CN116404265B - Electrochemical device and electronic device - Google Patents

Electrochemical device and electronic device Download PDF

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Publication number
CN116404265B
CN116404265B CN202310674932.3A CN202310674932A CN116404265B CN 116404265 B CN116404265 B CN 116404265B CN 202310674932 A CN202310674932 A CN 202310674932A CN 116404265 B CN116404265 B CN 116404265B
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positive electrode
lithium
carbonate
negative electrode
electrochemical device
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CN116404265A (en
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徐小明
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Ningde Amperex Technology Ltd
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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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • 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
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • 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

Abstract

The application provides an electrochemical device and an electronic device, wherein the electrochemical device comprises an anode plate, a separation film, a cathode plate and electrolyte, and the separation film is arranged between the anode plate and the cathode plate; the reversible capacity of the positive pole piece is P, and the reversible capacity of the negative pole piece is N, wherein N/P is more than or equal to 0.95 and less than or equal to 1.0; the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode material layer comprises a positive electrode active material, and the positive electrode active material comprises lithium element; the electrolyte comprises fluoroethylene carbonate and lithium bis (fluorosulfonyl) imide, wherein the mass percentage content a of the fluoroethylene carbonate is 2-10% and the mass percentage content b of the lithium bis (fluorosulfonyl) imide is 1-10% based on the mass of the electrolyte; the surface of the isolating film adjacent to the negative electrode plate is provided with a dielectric coating, and the dielectric coating comprises a dielectric coating material. The electrochemical device provided by the application can improve the energy density and the cycle performance.

Description

Electrochemical device and electronic device
Technical Field
The present application relates to the field of electrochemical technology, and in particular, to an electrochemical device and an electronic device.
Background
Further enhancement of energy density of electrochemical devices, such as lithium ion batteries, is significant, and for conventional graphite negative electrode systems, lithium deposition by the surface of the negative electrode has proven to be an effective method of enhancing energy density of lithium ion batteries. However, in general, lithium will preferentially nucleate and grow on certain specific sites due to non-uniform electric field on the surface of the negative electrode, so that deposition of metallic lithium on the surface of the negative electrode will occur in the form of lithium dendrites, which will cause it to gradually form "dead lithium", thereby causing rapid capacity decay; on the other hand, the occurrence of lithium dendrites may puncture the separator to form an internal short circuit in the lithium ion battery, resulting in safety risks. The above problems severely limit the improvement of the energy density of the lithium ion battery and influence the cycle performance, so how to realize the uniform deposition of lithium on the negative electrode on the basis of the traditional lithium ion battery system, thereby improving the energy density and the cycle performance of the electrochemical device becomes a technical problem to be solved.
Disclosure of Invention
An object of an embodiment of the present application is to provide an electrochemical device having a high energy density and good cycle performance, and an electronic device. The specific technical scheme is as follows:
in the context of the present application, the present application is explained using a lithium ion battery as an example of an electrochemical device, but the electrochemical device of the present application is not limited to a lithium ion battery.
The first aspect of the present application provides an electrochemical device comprising a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte, the separator being disposed between the positive electrode sheet and the negative electrode sheet; the reversible capacity of the positive pole piece is P, and the reversible capacity of the negative pole piece is N, wherein N/P is more than or equal to 0.95 and less than or equal to 1.0; the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode material layer comprises a positive electrode active material, and the positive electrode active material comprises lithium element; the electrolyte comprises fluoroethylene carbonate (FEC) and lithium bis (fluorosulfonyl) imide (LiFSI), wherein the mass percentage content a of the fluoroethylene carbonate is 2-10% and the mass percentage content b of the lithium bis (fluorosulfonyl) imide is 1-10% based on the mass of the electrolyte; the surface of the isolating film adjacent to the negative electrode plate is provided with a dielectric coating, the dielectric coating comprises a dielectric coating material, and the dielectric coating material comprises at least one of polyacrylonitrile, polyvinylidene fluoride, polyethylene terephthalate, polytetrafluoroethylene, polyamide or polysiloxane. Through regulating and controlling the value of N/P, the mass percent content of FEC and LiWSI, and arranging a dielectric coating on the surface of the isolating film adjacent to the negative electrode plate, and selecting the dielectric layer materials, a synergistic effect is formed among the positive electrode plate, the negative electrode plate, the isolating film and the electrolyte, the uniformity of deposition of lithium ions on the surface of the negative electrode plate can be improved, and the generation of lithium dendrites and dead lithium is reduced, so that the obtained electrochemical device has higher energy density and good cycle performance.
In some embodiments of the application, 4% or less a or less than 6%.
In some embodiments of the application, 6% to 10% b.
In some embodiments of the application, the dielectric coating has a thickness of 1 μm to 2 μm. By regulating the thickness of the dielectric coating within the above range, the obtained electrochemical device has higher energy density and good cycle performance.
In some embodiments of the application, the positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium cobalt oxide, or lithium iron phosphate. By selecting the positive electrode active material, the value of N/P can be in the range, the deposition uniformity of lithium ions on the surface of the negative electrode plate can be improved, and the generation of lithium dendrites and dead lithium is reduced, so that the obtained electrochemical device has higher energy density and good cycle performance.
