Electrochemical devices and electronic devices

Abstract

The present application relates to an electrochemical device and an electronic device. Specifically, the present application provides an electrochemical device, which includes a positive electrode, a negative electrode, and an electrolyte, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, the positive electrode active material layer includes a positive electrode active material, wherein the positive electrode active material includes lithium nickel cobalt manganese oxide containing aluminum, zirconium, and tungsten, and the electrolyte includes a dinitrile compound. The electrochemical device of the present application has improved overcharge resistance and safety at high temperature and high pressure.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of energy storage, in particular to an electrochemical device and an electronic device, especially a lithium ion battery. BACKGROUND

[0002] With the development of technology and the increasing demand for mobile devices, the demand for electrochemical devices (e.g., lithium ion batteries) under different use conditions has significantly increased, thereby putting forward higher requirements for the performance of lithium ion batteries, which are embodied in: higher capacity, appropriate cycle life, good high-temperature performance, good high-rate discharge performance, overcharge resistance and safety, etc.

[0003] When the lithium ion battery fails in the charging control circuit during use, overcharge is prone to occur, which leads to an increase in the internal pressure and temperature of the lithium ion battery, thereby possibly affecting the safety of the lithium ion battery.

[0004] Therefore, it is necessary to provide an electrochemical device and an electronic device with improved overcharge resistance and safety under high temperature and high pressure. SUMMARY

[0005] The embodiments of the present application provide an electrochemical device and an electronic device with improved overcharge resistance and safety under high temperature and high pressure to solve the problems existing in the prior art to some extent.

[0006] In one aspect of the present application, the present application provides an electrochemical device, comprising: a positive electrode, a negative electrode and an electrolyte, the positive electrode comprising a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material, wherein: the positive electrode active material comprises lithium nickel cobalt manganese oxide containing aluminum, zirconium and tungsten, and the electrolyte comprises a dinitrile compound.

[0007] According to the embodiments of the present application, based on the mass of the positive electrode active material, the contents of aluminum, zirconium and tungsten are a%, b% and c% respectively, and a, b and c satisfy: 0.1≤a+b+c≤1.

[0008] According to the embodiments of the present application, based on the mass of the positive electrode active material, the contents of aluminum, zirconium and tungsten are a%, b% and c% respectively, and a, b and c satisfy: 1≤(b+c) / a≤5.

[0009] According to the embodiments of the present application, based on the mass of the positive electrode active material, the contents of zirconium and tungsten are b% and c% respectively, and b and c satisfy: 1≤b / c≤3.

[0010] According to embodiments of the present application, the content of the tungsten is c% based on the mass of the positive electrode active material; the content of the dinitrile compound is x% based on the mass of the electrolyte; and c and x satisfy: 10≤x / c≤100.

[0011] According to embodiments of the present application, the electrolyte further comprises a trinitrile compound.

[0012] According to embodiments of the present application, the content of the dinitrile compound is x% and the content of the trinitrile compound is y% based on the mass of the electrolyte, and x and y satisfy: 1≤x+y≤15.

[0013] According to embodiments of the present application, x and y satisfy: 1≤x / y≤5.

[0014] According to embodiments of the present application, the electrolyte further comprises a compound having a sulfur-oxygen double bond, the content of the compound having a sulfur-oxygen double bond is z% based on the mass of the electrolyte; the content of the tungsten is c% based on the mass of the positive electrode active material; and z and c satisfy: 1≤z / c≤50.

[0015] According to embodiments of the present application, the compound having a sulfur-oxygen double bond comprises at least one of a bicyclic sulfate, a bicyclic sulfonolactone, a vinyl sulfate, a propylene sulfate, 1,3-propane sulfonolactone, 1,3-propylene sulfonolactone, methanediyl dimethanesulfonate, or methanediyl diethanesulfonate.

[0016] According to embodiments of the present application, the bicyclic sulfate comprises a compound of Formula I:

[0017]

[0018] wherein:

[0019] W is selected from

[0020] each L is independently selected from a single bond or a methylene group;

[0021] m is 1, 2, 3, or 4;

[0022] n is 0, 1, or 2; and

[0023] p is 0, 1, 2, 3, 4, 5, or 6.

[0024] According to embodiments of the present application, the compound of Formula I comprises at least one of:

[0025]

[0026]

[0027] According to embodiments of the present application, the bicyclic sulfolactone comprises a compound of Formula II:

[0028]

[0029] wherein each of A1, A2, A3, and A4 is independently selected from substituted or unsubstituted C1-3 alkylene, when substituted, the substituent is selected from C1-5 alkyl, halogen, or halogenated C1-5 alkyl.

[0030] According to embodiments of the present application, the compound of Formula II comprises at least one of the following:

[0031]

[0032] According to embodiments of the present application, the electrochemical device satisfies at least one of the following:

[0033] a) the aluminum content is a%, a ranges from 0.05 to 1, based on the mass of the positive electrode active material;

[0034] b) the zirconium content is b%, b ranges from 0.05 to 1, based on the mass of the positive electrode active material;

[0035] c) the tungsten content is c%, c ranges from 0.05 to 1, based on the mass of the positive electrode active material;

[0036] d) the dicyan compound content is x%, x ranges from 0.1 to 15, based on the mass of the electrolyte;

[0037] e) the electrolyte further comprises a tricyan compound, the tricyan compound content is y%, y ranges from 0.1 to 8, based on the mass of the electrolyte;

[0038] f) the electrolyte further comprises a compound having a sulfur-oxygen double bond, the compound having a sulfur-oxygen double bond content is z%, z ranges from 0.01 to 5, based on the mass of the electrolyte.

[0039] According to embodiments of the present application, the electrochemical device satisfies at least one of the following:

[0040] g) a ranges from 0.1 to 0.5;

[0041] h) b ranges from 0.1 to 0.5;

[0042] i) c ranges from 0.1 to 0.5;

[0043] j) x ranges from 0.5 to 10;

[0044] k) The value of y ranges from 0.5 to 5;

[0045] l) The value of z ranges from 0.1 to 3.

[0046] According to embodiments of this application, the electrolyte further includes at least one of lithium difluorophosphate or a compound of formula III.

[0047]

[0048] Where R is a single bond or a C1-4 alkylene group.

[0049] According to embodiments of this application, the electrolyte further includes at least one of fluoroethylene carbonate, vinylene carbonate, or 1-propyl cyclic phosphate anhydride.

[0050] In another aspect of this application, an electronic device is provided that includes an electrochemical device according to this application.

[0051] The positive electrode active material layer used in this application has improved interfacial stability under thermal runaway and can effectively suppress the overcharge resistance of the electrochemical device under high voltage and high temperature. At the same time, the use of an electrolyte including a dinitrile compound can significantly improve the safety of the electrochemical device.

[0052] Additional aspects and advantages of the embodiments of this application will be described, shown, or illustrated in part by way of implementation of the embodiments of this application in the following description. Detailed Implementation

[0053] The embodiments of this application will be described in detail below. These embodiments should not be construed as limiting the scope of this application.

[0054] Unless otherwise expressly stated, the terms used herein have the meanings indicated below.

[0055] In the detailed description and claims, the list of items connected by the term "at least one of" can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and 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, and 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 element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements. The term "at least one of" has the same meaning as the term "at least one of".

[0056] As used herein, the term "alkyl" is intended to refer to a straight-chain saturated hydrocarbon structure having 1 to 20 carbon atoms. "alkyl" is also intended to refer to a branched or cyclic hydrocarbon structure having 3 to 20 carbon atoms. When an alkyl group with a specific number of carbon atoms is specified, it is intended to encompass all geometric isomers having that number of carbon atoms; thus, for example, "butyl" means including n-butyl, sec-butyl, isobutyl, tert-butyl, and cyclobutyl; "propyl" includes n-propyl, isopropyl, and cyclopropyl. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, methylcyclopentyl, ethylcyclopentyl, n-hexyl, isohexyl, cyclohexyl, n-heptyl, octyl, cyclopropyl, cyclobutyl, norbornyl, etc.

[0057] As used herein, the term "alkylene" means a divalent saturated hydrocarbon group that may be straight-chain or branched. Unless otherwise defined, said alkylene typically contains 2 to 10 carbon atoms and includes, for example, -C. 2-3 Alkylene and -C 2-6 Alkylenes - Representative alkylenes 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, etc.

[0058] As used in this article, the term "halogen" refers to elements in Group VIIA of the periodic table, including fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).

