CN113939927B - Electrochemical device, electronic device and electrochemical device preparation method - Google Patents

Electrochemical device, electronic device and electrochemical device preparation method Download PDF

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CN113939927B
CN113939927B CN202080040347.2A CN202080040347A CN113939927B CN 113939927 B CN113939927 B CN 113939927B CN 202080040347 A CN202080040347 A CN 202080040347A CN 113939927 B CN113939927 B CN 113939927B
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active material
material layer
positive electrode
binder
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CN113939927A (en
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刘晓欠
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Dongguan 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H01M10/058—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
    • 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
    • H01M4/139—Processes of manufacture
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

An electrochemical device, an electronic device and a preparation method of the electrochemical device are provided, the electrochemical device comprises a positive electrode, the positive electrode comprises a current collector (10), at least one surface of the current collector (10) is provided with a second active material layer (22), and a first active material layer (21) is arranged between the current collector (10) and the second positive active material layer (22). The first active material layer (21) comprises a first active material, a first binder and a conductive agent, the first binder comprises a copolymer formed by polymerizing acrylate, acrylamide and acrylonitrile, the swelling ratio of the first binder is small, and good adhesion between the first active material layer (21) and the current collector (10) can be ensured. The electrochemical device has good nail penetration test and impact test passing rate, and the safety of the electrochemical device can be effectively improved.

Description

Electrochemical device, electronic device and electrochemical device preparation method
Technical Field
The application relates to the field of electrochemistry, in particular to an electrochemical device, an electronic device and a preparation method of the electrochemical device.
Background
The lithium ion battery has the advantages of high energy storage density, high open circuit voltage, low self-discharge rate, long cycle life, good safety performance and the like, and is widely applied to various fields of electric energy storage, mobile electronic equipment, electric automobiles, aerospace equipment and the like. As mobile electronic devices and electric vehicles enter a high-speed development stage, the market puts higher and higher requirements on the energy density, safety performance, cycle performance, service life and the like of lithium ion secondary batteries, wherein the safety performance is particularly important.
At present, safety accidents caused by external force impact or puncture still exist in the use process of the lithium ion battery, and the wide application of the lithium ion battery is hindered. Therefore, a technical means for further improving the safety performance of the lithium ion battery is needed.
Disclosure of Invention
An object of the present application is to provide an electrochemical device, an electronic device, and a method for manufacturing the electrochemical device, which can improve the safety of the electrochemical device.
In the following description, 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 specific technical scheme is as follows:
a first aspect of the present application provides an electrochemical device comprising a positive electrode including: a current collector; a first active material layer including a first active material, a first binder, and a conductive agent; and a second active material layer including a second active material; a second active material layer is arranged on at least one surface of the current collector, and the first active material layer is arranged between the current collector and the second active material layer;
wherein the first binder comprises a copolymer formed by polymerizing acrylate, acrylamide and acrylonitrile.
In one embodiment of the present application, the first binder comprises a copolymer formed by polymerization of an acrylate salt, acrylamide, and acrylonitrile. The copolymer is soaked in electrolyte at 85 ℃ for 24 hours or at 25 ℃ for 7 days, the swelling ratio is less than 5%, and the first active material layer and the current collector or the first active material layer and the second active material layer have good binding power.
In the present application, the weight average molecular weight of the first binder is not particularly limited as long as the object of the present application can be achieved, and for example, the weight average molecular weight of the first binder may be 100000 to 2000000, preferably 300000 to 800000.
The term "swelling" as used herein means that the polymer expands in volume in the electrolyte. Swelling ratio = (volume after soaking-volume before soaking)/volume before soaking × 100%.
In the present application, a second active material layer is provided on at least one surface of the current collector, and the first active material layer is provided between the current collector and the second active material layer. The "surface" herein may be the entire region of the surface of the current collector or a partial region of the surface of the current collector, and the present application is not particularly limited as long as the object of the present application can be achieved.
Through set up first active material layer between mass flow body and second active material layer, can be under the abnormal conditions such as drift bolt, striking, the metal burr that probably produces in the parcel mass flow body to prevent the emergence of short circuit in the lithium ion battery effectively, simultaneously, can prevent the thermal runaway that the local overheat of lithium ion battery caused, thereby avoid lithium ion battery's overheated burning, improve its security.
In general, the electrochemical device provided herein includes a positive electrode including: and a current collector having a second active material layer disposed on at least one surface thereof, the first active material layer being disposed between the current collector and the second active material layer. The first active material layer comprises a first active material, a first binder and a conductive agent, wherein the first binder comprises a copolymer formed by polymerization of acrylonitrile, acrylate and acrylamide. The swelling rate of this first binder is little, can guarantee to have good adhesion between first active material layer and the mass flow body, and at the drift test or striking test in-process, first active material layer adhesion increases contact resistance on the mass flow body surface, reduces temperature rise and safe risk, improves the throughput of drift test and striking test to effectively improve lithium ion battery's security.
In one embodiment of the present application, the resistance of the positive electrode after the electrochemical device is fully charged is 10 Ω or more, preferably 30 Ω to 100 Ω. The positive electrode resistance is controlled within the range, so that the internal resistance of the lithium ion battery in short circuit can be increased, the short-circuit current is reduced, and the temperature rise is reduced, thereby improving the safety of the lithium ion battery.
In one embodiment of the present application, the acrylonitrile is present in an amount of 1 to 70% by mass, the acrylate is present in an amount of 1 to 70% by mass, and the acrylamide is present in an amount of 1 to 70% by mass, based on the total mass of the above-mentioned copolymer. Preferably, the acrylonitrile content is 10 to 70% by mass, the acrylate content is 10 to 70% by mass, and the acrylamide content is 10 to 70% by mass, based on the total mass of the copolymer. More preferably, the acrylonitrile content is 40 to 60% by mass, the acrylate content is 10 to 50% by mass, and the acrylamide content is 10 to 50% by mass, based on the total mass of the copolymer. By controlling the acrylonitrile, acrylate and acrylamide within the above-mentioned range of the total mass of the copolymer, the first binder can be made to have better adhesion in use.
In one embodiment of the present application, the first active material layer further includes a leveling agent, and the leveling agent may include at least one of a polymer of an olefin derivative, a carboxylate polymer, a siloxane polymer, an acrylate polymer, an alcohol polymer, an ether polymer, or the like. Preferably, the leveling agent may include at least one of a sodium carboxylate polymer, an oxypropylene polymer, or a polysiloxane. For example, the leveling agent may include at least one of polyethoxypropoxypropylene, polysiloxane, polymethyl acrylate, polyethylene glycol, sodium polycarboxylate, polyallyl alcohol, or the like. The leveling agent is added into the first active substance layer, so that the surface tension of the first active substance can be reduced, the leveling property of the first active substance can be improved, the wetting property, spreading property and leveling property of the first active substance on the surface of the current collector can be improved, the probability of missing coating of the first active substance layer on the current collector can be reduced, the first active substance can be uniformly coated on the current collector, and the safety performance of the lithium ion battery can be optimized.
In the present application, the weight average molecular weight of the leveling agent is not particularly limited as long as the object of the present application can be achieved, and for example, the weight average molecular weight of the leveling agent may be not higher than 50000.
In one embodiment of the present application, the content of the first positive electrode active material in the first positive electrode active material layer is 50wt% to 98.89wt%, the content of the first binder is 1wt% to 20wt%, the content of the conductive agent is 0.1wt% to 20wt%, and the content of the leveling agent is 0.01wt% to 10wt%.
Through controlling the content of the first active material, the first binder, the conductive agent and the flatting agent in the first active material layer within the range, the adhesive force between the first active material layer and the current collector can be ensured, and the first active material can be uniformly distributed on the first active material layer, so that the temperature rise of the lithium ion battery is reduced, the safety and reliability are improved, and the nail penetration test and the impact test passing rate of the lithium ion battery are improved.
