WO2023225897A1 - 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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WO2023225897A1
WO2023225897A1 PCT/CN2022/094915 CN2022094915W WO2023225897A1 WO 2023225897 A1 WO2023225897 A1 WO 2023225897A1 CN 2022094915 W CN2022094915 W CN 2022094915W WO 2023225897 A1 WO2023225897 A1 WO 2023225897A1
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electrochemical device
positive electrode
negative electrode
electrolyte
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PCT/CN2022/094915
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French (fr)
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王翔
王蕊
唐超
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宁德新能源科技有限公司
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Priority to PCT/CN2022/094915 priority Critical patent/WO2023225897A1/zh
Priority to CN202280007272.7A priority patent/CN116802873A/zh
Publication of WO2023225897A1 publication Critical patent/WO2023225897A1/zh
Priority to US18/619,623 priority patent/US20240250304A1/en

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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
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C255/00—Carboxylic acid nitriles
    • C07C255/01—Carboxylic acid nitriles having cyano groups bound to acyclic carbon atoms
    • C07C255/02—Carboxylic acid nitriles having cyano groups bound to acyclic carbon atoms of an acyclic and saturated carbon skeleton
    • C07C255/04—Carboxylic acid nitriles having cyano groups bound to acyclic carbon atoms of an acyclic and saturated carbon skeleton containing two cyano groups bound to the carbon skeleton
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C255/00—Carboxylic acid nitriles
    • C07C255/01—Carboxylic acid nitriles having cyano groups bound to acyclic carbon atoms
    • C07C255/02—Carboxylic acid nitriles having cyano groups bound to acyclic carbon atoms of an acyclic and saturated carbon skeleton
    • C07C255/05—Carboxylic acid nitriles having cyano groups bound to acyclic carbon atoms of an acyclic and saturated carbon skeleton containing at least three cyano groups bound to the carbon skeleton
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
    • C07C69/02—Esters of acyclic saturated monocarboxylic acids having the carboxyl group bound to an acyclic carbon atom or to hydrogen
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
    • C07C69/02—Esters of acyclic saturated monocarboxylic acids having the carboxyl group bound to an acyclic carbon atom or to hydrogen
    • C07C69/12—Acetic acid esters
    • C07C69/14—Acetic acid esters of monohydroxylic compounds
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
    • C07C69/02—Esters of acyclic saturated monocarboxylic acids having the carboxyl group bound to an acyclic carbon atom or to hydrogen
    • C07C69/22—Esters of acyclic saturated monocarboxylic acids having the carboxyl group bound to an acyclic carbon atom or to hydrogen having three or more carbon atoms in the acid moiety
    • C07C69/24—Esters of acyclic saturated monocarboxylic acids having the carboxyl group bound to an acyclic carbon atom or to hydrogen having three or more carbon atoms in the acid moiety esterified with monohydroxylic compounds
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
    • C07C69/96—Esters of carbonic or haloformic acids
    • 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
    • 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
    • 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
    • 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
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • 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
    • 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
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0034—Fluorinated solvents
    • 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

  • the present application relates to the field of energy storage technology, and more specifically, to an electrochemical device and an electronic device including the same.
  • Rechargeable electrochemical devices are considered to be one of the most attractive energy storage systems due to their advantages such as high energy density and relatively simple reaction mechanism, high operating voltage, long life, and green environmental protection.
  • electrochemical devices such as lithium-ion batteries have been widely used in electronic products such as laptops, smartphones, and wearable devices.
  • this application improves the fast charging performance and high temperature interval cycle performance of the electrochemical device by improving the formula composition of the electrolyte and/or designing the size of the electrochemical device.
  • the application provides an electrolyte solution
  • the electrolyte solution includes a carboxylate compound represented by formula (I) and fluorinated ethylene carbonate (FEC),
  • R 11 includes hydrogen, hydroxyl group, C1-C20 alkyl group, C1-C20 alkoxy group, C2-C20 chain alkenyl group, C6-C30 aryl group, or C6-C30 aryloxy group.
  • At least one of R 12 includes at least one of a C1-C20 alkyl group, a C2-C20 chain alkenyl group, or a C6-C30 aryl group;
  • the contents of the carboxylate compound represented by formula (I) and the FEC are w 1 and w 2 respectively, 5% ⁇ w 1 ⁇ 60%, 2% ⁇ w 2 ⁇ 12%, and 2 ⁇ w 1 /w 2 ⁇ 20.
  • the carboxylate compound represented by formula (I) includes at least one of the following: methyl acetate, ethyl acetate, propyl acetate, methyl propionate, propionic acid Ethyl ester, n-propyl propionate, isopropyl propionate, n-butyl propionate, isobutyl propionate, n-amyl propionate, isoamyl propionate, ethyl n-butyrate, n-propyl n-butyrate ester, propyl isobutyrate, n-amyl n-butyrate, n-amyl isobutyrate, n-butyl n-butyrate, isobutyl isobutyrate or n-amyl n-valerate.
  • the carboxylic acid ester compound represented by formula (I) includes propyl propionate and ethyl acetate.
  • the electrolyte further includes nitrile compounds, and based on the total weight of the electrolyte, the content of the nitrile compound is w 3 , 0.1% ⁇ w 3 ⁇ 12%.
  • the nitrile compound includes at least one of the compounds represented by formula (II) to formula (V):
  • R 21 includes at least one of a substituted or unsubstituted C1-C12 alkylene group or a substituted or unsubstituted C1-C12 alkyleneoxy group;
  • R 31 and R 32 each independently include hydrogen and a substituted or unsubstituted C1-C12 alkylene group
  • R 41 , R 42 , and R 43 each independently include hydrogen, a substituted or unsubstituted C1-C12 alkylene group or a substituted or unsubstituted C1-C12 alkyleneoxy group;
  • R 51 includes substituted or unsubstituted C1-C12 alkylene, substituted or unsubstituted C2-C12 alkenylene, substituted or unsubstituted C6-C26 arylene or substituted or unsubstituted C2-C12 Heterocyclic group, in which the heteroatom is at least one of N, S or O;
  • the substituent When substituted, the substituent is halogen.
  • the total molar amount of cyano groups (-CN) in the nitrile compound is x
  • the total molar amount of the nitrile compound is y
  • the cyano group enrichment x/y satisfies 2.16 ⁇ x/y ⁇ 2.71.
  • the cyano group enrichment x/y, the content w 1 of the carboxylate compound represented by the formula (I) and the content w 2 of the FEC satisfy 2w 1 2 -0.01 w 1 +2.3>x/y>27w 2 2 -1.2w 2 +2.1.
  • the electrolyte includes a lithium salt
  • the lithium salt includes at least one of the following: LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4. LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 , LiC(SO 2 CF 3 ) 3 , LiSiF 6 , LiBOB or LiDFOB.
  • the present application also provides an electrochemical device, which includes the electrolyte solution described in the above embodiments of the present application.
  • the electrochemical device further includes a positive electrode, a negative electrode and a separator located between the positive electrode and the negative electrode, wherein the positive electrode, the negative electrode and the separator are wound to A battery core is formed, the length L and width W of the battery core satisfy 20mm ⁇ L ⁇ 300mm, 20mm ⁇ W ⁇ 100mm, and 1 ⁇ L/W ⁇ 4.
  • the electrochemical device satisfies at least one of the following characteristics: a).1 ⁇ L/W ⁇ 3; b) 2 ⁇ L/W ⁇ 3; c) 2 ⁇ L/ W ⁇ 4.
  • the electrochemical device further includes a positive electrode, a negative electrode and a separator located between the positive electrode and the negative electrode, wherein the positive electrode, the negative electrode and the separator are wound to A battery core is formed, the thickness T and width W of the battery core satisfy 2mm ⁇ T ⁇ 12mm, and W/T ⁇ 5.
  • the electrochemical device satisfies at least one of the following characteristics: d).5 ⁇ W/T ⁇ 25; e)5 ⁇ W/T ⁇ 20; f)5 ⁇ W/ T ⁇ 15; g)10 ⁇ W/T ⁇ 25.
  • the electrochemical device further includes a positive electrode, a negative electrode and a separator located between the positive electrode and the negative electrode, wherein the positive electrode, the negative electrode and the separator are wound to An electric core is formed, and the length L and width W of the electric core and the content w 1 of the carboxylic acid ester compound represented by the formula (I) satisfy w 1 ⁇ 100/(L/W) ⁇ 10.
  • the electrochemical device satisfies at least one of the following characteristics: h).10 ⁇ w 1 ⁇ 100/(L/W) ⁇ 40; i).20 ⁇ w 1 ⁇ 100 /(L/W) ⁇ 30; j)20 ⁇ w 1 ⁇ 100/(L/W) ⁇ 40; k).15 ⁇ w 1 ⁇ 100/(L/W) ⁇ 30.
  • the present application also provides an electronic device, which includes the electrochemical device described in the above embodiments of the present application.
  • Figure 1 shows a graph of the relationship between the cyano concentration x/y and the content w 1 of the carboxylic acid ester compound.
  • Figure 2 shows the relationship between the cyano enrichment x/y and the content w2 of fluoroethylene carbonate (FEC).
  • Figure 3 shows the length L, width W and thickness T of the battery core after packaging.
  • a list of items connected by the term “one or more of,” “one or more of,” “at least one of” or other similar terms may mean with any combination of the items listed.
  • the phrase “at least one of A or B” means only A; only B; or both A and B.
  • 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 (excluding B); B and C (excluding A); or all of A, B and C.
  • Item A may contain a single component or multiple components.
  • Item B may contain a single component or multiple components.
  • Item C may contain a single component or multiple components.
  • alkyl encompasses both straight and branched chain alkyl groups.
  • the alkyl group can be C1-C50 alkyl, C1-C40 alkyl, C1-C30 alkyl, C1-C20 alkyl, C1-C12 alkyl, C1-C10 alkyl, C1-C6 alkyl, C2- C6 alkyl, C2-C5 alkyl.
  • alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, and the like. Additionally, alkyl groups may be optionally substituted.
  • alkenyl encompasses both straight and branched chain alkenyl groups.
  • the alkenyl group may be C2-C50 alkenyl, C2-C40 alkenyl, C2-C30 alkenyl, C2-C20 alkenyl, C2-C12 alkenyl, C2-C10 alkenyl, C2-C6 alkenyl. Additionally, 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 common to two adjacent rings (the rings are "fused"), wherein at least one of the rings is aromatic, such as other
  • the ring may be cycloalkyl, cycloalkenyl, aryl, heterocycle and/or heteroaryl.
  • the aryl group may be C6-C50 aryl, C6-C40 aryl, C6-C30 aryl, C6-C20 aryl or C6-C10 aryl. Additionally, aryl groups may be optionally substituted.
  • alkoxy refers to an organic group having -O-R1, where R1 is the linear or branched alkyl group mentioned above.
  • aryloxy refers to an organic group having -O-R2, where R2 is the aryl group mentioned above.
  • alkylene encompasses both straight and branched chain alkylene groups.
  • the alkylene group can be C1-C50 alkylene, C1-C40 alkylene, C1-C30 alkylene, C1-C20 alkylene, C1-C10 alkylene, C1-C6 alkylene, C2 -C6 alkylene, C2-C5 alkylene. Additionally, alkylene groups may be optionally substituted.
  • alkenylene encompasses both straight chain and branched chain alkenylene groups.
  • the alkenylene group can be C2-C50 alkenylene, C2-C40 alkenylene, C2-C30 alkenylene, C2-C20 alkenylene, C2-C10 alkenylene, C1-C6 alkenylene, C2 -C6 alkenylene. Additionally, alkenylene groups may be optionally substituted.
  • heterocyclylene group includes closed ring structures similar to carbocyclic groups in which one or more of the ring carbon atoms are non-carbon elements, such as nitrogen, sulfur, or oxygen, including but not limited to aziridine groups , ethylene oxide group (epoxide, ethylene oxide), ethylene sulfide (group episulfide), bis-oxirane group, azetidine group, oxetane Alkyl group, thietane group, dioxetane group, dithietane group, dithiobutene group, azepane group, pyrrolidine group , pyrroline group, oxolane group, dihydrofuran group and furan group, etc.
  • aziridine groups ethylene oxide group (epoxide, ethylene oxide), ethylene sulfide (group episulfide), bis-oxirane group, azetidine group, oxetane Alkyl group, thietane group, di
  • the substituents may be independently selected from alkyl, alkenyl, aryl, alkoxy, aryloxy, silyl, siloxanyl, amino, ether, ester, carboxyl, Sulfonic acid group, mercapto group, cyano group, halogen or combinations thereof.
  • the electrolyte is used to transport lithium ions between the positive and negative electrodes to realize the continuous insertion and extraction of lithium ions in the positive and negative electrode materials, thereby performing the functions of charging and discharging. Therefore, the electrolyte has a crucial impact on the electrochemical performance of electrochemical devices.
  • this application adds a carboxylic acid ester compound with a lower viscosity to the electrolyte to increase the transmission rate of lithium ions in the electrolyte.
