CN115380409A - Electrochemical device and electronic device - Google Patents

Electrochemical device and electronic device Download PDF

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CN115380409A
CN115380409A CN202180027069.1A CN202180027069A CN115380409A CN 115380409 A CN115380409 A CN 115380409A CN 202180027069 A CN202180027069 A CN 202180027069A CN 115380409 A CN115380409 A CN 115380409A
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lithium
sulfate
electrochemical device
negative electrode
electrolyte
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张青文
王可飞
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Ningde Amperex Technology Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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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, the negative electrode including a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, wherein: the anode active material layer includes a nonionic surfactant, and the electrolytic solution includes lithium alkyl sulfate. The electrochemical device of the present application has improved float charge performance and safety.

Description

Electrochemical device and electronic device
Technical Field
The present application relates to the field of energy storage, in particular to an electrochemical device and an electronic device, in particular a lithium ion battery.
Background
In recent years, electrochemical devices (e.g., lithium ion batteries) have been widely used in the fields of mobile phones, tablet computers, electric vehicles, and the like as a green secondary battery having high energy density and power density. However, the electrolyte used in the conventional lithium ion battery generally includes flammable organic solvents such as ethylene carbonate, dimethyl carbonate, diethyl carbonate, etc., which are liable to be burned violently or even cause explosion of the battery when thermal runaway occurs. Therefore, the safety problem of lithium ion batteries is attracting more and more attention.
Although battery production enterprises, raw material suppliers and scientific research institutes do a lot of work around improving the performance of lithium ion batteries, the existing method still cannot effectively improve the floating charge performance of the lithium ion batteries and fundamentally control the thermal runaway of the lithium ion batteries.
In view of the above, there is a need for an electrochemical device and an electronic device having improved float charge performance and safety.
Disclosure of Invention
Embodiments of the present application solve the problems occurring in the prior art to some extent by providing an electrochemical device and an electronic device having improved float charging performance and safety.
In one aspect of the present application, there is provided an electrochemical device comprising: a positive electrode, a negative electrode, and an electrolytic solution, the negative electrode including a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, wherein: the anode active material layer includes a nonionic surfactant, and the electrolytic solution includes lithium alkyl sulfate.
According to the embodiment of the present application, the content of the nonionic surfactant is a% based on the weight of the anode active material layer; the content of the lithium alkyl sulfate is b% based on the weight of the electrolyte; and a and b satisfy: a/b is more than or equal to 0.1 and less than or equal to 2.
According to the embodiment of the application, the value range of a is 0.01 to 5.
According to the embodiment of the application, the value range of b is 0.01 to 5.
According to an embodiment of the present application, the nonionic surfactant has a segment formed by an ethylene oxide structure.
According to an embodiment of the present application, the nonionic surfactant has a hydrophilic-lipophilic balance value in the range of 8 to 19.
According to an embodiment of the present application, the nonionic surfactant includes at least one of polyoxyethylene alkyl ether, sorbitan fatty acid ester, glycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene resin hardened castor oil, or polyoxyethylene alkylamine.
According to embodiments of the present application, the lithium alkyl sulfate includes a compound of formula I:
Figure BDA0003877756630000021
wherein:
r is selected from the following groups, unsubstituted or substituted with one or more halogens: c1-20 alkyl, C2-20 alkoxy, C6-12 aryl, C2-10 alkenyl, C2-10 alkynyl, C3-18 chain ester group, C3-18 cyclic ester group, C4-10 silane or C2-10 alkyl containing cyano.
According to embodiments of the present application, the lithium alkyl sulfate includes at least one of lithium methyl sulfate, lithium ethyl sulfate, lithium propyl sulfate, lithium butyl sulfate, lithium amyl sulfate, lithium hexyl sulfate, lithium heptyl sulfate, lithium octyl 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-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, lithium 1-oxo-1- (2-propynyloxy) propan-2-yl sulfate, lithium 2- (trimethylsilyl) ethyl sulfate, lithium 2-cyanoethyl sulfate, or lithium 1,3-dicyanopropyl-2-yl sulfate; at least one of lithium hexyl sulfate, lithium trifluoromethyl sulfate, and lithium 2-cyanoethyl sulfate is preferable.
According to an embodiment of the application, the electrolyte further comprises a fluorine and phosphorus containing compound comprising at least one of lithium difluorophosphate, lithium monofluorophosphate, or a compound of formula II:
Figure BDA0003877756630000022
wherein R is a C1-10 hydrocarbon group or a halogen-substituted C1-10 hydrocarbon group.
According to embodiments of the application, the compound of formula II comprises at least one of the following compounds:
Figure BDA0003877756630000031
according to an embodiment of the present application, the content of the lithium alkyl sulfate is b%, the content of the fluorine and phosphorus containing compound is c%, and b and c satisfy: b + c is more than or equal to 0.5 and less than or equal to 5, and b/c is more than or equal to 0.4 and less than or equal to 5.
According to the embodiment of the application, the content of the compound containing fluorine and phosphorus is c% based on the weight of the electrolyte, and the value of c ranges from 0.1 to 5.
According to embodiments of the present application, c ranges from 0.2 to 3.
In another aspect of the present application, the present application provides an electronic device comprising an electrochemical device according to the present application.
The specific combination of the negative active material layer including the nonionic surfactant and the electrolyte including the lithium alkyl sulfate used herein can significantly improve the float charge performance and safety of the electrochemical device.
Additional aspects and advantages of embodiments of the present application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of the present application.
Detailed Description
Embodiments of the present application will be described in detail below. The embodiments of the present application should not be construed as limiting the present application.
The following terms used herein have the meanings indicated below, unless explicitly indicated otherwise.
In the detailed description and claims, a 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, the phrase "at least one of a and B" means a only; only B; or A and B. In another example, if 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 A, B and all of C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements. At least one of the terms has the same meaning as at least one of the terms.
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 to be a branched or cyclic hydrocarbon structure having from 3 to 20 carbon atoms. When an alkyl group having a particular carbon number is specified, all geometric isomers having that carbon number are intended to be encompassed; thus, for example, "butyl" is meant to include 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, and the like.