In one embodiment of the present application, the conductive agent is not particularly limited as long as the object of the present application can be achieved, and for example, the conductive agent may include at least one of a lamellar, mesh, linear, or zero-dimensional conductive agent, and the like. Preferably, the conductive agent may include at least one of graphene, reticular graphite fibers, carbon nanotubes, ketjen black, graphite fibers, or nanoparticle conductive carbon, and the like. By adding the conductive agent into the first active material layer, the migration rate of lithium ions in the first active material layer can be effectively improved, so that the charge and discharge efficiency of the lithium ion battery is improved.
In one embodiment of the present application, the Dv99 of the first active substance is between 0.01 μm and 19.9 μm. By controlling the Dv99 of the first active material within the above range, the flatness of the first active material layer can be improved; preferably, dv99 of the first active material does not exceed the thickness of the first active material layer, otherwise the aluminum foil is easy to be stabbed in the cold pressing process, and concave-convex points are formed to exceed the thickness of the target first active material layer.
In one embodiment of the present application, the first active material layer has a monolayer thickness of 0.04 μm to 20 μm, and when the thickness of the first active material layer is too low, for example, less than 0.04 μm, the first active material layer is too thin, the performance is affected; when the thickness of the first active material layer is too high, for example, higher than 20 μm, the relative content of the first active material in the pole piece decreases, which affects the energy density of the lithium ion battery.
In one embodiment of the present application, the second active material layer has a monolayer thickness of 20 μm to 200 μm, and when the thickness of the second active material layer is too low, for example, less than 20 μm, the energy density of the lithium ion battery is affected and the processing is not easy in the case of a constant capacity; when the thickness of the second active material layer is too high, for example, more than 200 μm, lithium ion battery kinetics are deteriorated.
In an embodiment of this application, the cohesive force of first active material layer and mass flow body is more than 201N/m, and it can be seen that the first active material layer and the mass flow body of this application have excellent adhesive property between them, can effectively improve lithium ion battery's the through-nail test percent of pass.
In one embodiment of the present application, a current collector includes a coated region where a first active material and a second active material are disposed, and an uncoated region where the first active material and the second active material are not disposed; the uncoated zone is at least partially provided with an insulating layer. Through the setting of insulating layer, can promote the insulating properties in coating insulating layer region in this application, and then promote lithium ion battery security performance. In the electrochemical device of the present application, an insulating layer may be at least partially disposed in the above uncoated region, and various disposition may be adopted, for example, which may include, but is not limited to: the insulating layers are arranged on two sides of the positive electrode in the length direction, the insulating layers are arranged on the starting end side of the positive electrode, and the insulating layers are arranged on the ending end side of the positive electrode. The above arrangement modes can be adopted singly or in combination. The starting end and the ending end can refer to the starting end and the ending end of a winding structure in the lithium ion battery with the winding structure.
In one embodiment of the present application, the adhesion force between the insulating layer and the current collector is above 201N/m, and it can be seen that the insulating layer and the current collector of the present application have excellent adhesion performance, thereby reducing the thickness increase rate and the internal resistance increase rate of the lithium ion battery.
In one embodiment of the present application, the coverage of the insulating layer is from 90% to 100%. By controlling the coverage of the insulating layer within the above range, the safety performance of the lithium ion battery can be improved.
In one embodiment of the present application, the insulating layer further includes inorganic particles, a second binder, and a leveling agent;
the inorganic particles may include at least one of boehmite, diaspore, alumina, barium sulfate, calcium silicate, or the like; preferably, the inorganic particles may include at least one of boehmite, alumina, or the like. The addition of the inorganic particles can improve the strength and insulating property of the insulating layer.
The second binder may include at least one of a copolymer of a propylene derivative, a polyacrylate, a acrylonitrile-based multipolymer, a carboxymethyl cellulose salt, a nitrile rubber, or the like; preferably, the second binder may include at least one of a propylene-based polymer or a nitrile rubber, or the like. The swelling rate of the second binder in the electrolyte is small, and the high binding power is kept.
In the present application, the weight average molecular weight of the second binder is not particularly limited as long as the object of the present application can be achieved, and for example, the weight average molecular weight of the second binder may be 100000 to 2000000, preferably 300000 to 800000.
In one embodiment of the present application, the content of the inorganic particles in the insulating layer is 40 to 97.99wt%, the content of the second binder is 2 to 50wt%, and the content of the leveling agent is 0.01 to 10wt%. Preferably, the content of the inorganic particles in the insulating layer is 72wt% to 94.9wt%, the content of the second binder is 5wt% to 25wt%, and the content of the leveling agent is 0.1wt% to 3wt%. By controlling the contents of the inorganic particles, the second binder and the leveling agent in the insulating layer within the above range, the insulating layer can be uniformly coated on the current collector of the anode, so that the strength of the insulating layer and the binding force between the insulating layer and the current collector are improved, and the safety performance of the lithium ion battery is improved.
In one embodiment of the present application, the insulating layer has a thickness of 0.02 μm to 10 μm. When the thickness of the insulating layer is less than 0.02 mu m, the strength of the insulating layer is too low and the insulating layer is easy to crack, so that the insulating property of the area is influenced; when the thickness of the insulating layer is greater than 10 μm, the energy density of the lithium ion battery may be affected by the excessive thickness of the insulating layer.
The method for preparing the first binder of the present application is not particularly limited, and a method known to those skilled in the art may be used, and for example, the following method may be used:
adding distilled water into a reaction kettle, starting stirring, introducing nitrogen to remove oxygen, adding at least one of the components such as acrylonitrile, acrylate, acrylamide and the like according to different mass ratios, heating to about 65 ℃ under an inert atmosphere, keeping the temperature constant, then adding an initiator to initiate a reaction, and ending after about 20 hours of reaction.
The initiator is not particularly limited as long as it can initiate polymerization of the monomers, and may be, for example, a 20% ammonium persulfate solution. The amount of the distilled water and the initiator added is not particularly limited as long as the polymerization of the added monomers is ensured. After the reaction, a basic solution was added to the precipitate of the reaction to neutralize it to a pH of 6.5 to 9. Then, the reaction product is filtered, washed, dried, crushed, sieved and the like.
It is understood by those skilled in the art that the positive electrode of the present application may be provided with a first active material layer and a second active material layer on one surface thereof, or may be provided with a first active material layer and a second active material layer on both surfaces thereof. The insulating layer of the present application may be provided on at least one surface of the positive electrode, and for example, the insulating layer may be provided on one surface of the positive electrode or may be provided on both surfaces of the positive electrode.
In the positive electrode of the present application, the current collector is not particularly limited, and may be a current collector known in the art, such as an aluminum foil, an aluminum alloy foil, or a composite current collector. The first active material layer includes a first active material, and the second active material layer includes a second active material, and in the present application, the first active material and the second active material may be the same or different, and the first active material and the second active material are not particularly limited, and active materials known in the art may be used, and for example, may each independently include at least one of lithium nickel cobalt manganese (811, 622, 523, 111), lithium nickel cobalt aluminate, lithium iron phosphate, a lithium rich manganese-based material, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate, or lithium titanate. In the present application, the thickness of the current collector of the positive electrode is not particularly limited as long as the object of the present application can be achieved, and for example, the thickness of the current collector is 8 μm to 12 μm.
The negative electrode of the present application is not particularly limited as long as the object of the present application can be achieved. For example, the negative electrode generally includes a current collector and an active material layer. In the present application, the current collector is not particularly limited, and a current collector known in the art, such as a copper foil, a copper alloy foil, a composite current collector, and the like, may be used. The active material layer is not particularly limited, and active materials known in the art can be used. For example, at least one of artificial graphite, natural graphite, mesocarbon microbeads, silicon carbon, silicon oxy-compound, soft carbon, hard carbon, lithium titanate, niobium titanate, or the like may be included. In the present application, the thicknesses of the current collector and the active material layer of the negative electrode are not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the current collector is 4 μm to 10 μm, and the thickness of the active material layer is 30 μm to 120 μm.
