Electrochemical devices and electronic devices

Abstract

This application relates to an electrochemical device and an electronic device. Specifically, this application provides an electrochemical device comprising a positive electrode, a negative electrode, and an electrolyte. The negative electrode includes a negative electrode current collector and a negative electrode additive layer formed on the negative electrode current collector. The negative electrode additive layer includes a negative electrode active material, wherein the elongation at the yield point of the negative electrode additive layer satisfies a specific relationship with the D50 of the negative electrode active material, and the electrolyte includes a compound having a cyano group. The electrochemical device of this application has improved rate performance and safety performance.

Description

[0001] Information related to divisional application

[0002] This case is a divisional application. The parent application of this divisional application is the invention patent application filed on October 15, 2020, with application number 202011101196.5 and title "Electrochemical Device and Electronic Device". Technical Field

[0003] This application relates to the field of energy storage, specifically to an electrochemical device and an electronic device, particularly a lithium-ion battery. Background Technology

[0004] With technological advancements, electrochemical devices (such as lithium-ion batteries) have been widely applied in various aspects of daily life and production. Lithium-ion batteries offer advantages such as high energy density, long cycle life, and environmental friendliness. However, their application also faces numerous challenges, including driving range, cost, charging performance, safety, and hill-climbing performance. Improving the rate performance of lithium-ion batteries often leads to increased battery temperature, resulting in decreased safety.

[0005] In view of this, it is indeed necessary to provide an electrochemical and electronic device that combines high rate performance with good safety. Summary of the Invention

[0006] This application provides an electrochemical and electronic device with improved rate performance and safety performance to at least partially solve at least one problem existing in the relevant field.

[0007] This application provides an electrochemical device comprising a positive electrode, a negative electrode, and an electrolyte. The negative electrode comprises a negative electrode current collector and a negative electrode additive layer formed on the negative electrode current collector. The negative electrode additive layer comprises a negative electrode active material, wherein: the elongation at the yield point of the negative electrode additive layer is X%, and the median particle size of the negative electrode active material is Y μm, where X and Y satisfy: 0.1 ≤ X / Y ≤ 30; the electrolyte comprises a compound having a cyano group.

[0008] According to embodiments of this application, X is in the range of 10 to 30, and Y is in the range of 1 to 50.

[0009] According to an embodiment of this application, based on the weight of the electrolyte, the content of the cyano compound is Z%, where Z is in the range of 0.1 to 10.

[0010] According to an embodiment of this application, X and Z satisfy: 2≤X / Z≤100.

[0011] According to embodiments of this application, the negative electrode compound layer comprises rubber, wherein the rubber comprises at least one of styrene-butadiene rubber, isoprene rubber, butadiene rubber, fluororubber, acrylonitrile-butadiene rubber, and styrene-propylene rubber.

[0012] According to embodiments of this application, the rubber further comprises at least one of an acrylic acid functional group, a trichlorofluoroethylene functional group, or a hexafluoropropylene functional group.

[0013] According to embodiments of this application, the negative electrode active material has at least one of the following characteristics:

[0014] (i) includes at least one of the following: artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, amorphous carbon, silicon-containing materials, tin-containing materials, and alloy materials;

[0015] (ii) includes a metal, said metal including at least one of molybdenum, iron or copper, and the content of said metal is less than 0.05% based on the weight of said negative electrode mixture layer.

[0016] According to embodiments of this application, the cyano-containing compounds include succinate, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, tetramethylsuccinate, 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-dioxane- Heptanonitrile, 1,4-di(cyanoethoxy)butane, diethylene glycol di(2-cyanoethyl) ether, triethylene glycol di(2-cyanoethyl) ether, tetraethylene glycol di(2-cyanoethyl) ether, 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 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, 1,6-dicyano-2-methyl-3-hexene, 1,3,5-pentanetricarbonyl, 1,2,3-propanetricarbonyl, 1,3,6-hexanetricarbonyl, 1,2,6-hexanetricarbonyl, 1,2,3- At least one of the following: 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.

[0017] According to embodiments of this application, the cyano compound includes a dinitrile compound without ether bonds and a dinitrile compound containing ether bonds, wherein the content of the dinitrile compound without ether bonds is greater than the content of the dinitrile compound containing ether bonds.

[0018] According to embodiments of this application, the cyano-containing compound includes a dinitrile compound and a trinitrile compound, wherein the content of the dinitrile compound is greater than the content of the trinitrile compound.

[0019] According to embodiments of this application, the cyano compound includes a dinitrile compound and a trinitrile compound having an ether bond, wherein the content of the dinitrile compound is greater than the content of the trinitrile compound having an ether bond.

[0020] According to embodiments of this application, the electrolyte further comprises at least one of the following compounds:

[0021] a) Fluorinated ethylene carbonate;

[0022] b) Compounds containing sulfur-oxygen double bonds;

[0023] c) Lithium difluorophosphate; and

[0024] d) Compound of Formula 1:

[0025]

[0026] in:

[0027] R 1 R 2 R 3 R 4 R 5 and R 6 Each is independently hydrogen or C1-C 10 alkyl;

[0028] L1 and L2 are each independently -(CR 7 R 8 ) n -;

[0029] R 7 and R 8 Each is independently hydrogen or C1-C 10 Alkyl groups; and

[0030] n is 1, 2, or 3.

[0031] According to embodiments of this application, the compound of formula 1 includes at least one of the following compounds:

[0032]

[0033] According to embodiments of this application, the content of the compound of formula 1 is in the range of 0.01% to 5% based on the weight of the electrolyte.

[0034] According to an embodiment of this application, the content of fluoroethylene carbonate is b% based on the weight of the electrolyte, with b ranging from 0.1 to 10%.

[0035] According to an embodiment of this application, the relationship between Y and b satisfies: 4≤Y×b≤200.

[0036] In another aspect of this application, an electronic device is provided that includes the electrochemical device described in this application.

[0037] 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

[0038] The embodiments of this application will be described in detail below. These embodiments should not be construed as limiting the scope of this application.

[0039] Unless otherwise expressly stated, the terms used herein have the meanings indicated below.

[0040] 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".

[0041] 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.

[0042] As used herein, the term "halogenated" refers to the partial or complete substitution of hydrogen atoms in a group by halogen atoms (e.g., fluorine, chlorine, bromine, or iodine).

[0043] With the increasing use of electrochemical devices (such as lithium-ion batteries), higher performance requirements have been placed on them, including rate performance and safety. However, rate performance and safety are often difficult to achieve simultaneously. While techniques such as selecting active materials for the positive or negative electrode, electrolyte composition, and optimizing battery design can help improve the rate performance of lithium-ion batteries, lithium-ion batteries tend to generate a large amount of heat when discharging at high rates, which can adversely affect their safety.

[0044] To address the aforementioned issues, this application adjusts the relationship between the elongation at the yield point of the negative electrode mixture layer and the median particle size (D50) of the negative electrode active material, and combines this with an electrolyte containing compounds with cyano groups. This results in reduced internal resistance, enhanced adhesion, improved conductivity, and increased compaction density of the electrochemical device, thereby significantly improving its rate performance. Simultaneously, it reduces the thickness expansion rate of the electrochemical device under thermal abuse conditions, thus improving its safety performance.

[0045] In one embodiment, this application provides an electrochemical device comprising a positive electrode, a negative electrode, and an electrolyte as described below.

[0046] I. Negative electrode

[0047] The negative electrode includes a negative electrode current collector and a negative electrode mixture layer formed on one or both surfaces of the negative electrode current collector, the negative electrode mixture layer including a negative electrode active material.

[0048] A feature of the electrochemical device of this application is that the elongation X% of the yield point of the negative electrode mixture layer and the D50 Yμm of the negative electrode active material satisfy the following: 0.1 ≤ X / Y ≤ 30. In some embodiments, 0.5 ≤ X / Y ≤ 25. In some embodiments, 1 ≤ X / Y ≤ 20. In some embodiments, 3 ≤ X / Y ≤ 15. In some embodiments, X / Y is 0.1, 0.5, 1, 2, 5, 8, 10, 12, 15, 18, 20, 25, 30 or within a range consisting of any two of the above values. When the elongation X% of the yield point of the negative electrode mixture layer and the D50 Yμm of the negative electrode active material satisfy the above relationship, the rate performance and safety performance of the electrochemical device can be significantly improved.