In some embodiments of the present application, the negative electrode tab includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, the negative electrode material layer including a negative electrode active material including at least one of artificial graphite, natural graphite, hard carbon, silicon oxygen, or silicon carbon. By selecting the anode active material, the value of N/P is in the range, the deposition uniformity of lithium ions on the surface of the anode piece can be improved, and the generation of lithium dendrites and dead lithium is reduced, so that the obtained electrochemical device has higher energy density and good cycle performance.
In some embodiments of the application, the electrolyte includes a carbonate compound including dimethyl carbonate and a lithium saltAt least one of methyl ethyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, dipropyl carbonate, methyl propyl carbonate, pentafluoropropyl ethylene carbonate, methyl trifluoroethyl carbonate, trifluoromethyl ethylene carbonate, or bis (2, 2-trifluoroethyl) carbonate; the lithium salt comprises LiPF 6 、LiBF 4 、LiClO 4 、LiB(C 6 H 5 ) 4 、LiCH 3 SO 3 、LiCF 3 SO 3 、LiN(SO 2 CF 3 ) 2 、LiC(SO 2 CF 3 ) 3 Or Li (lithium) 2 SiF 6 At least one of (a) and (b); the carbonate compound has a mass percentage d of 75 to 90% and the lithium salt has a mass percentage e of 7 to 15% based on the mass of the electrolyte. The electrolyte contains the carbonate compound and the lithium salt, the mass percentage content of the carbonate compound and the lithium salt is regulated and controlled within the range, and the formed electrolyte system has proper viscosity, ionic conductivity and desolvation property, is favorable for the transmission of lithium ions and the deposition of the lithium ions on the surface of a negative electrode plate, can improve the uniformity of the deposition of the lithium ions on the surface of the negative electrode plate, and reduces the generation of lithium dendrites and dead lithium, so that the obtained electrochemical device has higher energy density and good cycle performance.
A second aspect of the present application provides an electronic device comprising an electrochemical device according to any one of the preceding embodiments. Therefore, the electronic device provided by the application has good service performance.
The embodiment of the application has the beneficial effects that:
the application provides an electrochemical device and an electronic device, wherein the electrochemical device comprises an anode plate, a separation film, a cathode plate and electrolyte, and the separation film is arranged between the anode plate and the cathode plate; the reversible capacity of the positive pole piece is P, and the reversible capacity of the negative pole piece is N, wherein N/P is more than or equal to 0.95 and less than or equal to 1.0; the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode material layer comprises a positive electrode active material, and the positive electrode active material comprises lithium element; the electrolyte comprises fluoroethylene carbonate and lithium bis (fluorosulfonyl) imide, wherein the mass percentage content a of the fluoroethylene carbonate is 2-10% and the mass percentage content b of the lithium bis (fluorosulfonyl) imide is 1-10% based on the mass of the electrolyte; the surface of the isolating film adjacent to the negative electrode plate is provided with a dielectric coating, the dielectric coating comprises a dielectric coating material, and the dielectric coating material comprises at least one of polyacrylonitrile, polyvinylidene fluoride, polyethylene terephthalate, polytetrafluoroethylene, polyamide or polysiloxane. The electrochemical device provided by the application realizes uniform deposition of lithium on the surface of the negative electrode plate, thereby improving the energy density and the cycle performance of the electrochemical device.
Of course, it is not necessary for any one product or method of practicing the application to achieve all of the advantages set forth above at the same time.
Drawings
In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the application, and other embodiments may be obtained according to these drawings to those skilled in the art.
FIG. 1 is an electron micrograph of the negative electrode sheet of example 1 at 500 Xmagnification;
FIG. 2 is an electron micrograph of the negative electrode sheet of example 1 at 5000 Xmagnification;
FIG. 3 is an electron micrograph of the negative electrode tab of comparative example 2 at 500 Xmagnification;
FIG. 4 is an electron micrograph of the negative electrode plate of comparative example 2 at 5000 Xmagnification;
FIG. 5 is an electron micrograph of the negative electrode tab of comparative example 3 at 500 Xmagnification;
FIG. 6 is an electron micrograph of the negative electrode plate of comparative example 3 at 5000 Xmagnification;
fig. 7 is a cycle performance test chart of the lithium ion batteries in example 1 and comparative example 1;
fig. 8 is a cycle performance test chart of the lithium ion batteries in example 1 and comparative example 4.
Detailed Description
The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. Based on the embodiments of the present application, all other embodiments obtained by the person skilled in the art based on the present application are included in the scope of protection of the present application.
In the specific embodiment of the present application, the present application is explained by taking a lithium ion battery as an example of an electrochemical device, but the electrochemical device of the present application is not limited to a lithium ion battery.