  • carboxylic acid ester compounds with a lower viscosity to the electrolyte to increase the transmission rate of lithium ions in the electrolyte.
  • this application further found that the electrochemical window of carboxylic acid ester compounds is narrow and has poor high-temperature stability. For example, when electronic devices (e.g., laptop computers) are stored at high temperatures and under intermittent conditions of charge and discharge cycles, carboxylate compounds will react at the negative electrode, consuming active lithium and destroying the solid electrolyte interface (SEI) film on the surface of the negative electrode. , causing rapid attenuation of battery capacity.
  • SEI solid electrolyte interface
  • this application further adds fluorinated ethylene carbonate (FEC) to the electrolyte.
  • FEC fluorinated ethylene carbonate
  • the present application further found that when the electrochemical device is under high-temperature storage and intermittent conditions of charge and discharge cycles, the positive electrode structure is easily damaged and an oxygen release reaction occurs. At this time, FEC is easily oxidized and decomposed to produce CO 2 , resulting in electrolyte The chemical unit is bulging.
  • the present application unexpectedly found that by adjusting the content and ratio of the carboxylic acid ester compound and FEC in the electrolyte, the fast charging performance of the electrochemical device can be effectively improved without deteriorating or minimizing the deterioration of the electrochemical device. High temperature interval cycling performance.
  • the contents of the carboxylate compound and FEC are w 1 and w 2 respectively, where 5% ⁇ w 1 ⁇ 60%, 2% ⁇ w 2 ⁇ 12%, and 2 ⁇ w 1 /w 2 ⁇ 20.
  • w 1 can be, but is not limited to, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, or 60%, Or within the range consisting of any two of the above values. For example, 10% ⁇ w 1 ⁇ 50% or 15% ⁇ w 1 ⁇ 50%.
  • w 2 may be, but is not limited to, 2%, 4%, 6%, 8%, 10%, or 12%, or within a range consisting of any two of the above values. For example, 4% ⁇ w 2 ⁇ 12% or 4% ⁇ w 1 ⁇ 10%.
  • w 1 /w 2 can be, but is not limited to, 2, 4, 6, 8, 10, 12, 14, 16, 18 or 20, or within a range consisting of any two of the above values. .
  • the carboxylate compound is a carboxylate compound represented by the following formula (I),
  • R 11 includes hydrogen, hydroxyl group, C1-C20 alkyl group, C1-C20 alkoxy group, C2-C20 chain alkenyl group, C6-C30 aryl group, or C6-C30 aryloxy group.
  • At least one of R 12 includes at least one of a C1-C20 alkyl group, a C2-C20 chain alkenyl group, or a C6-C30 aryl group.
  • the carboxylate compound represented by formula (I) includes at least one of the following: methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propionic acid n-propyl propionate, isopropyl propionate, n-butyl propionate, isobutyl propionate, n-amyl propionate, iso-amyl propionate, ethyl n-butyrate, n-propyl n-butyrate, isobutyric acid Propyl ester, n-amyl n-butyrate, n-amyl isobutyrate, n-butyl n-butyrate, isobutyl isobutyrate, or n-amyl n-valerate.
  • the carboxylate compound represented by formula (I) includes at least propyl propionate.
  • propyl propionate is more beneficial to stabilizing the cathode structure. Therefore, while improving the fast charging performance of the electrochemical device, it can also improve its high-temperature ITC performance and suppress gas production, thereby improving the electrochemical performance. Overall performance of the device.
  • the carboxylic acid ester compound represented by formula (I) includes ethyl propionate and ethyl acetate. In some embodiments, the carboxylic acid ester compound represented by formula (I) includes propyl propionate and ethyl acetate. In some embodiments, the carboxylic acid ester compound represented by formula (I) includes propyl propionate and ethyl propionate. In some embodiments, the carboxylate compounds represented by formula (I) include ethyl acetate, ethyl propionate and propyl propionate.
  • the electrolyte further includes nitrile compounds.
  • nitrile compounds contain cyano (-CN) functional groups.
  • the content of the nitrile compound is w 3 , and 0.1% ⁇ w 3 ⁇ 12%.
  • w 3 can be, but is not limited to, 0.1%, 1%, 2%, 4%, 6%, 8%, 10% or 12%, or in a range consisting of any two of the above values Inside.
  • the high-temperature ITC performance of the electrochemical device can be improved and gas production can be suppressed while taking into account the fast charging performance of the electrochemical device.
  • nitrile compounds can form a nitrile protective film with excellent performance on the surface of the cathode, which can well stabilize the active metal in the cathode active material, inhibit the dissolution of the active metal, and reduce the oxygen release reaction.
  • nitrile compounds include at least one of the compounds represented by formula (II) to formula (V):
  • R 21 includes at least one of a substituted or unsubstituted C1-C12 alkylene group or a substituted or unsubstituted C1-C12 alkyleneoxy group;
  • R 31 and R 32 each independently include hydrogen and a substituted or unsubstituted C1-C12 alkylene group
  • R 41 , R 42 , and R 43 each independently include hydrogen, a substituted or unsubstituted C1-C12 alkylene group or a substituted or unsubstituted C1-C12 alkyleneoxy group;
  • R 51 includes substituted or unsubstituted C1-C12 alkylene, substituted or unsubstituted C2-C12 alkenylene, substituted or unsubstituted C6-C26 arylene or substituted or unsubstituted C2-C12 Heterocyclic group, in which the heteroatom is at least one of N, S or O;
  • the substituent When substituted, the substituent is halogen.
  • nitrile compounds include adiponitrile, succinonitrile, glutaronitrile, malononitrile, 2-methylglutaronitrile, pimelonitrile, sebaconitrile, azelonitrile, 1,4- Dicyano-2-butene, ethylene glycol bis(propionitrile) ether, 3,3′-oxydipropionitrile, thiomalononitrile, hex-2-enedonitrile, butenedonitrile, 2- Glutenedonitrile, ethylsuccinonitrile, hex-3-enedonitrile, 2-methyleneglutaronitrile, 4-cyanopimelonitrile, 1,3,6-hexanetrinitrile, 1,3 , at least one of 5-hexanetricarbonitrile, 1,2,3-propanetricarbonitrile or 1,2,3-tris(2-cyanooxy)propane.
  • cyano group enrichment is the total molar amount of cyano groups (-CN) in nitrile compounds x and the total molar amount of nitrile compounds The ratio between y.
  • cyano group enrichment is the total molar amount of cyano groups (-CN) in nitrile compounds x and the total molar amount of nitrile compounds The ratio between y.
  • the degree x/y satisfies 2.16 ⁇ x/y ⁇ 2.71
  • it can significantly improve the high-temperature ITC performance of the electrochemical device and inhibit gas production.
  • the electrochemical device when the electrochemical device satisfies 2w 1 2 -0.01w 1 +2.3>x/y>27w 2 2 -1.2w 2 +2.1, the fast charging performance and high-temperature ITC performance of the electrochemical device can be simultaneously improved and production can be suppressed. gas.
  • the electrolyte solution described herein further includes a lithium salt.
  • lithium salts may include, but are not limited to, inorganic lithium salts such as LiPF 6 , LiBF 4 , LiClO 4 , LiAlF 4 , LiSbF 6 , and LiWF 7 ; lithium tungstates such as LiWOF 5 ; HCO 2 Li, CH 3 CO 2 Li , CH 2 FCO 2 Li, CHF 2 CO 2 Li, CF 3 CO 2 Li, CF 3 CH 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li and other lithium carboxylate salts; FSO 3 Li, CH 3 SO 3 Li, CH 2 FSO 3 Li, CHFSO 3 Li, CHF 2 SO 3 Li, CF 3 SO 3 Li, CF 3 CF 2 SO 3 Li, CF 3 CF 2 CF 2 SO 3 Li, CF 3 CF 2 CF
  • (malonate) Lithium borate salts lithium tris(malonate) phosphate, lithium difluorobis(malonate) phosphate, lithium tetrafluoro(malonate) phosphate and other (malonate) lithium phosphate salts; and LiPF 4 (CF 3 ) 2 , LiPF 4 (C 2 F 5 ) 2 , LiPF 4 (CF 3 SO 2 ) 2 , LiPF 4 (C 2 F 5 SO 2 ) 2 , LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiBF 3 C 3 F 7 , LiBF 2 (CF 3 ) 2 , LiBF 2 (C 2 F 5 ) 2 , LiBF 2 (CF 3 SO 2 ) 2 , LiBF 2 (C 2 F 5 SO 2 ) 2, etc.
  • Fluorine organic lithium salts such as lithium difluoroxaloborate and lithium bis(oxalate)borate; lithium tetrafluorooxalatophosphate, lithium difluorobis(oxalato)phosphate, and tris(oxalato) Lithium phosphate and other oxalate lithium phosphate salts, etc.
  • the lithium salt includes at least one of the following: LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN (SO 2 CF 3 ) 2 , LiC(SO 2 CF 3 ) 3 , LiSiF 6 , LiBOB or LiDFOB.
  • the content of the lithium salt is 0.01wt% to 20wt%, 0.01wt% to 10wt%, 0.01wt% to 5wt%, 0.01wt% to 3wt%, 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 electrolyte further includes any non-aqueous solvent known in the art that can serve as a solvent for the electrolyte.
  • the non-aqueous solvent includes, but is not limited to, one or more of the following: cyclic carbonate, chain carbonate, cyclic ether, chain ether, phosphorus-containing organic solvent, Sulfur organic solvents and aromatic fluorinated solvents.
  • examples of the cyclic carbonate may include, but are not limited to, one or more of: ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate.
  • the cyclic carbonate has 3-6 carbon atoms.
  • examples of the chain carbonate may include, but are not limited to, one or more of the following: dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl carbonate Chain carbonates such as n-propyl carbonate, ethyl n-propyl carbonate, di-n-propyl carbonate, etc.
  • chain carbonates substituted by fluorine may include, but are not limited to, one or more of the following: bis(fluoromethyl)carbonate, bis(difluoromethyl)carbonate, bis(trifluoromethyl)carbonate base) carbonate, bis(2-fluoroethyl) carbonate, bis(2,2-difluoroethyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 2-fluoroethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate and 2,2,2-trifluoroethyl methyl carbonate, etc.
  • examples of the cyclic ether may include, but are not limited to, one or more of the following: tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl 1,3-dioxolane, 4-methyl 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane and dimethoxypropane.
  • examples of the chain ether may include, but are not limited to, one or more of the following: dimethoxymethane, 1,1-dimethoxyethane, 1,2- Dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxy Methoxyethane and 1,2-ethoxymethoxyethane, etc.
  • examples of the phosphorus-containing organic solvent may include, but are not limited to, one or more of the following: trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl phosphate Diethyl ester, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, triethyl phosphite, triphenyl phosphite, tris (2,2,2-trifluoroethyl) phosphate ester and tris(2,2,3,3,3-pentafluoropropyl) phosphate, etc.
  • examples of the sulfur-containing organic solvent may include, but are not limited to, one or more of the following: sulfolane, 2-methyl sulfolane, 3-methyl sulfolane, dimethyl sulfone, dimethyl sulfolane, Ethyl sulfone, ethyl methyl sulfone, methyl propyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate or ethyl ethanesulfonate.
  • some hydrogen atoms of the sulfur-containing organic solvent may be replaced by fluorine.
  • the aromatic fluorinated solvent includes, but is not limited to, one or more of the following: fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene and trifluoromethylbenzene.
  • the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer contains a positive electrode active material.
  • the cathode active material layer may be one or more layers, and each layer of the multiple layers of cathode active material may contain the same or different cathode active materials.
  • the positive active material is any material that can reversibly insert and detach metal ions such as lithium ions.
  • the type of positive electrode active material is not particularly limited as long as it can electrochemically absorb and release metal ions (for example, lithium ions).
  • the positive active material is a material containing lithium and at least one transition metal.
  • the positive active material may include, but are not limited to, lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.
  • the transition metal in the lithium transition metal composite oxide includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc.
  • lithium transition metal composite oxides include lithium cobalt composite oxides such as LiCoO 2 , lithium nickel composite oxides such as LiNiO 2 , lithium manganese composite oxides such as LiMnO 2 , LiMn 2 O 4 , Li 2 MnO 4 , etc.
  • LiNi 1/3 Mn 1/3 Co 1/3 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 and other lithium nickel manganese cobalt composite oxides in which some of the transition metal atoms that are the main body of these lithium transition metal composite oxides are Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W and other elements replaced .
  • lithium transition metal composite oxides may include, but are not limited to, LiNi 0.5 Mn 0.5 O 2 , LiNi 0.85 Co 0.10 Al 0.05 O 2 , LiNi 0.33 Co 0.33 Mn 0.33 O 2 , LiNi 0.45 Co 0.10 Al 0.45 O 2 , LiMn 1.8 Al 0.2 O 4 and LiMn 1.5 Ni 0.5 O 4 etc.
