WO2023123031A1 - Electrochemical device and electronic device - Google Patents

Abstract

The present application relates to an electrochemical device and an electronic device. Specifically, the present application provides 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 active material layer formed on the negative electrode current collector; the negative electrode active material layer comprises a non-ionic surfactant; and the electrolyte comprises lithium alkyl sulfate. The electrochemical device of the present application has improved floating-charge performance and safety.

Description

Electrochemical devices and electronic devices technical field

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

Background technique

In recent years, electrochemical devices (eg, Li-ion batteries), as a green secondary battery with high energy density and power density, have been widely used in mobile phones, tablet computers, electric vehicles, etc. However, the electrolytes used in existing lithium-ion batteries usually include flammable organic solvents such as ethylene carbonate, dimethyl carbonate, and diethyl carbonate, which are prone to violent combustion and even cause battery explosions when thermal runaway occurs. Therefore, the safety of lithium-ion batteries has attracted more and more attention.

Although battery manufacturers, raw material suppliers and scientific research institutes have done a lot of work to improve the performance of lithium-ion batteries, the existing methods are still unable to effectively improve the floating charge performance of lithium-ion batteries and fundamentally control the heat dissipation of lithium-ion batteries. out of control.

In view of this, there is a need to provide an electrochemical device and an electronic device with improved float performance and safety.

Contents of the invention

The embodiments of the present application solve the problems existing in the prior art to some extent by providing an electrochemical device and an electronic device with improved float charging performance and safety.

In one aspect of the present application, the present application provides an electrochemical device, which includes: a positive electrode, a negative electrode and an electrolyte, the negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, wherein: The negative electrode active material layer includes a nonionic surfactant, and the electrolytic solution includes alkyl lithium sulfate.

According to an embodiment of the present application, based on the weight of the negative electrode active material layer, the content of the nonionic surfactant is a%; based on the weight of the electrolyte, the content of the alkyl lithium sulfate is b% ; and a and b satisfy: 0.1≤a/b≤2.

According to the embodiment of the present application, a ranges from 0.01 to 5.

According to the embodiment of the present application, the value of b ranges from 0.01 to 5.

According to an embodiment of the present application, the nonionic surfactant has a segment formed by an oxyethylene structure.

According to an embodiment of the present application, the hydrophilic-lipophilic balance value of the nonionic surfactant is in the range of 8-19.

According to an embodiment of the present application, the nonionic surfactants include polyoxyethylene alkyl ethers, sorbitan fatty acid esters, glycerin fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, At least one of oxyethylene sorbitan fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene resin hardened castor oil, or polyoxyethylene alkylamine.

According to an embodiment of the present application, the alkyl lithium sulfate includes a compound of formula I:

in:

R is selected from the following groups that are unsubstituted or substituted by one or more halogens: C1-20 alkyl, C2-20 alkoxy, C6-12 aryl, C2-10 alkenyl, C2-10 alkynyl, One of C3-18 chain ester groups, C3-18 cyclic ester groups, C4-10 silane or C2-10 cyano-containing alkyl groups.

According to an embodiment of the present application, the alkyl lithium sulfate includes lithium methylsulfate, lithium ethylsulfate, lithium propylsulfate, lithium butylsulfate, lithium pentylsulfate, lithium hexylsulfate, lithium heptylsulfate, lithium octylsulfate, Lithium sulfate, lithium isopropyl sulfate, lithium sec-butyl sulfate, lithium trifluoromethyl sulfate, lithium 2,2,2-trifluoroethyl sulfate, lithium 2,2,3,3-tetrafluoropropyl sulfate, Lithium 1,1,1,3,3,3-hexafluoro-2-propylsulfate, lithium methoxyethylsulfate, lithium ethoxyethylsulfate, lithium methoxypropylsulfate, lithium phenylsulfate , 4-methylphenyl lithium sulfate, 4-fluorophenyl lithium sulfate, perfluorophenyl lithium sulfate, vinyl lithium sulfate, allyl lithium sulfate, propargyl lithium sulfate, 1-oxo-1-( 2-propynyloxy)propan-2-yllithium sulfate, 2-(trimethylsilyl)ethylsulfate lithium, 2-cyanoethylsulfate lithium or 1,3-dicyanopropynyl- At least one of lithium 2-ylsulfate; preferably at least one of lithium hexylsulfate, lithium trifluoromethylsulfate or lithium 2-cyanoethylsulfate.

According to an embodiment of the present application, the electrolyte solution further includes a compound containing fluorine and phosphorus, and the compound containing fluorine and phosphorus includes at least one of lithium difluorophosphate, lithium monofluorophosphate or a compound of formula II:

Wherein R is C1-10 hydrocarbon group or C1-10 hydrocarbon group substituted by halogen.

According to the embodiments of the present application, the compound of formula II comprises at least one of the following compounds:

According to an embodiment of the present application, based on the weight of the electrolyte, the content of the lithium alkyl sulfate is b%, the content of the compound containing fluorine and phosphorus is c%, and b and c satisfy: 0.5≤b+ c≤5 and 0.4≤b/c≤5.

According to an embodiment of the present application, based on the weight of the electrolyte, the content of the compound containing fluorine and phosphorus is c%, and the value of c ranges from 0.1 to 5.

According to the embodiment of the present application, the value of c ranges from 0.2 to 3.

In another aspect of the present application, the present application provides an electronic device comprising the electrochemical device according to the present application.

The specific combination of the negative electrode active material layer including the non-ionic surfactant and the electrolyte solution including alkyl lithium sulfate used in the present application can significantly improve the float charge performance and safety of the electrochemical device.

Additional aspects and advantages of the embodiments of the present application will be partially described, shown, or explained through the implementation of the embodiments of the present application in the subsequent description.

Detailed ways

Embodiments of the present application will be described in detail below. The examples of the present application should not be construed as limiting the present application.

Unless otherwise expressly indicated, the following terms used herein have the meanings indicated below.

In the detailed description and claims, a list of items linked by the term "at least one of" may mean any combination of the listed items. For example, if the items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if the items A, B, and C are listed, 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".

The term "hydrocarbyl" encompasses alkyl, alkenyl, alkynyl.

The term "alkyl" is intended to be a straight chain saturated hydrocarbon structure having from 1 to 20 carbon atoms. "Alkyl" is also contemplated as branched or cyclic hydrocarbon structures having from 3 to 20 carbon atoms. When an alkyl group having a specific number of carbons is specified, all geometric isomers having that number of carbons are intended to be encompassed; thus, for example, "butyl" is meant to include n-butyl, sec-butyl, iso-butyl, 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 Base etc.