[0059] Overcharging can easily occur when the charging control circuit of an electrochemical device (e.g., a lithium-ion battery) malfunctions during use. When the charging voltage reaches the decomposition voltage of the electrolyte, it causes the electrolyte to decompose at the positive electrode of the lithium-ion battery, generating gas, increasing the internal pressure of the lithium-ion battery, causing internal heat buildup and loss of stability, and seriously affecting battery safety. The main methods for overcharge protection of lithium-ion batteries include physical methods (e.g., integrated circuit protection) and chemical methods (e.g., overcharge protection additives). Integrated circuit protection is reliable, fast, and widely used; however, integrated circuits have complex structures, require plastic packaging, and are expensive. Overcharge protection additives typically use additives based on polymerization reactions, such as biphenyl and cyclohexylbenzene, or additives based on reductive-oxidative cycles, such as lithium halides, metallocenes and their derivatives, and benzene derivatives. However, biphenyl and cyclohexylbenzene increase the internal resistance of the lithium-ion battery, reducing its performance. Lithium halides, metallocenes and their derivatives, and benzene derivatives cannot effectively provide overcharge protection under high charging currents, and at the same time, they will reduce the cycle life and other performance of lithium-ion batteries.

[0060] The industry has seen the addition of aluminum, zirconium, or tungsten to cathode active materials to alter the surface energy of the material's microstructure, thereby significantly improving its cycle stability. However, there are no reports of adding aluminum, zirconium, or tungsten to cathode active materials to improve the safety of electrochemical devices. Furthermore, it is generally believed that using dinitrile compounds in the electrolyte can reduce the deposition of dissolved transition metal ions. Based on existing knowledge, it is impossible to predict the impact of simultaneously using cathode active materials containing aluminum, zirconium, and tungsten (lithium nickel cobalt manganese oxide) and electrolytes containing dinitrile compounds on the overcharge resistance and safety performance of electrochemical devices.

[0061] This application addresses the issues of overcharge resistance and safety performance in electrochemical devices by using lithium nickel cobalt manganese oxide (LCO) containing aluminum, zirconium, and tungsten as the positive electrode active material and an electrolyte containing a dinitrile compound. Doping LCO with aluminum, zirconium, and tungsten can suppress the phase transformation of LCO and effectively inhibit the delamination of the positive electrode active material under high temperature and pressure. Using an electrolyte containing a dinitrile compound not only effectively passivates the positive electrode surface but also stabilizes the bulk structure of the positive electrode active material. The specific combination of the positive electrode active material and electrolyte in this application not only effectively improves the overcharge resistance of the electrochemical device under high temperature and pressure but also significantly enhances the safety of the electrochemical device (e.g., short-circuit safety and thermal abuse safety).

[0062] I. Positive electrode

[0063] The positive electrode includes a positive current collector and a layer of positive active material formed on the positive current collector. The positive active material layer can be one or more layers. The positive active material layer includes positive active material, and each layer of the multilayer positive active material can contain the same or different positive active material.

[0064] A key feature of the electrochemical device of this application is that the positive electrode active material comprises lithium nickel cobalt manganese oxide containing aluminum, zirconium, and tungsten. Compared to lithium cobalt oxide, the crystal structure obtained by doping lithium nickel cobalt manganese oxide with aluminum, zirconium, and tungsten is more stable, which significantly improves the overcharge resistance and safety of the electrochemical device under high temperature and high pressure.

[0065] The inventors discovered that the simultaneous presence of aluminum, zirconium, and tungsten in the positive electrode active material can unexpectedly enhance the stability of the structure and electrode interface of the positive electrode active material under high voltage. Further adjustment of the content of these three elements can further improve overcharge resistance. Adjustments to the total content of aluminum, zirconium, and tungsten, or the ratio of the sum of zirconium and tungsten to aluminum, or the ratio of zirconium to tungsten, will cause changes in the bulk structure of the positive electrode material, changes in the surface coating structure, changes in the elemental content on the surface of the positive electrode material particles, and the stability of the interface between the positive electrode and the electrolyte, thus affecting the performance of the entire electrochemical device.

[0066] In some embodiments, based on the mass of the positive electrode active material, the contents of aluminum, zirconium, and tungsten are a%, b%, and c%, respectively, and a, b, and c satisfy: 0.1 ≤ a + b + c ≤ 1. In some embodiments, 0.2 ≤ a + b + c ≤ 0.8. In some embodiments, 0.3 ≤ a + b + c ≤ 0.5. In some embodiments, a + b + c is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or within a range consisting of any two of the above values. When the contents of aluminum, zirconium, and tungsten in the positive electrode active material satisfy the above relationships, the stability of the lithium nickel cobalt manganese oxide crystal structure under high voltage can be effectively maintained, and the continuous damage to the passivation layer on the positive electrode surface during charge-discharge cycles of lithium-ion batteries can be effectively suppressed, reducing the number of repairs. Especially in the presence of compounds with nitrile groups, the interfacial stability of the positive electrode active material layer can be more fully improved, thereby helping to further improve the overcharge resistance and safety of electrochemical devices under high temperature and high pressure.

[0067] In some embodiments, based on the mass of the positive electrode active material, the contents of aluminum, zirconium, and tungsten are a%, b%, and c%, respectively, and a, b, and c satisfy: 1 ​​≤ (b+c) / a ≤ 5. In some embodiments, 1 ≤ (b+c) / a ≤ 4. In some embodiments, 2 ≤ (b+c) / a ≤ 3. In some embodiments, (b+c) / a is 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, or within a range consisting of any two of the above values. When the contents of aluminum, zirconium, and tungsten in the positive electrode active material satisfy the above relationships, it helps to further improve the structural stability of the positive electrode active material layer during the cycling process of the electrochemical device, thereby further improving the overcharge resistance and safety of the electrochemical device under high temperature and high pressure.

[0068] In some embodiments, based on the mass of the positive electrode active material, the contents of zirconium and tungsten are b% and c%, respectively, and b and c satisfy: 1 ​​≤ b / c ≤ 3. In some embodiments, 1 ≤ b / c ≤ 2.5. In some embodiments, 1 ≤ b / c ≤ 2. In some embodiments, b / c is 1, 1.5, 2, 2.5, 3, or within a range consisting of any two of the above values. When the contents of zirconium and tungsten in the positive electrode active material satisfy the above relationship, it helps to further improve the structural stability of the positive electrode active material layer during the cycling process of the electrochemical device, thereby further improving the overcharge resistance and safety of the electrochemical device under high temperature and high pressure.

[0069] In some embodiments, the aluminum content is a%, based on the mass of the positive electrode active material, where a ranges from 0.05 to 1. In some embodiments, a ranges from 0.1 to 0.5. In some embodiments, a is 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or within any two of the above values. When the aluminum content in the positive electrode active material is within the above range, it helps to further improve the structural stability of the positive electrode active material layer during the cycling process of the electrochemical device, thereby further improving the overcharge resistance and safety of the electrochemical device under high temperature and high pressure.

[0070] In some embodiments, the zirconium content is b%, based on the mass of the positive electrode active material, with b ranging from 0.05 to 1. In some embodiments, the zirconium content ranges from 0.1 to 0.5. In some embodiments, b is 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or within a range of any two of the above values. When the zirconium content in the positive electrode active material is within the above range, it helps to further improve the structural stability of the positive electrode active material layer during the cycling process of the electrochemical device, thereby further improving the overcharge resistance and safety of the electrochemical device under high temperature and high pressure.

[0071] In some embodiments, the tungsten content is c%, based on the mass of the positive electrode active material, and c ranges from 0.05 to 1. In some embodiments, c is 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or within a range of any two of the above values. When the tungsten content in the positive electrode active material is within the above range, it helps to further improve the structural stability of the positive electrode active material layer during the cycling process of the electrochemical device, thereby further improving the overcharge resistance and safety of the electrochemical device under high temperature and high pressure.

[0072] In some embodiments, a substance with a different composition may be attached to the surface of the aforementioned positive electrode active material. Examples of such surface-attached substances may include, but are not limited to: oxides such as aluminum oxide, silicon dioxide, titanium dioxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate; and carbon. By attaching 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 improving the lifespan of the electrochemical device. When the amount of surface-attached substance is too small, its effect cannot be fully realized; when the amount of surface-attached substance is too large, it will hinder the entry and exit of lithium ions, and thus the resistance may sometimes increase. In this application, the positive electrode active material to which a substance with a different composition is attached to the surface of the positive electrode active material is also referred to as "positive electrode active material".