The first aspect of the present application provides an electrochemical device comprising a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte, the separator being disposed between the positive electrode sheet and the negative electrode sheet; the reversible capacity of the positive pole piece is P, and the reversible capacity of the negative pole piece is N, wherein N/P is more than or equal to 0.95 and less than or equal to 1.0. For example, the value of N/P may be 0.95, 0.96, 0.97, 0.98, 0.99, 1.0 or a range of any two values therebetween. The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector, the positive electrode material layer including a positive electrode active material including lithium element. The electrolyte comprises fluoroethylene carbonate (FEC) and lithium bis (fluorosulfonyl) imide (LiFSI), wherein the mass percentage content a of the fluoroethylene carbonate is 2-10% based on the mass of the electrolyte; in some embodiments, 4% or less a 6% or less; the mass percentage of lithium bis (fluorosulfonyl) imide, b, is 1% to 10%, and in some embodiments, 6% b 10% b. For example, the mass percent a of fluoroethylene carbonate may be 2%, 4%, 5%, 6%, 8%, 10% or a range of any two values therebetween, and the mass percent b of lithium bisfluorosulfonyl imide may be 1%, 3%, 5%, 7%, 9%, 10% or a range of any two values therebetween. The surface of the isolating film adjacent to the negative electrode plate is provided with a dielectric coating, the dielectric coating comprises a dielectric coating material, and the dielectric coating material comprises at least one of polyacrylonitrile, polyvinylidene fluoride, polyethylene terephthalate, polytetrafluoroethylene, polyamide or polysiloxane; in some embodiments, the dielectric coating material comprises at least one of polyacrylonitrile or polyvinylidene fluoride.
The electrochemical device provided by the application has the advantages that the N/P value is in the range, the deposition of lithium ions on the surface of the negative electrode plate can be realized, the improvement of energy density is realized, and the FEC and LiFSI in the electrolyte are beneficial to promoting the transverse deposition of lithium ions on the surface of the negative electrode plate and reducing the formation of lithium dendrites; meanwhile, the dielectric coating is arranged on the surface of the isolating film adjacent to the negative electrode plate, so that the uniformity of an electric field is improved, the uniformity of deposition of lithium ions on the surface of the negative electrode plate is further improved, generation of lithium dendrites is avoided, the content of dead lithium is reduced, and the cycle performance of an electrochemical device is improved. When the value of N/P is too small, for example, less than 0.95, the precipitation amount of lithium ions is too large, lithium dendrites are easily formed during deposition to form "dead lithium", which affects the cycle and safety performance of the electrochemical device; when the value of N/P is too large, for example, greater than 1.0, lithium ions are not easily precipitated, affecting the energy density of the electrochemical device. When the mass percentage of the FEC and/or LiFSI in the electrolyte is too low, for example, a is less than 2% or b is less than 1%, lithium ions are deposited on the surface of the negative electrode plate to easily form lithium dendrites so as to form dead lithium, so that the cycle performance of the electrochemical device is reduced; when the FEC and/or LiFSI is excessively high in mass percentage in the electrolyte, for example, a is greater than 10% and/or b is greater than 10%, the viscosity of the electrolyte increases, the ionic conductivity decreases, the impedance of the electrochemical device increases, and even deposition of lithium ions is adversely affected, thereby affecting the energy density and cycle performance of the electrochemical device. Therefore, according to the electrochemical device provided by the application, the N/P value, the FEC and the LiFSI in percentage by mass are regulated, the dielectric coating is arranged on the surface of the isolating film adjacent to the negative electrode plate, and the dielectric layer material is selected, so that a synergistic effect is formed among the positive electrode plate, the negative electrode plate, the isolating film and the electrolyte, the deposition uniformity of lithium ions on the surface of the negative electrode plate can be improved, and the generation of lithium dendrites and dead lithium is reduced, so that the obtained electrochemical device has higher energy density and good cycle performance.
In the present application, the value of N/P can be changed by selecting different kinds of positive electrode active materials and/or negative electrode active materials, and the coating weight of the positive electrode active materials and/or negative electrode active materials can be controlled to change the value of N/P. For example, when the positive electrode active material and the negative electrode active material are determined, the coating weight of the negative electrode active material increases, or the coating weight of the positive electrode active material decreases, and the value of N/P increases; when the coating weight of the anode active material is reduced, or the coating weight of the cathode active material is increased, the value of N/P is reduced.
In the present application, the above-mentioned "positive electrode material layer provided on at least one surface of the positive electrode current collector" means that the positive electrode material layer may be provided on one surface of the positive electrode current collector in the thickness direction thereof, or may be provided on both surfaces of the positive electrode current collector in the thickness direction thereof. The "surface" here may be the entire area of the surface of the positive electrode current collector or may be a partial area of the surface of the positive electrode current collector, and the present application is not particularly limited as long as the object of the present application can be achieved. The thickness of the positive electrode material layer is not particularly limited as long as the object of the present application can be achieved, for example, the thickness of the positive electrode material layer is 30 μm to 120 μm. The positive electrode current collector of the present application is not particularly limited as long as the object of the present application can be achieved, and may include, for example, aluminum foil, aluminum alloy foil, or a composite current collector (e.g., an aluminum-carbon composite current collector), or the like. The thickness of the positive electrode current collector is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5 μm to 12 μm.
In the present application, "dead lithium" refers to lithium in an electrochemical device, which cannot participate in charge and discharge of the electrochemical device after formation of lithium dendrites.