The term "alkenyl" refers to a monovalent unsaturated hydrocarbon group which may be straight-chain or branched and which has at least one and usually 1, 2 or 3 carbon-carbon double bonds. Unless otherwise defined, such alkenyl groups typically contain 2 to 20 carbon atoms and include, for example, -C _2-4 alkenyl, -C _2-6 alkenyl, and -C _2-10 alkenyl. Representative alkenyl groups include, for example, ethenyl, n-propenyl, isopropenyl, n-but-2-enyl, but-3-enyl, n-hex-3-enyl, and the like.

The term "alkynyl" refers to a monovalent unsaturated hydrocarbon group which may be straight-chain or branched and has at least one, and usually 1, 2 or 3, carbon-carbon triple bonds. Unless otherwise defined, such alkynyl groups typically contain 2 to 20 carbon atoms and include, for example, -C _2-4 alkynyl, -C _3-6 alkynyl, and -C _3-10 alkynyl. Representative alkynyl groups include, for example, ethynyl, prop-2-ynyl (n-propynyl), n-but-2-ynyl, n-hex-3-ynyl, and the like.

The term "aryl" means a monovalent aromatic hydrocarbon having a single ring (eg, phenyl) or fused rings. Fused ring systems include those that are fully unsaturated (eg, naphthalene) as well as those that are partially unsaturated (eg, 1,2,3,4-tetrahydronaphthalene). Unless otherwise defined, such aryl groups typically contain 6 to 26 carbon ring atoms and include, for example, -C _6-10 aryl. Representative aryl groups include, for example, phenyl, methylphenyl, propylphenyl, isopropylphenyl, benzyl, and naphthalen-1-yl, naphthalen-2-yl, and the like.

The term "cycloalkyl" encompasses cyclic alkyl groups. The cycloalkyl group may be a cycloalkyl group of 3-20 carbon atoms, a cycloalkyl group of 6-20 carbon atoms, a cycloalkyl group of 3-12 carbon atoms, or a cycloalkyl group of 3-6 carbon atoms. For example, cycloalkyl may be cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. Additionally, cycloalkyl groups may be optionally substituted.

The term "halogen" refers to the elements of group VIIA of the periodic table of chemical elements, including fluorine (F), chlorine (Cl), bromine (Br), iodine (I) and astatine (At).

Overcharging is one of the causes of thermal runaway of Li-ion batteries. When overcharging occurs, lithium metal is deposited on the negative electrode. When the negative electrode intercalates more and more lithium and reaches saturation, the excess lithium will form lithium dendrites on the surface of the negative electrode in the form of metallic lithium, and the growth of lithium dendrites will pierce the separator and cause an internal short circuit in the battery cell. In addition, the voltage of the lithium-ion battery will continue to increase as the overcharge progresses, and then reach the electrolyte decomposition voltage, causing the electrolyte to decompose and produce gas. The increase in gas production will cause the internal air pressure of the lithium-ion battery to increase to exceed the valve opening pressure, causing the explosion-proof valve of the battery cell to open, resulting in a safety hazard. The methods to prevent lithium-ion batteries from overcharging mainly include adding external protection devices and adding new electrolyte additives. However, the addition of external devices to prevent overcharging will increase the cost of cell manufacturing, and the introduction of new electrolyte additives may lead to new side reactions.

The present application solves the above-mentioned problems by using a combination of a negative electrode active material layer including a nonionic surfactant and an electrolytic solution including alkyl lithium sulfate. Non-ionic surfactants have a very large contribution to the surface smoothness of the negative electrode, which can reduce the risk of lithium dendrites. However, when the electrochemical device is under high temperature and high pressure, the non-ionic surfactant will increase the float thickness of the lithium-ion battery. Adding alkyl lithium sulfate to the electrolyte can effectively improve the float charge performance of lithium-ion batteries, because alkyl lithium sulfate can reduce the ion conductance and electron conductance inside the negative electrode. At the same time, the combination of the negative electrode active material layer including the non-ionic surfactant and the electrolyte solution including alkyl lithium sulfate can also significantly improve the overcharge safety of the lithium-ion battery.

I. Negative electrode

The negative electrode includes a negative electrode current collector and a positive electrode active material layer disposed on one or both surfaces of the negative electrode current collector, and the negative electrode active material layer contains the negative electrode active material. The negative electrode active material layer may be one or more layers, and each layer of the multilayer negative electrode active material may contain the same or different negative electrode active materials. The negative electrode active material is any material capable of reversibly intercalating and deintercalating metal ions such as lithium ions. In some embodiments, the chargeable capacity of the negative active material is greater than the discharge capacity of the positive active material, so as to prevent unintentional precipitation of lithium metal on the negative electrode during charging.

A main feature of the electrochemical device of the present application is that the negative electrode active material layer includes a nonionic surfactant.

In some embodiments, the nonionic surfactant has segments formed from ethylene oxide structures.

In some embodiments, the nonionic surfactant has a Hydrophile-Lipophile Balance (HLB) value in the range of 8-19.

In some embodiments, the nonionic surfactant includes polyoxyethylene alkyl ether, sorbitan fatty acid ester, glycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene At least one of ethylene sorbitan fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene resin hardened castor oil, or polyoxyethylene alkylamine.

In some embodiments, based on the weight of the negative electrode active material layer, the content of the nonionic surfactant is a%, and the value of a is in the range of 0.01 to 5. In some embodiments, a ranges from 0.1 to 3. In some embodiments, a is 0.1, 0.3, 0.5, 1, 2, 2.5, 3, 3.5, 4, 4.5, 5 or within a range consisting of any two values above. When the content of the nonionic surfactant in the negative electrode active material layer is within the above range, the float performance and safety of the electrochemical device can be further improved.

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

When the negative electrode current collector is a metal material, the form of the negative electrode current collector may include, but not limited to, metal foil, metal cylinder, metal strip, metal plate, metal film, expanded metal, 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 a rolled copper foil based on a rolling method or an electrolytic copper foil based on an electrolytic method.

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

The negative electrode active material is not particularly limited as long as it can reversibly store and release lithium ions. Examples of negative electrode active materials may include, but are not limited to, carbon materials such as natural graphite and artificial graphite; metals such as silicon (Si) and tin (Sn); or oxides of metal elements such as Si and Sn. The negative electrode active materials can be used alone or in combination.

