取代的C 3至C 6的亚环烷基、取代或未取代的C 6至C 10的亚芳基、取代或未取代的C 1至C 6的亚杂环基团，其中经取代时，取代基选自卤素、氰基或羧基中的至少一种，其中亚杂环基团中的杂原子选自O、N、P或S中的至少一种。
  4. 根据权利要求2所述的电化学装置，其中以所述电解液的总重量计，所述电解液中的所述钴离子的重量百分比小于等于0.1％，所述电解液中的所述铜离子的重量百分比小于等于0.1％。
  5. 根据权利要求1所述的电化学装置，其中所述正极包含正极活性物质，所述正极活性物质中含有铝元素，其中以所述正极活性物质的总重量计，所述铝元素的重量百分比为C％，所述C的数值范围为：0.001<C<1。
  6. 根据权利要求5所述的电化学装置，其中所述A与所述C满足如下关系：0.01≤A/C≤170。
  7. 根据权利要求5所述的电化学装置，其中所述正极活性物质经过差示扫描量热法测试得到的曲线包含第一放热峰和第二放热峰，其中所述第一放热峰对应的温度为X，240℃≤X≤280℃，所述第二放热峰对应的温度为Y，280℃＜Y≤340℃。
  8. 根据权利要求7所述的电化学装置，其中所述第一放热峰的峰面积≤50J/g，所述第二放热峰的峰面积≤800J/g。
  9. 根据权利要求1所述的电化学装置，其中所述电解液还包含式IV化合物：
    Figure PCTCN2021081455-appb-100002
    其中R 41选自取代或未取代的C 1至C 12烷基、取代或未取代的C 3至C 12环烷基、取代或未取代的C 2至C 12烯基、取代或未取代的C 2至C 12炔基、取代或未取代的C 6至C 22芳基、取代或未取代的C 5至C 22杂芳基，其中经取代时，取代基选自卤素、氰基或羧基中的至少一种；其中以所述电解液的总重量计，所述式IV化合物的重量百分比为0.001％至5％。
  10. 根据权利要求1所述的电化学装置，其中所述电解液还包含第一添加剂，所述第一添加剂包含乙烯基碳酸乙烯酯、氟苯、二氟磷酸锂、四氟硼酸锂、1,3,2-二噁唑噻吩-2,2-二氧化物、氟代碳酸乙烯酯、碳酸亚乙烯酯或1,3-丙烷磺酸内酯中的至少一种，以所述电解液的总重量计，所述添加剂的重量百分比为0.001％至13％。
  11. 一种电子装置，其包含根据权利要求1-10中任一权利要求所述的电化学装置。
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