Optionally, the negative electrode may further include a conductive layer between the current collector and the active 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 above-mentioned conductive agent is not particularly limited as long as the object of the present application can be achieved. For example, the conductive agent may include at least one of conductive carbon black (Super P), carbon Nanotubes (CNTs), carbon fibers, graphene, or the like. The above-mentioned binder is not particularly limited, and any binder known in the art may be used as long as the object of the present application can be achieved. For example, the binder may include at least one of styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), sodium carboxymethylcellulose (CMC-Na), or the like. For example, styrene Butadiene Rubber (SBR) may be used as the binder.
The lithium ion battery further comprises an isolating membrane used for separating the positive electrode from the negative electrode, preventing short circuit inside the lithium ion battery, allowing electrolyte ions to freely pass through, and completing the effect of an electrochemical charging and discharging process. In the present application, the separator is not particularly limited as long as the object of the present application can be achieved.
For example, at least one of Polyolefin (PO) based separators mainly composed of Polyethylene (PE) and polypropylene (PP), polyester films (e.g., polyethylene terephthalate (PET) films), cellulose films, polyimide films (PI), polyamide films (PA), spandex or aramid films, woven films, nonwoven films (nonwoven fabrics), microporous films, composite films, separator papers, rolled films, and spun films.
For example, the release film may include a base material layer and a surface treatment layer. The substrate layer may be a non-woven fabric, a film or a composite film having a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, and the like. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film may be used. Optionally, a surface treatment layer is disposed on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance.
For example, the inorganic layer includes inorganic particles and a binder, and the inorganic particles are not particularly limited and may be, for example, at least one selected from the group consisting of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium sulfate, and the like. The binder is not particularly limited, and may be, for example, one or a combination of several selected from polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer contains a polymer, and the material of the polymer comprises at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, poly (vinylidene fluoride-hexafluoropropylene), and the like.
The lithium ion battery of the present application further includes an electrolyte, which may be one or more of a gel electrolyte, a solid electrolyte, and an electrolyte including a lithium salt and a non-aqueous solvent.
In some embodiments herein, the lithium salt is selected from LiPF 6 、LiBF 4 、LiAsF 6 、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 、LiSiF 6 One or more of LiBOB and lithium difluoroborate. For example, the lithium salt may be LiPF 6 Since it can give high ionic conductivity and improve cycle characteristics.
The non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvent, or a combination thereof.
The carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluoro carbonate compound, or a combination thereof.
Examples of the above chain carbonate compound are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl Propyl Carbonate (MPC), ethyl Propyl Carbonate (EPC), methyl Ethyl Carbonate (MEC), and combinations thereof. Examples of the cyclic carbonate compound are Ethylene Carbonate (EC), propylene Carbonate (PC), butylene Carbonate (BC), vinyl Ethylene Carbonate (VEC), and combinations thereof. Examples of the fluoro carbonate compounds are fluoroethylene carbonate (FEC), 1, 2-difluoroethylene carbonate, 1, 2-trifluoroethylene carbonate, 1, 2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1, 2-difluoro-1-methylethylene carbonate, 1, 2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof.
Examples of the above carboxylic acid ester compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ -butyrolactone, decalactone, valerolactone, mevalonolactone, caprolactone, and combinations thereof.
Examples of the above ether compounds are dibutyl ether, tetraglyme, diglyme, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.
Examples of such other organic solvents are dimethylsulfoxide, 1, 2-dioxolane, sulfolane, methylsulfolane, 1, 3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters and combinations thereof.
A second aspect of the present application provides an electronic device comprising the electrochemical device provided in the first aspect of the present application.
The electronic device of the present application is not particularly limited, and 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 phone, a portable facsimile machine, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a handheld cleaner, a portable CD player, a mini-disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power source, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large household battery, a lithium ion capacitor, and the like.
The process for preparing the electrochemical device is well known to those skilled in the art, and the present application is not particularly limited.
In one embodiment of the present application, a method of manufacturing an electrochemical device includes:
(1) Mixing a first active material, a first binder, a conductive agent and a solvent to obtain first active material layer slurry;
(2) Coating the first active material layer slurry on a current collector, and drying to obtain a first active material layer;
(3) Mixing a second active material, a binder, a conductive agent and a solvent to obtain second active material layer slurry;
(4) Coating the second active material layer slurry on the first active material layer, and drying to obtain a positive electrode;
(5) And sequentially stacking the anode, the isolating membrane and the cathode, winding to obtain an electrode assembly, packaging the electrode assembly into a packaging bag, and performing subsequent treatment to obtain the electrochemical device.
In one embodiment of the present application, a method of manufacturing an electrochemical device includes: an insulating layer is coated on the uncoated region of the current collector.
For example, the electrochemical device may be manufactured by the following process: the positive electrode and the negative electrode are overlapped via a separator, and are wound, folded, and the like as needed, and then placed in a case, and an electrolyte is injected into the case and sealed. In addition, an overcurrent prevention element, a guide plate, or the like may be placed in the case as necessary to prevent a pressure rise and overcharge/discharge inside the electrochemical device.
The application provides an electrochemical device and electronic device, it includes the positive pole, and the positive pole includes the mass flow body, is provided with the second active material layer on this at least one surface of mass flow body, and the first active material layer sets up between mass flow body and second active material layer. The first active material layer includes a first active material, a first binder including a copolymer formed by polymerizing acrylate, acrylamide and acrylonitrile, and a conductive agent. The swelling ratio of the first binder is small, and good binding power between the first active material layer and the current collector can be ensured. The electrochemical device has good nail penetration test and impact test passing rate, and the safety of the electrochemical device can be effectively improved.
Drawings
In order to illustrate the technical solutions of the present application and the prior art more clearly, the following briefly introduces examples and figures that need to be used in the prior art, it being obvious that the figures in the following description are only some examples of the present application.
Fig. 1 is a schematic structural view of a positive electrode of an embodiment of the present application;
fig. 2 is a schematic structural view of a positive electrode according to another embodiment of the present application;
fig. 3 is a schematic structural view of a positive electrode of yet another embodiment of the present application;
fig. 4 is a graph showing the relationship between the adhesion and the stroke in the adhesion test according to the present application.
Reference numerals: 10. collector, 21, first active material layer, 22, second active material layer, 30, insulating layer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be apparent that the described embodiments are only a few embodiments of the present application, and not all embodiments. All other technical solutions obtained by a person of ordinary skill in the art based on the embodiments in the present application belong to the protection scope of the present application.
In the embodiments 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.
Fig. 1 shows a schematic structural view of a positive electrode in one embodiment of the present application, in which uncoated regions, i.e., regions where the first active material layer 21 and the second active material layer 22 are not disposed, may exist on the left and right sides of the positive electrode, and the current collector 10 is exposed to the uncoated regions, and in fig. 1, the insulating layer 30 may be disposed on the uncoated regions, and particularly, may be disposed on both sides of the positive electrode in the length direction. Of course, the positive electrode may be provided only on one side in the longitudinal direction.
Fig. 2 shows a schematic view of the structure of a positive electrode in another embodiment of the present application, the a surface of the current collector 10 is provided with the first active material layer 21 and the second active material layer 22, and the a surface of the current collector 10 may have an uncoated region; the B surface of current collector 10 may have uncoated regions. In fig. 2, the insulating layer 30 may be disposed on both sides of the coating region of the surface a of the current collector 10 in the length direction, and the insulating layer 30 may also be disposed on the surface B of the current collector 10.
Fig. 3 shows a schematic view of the structure of a positive electrode in another embodiment of the present application, the entire area of the a surface of the current collector 10 is provided with the first active material layer 21 and the second active material layer 22, and the B surface of the current collector 10 may have an uncoated region. In fig. 3, an insulating layer 30 may be disposed on the B surface of the current collector 10.