The negative active material layer may further include a negative binder. The negative electrode binder can improve the combination of the negative electrode active material particles and the combination of the negative electrode active material and the current collector. The type of negative electrode binder is not particularly limited, as long as it is a material stable to the electrolyte solution or the solvent used in electrode production. In some embodiments, the negative binder includes a resin binder. Examples of resin binders include, but are not limited to, fluororesins, polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, and the like. When using a water-based solvent to prepare the negative electrode mixture slurry, the negative electrode binder includes, but is not limited to, carboxymethyl cellulose (CMC) or its salt, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or Its salt, polyvinyl alcohol, etc.

The negative electrode can be prepared by the following method: coating the negative electrode mixture slurry comprising negative electrode active material, resin binder, etc. on the negative electrode current collector, after drying, calendering to form negative electrode active material layers on both sides of the negative electrode current collector, thus Negative pole is available.

II. Electrolyte

The electrolytic solution used in the electrochemical device of the present application includes an electrolyte and a solvent for dissolving the electrolyte.

Another main feature of the electrochemical device of the present application is that the electrolyte includes alkyl lithium sulfate.

In some embodiments, the lithium alkyl sulfate comprises a compound of formula I:

in:

R is selected from the following groups that are unsubstituted or substituted by one or more halogens: C1-20 alkyl, C2-20 alkoxy, C6-12 aryl, C2-10 alkenyl, C2-10 alkynyl, One of C3-18 chain ester groups, C3-18 cyclic ester groups, C4-10 silane or C2-10 cyano-containing alkyl groups.

In some embodiments, the alkyl lithium sulfate includes lithium methylsulfate, lithium ethylsulfate, lithium propylsulfate, lithium butylsulfate, lithium pentylsulfate, lithium hexylsulfate, lithium heptylsulfate, lithium octylsulfate Lithium, lithium isopropylsulfate, lithium sec-butylsulfate, lithium trifluoromethylsulfate, lithium 2,2,2-trifluoroethylsulfate, lithium 2,2,3,3-tetrafluoropropylsulfate, 1 ,1,1,3,3,3-hexafluoro-2-propyl lithium sulfate, lithium methoxyethyl sulfate, lithium ethoxyethyl sulfate, lithium methoxypropyl sulfate, lithium phenyl sulfate, Lithium 4-methylphenylsulfate, lithium 4-fluorophenylsulfate, lithium perfluorophenylsulfate, lithium vinylsulfate, lithium allylsulfate, lithium propargylsulfate, 1-oxo-1-(2 -propynyloxy)propan-2-yl lithium sulfate, 2-(trimethylsilyl)ethyl lithium sulfate, 2-cyanoethyl lithium sulfate or 1,3-dicyanopropynyl-2 - at least one of lithium sulfate.

In some embodiments, the alkyl lithium sulfate includes at least one of lithium hexyl sulfate, lithium trifluoromethyl sulfate or lithium 2-cyanoethyl sulfate.

In some embodiments, based on the weight of the electrolytic solution, the content of the lithium alkyl sulfate is b%, and a and b satisfy: 0.1≤a/b≤2. In some embodiments, a and b satisfy: 0.1≦a/b≦1. In some embodiments, a and b satisfy the following relationship: 0.2≦a/b≦0.5. In some embodiments, a/b is 0.1, 0.2, 0.5, 1, 1.2, 1.5, 1.8, 2 or within a range consisting of any two values above. When the content of the nonionic surfactant in the positive electrode active material layer and the content of alkyl lithium sulfate in the electrolyte satisfy the above relationship, the float charge performance and safety of the electrochemical device can be further improved.

In some embodiments, b ranges from 0.01 to 5. In some embodiments, b ranges from 0.1 to 3. In some embodiments, b is 0.1, 0.3, 0.5, 1, 2, 2.5, 3, 3.5, 4, 4.5, 5 or within a range consisting of any two values above. When the content of alkyl lithium sulfate in the electrolyte is within the above range, the float charge performance and safety of the electrochemical device can be further improved.

In some embodiments, the electrolyte also includes a compound containing fluorine and phosphorus, and the compound containing fluorine and phosphorus includes at least one of lithium difluorophosphate, lithium monofluorophosphate, or a compound of formula II:

Wherein R is C1-10 hydrocarbon group or C1-10 hydrocarbon group substituted by halogen.

In some embodiments, the compound of formula II comprises at least one of the following compounds:

The compound containing fluorine and phosphorus can further reduce the ion conductance and electron conductance inside the pole piece, thereby further improving the floating charge performance and safety of the electrochemical device.

In some embodiments, based on the weight of the electrolyte, the content of the lithium alkyl sulfate is b%, the content of the compound containing fluorine and phosphorus is c%, and b and c satisfy: 0.5≤b+c ≤5 and 0.4≤b/c≤5. In some embodiments, 1≦b+c≦3. In some embodiments, b+c is 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or within a range consisting of any two values above. In some embodiments, 0.5≤b/c≤3. In some embodiments, 1≦b/c≦2. When the content of the alkyl lithium sulfate and the compound containing fluorine and phosphorus in the electrolyte satisfies the above relationship, the float charge performance and safety of the electrochemical device can be further improved.

In some embodiments, c ranges from 0.1 to 5. In some embodiments, c ranges from 0.2 to 3. In some embodiments, c ranges from 0.5 to 2. In some embodiments, c ranges from 1 to 1.5. In some embodiments, c is 0.1, 0.3, 0.5, 1, 2, 2.5, 3, 3.5, 4, 4.5, 5 or within a range consisting of any two values above. When the content of the compound containing fluorine and phosphorus in the electrolyte satisfies the above relationship, the ionic conductance and electron conductance inside the pole piece can be further reduced, thereby further improving the float charge performance and safety of the electrochemical device.

In some embodiments, the electrolyte solution further comprises any non-aqueous solvent known in the prior art as a solvent for the electrolyte solution.

In some embodiments, the non-aqueous solvent includes, but is not limited to, one or more of the following: cyclic carbonate, chain carbonate, cyclic carboxylate, chain carboxylate, cyclic Ethers, chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and aromatic fluorinated solvents.

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 butylene carbonate. In some embodiments, the cyclic carbonate has 3-6 carbon atoms.

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 carbonate Chain carbonates such as ethyl n-propyl carbonate, ethyl n-propyl carbonate, di-n-propyl carbonate, etc. Examples of chain carbonates substituted with fluorine may include, but are not limited to, one or more of the following: bis(fluoromethyl)carbonate, bis(difluoromethyl)carbonate, bis(trifluoromethyl)carbonate base) carbonate, bis(2-fluoroethyl)carbonate, bis(2,2-difluoroethyl)carbonate, bis(2,2,2-trifluoroethyl)carbonate, 2-fluoroethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate and 2,2,2-trifluoroethyl methyl carbonate, etc.