The term "alkenyl" refers to a monovalent unsaturated hydrocarbon group that can be straight or branched chain and has at least one and typically 1,2, or 3 carbon-carbon double bonds. Unless otherwise defined, the 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 An alkenyl group. Representative alkenyl groups include, by way of example, ethenyl, n-propenyl, isopropenyl, n-but-2-enyl, but-3-enyl, n-hex-3-enyl, and the like.
The term "alkynyl" isRefers to a monovalent unsaturated hydrocarbon group that can be straight or branched chain and has at least one and typically 1,2, or 3 carbon-carbon triple bonds. Unless otherwise defined, the alkynyl group typically contains 2 to 20 carbon atoms and includes, 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 (e.g., phenyl) or a fused ring. Fused ring systems include those that are fully unsaturated (e.g., naphthalene) as well as those that are partially unsaturated (e.g., 1,2,3,4-tetrahydronaphthalene). Unless otherwise defined, the aryl group typically contains from 6 to 26 carbon ring atoms and includes, for example, -C 6-10 And (3) an aryl group. 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 to 20 carbon atoms, a cycloalkyl group of 6 to 20 carbon atoms, a cycloalkyl group of 3 to 12 carbon atoms, a cycloalkyl group of 3 to 6 carbon atoms. For example, cycloalkyl groups can be cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. In addition, cycloalkyl groups may be optionally substituted.
The term "halogen" refers to the elements of group VIIA of the periodic Table of the elements, including fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).
Overcharge is one of the causes of thermal runaway of lithium ion batteries. When overcharge occurs, lithium metal is deposited on the negative electrode. When the negative electrode is saturated with more and more lithium, lithium dendrites are formed on the surface of the negative electrode by the excessive lithium in the form of metal lithium, and the growth of the lithium dendrites can pierce the separation film to cause internal short circuit of a battery cell. In addition, the voltage of the lithium ion battery can be continuously increased along with the overcharge, so that the decomposition voltage of the electrolyte is reached, and the electrolyte is decomposed to generate gas. The increase of the gas production can lead to the internal air pressure of the lithium ion battery to increase to exceed the valve opening pressure, so that the battery cell explosion-proof valve is opened, and potential safety hazards are generated. The method for preventing the overcharge of the lithium ion battery mainly comprises the steps of adding an external protection device and adding a novel electrolyte additive. However, the addition of external devices to prevent overcharge may increase the cost of cell fabrication, and the introduction of new electrolyte additives may lead to new side reactions.
The present application solves the above-described problems by using a combination of a negative electrode active material layer including a nonionic surfactant and an electrolytic solution including lithium alkyl sulfate. The nonionic surfactant greatly contributes to the surface flatness of the negative electrode, and can reduce the risk of lithium dendrite generation. However, when the electrochemical device is subjected to high temperature and high pressure, the non-ionic surfactant increases the float thickness of the lithium ion battery. The addition of lithium alkyl sulfate to the electrolyte can effectively improve the float charge performance of the lithium ion battery because lithium alkyl sulfate can reduce the ionic conductivity and electronic conductivity inside the negative electrode. Meanwhile, the combination of the anode active material layer including the nonionic surfactant and the electrolyte including the lithium alkyl sulfate may also significantly improve overcharge safety of the lithium ion battery.
IAnd a 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, the negative electrode active material layer containing a negative electrode active material. The anode active material layer may be one layer or a plurality of layers, and each layer of the plurality of layers may contain the same or different anode 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 electrode active material is greater than the discharge capacity of the positive electrode active material to prevent unintentional precipitation of lithium metal on the negative electrode during charging.
One of the main features 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 a segment formed by an ethylene oxide structure.
In some embodiments, the nonionic surfactant has a hydrophilic-lipophilic balance (HLB) value in the range of 8 to 19.
In some embodiments, the nonionic surfactant comprises at least one of a polyoxyethylene alkyl ether, a sorbitan fatty acid ester, a glycerol fatty acid ester, a polyoxyethylene sorbitan fatty acid ester, a polyoxyethylene sorbitol fatty acid ester, a polyoxyethylene resin hardened castor oil, or a polyoxyethylene alkylamine.
In some embodiments, the nonionic surfactant is present in an amount of a% based on the weight of the anode active material layer, and a ranges from 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 of the foregoing values. When the content of the nonionic surfactant in the anode active material layer is within the above range, the float charge performance and safety of the electrochemical device can be further improved.
As the current collector for holding the negative electrode active material, a known current collector may be used arbitrarily. Examples of the negative electrode current collector include, but are not limited to, metal materials such as aluminum, copper, nickel, stainless steel, nickel-plated steel, and the like. In some embodiments, the negative current collector is copper.
In the case where the negative electrode current collector is a metal material, the form of the negative electrode current collector may include, but is not limited to, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal film, a metal lath, a stamped metal, a foamed metal, and the like. In some embodiments, the negative electrode current collector is a metal thin film. In some embodiments, the negative current collector is a copper foil. In some embodiments, the negative electrode current collector is a rolled copper foil based on a rolling process or an electrolytic copper foil based on an electrolytic process.
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 a range consisting of any two of the above values.
The negative electrode active material is not particularly limited as long as it can reversibly store and release lithium ions. Examples of the negative electrode active material may include, but are not limited to, carbon materials such as natural graphite, artificial graphite, and the like; metals such as silicon (Si) and tin (Sn); and oxides of metal elements such as Si and Sn. The negative electrode active materials may be used alone or in combination.
The anode active material layer may further include an anode binder. The negative electrode binder may improve the binding of the negative electrode active material particles to each other and the binding of the negative electrode active material to the current collector. The kind of the negative electrode binder is not particularly limited as long as it is a material that is stable to the electrolyte solution or the solvent used in the production of the electrode. In some embodiments, the negative electrode binder comprises a resin binder. Examples of the resin binder include, but are not limited to, fluororesins, polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, and the like. When the negative electrode mix slurry is prepared using an aqueous solvent, the negative electrode binder includes, but is not limited to, carboxymethyl cellulose (CMC) or a salt thereof, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, and the like.
The negative electrode can be prepared by the following method: a negative electrode can be obtained by applying a negative electrode mixture slurry containing a negative electrode active material, a resin binder, and the like onto a negative electrode current collector, drying the slurry, and then rolling the dried slurry to form negative electrode active material layers on both surfaces of the negative electrode current collector.