[0049] When the negative electrode layer is stretched, if the tensile force exceeds the limit of elastic deformation, further stretching will cause the negative electrode layer to undergo plastic deformation. The boundary between elastic and plastic deformation of the negative electrode layer is called the "yield point". The elongation at the yield point of the negative electrode layer can be expressed by the following formula: (elongation of the negative electrode layer at the yield point - original length of the negative electrode layer) / original length of the negative electrode layer × 100%.

[0050] The elongation at the yield point of the negative electrode adhesive layer can be determined by the following method: A 50 μm thick polyethylene terephthalate (PET) film is adhered to one adhesive side of double-sided tape, and the negative electrode adhesive layer is adhered to the other adhesive side of the double-sided tape. The negative electrode adhesive layer and the PET film are peeled off from the negative electrode current collector together to obtain the test sample. A test sample measuring 140 mm in length and 15 mm in width is taken and fixed in the chuck (positioning fixture) of a tensile testing machine, so that the length of the stretchable portion of the negative electrode adhesive layer is 100 mm. At room temperature (20℃±5℃), the test sample is stretched in a direction substantially orthogonal to the thickness direction of the negative electrode adhesive layer (±10° to the thickness direction). Whenever the negative electrode layer elongates by 1 mm (the elongation rate is 1% for 1 mm, 2% for 2 mm, and so on), the stretching is paused, and the resistance of the negative electrode layer is measured three times using a resistance measuring device equipped with a four-probe 300mm sensor via a four-terminal method. The average value is taken. The above steps are repeated until the negative electrode layer breaks. An orthogonal coordinate system is plotted with the elongation rate of the negative electrode layer as the horizontal axis and the resistance rate as the vertical axis. The measurement point with the smaller elongation rate when the resistance difference between two adjacent measurement points exceeds 0.1Ω is recorded as the "yield point," and the elongation rate of the yield point of the negative electrode layer is recorded. When multiple yield points exist, the elongation rate of the yield point with the smallest corresponding elongation rate is taken as the elongation rate of the yield point of the negative electrode layer.

[0051] 1. Negative electrode mixture layer

[0052] The negative electrode additive layer can be one or more layers, and each layer in a multilayer negative electrode active material can contain the same or different negative electrode active materials. The negative electrode active material is any substance 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 onto the negative electrode during charging. In some embodiments, the elongation at the yield point of the negative electrode additive layer is in the range of 10% to 30%. In some embodiments, the elongation at the yield point of the negative electrode additive layer is in the range of 15% to 25%. The elongation at the yield point of the negative electrode additive layer is 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or within a range consisting of any two of the above values. When the elongation at the yield point of the negative electrode additive layer is within the above range, the rate performance and safety performance of the electrochemical device can be further improved.

[0053] In some embodiments, the median particle size (D50) of the negative electrode active material is in the range of 1 μm to 50 μm. In some embodiments, the median particle size (D50) of the negative electrode active material is in the range of 3 μm to 40 μm. In some embodiments, the median particle size (D50) of the negative electrode active material is in the range of 5 μm to 30 μm. In some embodiments, the median particle size (D50) of the negative electrode active material is in the range of 10 μm to 20 μm. In some embodiments, the median particle size of the negative electrode active material is 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or within a range consisting of any two of the above values. When the median particle size (D50) of the negative electrode active material is within the above ranges, the rate performance and safety performance of the electrochemical device can be further improved.

[0054] The median particle size (D50) of the negative electrode active material can be determined by the following method: the carbon material is dispersed in a 0.2% aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate and tested using a laser diffraction / scattering particle size analyzer (Horiba Seisakusho LA-700).

[0055] In some embodiments, the negative electrode binder layer comprises rubber. Rubber can effectively improve the interfacial stability of the negative electrode binder layer, thereby significantly improving the rate performance and safety performance of the electrochemical device.

[0056] In some embodiments, the rubber includes at least one of styrene-butadiene rubber, isoprene rubber, butadiene rubber, fluororubber, acrylonitrile-butadiene rubber, and styrene-propylene rubber.

[0057] In some embodiments, the rubber further comprises at least one of an acrylic functional group, a trichlorofluoroethylene functional group, or a hexafluoropropylene functional group.

[0058] In some embodiments, the rubber content is 10% or less based on the weight of the negative electrode mixture layer. In some embodiments, the rubber content is 8% or less based on the weight of the negative electrode mixture layer. In some embodiments, the rubber content is 5% or less based on the weight of the negative electrode mixture layer. In some embodiments, the rubber content is 3% or less based on the weight of the negative electrode mixture layer. In some embodiments, the rubber content is 2% or less based on the weight of the negative electrode mixture layer.

[0059] In some embodiments, the negative electrode active material has at least one of the following characteristics (i) or (ii):

[0060] (i) Types of negative electrode active materials

[0061] In some embodiments, the negative electrode active material includes at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, amorphous carbon, silicon-containing materials, tin-containing materials, and alloy materials.

[0062] In some embodiments, the shape of the negative electrode active material includes, but is not limited to, fibrous, spherical, granular, and scaly forms.

[0063] In some embodiments, the negative electrode active material includes carbon materials.

[0064] In some embodiments, the negative electrode active material has a content of less than 5m 2 The specific surface area is 1 / g. In some embodiments, the negative electrode active material has a specific surface area of ​​less than 3m². 2 The specific surface area is 1 / g. In some embodiments, the negative electrode active material has a specific surface area of ​​less than 1m². 2 The specific surface area is 0.1 m² / g. In some embodiments, the negative electrode active material has a specific surface area greater than 0.1 m² / g. 2 The specific surface area is 0.7 m² / g. In some embodiments, the negative electrode active material has a specific surface area of ​​less than 0.7 m² / g. 2 The specific surface area is 0.5 m² / g. In some embodiments, the negative electrode active material has a specific surface area of ​​less than 0.5 m² / g. 2 The specific surface area is / g. In some embodiments, the specific surface area of ​​the negative electrode active material is within the range of any two of the above values. When the specific surface area of ​​the negative electrode active material is within the above range, lithium deposition on the electrode surface can be suppressed, and gas generation caused by the reaction between the negative electrode and the electrolyte can be suppressed.

[0065] The specific surface area (BET) of the negative electrode active material can be determined by the following method: using a surface area meter (fully automatic surface area measuring device manufactured by Riken Okura), the sample is pre-dried at 350°C for 15 minutes under nitrogen flow. Then, a nitrogen-helium mixed gas with the relative pressure of nitrogen relative to atmospheric pressure accurately adjusted to 0.3 is used to determine the BET by the nitrogen adsorption single-point method using the gas flow method.

[0066] In some embodiments, based on the X-ray diffraction pattern obtained by the vibratory method, the interlayer distance of the lattice plane (002 plane) of the negative electrode active material is in the range of about 0.335 nm to about 0.360 nm, in the range of about 0.335 nm to about 0.350 nm, or in the range of about 0.335 nm to about 0.345 nm.

[0067] In some embodiments, based on the X-ray diffraction pattern obtained by the vibratory method, the crystallite size (Lc) of the negative electrode active material is greater than about 1.0 nm or greater than about 1.5 nm.

[0068] In some embodiments, the Raman R value of the negative electrode active material is greater than about 0.01, greater than about 0.03, or greater than about 0.1. In some embodiments, the Raman R value of the negative electrode active material is less than about 1.5, less than about 1.2, less than about 1.0, or less than about 0.5. In some embodiments, the Raman R value of the negative electrode active material is within the range of any two of the above values.