Fig. 4 shows the relationship between the adhesion force and the stroke in the adhesion force test of the present application.
Examples
Hereinafter, embodiments of the present application will be described in more detail with reference to examples and comparative examples. Various tests and evaluations were carried out by the following methods. Unless otherwise specified, "part" and "%" are based on mass.
The test method and the test device are as follows:
and (3) testing the adhesive force:
the adhesion between the insulating layer/first active material layer and the current collector was tested using a high-iron tensile machine, 90 ° angle method: and cutting the positive electrode provided with the insulating layer/first active material layer part in the finished lithium ion battery into a strip sample of 20mm multiplied by 60mm, wherein the length and width values of the sample can be proportionally adjusted according to actual conditions. Adhering a part of the sample insulating layer or the first active material layer to a steel plate by double-sided adhesive from one end of the sample along the length direction of the sample, wherein the adhering length is not less than 40mm; then the steel plate is fixed at the corresponding position of a high-speed rail tensile machine, the other end which is not adhered to the steel plate is pulled up, and a sample is placed into a chuck through a connector or directly and clamped, wherein the pulled sample part and the steel plate form an included angle of 90 degrees in space. The chuck pulls the sample at a speed of 5mm/min, so that the insulating layer/the first active material layer is separated from the current collector, and finally the average tension of the measured stable area is recorded as the adhesive force between the insulating layer/the first active material layer and the current collector. As shown in fig. 4, it is required that the ratio of the standard deviation of the above-described bonding force data of the plateau region to the average value does not exceed 10%.
Testing the coverage of the insulating layer:
1) Cutting the pole piece coated with the insulating coating to obtain a pole piece sample coated with the insulating coating, and recording the area of one surface coated with the insulating coating as S1;
2) Counting the area (namely the coating leakage area) of the current collector, which is not covered by the insulating material, on the surface coated with the insulating layer in the pole piece sample in 1) by using a CCD microscope with the resolution of 0.02 mu m, and recording the area as S2;
3) The coverage B of the insulating layer is calculated by the following expression: b = (S1-S2)/S1 × 100%.
Inorganic particle Dv99 test:
inorganic particles were tested for Dv99 using a laser particle sizer.
Dv99 means a particle diameter at which the inorganic particles reach 99% of the volume accumulation from the small particle diameter side in the volume-based particle size distribution, that is, the volume of the inorganic particles smaller than this particle diameter accounts for 99% of the total volume of the inorganic particles.
Testing the thickness of the insulating layer:
1) And (3) detaching the pole piece coated with the insulating coating from the finished product battery core under the environment of (25 +/-3) DEG C. Wiping the residual electrolyte on the surface of the pole piece by using dust-free paper;
2) Cutting the pole piece coated with the insulating layer under plasma to obtain the cross section of the pole piece;
3) Observing the cross section of the pole piece obtained in the step 2) under SEM, testing the thickness of the single-sided insulating coating, testing adjacent test points at intervals of 2-3 mm, testing at least 15 different points, and recording the average value of all the test points as the thickness of the insulating coating.
Thickness test of first active material layer and second active material layer:
1) Detaching the positive pole piece coated with the first active material layer and the second active material layer from the finished lithium ion battery;
2) Cutting the positive pole piece obtained in the step 1) along the thickness direction of the positive pole by using a plasma cutting technology to obtain cross sections of the first active material layer and the second active material layer;
3) Observing the cross sections of the first active material layer and the second active material layer obtained in the step 2) under an SEM (electron microscope) (the length of the observed cross section is required to be not less than 2 cm), respectively testing the single-side thicknesses of the first active material layer and the second active material layer under the SEM, testing at least 15 different points at intervals of 2mm to 3mm, and recording the thickness average value of all testing positions of each layer as the thickness value of the corresponding layer.
And (3) testing the full charge internal resistance of the positive electrode:
1) The lithium ion battery is charged with a multiplying factor of 0.05C to a voltage of 4.45V (namely, a full charge voltage) in a constant current mode, and then charged with a constant voltage of 4.45V to a current of 0.025C (cut-off current), so that the lithium ion battery reaches a full charge state;
2) Disassembling the lithium ion battery to obtain a positive electrode;
3) Soaking the positive electrode obtained in the step 2) in DMC (dimethyl carbonate) for 1h at 25 ℃, and then airing in a fume hood;
4) Testing the resistance of the positive pole piece obtained in the step 3) by using a BER1200 model diaphragm resistance tester, wherein the interval between adjacent test points is 2mm to 3mm, at least 15 different points are tested, and the resistance mean value of all the test points is recorded as the diaphragm resistance of the positive pole piece. Wherein the parameters are as follows: the area of the pressure head is 153.94mm 2 Pressure 3.5t, hold time 50s.
The 90-degree vertical side edge nail penetration test pass rate test:
and charging the lithium ion battery to be tested to 4.45V (namely full charge voltage) by constant current with the multiplying power of 0.05C, and then charging to 0.025C (cut-off current) by constant voltage of 4.45V to ensure that the lithium ion battery reaches a full charge state, and recording the appearance of the lithium ion battery before testing. The battery is subjected to a nail penetration test in an environment of 25 +/-3 ℃, the diameter of a steel nail is 4mm, the penetration speed is 30mm/s, the nail penetration position is located on the side face of a lithium ion battery, the test is stopped after the test is carried out for 3.5min or the surface temperature of an electrode assembly is reduced to 50 ℃, 10 lithium ion batteries are taken as a group, the states of the lithium ion batteries in the test process are observed, the judgment standard that the lithium ion batteries do not burn or explode is taken, and the nail penetration test is judged to pass after more than 15 times of 20 nail penetration tests.
Example 1
< preparation of first Binder >
Adding distilled water into a reaction kettle, starting stirring, introducing nitrogen to remove oxygen for 2 hours, adding a sodium acrylate monomer into the reaction kettle, heating to 65 ℃ under an inert atmosphere, keeping the temperature constant, adding a 20% ammonium persulfate solution serving as an initiator to start reaction, taking out a precipitate after reacting for 22 hours, adding alkali liquor to neutralize the precipitate, and keeping the pH value to be 6.5. Wherein the mass ratio of distilled water, monomer and initiator is 89.5: 10: 0.5. And after the reaction, filtering, washing, drying, crushing, sieving and the like are carried out on the reaction product to obtain the first binder.
< preparation of second Binder >
Adding distilled water into a reaction kettle, starting stirring, introducing nitrogen to remove oxygen for 2 hours, adding a methyl acrylate monomer into the reaction kettle, heating to 65 ℃ under an inert atmosphere, keeping the temperature constant, then adding a 20% ammonium persulfate solution as an initiator to start reaction, taking out a precipitate after reacting for 22 hours, adding alkali liquor to neutralize the precipitate, and keeping the pH value to be 6.5. Wherein the mass ratio of distilled water, monomer and initiator is 89.5: 10: 0.5. And after the reaction, filtering, washing, drying, crushing, sieving and the like are carried out on the reaction product to obtain the second binder.
< preparation of insulating layer slurry >
Dispersing a second binder, inorganic particle boehmite and a flatting agent polyethenoxy propoxy propylene olefin in deionized water, and uniformly stirring until the viscosity of the slurry is stable to obtain an insulating layer slurry with the solid content of 30%, wherein the mass ratio of the second binder to the inorganic particles to the flatting agent is 15: 84.9: 0.1. The weight average molecular weight of the leveling agent is 20000, and the weight average molecular weight of the second binder is 500000.