II. Electrolyte solution
The electrolyte used in the electrochemical device of the present application includes an electrolyte and a solvent dissolving the electrolyte.
Another main feature of the electrochemical device of the present application is that the electrolyte includes lithium alkyl sulfate.
In some embodiments, the lithium alkyl sulfate comprises a compound of formula I:
Figure BDA0003877756630000071
wherein:
r is selected from the following groups, unsubstituted or substituted with one or more halogens: c1-20 alkyl, C2-20 alkoxy, C6-12 aryl, C2-10 alkenyl, C2-10 alkynyl, C3-18 chain ester group, C3-18 cyclic ester group, C4-10 silane or C2-10 alkyl containing cyano.
In some embodiments, the lithium alkyl sulfate comprises at least one of lithium methyl sulfate, lithium ethyl sulfate, lithium propyl sulfate, lithium butyl sulfate, lithium amyl sulfate, lithium hexyl sulfate, lithium heptyl sulfate, lithium octyl sulfate, lithium isopropyl sulfate, lithium sec-butyl sulfate, lithium trifluoromethyl sulfate, 2,2,2-lithium trifluoroethylsulfate, 2,2,3,3-lithium tetrafluoropropyl sulfate, 1,1,1,3,3,3-lithium 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, lithium 1-oxo-1- (2-propynyloxy) propan-2-yl sulfate, lithium 2- (trimethylsilyl) ethyl sulfate, lithium 2-cyanoethyl sulfate, or 1,3-dicyanopropynyl-2-yl sulfate.
In some embodiments, the lithium alkyl sulfate includes at least one of lithium hexyl sulfate, lithium trifluoromethyl sulfate, or lithium 2-cyanoethyl sulfate.
In some embodiments, the lithium alkyl sulfate is present in an amount of b%, a and b satisfying: a/b is more than or equal to 0.1 and less than or equal to 2. In some embodiments, a and b satisfy: a/b is more than or equal to 0.1 and less than or equal to 1. In some embodiments, a and b satisfy the following relationship: a/b is more than or equal to 0.2 and less than or equal to 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 of the foregoing values. When the content of the nonionic surfactant in the positive electrode active material layer and the content of the lithium alkyl sulfate in the electrolyte satisfy the above-described 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 of the foregoing values. When the content of the lithium alkylsulfate 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 further comprises a fluorine and phosphorus containing compound comprising at least one of lithium difluorophosphate, lithium monofluorophosphate, or a compound of formula II:
Figure BDA0003877756630000081
wherein R is a C1-10 hydrocarbon group or a halogen-substituted C1-10 hydrocarbon group.
In some embodiments, the compound of formula II comprises at least one of the following compounds:
Figure BDA0003877756630000082
the compound containing fluorine and phosphorus can further reduce the ionic conductivity and the electronic conductivity in the pole piece, thereby further improving the float charge performance and the safety of the electrochemical device.
In some embodiments, the lithium alkyl sulfate is present in an amount of b%, the fluorine and phosphorus containing compound is present in an amount of c%, and b and c satisfy: b + c is more than or equal to 0.5 and less than or equal to 5, and b/c is more than or equal to 0.4 and less than or equal to 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 of the foregoing values. In some embodiments, 0.5 ≦ b/c ≦ 3. In some embodiments, 1 ≦ b/c ≦ 2. When the contents of the lithium alkylsulfate and the fluorine-and phosphorus-containing compound in the electrolyte satisfy the above-described 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 of the foregoing values. When the content of the compound containing fluorine and phosphorus in the electrolyte meets the relationship, the ionic conductance and the electronic conductance in the pole piece can be further reduced, so that the float charge performance and the safety of the electrochemical device are further improved.
In some embodiments, the electrolyte further comprises any non-aqueous solvent known in the art that can act as a solvent for the electrolyte.
In some embodiments, the non-aqueous solvent includes, but is not limited to, one or more of: cyclic carbonate, chain carbonate, cyclic carboxylate, chain carboxylate, cyclic ether, chain ether, phosphorus-containing organic solvent, sulfur-containing organic solvent, and aromatic fluorine-containing solvent.
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 to 6 carbon atoms.
In some embodiments, examples of the chain carbonates can include, but are not limited to, one or more of the following: and chain carbonates such as dimethyl carbonate, methylethyl carbonate, diethyl carbonate (DEC), methyl-n-propyl carbonate, ethyl-n-propyl carbonate, and di-n-propyl carbonate. 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, 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, and the like.
In some embodiments, examples of the cyclic carboxylic acid ester may include, but are not limited to, one or more of the following: one or more of gamma-butyrolactone and gamma-valerolactone. In some embodiments, a portion of the hydrogen atoms of the cyclic carboxylic acid ester may be substituted with fluorine.
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, and the like. In some embodiments, a part of hydrogen atoms of the chain carboxylic acid ester may be substituted with fluorine. In some embodiments, examples of the fluorine-substituted chain carboxylic acid ester may include, but are not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, 2,2,2-trifluoroethyl trifluoroacetate, and the like.
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-ethoxymethoxyethane, 1,2-ethoxymethoxyethane, and the like.
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 methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphate, tris (2,2,2-trifluoroethyl) phosphate, tris (2,2,3,3,3-pentafluoropropyl) phosphate, and the like.
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, diethylsulfone, ethylmethylsulfone, methylpropylsulfone, dimethylsulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate and dibutyl sulfate. In some embodiments, a portion of the hydrogen atoms of the sulfur-containing organic solvent may be substituted with fluorine.
In some embodiments, the aromatic fluorine-containing 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 carboxylic esters, chain carboxylic esters, 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, propyl propionate, 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, gamma-butyrolactone, and combinations thereof.