  • combinations of lithium transition metal composite oxides include, but are not limited to, a combination of LiCoO 2 and LiMn 2 O 4 , in which part of the Mn in LiMn 2 O 4 may be replaced by a transition metal (for example, LiNi 0.33 Co 0.33 Mn 0.33 O 2 ), part of Co in LiCoO 2 can be replaced by transition metals.
  • the transition metal in the lithium-containing transition metal phosphate compound includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc.
  • lithium-containing transition metal phosphate compounds include iron phosphates such as LiFePO 4 , Li 3 Fe 2 (PO 4 ) 3 , LiFeP 2 O 7 , etc., and cobalt phosphates such as LiCoPO 4 , wherein as these lithium transition metal phosphate compounds Part of the main transition metal atoms are replaced by other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc.
  • a substance having a different composition may be attached to the surface of the positive electrode active material.
  • surface-attached substances may include, but are not limited to: oxides such as aluminum oxide, silica, titanium dioxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide; lithium sulfate, sodium sulfate, potassium sulfate , magnesium sulfate, calcium sulfate, aluminum sulfate and other sulfates; lithium carbonate, calcium carbonate, magnesium carbonate and other carbonates; carbon, etc.
  • a substance By adhering a substance to the surface of the positive electrode active material, the oxidation reaction of the electrolyte on the surface of the positive electrode active material can be suppressed, thereby increasing the life of the electrochemical device.
  • the amount of the substance attached to the surface is too small, the effect cannot be fully expressed; when the amount of the substance attached to the surface is too much, it hinders the entry and exit of lithium ions, so the resistance may increase.
  • a positive electrode active material in which a substance different in composition is attached to the surface of the positive electrode active material is also referred to as a "positive electrode active material.”
  • the "positive electrode active material” preferably uses lithium cobalt oxide or lithium nickel cobalt manganate.
  • the shapes of the positive active material particles include, but are not limited to, block, polyhedral, spherical, ellipsoidal, plate, needle, and columnar shapes.
  • the positive active material particles include primary particles, secondary particles, or combinations thereof.
  • primary particles can agglomerate to form secondary particles.
  • the positive electrode also includes a positive conductive material to increase the conductivity of the positive electrode.
  • the type of positive conductive material is not limited, and any known conductive material can be used.
  • Examples of the positive conductive material may include, but are not limited to, graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; amorphous carbon such as needle coke and other carbon materials; carbon nanotubes; graphene, etc.
  • the above-mentioned positive conductive materials can be used alone or in any combination.
  • the type of solvent used to form the positive electrode slurry is not limited as long as it is a solvent that can dissolve or disperse the positive electrode active material, the conductive material, the positive electrode binder, and a thickener used as necessary.
  • the solvent used to form the positive electrode slurry may include any of an aqueous solvent and an organic solvent.
  • aqueous media may include, but are not limited to, water, mixed media of alcohol and water, and the like.
  • organic media may include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; acetone, methylethane Ketones such as base ketone and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N, N-dimethylaminopropylamine; diethyl ether, propylene oxide, tetrahydrofuran (THF) ) and other ethers; N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide and other amides; hexamethylphosphoramide, dimethyl sulfoxide and other aprotic polar solvents, etc.
  • aliphatic hydrocarbons such as hexane
  • aromatic hydrocarbons such as benz
  • Thickeners are usually used to adjust the viscosity of the slurry.
  • a thickener and styrene-butadiene rubber (SBR) emulsion can be used for slurrying.
  • SBR styrene-butadiene rubber
  • the type of thickener is not particularly limited, and examples thereof may include, but are not limited to, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, and phosphorylated starch , casein and their salts, etc.
  • the above thickeners can be used alone or in any combination.
  • the type of the positive electrode current collector is not particularly limited, and it can be any material known to be suitable for use as a positive electrode current collector.
  • positive electrode current collectors may include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; carbon materials such as carbon cloth and carbon paper.
  • the positive current collector is a metallic material.
  • the positive current collector is aluminum.
  • the surface of the positive electrode current collector may include a conductive additive.
  • conductive additives may include, but are not limited to, carbon and precious metals such as gold, platinum, and silver.
  • the positive electrode can be produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector.
  • the positive electrode using the positive electrode active material can be produced by a conventional method. That is, the positive electrode active material and the binder, as well as the conductive material and thickener if necessary, are dry-mixed into a sheet, and the resultant The sheet is pressed onto the positive electrode current collector; or these materials are dissolved or dispersed in a liquid medium to form a slurry, and the slurry is applied to the positive electrode current collector and dried to form a slurry on the current collector.
  • the positive electrode active material layer can be used to obtain a positive electrode.
  • the weight fraction of the cathode active material is M% based on the total weight of the cathode active material layer, where 90 ⁇ M ⁇ 99.5. In some embodiments, 95 ⁇ M ⁇ 99. In some embodiments, M may be 90, 92, 94, 95, 96, 97, 98, or 99, or within a range consisting of any two of the above values.
  • the energy density of the electrochemical device can be significantly increased.
  • the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer contains a negative electrode active material.
  • the negative active material layer may be one or more layers, and each layer of the multiple layers of negative active material may contain the same or different negative active materials.
  • the negative active material is any material that can reversibly insert and detach metal ions such as lithium ions.
  • the rechargeable capacity of the negative active material is greater than the discharge capacity of the positive active material to prevent lithium metal from unintentionally precipitating on the negative electrode during charging.
  • any known current collector can be used.
  • negative electrode current collectors include, but are not limited to, metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. In some embodiments, the negative current collector is copper.
  • the form of the negative electrode current collector may include, but is not limited to, metal foil, metal cylinder, metal strip roll, metal plate, metal film, metal mesh, stamped metal, foamed metal, etc.
  • the negative electrode current collector is a metal film.
  • the negative electrode current collector is copper foil.
  • the negative electrode current collector is a rolled copper foil based on a rolling method or an electrolytic copper foil based on an electrolysis method.
  • the thickness of the negative electrode current collector is greater than 1 ⁇ m or greater than 5 ⁇ m. In some embodiments, the thickness of the negative electrode current collector is less than 100 ⁇ m or less than 50 ⁇ m. In some embodiments, the thickness of the negative electrode current collector is within the range of any two of the above values.
  • the negative active material is not particularly limited as long as it can reversibly absorb and release lithium ions.
  • Examples of negative active materials may include, but are not limited to, carbon materials such as natural graphite and artificial graphite; metals such as silicon (Si) and tin (Sn); or oxides of metal elements such as Si and Sn.
  • the negative active materials can be used alone or in combination.
  • the negative electrode active material layer may further include a negative electrode binder.
  • the negative electrode binder can improve the binding between the negative electrode active material particles and the binding between the negative electrode active material and the current collector.
  • the type of negative electrode binder is not particularly limited as long as it is a material that is stable to the electrolyte or the solvent used in electrode production.
  • the negative electrode binder includes a resin binder.
  • resin binders include, but are not limited to, fluororesin, polyacrylonitrile (PAN), polyimide resin, acrylic resin, polyolefin resin, and the like.
  • the negative electrode binder includes, but is not limited to, carboxymethylcellulose (CMC) or its salt, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or Its salt, polyvinyl alcohol, etc.
  • CMC carboxymethylcellulose
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • Its salt polyvinyl alcohol, etc.
  • the negative electrode can be prepared by coating a negative electrode mixture slurry containing a negative electrode active material, a resin binder, etc. on a negative electrode current collector, drying it, and rolling it to form negative electrode active material layers on both sides of the negative electrode current collector. You can get the negative pole.
  • an isolation film is usually provided between the positive and negative electrodes.
  • the electrolyte of the present application is usually used by penetrating into the separator.
  • the isolation membrane may be resin, glass fiber, inorganic material, etc. formed of materials that are stable to the electrolyte of the present application.
  • the isolation film includes a porous sheet or a non-woven fabric-like material having excellent liquid retention properties.
  • materials for resin or fiberglass isolation membranes may include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, and the like.
  • the polyolefin is polyethylene or polypropylene.
  • the polyolefin is polypropylene.
  • the isolation film may also be a material formed by laminating the above materials. Examples thereof include, but are not limited to, a three-layer isolation film formed by laminating polypropylene, polyethylene, and polypropylene in this order.
  • inorganic materials may include, but are not limited to, oxides such as aluminum oxide and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates (for example, barium sulfate, calcium sulfate, etc.).
  • inorganic forms may include, but are not limited to, particulate or fibrous.
  • the isolation membrane may be in the form of a film, and examples thereof include, but are not limited to, non-woven fabrics, woven fabrics, microporous membranes, etc.
  • the isolation film has a pore diameter of 0.01 ⁇ m to 1 ⁇ m and a thickness of 5 ⁇ m to 50 ⁇ m.
  • separators may also be used: a separator formed by using a resin-based binder to form a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and/or the negative electrode,
  • a separator is formed by using fluororesin as a binder to form porous layers on both sides of the positive electrode with 90% alumina particles having a particle size less than 1 ⁇ m.
  • the thickness of the isolation film is arbitrary. In some embodiments, the thickness of the isolation film is greater than 1 ⁇ m, greater than 5 ⁇ m, or greater than 8 ⁇ m. In some embodiments, the thickness of the isolation film is less than 50 ⁇ m, less than 40 ⁇ m, or less than 30 ⁇ m. In some embodiments, the thickness of the isolation film is within a range consisting of any two of the above values. When the thickness of the isolation film is within the above range, insulation and mechanical strength can be ensured, and rate characteristics and energy density of the electrochemical device can be ensured.
  • the porosity of the separator is arbitrary.
  • the isolation membrane has a porosity greater than 10%, greater than 15%, or greater than 20%.
  • the isolation membrane has a porosity of less than 60%, less than 50%, or less than 45%.
  • the porosity of the isolation film is within a range consisting of any two of the above values. When the porosity of the isolation film is within the above range, insulation and mechanical strength can be ensured, and membrane resistance can be suppressed, so that the electrochemical device has good safety characteristics.
  • the average pore size of the isolation membrane is also arbitrary.
  • the isolation membrane has an average pore diameter of less than 0.5 ⁇ m or less than 0.2 ⁇ m. In some embodiments, the isolation membrane has an average pore size greater than 0.05 ⁇ m. In some embodiments, the average pore size of the isolation membrane is within the range consisting of any two of the above values. If the average pore diameter of the isolation film exceeds the above range, short circuit may easily occur. When the average pore diameter of the isolation membrane is within the above range, the electrochemical device has good safety characteristics.
  • the electrochemical device of the present application includes any device that undergoes electrochemical reactions, and specific examples thereof include lithium metal secondary batteries or lithium ion secondary batteries.
  • the electrochemical device of the present application includes the electrolyte solution mentioned in the above embodiment.
  • the applied electrochemical device further includes a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode.
  • electrochemical devices usually tend to have a narrow and long shape. Due to uneven current distribution and uneven SEI film formation in narrow and long batteries, lithium precipitation is more likely to occur at the upper and lower edges when charging at room temperature or low temperature, resulting in capacity attenuation. In addition, the precipitated lithium dendrites may also puncture the separator between the positive and negative electrodes, causing a short circuit in the battery, thereby causing safety issues.
  • the positive electrode, negative electrode, and separator are rolled to form a cell. In some embodiments, the positive electrode, negative electrode, and separator are laminated to form a cell.
  • the present application found that adjusting the size of the battery cell can increase the charging rate window of the electrochemical device, improve lithium deposition, and thereby improve the fast charging performance of the electrochemical device.
  • the length L and width W of the battery core satisfy 20mm ⁇ L ⁇ 300mm, 20mm ⁇ W ⁇ 100mm, and 1 ⁇ L/W ⁇ 4.
  • the length L of the battery core can be, but is not limited to, 20mm, 50mm, 75mm, 100mm, 125mm, 150mm, 175mm, 200mm, 225mm, 250mm, 275mm or 300mm, or any two of the above points. within the composition range.
  • the width W of the battery core may be, but is not limited to, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm or 100 mm, or within the range of any two of the above points.
  • the aspect ratio L/W of the cell may be, but is not limited to, 1, 2, 3, or 4, or be within the range consisting of any two of the above-mentioned point values.
  • the thickness T of the battery core satisfies 2mm ⁇ T ⁇ 12mm. In some embodiments, the thickness T of the battery core may be, but is not limited to, 2, 4, 6, 8, 10, or 12, or within a range consisting of any two of the above values. In some embodiments, the width and thickness ratio W/T of the cell satisfies W/T ⁇ 5. In some embodiments, the width and thickness ratio W/T of the cell satisfies W/T ⁇ 25. In some embodiments, W/T may be, but is not limited to, 5, 10, 15, 20, or 25, or within a range consisting of any two point values mentioned above.
  • the charge rate window of the electrochemical device can be further increased, lithium evolution can be improved, and the fast charging performance of the electrochemical device can be further improved.
  • the length L and width W of the battery core and the content w 1 of the carboxylate compound represented by formula (I) satisfy w 1 ⁇ 100/(L/W) ⁇ 10.