In some embodiments, examples of the cyclic carboxylate may include, but are not limited to, one or more of the following: one or more of γ-butyrolactone and γ-valerolactone. In some embodiments, some of the hydrogen atoms of the cyclic carboxylate may be replaced by fluorine.

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

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.

In some embodiments, examples of the chain ethers may include, but are not limited to, one or more of the following: dimethoxymethane, 1,1-dimethoxyethane, 1,2- Dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxy Methoxyethane and 1,2-ethoxymethoxyethane, etc.

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 phosphate Diethyl ester, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tris(2,2,2- phosphate Trifluoroethyl) ester and tris(2,2,3,3,3-pentafluoropropyl) phosphate, etc.

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, dimethylsulfone, disulfone Ethyl sulfone, ethyl methyl sulfone, methyl propyl 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 replaced by fluorine.

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.

In some embodiments, the solvent used in the electrolyte of the present application includes cyclic carbonates, chain carbonates, cyclic carboxylates, chain carboxylates, and combinations thereof. In some embodiments, the solvent used in the electrolyte of the present application comprises an organic solvent selected from the group consisting of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propionic acid Propyl ester, n-propyl acetate, ethyl acetate and combinations thereof. In some embodiments, the solvent used in the electrolyte of the present application comprises: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, γ-butyrolactone and combinations thereof .

In some embodiments, the electrolyte is not particularly limited, and any known substance as an electrolyte can be used arbitrarily. In the case of lithium secondary batteries, lithium salts are generally used. Examples of electrolytes may include, but are not limited to, inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAlF ₄ , LiSbF ₆ , LiWF ₇ ; lithium tungstates such as LiWOF ₅ ; HCO ₂ Li, CH ₃ CO ₂ Li, CH ₂ FCO ₂ Li, CHF ₂ CO ₂ Li, CF ₃ CO ₂ Li, CF ₃ CH ₂ CO ₂ Li, CF 3 CF ₂ CO ₂ Li, CF ₃ CF ₂ CF ₂ CO ₂ Li, CF ₃ CF _{2 CF 2} Lithium carboxylate salts such as CF ₂ CO ₂ Li; FSO ₃ Li, CH ₃ SO ₃ Li, CH ₂ FSO ₃ Li, CHF ₂ SO ₃ Li, CF ₃ SO ₃ Li, CF ₃ CF ₂ SO ₃ Li, CF ₃ CF ₂ CF ₂ SO ₃ Li, CF ₃ CF ₂ CF ₂ CF ₂ SO ₃ Li and other sulfonate lithium salts; LiN(FCO) ₂ , LiN(FCO)(FSO ₂ ), LiN(FSO ₂ ) ₂ , LiN( FSO ₂ )(CF ₃ SO ₂ ), LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , cyclic lithium 1,2-perfluoroethanebissulfonylimide, cyclic 1 , 3-perfluoropropane bissulfonylimide lithium, LiN(CF ₃ SO ₂ )(C ₄ F ₉ SO ₂ ) and other imide lithium salts; LiC(FSO ₂ ) ₃ , LiC(CF ₃ SO ₂ ) _3. LiC(C ₂ F ₅ SO ₂ ) ₃ and other methylated lithium salts; bis(malonato)borate lithium salt, difluoro(malonate) borate lithium salt, etc. (malonato)boric acid Lithium salts; lithium tris(malonato)phosphate, lithium difluorobis(malonato)phosphate, lithium tetrafluoro(malonato)phosphate and other (malonato)phosphate lithium salts; and LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF ₄ (CF ₃ SO ₂ ) ₂ , LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiBF ₃ C ₃ F ₇ , LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ (CF ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ and other fluorine-containing Organolithium salts; lithium difluorooxalate borate, lithium bis(oxalate)borate and other lithium oxalate borate salts; lithium tetrafluorooxalatophosphate, lithium difluorobis(oxalato)phosphate, tri(oxalato)phosphoric acid Lithium oxalatophosphate lithium salts, etc.

In some embodiments, the electrolyte is selected from LiPF ₆ , LiSbF ₆ , FSO ₃ Li, CF ₃ SO ₃ Li, LiN(FSO ₂ ) ₂ , LiN(FSO ₂ )(CF ₃ SO ₂ ), LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , cyclic lithium 1,2-perfluoroethanebissulfonimide, cyclic lithium 1,3-perfluoropropanebissulfonimide, LiC(FSO ₂ ) ₃ , LiC(CF ₃ SO ₂ ) ₃ , LiC(C ₂ F ₅ SO ₂ ) ₃ , LiBF ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (C ₂ F ₅ ) _3. Lithium difluorooxalate borate, lithium bis(oxalate)borate or lithium difluorobis(oxalato)phosphate, which help to improve the output power characteristics, high-rate charge and discharge characteristics, and high-temperature storage characteristics of electrochemical devices and cycle characteristics, etc.

The content of the electrolyte is not particularly limited as long as the effect of the present application is not impaired. 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 formed by any two values above. When the electrolyte concentration is within the above range, the lithium as charged particles will not be too small, and the viscosity can be kept in an appropriate range, so it is easy to ensure good electrical conductivity.

When two or more electrolytes are used, the electrolyte includes at least one salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate. In some embodiments, the electrolyte includes a salt selected from the group consisting of monofluorophosphate, oxalate, and fluorosulfonate. In some embodiments, the electrolyte includes a lithium salt. In some embodiments, the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is present at greater than 0.01% or greater than 0.1% by weight of the electrolyte. In some embodiments, the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate comprises less than 20% or less than 10% by weight of the electrolyte. In some embodiments, the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate and fluorosulfonate is within the range formed by any two of the above values.

In some embodiments, the electrolyte includes one or more substances selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate and one or more salts other than these. Other salts include the lithium salts exemplified above, and in some examples, LiPF ₆ , LiN(FSO ₂ )(CF ₃ SO ₂ ), LiN(CF ₃ SO ₂ ) ₂ , LiN( C ₂ F ₅ SO ₂ ) ₂ , cyclic lithium 1,2-perfluoroethanebissulfonimide, cyclic lithium 1,3-perfluoropropanebissulfonimide, LiC(FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC(C ₂ F ₅ SO ₂ ) ₃ , LiBF ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (C ₂ F ₅ ) ₃ . In some embodiments, the additional salt is LiPF ₆ .

In some embodiments, the additional salts are present at greater than 0.01% or greater than 0.1% by weight of the electrolyte. In some embodiments, the additional salts are present at less than 20%, less than 15%, or less than 10% by weight of the electrolyte. In some embodiments, the content of other salts is within the range formed by any two values above. Salts other than these having the above content contribute to the balance of the electrical conductivity and viscosity of the electrolytic solution.