In some embodiments, the electrolyte is not particularly limited, and a substance known as an electrolyte may be arbitrarily used. In the case of a lithium secondary battery, a lithium salt is generally used. Examples of the electrolyte may include, but are not limited to, liPF 6 、LiBF 4 、LiClO 4 、LiAlF 4 、LiSbF 6 、LiWF 7 Inorganic lithium salts; liWOF 5 Lithium tungstate species; 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 CF 2 CO 2 Lithium carboxylates such as 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 Lithium sulfonates such as Li; 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 1,2-perfluoroethane bis-sulfonyl imide lithium, cyclic 1,3-perfluoropropane bis-sulfonyl imide lithium, liN (CF) 3 SO 2 )(C 4 F 9 SO 2 ) Lithium imide salts; liC (FSO) 2 ) 3 、LiC(CF 3 SO 2 ) 3 、LiC(C 2 F 5 SO 2 ) 3 Lithium methide salts; lithium (malonate) borate salts such as lithium bis (malonate) borate, lithium difluoro (malonate) borate, and the like; lithium (malonate) phosphates such as lithium tris (malonate) phosphate, lithium difluorobis (malonate) phosphate, and lithium tetrafluoro (malonate) phosphate; 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 Fluorine-containing organic lithium salts; lithium oxalato borate salts such as lithium difluorooxalato borate and lithium bis (oxalato) borate; lithium oxalato phosphate salts such as lithium tetrafluorooxalato phosphate, lithium difluorobis (oxalato) phosphate, and lithium tris (oxalato) phosphate.
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 1,2-perfluoroethane bis-sulfonyl imide lithium, cyclic 1,3-perfluoropropane bis-sulfonyl imide lithium, 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 (oxalate) phosphate, which contribute to improvement in output characteristics, high-rate charge-discharge characteristics, high-temperature storage characteristics, cycle characteristics, and the like of electrochemical devices.
The content of the electrolyte is not particularly limited as long as the effects of the present application are not impaired. In some embodiments, the total molar concentration of lithium in the electrolyte is greater than 0.3mol/L, greater than 0.4mol/L, or greater than 0.5mol/L. In some embodiments, the total molar concentration of lithium in the electrolyte is less than 3mol/L, less than 2.5mol/L, or less than 2.0 mol/L. In some embodiments, the total molar concentration of lithium in the electrolyte is within a range consisting of any two of the above values. When the electrolyte concentration is within the above range, lithium as charged particles is not excessively small, and the viscosity can be made to be in an appropriate range, so that good conductivity is easily ensured.
In the case where 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 comprises a salt selected from the group consisting of a monofluorophosphate, an oxalate, and a fluorosulfonate. In some embodiments, the electrolyte comprises a lithium salt. In some embodiments, the salt selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates is present in an amount of greater than 0.01% or greater than 0.1%, based on the weight of the electrolyte. In some embodiments, the salt selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates is present in an amount of less than 20% or less than 10% by weight of the electrolyte. In some embodiments, the amount of a salt selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates is within a range consisting of any two of the foregoing values.
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 salts in addition thereto. As other salts, there may be mentioned the lithium salts exemplified hereinabove, and LiPF in some examples 6 、LiN(FSO 2 )(CF 3 SO 2 )、LiN(CF 3 SO 2 ) 2 、LiN(C 2 F 5 SO 2 ) 2 Cyclic 1,2-perfluoroethane bis-sulfonyl imide lithium, cyclic 1,3-perfluoropropane bis-sulfonyl imide lithium, 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 amount of the additional salt is greater than 0.01% or greater than 0.1% based on the weight of the electrolyte. In some embodiments, the amount of other salts is less than 20%, less than 15%, or less than 10% based on the weight of the electrolyte. In some embodiments, the amount of other salts is within a range consisting of any two of the above values. The other salt having the above content helps to balance the conductivity and viscosity of the electrolyte.
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 electrode active material layer may be one or more layers. The positive electrode active material layer includes a positive electrode active material, and each of the plurality of layers of the positive electrode active material may contain the same or different positive electrode active materials. The positive electrode active material is any material capable of reversibly intercalating and deintercalating metal ions such as lithium ions.
The kind of the positive electrode active material is not particularly limited as long as it can electrochemically occlude and release metal ions (for example, lithium ions). In some embodiments, the positive active material is a material containing lithium and at least one transition metal. Examples of the positive active material may include, but are not limited to, lithium transition metal composite oxides and lithium transition metal phosphate compounds.
In some embodiments, the transition metal in the lithium transition metal composite oxide includes V, ti, cr, mn, fe, co, ni, cu, and the like. In some embodiments, the lithium transition metal composite oxide comprises LiCoO 2 Lithium cobalt composite oxide, liNiO 2 Lithium nickel composite oxide and LiMnO 2 、LiMn 2 O 4 、Li 2 MnO 4 Lithium manganese composite oxide, liNi 1/3 Mn 1/3 Co 1/3 O 2 、LiNi 0.5 Mn 0.3 Co 0.2 O 2 And lithium nickel manganese cobalt composite oxides in which a part of transition metal atoms that are the main components of these lithium transition metal composite oxides is replaced with another element such as Na, K, B, F, al, ti, V, cr, mn, fe, co, li, ni, cu, zn, mg, ga, zr, si, nb, mo, sn, W, and the like. Examples of the lithium transition metal composite oxide 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 And the like. Examples of the combination of lithium transition metal composite oxides include, but are not limited to, liCoO 2 With LiMn 2 O 4 In which LiMn is 2 O 4 A part of Mn in (A) may be substituted with a transition metal (e.g., liNi) 0.33 Co 0.33 Mn 0.33 O 2 )，LiCoO 2 A part of Co in (b) may be substituted by a transition metal.
In some embodiments, the transition metal in the lithium-containing transition metal phosphate compound includes V, ti, cr, mn, fe, co, ni, cu, and the like. In some embodiments, the lithium-containing transition metal phosphate compound comprises LiFePO 4 、Li 3 Fe 2 (PO 4 ) 3 、LiFeP 2 O 7 Iso-phosphates, liCoPO 4 And cobalt phosphates in which a part of the transition metal atoms as the main component of the lithium transition metal phosphate compound is replaced with another element such as Al, ti, V, cr, mn, fe, co, li, ni, cu, zn, mg, ga, zr, nb, or Si.