[0069] The negative electrode active material is at 1580 cm⁻¹ -1 There is no particular limitation on the Raman full width at half maximum (FWHM) in the vicinity. In some embodiments, the negative electrode active material is at 1580 cm⁻¹. -1 The width of the nearby Raman peak is greater than approximately 10 cm. -1 or larger than approximately 15cm -1 In some embodiments, the negative electrode active material is at 1580 cm⁻¹ -1 The width of the nearby Raman peak is less than approximately 100 cm. -1 Less than approximately 80cm -1 Less than approximately 60cm -1 or less than approximately 40cm -1 In some embodiments, the negative electrode active material is at 1580 cm⁻¹ -1 The Raman half-width in the vicinity is within the range of any two of the above values.

[0070] In some embodiments, the aspect ratio of the negative electrode active material is greater than about 1, greater than about 2, or greater than about 3. In some embodiments, the aspect ratio of the negative electrode active material is less than about 10, less than about 8, or less than about 5. In some embodiments, the aspect ratio of the negative electrode active material is within the range of any two of the above values. When the aspect ratio of the negative electrode active material is within the above range, a more uniform coating can be achieved.

[0071] (ii) Trace elements

[0072] In some embodiments, the negative electrode active material comprises a metal, including at least one of molybdenum, iron, or copper. These metal elements can react with some poorly conductive organic compounds in the negative electrode active material, thereby facilitating film formation on the surface of the negative electrode active material.

[0073] In some embodiments, the aforementioned metal elements are present in trace amounts in the negative electrode mixture layer to avoid the formation of non-conductive byproducts that adhere to the surface of the negative electrode. In some embodiments, the metal content is less than 0.05% based on the weight of the negative electrode mixture layer. In some embodiments, the metal content is less than 0.04% based on the weight of the negative electrode mixture layer. In some embodiments, the metal content is less than 0.03% based on the weight of the negative electrode mixture layer. In some embodiments, the metal content is less than 0.01% based on the weight of the negative electrode mixture layer. When the metal content in the negative electrode mixture layer is within the above ranges, the rate performance and safety performance of the electrochemical device can be further improved.

[0074] In some embodiments, the negative electrode mixture layer further comprises at least one of a silicon-containing material, a tin-containing material, and an alloy material. In some embodiments, the negative electrode mixture layer further comprises at least one of a silicon-containing material and a tin-containing material. In some embodiments, the negative electrode mixture layer further comprises one or more of a silicon-containing material, a silicon-carbon composite material, a silicon-oxygen material, an alloy material, and a lithium metal composite oxide material.

[0075] In some embodiments, the negative electrode mixture layer further comprises other types of negative electrode active materials, such as one or more materials comprising a metallic element and a metalloid element capable of forming an alloy with lithium. Examples of the metallic element and metalloid element in some embodiments include, but are not limited to, Mg, B, Al, Ga, In, Si, Ge, Sn, Pb, Bi, Cd, Ag, Zn, Hf, Zr, Y, Pd, and Pt. Examples of the metallic element and metalloid element in some embodiments include Si, Sn, or combinations thereof. Si and Sn have excellent lithium-ion intercalation / deintercalation capabilities, providing high energy density for lithium-ion batteries. In some embodiments, other types of negative electrode active materials may also include one or more of metal oxides and polymeric compounds. In some embodiments, the metal oxide includes, but is not limited to, iron oxide, ruthenium oxide, and molybdenum oxide. In some embodiments, the polymeric compound includes, but is not limited to, polyacetylene, polyaniline, and polypyrrole.

[0076] Negative conductive material

[0077] In some embodiments, the negative electrode mixture layer further comprises a negative electrode conductive material, which may include any conductive material as long as it does not cause a chemical change. Non-limiting examples of conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0078] Negative electrode adhesive

[0079] In some embodiments, the negative electrode binder layer further includes a negative electrode adhesive. The negative electrode adhesive can improve 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 adhesive, as long as it is a material stable to the electrolyte or the solvent used in electrode manufacturing.

[0080] Examples of negative electrode adhesives include, but are not limited to, resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, polyimide, cellulose, and nitrocellulose; rubber-like polymers such as styrene-butadiene rubber (SBR), isoprene rubber, polybutadiene rubber, fluororubber, acrylonitrile-butadiene rubber (NBR), and ethylene-propylene rubber; thermoplastic elastomers such as styrene-butadiene-styrene block copolymers or their hydrides; thermoplastic elastomers such as ethylene-propylene-diene terpolymers (EPDM), styrene-ethylene-butadiene-styrene copolymers, and styrene-isoprene-styrene block copolymers or their hydrides; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorinated polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; and polymer compositions with ion conductivity of alkali metal ions (e.g., lithium ions). The above-mentioned negative electrode adhesive can be used alone or in any combination.

[0081] In cases where the negative electrode binder layer contains a fluorinated polymer (e.g., polyvinylidene fluoride), in some embodiments, the content of the negative electrode binder is greater than about 1%, greater than about 2%, or greater than about 3% based on the weight of the negative electrode binder layer. In some embodiments, the content of the negative electrode binder is less than about 10%, less than about 8%, or less than about 5% based on the weight of the negative electrode binder layer. The content of the negative electrode binder is within the range of any two of the above values ​​based on the weight of the negative electrode binder layer.

[0082] solvent

[0083] There are no particular limitations on the type of solvent used to form the negative electrode slurry, as long as it is capable of dissolving or dispersing the negative electrode active material, the negative electrode binder, and, as needed, the thickener and conductive material. In some embodiments, the solvent used to form the negative electrode slurry can be either an aqueous solvent or an organic solvent. Examples of aqueous solvents include, but are not limited to, water and alcohols. Examples of organic solvents include, but are not limited to, N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N,N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, hexamethylphosphoramide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. The above solvents can be used alone or in any combination.

[0084] Thickener

[0085] Thickeners are typically used to adjust the viscosity of negative electrode slurries. 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 thickeners can be used alone or in any combination.

[0086] In some embodiments, the content of the thickener is greater than about 0.1%, greater than about 0.5%, or greater than about 0.6% based on the weight of the negative electrode paste layer. In some embodiments, the content of the thickener is less than about 5%, less than about 3%, or less than about 2% based on the weight of the negative electrode paste layer. When the content of the thickener is within the above ranges, the capacity reduction and resistance increase of the electrochemical device can be suppressed, while ensuring that the negative electrode slurry has good coatability.

[0087] surface coating

[0088] In some embodiments, the surface of the negative electrode mixture layer may be coated with a substance different from its composition. Examples of substances coated on the surface of the negative electrode mixture layer 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; and carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate.

[0089] Content of negative electrode active material

[0090] In some embodiments, the content of the negative electrode active material is greater than about 80%, greater than about 82%, or greater than about 84% based on the weight of the negative electrode mixture layer. In some embodiments, the content of the negative electrode active material is less than about 99% or less than about 98% based on the weight of the negative electrode mixture layer. In some embodiments, the content of the negative electrode active material is within the range of any two of the above arrays based on the weight of the negative electrode mixture layer.

[0091] Density of negative electrode active material

[0092] In some embodiments, the density of the negative electrode active material in the negative electrode mixture layer is greater than about 1 g / cm³. 3 Greater than approximately 1.2 g / cm³ 3 Or greater than approximately 1.3 g / cm³ 3 In some embodiments, the density of the negative electrode active material in the negative electrode mixture layer is less than about 2.2 g / cm³. 3 Less than approximately 2.1 g / cm³ 3 Less than approximately 2.0 g / cm³ 3 Or less than approximately 1.9 g / cm³ 3In some embodiments, the density of the negative electrode active material in the negative electrode mixture layer is within the range of any two of the above values.

[0093] When the density of the negative electrode active material is within the above range, it can prevent the destruction of the negative electrode active material particles, suppress the initial irreversible capacity increase of the electrochemical device or the deterioration of the high current density charge and discharge characteristics caused by the reduced permeability of the electrolyte near the interface between the negative electrode current collector and the negative electrode active material, and also suppress the capacity reduction and resistance increase of the electrochemical device.

[0094] 2. Negative electrode current collector

[0095] 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.

[0096] 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.