[0073] In some embodiments, the shape of the positive electrode active material particles includes, but is not limited to, blocky, polyhedral, spherical, ellipsoidal, plate-like, needle-like, and columnar shapes. In some embodiments, the positive electrode active material particles include primary particles, secondary particles, or combinations thereof. In some embodiments, primary particles may aggregate to form secondary particles.

[0074] There are no restrictions on the type of positive electrode conductive material; any known conductive material can be used. Examples of positive electrode conductive materials include, but are not limited to, graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; carbon materials such as amorphous carbon such as needle coke; carbon nanotubes; graphene, etc. The above-mentioned positive electrode conductive materials can be used alone or in any combination.

[0075] There are no particular restrictions on the type of positive electrode binder used in the manufacture of the positive electrode active material layer. In the case of a coating method, any material that can be dissolved or dispersed in the liquid medium used during electrode manufacturing is acceptable. Examples of positive electrode binders may include, but are not limited to, one or more of the following: resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; rubber-like polymers such as styrene-butadiene rubber (SBR), nitrile rubber (NBR), fluororubber, isoprene rubber, polybutadiene rubber, and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers or their hydrides, and ethylene-propylene-diene terpolymers (EPDM). The above-mentioned positive electrode adhesives include thermoplastic elastomers such as styrene-ethylene-butadiene-ethylene copolymers, styrene-isoprene-styrene block copolymers, or their hydrides; soft resinous polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorinated polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; and polymeric compositions with ion conductivity of alkali metal ions (especially lithium ions). These positive electrode adhesives can be used alone or in any combination.

[0076] There are no restrictions on the type of solvent used to form the positive electrode slurry, as long as it can dissolve or disperse the positive electrode active material, conductive material, positive electrode binder, and thickener used as needed. Examples of solvents used to form the positive electrode slurry can include any of aqueous solvents and organic solvents. Examples of aqueous media can include, but are not limited to, water and mixtures of alcohol and water. Examples of organic media can 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; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, and tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide.

[0077] Thickeners are typically used to adjust the viscosity of slurries. In the case of aqueous media, thickeners and styrene-butadiene rubber (SBR) latex can be used for slurry preparation. There are no particular limitations on the types of thickeners; examples include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and their salts. The above-mentioned thickeners can be used alone or in any combination.

[0078] There are no particular limitations on the type of positive electrode current collector; it can be any material known to be suitable for use as a positive electrode current collector. Examples of positive electrode current collectors may include, but are not limited to, metallic materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper. In some embodiments, the positive electrode current collector is a metallic material. In some embodiments, the positive electrode current collector is aluminum.

[0079] To reduce the electronic contact resistance between the positive current collector and the positive active material layer, the surface of the positive current collector may include a conductive additive. Examples of conductive additives may include, but are not limited to, carbon and precious metals such as gold, platinum, and silver.

[0080] The positive electrode can be manufactured by forming a layer of positive electrode active material containing positive electrode active material and binder on a current collector. The manufacture of a positive electrode using positive electrode active material can be carried out by conventional methods, namely, dry mixing the positive electrode active material, binder, and conductive material and thickener as needed, forming a sheet, and pressing the resulting sheet onto the positive electrode current collector; or dissolving or dispersing these materials in a liquid medium to form a slurry, coating the slurry onto the positive electrode current collector and drying it, thereby forming a layer of positive electrode active material on the current collector, thus obtaining the positive electrode.

[0081] In some embodiments, the mass fraction of the positive electrode active material in the positive electrode active material layer is 95%, preferably 96%, and more preferably 97%. In some embodiments, the mass fraction of the positive electrode active material in the positive electrode active material layer is 98%. In some embodiments, the mass fraction of the positive electrode active material in the positive electrode active material layer is 99%. When the mass fraction of the positive electrode active material in the positive electrode active material layer is within the above ranges, the energy density of the electrochemical device can be significantly improved.

[0082] When the positive electrode active material consists of primary particles, the average particle size refers to the primary particle size. When the primary particles of the positive electrode active material agglomerate to form secondary particles, the average particle size refers to the secondary particle size.

[0083] In some embodiments, the average particle size of the positive electrode active material is D μm, where D ranges from 5 to 30. In some embodiments, D ranges from 10 to 25. In some embodiments, D ranges from 12 to 20. In some embodiments, D is 5, 7, 9, 10, 12, 15, 18, 20, 25, 30, or within a range consisting of any two of the above values.

[0084] When the average particle size of the positive electrode active material is within the above-mentioned range, a positive electrode active material with high tap density can be obtained, which can suppress the degradation of the performance of the electrochemical device and prevent problems such as streaking during the preparation of the positive electrode of the electrochemical device (i.e., when the positive electrode active material, conductive material, and binder are slurried with solvent and coated in a thin film). Mixing two or more positive electrode active materials with different average particle sizes can further improve the filling properties during positive electrode preparation.

[0085] The average particle size of the positive electrode active material can be determined using a laser diffraction / scattering particle size analyzer: Using a HORIBA LA-920 particle size analyzer, a 0.1% sodium hexametaphosphate aqueous solution was used as the dispersion medium. After ultrasonic dispersion for 5 minutes, the refractive index was set to 1.24 for measurement. The average particle size of the positive electrode active material can also be measured using a laser diffraction particle size analyzer (Shimadzu SALD-2300) and a scanning electron microscope (ZEISS EVO18, with at least 100 samples).

[0086] II. Electrolyte

[0087] The electrolyte used in the electrochemical device of this application includes an electrolyte and a solvent for dissolving the electrolyte. Another key feature of the electrochemical device of this application is that the electrolyte includes a dinitrile compound.

[0088] In some embodiments, the dinitrile compound comprises butadienenitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, tetramethylbutadienenitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, ethylene glycol bis(propionitrile) ether, 3,5-dioxa-heptanenitrile, 1,4-di(cyanoethoxy)butane, diethylene glycol di(2-cyanoethyl) ether, triethylene glycol di(2-cyanoethyl) ether, tetraethylene glycol di(2-... At least one of the following dicyanoethyl ethers, 1,3-di(2-cyanoethoxy)propane, 1,4-di(2-cyanoethoxy)butane, 1,5-di(2-cyanoethoxy)pentane, ethylene glycol di(4-cyanobutyl) ether, 1,4-dicyano-2-butene, 1,4-dicyano-2-methyl-2-butene, 1,4-dicyano-2-ethyl-2-butene, 1,4-dicyano-2,3-dimethyl-2-butene, 1,4-dicyano-2,3-diethyl-2-butene, 1,6-dicyano-3-hexene, or 1,6-dicyano-2-methyl-3-hexene. The above dicyanonitrile compounds may be used alone or in any combination.

[0089] In some embodiments, the content of the dinitrile compound is x% based on the mass of the electrolyte; and c and x satisfy: 10 ≤ x / c ≤ 100. In some embodiments, 10 ≤ x / c ≤ 80. In some embodiments, 20 ≤ x / c ≤ 80. In some embodiments, x / c is 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100 or within a range of any two of the above values. When the content of tungsten in the positive electrode active material and the content of the dinitrile compound in the electrolyte satisfy the above relationship, it helps to further improve the overcharge resistance and safety of the electrochemical device under high temperature and high pressure.

[0090] In some embodiments, the electrolyte further includes a trinitrile compound.

[0091] In some embodiments, the trinitrile compound comprises at least one selected from 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane, or 1,2,5-tris(cyanoethoxy)pentane. The above trinitrile compounds may be used alone or in any combination.

[0092] In some embodiments, based on the mass of the electrolyte, the content of the dinitrile compound is x%, and the content of the trinitrile compound is y%, where x and y satisfy: 1 ​​≤ x + y ≤ 15. In some embodiments, 2 ≤ x + y ≤ 12. In some embodiments, 3 ≤ x + y ≤ 10. In some embodiments, x + y is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or falls within a range consisting of any two of the above values. When the contents of the dinitrile compound and the trinitrile compound in the electrolyte satisfy the above relationship, it helps to further improve the overcharge resistance and safety of the electrochemical device under high temperature and high pressure.