  • the length L and width W of the battery core and the content w 1 of the carboxylic acid ester compound represented by formula (I) satisfy w 1 ⁇ 100/(L/W) ⁇ 40.
  • w 1 ⁇ 100/(L/W) may be, but is not limited to, 10, 15, 20, 25, 30, 35 or 40, or within the range consisting of any two point values mentioned above.
  • the present application further provides an electronic device, which includes the electrochemical device according to the present application.
  • the use of the electrochemical device of the present application is not particularly limited, and it can be used in any electronic device known in the art.
  • the electrochemical device of the present application can be used in, but is not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets, etc.
  • Stereo headphones video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, boosters Bicycles, bicycles, lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • LiCoO 2 lithium cobalt oxide
  • conductive agent Super P conductive agent
  • binder polyvinylidene fluoride in a weight ratio of 97:1:2, add N-methylpyrrolidone (NMP), and mix in a vacuum mixer.
  • NMP N-methylpyrrolidone
  • Boehmite is mixed with polyacrylate and dissolved into deionized water to form a coating slurry.
  • the coating slurry is then evenly coated on both surfaces of the polyethylene porous substrate using a micro-gravure coating method, and is dried to obtain the required isolation film.
  • the electrolyte prepared above is injected into the dried battery core through the injection port, and the lithium-ion battery is obtained through processes such as vacuum packaging, standing, formation, shaping, and capacity testing.
  • n1, n2,...nx represent the mass (g) of different nitrile compounds
  • p1, p2,...px represent the relative content (%) of different nitrile compounds
  • M1, M2,...Mx represent the relative molar masses (g/mol) of different nitrile compounds
  • ⁇ 1, ⁇ 2,... ⁇ x represent the number of cyano groups in different nitrile compounds.
  • the lithium-ion batteries were divided into three groups and subjected to charge and discharge cycle tests at currents of 0.7C, 1.5C and 3C, with each group including 10 lithium-ion batteries.
  • Cycle capacity retention rate (C250/C1) ⁇ 100%.
  • Cycle capacity retention rate (C′/C) ⁇ 100%.
  • Thickness growth rate ( ⁇ ′/ ⁇ -1) ⁇ 100%.
  • Table 1 shows the effects of the content and ratio of carboxylate compounds and FEC in the electrolyte on the fast charging performance and high-temperature ITC performance of lithium-ion batteries.
  • the electrochemical test results in Table 1 show that adding carboxylic acid ester compound and FEC to the electrolyte, and adjusting their content and proportion to satisfy 5% ⁇ w 1 ⁇ 60%, 2% ⁇ w 2 ⁇ 12% and 2 ⁇ w 1 /w 2 ⁇ 20 can improve the fast charging performance of the electrochemical device without deteriorating or slightly deteriorating the high-temperature ITC performance of the electrochemical device.
  • Comparative Examples 1-1 to 1-3 show that adding FEC alone to the electrolyte and keeping the content within an appropriate range can improve the fast charging performance of the electrochemical device to a certain extent.
  • the FEC content is too high (for example, more than 12%)
  • gas production will be aggravated, causing the thickness of the battery to increase significantly during high-temperature interval cycles.
  • too high a content of FEC will not only not improve the fast charging performance of the electrochemical device at large currents (for example, 1.5C and 3C), but will actually worsen it. This is because an appropriate amount of FEC can effectively alleviate the damage to the negative SEI film during battery charging and discharging and repair it in time, thereby improving overcharge performance.
  • Comparative Examples 1-4 to 1-6 further added a chain carboxylic acid ester compound to the electrolyte, which improved the fast charging performance of the electrochemical device, especially for large current ( For example, the fast charging performance at 1.5C and 3C) has been significantly improved.
  • ethyl acetate ethyl propionate and propyl propionate improve fast charging performance while basically not deteriorating high-temperature ITC performance, and even improve high-temperature ITC performance.
  • Comparing Examples 1-1 to 1-4 with Comparative Examples 1-5 and 1-7 to 1-9 it can be seen that when the content and proportion of the carboxylate compound and FEC satisfy 5% ⁇ w 1 ⁇ 60%, 2 When % ⁇ w 2 ⁇ 12% and 2 ⁇ w 1 /w 2 ⁇ 20, the fast charging performance of the electrochemical device can be improved without deteriorating or slightly deteriorating the high-temperature ITC performance of the electrochemical device. Comparing Examples 1-5 and 1-6 with Comparative Example 1-5, it can be seen that further adjusting w 1 /w 2 in the range of 4 ⁇ w 1 /w 2 ⁇ 10 can not only improve the fast charging of the electrochemical device performance, and can also simultaneously improve its high-temperature ITC performance. Comparing Examples 1-7 and 1-8 with Comparative Examples 1-4 and 1-10, or comparing Examples 1-9 to 1-11 with Comparative Examples 1-6, the same conclusion can be obtained. .
  • Examples 1-12 to 1-15 use a combination of multiple carboxylic acid ester compounds when 5% ⁇ w 1 ⁇ 60%, 2% ⁇ w 2 ⁇ 12%, and 2 ⁇ w 1 /w 2 ⁇ 20 , is expected to achieve simultaneous improvements in fast charging performance and high-temperature ITC performance. For example, adding propyl propionate and ethyl propionate simultaneously to the electrolyte can more efficiently improve fast charging performance while maintaining superior high-temperature ITC performance.
  • Table 2 shows the effect of cyano group enrichment and the content of carboxylic acid ester and FEC in the electrolyte on the fast charging performance and high temperature ITC performance of lithium-ion batteries, where the examples in Table 2 are in Examples 1-14 Improvements made on the basis of , the difference is specifically the addition of nitrile additives to the electrolyte.
  • Examples 2-1 to 2-8 use a single nitrile additive in the electrolyte, which will slightly deteriorate the fast charging performance of the electrochemical device, but significantly improve the high-temperature ITC performance.
  • a single nitrile compound when added in excess, it will increase the viscosity of the electrolyte to a certain extent, causing the lithium ion deintercalation reaction to be delayed and lithium to be precipitated, thus negatively affecting the high-temperature ITC performance to a certain extent.
  • Examples 2-9 to 2-29 introduce a variety of nitrile additives into the electrolyte solution.
  • the electrochemistry can be basically not deteriorated. Under the premise of fast charging performance of the device, its high-temperature ITC performance is effectively improved.
  • Examples 2-26 to 2-29 illustrate that on the premise of meeting the above range of cyano group enrichment, the total amount of nitriles should not be too high or too low.
  • the cyano group enrichment x/y satisfies 2.16 ⁇ x/y ⁇ 2.71
  • the upper limit of the dosage of a single nitrile can be exceeded and the high temperature improvement can be maximized. ITC performance.
  • Table 3 shows the effects of cell size and the content of carboxylate compounds in the electrolyte on the high-temperature ITC performance of lithium-ion batteries.
  • the examples in Table 3 are improvements based on Examples 2-23. The difference is specifically due to the cell size and/or the content of the carboxylate compound in the electrolyte.
  • test results in Table 3 show that making the battery size design and the content of the carboxylate compound in the electrolyte follow a certain relationship can increase the battery charge rate window, improve lithium evolution, and thus improve the fast charging performance of the electrochemical device.
  • Examples 3-1 to 3-12 show that when the electrolyte solution remains unchanged, when the aspect ratio L/W is in the range of 1 ⁇ L/W ⁇ 4 or the width-to-thickness ratio W/T is in the range of W/T ⁇ 5 Within, the fast charging performance of electrochemical devices can be improved, especially the fast charging performance at large rate currents above 1.5C can be significantly improved. This is mainly because when the battery core is within the above range, the current density in the upper and lower edge areas and the wound outer ring pole piece area and the increase in temperature during charging are not much different from the main area, so it will decrease in the edge area and periphery. Lithium is deposited in the pole piece area, thereby improving fast charging performance.
  • Examples 3-13 to 3-17 show that when the cell size remains unchanged, adjusting the content of the carboxylic acid ester compound in the electrolyte to satisfy w 1 ⁇ 100/(L/W) ⁇ 10 can improve the electrochemical device.
  • the fast charging performance especially the fast charging performance at high rate current above 1.5C, can be significantly improved.
  • adding carboxylate compounds can improve the fast charging performance of electrochemical devices, it has a negative impact on high-temperature ITC performance.
  • based on the size limitations of electrochemical devices used in notebook computers combined with cell size design Adjusting carboxylate esters is considered an effective measure to simultaneously improve kinetic capabilities and battery safety.
  • references throughout the specification to “embodiment”, “partial embodiment”, “one embodiment”, “another example”, “example”, “specific example” or “partial example” mean that At least one embodiment or example in this application includes a specific feature, structure, material or characteristic described in the embodiment or example. Accordingly, phrases such as “in some embodiments,” “in an embodiment,” “in one embodiment,” “in another example,” “in one example,” etc. may appear in various places throughout this specification. "in”, “in a particular example” or “for example” do not necessarily refer to the same embodiment or example in this application. Furthermore, the specific features, structures, materials, or characteristics herein may be combined in any suitable manner in one or more embodiments or examples.