[0097] In some embodiments, the thickness of the negative electrode current collector is greater than about 1 μm or greater than about 5 μm. In some embodiments, the thickness of the negative electrode current collector is less than about 100 μm or less than about 50 μm. In some embodiments, the thickness of the negative electrode current collector is within the range of any two of the above values.

[0098] The thickness ratio of the negative electrode flux layer to the negative electrode current collector refers to the thickness of the single-sided negative electrode flux layer divided by the thickness of the negative electrode current collector, and its value is not particularly limited. In some embodiments, the thickness ratio is 50 or less. In some embodiments, the thickness ratio is 30 or less. In some embodiments, the thickness ratio is 20 or less. In some embodiments, the thickness ratio is 10 or less. In some embodiments, the thickness ratio is 1 or more. In some embodiments, the thickness ratio is within the range of any two of the above values. When the thickness ratio is within the above range, the capacity of the electrochemical device can be ensured, while the heat release of the negative electrode current collector during high current density charging and discharging can be suppressed.

[0099] II. Electrolyte

[0100] The electrolyte used in the electrochemical device of this application includes an electrolyte and a solvent for dissolving the electrolyte. In some embodiments, the electrolyte used in the electrochemical device of this application further includes additives.

[0101] Another feature of the electrochemical device of this application is that the electrolyte includes a compound having a cyano group.

[0102] In some embodiments, the cyano-containing compounds include butadionitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, tetramethylbutadionitrile, 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-heptane. Nitriles, 1,4-di(cyanoethoxy)butane, diethylene glycol di(2-cyanoethyl) ether, triethylene glycol di(2-cyanoethyl) ether, tetraethylene glycol di(2-cyanoethyl) ether, 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, 1,6-dicyano-2-methyl-3-hexene, 1,3,5-pentanetricarbonyl, 1,2,3-propanetricarbonyl, 1,3,6-hexanetricarbonyl, 1,2,6-hexanetricarbonyl, 1,2,3-trimethylaniline At least one of (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.

[0103] In some embodiments, the cyano compound includes a dinitrile compound without ether bonds and a dinitrile compound containing ether bonds, wherein the content of the dinitrile compound without ether bonds is greater than the content of the dinitrile compound containing ether bonds.

[0104] In some embodiments, the cyano compound includes a dinitrile compound and a trinitrile compound, wherein the content of the dinitrile compound is greater than the content of the trinitrile compound.

[0105] In some embodiments, the cyano compound includes a dinitrile compound and a trinitrile compound having an ether bond, wherein the content of the dinitrile compound is greater than the content of the trinitrile compound having an ether bond.

[0106] In some embodiments, the content of the cyano-containing compound is Z% based on the weight of the electrolyte, where Z is in the range of 0.1 to 10. In some embodiments, Z is in the range of 0.5 to 8. In some embodiments, Z is in the range of 1 to 5. In some embodiments, Z is 0.1, 0.5, 1, 2, 5, 8, 10, or within any two of the above values. When the content of the cyano-containing compound in the electrolyte is within the above ranges, the rate performance and safety performance of the electrochemical device can be further improved.

[0107] In some embodiments, the content Z% of cyano-containing compounds in the electrolyte and the elongation at the yield point of the negative electrode binder layer X% satisfy the following conditions: 2 ≤ X / Z ≤ 100. In some embodiments, 5 ≤ X / Z ≤ 80. In some embodiments, 10 ≤ X / Z ≤ 50. In some embodiments, 20 ≤ X / Z ≤ 30. In some embodiments, X / Z is 2, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or within any two of the above values. When the content Z% of cyano-containing compounds in the electrolyte and the elongation at the yield point of the negative electrode binder layer X% satisfy the above relationship, the rate performance and safety performance of the electrochemical device can be further improved.

[0108] In some embodiments, the electrolyte further comprises at least one of the following compounds:

[0109] a) Fluorinated ethylene carbonate;

[0110] b) Compounds containing sulfur-oxygen double bonds;

[0111] c) Lithium difluorophosphate;

[0112] d) Compound of Formula 1:

[0113]

[0114] in:

[0115] R 1 R 2 R 3 R 4 R 5 and R 6 Each is independently hydrogen or C1-C 10 alkyl;

[0116] L1 and L2 are each independently -(CR 7 R 8 ) n -;

[0117] R 7 and R 8 Each is independently hydrogen or C1-C10 Alkyl groups; and

[0118] n is 1, 2, or 3.

[0119] a) Fluorinated vinyl carbonate

[0120] During charging / discharging in an electrochemical device, fluoroethylene carbonate can interact with compounds containing cyano groups to form a stable protective film on the surface of the negative electrode, thereby inhibiting the decomposition reaction of the electrolyte.

[0121] In some embodiments, the fluorocarbonate has the formula C=O(OR) x (OR) y ), where R x and R y Each is selected from alkyl or haloalkyl groups having 1-6 carbon atoms, wherein R x and R y At least one of them is selected from fluoroalkyl groups having 1-6 carbon atoms, and R x and R y Optionally, it can be linked with the atoms it is attached to to form a 5- to 7-membered ring.

[0122] In some embodiments, examples of the fluoroethylene carbonate may include, but are not limited to, one or more of the following: fluoroethylene carbonate, cis-4,4-difluoroethylene carbonate, trans-4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, etc.

[0123] In some embodiments, the content of fluoroethylene carbonate is b% based on the weight of the electrolyte, with b ranging from 0.1 to 10. In some embodiments, b ranges from 0.5 to 8. In some embodiments, b ranges from 1 to 5. In some embodiments, b ranges from 2 to 4. In some embodiments, b is 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or within any two of the above values. When the content of fluoroethylene carbonate in the electrolyte is within the above ranges, the rate performance and safety performance of the electrochemical device can be further improved.

[0124] In some embodiments, the content b% of fluoroethylene carbonate in the electrolyte and the median particle size Yμm of the negative electrode active material satisfy the following: 4 ≤ Y×b ≤ 200. In some embodiments, 5 ≤ Y×b ≤ 150. In some embodiments, 10 ≤ Y×b ≤ 100. In some embodiments, 20 ≤ Y×b ≤ 50. In some embodiments, Y×b is 4, 5, 10, 20, 50, 80, 100, 120, 150, 180, 200, or within any two of the above values. When the content b% of fluoroethylene carbonate in the electrolyte and the median particle size Yμm of the negative electrode active material satisfy the above relationship, the rate performance and safety performance of the electrochemical device can be further improved.

[0125] b) Compounds containing sulfur-oxygen double bonds

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] In some embodiments, the compound containing a sulfur-oxygen double bond includes compounds of formula 2:

[0134]

[0135] in:

[0136] W selected

[0137] L are each independently selected from single bonds or methylene groups;

[0138] m can be 1, 2, 3, or 4;

[0139] n is 0, 1, or 2; and

[0140] p can be 0, 1, 2, 3, 4, 5, or 6.

[0141] In some embodiments, the compound of formula 2 includes at least one of the following:

[0142]

[0143]

[0144] In some embodiments, the content of the sulfur-oxygen double bond-containing compound is in the range of 0.01% to 10% based on the weight of the electrolyte. In some embodiments, the content of the sulfur-oxygen double bond-containing compound is in the range of 0.05% to 8% based on the weight of the electrolyte. In some embodiments, the content of the sulfur-oxygen double bond-containing compound is in the range of 0.1% to 5% based on the weight of the electrolyte. In some embodiments, the content of the sulfur-oxygen double bond-containing compound is in the range of 0.5% to 3% based on the weight of the electrolyte. In some embodiments, the content of the sulfur-oxygen double bond-containing compound is in the range of 1% to 2% based on the weight of the electrolyte. In some embodiments, the content of the sulfur-oxygen double bond-containing compound is 0.01%, 0.05%, 0.1%, 0.5%, 0.8%, 1%, 2%, 5%, 8%, 10% or within a range consisting of any two of the above values, based on the weight of the electrolyte.