The present application is not particularly limited in the molecular weight of the above dielectric coating material as long as the object of the present application can be achieved, and the weight average molecular weight of the dielectric coating material may be 10000 to 200000, for example.
In some embodiments of the application, the thickness T of the dielectric coating is 1 μm to 2 μm. For example, the thickness of the dielectric coating may be 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.8 μm, 2 μm. The dielectric coating layer has the thickness, which shows that the influence on the energy density of the electrochemical device is small, so that the electrochemical device obtained by regulating the thickness of the dielectric coating layer within the range has higher energy density and good cycle performance.
In some embodiments of the present application, the positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium cobalt oxide, or lithium iron phosphate. By selecting the positive electrode active material, the value of N/P is in the range, the deposition uniformity of lithium ions on the surface of the negative electrode plate can be improved, and the generation of lithium dendrites and dead lithium is reduced, so that the obtained electrochemical device has higher energy density and good cycle performance. The nickel cobalt lithium manganate may include, but is not limited to, liNi 0.8 Co 0.1 Mn 0.1 O 2 （NCM811）、LiNi 0.6 Co 0.2 Mn 0.2 O 2 （NCM622）、LiNi 0.5 Co 0.3 Mn 0.2 O 2 (NCM 532). The coating weight of the positive electrode active material is not limited in the present application, and may be selected according to the actual situation as long as the object of the present application can be achieved.
In some embodiments of the present application, the negative electrode tab includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, the negative electrode material layer including a negative electrode active material including at least one of artificial graphite, natural graphite, hard carbon, silicon oxygen, or silicon carbon. By selecting the anode active material, the value of N/P is in the range, the deposition uniformity of lithium ions on the surface of the anode piece can be improved, and the generation of lithium dendrites and dead lithium is reduced, so that the obtained electrochemical device has higher energy density and good cycle performance. The coating weight of the negative electrode active material is not limited in the present application, and may be selected according to the actual situation as long as the object of the present application can be achieved.
In the present application, the above-mentioned "anode material layer provided on at least one surface of the anode current collector" means that the anode material layer may be provided on one surface of the anode current collector in the thickness direction thereof, or may be provided on both surfaces of the anode current collector in the thickness direction thereof. The "surface" here may be the entire area of the surface of the negative electrode current collector or may be a partial area of the surface of the negative electrode current collector, and the present application is not particularly limited as long as the object of the present application can be achieved.
In some embodiments of the application, the electrolyte comprises a carbonate compound and a lithium salt, the carbonate compound comprising at least one of dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, dipropyl carbonate, methylpropyl carbonate, pentafluoropropyl ethylene carbonate, methyltrifluoroethyl carbonate, ethylmethyl trifluorocarbonate, ethylene trifluoromethyl carbonate, or bis (2, 2-trifluoroethyl) carbonate; the lithium salt comprises LiPF 6 、LiBF 4 、LiClO 4 、LiB(C 6 H 5 ) 4 、LiCH 3 SO 3 、LiCF 3 SO 3 、LiN(SO 2 CF 3 ) 2 、LiC(SO 2 CF 3 ) 3 Or Li (lithium) 2 SiF 6 At least one of (a) and (b); the mass percentage d of the carbonate compound is 75 to 90% and the mass percentage e of the lithium salt is 7 to 15% based on the mass of the electrolyte. For example, the carbonate compound may be present in an amount of 75%, 78%, 80%, 82%, 85%, 88%, 90% by mass or in a range of any two values therebetween, and the lithium salt may be present in an amount of 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% by mass or in a range of any two values therebetween. The electrolyte contains the carbonate compound and the lithium salt, the mass percentage content of the carbonate compound and the lithium salt is regulated and controlled within the range, and the formed electrolyte system has proper viscosity, ionic conductivity and desolvation property, is favorable for the transmission of lithium ions and the deposition of the lithium ions on the surface of a negative electrode plate, can improve the uniformity of the deposition of the lithium ions on the surface of the negative electrode plate, and reduces the generation of lithium dendrites and dead lithium, so that the obtained electrochemical device has higher energy density and good cycle performance.
In the present application, the positive electrode material layer may further include a conductive agent and a binder, and the present application is not particularly limited in kind as long as the object of the present application can be achieved. For example, the conductive agent may include, but is not limited to, at least one of conductive carbon black (Super P), carbon Nanotubes (CNTs), carbon fiber, crystalline flake graphite, ketjen black, graphene, a metallic material, or a conductive polymer. The carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and/or multi-walled carbon nanotubes. The carbon fibers may include, but are not limited to, vapor Grown Carbon Fibers (VGCF) and/or nano carbon fibers. The above-mentioned metal material may include, but is not limited to, metal powder and/or metal fiber, and in particular, the metal may include, but is not limited to, at least one of copper, nickel, aluminum or silver. The conductive polymer may include, but is not limited to, at least one of a polyphenylene derivative, polyaniline, polythiophene, polyacetylene, or polypyrrole. For example, the binder may include, but is not limited to, at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamideimide, styrene butadiene rubber, or polyvinylidene fluoride (PVDF).