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Abstract

本申请涉及一种电化学装置及包含其的电子装置。电化学装置包括电解液，所述电解液包括羧酸酯化合物和氟代碳酸乙烯酯(FEC)，其中基于所述电解液的总重量，所述羧酸酯化合物和所述FEC的含量分别为w1和w2，5％≤w1≤60％，2％≤w2≤12％，且2≤w1/w2≤20。上述电化学装置表现出优异的快充性能和高温间隔循环性能。

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
由于具有高能量密度和相对简单的反应机理、工作电压高、寿命长、绿色环保等优点，可再充电的电化学装置被认为是最具吸引力的储能系统之一。如今，电化学装置如锂离子电池已经广泛地应用于笔记本电脑、智能手机、可穿戴设备等电子产品中。
随着市场对于电子产品快速充电的追求，对电化学装置的充电速度要求越来越高，这也就要求电化学装置在大倍率电流密度下仍然具备优异的电化学表现，尤其是优异的循环性能。另外，在对电化学装置进行快充时，往往伴随着发热的发生，而温度升高会进一步恶化电化学装置的循环稳定性。例如，笔记本电脑在使用的过程中常常会先充电至满充状态，再在满充状态下保持数个小时，最后被切断充电器处于放电状态，而上述过程会导致笔记本电脑中的电池发热从而处于高温状态。当笔记本电脑经历上述高温存储和充放电循环的间歇工况下，其中的电池容量会衰减严重，这又对电化学装置的高温间隔循环(Interval Cycle，ITC)性能提出了更高的要求。
有鉴于此，亟需获得一种具备优异的快充性能和高温间隔循环性能的电化学装置以满足人们的上述需求。
发明内容
至少为了解决上述问题，本申请通过改进电解液的配方组成和/或对电化学装置的尺寸进行设计来改善电化学装置的快充性能和高温间隔循环性能。
根据本申请的一个方面，本申请提供一种电解液，所述电解液包括式(I)所示羧酸酯化合物和氟代碳酸乙烯酯(FEC)，
Figure PCTCN2022094915-appb-000001
其中，R 11包括氢、羟基、C1-C20的烷基、C1-C20的烷氧基、C2-C20的链状烯基、C6-C30的芳基、或C6-C30的芳氧基中的至少一者，R 12包括C1-C20的烷基、C2-C20的链状烯基、或C6-C30的芳基中的至少一者；
其中，基于所述电解液的总重量，所述式(I)所示羧酸酯化合物和所述FEC的含量分别为w 1和w 2，5％≤w 1≤60％，2％≤w 2≤12％，且2≤w 1/w 2≤20。
根据本申请的实施例，其中，4≤w 1/w 2≤10。
根据本申请的实施例，其中，所述式(I)所示羧酸酯化合物包括以下各者中的至少一者：乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸正丙酯、丙酸异丙酯、丙酸正丁酯、丙酸异丁酯、丙酸正戊酯、丙酸异戊酯、正丁酸乙酯、正丁酸正丙酯、异丁酸丙酯、正丁酸正戊酯、异丁酸正戊酯、正丁酸正丁酯、异丁酸异丁酯或正戊酸正戊酯。
根据本申请的实施例，其中，所述式(I)所示羧酸酯化合物包括丙酸丙酯和乙酸乙酯。
根据本申请的实施例，其中，所述电解液还包括腈类化合物，基于所述电解液的总重量，所述腈类化合物的含量为w 3，0.1％≤w 3≤12％。
根据本申请的实施例，其中，所述腈类化合物包括式(II)至式(V)所示化合物中的至少一种：
N≡C——R 21——C≡N，
式(II)
Figure PCTCN2022094915-appb-000002
Figure PCTCN2022094915-appb-000003
其中，R 21包括取代或未取代的C1-C12的亚烷基或取代或未取代的C1-C12的亚烷氧基中的至少一者；
R 31、R 32各自独立地包括氢、取代或未取代的C1-C12的亚烷基；
R 41、R 42、R 43各自独立地包括氢、取代或未取代的C1-C12的亚烷基或取代或未取代的C1-C12的亚烷氧基；
R 51包括取代或未取代的C1-C12的亚烷基、取代或未取代的C2-C12的亚烯基、取代或未取代的C6-C26的亚芳基或取代或未取代的C2-C12亚杂环基团，其中杂原子为N、S或O中的至少一者；
其中经取代时，取代基为卤素。
根据本申请的实施例，其中，所述腈类化合物中的氰基(-CN)的摩尔总量为x，所述腈类化合物的摩尔总量为y，氰基富集度x/y满足2.16≤x/y≤2.71。
根据本申请的实施例，其中，所述氰基富集度x/y、所述式(I)所示羧酸酯化合物的含量w 1和所述FEC的含量w 2满足2w 1 2-0.01w 1+2.3＞x/y＞27w 2 2-1.2w 2+2.1。
根据本申请的实施例，其中，所述电解液包括锂盐，所述锂盐包括以下各者中的至少一者：LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB或LiDFOB。
根据本申请的另一个方面，本申请还提供了一种电化学装置，其包括本申请上述实施例所述的电解液。
根据本申请的实施例，其中，所述电化学装置还包括正极、负极和位于所述 正极和所述负极之间的隔膜，其中，所述正极、所述负极和所述隔膜经卷绕以形成电芯，所述电芯的长度L和宽度W满足20mm≤L≤300mm，20mm≤W≤100mm，且1≤L/W≤4。
根据本申请的实施例，其中，所述电化学装置满足如下特征中的至少一者：a).1≤L/W≤3；b)2≤L/W≤3；c)2≤L/W≤4。
根据本申请的实施例，其中，所述电化学装置还包括正极、负极和位于所述正极和所述负极之间的隔膜，其中，所述正极、所述负极和所述隔膜经卷绕以形成电芯，所述电芯的厚度T和宽度W满足2mm≤T≤12mm，W/T≥5。
根据本申请的实施例，其中，所述电化学装置满足如下特征中的至少一者：d).5≤W/T≤25；e)5≤W/T≤20；f)5≤W/T≤15；g)10≤W/T≤25。
根据本申请的实施例，其中，所述电化学装置还包括正极、负极和位于所述正极和所述负极之间的隔膜，其中，所述正极、所述负极和所述隔膜经卷绕以形成电芯，所述电芯的长度L和宽度W以及所述式(I)所示羧酸酯化合物的含量w 1满足w 1×100/(L/W)≥10。
根据本申请的实施例，其中，所述电化学装置满足如下特征中的至少一者：h).10≤w 1×100/(L/W)≤40；i).20≤w 1×100/(L/W)≤30；j)20≤w 1×100/(L/W)≤40；k).15≤w 1×100/(L/W)≤30。
根据本申请的另一个方面，本申请还提供了一种电子装置，其包括本申请上述实施例所述的电化学装置。
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示出了氰基富集度x/y和羧酸酯化合物的含量w 1之间的关系图。
图2示出了氰基富集度x/y和氟代碳酸乙烯酯(FEC)的含量w 2之间的关系图。
图3示出了封装完成后的电芯的长度L、宽度W和厚度T。
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。
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“中的一者或多者”、“中的一个或多个”、“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中的至少一种”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中的至少一种”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可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
术语“烷基”涵盖直链和支链烷基。例如，烷基可为C1-C50烷基、C1-C40烷基、C1-C30烷基、C1-C20烷基、C1-C12烷基、C1-C10烷基、C1-C6烷基、C2-C6烷基、C2-C5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C2-C50烯基、C2-C40烯基、C2-C30烯基、C2-C20烯基、C2-C12烯基、C2-C10烯基、C2-C6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C6-C50芳基、C6-C40芳基、C6-C30芳基、C6-C20芳基或C6-C10芳基。另外，芳基可以是任选地被取代的。
术语“烷氧基”为具有-O-R1的有机物基团，其中R1为上述所提到的直链或支链烷基。
术语“芳氧基”为具有-O-R2的有机物基团，其中R2为上述所提到的芳基。
术语“亚烷基”涵盖直链和支链亚烷基。例如，亚烷基可为C1-C50亚烷基、C1-C40亚烷基、C1-C30亚烷基、C1-C20亚烷基、C1-C10亚烷基、C1-C6亚烷基、C2-C6亚烷基、C2-C5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C2-C50亚烯基、C2-C40亚烯基、C2-C30亚烯基、C2-C20亚烯基、C2-C10亚烯基、C1-C6亚烯基、C2-C6亚烯基。另外，亚烯基可以是任选地被取代的。
术语“亚杂环基团”包括与其中环上碳原子中的一个或多个为非碳元素，例如氮、硫或氧的碳环基团类似的闭环结构，包括但不限于氮丙啶基团、环氧乙烷基团(环氧化物、环氧乙烷)、环硫乙烷(基团环硫化物)、双环氧乙烷基团、氮杂环丁烷基团、氧杂环丁烷基团、硫杂环丁烷基团、二氧杂环丁烷基团、二硫杂环丁烷基团、二硫环丁烯基团、氮杂环戊烷基团、吡咯啶基团、吡咯啉基团、氧杂环戊烷基团、二氢呋喃基团以及呋喃基团等。
当上述基团经取代时，取代基可独立地选自烷基、烯基、芳基、烷氧基、芳氧基、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。
I、电解液
电解液作为电化学装置的重要组成部分，用于在正负极之间传输锂离子以实现锂离子在正负极材料中不断地嵌入和脱出，从而发挥充放电的功能。因此，电解液对电化学装置的电化学性能有着至关重要的影响。
为了提高电化学装置的快充性能，本申请将粘度较低的羧酸酯化合物添加至电解液中以提高锂离子在电解液中的传输速率。然而，本申请进一步发现羧酸酯化合物的电化学窗口较窄，高温稳定性差。例如，当电子装置(例如，笔记本电脑)在高温存储和充放电循环的间歇工况下，羧酸酯化合物会在负极处发生反应，消耗活性锂，破坏负极表面的固体电解质界面(SEI)膜，造成电池容量的快速衰减。
为了有效缓解羧酸酯化合物对负极SEI膜的破坏并对负极SEI膜进行及时修复，本申请进一步在电解液中添加了氟代碳酸乙烯酯(FEC)。然而，本申请进 一步发现当电化学装置在高温存储和充放电循环的间歇工况下，正极结构容易遭到破坏并发生释氧反应，而此时FEC极易被氧化分解产生CO 2，造成电化学装置鼓包胀气。
然而，本申请出乎意料地发现通过调整羧酸酯化合物和FEC在电解液中的含量和比值，能够有效改善电化学装置的快充性能，同时还不会恶化或较小恶化电化学装置的高温间隔循环性能。在一些实施例中，基于电解液的总重量，羧酸酯化合物和FEC的含量分别为w 1和w 2，其中5％≤w 1≤60％，2％≤w 2≤12％，且2≤w 1/w 2≤20。
在一些实施例中，w 1可以，但不限制为5％、10％、15％、20％、25％、30％、35％、40％、45％、50％、55％或60％，或者处于由上述任意两个数值所组成的范围内。例如，10％≤w 1≤50％或者15％≤w 1≤50％。
在一些实施例中，w 2可以，但不限制为2％、4％、6％、8％、10％或12％，或者处于由上述任意两个数值所组成的范围内。例如，4％≤w 2≤12％或者4％≤w 1≤10％。
在一些实施例中，w 1/w 2可以，但不限制为2、4、6、8、10、12、14、16、18或20，或者处于由上述任意两个数值所组成的范围内。例如，4≤w 1/w 2≤16或者4≤w 1/w 2≤10。
在一些实施例中，羧酸酯化合物为如下式(I)所示的羧酸酯化合物，
Figure PCTCN2022094915-appb-000004
其中，R 11包括氢、羟基、C1-C20的烷基、C1-C20的烷氧基、C2-C20的链状烯基、C6-C30的芳基、或C6-C30的芳氧基中的至少一者，R 12包括C1-C20的烷基、C2-C20的链状烯基、或C6-C30的芳基中的至少一者。
在一些实施例中，式(I)所示羧酸酯化合物包括以下各者中的至少一者：乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸正丙酯、丙酸异丙酯、丙酸正丁酯、丙酸异丁酯、丙酸正戊酯、丙酸异戊酯、正丁酸乙酯、正丁酸正丙酯、异丁酸丙酯、正丁酸正戊酯、异丁酸正戊酯、正丁酸正丁酯、异丁酸异丁酯、或正戊酸正戊酯。
在一些实施例中，式(I)所示羧酸酯化合物至少包括丙酸丙酯。相较于其他羧酸酯化合物，丙酸丙酯更有益于稳定正极结构，因此在改善电化学装置的快充性能的同时，还能同时改善其高温ITC性能并抑制产气，从而提高电化学装置的综合表现。