< preparation of Positive electrode >
Mixing a first active material lithium iron phosphate, a first binder, nano-particle conductive carbon, a carbon nano tube and a flatting agent polyethoxy propoxy propylene hydrocarbon according to the mass ratio of 95.6: 3: 0.7: 0.5: 0.2, adding N-methyl pyrrolidone (NMP) as a solvent, blending into slurry with the solid content of 75%, and uniformly stirring. Uniformly coating the slurry on a current collector aluminum foil with the thickness of 10 mu m, and drying at 90 ℃ to obtain a first active material layer with the thickness of 5 mu m; wherein the first binder has a weight average molecular weight of 500000, the leveling agent has a weight average molecular weight of 20000, and the first active material has a Dv99 of 4 μm;
mixing a second active substance, namely Lithium Cobaltate (LCO), polyvinylidene fluoride (PVDF), conductive carbon black and carbon nano tubes according to the mass ratio of 97.7: 1.3: 0.5, adding N-methylpyrrolidone (NMP) serving as a solvent, preparing slurry with the solid content of 75%, and uniformly stirring. Uniformly coating the slurry on the first active material layer, and drying at 90 ℃ to obtain a second active material layer with the thickness of 85 micrometers;
the prepared insulating layer slurry was coated on a region of the surface of the aluminum foil where the first and second active material layers were not coated, i.e., an uncoated region, to obtain an insulating layer having a thickness of 6 μm and a coverage of the insulating layer of 95%.
The above steps are then repeated on the other surface of the positive electrode, resulting in a positive electrode coated on both sides with a first active material layer, a second active material layer, and an insulating layer. Cutting the positive electrode into a size of 74mm × 867mm, and welding the lug for later use.
< preparation of negative electrode >
Mixing active substance graphite, styrene-butadiene polymer and sodium carboxymethylcellulose at a weight ratio of 97.5: 1.3: 1.2, adding deionized water as solvent, blending to obtain slurry with solid content of 70%, and stirring. And uniformly coating the slurry on a current collector copper foil, drying at 110 ℃, and cold-pressing to obtain the negative electrode with the active material layer coated on one side, wherein the thickness of the active material layer is 150 mu m.
And after the steps are finished, the steps are also finished on the back surface of the cathode by adopting the same method, and the cathode with the double-sided coating is obtained. After the coating was completed, the negative electrode was cut into sheets of 76mm × 851mm in size and the tabs were welded for use.
< preparation of electrolyte solution >
Mixing organic solvents ethylene carbonate, ethyl methyl carbonate and diethyl carbonate at a mass ratio of EC: EMC: DEC = 30: 50: 20 in a dry argon atmosphere to obtain an organic solution, and then adding lithium salt lithium hexafluorophosphate into the organic solvent to dissolve and uniformly mix the organic solution to obtain an electrolyte with the concentration of lithium salt being 1.15 Mol/L.
< preparation of separator >
Alumina and polyvinylidene fluoride were mixed in a mass ratio of 90: 10 and dissolved in deionized water to form a ceramic slurry with 50% solids. The ceramic slurry was then uniformly coated on one side of a porous substrate (polyethylene, thickness 7 μm, average pore diameter 0.073 μm, porosity 26%) by a gravure coating method, and dried to obtain a two-layer structure of a ceramic coating layer and the porous substrate, the ceramic coating layer having a thickness of 50 μm.
Polyvinylidene fluoride (PVDF) was mixed with polyacrylate in a mass ratio of 96: 4 and dissolved in deionized water to form a polymer slurry with 50% solids. And then uniformly coating the polymer slurry on two surfaces of the ceramic coating and porous substrate double-layer structure by adopting a dimple coating method, and drying to obtain the isolating membrane, wherein the thickness of a single-layer coating formed by the polymer slurry is 2 mu m.
< preparation of lithium ion Battery >
And (3) sequentially stacking the prepared positive electrode, the prepared isolating membrane and the prepared negative electrode, enabling the isolating membrane to be positioned between the positive electrode and the negative electrode to play an isolating role, and winding to obtain the electrode assembly. And (3) putting the electrode assembly into an aluminum-plastic film packaging bag, dehydrating at 80 ℃, injecting the prepared electrolyte, and performing vacuum packaging, standing, formation, shaping and other processes to obtain the lithium ion battery.
Example 2
The same as example 1 was repeated except that in < preparation of first binder >, the sodium acrylate monomer was replaced with the acrylamide monomer.
Example 3
Except that in < preparation of first binder >, the sodium acrylate monomer was replaced with acrylamide monomer at a mass ratio of 40: 60: the procedure of example 1 was repeated except for using sodium acrylate.
Example 4
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with acrylonitrile monomer in a mass ratio of 40: 60: the procedure of example 1 was repeated except for acrylamide.
Example 5
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with acrylonitrile monomer at a mass ratio of 40: 60: the procedure of example 1 was repeated except for using sodium acrylate.
Example 6
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with monomer acrylonitrile in a mass ratio of 30: 60: 10: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 7
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with monomer acrylonitrile in a mass ratio of 30: 10: 60: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 8
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with monomer acrylonitrile in a mass ratio of 40: 50: 10: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 9
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with monomer acrylonitrile in a mass ratio of 40: 10: 50: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 10
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with monomer acrylonitrile in a mass ratio of 45: 10: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 11
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with monomer acrylonitrile in a mass ratio of 45: 10: 45: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 12
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with monomer acrylonitrile in a mass ratio of 50: 40: 10: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 13
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with monomer acrylonitrile in a mass ratio of 50: 10: 40: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 14
Except that in < preparation of first binder >, sodium acrylate was replaced with monomer acrylonitrile in a mass ratio of 55: 35: 10: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 15
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with monomer acrylonitrile in a mass ratio of 55: 10: 35: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 16
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with monomer acrylonitrile in a mass ratio of 60: 30: 10: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 17
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with monomer acrylonitrile in a mass ratio of 60: 10: 30: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 18
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with monomer acrylonitrile in a mass ratio of 70: 20: 10: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 19
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with monomer acrylonitrile in a mass ratio of 70: 10: 20: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 20
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with monomer acrylonitrile in a mass ratio of 10: 70: 20: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 21
Except that in < preparation of first binder >, sodium acrylate monomer was replaced with monomer acrylonitrile in a mass ratio of 10: 20: 70: sodium acrylate: the procedure of example 1 was repeated except for acrylamide.
Example 22
The same as example 10 was repeated, except that the content of the first binder in < preparation of positive electrode > was 1 wt%.
Example 23
The same as example 10 was repeated, except that the content of the first binder in < preparation of positive electrode > was 2 wt%.
Example 24
The same as example 10 was repeated, except that the content of the first binder in < preparation of positive electrode > was 4 wt%.
Example 25
The same as example 10 was repeated, except that the content of the first binder in < preparation of positive electrode > was 5 wt%.
Example 26
The same as example 10 was repeated, except that the content of the first binder in < preparation of positive electrode > was 8 wt%.
Example 27
The same as example 10 was repeated, except that the content of the first binder in < preparation of positive electrode > was 10wt%.
Example 28
The same as example 10 was repeated, except that the content of the first binder in < preparation of positive electrode > was 12 wt%.
Example 29
The same as example 10 was repeated, except that the content of the first binder in < preparation of positive electrode > was 15 wt%.
Example 30
The same as example 10 was repeated, except that the content of the first binder in < preparation of positive electrode > was 18 wt%.
Example 31
The same as example 10 was repeated except that the content of the first binder in < preparation of positive electrode > was 20 wt%.
Example 32
Except that in < preparation of positive electrode >, lithium iron phosphate was replaced with lithium manganese iron phosphate, and the same was as in example 10.
Example 33
The procedure was as in example 10, except that in < preparation of positive electrode >, lithium iron phosphate was replaced with lithium manganate.
Example 34
Example 32 was repeated except that in < preparation of positive electrode >, 0.7wt% of the nanoparticle conductive carbon and 0.5wt% of the carbon nanotubes were replaced with 1.2wt% of the carbon nanotubes, dv99 of the first positive electrode active material was 0.01 μm, and the thickness of the first positive electrode active material layer was 0.04 μm.