Optionally, the positive electrode sheet may further comprise a conductive layer located between the positive electrode current collector and the positive electrode material layer. The composition of the conductive layer is not particularly limited, and may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The conductive agent and the binder in the conductive layer are not particularly limited in the present application, and for example, at least one of the conductive agent and the binder may be used.
The negative electrode current collector of the present application is not particularly limited as long as the object of the present application can be achieved, and for example, copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foam nickel, foam copper, or a composite current collector (for example, lithium copper composite current collector, carbon copper composite current collector, nickel copper composite current collector, titanium copper composite current collector, or the like) may be included.
The negative electrode material layer further includes a conductive agent and a binder, and the present application is not particularly limited in kind as long as the object of the present application can be achieved, and for example, may be at least one of the above-mentioned conductive agent and the above-mentioned binder. The mass ratio of the anode active material, the conductive agent and the binder in the anode material layer is not particularly limited, and can be selected by a person skilled in the art according to actual needs as long as the purpose of the application can be achieved.
The thickness of the anode material layer is not particularly limited as long as the object of the present application can be achieved, for example, the thickness of the anode material layer is 20 μm to 150 μm. The thickness of the negative electrode current collector is not particularly limited as long as the object of the present application can be achieved, for example, the thickness of the negative electrode current collector is 4 μm to 12 μm.
Optionally, the negative electrode tab may further comprise a conductive layer located between the negative electrode current collector and the negative electrode material layer. The composition of the conductive layer is not particularly limited in the present application, and may be a conductive layer commonly used in the art. For example, the conductive layer includes a conductive agent and a binder. The conductive agent and the binder in the conductive layer are not particularly limited, and may be at least one of the conductive agent and the binder, for example.
In the application, the isolating film is used for separating the positive electrode plate and the negative electrode plate, preventing the internal short circuit of the electrochemical device, allowing electrolyte ions to pass freely and not influencing the electrochemical charging and discharging process. The isolation film includes a base film and a dielectric coating layer disposed on at least one surface of the base film. That is, the dielectric coating layer may be provided on one surface of the base film in the self thickness direction, or may be provided on both surfaces of the base film in the self thickness direction. The "surface" herein may be the entire region of the surface of the base film or may be a partial region of the surface of the base film, and the present application is not particularly limited as long as the object of the present application can be achieved. When the dielectric coating is provided on one surface of the base film in the thickness direction thereof, the dielectric coating is adjacent to the negative electrode tab. The method of setting the separator according to the present application is not particularly limited as long as the object of the present application can be achieved, and for example, the method of setting the separator may include, but is not limited to, the steps of: adding a dielectric coating material into a solvent to obtain a dielectric coating solution, then setting the dielectric coating solution on one surface of a base film in a dip-coating or spray-coating mode, and drying to obtain the isolation film with the dielectric coating on one surface of the base film. If the isolating film with dielectric coating is needed to be arranged on the two sides of the base film, repeating the steps on the other surface of the base film. The present application is not particularly limited as long as the object of the present application can be achieved, and for example, the solvent may include, but is not limited to, at least one of deionized water, N-methylpyrrolidone, or ethanol. The concentration of the dielectric coating solution is not particularly limited as long as the object of the present application can be achieved, for example, the concentration of the dielectric coating solution may be 20 to 50wt%. The dip coating, spray coating and drying are all dip coating, spray coating and drying treatments known in the art, and the application is not limited thereto, as long as the object of the application can be achieved. Typically, the thickness of the dielectric coating can be varied by adjusting the amount of dielectric coating solution disposed, e.g., the disposed amount of dielectric coating solution increases and the thickness of the dielectric coating increases; the amount of the dielectric coating solution to be disposed is reduced, and the thickness of the dielectric coating is reduced.
The present application is not particularly limited as long as the object of the present application can be achieved. For example, the material of the base film may include, but is not limited to, at least one of Polyethylene (PE), polypropylene (PP) -based Polyolefin (PO), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid; the type of base film may include at least one of a woven film, a nonwoven film, a microporous film, a composite film, a laminate film, or a spun film.
The process of preparing the electrochemical device of the present application is well known to those skilled in the art, and the present application is not particularly limited, and may include, for example, but not limited to, the following steps: sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, winding and folding the positive electrode plate, the isolating film and the negative electrode plate according to the need to obtain an electrode assembly with a winding structure, placing the electrode assembly into a packaging bag, injecting electrolyte into the packaging bag, and sealing to obtain an electrochemical device; or sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, fixing four corners of the whole lamination structure by using adhesive tapes to obtain an electrode assembly of the lamination structure, placing the electrode assembly into a packaging bag, injecting electrolyte into the packaging bag, and sealing to obtain the electrochemical device. In addition, an overcurrent prevention element, a guide plate, or the like may be placed in the package as needed, thereby preventing the pressure inside the electrochemical device from rising and overcharging and discharging. Wherein the package is a package known in the art, and the application is not limited thereto.
A second aspect of the present application provides an electronic device comprising an electrochemical device according to any one of the preceding embodiments. Therefore, the electronic device provided by the application has good service performance.
The kind of the electronic device is not particularly limited in the present application, and it may be any electronic device known in the art. In some embodiments, the electronic device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile machine, a portable copier, a portable printer, a headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-compact disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, a power assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flash light, a camera, a household large-sized battery, a lithium ion capacitor, and the like.