[0093] In some embodiments, the content of the dinitrile compound is x%, based on the mass of the electrolyte, where x ranges from 0.1 to 15. In some embodiments, x ranges from 1 to 10. In some embodiments, x ranges from 2 to 8. In some embodiments, x ranges from 3 to 5. In some embodiments, x is 0.1, 0.5, 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, or within a range consisting of any two of the above values. When the content of the dinitrile compound in the electrolyte is within the above ranges, it helps to further improve the overcharge resistance and safety of the electrochemical device under high temperature and high pressure.

[0094] In some embodiments, the content of the trinitrile compound is y%, based on the mass of the electrolyte, and y ranges from 0.1 to 8. In some embodiments, y ranges from 0.5 to 6. In some embodiments, y ranges from 1 to 5. In some embodiments, y is 0.1, 0.5, 1, 1.5, 2, 3, 4, 5, 6, 7, 8, or within a range consisting of any two of the above values. When the content of the trinitrile compound in the electrolyte is within the above range, it helps to further improve the overcharge resistance and safety of the electrochemical device under high temperature and high pressure.

[0095] In some embodiments, the electrolyte further includes a compound having a sulfur-oxygen double bond.

[0096] In some embodiments, the sulfur-oxygen double bond-containing compound includes at least one of the following compounds: cyclic sulfate, chain sulfate, chain sulfonate, cyclic sulfonate, chain sulfite, or cyclic sulfite.

[0097] In some embodiments, the cyclic sulfate esters include, but are not limited to, one or more of the following: 1,2-ethylene glycol sulfate, 1,2-propanediol sulfate, 1,3-propanediol sulfate, 1,2-butanediol sulfate, 1,3-butanediol sulfate, 1,4-butanediol sulfate, 1,2-pentanediol sulfate, 1,3-pentanediol sulfate, 1,4-pentanediol sulfate, and 1,5-pentanediol sulfate, etc.

[0098] In some embodiments, the chain sulfate ester includes, but is not limited to, one or more of the following: dimethyl sulfate, methyl ethyl sulfate, and diethyl sulfate, etc.

[0099] In some embodiments, the chain sulfonate includes, but is not limited to, one or more of the following: fluorosulfonates such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, butyl dimethanesulfonate, methyl 2-(methanesulfonyloxy)propionate and ethyl 2-(methanesulfonyloxy)propionate, etc.

[0100] In some embodiments, the cyclic sulfonate ester includes, but is not limited to, one or more of the following: 1,3-propanesulfonate lactone, 1-fluoro-1,3-propanesulfonate lactone, 2-fluoro-1,3-propanesulfonate lactone, 3-fluoro-1,3-propanesulfonate lactone, 1-methyl-1,3-propanesulfonate lactone, 2-methyl-1,3-propanesulfonate lactone, 3-methyl-1,3-propanesulfonate lactone, 1-propene-1,3-sulfonate lactone, 2-propene-1,3-sulfonate lactone, 1-fluoro-1-propene-1,3-sulfonate lactone, 2-fluoro-1-propene-1,3-sulfonate lactone, 3-fluoro-1-propene-1,3-sulfonate lactone Esters, 1-fluoro-2-propene-1,3-sulfonate lactone, 2-fluoro-2-propene-1,3-sulfonate lactone, 3-fluoro-2-propene-1,3-sulfonate lactone, 1-methyl-1-propene-1,3-sulfonate lactone, 2-methyl-1-propene-1,3-sulfonate lactone, 3-methyl-1-propene-1,3-sulfonate lactone, 1-methyl-2-propene-1,3-sulfonate lactone, 2-methyl-2-propene-1,3-sulfonate lactone, 3-methyl-2-propene-1,3-sulfonate lactone, 1,4-butanesulfonate lactone, 1,5-pentanesulfonate lactone, methylene disulfonate, and ethylene disulfonate, etc.

[0101] In some embodiments, the chain sulfite includes, but is not limited to, one or more of the following: dimethyl sulfite, methyl ethyl sulfite, and diethyl sulfite, etc.

[0102] In some embodiments, the cyclic sulfites include, but are not limited to, one or more of the following: 1,2-ethylene glycol sulfite, 1,2-propanediol sulfite, 1,3-propanediol sulfite, 1,2-butanediol sulfite, 1,3-butanediol sulfite, 1,4-butanediol sulfite, 1,2-pentanediol sulfite, 1,3-pentanediol sulfite, 1,4-pentanediol sulfite, and 1,5-pentanediol sulfite, etc.

[0103] In some embodiments, the compound having a sulfur-oxygen double bond includes at least one of bicyclic sulfate, bicyclic sulpholactone, vinyl sulfate, propylene sulfate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, methylene disulfonate, or ethylene disulfonate.

[0104] In some embodiments, the bicyclic sulfate comprises a compound of formula I:

[0105]

[0106] in:

[0107] W selected

[0108] L are each independently selected from single bonds or methylene groups;

[0109] m can be 1, 2, 3, or 4;

[0110] n is 0, 1, or 2; and

[0111] p can be 0, 1, 2, 3, 4, 5, or 6.

[0112] In some embodiments, the compound of formula I includes at least one of the following:

[0113]

[0114] In some embodiments, the bicyclic sulfonyl lactone comprises a compound of formula II:

[0115]

[0116] A1, A2, A3 and A4 are each independently selected from substituted or unsubstituted C1-3 alkylene groups. When substituted, the substituents are selected from C1-5 alkyl, halogen or halo-C1-5 alkyl groups.

[0117] In some embodiments, the compound of formula II comprises at least one of the following:

[0118]

[0119]

[0120] In some embodiments, the content of the compound having a sulfur-oxygen double bond is z% based on the mass of the electrolyte; and z and c satisfy: 1 ​​≤ z / c ≤ 50. In some embodiments, 5 ≤ z / c ≤ 40. In some embodiments, 10 ≤ z / c ≤ 35. In some embodiments, 15 ≤ z / c ≤ 30. In some embodiments, 20 ≤ z / c ≤ 25. In some embodiments, z / c is 1, 2, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50 or within a range consisting of any two of the above values. When the content of the compound having a sulfur-oxygen double bond in the electrolyte and the content of tungsten in the positive electrode active material satisfy the above relationship, it helps to further improve the overcharge resistance and safety of the electrochemical device under high temperature and high pressure.

[0121] In some embodiments, based on the mass of the electrolyte, the content of the compound having a sulfur-oxygen double bond is z%, where z ranges from 0.01 to 5. In some embodiments, z ranges from 0.1 to 3. In some embodiments, z ranges from 0.5 to 1. In some embodiments, z is 0.01, 0.1, 0.5, 1, 1.5, 2, 3, 4, 5, or within a range consisting of any two of the above values. When the content of the compound having a sulfur-oxygen double bond in the electrolyte is within the above range, it helps to further improve the overcharge resistance and safety of the electrochemical device under high temperature and high pressure.

[0122] In some embodiments, the electrolyte further includes lithium difluorophosphate or at least one of a compound of formula III.

[0123]

[0124] Where R is a single bond or a C1-4 alkylene group.

[0125] In some embodiments, the compound of formula III includes the compound of formula III-1:

[0126]

[0127] In some embodiments, the content of the Formula III compound is 0.1%-2% based on the mass of the electrolyte. In some embodiments, the content of the Formula III compound is 0.1%-0.5% based on the mass of the electrolyte.

[0128] In some embodiments, the electrolyte further includes at least one of fluoroethylene carbonate, vinylene carbonate, or 1-propyl cyclic phosphate anhydride. These compounds help stabilize the interface between the cathode and the electrolyte, thereby further improving the overcharge resistance and safety of the electrochemical device under high temperature and high pressure.

[0129] In some embodiments, the content of fluoroethylene carbonate, vinylene carbonate, or 1-propyl cyclic anhydride is 0.1%-6% based on the mass of the electrolyte. In some embodiments, the content of fluoroethylene carbonate, vinylene carbonate, or 1-propyl cyclic anhydride is 0.5%-5% based on the mass of the electrolyte. In some embodiments, the content of fluoroethylene carbonate, vinylene carbonate, or 1-propyl cyclic anhydride is 1%-3% based on the mass of the electrolyte.

[0130] In some embodiments, the electrolyte further comprises any non-aqueous solvent known in the art that can be used as a solvent for an electrolyte.

[0131] In some embodiments, the non-aqueous solvent includes, but is not limited to, one or more of the following: cyclic carbonates, chain carbonates, cyclic carboxylic esters, chain carboxylic esters, cyclic ethers, chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and aromatic fluorine-containing solvents.