In some embodiments, a substance having a different composition from the positive electrode active material 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, 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; carbon, and the like. By depositing a substance on 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, and the life of the electrochemical device can be improved. When the amount of the surface-adhering substance is too small, the effect cannot be sufficiently exhibited; when the amount of the surface-adhering substance is too large, the entry and exit of lithium ions are inhibited, and the electric resistance may increase. In the present application, a positive electrode active material having a composition different from that of the positive electrode active material deposited on the surface thereof 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, a block shape, a polyhedral shape, a spherical shape, an elliptical spherical shape, a plate shape, a needle shape, a columnar shape, and the like. In some embodiments, the positive active material particles include primary particles, secondary particles, or a combination thereof. In some embodiments, the primary particles may agglomerate to form secondary particles.
The kind of the positive electrode conductive material is not limited, and any known conductive material may be used. Examples of the positive electrode conductive material may include, but are not limited to, graphite such as natural graphite, artificial graphite, and the like; carbon black such as acetylene black; carbon materials such as amorphous carbon such as needle coke; a carbon nanotube; graphene, and the like. The above-mentioned positive electrode conductive materials may be used alone or in any combination.
The type of the positive electrode binder used for producing the positive electrode active material layer is not particularly limited, and in the case of the coating method, it is sufficient if it is a material that can be dissolved or dispersed in a liquid medium used for producing the electrode. Examples of the positive electrode binder may include, but are not limited to, one or more of the following: resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and cellulose nitrate; rubber-like polymers such as Styrene Butadiene Rubber (SBR), nitrile Butadiene Rubber (NBR), fluororubber, isoprene rubber, butadiene rubber, and ethylene-propylene rubber; thermoplastic elastomer polymers such as styrene-butadiene-styrene block copolymers or hydrogenated products thereof, ethylene-propylene-diene terpolymers (EPDM), styrene-ethylene-butadiene-ethylene copolymers, styrene-isoprene-styrene block copolymers or hydrogenated products thereof; syndiotactic 1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, propylene- α -olefin copolymer, and other soft resinous polymers; fluorine-based polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymer; and a polymer composition having ion conductivity of alkali metal ions (particularly lithium ions). The positive electrode binder may be used alone or in any combination thereof.
The type of solvent used for forming the positive electrode slurry is not limited as long as it can dissolve or disperse the positive electrode active material, the conductive material, the positive electrode binder, and the thickener used as needed. Examples of the solvent used for forming the positive electrode slurry may include any one of an aqueous solvent and an organic solvent. Examples of the aqueous medium may include, but are not limited to, water and a mixed medium of alcohol and water, and the like. Examples of the organic medium 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; 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; aprotic polar solvents such as hexamethylphosphoramide and dimethylsulfoxide.
Thickeners are commonly used to adjust the viscosity of the slurry. In the case of using an aqueous medium, slurrying may be performed using a thickener and a Styrene Butadiene Rubber (SBR) emulsion. The kind of the thickener is not particularly limited, and examples thereof may include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof, and the like. The above thickeners may be used alone or in any combination.
The kind of the positive electrode current collector is not particularly limited, and it may be any material known to be suitable for use as a positive electrode current collector. Examples of the positive electrode current collector may include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, tantalum, etc.; carbon cloth, carbon paper, and the like. In some embodiments, the positive current collector is a metallic material. In some embodiments, the positive current collector is aluminum.
In order to reduce the electron 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 assistant. Examples of the conductive aid may include, but are not limited to, carbon and noble metals such as gold, platinum, silver, and the like.
The positive electrode can be produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. The positive electrode using the positive electrode active material can be produced by a conventional method in which the positive electrode active material and the binder, and if necessary, the conductive material and the thickener, etc. are dry-mixed and formed into a sheet, and the obtained sheet is pressure-bonded to the positive electrode current collector; alternatively, these materials are dissolved or dispersed in a liquid medium to prepare a slurry, and the slurry is applied onto a positive electrode current collector and dried to form a positive electrode active material layer on the current collector, thereby obtaining a positive electrode.
IV, isolating film
In order to prevent short-circuiting, a separator is generally provided between the positive electrode and the negative electrode. In this case, the electrolyte of the present application is generally used by penetrating the separator.
The material and shape of the separator are not particularly limited as long as the effects of the present application are not significantly impaired. The separator may be a resin, glass fiber, inorganic substance, or the like formed of a material stable to the electrolyte of the present application. In some embodiments, the separator includes a porous sheet having excellent liquid retention properties, a nonwoven fabric-like material, or the like. Examples of materials for the resin or glass fiber separator film may include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, and the like. In some embodiments, the polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The materials of the above-mentioned separator may be used alone or in any combination.
The separator may also be a material laminated with the above materials, and examples thereof include, but are not limited to, a three-layer separator laminated in the order of polypropylene, polyethylene, polypropylene, and the like.
Examples of the material of the inorganic substance may include, but are not limited to, oxides such as alumina, silica, nitrides such as aluminum nitride, silicon nitride, and sulfates (e.g., barium sulfate, calcium sulfate, and the like). Forms of inorganics may include, but are not limited to, particulate or fibrous.
The form of the separator may be a film form, and examples thereof include, but are not limited to, a nonwoven fabric, a woven fabric, a microporous film, and the like. In the form of a thin film, the separator has a pore size of 0.01 to 1 μm and a thickness of 5 to 50 μm. In addition to the above-mentioned separate film-like separator, the following separators may be used: the separator is formed by forming a composite porous layer containing the inorganic particles on the surface of the positive electrode and/or the negative electrode using a resin-based binder, and is formed by forming porous layers on both surfaces of the positive electrode using, for example, a fluororesin as a binder and alumina particles having a particle size of 90% less than 1 μm.
The thickness of the separator is arbitrary. In some embodiments, the release film has a thickness 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 barrier film is within a range consisting of any two of the above values. When the thickness of the separator is within the above range, the insulating property and the mechanical strength can be secured, and the rate characteristic and the energy density of the electrochemical device can be secured.
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 separator has a porosity of greater than 10%, greater than 15%, or greater than 20%. In some embodiments, the separator film has a porosity of less than 60%, less than 50%, or less than 45%. In some embodiments, the porosity of the separator is within a range consisting of any two of the above values. When the porosity of the separator is within the above range, insulation and mechanical strength can be secured, and membrane resistance can be suppressed, resulting in an electrochemical device having good safety characteristics.