Examples
Hereinafter, embodiments of the present application will be described in more detail with reference to examples and comparative examples. The various tests and evaluations were carried out according to the following methods.
Test method and apparatus:
reversible capacity test:
disassembling a fully-placed lithium ion battery to obtain a positive electrode plate and a negative electrode plate, cutting the positive electrode plate into a circular sheet with the diameter of 10mm, and assembling the circular sheet, a circular diaphragm with the diameter of 15mm, a circular lithium metal sheet with the diameter of 12mm and electrolyte into a button cell; wherein the electrolyte is the electrolyte in example 1. And placing the button cell on a cell test system to perform constant-current charge and discharge test at 0.1C, and taking the capacity of the second circle as the reversible capacity P of the positive pole piece. When the positive electrode active material is NCM811, the test potential interval is 2.8V to 4.3V; when the positive electrode active material is lithium cobaltate, the test potential interval is 3.0V to 4.55V; when the positive electrode active material is NCM622, the test potential interval is 2.8V to 4.3V; when the positive electrode active material is NCM532, the test potential interval is 2.8V to 4.3V.
The positive pole piece is replaced by a negative pole piece, the test potential interval is 0.005V to 0.8V, and the reversible capacity N of the negative pole piece can be measured.
Judging lithium deposition on the surface of the negative electrode plate:
and disassembling the fully charged lithium ion battery to obtain a negative electrode plate, cleaning the negative electrode plate by adopting solvent dimethyl carbonate, then taking an electron microscope picture of the surface of the negative electrode plate, and observing whether lithium deposition on the surface of the negative electrode plate is uniform and whether lithium dendrite exists or not from the electron microscope picture.
Energy density testing:
the test temperature is 25 ℃, the lithium ion battery is kept stand for 5min, discharged to 2.8V at a constant current of 0.2C, kept stand for 5min, charged to 4.25V at a constant current of 0.2C, charged to 0.05C at a constant voltage of 4.25V, kept stand for 5min, discharged to 2.8V at a constant current of 0.2C, and kept stand for 5min. Testing the discharge capacity and recording the voltage value of the platform (namely average discharge voltage), taking 10 lithium ion batteries for each example or comparative example for testing, and taking the average value as the final discharge capacity and the voltage value of the platform; and the mass of each lithium ion battery was tested using an electronic balance, and the average value was also taken as the final mass.
Energy density= (final discharge capacity x plateau voltage)/mass.
And (3) testing the cycle performance:
the test temperature is 25 ℃, the lithium ion battery is kept stand for 30min, charged to 4.25V at a constant current of 0.5C, charged to 0.05C at a constant voltage of 4.25V, kept stand for 5min, discharged to 2.8V at a constant current of 2.0C, and kept stand for 5min, which is a charge-discharge cycle. The charge and discharge cycle is performed according to the above steps, and when the 50 th, 100 th, 150 th, 200 th, 300 th, 400 th, 500 th, 600 th, 700 th, 800 th, 900 th and 1000 th cycles are performed, the charge and discharge is performed according to the following steps: the lithium ion battery is kept stand for 30min, charged to 4.25V at a constant current of 0.5C, charged to 0.05C at a constant voltage of 4.25V, kept stand for 5min, discharged to 2.8V at a constant current of 0.2C, and kept stand for 5min.
The second cycle discharge capacity was taken as the initial discharge capacity, and the cycle capacity retention= (discharge capacity of 1000 th cycle/initial discharge capacity) ×100%.
Example 1
< preparation of Positive electrode sheet >
Mixing an anode active material NCM811, a conductive agent Super P and a binder PVDF according to a mass ratio of 97.7:1.0:1.3, adding N-methyl pyrrolidone (NMP) as a solvent, blending to obtain slurry with a solid content of 75wt%, and uniformly stirring in vacuum to obtain anode slurry. Uniformly coating positive electrode slurry on one surface of a positive electrode current collector aluminum foil with the thickness of 12 mu m, and drying at 120 ℃ to obtain a positive electrode plate with a single-side coated positive electrode material layer, wherein the coating quality of a positive electrode active material in the positive electrode material layer is 12.0mg/cm 2 . And repeating the steps on the other surface of the aluminum foil to obtain the positive electrode plate with the double-sided coating positive electrode material layer. Drying at 120 ℃, cold pressing, cutting and welding the tab to obtain the positive pole piece with the specification of 50mm multiplied by 42mm for standby.
< preparation of negative electrode sheet >
Mixing artificial graphite (with the gram capacity of 357+/-3 mAh/g and the first coulomb efficiency of 93 percent, and the consistency of charge and discharge parameters in the gram capacity and the first coulomb efficiency test process and the reversible capacity test), carboxymethyl cellulose serving as a thickener and styrene-butadiene rubber serving as a binder according to the mass ratio of 97.4:1.0:1.6, adding deionized water as a solvent, preparing slurry with the solid content of 45 weight percent, and uniformly stirring by a vacuum stirrer to obtain the negative electrode slurry. Uniformly coating the anode slurry on one surface of an anode current collector copper foil with the thickness of 10 mu m, and drying at 80 ℃ to obtain an anode piece with an anode material layer coated on one side, wherein the coating quality of an anode active material in the anode material layer is 6.3mg/cm 2 . Then repeating the above steps on the other surface of the copper foil to obtain doubleAnd a negative electrode plate coated with a negative electrode material layer. Drying at 80 ℃, cold pressing, cutting and welding the tab to obtain the negative electrode plate with the specification of 51mm multiplied by 44mm for standby.