[0145] c) Lithium difluorophosphate (LiPO2F2)

[0146] In some embodiments, the lithium difluorophosphate content is 0.01% to 1.5% based on the weight of the electrolyte. In some embodiments, the lithium difluorophosphate content is 0.05% to 1.2% based on the weight of the electrolyte. In some embodiments, the lithium difluorophosphate content is 0.1% to 1.0% based on the weight of the electrolyte. In some embodiments, the lithium difluorophosphate content is 0.5% to 0.8% based on the weight of the electrolyte. In some embodiments, the lithium difluorophosphate content is 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.8%, 1%, 1.5%, or within a range consisting of any two of the above values, based on the weight of the electrolyte.

[0147] d) Compound of Formula 1

[0148] In some embodiments, the compound of formula 1 includes at least one of the following compounds:

[0149]

[0150] In some embodiments, the content of the compound of Formula 1 is in the range of 0.01% to 5% based on the weight of the electrolyte. In some embodiments, the content of the compound of Formula 1 is in the range of 0.05% to 4% based on the weight of the electrolyte. In some embodiments, the content of the compound of Formula 1 is in the range of 0.1% to 3% based on the weight of the electrolyte. In some embodiments, the content of the compound of Formula 1 is in the range of 0.5% to 2% based on the weight of the electrolyte. In some embodiments, the content of the compound of Formula 1 is in the range of 1% to 1.5% based on the weight of the electrolyte. In some embodiments, the content of the compound of Formula 1 is 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or within any two of the above values, based on the weight of the electrolyte. When the content of the compound of Formula 1 in the electrolyte is within the above ranges, the rate performance and safety performance of the electrochemical device can be further improved.

[0151] solvent

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] additive

[0165] In some embodiments, examples of the additive may include, but are not limited to, one or more of the following: fluorocarbonates, ethylene carbonates containing carbon-carbon double bonds, compounds containing sulfur-oxygen double bonds, and acid anhydrides.

[0166] In some embodiments, the content of the additive is 0.01% to 15%, 0.1% to 10%, or 1% to 5% based on the weight of the electrolyte.

[0167] According to embodiments of this application, based on the weight of the electrolyte, the content of the propionate ester is 1.5 to 30 times, 1.5 to 20 times, 2 to 20 times, or 5 to 20 times that of the additive.

[0168] In some embodiments, the additive comprises one or more ethylene carbonates containing carbon-carbon double bonds. Examples of ethylene carbonates containing carbon-carbon double bonds may include, but are not limited to, one or more of the following: vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 1,2-dimethyl vinylene carbonate, 1,2-diethyl vinylene carbonate, fluoroethyleneene carbonate, trifluoromethyl vinylene carbonate; vinylene carbonate, 1-methyl-2-vinylene carbonate, 1-ethyl-2-vinylene carbonate, 1-n-propyl-2-vinylene carbonate, 1-methyl-2-vinylene carbonate, 1,1-divinylene carbonate, 1,2-divinylene carbonate, 1,1-dimethyl-2-methyleneene carbonate, and 1,1-diethyl-2-methyleneene carbonate, etc. In some embodiments, the ethylene carbonate containing carbon-carbon double bonds includes vinylene carbonate, which is readily available and can achieve superior effects.

[0169] In some embodiments, the additive is a combination of a fluorocarbonate and a ethylene carbonate containing a carbon-carbon double bond. In some embodiments, the additive is a combination of a fluorocarbonate and a compound containing a sulfur-oxygen double bond. In some embodiments, the additive is a combination of a fluorocarbonate and a compound having 2-4 cyano groups. In some embodiments, the additive is a combination of a fluorocarbonate and a cyclic carboxylic acid ester. In some embodiments, the additive is a combination of a fluorocarbonate and a cyclic phosphoric anhydride. In some embodiments, the additive is a combination of a fluorocarbonate and a carboxylic anhydride. In some embodiments, the additive is a combination of a fluorocarbonate and a sulfonic acid anhydride. In some embodiments, the additive is a combination of a fluorocarbonate and a carboxylic acid sulfonic anhydride.

[0170] electrolytes

[0171] There are no particular restrictions on the electrolyte; 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 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.

[0172] 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.

[0173] 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.

[0174] 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.

[0175] 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.

[0176] 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.

[0177] In addition to the solvents, additives, and electrolyte salts mentioned above, the electrolyte may contain additional additives such as negative electrode film-forming agents, positive electrode protectants, and overcharge protection agents, as needed. As additives, those commonly used in non-aqueous electrolyte secondary batteries can be used, examples of which include, but are not limited to, vinylene carbonate, succinic anhydride, biphenyl, cyclohexylbenzene, 2,4-difluoroanisole, propane sulpholactone, and propene sulpholactone. These additives can be used alone or in any combination. Furthermore, the content of these additives in the electrolyte is not particularly limited and can be appropriately set according to the type of additive, etc. In some embodiments, based on the weight of the electrolyte, the content of the additive is less than 5%, in the range of 0.01% to 5%, or in the range of 0.2% to 5%.

[0178] III. Positive electrode

[0179] The positive electrode includes a positive current collector and a layer of positive active material disposed on one or both surfaces of the positive current collector.

[0180] 1. Positive electrode active material layer

[0181] The positive electrode active material layer contains positive electrode active material, and the positive electrode active material layer can be one or more layers. Each layer in a multilayer positive electrode active material layer can contain the same or different positive electrode active materials. The positive electrode active material is any substance capable of reversibly inserting and deintercalating metal ions such as lithium ions.

[0182] There are no particular limitations on the type of positive electrode active material, as long as it can electrochemically adsorb and release metal ions (e.g., lithium ions). In some embodiments, the positive electrode active material is a substance containing lithium and at least one transition metal. Examples of positive electrode active materials may include, but are not limited to, lithium transition metal composite oxides and lithium transition metal phosphate compounds.

[0183] In some embodiments, the transition metal in the lithium transition metal composite oxide includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. In some embodiments, the lithium transition metal composite oxide includes lithium cobalt composite oxides such as LiCoO2, lithium nickel composite oxides such as LiNiO2, lithium manganese composite oxides such as LiMnO2, LiMn2O4, and Li2MnO4, and LiNi... 1 / 3 Mn 1 / 3 Co 1 / 3 O2, LiNi 0.5 Mn 0.3 Co 0.2 Lithium-nickel-manganese-cobalt composite oxides, such as O2, in which a portion of the transition metal atoms that form the bulk of these lithium transition metal composite oxides are replaced by other elements such as Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, and W. Examples of lithium transition metal composite oxides include, but are not limited to, LiNi. 0.5 Mn 0.5 O2, LiNi 0.85 Co 0.10 Al 0.05 O2, LiNi 0.33 Co 0.33 Mn 0.33 O2, LiNi 0.45 Co 0.10 Al 0.45 O2, LiMn 1.8 Al 0.2 O4 and LiMn 1.5 Ni 0.5 O4, etc. Examples of combinations of lithium transition metal composite oxides include, but are not limited to, combinations of LiCoO2 and LiMn2O4, wherein a portion of the Mn in LiMn2O4 can be replaced by a transition metal (e.g., LiNi). 0.33 Co 0.33 Mn0.33 In LiCoO2, some of the Co can be replaced by transition metals.

[0184] In some embodiments, the transition metal in the lithium transition metal phosphate compound includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. In some embodiments, the lithium transition metal phosphate compound includes iron phosphates such as LiFePO4, Li3Fe2(PO4)3, and LiFeP2O7, and cobalt phosphates such as LiCoPO4, wherein a portion of the transition metal atoms that constitute the main body of these lithium transition metal phosphate compounds are replaced by other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc.

[0185] In some embodiments, the positive electrode active material includes lithium phosphate, which can improve the continuous charging characteristics of the electrochemical device. The use of lithium phosphate is not limited. In some embodiments, the positive electrode active material and lithium phosphate are used in combination. In some embodiments, the content of lithium phosphate relative to the weight of the positive electrode active material and lithium phosphate is greater than 0.1%, greater than 0.3%, or greater than 0.5%. In some embodiments, the content of lithium phosphate relative to the weight of the positive electrode active material and lithium phosphate is less than 10%, less than 8%, or less than 5%. In some embodiments, the content of lithium phosphate is within the range of any two of the above values.