III. Positive electrode

The positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. The positive active material layer may be one or more layers. The positive active material layer includes positive active materials, and each layer of the multilayer positive active materials may contain the same or different positive active materials. The positive electrode active material is any material capable of reversibly intercalating and deintercalating metal ions such as lithium ions.

The type of positive electrode active material is not particularly limited, as long as it can store and release metal ions (for example, lithium ions) electrochemically. In some embodiments, the positive active material is a material containing lithium and at least one transition metal. Examples of positive active materials may include, but are not limited to, lithium transition metal composite oxides and lithium transition metal phosphate compounds.

In some embodiments, the transition metals in the lithium transition metal composite oxide include V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like. In some embodiments, lithium transition metal composite oxides include lithium cobalt composite oxides such as LiCoO ₂ , lithium nickel composite oxides such as LiNiO ₂ , lithium manganese composite oxides such as LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO ₄ , lithium nickel manganese cobalt composite oxides such as LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiNi _0.5 Mn _0.3 Co _0.2 O _{2 ,} etc., in which a part of the transition metal atom which is the main body of these lithium transition metal composite oxides is Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W and other elements substituted . Examples of lithium transition metal composite oxides may include, but are not limited to, LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.85 Co _0.10 Al _0.05 O ₂ , LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiNi _0.45 Co _0.10 Al _0.45 O ₂ , LiMn _1.8 Al _0.2 O ₄ and LiMn _1.5 Ni _0.5 O ₄ etc. Examples of combinations of lithium transition metal composite oxides include, but are not limited to, combinations of LiCoO ₂ and LiMn ₂ O ₄ , wherein a part of Mn in LiMn ₂ O ₄ may be replaced by transition metals (for example, LiNi _0.33 Co _0.33 Mn _0.33 O ₂ ), part of Co in LiCoO ₂ can be replaced by transition metals.

In some embodiments, the transition metals in the lithium-containing transition metal phosphate compound include V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like. In some embodiments, lithium-containing transition metal phosphate compounds include iron phosphates such as LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ) ₃ , LiFeP ₂ O ₇ , and cobalt phosphates such as LiCoPO ₄ , wherein as these lithium transition metal phosphate compounds Some of the transition metal atoms of the main body are replaced by other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc.

In some embodiments, a substance different from its composition may be attached to the surface of the positive electrode active material. Examples of surface attachment substances may include, but are not limited to: oxides such as alumina, silica, titania, zirconia, magnesia, calcium oxide, boron oxide, antimony oxide, bismuth oxide; lithium sulfate, sodium sulfate, potassium sulfate , magnesium sulfate, calcium sulfate, aluminum sulfate and other sulfates; lithium carbonate, calcium carbonate, magnesium carbonate and other carbonates; carbon, etc. By attaching the substance on the surface of the positive electrode active material, the oxidation reaction of the electrolyte solution on the surface of the positive electrode active material can be suppressed, and the life of the electrochemical device can be improved. When the amount of the surface-attached substance is too small, the effect cannot be fully expressed; when the amount of the surface-attached substance is too large, it will hinder the entry and exit of lithium ions, so the resistance may increase. In the present application, a positive electrode active material having a composition different from the positive electrode active material attached to the surface of the positive electrode active material is also referred to as a "positive electrode active material".

In some embodiments, the shape of the positive electrode active material particles includes, but is not limited to, block shape, polyhedron shape, spherical shape, ellipsoidal shape, plate shape, needle shape and columnar shape. In some embodiments, the positive active material particles include primary particles, secondary particles, or a combination thereof. In some embodiments, primary particles may agglomerate to form secondary particles.

The kind of positive electrode conductive material is not limited, and any known conductive material can be used. Examples of positive electrode conductive materials may 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 and the like. The above positive electrode conductive materials can be used alone or in any combination.

The kind of the positive electrode binder used in the manufacture of the positive electrode active material layer is not particularly limited, and in the case of the coating method, as long as it is a material that can be dissolved or dispersed in the liquid medium used in electrode manufacture. Examples of positive electrode binders may include, but are not limited to, one or more of the following: polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, Aramid, cellulose, nitrocellulose and other resin-based polymers; styrene-butadiene rubber (SBR), nitrile rubber (NBR), fluororubber, isoprene rubber, polybutadiene rubber, ethylene-propylene rubber and other rubber Shaped polymer; styrene-butadiene-styrene block copolymer or its hydrogenated product, ethylene-propylene-diene terpolymer (EPDM), styrene-ethylene-butadiene-ethylene copolymer, benzene Thermoplastic elastomeric polymers such as ethylene-isoprene-styrene block copolymer or its hydrogenated products; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, Soft resinous polymers such as propylene-α-olefin copolymers; Fluorine-based polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers ; Ion-conductive polymer compositions with alkali metal ions (especially lithium ions), etc. The above positive electrode binders may be used alone or in any combination.

The kind of solvent used to form the positive electrode slurry is not limited as long as it is a solvent capable of dissolving or dispersing the positive electrode active material, conductive material, positive electrode binder, and thickener used as needed. Examples of the solvent used to form the positive electrode slurry may include any one of aqueous solvents and organic solvents. Examples of the aqueous medium may include, but are not limited to, water, a mixed medium of alcohol and water, and the like. Examples of organic media may include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; acetone, methyl ethyl ketones such as ketone and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; diethyl ether, propylene oxide, tetrahydrofuran (THF ) and other ethers; amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide, etc.

Thickeners are generally used to adjust the viscosity of the slurry. In the case of using an aqueous medium, thickeners and styrene-butadiene rubber (SBR) emulsions can be used for slurrying. The kind of thickener is not particularly limited, and examples thereof may include, but are not limited to, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch , casein and their salts, etc. The above-mentioned thickeners can be used alone or in any combination.

The type of the positive electrode collector is not particularly limited, and it can be any known material suitable for use as the positive electrode collector. Examples of the positive current collector may include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; carbon materials such as carbon cloth and carbon paper. In some embodiments, the positive current collector is a metal material. In some embodiments, the positive current collector is aluminum.

In order to reduce the electronic contact resistance of the positive electrode current collector and the positive electrode active material layer, the surface of the positive electrode current collector may include a conductive aid. Examples of conductive aids may include, but are not limited to, carbon and noble metals such as gold, platinum, and silver.

The positive electrode can be produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. The manufacture of the positive electrode using the positive electrode active material can be carried out by a conventional method, that is, the positive electrode active material and the binder, as well as the conductive material and thickener as required, etc. are dry mixed, made into a sheet, and the obtained The sheet is pressed onto the positive current collector; or these materials are dissolved or dispersed in a liquid medium to make a slurry, and the slurry is coated on the positive current collector and dried to form a positive electrode current collector. A positive electrode active material layer, whereby a positive electrode can be obtained.