< preparation of electrolyte >
In a glove box with a dry argon atmosphere, mixing carbonate compounds of ethylene carbonate, propylene carbonate, dimethyl carbonate and ethylmethyl carbonate according to a mass ratio of 3.0:1.0:4.0:2.0 to obtain an organic solvent, and then adding FEC, liFSI and lithium salt LiPF into the organic solvent 6 And uniformly mixing to obtain the electrolyte. Wherein, based on the mass of electrolyte, the mass percent of FEC a is 5%, the mass percent of LiFSI b is 4%, and LiPF 6 The mass percent e of the catalyst is 8 percent, and the balance is organic solvent.
< preparation of isolation Membrane >
Polyacrylonitrile was dissolved in a solvent NMP to obtain a dielectric coating solution with a mass concentration of 20%. A porous polyethylene film (supplied by Celgard corporation) having a thickness of 7 μm was used as a base film, and a dielectric coating solution was applied to one surface of the base film by spraying, followed by a baking treatment at 60℃to obtain a barrier film containing a dielectric coating. Wherein the thickness of the dielectric coating is 1 μm.
< preparation of lithium ion Battery >
And sequentially stacking the prepared positive pole piece, the isolation film and the negative pole piece, wherein the isolation film is positioned between the positive pole piece and the negative pole piece to play a role in isolation, and the dielectric coating in the isolation film is adjacent to the negative pole piece, so that the electrode assembly is obtained through lamination. And (3) filling the electrode assembly into an aluminum plastic film packaging bag, dehydrating at 80 ℃, injecting the electrolyte prepared by the method, and carrying out the procedures of vacuum packaging, standing, formation, degassing, trimming and the like to obtain the lithium ion battery. The upper limit voltage of the formation is 4.15V, the formation temperature is 80 ℃, and the formation standing time is 1h.
Examples 2 to 24
The procedure of example 1 was repeated except that the relevant production parameters were adjusted as shown in Table 1. When the mass percentage of FEC and/or LiFSI in the electrolyte is changed as compared to example 1, the mass percentage of the organic solvent is changed, and the mass percentage of the lithium salt is unchanged. The weight average molecular weight of the dielectric coating materials of polyacrylonitrile, polyvinylidene fluoride and polyethylene terephthalate is 30000, 45000 and 60000 respectively. The natural Dan Moke capacity of examples 23 and 24 was 360.+ -.3 mAh/g and the first coulombic efficiency was 93% (the gram capacity and the charge and discharge parameters during the first coulombic efficiency test were identical to those in the reversible capacity test described above).
Comparative example 1 and comparative example 4
The procedure of example 1 was repeated except that the relevant production parameters were adjusted as shown in Table 1.
Comparative example 2
The procedure of example 1 was repeated except that FEC and LiFSI were not added to the electrolyte preparation, and the mass percentage of the organic solvent was changed, so that the mass percentage of the lithium salt was not changed.
Comparative example 3
The procedure of example 1 was repeated except that the base film was used as the separator.
Comparative example 5 and comparative example 6
The procedure of example 1 was repeated except that the mass percentage of FEC or LiFSI was changed as shown in table 1, and the mass percentage of the organic solvent and the mass percentage of the lithium salt were not changed.
The relevant preparation parameters and properties of each example and comparative example are shown in table 1.
TABLE 1
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Note that: the "/" in table 1 indicates that there is no corresponding parameter or performance.
As can be seen from examples 1 to 3, comparative examples 1 and 4, when the value of N/P is within the scope of the present application, lithium deposition on the surface of the negative electrode tab is uniform and no lithium dendrite is generated, and the resulting lithium ion battery has both higher cycle capacity retention rate and energy density, which cannot be achieved at the same time. As can be seen from examples 1, 4 to 16, comparative examples 2, 5 and 6, when the electrolyte contains FEC and LiFSI and the mass percentages of FEC and LiFSI are within the scope of the present application, lithium deposition on the surface of the negative electrode sheet is uniform and no lithium dendrite is generated, and the resulting lithium ion battery has both higher cycle capacity retention and energy density, while lithium deposition on the surface of the negative electrode sheet is non-uniform and lithium dendrite is generated in the comparative examples, and the cycle capacity retention and energy density of the lithium ion battery are not compatible. As can be seen from examples 1 to 24 and comparative example 3, when the surface of the separator adjacent to the negative electrode sheet is provided with a dielectric coating, and the dielectric coating material is within the scope of the present application, lithium deposition on the surface of the negative electrode sheet is uniform and no lithium dendrite is generated, and the obtained lithium ion battery has a higher cycle capacity retention rate and energy density at the same time, while lithium deposition on the surface of the negative electrode sheet is uneven and lithium dendrite is generated in the comparative example, and the cycle capacity retention rate and energy density of the lithium ion battery cannot be considered. Therefore, only when the value of N/P, the mass percent of FEC and LiFSI and the surface of the isolating film adjacent to the negative electrode plate are provided with a dielectric coating and the dielectric layer material in the range of the application is selected, the lithium ion battery with good cycle performance and higher energy density can be obtained.