[0186] surface coating

[0187] The surface of the aforementioned positive electrode active material may be coated with a substance of a different composition. Examples of such surface-coated 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.

[0188] These surface-adhesive substances can be attached to the surface of the positive electrode active material by methods such as: dissolving or suspending the surface-adhesive substance in a solvent and adding it into the positive electrode active material followed by drying; dissolving or suspending the surface-adhesive substance precursor in a solvent, adding it into the positive electrode active material, and then reacting it by heating or the like; and adding it to the positive electrode active material precursor while simultaneously calcining it, etc. In the case of carbon attachment, a method of mechanically attaching carbon materials (e.g., activated carbon) can also be used.

[0189] In some embodiments, the content of surface-adhered substances, based on the weight of the positive electrode active material layer, is greater than 0.1 ppm, greater than 1 ppm, or greater than 10 ppm. In some embodiments, the content of surface-adhered substances, based on the weight of the positive electrode active material layer, is less than 10%, less than 8%, or less than 5%. In some embodiments, the content of surface-adhered substances, based on the weight of the positive electrode active material layer, is within the range of any two of the above values.

[0190] 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, thus sometimes increasing the resistance.

[0191] In this application, a positive electrode active material on which a substance with a different composition is attached to the surface of the positive electrode active material is also referred to as a "positive electrode active material".

[0192] shape

[0193] 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.

[0194] Tap density

[0195] In some embodiments, the tap density of the positive electrode active material is greater than 0.5 g / cm³. 3 Greater than 0.8 g / cm 3 or greater than 1.0 g / cm 3 When the tap density of the positive electrode active material is within the above-mentioned range, the amount of dispersion medium required for the formation of the positive electrode active material layer, as well as the required amounts of conductive material and positive electrode binder, can be suppressed, thereby ensuring the filling rate of the positive electrode active material and the capacity of the electrochemical device. A high-density positive electrode active material layer can be formed by using composite oxide powder with high tap density. Generally, a higher tap density is preferred, with no particular upper limit. In some embodiments, the tap density of the positive electrode active material is less than 4.0 g / cm³. 3 Less than 3.7 g / cm 3 or less than 3.5g / cm 3 When the tap density of the positive electrode active material has the upper limit mentioned above, the reduction in load characteristics can be suppressed.

[0196] The tap density of the positive electrode active material can be calculated as follows: Place 5g to 10g of positive electrode active material powder into a 10mL glass graduated cylinder and vibrate it 200 times with a stroke of 20mm to obtain the powder filling density (tap density).

[0197] Median particle size (D50)

[0198] When the positive electrode active material particles are primary particles, the median particle size (D50) refers to the primary particle size. When the primary particles of the positive electrode active material aggregate to form secondary particles, the median particle size (D50) refers to the secondary particle size.

[0199] In some embodiments, the median particle size (D50) of the positive electrode active material particles is greater than 0.3 μm, greater than 0.5 μm, greater than 0.8 μm, or greater than 1.0 μm. In some embodiments, the median particle size (D50) of the positive electrode active material particles is less than 30 μm, less than 27 μm, less than 25 μm, or less than 22 μm. In some embodiments, the median particle size (D50) of the positive electrode active material particles is within the range of any two of the above values. When the median particle size (D50) of the positive electrode active material particles is within the above 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. On the other hand, during the preparation process of the positive electrode of the electrochemical device (i.e., when the positive electrode active material, conductive material, and binder are slurried with a solvent and coated in a thin film), problems such as streaking can be prevented. Here, by mixing two or more positive electrode active materials with different median particle sizes, the filling properties during positive electrode preparation can be further improved.

[0200] The median particle size (D50) of the positive electrode active material particles can be determined using a laser diffraction / scattering particle size distribution measuring device: using a HORIBA LA-920 as the particle size distributor, a 0.1% sodium hexametaphosphate aqueous solution is used as the dispersion medium for the measurement. After ultrasonic dispersion for 5 minutes, the refractive index is set to 1.24 for measurement.

[0201] Average primary particle size

[0202] In cases where primary particles of the positive electrode active material agglomerate to form secondary particles, in some embodiments, the average primary particle size of the positive electrode active material is greater than 0.05 μm, greater than 0.1 μm, or greater than 0.5 μm. In some embodiments, the average primary particle size of the positive electrode active material is less than 5 μm, less than 4 μm, less than 3 μm, or less than 2 μm. In some embodiments, the average primary particle size of the positive electrode active material is within the range of any two of the above values. When the average primary particle size of the positive electrode active material is within the above range, powder filling capacity and specific surface area can be ensured, battery performance degradation can be suppressed, and appropriate crystallinity can be obtained, thereby ensuring the reversibility of charge and discharge of the electrochemical device.

[0203] The average primary particle size of the positive electrode active material can be obtained by observing images obtained by scanning electron microscopy (SEM): in an SEM image at a magnification of 10,000, for any 50 primary particles, find the longest value of the slice obtained by the left and right boundary lines of the primary particles relative to the horizontal straight line, and calculate its average value, thereby obtaining the average primary particle size.

[0204] Specific surface area (BET)

[0205] In some embodiments, the specific surface area (BET) of the positive electrode active material is greater than 0.1 m². 2 / g, greater than 0.2m 2 / g or greater than 0.3m 2 / g. In some embodiments, the specific surface area (BET) of the positive electrode active material is less than 50 m² / g. 2 / g, less than 40m 2 / g or less than 30m 2 / g. In some embodiments, the specific surface area (BET) of the positive electrode active material is within the range of any two of the above values. When the specific surface area (BET) of the positive electrode active material is within the above range, the performance of the electrochemical device can be ensured, while the positive electrode active material can have good coatability.

[0206] The specific surface area (BET) of the positive electrode active material can be measured by the following method: using a surface area meter (e.g., a fully automatic surface area measuring device manufactured by Riken Okura), the sample is pre-dried at 150°C for 30 minutes under nitrogen flow, and then a nitrogen-helium mixed gas with the relative pressure of nitrogen relative to atmospheric pressure accurately adjusted to 0.3 is used to measure the BET by the nitrogen adsorption single-point method using the gas flow method.

[0207] Positive conductive material

[0208] 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.

[0209] In some embodiments, the content of the positive electrode conductive material is greater than 0.01%, greater than 0.1%, or greater than 1%, based on the weight of the positive electrode active material layer. In some embodiments, the content of the positive electrode conductive material is less than 10%, less than 8%, or less than 5%, based on the weight of the positive electrode active material layer. When the content of the positive electrode conductive material is within the above ranges, sufficient conductivity and capacity of the electrochemical device can be ensured.

[0210] Positive electrode adhesive

[0211] 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.

[0212] In some embodiments, the content of the positive electrode binder is greater than 0.1%, greater than 1%, or greater than 1.5% based on the weight of the positive electrode active material layer. In some embodiments, the content of the positive electrode binder is less than 10%, less than 8%, less than 4%, or less than 3% based on the weight of the positive electrode active material layer. When the content of the positive electrode binder is within the above ranges, the positive electrode can have good conductivity and sufficient mechanical strength, and the capacity of the electrochemical device can be guaranteed.

[0213] solvent

[0214] 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.

[0215] Thickener

[0216] 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.

[0217] In some embodiments, the thickener content is greater than 0.1%, greater than 0.2%, or greater than 0.3% based on the weight of the positive electrode active material layer. In some embodiments, the thickener content is less than 5%, less than 3%, or less than 2% based on the weight of the positive electrode active material layer. In some embodiments, the thickener content is within the range of any two of the above values ​​based on the weight of the positive electrode active material layer. When the thickener content is within the above range, the positive electrode slurry can have good coatability, while suppressing the capacity reduction and resistance increase of the electrochemical device.