Example 35
The same as example 34 was repeated except that in < preparation of positive electrode >, dv99 of the first positive electrode active material was 0.02 μm, and the thickness of the first positive electrode active material layer was 0.06 μm.
Example 36
The procedure of example 34 was repeated, except that in < preparation of positive electrode >, dv99 of the first positive electrode active material was 0.03 μm, and the thickness of the first positive electrode active material layer was 0.08 μm.
Example 37
The same as example 34 was repeated except that in < preparation of positive electrode >, dv99 of the first positive electrode active material was 0.05 μm, and the thickness of the first positive electrode active material layer was 0.1 μm.
Example 38
The same as example 34 was repeated except that in < preparation of positive electrode >, dv99 of the first positive electrode active material was 0.08 μm, and the thickness of the first positive electrode active material layer was 0.2 μm.
Example 39
The same as example 32 was repeated except that in < preparation of positive electrode >, lithium manganese iron phosphate was contained in an amount of 96wt%, nano-particle conductive carbon was contained in an amount of 0.3wt%, dv99 of the first positive electrode active material was 0.5 μm, and the thickness of the first positive electrode active material layer was 2 μm.
Example 40
The procedure was carried out in the same manner as in example 39 except that in < preparation of positive electrode >, dv99 of the first positive electrode active material was 1 μm, and the thickness of the first positive electrode active material layer was 3 μm.
Example 41
The procedure of example 32 was repeated, except that in < preparation of positive electrode >, dv99 of the first positive electrode active material was 3 μm.
Example 42
The same as example 32 was repeated except that in < preparation of positive electrode >, dv99 of the first positive electrode active material was 5 μm, and the thickness of the first positive electrode active material layer was 7 μm.
Example 43
The procedure of example 32 was repeated, except that in < preparation of positive electrode >, dv99 of the first positive electrode active material was 7 μm, and the thickness of the first positive electrode active material layer was 9 μm.
Example 44
The same as example 32 was repeated except that in < preparation of positive electrode >, dv99 of the first positive electrode active material was 9 μm, and the thickness of the first positive electrode active material layer was 11 μm.
Example 45
The procedure of example 32 was repeated, except that in < preparation of positive electrode >, dv99 of the first positive electrode active material was 11 μm, and the thickness of the first positive electrode active material layer was 13 μm.
Example 46
The same as example 32 was repeated except that in < preparation of positive electrode >, dv99 of the first positive electrode active material was 13 μm, and the thickness of the first positive electrode active material layer was 15 μm.
Example 47
The procedure of example 32 was repeated, except that in < preparation of positive electrode >, dv99 of the first positive electrode active material was 15 μm, and the thickness of the first positive electrode active material layer was 17 μm.
Example 48
The procedure of example 32 was repeated, except that in < preparation of positive electrode >, dv99 of the first positive electrode active material was 17 μm, and the thickness of the first positive electrode active material layer was 19 μm.
Example 49
The same as example 32 was repeated except that in < preparation of positive electrode >, dv99 of the first positive electrode active material was 19 μm, and the thickness of the first positive electrode active material layer was 19.5 μm.
Example 50
The same as example 32 was repeated except that in < preparation of positive electrode >, dv99 of the first positive electrode active material was 19.9 μm, and the thickness of the first positive electrode active material layer was 20 μm.
Example 51
The same as example 32 except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 96.7wt%, 0.7wt% of the nanoparticle conductive carbon, and 0.5wt% of the carbon nanotubes were replaced with 0.1wt% of the network graphite fibers.
Example 52
The procedure of example 32 was repeated, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 96.3wt% and the content of nanoparticle conductive carbon was 0wt%.
Example 53
The same procedure as in example 32 was repeated, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 96.2wt% and the content of nanoparticle conductive carbon was 0.1 wt%.
Example 54
The same procedure as in example 32 was repeated, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 96wt% and the content of nanoparticle conductive carbon was 0.3 wt%.
Example 55
The same procedure as in example 32 was repeated, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 95.4wt% and the content of nanoparticle conductive carbon was 0.9 wt%.
Example 56
The same procedure as in example 32 was repeated, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 95.2wt% and the content of nanoparticle conductive carbon was 1.1 wt%.
Example 57
The same procedure as in example 32 was repeated, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 95wt% and the content of nanoparticle conductive carbon was 1.3 wt%.
Example 58
The procedure was repeated as in example 32 except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 94.8wt% and the content of nanoparticle conductive carbon was 1.5 wt%.
Example 59
The procedure of example 32 was repeated, except that in < preparation of positive electrode >, lithium manganese iron phosphate was contained in an amount of 96wt%, conductive carbon of nanoparticles was contained in an amount of 0.5wt%, and carbon nanotubes were contained in an amount of 0.3 wt%.
Example 60
The same procedure as in example 32 was repeated, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 95.8wt% and the content of nanoparticle conductive carbon was 0.5 wt%.
Example 61
The same procedure as in example 32 was repeated, except that in < preparation of positive electrode >, the content of the nanoparticle conductive carbon was 0.5wt% and the content of the carbon nanotube was 0.7 wt%.
Example 62
The procedure of example 32 was repeated, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 95.4wt%, the content of nanoparticle conductive carbon was 0.5wt%, and the content of carbon nanotubes was 0.9 wt%.
Example 63
The procedure of example 32 was repeated, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 95.2wt%, the content of nanoparticle conductive carbon was 0.5wt%, and the content of carbon nanotubes was 1.1 wt%.
Example 64
The same as example 32 was repeated, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 95.3wt%, 0.7wt% of the nanoparticle conductive carbon, and 0.5wt% of the carbon nanotubes were replaced with 1.5wt% of the nanoparticle conductive carbon.
Example 65
The procedure was repeated as in example 64, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 94.8wt% and the content of nanoparticle conductive carbon was 2.0 wt%.
Example 66
The procedure of example 64 was repeated, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 86.8wt%, the content of nanoparticle conductive carbon was 5.0wt%, and the content of the first binder was 8 wt%.
Example 67
The procedure of example 64 was repeated, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 79.8wt%, the content of nanoparticle conductive carbon was 10.0wt%, and the content of the first binder was 10wt%.
Example 68
The procedure of example 64 was repeated, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 71.8wt%, the content of nanoparticle conductive carbon was 15.0wt%, and the content of the first binder was 13 wt%.
Example 69
The same as example 32 was repeated, except that in < preparation of positive electrode >, the lithium manganese iron phosphate content was 59.8wt%, the nanoparticle conductive carbon content was 15wt%, the carbon nanotube content was 5wt%, and the first binder content was 20 wt%.
Example 70
The procedure was as in example 32 except that in < preparation of positive electrode >, polyethoxypropoxypropene hydrocarbon was replaced with sodium polycarboxylate.
Example 71
The same as in example 32 was repeated, except that in < preparation of positive electrode >, polyethoxypropropylene hydrocarbon was replaced with polysiloxane.
Example 72
The procedure of example 32 was repeated, except that in < preparation of positive electrode >, polyethoxypropoxypropylene hydrocarbon was replaced with polymethyl acrylate.
Example 73
The same as example 32 was repeated, except that in < preparation of positive electrode >, polyethoxypropypropylene hydrocarbon was replaced with polypropylene alcohol.
Example 74
The procedure was as in example 32, except that in < preparation of positive electrode >, polyethoxypropoxyalkene was replaced with polyethylene glycol ether.
Example 75
The procedure was repeated as in example 32 except that in < preparation of positive electrode >, the content of lithium iron manganese phosphate was 95.79% by weight and the content of polyethoxypropoxypropylene was 0.01% by weight.
Example 76
The procedure was repeated as in example 32 except that in < preparation of positive electrode >, the content of lithium iron manganese phosphate was 95.75% by weight and the content of polyethoxypropoxypropylene was 0.05% by weight.
Example 77
The procedure was repeated as in example 32 except that in < preparation of positive electrode >, the content of lithium iron manganese phosphate was 95.7% by weight and the content of polyethoxypropoxypropylene was 0.1% by weight.