IV. Isolation film

In order to prevent a short circuit, a separator is usually provided between the positive electrode and the negative electrode. In this case, the electrolytic solution of the present application is usually used by permeating the separator.

The material and shape of the separator are not particularly limited as long as the effect of the present application is not significantly impaired. The separator can be resin, glass fiber, inorganic material, etc. formed of materials stable to the electrolyte solution of the present application. In some embodiments, the separator includes a porous sheet or a non-woven fabric-like substance with excellent liquid retention properties. Examples of the material of the resin or fiberglass separator may include, but are not limited to, polyolefin, aramid, polytetrafluoroethylene, polyethersulfone, and the like. In some embodiments, the polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The materials for the above separators may be used alone or in any combination.

The isolation film can also be a material formed by laminating the above materials, examples of which include, but not limited to, a three-layer isolation film formed by laminating polypropylene, polyethylene, and polypropylene in this order.

Examples of materials of inorganic substances may include, but are not limited to, oxides such as aluminum oxide and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, sulfates (eg, barium sulfate, calcium sulfate, etc.). Inorganic forms may include, but are not limited to, granular or fibrous.

The form of the separator may be in the form of a film, examples of which include, but are not limited to, non-woven fabrics, woven fabrics, microporous films, and the like. In thin film form, the pore diameter of the isolation membrane is 0.01 μm to 1 μm, and the thickness is 5 μm to 50 μm. In addition to the above-mentioned independent film-shaped separator, the following separator can also be used: a separator formed by forming a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and/or negative electrode using a resin-based binder, For example, a separator is formed by using a fluororesin as a binder to form porous layers on both sides of the positive electrode with 90% of the alumina particles having a particle size of less than 1 μm.

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

When a porous material such as a porous sheet or nonwoven fabric is used as the separator, the porosity of the separator is arbitrary. In some embodiments, the isolation membrane has a porosity greater than 10%, greater than 15%, or greater than 20%. In some embodiments, the separator has a porosity of less than 60%, less than 50%, or less than 45%. In some embodiments, the porosity of the isolation membrane is within the range formed by any two values above. When the porosity of the separator is within the above range, insulation and mechanical strength can be ensured, and membrane resistance can be suppressed, so that the electrochemical device has good safety characteristics.

The average pore diameter of the separator is also arbitrary. In some embodiments, the average pore size of the isolation membrane is less than 0.5 μm or less than 0.2 μm. In some embodiments, the average pore size of the isolation membrane is greater than 0.05 μm. In some embodiments, the average pore diameter of the isolation membrane is within the range formed by any two values above. When the average pore diameter of the separator exceeds the above-mentioned range, short circuits are likely to occur. When the average pore diameter of the isolation membrane is within the above range, the electrochemical device has good safety characteristics.

V. Electrochemical device components

The electrochemical device assembly includes an electrode group, a current collecting structure, an outer casing and a protection element.

The electrode group may have either a laminated structure in which the positive electrode and the negative electrode are laminated with the separator interposed therebetween, or a structure in which the positive electrode and the negative electrode are wound in a spiral shape with the separator interposed therebetween. In some embodiments, the ratio of the mass of the electrode group to the internal volume of the battery (electrode group occupancy) is greater than 40% or greater than 50%. In some embodiments, the electrode set occupancy is less than 90% or less than 80%. In some embodiments, the occupancy of the electrode group is within the range formed by any two values above. When the electrode group occupancy ratio is within the above range, the capacity of the electrochemical device can be ensured, and at the same time, the decrease in characteristics such as repeated charge-discharge performance and high-temperature storage due to an increase in internal pressure can be suppressed.

The current collecting structure is not particularly limited. In some embodiments, the current collecting structure is a structure that reduces the resistance of the wiring portion and the bonding portion. When the electrode group has the above-mentioned laminated structure, it is suitable to use a structure in which the metal core portions of the electrode layers are bundled and welded to the terminal. When the area of one electrode increases, the internal resistance increases, so it is also suitable to provide two or more terminals in the electrode to reduce the resistance. When the electrode group has the above-mentioned winding structure, the internal resistance can be reduced by providing two or more lead wire structures on the positive electrode and the negative electrode respectively, and bundling them on the terminals.

The material of the outer case is not particularly limited, as long as it is stable to the electrolyte solution used. As the exterior case, metals such as nickel-plated steel sheets, stainless steel, aluminum or aluminum alloys, and magnesium alloys, or laminated films of resin and aluminum foil can be used, but not limited to. In some embodiments, the outer casing is aluminum or aluminum alloy metal or a laminated film.

Metal exterior cases include, but are not limited to, encapsulation and sealing structures formed by welding metals together by laser welding, resistance welding, or ultrasonic welding; or riveted structures using the above-mentioned metals through resin spacers. The exterior case using the above-mentioned laminated film includes, but is not limited to, a package sealing structure formed by thermally bonding resin layers to each other, and the like. In order to improve the sealability, a resin different from the resin used in the laminated film may be interposed between the above-mentioned resin layers. When the resin layer is thermally bonded through the collector terminal to form a sealed structure, a resin having a polar group or a modified resin into which a polar group is introduced can be used as the interposed resin due to the bonding between the metal and the resin. In addition, the shape of the exterior body is also arbitrary, and for example, any of cylindrical, square, laminated, button-shaped, large, and the like may be used.

Protection elements can use positive temperature coefficient (PTC) whose resistance increases when abnormal heat generation or excessive current flows, temperature fuses, thermistors, cut off by causing the internal pressure of the battery or the internal temperature to rise sharply at the time of abnormal heat generation A valve (current cut-off valve) for the current flowing in the circuit, etc. The above-mentioned protection elements can be selected under the condition that they do not work in the normal use of high current, and can also be designed in such a way that abnormal heat dissipation or thermal runaway will not occur even if there is no protection element.

The electrochemical device of the present application includes any device that undergoes an electrochemical reaction, and specific examples thereof include a lithium metal secondary battery or a lithium ion secondary battery.

The present application further provides an electronic device, which includes the electrochemical device according to the present application.

The application of the electrochemical device of the present 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 the present application can be used in, but not limited to, notebook computers, pen-based computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-worn Stereo headphones, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, power assist Bicycles, bicycles, lighting equipment, toys, game consoles, clocks, electric tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.