Specifically, as shown in fig. 1 to 6, lithium deposition on the surface of the negative electrode tab in example 1 (fig. 1 and 2) was more uniform and free of lithium dendrites than in comparative example 2 (fig. 3 and 4) and comparative example 3 (fig. 5 and 6). As can be seen from fig. 7 and table 1, the lithium ion batteries of example 1 and comparative example 1 have a smaller difference in the cycle capacity retention rate, but the lithium ion battery of example 1 has a higher energy density. Fig. 8 is a cycle performance test chart of the lithium ion battery in example 1 and comparative example 4, the lithium ion battery in example 1 is tested for 1000 cycles, the lithium ion battery in comparative example 4 is tested for 900 cycles, and it can be seen from fig. 8 that the capacity retention rate of example 1 is always higher than that of comparative example 4 in the same cycle number in the whole cycle process, so as to demonstrate that the lithium ion battery in the example of the present application has better cycle performance.
The thickness of the dielectric coating generally affects the energy density and cycle performance of the lithium ion battery, and it can be seen from examples 1 and 17 that when the thickness of the dielectric coating is within the scope of the present application, lithium deposition on the surface of the negative electrode sheet is uniform and no lithium dendrite is generated, and the obtained lithium ion battery has a higher cycle capacity retention rate and energy density at the same time, which indicates that the lithium ion battery has good cycle performance and higher energy density at the same time.
As can be seen from examples 1, 20 to 24, when the kind of the positive electrode active material and the kind of the negative electrode active material are within the scope of the present application, lithium deposition on the surface of the negative electrode sheet is uniform and no lithium dendrite is generated, and the obtained lithium ion battery has both a higher cycle capacity retention rate and an energy density, indicating that the lithium ion battery has both good cycle performance and a higher energy density.
It should be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
In this specification, each embodiment is described in a related manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments.
The foregoing description is only of the preferred embodiments of the present application and is not intended to limit the scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims (7)

1. An electrochemical device comprises a positive electrode plate, a separation membrane, a negative electrode plate and electrolyte, wherein the separation membrane is arranged between the positive electrode plate and the negative electrode plate; the negative electrode plate comprises a negative electrode current collector and a negative electrode material layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode material layer comprises a negative electrode active material, and the negative electrode active material comprises at least one of artificial graphite, natural graphite, hard carbon, silicon oxide or silicon carbon; the reversible capacity of the positive pole piece is P, and the reversible capacity of the negative pole piece is N, wherein N/P is more than or equal to 0.95 and less than 1.0;
the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode material layer comprises a positive electrode active material, and the positive electrode active material comprises lithium element;
the electrolyte comprises fluoroethylene carbonate and lithium bis (fluorosulfonyl) imide, wherein the mass percentage content a of the fluoroethylene carbonate is 2-10% and the mass percentage content b of the lithium bis (fluorosulfonyl) imide is 1-10% based on the mass of the electrolyte;
the surface of the isolating film adjacent to the negative electrode plate is provided with a dielectric coating, the dielectric coating comprises a dielectric coating material, and the dielectric coating material comprises at least one of polyacrylonitrile, polyvinylidene fluoride, polyethylene terephthalate, polytetrafluoroethylene, polyamide or polysiloxane.
2. The electrochemical device according to claim 1, wherein 4% to 6% of a.
3. The electrochemical device according to claim 1, wherein 6% to 10% of b.
4. The electrochemical device of claim 1, wherein the dielectric coating has a thickness of 1 μιη to 2 μιη.
5. The electrochemical device of claim 1, wherein the positive electrode active material comprises at least one of lithium nickel cobalt manganese oxide, lithium cobalt oxide, or lithium iron phosphate.
6. The electrochemical device of any one of claims 1 to 5, wherein the electrolyte comprises a carbonate compound and a lithium salt, the carbonate compound comprising at least one of dimethyl carbonate, methylethyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, dipropyl carbonate, methylpropyl carbonate, pentafluoropropyl ethylene carbonate, methyltrifluoroethyl carbonate, trifluoroethyl carbonate, trifluoromethylethylene carbonate, or bis (2, 2-trifluoroethyl) carbonate; the lithium salt comprises LiPF 6 、LiBF 4 、LiClO 4 、LiB(C 6 H 5 ) 4 、LiCH 3 SO 3 、LiCF 3 SO 3 、LiN(SO 2 CF 3 ) 2 、LiC(SO 2 CF 3 ) 3 Or Li (lithium) 2 SiF 6 At least one of (a) and (b); the carbonate compound has a mass percentage d of 75 to 90% and the lithium salt has a mass percentage e of 7 to 15% based on the mass of the electrolyte.
7. An electronic device comprising the electrochemical device of any one of claims 1 to 6.
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