[0218] Content of positive electrode active material

[0219] In some embodiments, the content of the positive electrode active material is greater than 80%, greater than 82%, or greater than 84% based on the weight of the positive electrode active material layer. In some embodiments, the content of the positive electrode active material is less than 99% or less than 98% based on the weight of the positive electrode active material layer. In some embodiments, the content of the positive electrode active material is within the range of any two of the above arrays based on the weight of the positive electrode active material layer. When the content of the positive electrode active material is within the above ranges, the capacitance of the positive electrode active material in the positive electrode active material layer can be ensured, while the strength of the positive electrode can be maintained.

[0220] Density of the positive electrode active material layer

[0221] For the positive electrode active material layer obtained by coating and drying, in order to increase the filling density of the positive electrode active material, it can be compacted by a manual press or roller press. In some embodiments, the density of the positive electrode active material layer is greater than 1.5 g / cm³. 3 Greater than 2g / cm 3 or greater than 2.2 g / cm 3 In some embodiments, the density of the positive electrode active material layer is less than 5 g / cm³. 3 Less than 4.5 g / cm 3 or less than 4g / cm 3 In some embodiments, the density of the positive electrode active material layer is within the range of any two of the above values. When the density of the positive electrode active material layer is within the above range, the electrochemical device can have good charge and discharge characteristics, while suppressing the increase in resistance.

[0222] Thickness of the positive electrode active material layer

[0223] The thickness of the positive electrode active material layer refers to the thickness of the positive electrode active material layer on any side of the positive electrode current collector. In some embodiments, the thickness of the positive electrode active material layer is greater than 10 μm or greater than 20 μm. In some embodiments, the thickness of the positive electrode active material layer is less than 500 μm or less than 450 μm.

[0224] Method for manufacturing positive electrode active materials

[0225] Positive electrode active materials can be manufactured using methods commonly used in the manufacture of inorganic compounds. To produce spherical or ellipsoidal positive electrode active materials, the following method can be used: The transition metal raw material is dissolved or pulverized and dispersed in a solvent such as water, while stirring and adjusting the pH to create a spherical precursor, which is then recovered. After drying as needed, a Li source such as LiOH, Li₂CO₃, or LiNO₃ is added, and the mixture is calcined at high temperature to obtain the positive electrode active material.

[0226] 2. Positive current collector

[0227] 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.

[0228] There are no particular limitations on the form of the positive electrode current collector. When the positive 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 foil, metal mesh, stamped metal, foamed metal, etc. When the positive electrode current collector is a carbon material, its form may include, but is not limited to, carbon plate, carbon film, carbon cylinder, etc. In some embodiments, the positive electrode current collector is a metal foil. In some embodiments, the metal foil is a mesh. There are no particular limitations on the thickness of the metal foil. In some embodiments, the thickness of the metal foil is greater than 1 μm, greater than 3 μm, or greater than 5 μm. In some embodiments, the thickness of the metal foil is less than 1 mm, less than 100 μm, or less than 50 μm. In some embodiments, the thickness of the metal foil is within the range of any two of the above values.

[0229] 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.

[0230] The thickness ratio of the positive electrode active material layer to the positive electrode current collector refers to the thickness of the positive electrode active material layer on one side divided by the thickness of the positive electrode current collector, and its value is not particularly limited. In some embodiments, the thickness ratio is less than 50, less than 30, or less than 20. In some embodiments, the thickness ratio is greater than 0.5, greater than 0.8, or greater than 1. In some embodiments, the thickness ratio is within the range of any two of the above values. When the thickness ratio is within the above range, the heat release of the positive electrode current collector during high current density charging and discharging can be suppressed, and the capacity of the electrochemical device can be ensured.

[0231] 3. Method for manufacturing the positive electrode

[0232] 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.

[0233] IV. Separating membrane

[0234] 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.

[0235] 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.

[0236] 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.

[0237] 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.

[0238] 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.

[0239] 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.

[0240] 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 45%, or less than 40%. 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 rate capability.

[0241] 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, short circuits are prevented while membrane resistance is suppressed, giving the electrochemical device good rate performance.

[0242] V. Electrochemical Device Components

[0243] Electrochemical device components include electrode arrays, current collectors, housings, and protective elements.

[0244] Electrode group

[0245] 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.

[0246] collector structure

[0247] 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.

[0248] outer casing

[0249] 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.

[0250] 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.

[0251] Protective components

[0252] 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.

[0253] VI. Application

[0254] The electrochemical device of this application includes any device in which an electrochemical reaction occurs, and specific examples include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries or lithium-ion secondary batteries.

[0255] This application also provides an electronic device that includes an electrochemical device according to this application.

[0256] 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.

[0257] 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.

[0258] Example

[0259] The following describes the performance evaluation based on the embodiments and comparative examples of the lithium-ion battery of this application.

[0260] I. Preparation of Lithium-ion Batteries

[0261] 1. Preparation of the negative electrode

[0262] Artificial graphite, 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 then coated onto a 12μm current collector. After drying and cold pressing, the material was cut into sheets and had tabs welded to obtain the negative electrode.

[0263] rubber name 1 Styrene-butadiene rubber (SBR) 2 Acrylic styrene-butadiene rubber copolymer 3 Styrene-acrylate copolymer 4 Chlorotrifluoroethylene-styrene-butadiene rubber blend 5 HFP (hexafluoropropylene) styrene-butadiene rubber blend

[0264] 2. Preparation of the positive electrode

[0265] Lithium cobalt oxide (LiCoO2), conductive material (Super-P), and polyvinylidene fluoride (PVDF) were mixed with N-methylpyrrolidone (NMP) in a mass ratio of 95%:2%:3% and stirred until homogeneous to obtain a positive electrode slurry. This positive electrode slurry was coated onto a 12μm aluminum foil, dried, cold-pressed, and then cut and welded to obtain the positive electrode.

[0266] 3. Preparation of electrolyte

[0267] EC, PC, and DEC (weight ratio 1:1:1) were mixed under a dry argon atmosphere, and LiPF6 was added and mixed thoroughly to form a basic electrolyte with a LiPF6 concentration of 1.15 mol / L. Electrolytes for different embodiments and comparative examples were obtained by adding different amounts of additives to the basic electrolyte.

[0268] The abbreviations and names of the components in the electrolyte are shown in the table below:

[0269]

[0270] 4. Preparation of the separating membrane

[0271] Polyethylene (PE) porous polymer film is used as the separator.

[0272] 5. Preparation of lithium-ion batteries

[0273] 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.

[0274] II. Testing Methods

[0275] 1. Test methods for the rate performance of lithium-ion batteries

[0276] At 25°C, the lithium-ion battery was discharged to 3.0V at 0.2C, left to stand for 5 minutes, charged to 4.4V at 0.5C, and then charged at a constant voltage to 0.05C, left to stand for 5 minutes. The discharge rate was adjusted, and discharge tests were conducted at 0.2C and 5.0C respectively to obtain the discharge capacity. The capacity obtained at 5.0C was compared with the capacity obtained at 0.2C to obtain the ratio, which was used to characterize the rate performance of the lithium-ion battery.

[0277] 2. Test method for thickness expansion rate of lithium-ion batteries

[0278] At 25°C, the lithium-ion battery was left to stand for 30 minutes, and its thickness T1 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 T2 of the lithium-ion battery was measured again. The thickness expansion rate of the lithium-ion battery was calculated using the following formula:

[0279] Thickness expansion rate = [(T2-T1) / T1]×100%.

[0280] III. Test Results

[0281] Table 1 shows the effects of the elongation X% at the yield point of the negative electrode mixture layer, the median particle size Y μm of the negative electrode active material, and their relationship on the rate performance and thickness expansion rate of lithium-ion batteries.

[0282] Table 1

[0283]

[0284] The " / " indicates that the feature is not added or is not present.

[0285] The results show that when the elongation at the yield point of the negative electrode compound layer (X%) and the median particle size (Yμm) of the negative electrode active material satisfy 0.1≤X / Y≤30 and the electrolyte includes compounds with cyano groups, the expansion / contraction of the negative electrode caused by the charging and discharging process can be suppressed, the interface between the negative electrode compound layer and the electrolyte can be stabilized, the rate performance of lithium-ion batteries can be significantly improved, the thickness expansion rate can be reduced, and the safety performance can be improved.