The lithium ion battery is taken as an example below and the preparation of the lithium ion battery is described in conjunction with specific examples. Those skilled in the art will understand that the preparation method described in this application is only an example, and any other suitable preparation methods are described in this application. within range.

Example

1. Preparation of lithium ion battery

1. Preparation of negative electrode

Mix artificial graphite, styrene-butadiene rubber, and sodium carboxymethyl cellulose with deionized water in a mass ratio of 96%:2%:2%, add nonionic surfactant as required, and stir evenly to obtain negative electrode slurry. The negative electrode slurry was coated on a 9 μm copper foil, dried, cold pressed, cut into pieces, and tabs were welded to obtain a negative electrode.

2. Preparation of positive electrode

Lithium cobaltate, Super-P and polyvinylidene fluoride were mixed with N-methylpyrrolidone (NMP) according to the mass ratio of 97:1:2, and stirred evenly to obtain positive electrode slurry. The positive electrode slurry was coated on a 12 μm aluminum foil, dried, cold pressed, cut into pieces, and tabs were welded to obtain a positive electrode.

3. Electrolyte preparation

In a dry argon environment, EC, PC and DEC (weight ratio 1:1:1) were mixed, and LiPF ₆ was added to mix well to form a basic electrolyte, in which the concentration of LiPF ₆ was 12.5%. The electrolytes of different examples and comparative examples were obtained by adding additives with different contents into the basic electrolyte.

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

material name	abbreviation	material name	abbreviation
Vinyl carbonate	EC	Propylene carbonate	PC
diethyl carbonate	DEC	Compound of formula II-1	Formula II-1
Compound of formula II-2	Formula II-2	Compound of formula II-3	Formula II-3

4. Preparation of isolation membrane

A polyethylene porous polymer film is used as a separator.

5. Preparation of Li-ion battery

Wind the obtained positive electrode, separator and negative electrode in sequence, place them in the outer packaging foil, and leave a liquid injection port. The electrolyte solution is poured from the liquid injection port, packaged, and then the lithium-ion battery is produced through processes such as formation and capacity.

2. Test method

1. Test method for overcharge deformation rate of lithium ion battery

At 25°C, let the lithium-ion battery stand still for 30 minutes, then charge it to 4.7V with a constant current at a rate of 0.5C, then charge it at a constant voltage at 4.7V to 0.05C, let it stand for 60 minutes, and measure the thickness T of the lithium-ion battery ₁ . Then charge the lithium-ion battery with a constant current at a rate of 0.1C for 60 minutes, let it stand for 30 minutes, and repeat this step 5 times to make the lithium-ion battery reach 150% state of charge (SOC), and measure the thickness T ₂ of the lithium-ion battery. Calculate the overcharge deformation rate of the lithium-ion battery by the following formula:

Overcharge deformation rate=[(T ₂ -T ₁ )/T ₁ ]×100%.

2. Test method of float charge performance of lithium ion battery

At 25°C, the Li-ion battery was charged at a constant current of 0.5C to 4.7V, and then charged at a constant voltage of 4.7V to 0.05C. Then, the lithium-ion battery was placed in an oven at 50° C., continuously charged at a constant voltage of 4.7 V (the cut-off current was 20 mA), and the thickness change of the lithium-ion battery was monitored. Taking the thickness of the lithium-ion battery at the initial 50% state of charge (SOC) as a benchmark, when the thickness of the lithium-ion battery increases by more than 20%, it is recorded as failure. Record the time from float charge to failure of the lithium-ion battery at 50°C, in hours (h) as the statistical unit.

3. Test results

Table 1 shows the impact of the negative electrode active material layer and electrolyte on the float performance and safety of lithium-ion batteries, wherein the nonionic surfactant in the negative electrode active material layer is polyoxyethylene alkyl ether, and the alkane in the electrolyte is Lithium sulfate is lithium trifluoromethylsulfate.

Table 1

As shown in Comparative Example 1-1, although the electrolyte includes lithium alkyl sulfate, the negative electrode active material layer does not include a nonionic surfactant, the overcharge deformation rate of the lithium-ion battery is higher and the float charge failure time is shorter. As shown in Comparative Example 1-2, although the negative electrode active material layer includes a non-ionic surfactant, but the electrolyte does not include lithium alkyl sulfate, the overcharge deformation rate of the lithium ion battery is high and the floating charge failure time is short.

As shown in Examples 1-1 to 1-15, when the negative electrode active material layer includes a non-ionic surfactant and the electrolyte includes lithium alkyl sulfate, the overcharge deformation rate of the lithium-ion battery can be significantly reduced and its floating rate can be significantly improved. Charging failure time.

In addition, when the content a% of the nonionic surfactant in the negative electrode active material layer and the content b% of the alkyl lithium sulfate in the electrolyte meet 0.1≤a/b≤2, the overcharge deformation rate of the lithium-ion battery can be further reduced And increase its floating charge failure time.

When the content of the nonionic surfactant in the negative electrode active material layer is in the range of 0.01%-5%, the overcharge deformation rate of the lithium ion battery can be further reduced and the floating charge failure time can be improved.

When the content of alkyl lithium sulfate in the electrolyte is in the range of 0.01% to 5%, the overcharge deformation rate of the lithium ion battery can be further reduced and the floating charge failure time can be improved.

Table 2 shows the influence of 1% alkyl lithium sulfate compounds with different structures on the floating charge performance and safety of lithium-ion batteries. Except for the parameters listed in Table 2, the settings of Examples 2-1 to 2-8 are the same as those of Example 1-1.

Table 2

the	Alkyl lithium sulfate	Overcharge deformation rate (%)	Float charge failure time (h)
Example 1-1	Lithium trifluoromethylsulfate	20.8	1125
Example 2-1	Lithium Propyl Sulfate	25.1	903
Example 2-2	lithium hexyl sulfate	23.2	917
Example 2-3	Lithium 1,1,1,3,3,3-hexafluoro-2-propylsulfate	16.1	1227
Example 2-4	2-Lithium cyanoethylsulfate	15.1	1348
Example 2-5	Lithium Ethoxyethyl Sulfate	13.5	1531
Example 2-6	Lithium Perfluorophenyl Sulfate	15.3	1279
Example 2-7	lithium allyl sulfate	13.9	1467
Example 2-8	2-(Trimethylsilyl)ethylsulfate Lithium	12.9	1206

The results show that alkyllithium sulfates with different structures can achieve basically the same effect. When lithium alkyl sulfate contains fluorine substituents, silyl groups, oxygen-containing alkyl groups, alkenyl groups or cyano groups, it can further reduce the overcharge deformation rate of the lithium ion battery and increase its floating charge failure time.