The average pore diameter of the separator is also arbitrary. In some embodiments, the mean pore size of the separator is less than 0.5 μm or less than 0.2 μm. In some embodiments, the separator membrane has an average pore size greater than 0.05 μm. In some embodiments, the mean pore size of the separator is within a range consisting of any two of the above values. If the average pore diameter of the separator exceeds the above range, short circuits are likely to occur. When the average pore diameter of the separation membrane is within the above range, the electrochemical device has good safety characteristics.
V, electrochemical device assembly
The electrochemical device assembly includes an electrode group, a current collecting structure, an outer case, and a protective member.
The electrode group may have any of a laminated structure in which the positive electrode and the negative electrode are laminated with the separator interposed therebetween, and a structure in which the positive electrode and the negative electrode are spirally wound with the separator interposed therebetween. In some embodiments, the electrode group has a mass occupying ratio (electrode group occupying ratio) of more than 40% or more than 50% in the battery internal volume. In some embodiments, the electrode set occupancy is less than 90% or less than 80%. In some embodiments, the electrode set occupancy is within a range consisting of any two of the values recited above. When the electrode group occupancy is within the above range, the capacity of the electrochemical device can be ensured, and the decrease in characteristics such as repeated charge and discharge performance and high-temperature storage due to the 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-described laminated structure, a structure in which the metal core portions of the respective electrode layers are bundled and welded to the terminals is suitably used. Since the internal resistance increases when the area of one electrode is increased, it is also preferable to provide 2 or more terminals in the electrode to reduce the resistance. When the electrode group has the above-described wound structure, the internal resistance can be reduced by providing 2 or more lead structures in each of the positive and negative electrodes and bundling the terminals.
The material of the outer case is not particularly limited as long as it is stable to the electrolyte used. The outer case may be made of, but not limited to, a metal such as nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, or a magnesium alloy, or a laminated film of a resin and an aluminum foil. In some embodiments, the outer case is a metal or laminated film of aluminum or aluminum alloy.
The metal-based outer case includes, but is not limited to, a hermetically sealed structure formed by welding metals to each other by laser welding, resistance welding, or ultrasonic welding; or a caulking structure formed by using the metal through a resin spacer. The outer case using the laminated film includes, but is not limited to, a sealed structure formed by thermally bonding resin layers to each other. In order to improve the sealing property, a resin different from the resin used in the laminate film may be interposed between the resin layers. When the resin layer is thermally adhered to the current collecting terminal to form a sealed structure, a resin having a polar group or a modified resin into which a polar group has been introduced may be used as the resin to be interposed, because of the bonding between the metal and the resin. The shape of the outer package is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminated shape, a button shape, a large size, and the like.
The protection element may be a Positive Temperature Coefficient (PTC) element whose resistance increases when abnormal heat radiation or an excessive current flows, a temperature fuse, a thermistor, a valve (current cutoff valve) that cuts off a current flowing through a circuit by rapidly increasing the internal pressure or internal temperature of the battery when abnormal heat radiation occurs, or the like. The protective element may be selected from elements that do not operate under normal use of high current, and may be designed so that abnormal heat release or thermal runaway does not occur even if the protective element is not present.
The electrochemical device of the present application includes any device in which an electrochemical reaction occurs, and specific examples thereof include a lithium metal secondary battery or a lithium ion secondary battery.
The present application further provides an electronic device comprising an electrochemical device according to the present application.
The use of the electrochemical device of the present application is not particularly limited, and it can be used for any electronic device known in the art. In some embodiments, the electrochemical device of the present application can be used in, but is not limited to, notebook computers, pen-input computers, mobile computers, electronic book players, cellular phones, portable facsimile machines, portable copiers, portable printers, headphones, video recorders, liquid crystal televisions, portable cleaners, portable CDs, mini-discs, transceivers, electronic organizers, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large batteries, lithium ion capacitors, and the like.
Taking a lithium ion battery as an example and describing the preparation of the lithium ion battery with reference to specific examples, those skilled in the art will understand that the preparation method described in the present application is only an example, and any other suitable preparation method is within the scope of the present application.
Examples
1. Preparation of lithium ion battery
1. Preparation of the negative electrode
Mixing the artificial graphite, the styrene-butadiene rubber and the sodium carboxymethylcellulose with deionized water according to the mass ratio of 96% to 2%, adding a nonionic surfactant according to needs, and uniformly stirring to obtain the cathode slurry. And coating the negative electrode slurry on a copper foil with the thickness of 9 mu m, drying, cold pressing, cutting into pieces, and welding a tab to obtain the negative electrode.
2. Preparation of the Positive electrode
Mixing lithium cobaltate, super-P and polyvinylidene fluoride with N-methylpyrrolidone (NMP) according to the mass ratio of 97. And coating the anode slurry on an aluminum foil with the thickness of 12 mu m, drying, cold pressing, cutting into pieces, and welding a tab to obtain the anode.
3. Preparation of the electrolyte
EC, PC and DEC (1 in weight ratio 1 6 Mixing uniformly to form a basic electrolyte, wherein LiPF 6 The concentration of (2) was 12.5%. Additives with different contents are added into the basic electrolyte to obtain electrolytes of different examples and comparative examples.
Abbreviations for components in the electrolyte and their names are shown in the following table:
name of Material Abbreviations Name of Material Abbreviations
Ethylene carbonate EC Propylene carbonate PC
Carbonic acid diethyl ester DEC Compounds of formula II-1 Formula II-1
Compounds of formula II-2 Formula II-2 Compounds of formula II-3 Formula II-3
4. Preparation of the separator
The polyethylene porous polymer film is used as a separation film.
5. Preparation of lithium ion battery
The obtained positive electrode, separator and negative electrode were wound in order and placed in an outer packaging foil, leaving a liquid inlet. And (4) pouring electrolyte from the electrolyte injection port, packaging, and performing formation, capacity and other processes to obtain the lithium ion battery.