在一些实施例中，式(I)所示羧酸酯化合物包括丙酸乙酯和乙酸乙酯。在一些实施例中，式(I)所示羧酸酯化合物包括丙酸丙酯和乙酸乙酯。在一些实施例中，式(I)所示羧酸酯化合物包括丙酸丙酯和丙酸乙酯。在一些实施例中，式(I)所示羧酸酯化合物包括乙酸乙酯、丙酸乙酯和丙酸丙酯。
在一些实施例中，所述电解液还包括腈类化合物。其中，腈类化合物包含氰基(-CN)官能团。在一些实施例，基于电解液的总重量，腈类化合物的含量为w 3，0.1％≤w 3≤12％。在一些实施例中，w 3可以，但不限制为0.1％、1％、2％、4％、6％、8％、10％或12％，或者处于由上述任意两个数值所组成的范围内。当腈类化合物的含量处于上述范围内时，在兼顾电化学装置的快充性能的前提下，还能够改善电化学装置的高温ITC性能并抑制产气。这是由于腈类化合物能够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，并减少释氧反应。
在一些实施例中，腈类化合物包括式(II)至式(V)所示化合物中的至少一种：
N≡C——R 21——C≡N，
式(II)
Figure PCTCN2022094915-appb-000005
Figure PCTCN2022094915-appb-000006
其中，R 21包括取代或未取代的C1-C12的亚烷基或取代或未取代的C1-C12的亚烷氧基中的至少一者；
R 31、R 32各自独立地包括氢、取代或未取代的C1-C12的亚烷基；
R 41、R 42、R 43各自独立地包括氢、取代或未取代的C1-C12的亚烷基或取代或未取代的C1-C12的亚烷氧基；
R 51包括取代或未取代的C1-C12的亚烷基、取代或未取代的C2-C12的亚烯基、取代或未取代的C6-C26的亚芳基或取代或未取代的C2-C12亚杂环基团，其中杂原子为N、S或O中的至少一者；
其中经取代时，取代基为卤素。
在一些实施例中，腈类化合物包括己二腈、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。
本申请还对氰基富集度对电化学性能的影响进行了评估，其中氰基富集度为腈类化合物中的氰基(-CN)的摩尔总量x与腈类化合物的摩尔总量y之间的比值。本申请发现，相较于在电解液中添加单一的腈类化合物，例如二腈化合物(即，x/y＝2)或者三腈化合物(即，x/y＝3)，当氰基富集度x/y满足2.16≤x/y≤2.71时，能够显著改善电化学装置的高温ITC性能并抑制产气，同时还会大大降低腈类化合物对电化学装置的快充性能的恶化程度，有望实现快充性能和高温ITC性能的同步提升。这可能是由于相较于氰基数较多的大分子腈类(例如，三腈化合物)所形成的厚的SEI膜和氰基数较小的小分子腈类(例如，二腈化合物)形成的不太稳定的SEI膜，在电解液中添加具有不同氰基数的多种腈类能够在正极表面同时形成大小分子复合的含腈SEI膜，实现更优的效果。
另外，本申请还对羧酸酯化合物的含量w 1、FEC的含量w 2与氰基富集度x/y之间的关系进行了研究。具体的，图1中圆点所示的曲线为x/y＝2w 1 2-0.01w 1+2.3， 而图2中正方形点所示的曲线为x/y＝27w 2 2-1.2w 2+2.1。本申请研究发现，当氰基富集度x/y＞2w 1 2-0.01w 1+2.3时，氰基的浓度较大，这在一定程度上会增加电解液的粘度，阻碍锂离子的传输以及在正负极活性物质中的嵌入和脱出，从而增大锂离子在正负极处析出形成锂枝晶的概率。当氰基富集度x/y＜27w 2 2-1.2w 2+2.1时，氰基的浓度较小，在正极活性表面形成的SEI膜的结构稳定性稍差，从而增大鼓包胀气的概率。
因此，当羧酸酯化合物的含量w 1、FEC的含量w 2与氰基富集度x/y之间的关系满足2w 1 2-0.01w 1+2.3＞x/y＞27w 2 2-1.2w 2+2.1时，不仅能够使电解液的粘度保持在更为适宜的范围内，改善锂离子在电解液中的传输，大幅降低析锂的风险，从而改善电化学装置的快充性能，还能够进一步加强腈类化合物对正极活性物质中的过渡金属的络合保护，降低正极在高温间歇循环的工况下的释氧，提高正极结构的稳定性，从而改善电化学装置的高温ITC性能并抑制产气。也即，当电化学装置满足2w 1 2-0.01w 1+2.3＞x/y＞27w 2 2-1.2w 2+2.1时，能够同步改善电化学装置的快充性能、高温ITC性能并抑制产气。
在一些实施例中，本申请所述的电解液还包括锂盐。锂盐的实例可包括，但不限于，LiPF 6、LiBF 4、LiClO 4、LiAlF 4、LiSbF 6、LiWF 7等无机锂盐；LiWOF 5等钨酸锂类；HCO 2Li、CH 3CO 2Li、CH 2FCO 2Li、CHF 2CO 2Li、CF 3CO 2Li、CF 3CH 2CO 2Li、CF 3CF 2CO 2Li、CF 3CF 2CF 2CO 2Li、CF 3CF 2CF 2CF 2CO 2Li等羧酸锂盐类；FSO 3Li、CH 3SO 3Li、CH 2FSO 3Li、CHF 2SO 3Li、CF 3SO 3Li、CF 3CF 2SO 3Li、CF 3CF 2CF 2SO 3Li、CF 3CF 2CF 2CF 2SO 3Li等磺酸锂盐类；LiN(FCO) 2、LiN(FCO)(FSO 2)、LiN(FSO 2) 2、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1，2-全氟乙烷双磺酰亚胺锂、环状1，3-全氟丙烷双磺酰亚胺锂、LiN(CF 3SO 2)(C 4F 9SO 2)等酰亚胺锂盐类；LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3等甲基化锂盐类；双(丙二酸根合)硼酸锂盐、二氟(丙二酸根合)硼酸锂盐等(丙二酸根合)硼酸锂盐类；三(丙二酸根合)磷酸锂、二氟双(丙二酸根合)磷酸锂、四氟(丙二酸根合)磷酸锂等(丙二酸根合)磷酸锂盐类；以及LiPF 4(CF 3) 2、LiPF 4(C 2F 5) 2、LiPF 4(CF 3SO 2) 2、LiPF 4(C 2F 5SO 2) 2、LiBF 3CF 3、LiBF 3C 2F 5、LiBF 3C 3F 7、LiBF 2(CF 3) 2、LiBF 2(C 2F 5) 2、LiBF 2(CF 3SO 2) 2、LiBF 2(C 2F 5SO 2) 2等含氟有机锂盐类；二氟草酸硼酸锂、双(草酸)硼酸锂等草酸硼酸锂盐类；四氟草酸根合磷酸锂、二氟双(草酸根合)磷酸锂、三(草酸根合)磷酸锂等草酸根合磷酸锂盐类等。
在一些实施例中，锂盐包括以下各者中的至少一者：LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB或LiDFOB。
在一些实施例中，基于电解液的总重量，锂盐的含量为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，所述电解液进一步包含现有技术中已知的任何可作为电解液的溶剂的非水溶剂。
在一些实施例中，所述非水溶剂包括，但不限于，以下中的一种或多种：环状碳酸酯、链状碳酸酯、环状醚、链状醚、含磷有机溶剂、含硫有机溶剂和芳香族含氟溶剂。
在一些实施例中，所述环状碳酸酯的实例可包括，但不限于，以下中的一种或多种：碳酸亚乙酯(EC)、碳酸亚丙酯(PC)和碳酸亚丁酯。在一些实施例中，所述环状碳酸酯具有3-6个碳原子。
在一些实施例中，所述链状碳酸酯的实例可包括，但不限于，以下中的一种或多种：碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯(DEC)、碳酸甲基正丙基酯、碳酸乙基正丙基酯、碳酸二正丙酯等链状碳酸酯等。被氟取代的链状碳酸酯的实例可包括，但不限于，以下中的一种或多种：双(氟甲基)碳酸酯、双(二氟甲基)碳酸酯、双(三氟甲基)碳酸酯、双(2-氟乙基)碳酸酯、双(2，2-二氟乙基)碳酸酯、双(2，2，2-三氟乙基)碳酸酯、2-氟乙基甲基碳酸酯、2，2-二氟乙基甲基碳酸酯和2，2，2-三氟乙基甲基碳酸酯等。
在一些实施例中，所述环状醚的实例可包括，但不限于，以下中的一种或多种：四氢呋喃、2-甲基四氢呋喃、1，3-二氧戊环、2-甲基1，3-二氧戊环、4-甲基1，3-二氧戊环、1，3-二氧六环、1，4-二氧六环和二甲氧基丙烷。
在一些实施例中，所述链状醚的实例可包括，但不限于，以下中的一种或多种：二甲氧基甲烷、1，1-二甲氧基乙烷、1，2-二甲氧基乙烷、二乙氧基甲烷、1，1-二乙氧基乙烷、1，2-二乙氧基乙烷、乙氧基甲氧基甲烷、1，1-乙氧基甲氧基乙烷和1，2-乙氧基甲氧基乙烷等。
在一些实施例中，所述含磷有机溶剂的实例可包括，但不限于，以下中的一 种或多种：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、、亚磷酸三乙酯、亚磷酸三苯酯、磷酸三(2，2，2-三氟乙基)酯和磷酸三(2，2，3，3，3-五氟丙基)酯等。
在一些实施例中，所述含硫有机溶剂的实例可包括，但不限于，以下中的一种或多种：环丁砜、2-甲基环丁砜、3-甲基环丁砜、二甲基砜、二乙基砜、乙基甲基砜、甲基丙基砜、二甲基亚砜、甲磺酸甲酯、甲磺酸乙酯、乙磺酸甲酯或乙磺酸乙酯。在一些实施例中，含硫有机溶剂的部分氢原子可被氟取代。
在一些实施例中，所述芳香族含氟溶剂包括，但不限于，以下中的一种或多种：氟苯、二氟苯、三氟苯、四氟苯、五氟苯、六氟苯和三氟甲基苯。
II、正极
正极包括正极集流体和设置在所述正极集流体的至少一个表面上的正极活性物质层，其中所述正极活性物质层包含正极活性物质。正极活性物质层可以是一层或多层，多层正极活性物质中的每层可以包含相同或不同的正极活性物质。正极活性物质为任何能够可逆地嵌入和脱出锂离子等金属离子的物质。
正极活性物质的种类没有特别限制，只要是能够以电化学方式吸藏和释放金属离子(例如，锂离子)即可。在一些实施例中，正极活性物质为含有锂和至少一种过渡金属的物质。正极活性物质的实例可包括，但不限于，锂过渡金属复合氧化物和含锂过渡金属磷酸化合物。
在一些实施例中，锂过渡金属复合氧化物中的过渡金属包括V、Ti、Cr、Mn、Fe、Co、Ni、Cu等。在一些实施例中，锂过渡金属复合氧化物包括LiCoO 2等锂钴复合氧化物、LiNiO 2等锂镍复合氧化物、LiMnO 2、LiMn 2O 4、Li 2MnO 4等锂锰复合氧化物、LiNi 1/3Mn 1/3Co 1/3O 2、LiNi 0.5Mn 0.3Co 0.2O 2等锂镍锰钴复合氧化物，其中作为这些锂过渡金属复合氧化物的主体的过渡金属原子的一部分被Na、K、B、F、Al、Ti、V、Cr、Mn、Fe、Co、Li、Ni、Cu、Zn、Mg、Ga、Zr、Si、Nb、Mo、Sn、W等其它元素所取代。锂过渡金属复合氧化物的实例可包括，但不限于，LiNi 0.5Mn 0.5O 2、LiNi 0.85Co 0.10Al 0.05O 2、LiNi 0.33Co 0.33Mn 0.33O 2、LiNi 0.45Co 0.10Al 0.45O 2、LiMn 1.8Al 0.2O 4和LiMn 1.5Ni 0.5O 4等。锂过渡金属复合氧化物的组合的实例包括，但不限于，LiCoO 2与LiMn 2O 4的组合，其中LiMn 2O 4中的一部分Mn可被过渡金属所取代(例如，LiNi 0.33Co 0.33Mn 0.33O 2)，LiCoO 2中的一部分Co可被过渡金属所取代。
在一些实施例中，含锂过渡金属磷酸化合物中的过渡金属包括V、Ti、Cr、Mn、Fe、Co、Ni、Cu等。在一些实施例中，含锂过渡金属磷酸化合物包括LiFePO 4、Li 3Fe 2(PO 4) 3、LiFeP 2O 7等磷酸铁类、LiCoPO 4等磷酸钴类，其中作为这些锂过渡金属磷酸化合物的主体的过渡金属原子的一部分被Al、Ti、V、Cr、Mn、Fe、Co、Li、Ni、Cu、Zn、Mg、Ga、Zr、Nb、Si等其它元素所取代。
在上述正极活性物质的表面可附着有与其组成不同的物质。表面附着物质的实例可包括，但不限于：氧化铝、二氧化硅、二氧化钛、氧化锆、氧化镁、氧化钙、氧化硼、氧化锑、氧化铋等氧化物；硫酸锂、硫酸钠、硫酸钾、硫酸镁、硫酸钙、硫酸铝等硫酸盐；碳酸锂、碳酸钙、碳酸镁等碳酸盐；碳等。通过在正极活性物质表面附着物质，可以抑制正极活性物质表面的电解液的氧化反应，可以提高电化学装置的寿命。当表面附着物质的量过少时，其效果无法充分表现；当表面附着物质的量过多时，会阻碍锂离子的出入，因而电阻有时会增加。本申请中，将在正极活性物质的表面附着有与其组成不同的物质的正极活性物质也称为“正极活性物质”。
在一些实施例中，“正极活性物质”优选使用钴酸锂或镍钴锰酸锂。
在一些实施例中，正极活性物质颗粒的形状包括，但不限于，块状、多面体状、球状、椭圆球状、板状、针状和柱状等。在一些实施例中，正极活性物质颗粒包括一次颗粒、二次颗粒或其组合。在一些实施例中，一次颗粒可以凝集而形成二次颗粒。
正极还包括正极导电材料以增加正极的导电性。正极导电材料的种类没有限制，可以使用任何已知的导电材料。正极导电材料的实例可包括，但不限于，天然石墨、人造石墨等石墨；乙炔黑等炭黑；针状焦等无定形碳等碳材料；碳纳米管；石墨烯等。上述正极导电材料可单独使用或任意组合使用。