[0132] In some embodiments, examples of the cyclic carbonate may include, but are not limited to, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate. In some embodiments, the cyclic carbonate has 3-6 carbon atoms.

[0133] In some embodiments, 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 n-propyl carbonate, ethyl n-propyl carbonate, di n-propyl carbonate, and other chain carbonates. Examples of fluorine-substituted chain carbonates may include, but are not limited to, one or more of the following: bis(fluoromethyl) carbonate, bis(difluoromethyl) carbonate, bis(trifluoromethyl) carbonate, bis(2-fluoroethyl) carbonate, bis(2,2-difluoroethyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 2-fluoroethylmethyl carbonate, 2,2-difluoroethylmethyl carbonate, and 2,2,2-trifluoroethylmethyl carbonate, etc.

[0134] In some embodiments, examples of the cyclic carboxylic acid ester may include, but are not limited to, one or more of the following: γ-butyrolactone and γ-valerolactone. In some embodiments, some hydrogen atoms of the cyclic carboxylic acid ester may be substituted with fluorine.

[0135] In some embodiments, examples of the chain carboxylic acid ester may include, but are not limited to, one or more of the following: methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate, and ethyl pivalate. In some embodiments, some hydrogen atoms of the chain carboxylic acid ester may be substituted with fluorine. In some embodiments, examples of fluorinated chain carboxylic acid esters may include, but are not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and 2,2,2-trifluoroethyl trifluoroacetate.

[0136] In some embodiments, 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.

[0137] In some embodiments, 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-ethoxymethoxyethane, and 1,2-ethoxymethoxyethane, etc.

[0138] In some embodiments, 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 diethyl phosphate, ethylene phosphate, ethylene phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tri(2,2,2-trifluoroethyl) phosphate, and tri(2,2,3,3,3-pentafluoropropyl) phosphate, etc.

[0139] In some embodiments, examples of the sulfur-containing organic solvent may include, but are not limited to, one or more of the following: sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethyl sulfone, diethyl sulfone, ethyl methyl sulfone, methylpropyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate, and dibutyl sulfate. In some embodiments, some hydrogen atoms of the sulfur-containing organic solvent may be substituted with fluorine.

[0140] In some embodiments, the aromatic fluorinated solvent includes, but is not limited to, one or more of the following: fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and trifluoromethylbenzene.

[0141] In some embodiments, the solvent used in the electrolyte of this application includes cyclic carbonates, linear carbonates, cyclic carboxylic acid esters, linear carboxylic acid esters, and combinations thereof. In some embodiments, the solvent used in the electrolyte of this application comprises an organic solvent selected from the group consisting of: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, n-propyl acetate, ethyl acetate, and combinations thereof. In some embodiments, the solvent used in the electrolyte of this application comprises: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, γ-butyrolactone, and combinations thereof.

[0142] In some embodiments, the electrolyte is not particularly limited, and any substance known as an electrolyte can be used. In the case of lithium secondary batteries, lithium salts are typically used. Examples of electrolytes may include, but are not limited to, inorganic lithium salts such as LiPF6, LiBF4, LiClO4, LiAlF4, LiSbF6, and LiWF7; lithium tungstates such as LiWOF5; lithium carboxylate salts such as HCO2Li, CH3CO2Li, CH2FCO2Li, CHF2CO2Li, CF3CO2Li, CF3CH2CO2Li, CF3CF2CO2Li, CF3CF2CF2CO2Li, and CF3CF2CF2CF2CO2Li; and lithium carboxylate salts such as FSO3Li and CH3SO3Li. Lithium sulfonate salts such as CH2FSO3Li, CHF2SO3Li, CF3SO3Li, CF3CF2SO3Li, CF3CF2CF2SO3Li, and CF3CF2CF2CF2SO3Li; lithium sulfonate salts such as LiN(FCO)2, LiN(FCO)(FSO2), LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethane disulfonylimide lithium, and cyclic 1,3-perfluoropropane disulfonylimide. Lithium, imide lithium salts such as LiN(CF3SO2)(C4F9SO2); methylated lithium salts such as LiC(FSO2)3, LiC(CF3SO2)3, and LiC(C2F5SO2)3; lithium malonate lithium salts such as bis(malonate)borate and difluoro(malonate)borate; lithium tri(malonate)phosphate, lithium difluorobis(malonate)phosphate, and lithium tetrafluoro(malonate)phosphate; and lithium malonate phosphates such as LiPF4(CF3)2 and LiPF4(C2F5)2. Fluorine-containing organic lithium salts such as LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF3CF3, LiBF3C2F5, LiBF3C3F7, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, and LiBF2(C2F5SO2)2; lithium oxalate borate salts such as lithium difluorooxalate borate and lithium bis(oxalate) borate; and lithium oxalate phosphate salts such as lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalate) phosphate, and lithium tri(oxalate) phosphate.

[0143] In some embodiments, the electrolyte is selected from LiPF6, LiSbF6, FSO3Li, CF3SO3Li, LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethane disulfonylimide lithium, cyclic 1,3-perfluoropropane disulfonylimide lithium, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, LiPF3(C2F5)3, lithium difluorooxalateborate, lithium bis(oxalate)borate, or lithium difluorobis(oxalate)phosphate, which helps to improve the output power characteristics, high-rate charge-discharge characteristics, high-temperature storage characteristics, and cycle characteristics of the electrochemical device.

[0144] There are no particular limitations on the content of the electrolyte, as long as it does not impair the effectiveness of this application. In some embodiments, the total molar concentration of lithium in the electrolyte is greater than 0.3 mol / L, greater than 0.4 mol / L, or greater than 0.5 mol / L. In some embodiments, the total molar concentration of lithium in the electrolyte is less than 3 mol / L, less than 2.5 mol / L, or less than 2.0 mol / L. In some embodiments, the total molar concentration of lithium in the electrolyte is within the range of any two of the above values. When the electrolyte concentration is within the above range, the amount of lithium as charged particles will not be too low, and the viscosity can be kept within an appropriate range, thus easily ensuring good conductivity.

[0145] When using two or more electrolytes, the electrolyte comprises at least one salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate. In some embodiments, the electrolyte comprises a salt selected from the group consisting of monofluorophosphate, oxalate, and fluorosulfonate. In some embodiments, the electrolyte comprises a lithium salt. In some embodiments, the content of a salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is greater than 0.01% or greater than 0.1% based on the weight of the electrolyte. In some embodiments, the content of a salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is less than 20% or less than 10% based on the weight of the electrolyte. In some embodiments, the content of a salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is within the range of any two of the above values.

[0146] In some embodiments, the electrolyte comprises one or more substances selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates, and one or more other salts. Examples of other salts include lithium salts exemplified above, and in some embodiments, LiPF6, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethane disulfonylimide lithium, cyclic 1,3-perfluoropropane disulfonylimide lithium, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, and LiPF3(C2F5)3. In some embodiments, the other salt is LiPF6.

[0147] In some embodiments, the content of other salts, based on the weight of the electrolyte, is greater than 0.01% or greater than 0.1%. In some embodiments, the content of other salts, based on the weight of the electrolyte, is less than 20%, less than 15%, or less than 10%. In some embodiments, the content of other salts is within the range of any two of the above values. The presence of other salts at the above-mentioned levels helps to balance the conductivity and viscosity of the electrolyte.

[0148] III. Negative electrode

[0149] The negative electrode includes a negative electrode current collector and a positive electrode active material layer disposed on one or both surfaces of the negative electrode current collector, the negative electrode active material layer containing negative electrode active material. The negative electrode active material layer can be one or more layers, and each layer in multiple layers can contain the same or different negative electrode active materials. The negative electrode active material is any material capable of reversibly inserting and deintercalating metal ions such as lithium ions. In some embodiments, the rechargeable capacity of the negative electrode active material is greater than the discharge capacity of the positive electrode active material to prevent unintentional deposition of lithium metal on the negative electrode during charging.

[0150] As the current collector for retaining the active material of the negative electrode, any known current collector can be used. Examples of negative electrode current collectors include, but are not limited to, metallic materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. In some embodiments, the negative electrode current collector is copper.

[0151] When the negative electrode current collector is a metallic material, its form 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. In some embodiments, the negative electrode current collector is a metal film. In some embodiments, the negative electrode current collector is copper foil. In some embodiments, the negative electrode current collector is rolled copper foil based on rolling or electrolytic copper foil based on electrolysis.