Table 3 shows the impact of fluorine and phosphorus-containing compounds on the float performance and safety of lithium-ion batteries, wherein the content of fluorine- and phosphorus-containing compounds in the electrolyte is 0.5%. Except for the parameters listed in Table 3, the settings of Examples 3-1 to 3-5 are the same as those of Example 1-1.

table 3

the	Compounds containing sulfur and oxygen double bonds	Overcharge deformation rate (%)	Float charge failure time (h)
Example 1-1	—	20.8	1125
Example 3-1	lithium difluorophosphate	15.7	1205
Example 3-2	lithium monofluorophosphate	16.3	1198
Example 3-3	Formula II-1	14.2	1325
Example 3-4	Formula II-2	13.1	1569
Example 3-5	Formula II-3	12.8	1632

The results show that when the electrolyte further includes a fluorine- and phosphorus-containing compound (at least one of lithium difluorophosphate, lithium monofluorophosphate, or a compound of formula II), the overcharge deformation rate of the lithium-ion battery can be further reduced and its Float charge failure time.

Table 4 shows the effect of the content relationship between alkyl lithium sulfate and fluorine- and phosphorus-containing compounds in the electrolyte on the float performance and safety of lithium-ion batteries. Except for the parameters listed in Table 4, the settings of Examples 4-1 to 4-8 are the same as those of Example 1-1.

Table 4

The results show that when the content b% of alkyl lithium sulfate in the electrolyte and the content c% of compounds containing fluorine and phosphorus meet 0.5≤b+c≤5 and 0.4≤b/c≤5, the lithium-ion battery can be further reduced Overcharge deformation rate and increase its floating charge failure time.

References to "embodiment", "partial embodiment", "an embodiment", "another example", "example", "specific example" or "partial example" in the entire specification mean that At least one embodiment or example in the present application includes a specific feature, structure, material or characteristic described in the embodiment or example. Thus, descriptions that appear throughout the specification such as: "in some embodiments", "in an embodiment", "in one embodiment", "in another example", "in an example In", "in a particular example" or "example", they are not necessarily referring to the same embodiment or example in this application. Furthermore, the particular features, structures, materials, or characteristics herein may be combined in any suitable manner in one or more embodiments or examples.

Although illustrative embodiments have been shown and described, those skilled in the art should understand that the foregoing embodiments are not to be construed as limitations on the present application, and that changes may be made in the embodiments without departing from the spirit, principle and scope of the application. , substitution and modification.

Claims (15)

1. 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 active material layer formed on the negative electrode current collector, wherein:

   The negative electrode active material layer includes a nonionic surfactant, and

   The electrolyte includes alkyl lithium sulfate.
2. The electrochemical device according to claim 1, wherein:

   Based on the weight of the negative electrode active material layer, the content of the nonionic surfactant is a%;

   Based on the weight of the electrolyte, the content of the alkyl lithium sulfate is b%; and

   a and b satisfy: 0.1≤a/b≤2.
3. The electrochemical device according to claim 2, wherein a ranges from 0.01 to 5.
4. The electrochemical device according to claim 2, wherein the value of b ranges from 0.01 to 5.
5. The electrochemical device according to claim 1, wherein the nonionic surfactant has a segment formed of an ethylene oxide structure.
6. The electrochemical device according to claim 5, wherein the hydrophilic-lipophilic balance value of the nonionic surfactant is in the range of 8 to 19.
7. The electrochemical device according to claim 5, wherein the nonionic surfactant comprises polyoxyethylene alkyl ether, sorbitan fatty acid ester, glycerin fatty acid ester, polyoxyethylene sorbitan At least one of fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene resin hardened castor oil, or polyoxyethylene alkylamine.
8. The electrochemical device according to claim 1, wherein the lithium alkyl sulfate comprises a compound of formula I:

   

   in:

   R is selected from the following groups that are unsubstituted or substituted by one or more halogens: C1-20 alkyl, C2-20 alkoxy, C6-12 aryl, C2-10 alkenyl, C2-10 alkynyl, One of C3-18 chain ester groups, C3-18 cyclic ester groups, C4-10 silane or C2-10 cyano-containing alkyl groups.
9. The electrochemical device according to claim 1, wherein said alkyl lithium sulfate comprises lithium methylsulfate, lithium ethylsulfate, lithium propylsulfate, lithium butylsulfate, lithium amylsulfate, lithium hexylsulfate, lithium heptylsulfate Lithium sulfate, lithium octyl sulfate, lithium isopropyl sulfate, lithium sec-butyl sulfate, lithium trifluoromethyl sulfate, lithium 2,2,2-trifluoroethyl sulfate, 2,2,3,3-tetrafluoro Lithium Propyl Sulfate, Lithium 1,1,1,3,3,3-hexafluoro-2-propyl Sulfate, Lithium Methoxyethyl Sulfate, Lithium Ethoxyethyl Sulfate, Lithium Methoxypropyl Sulfate , lithium phenyl sulfate, lithium 4-methylphenyl sulfate, lithium 4-fluorophenyl sulfate, lithium perfluorophenyl sulfate, lithium vinyl sulfate, lithium allyl sulfate, lithium propargyl sulfate, 1-oxo Lithium-1-(2-propynyloxy)propan-2-ylsulfate, lithium 2-(trimethylsilyl)ethylsulfate, lithium 2-cyanoethylsulfate or 1,3-dicyano At least one of lithium propynyl-2-ylsulfate; preferably at least one of lithium hexylsulfate, lithium trifluoromethylsulfate or lithium 2-cyanoethylsulfate.
10. The electrochemical device according to claim 1, wherein the electrolytic solution further comprises a compound containing fluorine and phosphorus, and the compound containing fluorine and phosphorus comprises at least one of lithium difluorophosphate, lithium monofluorophosphate, or a compound of formula II A sort of:

    

    Wherein R is C1-10 hydrocarbon group or C1-10 hydrocarbon group substituted by halogen.
11. The electrochemical device according to claim 10, wherein the compound of formula II comprises at least one of the following compounds:

    
12. The electrochemical device according to claim 10, wherein based on the weight of the electrolytic solution, the content of the lithium alkyl sulfate is b%, the content of the compound containing fluorine and phosphorus is c%, and b and c satisfy : 0.5≤b+c≤5 and 0.4≤b/c≤5.
13. The electrochemical device according to claim 10, wherein the content of the compound containing fluorine and phosphorus is c%, based on the weight of the electrolyte, and the value of c is in the range of 0.1 to 5.
14. The electrochemical device according to claim 13, wherein c ranges from 0.2 to 3.
15. An electronic device comprising the electrochemical device according to any one of claims 1-14.