用于形成正极浆料的溶剂的种类没有限制，只要是能够溶解或分散正极活性物质、导电材料、正极粘合剂和根据需要使用的增稠剂的溶剂即可。用于形成正极浆料的溶剂的实例可包括水系溶剂和有机系溶剂中的任一种。水系介质的实例可包括，但不限于，水和醇与水的混合介质等。有机系介质的实例可包括，但不限于，己烷等脂肪族烃类；苯、甲苯、二甲苯、甲基萘等芳香族烃类；喹啉、吡啶等杂环化合物；丙酮、甲基乙基酮、环己酮等酮类；乙酸甲酯、丙烯酸甲酯等酯类；二亚乙基三胺、N，N-二甲氨基丙胺等胺类；二乙醚、环氧丙烷、四氢呋喃 (THF)等醚类；N-甲基吡咯烷酮(NMP)、二甲基甲酰胺、二甲基乙酰胺等酰胺类；六甲基磷酰胺、二甲基亚砜等非质子性极性溶剂等。
增稠剂通常是为了调节浆料的粘度而使用的。在使用水系介质的情况下，可使用增稠剂和丁苯橡胶(SBR)乳液进行浆料化。增稠剂的种类没有特别限制，其实例可包括，但不限于，羧甲基纤维素、甲基纤维素、羟甲基纤维素、乙基纤维素、聚乙烯醇、氧化淀粉、磷酸化淀粉、酪蛋白和它们的盐等。上述增稠剂可单独使用或任意组合使用。
正极集流体的种类没有特别限制，其可为任何已知适于用作正极集流体的材质。正极集流体的实例可包括，但不限于，铝、不锈钢、镍镀层、钛、钽等金属材料；碳布、碳纸等碳材料。在一些实施例中，正极集流体为金属材料。在一些实施例中，正极集流体为铝。
为了降低正极集流体和正极活性物质层的电子接触电阻，正极集流体的表面可包括导电助剂。导电助剂的实例可包括，但不限于，碳和金、铂、银等贵金属类。
正极可以通过在集流体上形成含有正极活性物质和粘结剂的正极活性物质层来制作。使用正极活性物质的正极的制造可以通过常规方法来进行，即，将正极活性物质和粘结剂、以及根据需要的导电材料和增稠剂等进行干式混合，制成片状，将所得到的片状物压接至正极集流体上；或者将这些材料溶解或分散于液体介质中而制成浆料，将该浆料涂布到正极集流体上并进行干燥，从而在集流体上形成正极活性物质层，由此可以得到正极。
在一些实施例中，基于所述正极活性物质层的总重量，所述正极活性物质的重量分数为M％，其中90≤M≤99.5。在一些实施例中，95≤M≤99。在一些实施例中，M可以为90、92、94、95、96、97、98或99，或者处于由上述任意两个数值所组成的范围内。当所述正极活性物质在所述正极活性物质层中的重量分数满足上述关系时，能够显著提高电化学装置的能量密度。
III、负极
负极包括负极集流体和设置在所述负极集流体的至少一个表面上的负极活性物质层，其中所述负极活性物质层包含负极活性物质。负极活性物质层可以是一层或多层，多层负极活性物质中的每层可以包含相同或不同的负极活性物质。负极活性物质为任何能够可逆地嵌入和脱出锂离子等金属离子的物质。在一些实 施例中，负极活性物质的可充电容量大于正极活性物质的放电容量，以防止在充电期间锂金属无意地析出在负极上。
作为保持负极活性物质的集流体，可以任意使用公知的集流体。负极集流体的实例包括，但不限于，铝、铜、镍、不锈钢、镀镍钢等金属材料。在一些实施例中，负极集流体为铜。
在负极集流体为金属材料的情况下，负极集流体形式可包括，但不限于，金属箔、金属圆柱、金属带卷、金属板、金属薄膜、金属板网、冲压金属、发泡金属等。在一些实施例中，负极集流体为金属薄膜。在一些实施例中，负极集流体为铜箔。在一些实施例中，负极集流体为基于压延法的压延铜箔或基于电解法的电解铜箔。
在一些实施例中，负极集流体的厚度为大于1μm或大于5μm。在一些实施例中，负极集流体的厚度为小于100μm或小于50μm。在一些实施例中，负极集流体的厚度在上述任意两个数值所组成的范围内。
负极活性物质没有特别限制，只要能够可逆地吸藏、放出锂离子即可。负极活性物质的实例可包括，但不限于，天然石墨、人造石墨等碳材料；硅(Si)、锡(Sn)等金属；或Si、Sn等金属元素的氧化物等。负极活性物质可以单独使用或组合使用。
负极活性物质层还可包括负极粘合剂。负极粘合剂可提高负极活性物质颗粒彼此间的结合和负极活性物质与集流体的结合。负极粘合剂的种类没有特别限制，只要是对于电解液或电极制造时使用的溶剂稳定的材料即可。在一些实施例中，负极粘合剂包括树脂粘合剂。树脂粘合剂的实例包括，但不限于，氟树脂、聚丙烯腈(PAN)、聚酰亚胺树脂、丙烯酸系树脂、聚烯烃树脂等。当使用水系溶剂制备负极合剂浆料时，负极粘合剂包括，但不限于，羧甲基纤维素(CMC)或其盐、苯乙烯-丁二烯橡胶(SBR)、聚丙烯酸(PAA)或其盐、聚乙烯醇等。
负极可以通过以下方法制备：在负极集流体上涂布包含负极活性物质、树脂粘合剂等的负极合剂浆料，干燥后，进行压延而在负极集流体的两面形成负极活性物质层，由此可以得到负极。
IV、隔离膜
为了防止短路，在正极与负极之间通常设置有隔离膜。这种情况下，本申请的电解液通常渗入该隔离膜而使用。
对隔离膜的材料及形状没有特别限制，只要不显著损害本申请的效果即可。所述隔离膜可为由对本申请的电解液稳定的材料所形成的树脂、玻璃纤维、无机物等。在一些实施例中，所述隔离膜包括保液性优异的多孔性片或无纺布状形态的物质等。树脂或玻璃纤维隔离膜的材料的实例可包括，但不限于，聚烯烃、芳香族聚酰胺、聚四氟乙烯、聚醚砜等。在一些实施例中，所述聚烯烃为聚乙烯或聚丙烯。在一些实施例中，所述聚烯烃为聚丙烯。上述隔离膜的材料可以单独使用或任意组合使用。
所述隔离膜还可为上述材料层积而成的材料，其实例包括，但不限于，按照聚丙烯、聚乙烯、聚丙烯的顺序层积而成的三层隔离膜等。
无机物的材料的实例可包括，但不限于，氧化铝、二氧化硅等氧化物、氮化铝、氮化硅等氮化物、硫酸盐(例如，硫酸钡、硫酸钙等)。无机物的形式可包括，但不限于，颗粒状或纤维状。
所述隔离膜的形态可为薄膜形态，其实例包括，但不限于，无纺布、织布、微多孔性膜等。在薄膜形态中，所述隔离膜的孔径为0.01μm至1μm，厚度为5μm至50μm。除了上述独立的薄膜状隔离膜以外，还可以使用下述隔离膜：通过使用树脂类的粘合剂在正极和/或负极的表面形成含有上述无机物颗粒的复合多孔层而形成的隔离膜，例如，将氟树脂作为粘合剂使90％粒径小于1μm的氧化铝颗粒在正极的两面形成多孔层而形成的隔离膜。
所述隔离膜的厚度是任意的。在一些实施例中，所述隔离膜的厚度为大于1μm、大于5μm或大于8μm。在一些实施例中，所述隔离膜的厚度为小于50μm、小于40μm或小于30μm。在一些实施例中，所述隔离膜的厚度在上述任意两个数值所组成的范围内。当所述隔离膜的厚度在上述范围内时，则可以确保绝缘性和机械强度，并可以确保电化学装置的倍率特性和能量密度。
在使用多孔性片或无纺布等多孔质材料作为隔离膜时，隔离膜的孔隙率是任意的。在一些实施例中，所述隔离膜的孔隙率为大于10％、大于15％或大于20％。在一些实施例中，所述隔离膜的孔隙率为小于60％、小于50％或小于45％。在一些实施例中，所述隔离膜的孔隙率在上述任意两个数值所组成的范围内。当所述隔离膜的孔隙率在上述范围内时，可以确保绝缘性和机械强度，并可以抑制膜电阻，使电化学装置具有良好的安全特性。
所述隔离膜的平均孔径也是任意的。在一些实施例中，所述隔离膜的平均孔 径为小于0.5μm或小于0.2μm。在一些实施例中，所述隔离膜的平均孔径为大于0.05μm。在一些实施例中，所述隔离膜的平均孔径在上述任意两个数值所组成的范围内。若所述隔离膜的平均孔径超过上述范围，则容易发生短路。当隔离膜的平均孔径在上述范围内时，使电化学装置具有良好的安全特性。
V、电化学装置
本申请的电化学装置包括发生电化学反应的任何装置，它的具体实例包括锂金属二次电池或锂离子二次电池。本申请的电化学装置包括上述实施例中提到的电解液。在一些实施例中，申请的电化学装置还包括正极、负极和位于所述正极和所述负极之间的隔膜。
考虑到笔记本电脑给电化学装置预留的设计空间，电化学装置通常趋向窄长形状。窄长型电池由于电流分布不均和SEI成膜不均的原因，常温或低温充电时更容易在上下边缘位置发生锂析出，导致容量衰减。此外，析出的锂枝晶还可能会刺破位于正负极之间的隔膜，造成电池短路，从而引发安全问题。
在一些实施例中，正极、负极和隔膜经卷绕以形成电芯。在一些实施例中，正极、负极和隔膜经叠片以形成电芯。
本申请发现对电芯的尺寸进行调整能够提高电化学装置的充电倍率窗口，改善析锂，从而改进电化学装置的快充性能。
在一些实施例中，电芯的长度L和宽度W满足20mm≤L≤300mm，20mm≤W≤100mm，且1≤L/W≤4。在一些实施例中，电芯的长度L可以，但不限制为20mm、50mm、75mm、100mm、125mm、150mm、175mm、200mm、225mm、250mm、275mm或300mm，或者处于上述任何两个点值所组成的范围内。在一些实施例中，电芯的宽度W可以，但不限制为20mm、30mm、40mm、50mm、60mm、70mm、80mm、90mm或100mm，或者处于上述任何两个点值所组成的范围内。在一些实施例中，电芯的长宽比L/W可以，但不限制为1、2、3或4，或者处于上述任何两个点值所组成的范围内。
在一些实施例中，电芯的厚度T满足2mm≤T≤12mm。在一些实施例中，电芯的厚度T可以，但不限制为2、4、6、8、10或12，或者处于由上述任意两个数值所组成的范围内。在一些实施例中，电芯的宽度和厚度比W/T满足W/T≥5。在一些实施例中，电芯的宽度和厚度比W/T满足W/T≤25。在一些实施例中，W/T可以，但不限于为5、10、15、20或25，或者处于上述任何两个点值 所组成的范围内。
在一些实施例中，通过设计电池尺寸并且同时优化羧酸酯化合物在电解液中的含量，能够进一步提升电化学装置的充电倍率窗口，改善析锂，从而进一步改善电化学装置的快充性能。在一些实施例中，电芯的长度L和宽度W以及式(I)所示羧酸酯化合物的含量w 1满足w 1×100/(L/W)≥10。在一些实施例中，电芯的长度L和宽度W以及式(I)所示羧酸酯化合物的含量w 1满足w 1×100/(L/W)≤40。在一些实施例中，w 1×100/(L/W)可以，但不限于为10、15、20、25、30、35或40，或者处于上述任何两个点值所组成的范围内。
VI、电子装置
本申请另提供了一种电子装置，其包括根据本申请所述的电化学装置。
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电子装置。在一些实施例中，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。
下面以锂离子电池为例并且结合具体的实施例说明锂离子电池的制备，本领域的技术人员将理解，本申请中描述的制备方法仅是实例，其他任何合适的制备方法均在本申请的范围内。
(I)、锂离子电池的制备
(1)正极的制备
将正极活性材料钴酸锂(LiCoO 2)、导电剂Super P、粘结剂聚偏二氟乙烯按照重量比97∶1∶2进行混合，加入N-甲基吡咯烷酮(NMP)，在真空搅拌机作用下搅拌均匀，获得正极浆料；将正极浆料均匀涂覆于正极集流体铝箔上；将铝箔烘干，然后经过冷压、裁片、分切后，在真空条件下干燥，得到正极片。
(2)负极的制备
将负极活性材料人造石墨、增稠剂羧甲基纤维素钠(CMC)、粘结剂丁苯橡胶(SBR)按照重量比97∶1∶2进行混合，加入去离子水，在真空搅拌机作用下获 得负极浆料；将负极浆料均匀涂覆在负极集流体铜箔上；将铜箔烘干，然后经过冷压、裁片、分切后，在真空条件下干燥，得到负极片。
(3)电解液的制备
在干燥的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸乙烯酯(PC)和碳酸二乙酯(DEC)按照重量比1∶3∶6进行混合，加入锂盐LiPF 6混合均匀，形成基础电解液，其中LiPF 6的浓度为1.2mol/L。根据需要，在基础电解液中加入添加剂得到本申请实施例和对比例中的电解液，其中添加剂的具体种类及其含量可参见下表1-3。
(4)隔离膜的制备
将勃姆石与聚丙烯酸酯混合并将其溶入到去离子水中以形成涂层浆料。随后采用微凹涂布法将所述涂层浆料均匀涂布到聚乙烯多孔基材的两个表面上，经过干燥处理以获得所需隔离膜。
(5)锂离子电池的制备
将正极、隔离膜、负极按顺序叠好，其中隔离膜处于正、负极之间起到隔离的作用，然后经卷绕得到电芯；焊接极耳后将电芯置于外包装箔铝塑膜中，留下注液口。将上述制备好的电解液经由注液口注入到干燥后的电芯中，经过真空封装、静置、化成、整形、容量测试等工序，获得锂离子电池。
(II)、测试方法
1、电解液成分和含量的测试方法
将电池以0.1C恒流放电至2.8V，称取电池重量并计为m。然后将电池拆解，迅速把拆解得到的电芯和外包装箔铝塑膜放入高纯乙腈(纯度≥99.9％)中进行萃取，对经萃取的清液进行气相色谱测试，得到电解液中各个组分及其相对含量p。将萃取后的电芯和外包装箔铝塑在真空烘箱中烘干，称取总重量并计为m′，则电解液的重量n＝m-m′，电池中各组分的重量为n与各组分相对含量p的乘积。
2、氰基富集度的计算方法
通过如下公式计算氰基富集度：
Figure PCTCN2022094915-appb-000007
其中，n1、n2、……nx表示不同腈类化合物的质量(g)，