Example 78
The procedure was repeated as in example 32 except that in < preparation of positive electrode >, the content of lithium iron manganese phosphate was 95.5% by weight and the content of polyethoxypropoxypropylene was 0.3% by weight.
Example 79
The procedure was repeated as in example 32 except that in < preparation of positive electrode >, the content of lithium iron manganese phosphate was 95.3% by weight and the content of polyethoxypropoxypropylene was 0.5% by weight.
Example 80
The procedure was repeated as in example 32 except that in < preparation of positive electrode >, the content of lithium iron manganese phosphate was 95% by weight and the content of polyethoxypropoxypropylene was 0.8% by weight.
Example 81
The procedure was repeated as in example 70 except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 94.8% by weight and the content of sodium polycarboxylate was 1% by weight.
Example 82
The procedure of example 70 was repeated, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 92.7wt%, the content of carbon nanotubes was 0.6wt%, and the content of sodium polycarboxylate was 3wt%.
Example 83
The procedure was repeated as in example 70 except that in < preparation of positive electrode >, lithium iron manganese phosphate was contained in an amount of 90.6wt%, carbon nanotubes were contained in an amount of 0.7wt%, and sodium polycarboxylate was contained in an amount of 5 wt%.
Example 84
The procedure of example 73 was repeated, except that in < preparation of positive electrode >, the content of lithium manganese iron phosphate was 87.5wt%, the content of carbon nanotubes was 0.8wt%, and the content of polyvinyl alcohol was 8 wt%.
Example 85
The procedure of example 73 was repeated, except that in < preparation of positive electrode >, lithium manganese iron phosphate was contained in an amount of 85.4wt%, carbon nanotubes were contained in an amount of 0.9wt%, and polyvinyl alcohol was contained in an amount of 10wt%.
Example 86
The procedure was repeated as in example 51 except that in < preparation of positive electrode >, the content of lithium iron manganese phosphate was 98.89% by weight and the content of polyethoxypropoxypropylene was 1% by weight.
Example 87
The procedure was repeated as in example 69, except that in < preparation of positive electrode >, the content of lithium iron manganese phosphate was 50% by weight and the content of polyethoxypropoxypropylene was 20% by weight.
Example 88
The procedure was carried out in the same manner as in example 78 except that in < preparation of insulating layer slurry >, the inorganic particle content was 84.99% by weight and the leveling agent content was 0.2% by weight.
Example 89
The procedure of example 88 was repeated, except that in < preparation of second adhesive >, acrylonitrile multipolymer was used as the second adhesive.
Example 90
The procedure of example 88 was repeated, except that sodium carboxymethylcellulose was used as the second binder in the < preparation of second binder >.
Example 91
The procedure of example 88 was repeated, except that sodium polyacrylate was used as the second binder in < preparation of second binder >.
Example 92
The procedure of example 88 was repeated, except that polyacrylamide was used as the second binder in < preparation of second binder >.
Example 93
Except that in < preparation of second binder >: replacing methyl acrylate monomer with monomer acrylamide at a mass ratio of 40: 60: sodium acrylate, in < preparation of positive electrode >: the same as in example 88 was repeated except that the coverage of the insulating layer was 96%.
Example 94
Except that in < preparation of second binder >: replacing methyl acrylate monomer with monomer acrylonitrile with the mass ratio of 40: 60: acrylamide, in < preparation of positive electrode >: the procedure of example 88 was repeated except that the coverage of the insulating layer was 97%.
Example 95
Except that in < preparation of second binder >: replacing methyl acrylate monomer with monomer acrylonitrile with the mass ratio of 40: 60: sodium acrylate, in < preparation of positive electrode >: the same as in example 88 was repeated except that the coverage of the insulating layer was 97%.
Example 96
Except that in < preparation of second binder >: replacing methyl acrylate monomer with monomer acrylonitrile with the mass ratio of 27: 60: 10: 3: sodium acrylate: acrylamide: acrylate, in < preparation of positive electrode >: the same as in example 88 was repeated except that the coverage of the insulating layer was 97%.
Example 97
Except that in < preparation of second binder >: replacing a methyl acrylate monomer with a monomer acrylonitrile with a mass ratio of 30: 60: 10: sodium acrylate: acrylamide, in < preparation of positive electrode >: the same as example 88 was repeated except that the coverage of the insulating layer was 99%.
Example 98
Except that in < preparation of second binder >: replacing methyl acrylate monomer with monomer acrylonitrile with the mass ratio of 30: 10: 60: sodium acrylate: acrylamide, in < preparation of positive electrode >: the procedure of example 88 was repeated except that the coverage of the insulating layer was 99%.
Example 99
Except that in < preparation of second binder >: replacing methyl acrylate monomer with acrylonitrile monomer at a mass ratio of 40: 50: 10: sodium acrylate: acrylamide, in < preparation of positive electrode >: the procedure of example 88 was repeated except that the coverage of the insulating layer was 99%.
Example 100
Except that in < preparation of second binder >: replacing methyl acrylate monomer with acrylonitrile monomer in a mass ratio of 40: 10: 50: sodium acrylate: acrylamide, in < preparation of positive electrode >: the procedure of example 88 was repeated except that the coverage of the insulating layer was 99%.
Example 101
Except that in < preparation of second binder >: replacing methyl acrylate monomer with monomer acrylonitrile in a mass ratio of 45: 10: sodium acrylate: acrylamide, in < preparation of positive electrode >: the same as example 88 was repeated except that the coverage of the insulating layer was 99%.
Example 102
Except that in < preparation of second binder >: replacing methyl acrylate monomer with acrylonitrile monomer at a mass ratio of 45: 10: 45: sodium acrylate: acrylamide, in < preparation of positive electrode >: the procedure of example 88 was repeated except that the coverage of the insulating layer was 99%.
Example 103
Except that in < preparation of second binder >: replacing methyl acrylate monomer with monomer acrylonitrile with the mass ratio of 50: 40: 10: sodium acrylate: acrylamide, in < preparation of positive electrode >: the same as example 88 was repeated except that the coverage of the insulating layer was 99%.
Example 104
Except that in < preparation of second binder >: replacing methyl acrylate monomer with monomer acrylonitrile with the mass ratio of 50: 10: 40: sodium acrylate: acrylamide, in < preparation of positive electrode >: the same as example 88 was repeated except that the coverage of the insulating layer was 99%.
Example 105
Except that in < preparation of second binder >: replacing methyl acrylate monomer with acrylonitrile monomer with the mass ratio of 55: 35: 10: sodium acrylate: acrylamide, in < preparation of positive electrode >: the same as example 88 was repeated except that the coverage of the insulating layer was 99%.
Example 106
Except that in < preparation of second binder >: replacing methyl acrylate monomer with acrylonitrile monomer with the mass ratio of 55: 10: 35: sodium acrylate: acrylamide, in < preparation of positive electrode >: the same as example 88 was repeated except that the coverage of the insulating layer was 99%.
Example 107
Except that in < preparation of second binder >: replacing methyl acrylate monomer with monomer acrylonitrile with the mass ratio of 60: 30: 10: sodium acrylate: acrylamide, in < preparation of positive electrode >: the procedure of example 88 was repeated except that the coverage of the insulating layer was 99%.
Example 108
Except that in < preparation of second binder >: replacing methyl acrylate monomer with monomer acrylonitrile with the mass ratio of 60: 10: 30: sodium acrylate: acrylamide, in < preparation of positive electrode >: the procedure of example 88 was repeated except that the coverage of the insulating layer was 99%.
Example 109
Except that in < preparation of second binder >: replacing methyl acrylate monomer with monomer acrylonitrile with the mass ratio of 70: 20: 10: sodium acrylate: acrylamide, in < preparation of positive electrode >: the same as example 88 was repeated except that the coverage of the insulating layer was 99%.