[0152] In some embodiments, the thickness of the negative electrode current collector is greater than 1 μm or greater than 5 μm. In some embodiments, the thickness of the negative electrode current collector is less than 100 μm or less than 50 μm. In some embodiments, the thickness of the negative electrode current collector is within the range of any two of the above values.

[0153] There are no particular restrictions on the negative electrode active material, as long as it can reversibly absorb and release lithium ions. Examples of negative electrode 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. Negative electrode active materials can be used alone or in combination.

[0154] The negative electrode active material layer may also include a negative electrode binder. The negative electrode binder improves the bonding between the negative electrode active material particles and the bonding between the negative electrode active material and the current collector. There are no particular limitations on the type of negative electrode binder, as long as it is a material stable to the electrolyte or the solvent used in electrode manufacturing. In some embodiments, the negative electrode binder includes a resin binder. Examples of resin binders include, but are not limited to, fluoropolymers, polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, etc. When a negative electrode slurry is prepared using an aqueous solvent, the negative electrode binder includes, but is not limited to, carboxymethyl cellulose (CMC) or its salts, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or its salts, polyvinyl alcohol, etc.

[0155] The negative electrode can be prepared by coating a negative electrode slurry containing negative electrode active material, resin binder, etc. onto a negative electrode current collector, drying it, and then calendering it to form a negative electrode active material layer on both sides of the negative electrode current collector, thereby obtaining the negative electrode.

[0156] IV. Separator

[0157] To prevent short circuits, a separator is typically placed between the positive and negative electrodes. In this case, the electrolyte of this application is typically used after penetrating into the separator.

[0158] There are no particular limitations on the material and shape of the separator, as long as it does not significantly impair the effectiveness of this application. The separator may be a resin, glass fiber, inorganic material, or other material formed from a material stable to the electrolyte of this application. In some embodiments, the separator includes a porous sheet or non-woven fabric-like material with excellent liquid retention properties. Examples of materials for resin or glass fiber separators may include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc. In some embodiments, the polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The above-mentioned separator materials can be used alone or in any combination.

[0159] The separator can also be a material formed by laminating the above-mentioned materials, examples of which include, but are not limited to, a three-layer separator formed by laminating polypropylene, polyethylene, and polypropylene in that order.

[0160] Examples of inorganic materials may include, but are not limited to, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates (e.g., barium sulfate, calcium sulfate, etc.). Inorganic materials may be in, but are not limited to, particulate or fibrous forms.

[0161] The separator can be in the form of a thin film, examples of which include, but are not limited to, nonwoven fabrics, woven fabrics, microporous membranes, etc. In the form of a thin film, the pore size of the separator is 0.01 μm to 1 μm, and the thickness is 5 μm to 50 μm. In addition to the above-mentioned independent thin film separator, the following separator can also be used: a separator formed by using a resin-based adhesive to form a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and / or negative electrode, for example, a separator formed by using fluororesin as an adhesive to form a porous layer of alumina particles with a particle size of less than 1 μm on both sides of the positive electrode.

[0162] The thickness of the separator is arbitrary. In some embodiments, the thickness of the separator is greater than 1 μm, greater than 5 μm, or greater than 8 μm. In some embodiments, the thickness of the separator is less than 50 μm, less than 40 μm, or less than 30 μm. In some embodiments, the thickness of the separator is within the range of any two of the above values. When the thickness of the separator is within the above range, insulation and mechanical strength can be ensured, and the rate capability and energy density of the electrochemical device can be ensured.

[0163] When using porous materials such as porous sheets or nonwoven fabrics as the separator, the porosity of the separator is arbitrary. In some embodiments, the porosity of the separator is greater than 10%, greater than 15%, or greater than 20%. In some embodiments, the porosity of the separator is less than 60%, less than 50%, or less than 45%. In some embodiments, the porosity of the separator is within the range of any two of the above values. When the porosity of the separator is within the above range, insulation and mechanical strength can be ensured, and membrane resistance can be suppressed, giving the electrochemical device good safety characteristics.

[0164] The average pore size of the separator is also arbitrary. In some embodiments, the average pore size of the separator is less than 0.5 μm or less than 0.2 μm. In some embodiments, the average pore size of the separator is greater than 0.05 μm. In some embodiments, the average pore size of the separator is within the range of any two of the above values. If the average pore size of the separator exceeds the above range, a short circuit is likely to occur. When the average pore size of the separator is within the above range, the electrochemical device has good safety characteristics.

[0165] V. Electrochemical device assembly

[0166] Electrochemical device components include electrode arrays, current collectors, housings, and protective elements.

[0167] The electrode assembly can be either a laminated structure formed by stacking the positive and negative electrodes with the separator membrane in between, or a structure formed by spirally winding the positive and negative electrodes with the separator membrane in between. In some embodiments, the proportion of the electrode assembly's mass in the battery's internal volume (electrode assembly occupancy) is greater than 40% or greater than 50%. In some embodiments, the electrode assembly occupancy is less than 90% or less than 80%. In some embodiments, the electrode assembly occupancy falls within the range of any two of the above values. When the electrode assembly occupancy is within the above range, the capacity of the electrochemical device can be ensured, while suppressing the degradation of characteristics such as repeated charge-discharge performance and high-temperature storage associated with increased internal pressure.

[0168] There are no particular limitations on the current collector structure. In some embodiments, the current collector structure is one that reduces the resistance of the wiring portion and the joint portion. When the electrode group has the above-described laminated structure, it is suitable to use a structure formed by bundling the metal core portions of each electrode layer together and soldering them to the terminals. As the area of ​​an electrode increases, the internal resistance increases; therefore, it is also suitable to provide two or more terminals within the electrode to reduce the resistance. When the electrode group has the above-described wound structure, the internal resistance can be reduced by providing two or more lead structures on the positive and negative electrodes respectively and bundling them together on the terminals.

[0169] There are no particular restrictions on the material of the outer casing, as long as it is a substance stable to the electrolyte used. The outer casing can be, but is not limited to, nickel-plated steel, stainless steel, aluminum or aluminum alloy, magnesium alloy, or a laminated film of resin and aluminum foil. In some embodiments, the outer casing is an aluminum or aluminum alloy metal or a laminated film.

[0170] Metal casings include, but are not limited to, encapsulated and hermetically sealed structures formed by fusing metals together using laser welding, resistance welding, or ultrasonic welding; or riveted structures formed using the aforementioned metals with a resin gasket in between. Casings using the aforementioned laminated films include, but are not limited to, encapsulated and hermetically sealed structures formed by thermally bonding resin layers together. To improve sealing, a resin different from the resin used in the laminated film can be sandwiched between the resin layers. When forming a hermetically sealed structure by thermally bonding resin layers using current collectors, a resin with polar groups or a modified resin with introduced polar groups can be used as the sandwiched resin due to the bonding between the metal and the resin. Furthermore, the shape of the casing is arbitrary, and can be, for example, any of the following: cylindrical, square, laminated, button-shaped, or large.

[0171] Protective components can include positive temperature coefficient (PTC) devices that increase resistance when abnormal heat generation or excessive current flows, temperature fuses, thermistors, and valves (current cut-off valves) that cut off current flowing through the circuit by causing a rapid increase in internal battery pressure or temperature during abnormal heat generation. These protective components can be selected to avoid operation under normal high-current conditions, or they can be designed to prevent abnormal heat generation or thermal runaway even without the protective components.

[0172] The electrochemical device of this application includes any device in which an electrochemical reaction occurs, and specific examples include lithium metal secondary batteries or lithium-ion secondary batteries.

[0173] This application also provides an electronic device that includes the electrochemical device described in this application.

[0174] The application of the electrochemical device in this application is not particularly limited, and it can be used in any electronic device known in the prior art. In some embodiments, the electrochemical device of this application can be used in, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors, etc.

[0175] The following uses a lithium-ion battery as an example and combines specific embodiments to illustrate the preparation of a lithium-ion battery. Those skilled in the art will understand that the preparation method described in this application is only an example, and any other suitable preparation method is within the scope of this application.

[0176] Examples

[0177] I. Preparation of Lithium-ion Batteries

[0178] 1. Preparation of the negative electrode

[0179] Artificial graphite, styrene-butadiene rubber, and sodium carboxymethyl cellulose were mixed with deionized water in a mass ratio of 96%:2%:2% and stirred until homogeneous to obtain a negative electrode slurry. This negative electrode slurry was coated onto a 9μm copper foil, dried, cold-pressed, and then cut and welded with tabs to obtain the negative electrode.