2. Test method
1. Method for testing over-charge deformation rate of lithium ion battery
Standing the lithium ion battery at 25 deg.C for 30 min, then constant-current charging to 4.7V at 0.5C rate, constant-voltage charging to 0.05C at 4.7V, standing for 60 min, and measuring the thickness T of the lithium ion battery 1 . Then charging the lithium ion battery with a constant current of 0.1C multiplying power for 60 minutes, standing for 30 minutes, repeating the step for 5 times to enable the lithium ion battery to reach a state of charge (SOC) of 150%, and measuring lithium ionsThickness T of battery 2 . The overcharge deformation rate of the lithium ion battery was calculated by the following formula:
over-inflation deformation rate = [ (T) 2 -T 1 )/T 1 ]×100％。
2. Method for testing floating charge performance of lithium ion battery
The lithium ion battery was charged at 25 ℃ to 4.7V at a constant current of 0.5C and then to 0.05C at a constant voltage of 4.7V. The lithium ion cell was then placed in a 50 ℃ oven and charged at 4.7V with a constant voltage (cut-off current of 20 mA) and the thickness of the lithium ion cell was monitored for changes. When the thickness of the lithium ion battery increases by more than 20%, based on the thickness of the lithium ion battery at the initial 50% state of charge (SOC), it is said to be dead. The time to failure of the lithium ion battery at 50 ℃ after float charging was recorded in hours (h) as a statistical unit.
3. Test results
Table 1 shows the effect of the negative electrode active material layer and the electrolyte on the float charge performance and safety of the lithium ion battery, wherein the nonionic surfactant in the negative electrode active material layer is polyoxyethylene alkyl ether, and the lithium alkyl sulfate in the electrolyte is lithium trifluoromethyl sulfate.
TABLE 1
Figure BDA0003877756630000191
As shown in comparative example 1-1, although the electrolyte included lithium alkyl sulfate, the negative electrode active material layer included no nonionic surfactant, and the lithium ion battery had a high overcharge deformation rate and a short float charge failure time. As shown in comparative examples 1 to 2, although the anode active material layer included the nonionic surfactant, the electrolyte included no lithium alkyl sulfate, and the lithium ion battery had a high overcharge deformation rate and a short float charge failure time.
As shown in examples 1-1 to 1-15, when the anode active material layer includes the nonionic surfactant and the electrolytic solution includes the lithium alkylsulfate, the overcharge deformation rate of the lithium ion battery can be significantly reduced and the float charge failure time thereof can be significantly increased.
In addition, when the content a% of the nonionic surfactant in the negative electrode active material layer and the content b% of the lithium alkyl sulfate in the electrolyte meet the condition that a/b is more than or equal to 0.1 and less than or equal to 2, the overcharge deformation rate of the lithium ion battery can be further reduced, and the float charge failure time of the lithium ion battery can be prolonged.
When the content of the nonionic surfactant in the negative 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 float charge failure time of the lithium ion battery can be prolonged.
When the content of the lithium alkyl sulfate in the electrolyte is in the range of 0.01-5%, the overcharge deformation rate of the lithium ion battery can be further reduced, and the float charge failure time of the lithium ion battery can be prolonged.
Table 2 shows the effect of 1% content of lithium alkyl sulfate compounds of different structures on the float charge performance and safety of lithium ion batteries. Examples 2-1 to 2-8 were set up identically to example 1-1, except for the parameters listed in Table 2.
TABLE 2
Lithium alkyl sulfates Overcharge deformation Rate (%) Float charge failure time (h)
Example 1-1 Lithium trifluoromethyl sulfate 20.8 1125
Example 2-1 Lithium propyl sulfate 25.1 903
Examples 2 to 2 Lithium hexyl sulfate 23.2 917
Examples 2 to 3 1,1,1,3,3,3-hexafluoro-2-propyllithium sulfate 16.1 1227
Examples 2 to 4 2-cyanoethyl lithium sulfate 15.1 1348
Examples 2 to 5 Ethoxy ethyl lithium sulfate 13.5 1531
Examples 2 to 6 Lithium perfluorophenyl sulfate 15.3 1279
Examples 2 to 7 Allyl lithium sulfate 13.9 1467
Examples 2 to 8 2- (trimethylsilane)Yl) lithium ethylsulfate 12.9 1206
The results show that lithium alkyl sulfates of different structures can achieve substantially equivalent results. When the lithium alkyl sulfate contains a fluorine substituent, a silane group, an oxygen-containing alkyl group, an alkenyl group or a cyano group, the overcharge deformation rate of the lithium ion battery can be further reduced, and the float charge failure time of the lithium ion battery can be prolonged.
Table 3 shows the effect of fluorine and phosphorus containing compounds on the float charge performance and safety of the lithium ion battery, wherein the content of the fluorine and phosphorus containing compounds in the electrolyte was 0.5%. Examples 3-1 to 3-5 were set up identically to example 1-1, except for the parameters listed in Table 3.
TABLE 3
Compound containing sulfur-oxygen double bond Overcharge deformation Rate (%) Float charge failure time (h)
Examples 1 to 1 — 20.8 1125
Example 3-1 Lithium difluorophosphate 15.7 1205
Examples 3 to 2 Lithium monofluorophosphate 16.3 1198
Examples 3 to 3 Formula II-1 14.2 1325
Examples 3 to 4 Formula II-2 13.1 1569
Examples 3 to 5 Formula II-3 12.8 1632
The results show that when the electrolyte further comprises a compound containing fluorine and phosphorus (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 the float charge failure time thereof can be improved.
Table 4 shows the effect of the content relationship of lithium alkyl sulfate and fluorine and phosphorus containing compounds in the electrolyte on the float charge performance and safety of the lithium ion battery. Examples 4-1 to 4-8 were set up identically to example 1-1, except for the parameters listed in Table 4.
TABLE 4
Figure BDA0003877756630000211
The result shows that when the content b% of the lithium alkyl sulfate and the content c% of the compound containing fluorine and phosphorus in the electrolyte meet the conditions that b + c is more than or equal to 0.5 and less than or equal to 5 and b/c is more than or equal to 0.4 and less than or equal to 5, the over-charge deformation rate of the lithium ion battery can be further reduced and the float charge failure time of the lithium ion battery can be prolonged.
Reference throughout this specification to "an embodiment," "some embodiments," "one embodiment," "another example," "an example," "a specific example," or "some examples" means that at least one embodiment or example in this application includes a particular feature, structure, material, or characteristic described in the embodiment or example. Thus, throughout the specification, descriptions appear, for example: "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in one example," "in a particular example," or "an example," which do not necessarily refer to the same embodiment or example in this application. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.