[0286] Table 2 shows the effect of rubber on the rate performance and thickness expansion rate of lithium-ion batteries. Examples 2-1 to 2-9 differ from Example 1-1 only in the parameters listed in Table 2.

[0287] Table 2

[0288]

[0289]

[0290] The results show that the elongation at the yield point of the negative electrode compound layer can be adjusted by using different rubbers. When the elongation at the yield point of the negative electrode compound layer is in the range of 10% to 30% and Y is in the range of 1 to 50, the rate performance of the lithium-ion battery can be further improved and its thickness expansion rate can be reduced.

[0291] Table 3 shows the effect of trace metals in the negative electrode active material on the rate performance and thickness expansion rate of lithium-ion batteries. Examples 3-1 to 3-8 differ from Example 1-1 only in the parameters listed in Table 3.

[0292] Table 3

[0293]

[0294] The " / " indicates that the feature is not added or is not present.

[0295] The results show that the presence of trace metal elements (i.e., less than 0.05% of iron, molybdenum and / or copper) in the negative electrode active material can further improve the rate performance of lithium-ion batteries, reduce their thickness expansion rate, and improve their safety performance.

[0296] Table 4 shows the effect of compounds with cyano groups on improving the rate performance and thickness expansion rate of lithium-ion batteries. Examples 4-1 to 4-6 differ from Example 1-1 only in the parameters listed in Table 4.

[0297] Table 4

[0298]

[0299]

[0300] Examples 4-1, 4-4, and 4-5 demonstrate that combining a higher content of non-ether-bonded dinitrile compounds (ADN or SN) with a lower content of ether-bonded dinitrile compounds (EDN) can further improve the rate performance of lithium-ion batteries, reduce their thickness expansion rate, and improve their safety performance.

[0301] Examples 4-2, 4-3, and 4-6 show that combining a higher content of ether-free dinitrile compounds (ADN or SN) with a lower content of trinitrile compounds (HTCN or TCEP) can further improve the rate performance of lithium-ion batteries, reduce their thickness expansion rate, and improve their safety performance.

[0302] Table 5 shows the effect of electrolyte composition on the rate performance and thickness expansion rate of lithium-ion batteries. Examples 5-1 to 5-31 differ from Example 1-1 only in the parameters listed in Table 5.

[0303] Table 5

[0304]

[0305]

[0306] The " / " indicates that the feature is not added or is not present.

[0307] The results show that, based on the elongation X% at the yield point of the negative electrode compound layer and the median particle size Y μm of the negative electrode active material satisfying 0.1≤X / Y≤30, and the electrolyte including compounds with cyano groups, when the electrolyte further contains fluoroethylene carbonate, compounds containing sulfur-oxygen double bonds, lithium difluorophosphate, and / or compounds of formula 1, the rate performance of lithium-ion batteries can be further improved, their thickness expansion rate reduced, and their safety performance improved.

[0308] Table 6 shows the effect of the relationship between the median particle size Y μm of the negative electrode active material and the content b% of fluoroethylene carbonate in the electrolyte on the rate performance and thickness expansion rate of the lithium-ion battery. Examples 6-1 to 6-9 differ from Examples 1-1 or 5-1 only in the parameters listed in Table 6.

[0309] Table 6

[0310]

[0311] The results show that when the content of fluoroethylene carbonate in the electrolyte is between 0.1% and 10%, the rate performance of lithium-ion batteries can be further improved, their thickness expansion rate reduced, and their safety performance improved. When the median particle size Y μm of the negative electrode active material and the content b% of fluoroethylene carbonate in the electrolyte satisfy 4 ≤ Y × b ≤ 200, the rate performance of lithium-ion batteries can be further improved, their thickness expansion rate reduced, and their safety performance improved.

[0312] Table 7 shows the effect of the relationship between the elongation at the yield point of the negative electrode binder layer (X%) and the content (Z%) of cyanide-containing compounds in the electrolyte on the rate performance and thickness expansion rate of the lithium-ion battery. Examples 7-1 to 7-6 differ from Example 1-1 only in the parameters listed in Table 7.

[0313] Table 7

[0314]

[0315] The results show that when the elongation at the yield point of the negative electrode binder layer (X%) and the content of cyano compounds in the electrolyte (Z%) satisfy 2 ≤ X / Z ≤ 100, the rate performance of lithium-ion batteries can be further improved, their thickness expansion rate can be reduced, and their safety performance can be improved.

[0316] 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.

[0317] 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 negative electrode comprises a negative electrode current collector and a negative electrode mixture layer formed on the negative electrode current collector, the negative electrode mixture layer comprising a negative electrode active material, wherein: The elongation at the yield point of the negative electrode mixture layer is X%, and the median particle size of the negative electrode active material is Y µm. X and Y satisfy the following conditions: X is in the range of 10 to 30, Y is in the range of 3 to 30, and 0.5≤X / Y≤10. The negative electrode compound layer includes rubber, which includes at least one of styrene-butadiene rubber, isoprene rubber, butadiene rubber, fluororubber, acrylonitrile-butadiene rubber, and styrene-propylene rubber, and the rubber further includes at least one of acrylic acid functional groups, trichlorofluoroethylene functional groups, or hexafluoropropylene functional groups. The electrolyte includes compounds having a cyano group, which include dinitrile compounds without ether bonds, dinitrile compounds with ether bonds, and trinitrile compounds. Based on the weight of the electrolyte, the content of dinitrile compounds without ether bonds is greater than the content of dinitrile compounds with ether bonds, and the content of dinitrile compounds without ether bonds is greater than the content of trinitrile compounds. The content of the cyano compound is Z% based on the weight of the electrolyte, where Z is in the range of 5 to 10. The ether-free dinitrile compound includes at least one selected from glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, tetramethylsuccinate, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 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 dinitrile compound containing an ether bond includes at least one of 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-cyanoethyl) ether, 1,3-di(2-cyanoethoxy)propane, 1,4-di(2-cyanoethoxy)butane, 1,5-di(2-cyanoethoxy)pentane, or ethylene glycol di(4-cyanobutyl) ether; The trinitrile compound includes 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.

2. The electrochemical device according to claim 1, wherein X and Z satisfy: 2 ≤ X / Z ≤ 100.

3. The electrochemical device according to claim 1, wherein the negative electrode active material has at least one of the following characteristics: (i) including at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, amorphous carbon, silicon-containing materials, tin-containing materials, and alloy materials; (ii) Includes a metal, said metal including at least one of molybdenum, iron or copper, and the content of said metal is less than 0.05% based on the weight of said negative electrode mixture layer.

4. The electrochemical device according to claim 1, wherein the electrolyte further comprises at least one of the following compounds: a) Fluorinated ethylene carbonate; b) Compounds containing sulfur-oxygen double bonds; c) Lithium difluorophosphate; d) Compound of Formula 1: in: Formula 1; R 1 R 2 R 3 R 4 R 5 and R 6 Each is independently hydrogen or C1-C 10 alkyl; L1 and L2 are each independently -(CR 7 R 8 ) n -; R 7 and R 8 Each is independently hydrogen or C1-C 10 Alkyl groups; and n is 1, 2, or 3.

5. The electrochemical device according to claim 4, wherein the compound of formula 1 comprises at least one of the following compounds: Formula 1-1 Formula 1-2 Formula 1-3 Formula 1-4 Formulas 1-5 Equations 1-6.

6. The electrochemical device according to claim 4, wherein the content of the compound of formula 1 is in the range of 0.01% to 5% based on the weight of the electrolyte.

7. The electrochemical device according to claim 4, wherein the content of the fluoroethylene carbonate is b% based on the weight of the electrolyte, and b is in the range of 0.1 to 10%.

8. The electrochemical device according to claim 7, wherein the relationship between Y and b satisfies: 4 ≤ Y × b ≤ 200.

9. An electronic device comprising an electrochemical device according to any one of claims 1-8.

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