[0180] 2. Preparation of the positive electrode

[0181] (1) Preparation of lithium cobalt oxide positive electrode active material containing aluminum, zirconium, and tungsten: Anhydrous ethanol and deionized water were mixed at a volume ratio of 7:3. 0.05 mol nickel nitrate hexahydrate, 0.02 mol cobalt nitrate hexahydrate, 0.03 mol manganese acetate tetrahydrate, a certain amount of aluminum sulfate, and zirconium sulfate were added, and the mixture was ultrasonically stirred until completely dissolved. The mixture was transferred to a 500 mL high-pressure reactor, and 0.6 mol ammonium bicarbonate was added. The mixture was heated to 120 °C and maintained for 8 hours. After cooling, the mixture was centrifuged, the precipitate was collected, washed three times with anhydrous ethanol, and vacuum dried at 60 °C for 8 hours to obtain a nickel cobalt manganese hydroxide precursor. Subsequently, lithium carbonate, tungsten oxide, and the prepared cobalt manganese hydroxide precursor were thoroughly mixed and ground. The mixture was calcined at 900 °C for 20 hours in a tube furnace, cooled, and ground again to obtain a lithium cobalt manganese oxide positive electrode active material containing aluminum, zirconium, and tungsten.

[0182] (2) Preparation of lithium cobalt oxide positive electrode active material containing aluminum, zirconium and tungsten: A certain amount of Co3O4 and LiOH powder were weighed and thoroughly mixed and ground in an agate mortar, and then calcined at 900℃ for 10 hours. A specific amount of aluminum sulfate, zirconium sulfate and sodium tungstate were added to the calcined mixture, and ethanol was used as a solvent. After ball milling for 10 hours, the mixture was calcined at 800℃ for 10 hours to obtain lithium cobalt oxide positive electrode active material containing aluminum, zirconium and tungsten.

[0183] The positive electrode active material, carbon nanotubes, and polyvinylidene fluoride were mixed with N-methylpyrrolidone (NMP) in a mass ratio of 97:1:2 and stirred until homogeneous to obtain a positive electrode slurry. This slurry was then coated onto a 12μm aluminum foil, dried, cold-pressed, and subsequently cut and welded with tabs to obtain the positive electrode.

[0184] 3. Preparation of electrolyte

[0185] In a dry argon atmosphere, EC, PC, PP, and DEC (weight ratio 1:1:1:1) were mixed, and LiPF6 was added and mixed thoroughly to form a basic electrolyte with a LiPF6 concentration of 12.5%. Electrolytes of different embodiments and comparative examples were obtained by adding different amounts of additives to the basic electrolyte.

[0186] The abbreviations and names of the components in the electrolyte are shown in the table below:

[0187] Material name Abbreviation Material name Abbreviation Vinyl carbonate EC Vinyl carbonate PC Diethyl carbonate DEC Fluoroethylene carbonate FEC Butanedinitrile SN Hexanedinitrile ADN Ethylene glycol bis(2-cyanoethyl) ether EDN 1,3,6-Hexanetrinitrile HTCN 1,2,3-Tris(2-cyanoethoxy)propane TCEP 1,3-Propanesultone PS Vinyl sulfate DTD Compound of formula I-1 Formula I-1 Compound of formula I-3 Formula I-4 Compound of formula I-4 Formula I-5 Compound of formula II-1 Formula II-1 Compound of formula III-1 Formula III-1 Lithium difluorophosphate LDP 1-Propylphosphonic acid cyclic anhydride T3P Vinyl ethylene carbonate VC Propyl propionate PP

[0188] 4. Preparation of the separating membrane

[0189] Polyethylene porous polymer film is used as the separator.

[0190] 5. Preparation of lithium-ion batteries

[0191] The obtained positive electrode, separator, and negative electrode are wound in sequence and placed in an outer packaging foil, leaving an injection port. Electrolyte is poured in through the injection port, the battery is sealed, and then processed through formation, capacity testing, and other procedures to produce a lithium-ion battery.

[0192] II. Testing Methods

[0193] 1. Test method for overcharge deformation rate of lithium-ion batteries

[0194] At 25°C, the lithium-ion battery was left to stand for 30 minutes, then charged at a constant current rate of 0.5C to 4.45V, followed by constant voltage charging at 4.45V to 0.05C, and left to stand for 60 minutes. The thickness 1 was measured. Then, it was charged at a constant current rate of 0.1C for 60 minutes, left to stand for 30 minutes, and this 0.1C charging and standing cycle was repeated 5 times to bring the lithium-ion battery to 150% state of charge (SOC). The thickness 2 was measured. The overcharge deformation rate of the lithium-ion battery was calculated using the following formula:

[0195] Overfill deformation rate = [(thickness 2 - thickness 1) / thickness 1] × 100%.

[0196] 2. Test method for high-temperature short-circuit deformation rate of lithium-ion batteries

[0197] At 25°C, the lithium-ion battery was left to stand for 30 minutes, then charged at a constant current rate of 0.5C to 4.7V, and then charged at a constant voltage rate of 4.7V to 0.05C. After standing for 60 minutes, the thickness T1 of the lithium-ion battery was measured. Then, the lithium-ion battery was short-circuited with 100mΩ for 10 seconds, and the thickness T2 of the lithium-ion battery was measured again. The high-temperature short-circuit deformation rate of the lithium-ion battery was calculated using the following formula:

[0198] Short-circuit deformation rate = [(T2-T1) / T1]×100%.

[0199] 3. Test method for thermal abuse thickness expansion rate of lithium-ion batteries

[0200] At 25°C, the lithium-ion battery was left to stand for 30 minutes, and its thickness H1 was measured. Then, the temperature was increased at a rate of 5°C / min until it reached 130°C, which was maintained for 30 minutes, and the thickness H2 was measured again. The thermal abuse thickness expansion rate of the lithium-ion battery was calculated using the following formula:

[0201] Thickness expansion rate = [(H2-H1) / H1]×100%.

[0202] III. Test Results

[0203] Table 1 illustrates the effects of positive electrode active material and electrolyte on the overcharge resistance and safety of lithium-ion batteries under high temperature and high pressure. In Comparative Examples 1-1 to 1-7 and Examples 1-1 to 1-4, the positive electrode active material was lithium nickel manganese cobalt oxide with / without doping elements. In Comparative Examples 1-8, the positive electrode active material was lithium cobalt oxide containing aluminum, zirconium, and tungsten.

[0204] Table 1

[0205]

[0206] As shown in Comparative Examples 1-1 to 1-3, when lithium nickel cobalt manganese oxide contains only one element from aluminum, zirconium, and tungsten, and the electrolyte does not contain dinitrile compounds, the overcharge deformation rate, short-circuit deformation rate, and thickness deformation rate of the lithium-ion battery are relatively high. As shown in Comparative Example 1-4, when the electrolyte contains dinitrile compounds but the positive electrode active material is undoped lithium nickel cobalt manganese oxide, the overcharge deformation rate, short-circuit deformation rate, and thickness deformation rate of the lithium-ion battery are relatively high. As shown in Comparative Examples 1-5 to 1-7, when the electrolyte contains dinitrile compounds but lithium nickel cobalt manganese oxide contains only two elements from aluminum, zirconium, and tungsten, the overcharge deformation rate, short-circuit deformation rate, and thickness deformation rate of the lithium-ion battery are relatively high. As shown in Comparative Example 1-8, when the electrolyte contains dinitrile compounds but lithium cobalt oxide containing aluminum, zirconium, and tungsten is used as the positive electrode active material, the overcharge deformation rate, short-circuit deformation rate, and thickness deformation rate of the lithium-ion battery are relatively high.

[0207] As shown in Examples 1-1 to 1-4, when lithium nickel cobalt manganese oxide contains aluminum, zirconium, and tungsten and the electrolyte contains dinitrile compounds, the overcharge deformation rate, short-circuit deformation rate, and thickness deformation rate of lithium-ion batteries can be significantly reduced.

[0208] Table 2 shows the effects of the aluminum, zirconium, and tungsten content in the positive electrode active material on the overcharge resistance and safety of lithium-ion batteries under high temperature and high pressure. The electrolytes used in the examples and comparative examples listed in Table 2 are the same as those in Examples 1-1.