Although illustrative embodiments have been illustrated and described, it will be appreciated by those skilled in the art that the above embodiments are not to be construed as limiting the application and that changes, substitutions and alterations can be made to the embodiments without departing from the spirit, principles and scope of the application.

Claims (15)

1. An electrochemical device, comprising: a positive electrode, a negative electrode, and an electrolyte, the negative electrode including a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, wherein:
the anode active material layer includes a nonionic surfactant, and
the electrolyte includes lithium alkyl sulfate.
2. The electrochemical device of claim 1, wherein:
the content of the nonionic surfactant is a% based on the weight of the anode active material layer;
the content of the lithium alkyl sulfate is b% based on the weight of the electrolyte; and is provided with
a and b satisfy: a/b is more than or equal to 0.1 and less than or equal to 2.
3. The electrochemical device of claim 2, wherein a ranges from 0.01 to 5.
4. The electrochemical device of claim 2, wherein 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 nonionic surfactant has a hydrophilic-lipophilic balance value in the range of 8 to 19.
7. The electrochemical device according to claim 5, wherein the nonionic surfactant includes at least one of polyoxyethylene alkyl ether, sorbitan fatty acid ester, glycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene resin hardened castor oil, or polyoxyethylene alkylamine.
8. The electrochemical device of claim 1, wherein the lithium alkyl sulfate comprises a compound of formula I:
Figure FDA0003877756620000021
wherein:
r is selected from the following groups, unsubstituted or substituted with one or more halogens: c1-20 alkyl, C2-20 alkoxy, C6-12 aryl, C2-10 alkenyl, C2-10 alkynyl, C3-18 chain ester group, C3-18 cyclic ester group, C4-10 silane or C2-10 alkyl containing cyano.
9. The electrochemical device of claim 1, wherein the lithium alkyl sulfate comprises at least one of lithium methyl sulfate, lithium ethyl sulfate, lithium propyl sulfate, lithium butyl sulfate, lithium pentyl sulfate, lithium hexyl sulfate, lithium heptyl sulfate, lithium octyl 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-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, propargyl sulfate, lithium 1-oxo-1- (2-propynyloxy) propan-2-yl sulfate, lithium 2- (trimethylsilyl) ethyl sulfate, lithium 2-cyanoethyl sulfate, or lithium 1,3-dicyano-2-yl sulfate; at least one of lithium hexyl sulfate, lithium trifluoromethyl sulfate, and lithium 2-cyanoethyl sulfate is preferable.
10. The electrochemical device of claim 1, wherein the electrolyte further comprises a fluorine and phosphorus containing compound comprising at least one of lithium difluorophosphate, lithium monofluorophosphate, or a compound of formula II:
Figure FDA0003877756620000022
wherein R is a C1-10 hydrocarbon group or a halogen-substituted C1-10 hydrocarbon group.
11. The electrochemical device of claim 10, wherein the compound of formula II comprises at least one of the following compounds:
Figure FDA0003877756620000031
12. the electrochemical device according to claim 10, wherein the content of the lithium alkyl sulfate is b%, the content of the fluorine and phosphorus containing compound is c%, and b and c satisfy: b + c is more than or equal to 0.5 and less than or equal to 5, and b/c is more than or equal to 0.4 and less than or equal to 5.
13. The electrochemical device according to claim 10, wherein the content of the fluorine and phosphorus containing compound is c% based on the weight of the electrolyte, and c has a value ranging from 0.1 to 5.
14. The electrochemical device of claim 13, wherein c has a value in the range of 0.2 to 3.
15. An electronic device comprising the electrochemical device of any one of claims 1-14.
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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104584309A (en) * 2012-08-09 2015-04-29 三菱化学株式会社 Nonaqueous electrolyte solution and nonaqueous electrolyte secondary battery using same
CN105074996A (en) * 2013-04-01 2015-11-18 宇部兴产株式会社 Nonaqueous electrolyte solution and electricity storage device using same
CN111129592A (en) * 2019-12-25 2020-05-08 宁德新能源科技有限公司 Electrochemical device and electronic device comprising same
CN112151749A (en) * 2020-10-15 2020-12-29 宁德新能源科技有限公司 Electrochemical device and electronic device
CN112151752A (en) * 2020-10-15 2020-12-29 宁德新能源科技有限公司 Electrochemical device and electronic device
WO2021128094A1 (en) * 2019-12-25 2021-07-01 宁德新能源科技有限公司 Electrochemical device and electronic device comprising same
KR20210112389A (en) * 2020-10-15 2021-09-14 닝더 엠프렉스 테크놀로지 리미티드 Electrochemical devices and electronics

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107394269B (en) * 2016-05-17 2020-10-02 宁德新能源科技有限公司 Electrolyte and lithium ion battery
CN111129594B (en) * 2019-12-25 2023-09-01 宁德新能源科技有限公司 Electrochemical device and electronic device comprising same
CN111740163B (en) * 2020-03-23 2021-11-05 杉杉新材料（衢州）有限公司 High-voltage lithium ion battery electrolyte and lithium ion battery using same

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104584309A (en) * 2012-08-09 2015-04-29 三菱化学株式会社 Nonaqueous electrolyte solution and nonaqueous electrolyte secondary battery using same
CN105074996A (en) * 2013-04-01 2015-11-18 宇部兴产株式会社 Nonaqueous electrolyte solution and electricity storage device using same
CN111129592A (en) * 2019-12-25 2020-05-08 宁德新能源科技有限公司 Electrochemical device and electronic device comprising same
WO2021128094A1 (en) * 2019-12-25 2021-07-01 宁德新能源科技有限公司 Electrochemical device and electronic device comprising same
CN112151749A (en) * 2020-10-15 2020-12-29 宁德新能源科技有限公司 Electrochemical device and electronic device
CN112151752A (en) * 2020-10-15 2020-12-29 宁德新能源科技有限公司 Electrochemical device and electronic device
KR20210112389A (en) * 2020-10-15 2021-09-14 닝더 엠프렉스 테크놀로지 리미티드 Electrochemical devices and electronics

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