p1、p2、……px表示不同腈类化合物的相对含量(％)，
M1、M2、……Mx表示不同腈类化合物的相对摩尔质量(g/mol)，
ε1、ε2、……εx表示不同腈类化合物的氰基数量。
3、电芯尺寸的测试方法
拆解去除外包装箔铝塑膜，得到电芯，如图4所示，用千分尺分别测量电芯的长度L、宽度W和厚度T。
4、锂离子电池的快充性能测试
将锂离子电池分为三组，分别在0.7C、1.5C和3C的电流下进行充放电循环测试，其中每组包括10个锂离子电池。
在25℃下，将锂离子电池静置30分钟，分别以0.7C、1.5C和3C充电至电压为4.5V，恒压充电至0.05C，再分别以0.7C、1.5C和3C恒流放电至3.0V，按照上述流程进行充放电循环250圈。
记录各个锂离子电池的首次放电容量，并针对组内的电池取平均值，记为C1；记录各个锂离子电池循环250圈后的放电容量，并针对组内的电池取平均值，记为C250。利用如下公式计算锂离子电池在0.7C、1.5C和3C下的循环容量保持率：
循环容量保持率＝(C250/C1)×100％。
5、锂离子电池的高温间隔循环(ITC)测试
将锂离子电池置于45℃恒温箱中，静置30分钟。随后将锂离子电池以0.5C的电流放电至3.0V，再以1C的电流充电至4.5V，静置24小时，此为一个充放电循环。按照上述流程进行充放电循环50圈。记录首次放电容量和循环50圈后的放电容量分别为C和C′，并利用如下公式计算锂离子电池的循环容量保持率：
循环容量保持率＝(C′/C)×100％。
同时，利用千分尺分别测量锂离子电池的初始厚度η和循环50圈后的厚度η′。利用如下公式计算锂离子电池的厚度增长率：
厚度增长率＝(η′/η-1)×100％。
(III)、测试结果
表1展示了羧酸酯化合物和FEC在电解液中的含量及其比值对锂离子电池的快充性能和高温ITC性能的影响。
表1
Figure PCTCN2022094915-appb-000008
Figure PCTCN2022094915-appb-000009
备注：符号“/”表示不存在相应组分。
表1的电化学测试结果表明，在电解液中加入羧酸酯化合物和FEC，并调整其含量和比例满足5％≤w 1≤60％，2％≤w 2≤12％且2≤w 1/w 2≤20，能够在不恶化或较小恶化电化学装置的高温ITC性能的前提下，改善电化学装置的快充性能。
对比例1-1至1-3表明，在电解液中单独添加FEC并使其含量处于适当的范围内，能够在一定程度上改善电化学装置的快充性能。但是，当FEC的含量过 高(例如，超过12％)时，会加重产气，造成电池在高温间隔循环中的厚度发生明显增长。此外，FEC的含量过高对电化学装置在大电流(例如，1.5C和3C)下的快充性能不仅不会改进，反而有所恶化。这是因为适量的FEC能够有效缓解电池充放电过程中对负极SEI膜的破坏，并及时修复，从而改善过充性能。但是当FEC的含量过高时，容易形成过厚的SEI膜，成膜反应的加剧也进一步造成电芯析锂，导致电池容量的快速衰减。此外，当FEC的含量过高时，在ITC间歇循环工况下，正极结构遭到破坏，发生释氧反应，氧化FEC产生CO 2，造成电池鼓包胀气。
对比例1-4至1-6和对比例1-1相比，在电解液中进一步加入了链状羧酸酯化合物，其对电化学装置的快充性能有所改善，尤其对大电流(例如，1.5C和3C)下的快充性能改善明显。相较于乙酸乙酯，丙酸乙酯和丙酸丙酯在改善快充性能的同时基本上不会恶化高温ITC性能，甚至还对高温ITC性能有所改进。
将实施例1-1至1-4与对比例1-5、1-7至1-9进行对比可知，当羧酸酯化合物和FEC的含量和比例满足5％≤w 1≤60％，2％≤w 2≤12％且2≤w 1/w 2≤20时，能够在不恶化或轻微恶化电化学装置的高温ITC性能的前提下，改善电化学装置的快充性能。将实施例1-5和1-6与对比例1-5进行对比可知，进一步调整w 1/w 2处于4≤w 1/w 2≤10的范围内，不仅能够改善电化学装置的快充性能，还能够同步改善其高温ITC性能。将实施例1-7和1-8与对比例1-4和1-10进行对比，或者将实施例1-9至1-11和对比例1-6进行对比可知，也能得到相同的结论。
实施例1-12至1-15采用多种羧酸酯化合物的组合，当满足5％≤w 1≤60％，2％≤w 2≤12％，且2≤w 1/w 2≤20时，有望实现快充性能和高温ITC性能的同步提升。例如，在电解液中同时加入丙酸丙酯和丙酸乙酯，能够在保持较优的高温ITC性能的前提下，更高效地改进快充性能。
表2展示了氰基富集度与羧酸酯和FEC在电解液中的含量对锂离子电池的快充性能和高温ITC性能的影响，其中表2中的实施例是在实施例1-14的基础上进行的改进，其差异具体为在电解液中添加了腈类添加剂。
表2的性能测试结果表明，在电解液中进一步添加适量的腈类添加剂，在不恶化或者轻微恶化电化学装置的快充性能的前提下，能够改善其高温ITC性能。
实施例2-1至2-8与实施例1-14相比，在电解液中引用了单一的腈类添加剂，其会稍微恶化电化学装置的快充性能，但是对高温ITC性能有明显改进。然而， 当单一的腈类化合物添加过量时，会在一定程度上增加电解液的粘度，造成锂离子脱嵌反应不及时而析锂，从而在一定程度上负面影响高温ITC性能。
实施例2-9至2-29与实施例1-14相比，在电解液中引入了多种腈类添加剂。参见实施例2-9至2-17，在腈类化合物的添加量一定的情况下，当氰基富集度x/y满足2.16≤x/y≤2.71时，能够在基本上不恶化电化学装置的快充性能的前提下，有效改善其高温ITC性能。
从表2中的数据还可以看出，当氰基富集度x/y满足2.16≤x/y≤2.71且控制腈类化合物的含量w 3处于0.1％≤w 3≤12％的范围内时，能够突破单一腈类的加入对高温ITC性能的改善效果，同时也能够有效缓解单一腈类对快充性能的恶化。
同时，实施例2-26至2-29说明在满足氰基富集度的上述范围前提下，腈类总量不宜过高或过低。但与实施例2-19和2-25的比较可以看出，当氰基富集度x/y满足2.16≤x/y≤2.71时，可突破单一腈类的用量上限，最大限度地改善高温ITC性能。
Figure PCTCN2022094915-appb-000010
Figure PCTCN2022094915-appb-000011
Figure PCTCN2022094915-appb-000012
Figure PCTCN2022094915-appb-000013
表3展示了电芯尺寸与羧酸酯化合物在电解液中的含量对锂离子电池的高温ITC性能的影响，其中表3中的实施例是在实施例2-23的基础上进行的改进，其差异具体为电芯尺寸和/或羧酸酯化合物在电解液中的含量不同。
表3
Figure PCTCN2022094915-appb-000014
表3的测试结果表明，使电池尺寸设计结合羧酸酯化合物在电解液中的含量遵照一定的关系式，可提升电池充电倍率窗口，改善析锂，从而改进电化学装置的快充性能。
实施例3-1至3-12表明，当电解液不变时，当长宽比L/W处于1≤L/W≤4的范围内或者宽厚比W/T处于W/T≥5的范围内，能够改善电化学装置的快充性能，尤其是在1.5C以上的大倍率电流的快充性能能够得到显著提升。这主要是由于当电芯处于上述范围内时，上下边缘区域和卷绕的外圈极片区域的电流密度以及充电时温度的升高和主体区域相差不大，因此会降低在边缘区域和外围极 片区域的析锂，从而改善快充性能。
实施例3-13至3-17表明，当电芯尺寸不变时，调整羧酸酯化合物在电解液中的含量以满足w 1×100/(L/W)≥10，能够改善电化学装置的快充性能，尤其是在1.5C以上的大倍率电流的快充性能能够得到显著提升。尽管加入羧酸酯化合物能够改进电化学装置的快充性能，但是其对高温ITC性能产生负面影响，另外，基于在笔记本电脑中应用的电化学装置的尺寸的局限性，结合电芯尺寸设计来调整羧酸酯，被作为同步提升动力学能力和电池安全的有效措施。
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 (17)

  1. 一种电解液，所述电解液包括式(I)所示羧酸酯化合物和氟代碳酸乙烯酯(FEC)，
    Figure PCTCN2022094915-appb-100001
    其中，R 11包括氢、羟基、C1-C20的烷基、C1-C20的烷氧基、C2-C20的链状烯基、C6-C30的芳基、或C6-C30的芳氧基中的至少一者，R 12包括C1-C20的烷基、C2-C20的链状烯基、或C6-C30的芳基中的至少一者；
    其中，基于所述电解液的总重量，所述式(I)所示羧酸酯化合物和所述FEC的含量分别为w 1和w 2，5％≤w 1≤60％，2％≤w 2≤12％，且2≤w 1/w 2≤20。
  2. 根据权利要求1所述的电解液，其中，4≤w 1/w 2≤10。
  3. 根据权利要求1所述的电解液，其中，所述式(I)所示羧酸酯化合物包括以下各者中的至少一者：乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸正丙酯、丙酸异丙酯、丙酸正丁酯、丙酸异丁酯、丙酸正戊酯、丙酸异戊酯、正丁酸乙酯、正丁酸正丙酯、异丁酸丙酯、正丁酸正戊酯、异丁酸正戊酯、正丁酸正丁酯、异丁酸异丁酯、或正戊酸正戊酯。
  4. 根据权利要求1所述的电解液，其中，所述式(I)所示羧酸酯化合物包括丙酸丙酯和乙酸乙酯。
  5. 根据权利要求1所述的电解液，其中，所述电解液还包括腈类化合物，基于所述电解液的总重量，所述腈类化合物的含量为w 3，0.1％≤w 3≤12％。
  6. 根据权利要求5所述的电解液，其中，所述腈类化合物包括式(II)至式(V)所示化合物中的至少一种：
    N≡C——R 21—C≡N，
    式(II)
    Figure PCTCN2022094915-appb-100002
    Figure PCTCN2022094915-appb-100003
    其中，R 21包括取代或未取代的C1-C12的亚烷基或取代或未取代的C1-C12的亚烷氧基中的至少一者；
    R 31、R 32各自独立地包括氢、取代或未取代的C1-C12的亚烷基；
    R 41、R 42、R 43各自独立地包括氢、取代或未取代的C1-C12的亚烷基或取代或未取代的C1-C12的亚烷氧基；
    R 51包括取代或未取代的C1-C12的亚烷基、取代或未取代的C2-C12的亚烯基、取代或未取代的C6-C26的亚芳基或取代或未取代的C2-C12亚杂环基团，其中杂原子为N、S或O中的至少一者；
    其中经取代时，取代基为卤素。
  7. 根据权利要求5所述的电解液，其中，所述腈类化合物中的氰基(-CN)的摩尔总量为x，所述腈类化合物的摩尔总量为y，氰基富集度x/y满足2.16≤x/y≤2.71。
  8. 根据权利要求7所述的电解液，其中，所述氰基富集度x/y、所述式(I)所示羧酸酯化合物的含量w 1和所述FEC的含量w 2满足2w 1 2-0.01w 1+2.3＞x/y＞27w 2 2-1.2w 2+2.1。
  9. 根据权利要求1所述的电解液，其中，所述电解液包括锂盐，所述锂盐包括以下各者中的至少一者：LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB或LiDFOB。
  10. 一种电化学装置，其包括权利要求1-9中任一者所述的电解液。
  11. 根据权利要求10所述的电化学装置，所述电化学装置还包括正极、负极和位于所述正极和所述负极之间的隔膜，其中，所述正极、所述负极和所述隔膜经卷绕以形成电芯，所述电芯的长度L和宽度W满足20mm≤L≤300mm，20mm≤W≤100mm，且1≤L/W≤4。
  12. 据权利要求11所述的电化学装置，其满足如下特征中的至少一者：a).1≤L/W≤3；b)2≤L/W≤3；c)2≤L/W≤4。
  13. 根据权利要求10所述的电化学装置，其中，所述电化学装置还包括正极、负极和位于所述正极和所述负极之间的隔膜，其中，所述正极、所述负极和所述隔膜经卷绕以形成电芯，所述电芯的厚度T和宽度W满足2mm≤T≤12mm，W/T≥5。
  14. 根据权利要求13所述的电化学装置，其满足如下特征中的至少一者，d).5≤W/T≤25；e)5≤W/T≤20；f)5≤W/T≤15；g)10≤W/T≤25。
  15. 根据权利要求10所述的电化学装置，所述电化学装置还包括正极、负极和位于所述正极和所述负极之间的隔膜，其中，所述正极、所述负极和所述隔膜经卷绕以形成电芯，其中，所述电芯的长度L和宽度W以及所述式(I)所示羧酸酯化合物的含量w 1满足w 1×100/(L/W)≥10。
  16. 根据权利要求15所述的电化学装置，其满足如下特征中的至少一者：h).10≤w 1×100/(L/W)≤40；i).20≤w 1×100/(L/W)≤30；j)20≤w 1×100/(L/W)≤40；k).15≤w 1×100/(L/W)≤30。
  17. 一种电子装置，其包括权利要求10至16中任一者所述的电化学装置。
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