[0209] Table 2

[0210]

[0211]

[0212] The results show that when the aluminum content (a%), zirconium content (b%), and tungsten content (c%) in the positive electrode active material meet at least one of the following conditions: 0.1≤a+b+c≤1; 1≤(b+c) / a≤5; and 1≤b / c≤3, the overcharge deformation rate, short-circuit deformation rate, and thickness deformation rate of lithium-ion batteries can be further reduced.

[0213] Table 3 illustrates the relationship between the tungsten content in the positive electrode active material and the content of dinitrile compounds in the electrolyte, and its impact on the overcharge resistance and safety of lithium-ion batteries under high temperature and high pressure. Except for the parameters listed in Table 3, Examples 3-1 to 3-11 are identical to those in Example 1-1.

[0214] Table 3

[0215]

[0216] The results show that when the tungsten content (c%) in the positive electrode active material and the dinitrile compound content (x%) in the electrolyte satisfy 10 ≤ x / c ≤ 100, the overcharge deformation rate, short-circuit deformation rate, and thickness deformation rate of lithium-ion batteries can be further reduced.

[0217] Table 4 shows the effects of dinitrile and trinitrile compounds in the electrolyte on the overcharge resistance and safety of lithium-ion batteries under high temperature and high pressure. The positive electrode active materials used in Examples 4-1 to 4-14 are the same as those in Example 1-1.

[0218] Table 4

[0219]

[0220] The results show that adding trinitrile compounds to the electrolyte containing dinitrile compounds can further reduce the overcharge deformation rate, short-circuit deformation rate, and thickness deformation rate of lithium-ion batteries.

[0221] Furthermore, when the content of dinitrile compound x% and the content of trinitrile compound y% in the electrolyte satisfy 1≤x+y≤15 and / or 1≤x / y≤5, the overcharge deformation rate, short-circuit deformation rate and thickness deformation rate of lithium-ion batteries can be further reduced.

[0222] Table 5 illustrates the relationship between the tungsten content in the positive electrode active material and the content of compounds with sulfur-oxygen double bonds in the electrolyte on the overcharge resistance and safety of lithium-ion batteries under high temperature and high pressure. Except for the parameters listed in Table 5, the settings in Examples 5-1 to 5-11 are the same as in Example 1-1.

[0223] Table 5

[0224]

[0225] The results show that when a compound with sulfur-oxygen double bonds is further added to the electrolyte containing dinitrile compounds, and the content of the dinitrile compound x% and the content of the compound with sulfur-oxygen double bonds z% satisfy 1≤z / c≤50, the overcharge deformation rate, short-circuit deformation rate and thickness deformation rate of lithium-ion batteries can be further reduced.

[0226] Table 6 illustrates the effect of further addition of additional compounds to the electrolyte on the overcharge resistance and safety of lithium-ion batteries under high temperature and high pressure. Except for the parameters listed in Table 6, the settings of Examples 6-1 to 6-10 are the same as those of Example 1-1.

[0227] Table 6

[0228]

[0229]

[0230] The results show that adding at least one of lithium difluorophosphate, compound III, fluoroethylene carbonate, vinylene carbonate, or 1-propyl cyclic anhydride to the electrolyte containing dinitrile compounds can further reduce the overcharge deformation rate, short-circuit deformation rate, and thickness deformation rate of lithium-ion batteries.

[0231] Throughout this specification, references 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 that embodiment or example. Therefore, descriptions appearing throughout this specification, such as "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in an example," "in a specific example," or "example," do not necessarily refer to the same embodiments or examples in this application. Furthermore, specific features, structures, materials, or characteristics described herein can be combined in any suitable manner in one or more embodiments or examples.

[0232] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. An electrochemical device comprising: A positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material, wherein: The positive electrode active material comprises lithium nickel cobalt manganese oxide doped with aluminum, zirconium, and tungsten. Based on the mass of the positive electrode active material, the aluminum content is a%, where a ranges from 0.05 to 1; based on the mass of the positive electrode active material, the zirconium content is b%, where b ranges from 0.05 to 1; based on the mass of the positive electrode active material, the tungsten content is c%, where c ranges from 0.05 to 1; and The electrolyte includes a dinitrile compound, and the content of the dinitrile compound is x% based on the mass of the electrolyte, where x ranges from 0.1 to 15.

2. The electrochemical device according to claim 1, wherein the contents of aluminum, zirconium and tungsten are a%, b% and c% respectively based on the mass of the positive electrode active material, and a, b and c satisfy: 0.1≤a+b+c≤1.

3. The electrochemical device according to claim 1, wherein the contents of aluminum, zirconium and tungsten are a%, b% and c% respectively based on the mass of the positive electrode active material, and a, b and c satisfy: 1≤(b+c) / a≤5.

4. The electrochemical device according to claim 1, wherein the contents of zirconium and tungsten are b% and c% respectively based on the mass of the positive electrode active material, and b and c satisfy: 1≤b / c≤3.

5. The electrochemical device according to claim 1, wherein: Based on the mass of the positive electrode active material, the tungsten content is c%. Based on the mass of the electrolyte, the content of the dinitrile compound is x%; and c and x satisfy: 10 ≤ x / c ≤ 100.

6. The electrochemical device according to claim 1, wherein the electrolyte further comprises a trinitrile compound.

7. The electrochemical device according to claim 6, wherein the content of the dinitrile compound is x% and the content of the trinitrile compound is y% based on the mass of the electrolyte, and x and y satisfy: 1≤x+y≤15.

8. The electrochemical device according to claim 7, wherein x and y satisfy: 1 ​​≤ x / y ≤ 5.

9. The electrochemical device according to claim 1, wherein: The electrolyte also includes a compound having a sulfur-oxygen double bond, and the content of the compound having a sulfur-oxygen double bond is z% based on the mass of the electrolyte; Based on the mass of the positive electrode active material, the tungsten content is c%; and z and c satisfy: 1≤z / c≤50.

10. The electrochemical device according to claim 9, wherein the compound having a sulfur-oxygen double bond comprises at least one of bicyclic sulfate, bicyclic sulfonyl lactone, vinyl sulfate, propylene sulfate, 1,3-propanesulfonyl lactone, 1,3-propenesulfonyl lactone, methylene disulfonate, or ethylene disulfonate.

11. The electrochemical device according to claim 10, wherein the bicyclic sulfate comprises a compound of formula I: ， in: W selected ; L are each independently selected from single bonds or methylene groups; m can be 1, 2, 3, or 4; n is 0, 1, or 2; and p can be 0, 1, 2, 3, 4, 5, or 6.

12. The electrochemical device according to claim 11, wherein the compound of formula I comprises at least one of the following: or 。 13. The electrochemical device according to claim 10, wherein the bicyclic sulfonyl lactone comprises a compound of formula II: ， A1, A2, A3 and A4 are each independently selected from substituted or unsubstituted C1-3 alkylene groups. When substituted, the substituents are selected from C1-5 alkyl, halogen or halo-C1-5 alkyl groups.

14. The electrochemical device according to claim 13, wherein the compound of formula II comprises at least one of the following: or 。 15. The electrochemical device according to any one of claims 1 to 14, wherein the electrochemical device satisfies at least one of the following: e) The electrolyte also includes a trinitrile compound, and the content of the trinitrile compound is y% based on the mass of the electrolyte, where y ranges from 0.1 to 8; f) The electrolyte also includes a compound having a sulfur-oxygen double bond, and the content of the compound having a sulfur-oxygen double bond is z% based on the mass of the electrolyte, where z ranges from 0.01 to 5.

16. The electrochemical device according to claim 15, wherein the electrochemical device satisfies at least one of the following: g) The value of a ranges from 0.1 to 0.5; h) The value of b ranges from 0.1 to 0.5; i) The value of c ranges from 0.1 to 0.5; j) The value of x ranges from 0.5 to 10; k) The value of y ranges from 0.5 to 5; l) The value of z ranges from 0.1 to 3.

17. The electrochemical device according to claim 1, wherein the electrolyte further comprises lithium difluorophosphate or at least one of formula III. ； Where R is a single bond or a C1-4 alkylene group.

18. The electrochemical device according to claim 1, wherein the electrolyte further comprises at least one of fluoroethylene carbonate, vinylene carbonate, or 1-propyl cyclic phosphate anhydride.

19. An electronic device comprising an electrochemical device according to any one of claims 1-18.

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