Example 110
Except that in < preparation of second binder >: replacing methyl acrylate monomer with monomer acrylonitrile with the mass ratio of 70: 10: 20: sodium acrylate: acrylamide, in < preparation of positive electrode >: the same as example 88 was repeated except that the coverage of the insulating layer was 99%.
Example 111
The procedure of example 101 was repeated, except that in the preparation of insulating layer slurry, the second binder content was 50wt%, the inorganic particles content was 49.8wt%, and the coverage of the insulating layer was 95%.
Example 112
The procedure was carried out in the same manner as in example 101 except that in < preparation of insulating layer slurry >, the content of the second binder was 40wt%, the content of the inorganic particles was 59.8wt%, and the coverage of the insulating layer was 95%.
Example 113
The procedure of example 101 was repeated, except that in the preparation of insulating layer slurry, the second binder content was 30wt%, the inorganic particles content was 69.8wt%, and the coverage of the insulating layer was 95%.
Example 114
The procedure of example 101 was repeated, except that in the preparation of insulating layer slurry, the second binder content was 25wt%, the inorganic particles content was 74.8wt%, and the coverage of the insulating layer was 97%.
Example 115
The procedure was carried out in the same manner as in example 101 except that in < preparation of insulating layer slurry >, the content of the second binder was 20% by weight, the content of the inorganic particles was 79.8% by weight, and the coverage of the insulating layer was 99%.
Example 116
The procedure was carried out in the same manner as in example 101 except that in < preparation of insulating layer slurry >, the content of the second binder was 10% by weight, the content of the inorganic particles was 89.8% by weight, and the coverage of the insulating layer was 99%.
Example 117
The procedure was carried out in the same manner as in example 101 except that in < preparation of insulating layer slurry >, the content of the second binder was 5% by weight, the content of the inorganic particles was 94.8% by weight, and the coverage of the insulating layer was 96%.
Example 118
The procedure of example 101 was repeated, except that in < preparation of insulating layer slurry >, the content of the second binder was 2wt%, the content of the inorganic particles was 97.99wt%, the content of the leveling agent was 0.01wt%, and the coverage of the insulating layer was 95%.
Example 119
The procedure of example 101 was repeated, except that in the preparation of insulating layer slurry, the content of the second binder was 5wt%, the content of the inorganic particles was 94.9wt%, the content of the leveling agent was 0.1wt%, and the coverage of the insulating layer was 92%.
Example 120
The procedure of example 101 was repeated, except that in < preparation of insulating layer slurry >, the content of the second binder was 25wt%, the content of the inorganic particles was 72wt%, the content of the leveling agent was 3wt%, and the coverage of the insulating layer was 94%.
Example 121
The procedure of example 101 was repeated, except that in the preparation of insulating layer slurry, the second binder content was 45wt%, the inorganic particle content was 50wt%, the leveling agent content was 5wt%, and the coverage of the insulating layer was 93%.
Example 122
The procedure of example 111 was repeated, except that in the preparation of insulating layer slurry, the content of inorganic particles was 40wt%, the content of a leveling agent was 10wt%, and the coverage of the insulating layer was 90%.
Example 123
The procedure was as in example 101 except that boehmite was replaced with diaspore in < preparation of insulating layer slurry >.
Example 124
The procedure was as in example 101 except that in < preparation of insulating layer slurry >, boehmite was replaced with alumina.
Example 125
The procedure was as in example 101 except that in < preparation of insulating layer slurry >, boehmite was replaced with barium sulfate.
Example 126
The procedure was as in example 101 except that in < preparation of insulating layer slurry >, boehmite was replaced with calcium sulfate.
Example 127
The procedure was as in example 101 except that in < preparation of insulating layer slurry >, boehmite was replaced with calcium silicate.
Comparative example 1
The same procedure as in example 1 was repeated, except that in < preparation of first binder >, the monomer sodium acrylate was replaced with vinylidene fluoride, and in < preparation of positive electrode >, the content of first binder was 5 wt%.
Comparative example 2
The procedure of example 1 was repeated, except that lithium iron phosphate in < preparation of positive electrode > was replaced with lithium cobaltate.
Comparative example 3
Except that in < preparation of positive electrode >, the content of lithium iron phosphate was 71.8wt%, 0.7wt% of nanoparticle conductive carbon, and 0.5wt% of carbon nanotubes were replaced with 25wt% of nanoparticle conductive carbon, the same was as in example 1.
Comparative example 4
The same as in example 78 was conducted except that the insulating layer was not contained.
Comparative example 5
Except that in < preparation of second binder >: the second binder is polyvinylidene fluoride, and in the preparation of the insulating layer slurry: the procedure of example 124 was repeated except that the coverage of the insulating layer was 90%.
The preparation parameters and test results of each example and comparative example are shown in tables 1 to 3 below.
TABLE 1 preparation parameters and test results for examples 1-31 and comparative example 1
Figure BDA0003383057710000331
Figure BDA0003383057710000341
Figure BDA0003383057710000351
Figure BDA0003383057710000361
Figure BDA0003383057710000371
Figure BDA0003383057710000381
Figure BDA0003383057710000391
Figure BDA0003383057710000401
Figure BDA0003383057710000411
Figure BDA0003383057710000421
Figure BDA0003383057710000431
Figure BDA0003383057710000441
Figure BDA0003383057710000451
Figure BDA0003383057710000461
Figure BDA0003383057710000471
As can be seen from examples 1 to 31 and comparative example 1, in the lithium ion battery in which the first active material layer contains the first binder of the present application and the binder content is within the range defined in the present application, the binding force between the first active material layer and the current collector is significantly improved, and in particular, in examples 27 and 28, the binding force between the first active material layer and the current collector is up to 310N/m or more, the resistance of the positive electrode after the lithium ion battery is fully charged is improved, the nail penetration test passing rate is significantly improved, and the safety of the lithium ion battery can be effectively improved.
It can be seen from examples 32 to 87 and comparative examples 2 to 3 that by controlling the components and Dv99 of the first active material, the components and content of the conductive agent, and the components and content of the leveling agent, the resistance of the positive electrode after the lithium ion battery is fully charged is improved, the nail penetration test passing rate of the lithium ion battery is obviously improved, and the safety of the lithium ion battery can be effectively improved.
It can be seen from examples 88 to 127 and comparative examples 4 to 5 that the adhesion between the insulating layer and the current collector of the lithium ion battery having the insulating layer of the present application is significantly improved by controlling the second binder component and content, the inorganic particle component and content, and the leveling agent component and content, especially in examples 101 to 106, the adhesion between the insulating layer and the current collector of the lithium ion battery reaches more than 350N/m, and the nail penetration test throughput of the lithium ion battery is significantly improved, which can effectively improve the safety of the lithium ion battery.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims (16)

1. An electrochemical device comprising a positive electrode, the positive electrode comprising:
a current collector;
a first active material layer including a first active material, a first binder, and a conductive agent; and a second active material layer including a second active material;
the second active material layer is arranged on at least one surface of the current collector, and the first active material layer is arranged between the current collector and the second active material layer;
wherein the first binder comprises a copolymer formed by polymerization of an acrylate salt, acrylamide, and acrylonitrile; the mass percent of the acrylonitrile is 40-60%, the mass percent of the acrylate is 10-50%, and the mass percent of the acrylamide is 10-50% based on the total mass of the copolymer;
the resistance of the positive electrode after the electrochemical device is fully charged is more than 10 omega; the adhesion between the first active material layer and the current collector is 201N/m or more.
2. The electrochemical device according to claim 1, wherein the first active material layer further includes a leveling agent including at least one of a polymer of an olefin derivative, a carboxylate-based polymer, a siloxane-based polymer, an acrylate-based polymer, an alcohol-based polymer, or an ether-based polymer.
3. The electrochemical device according to claim 2, wherein the first active material layer has a content of the first active material of 50wt% to 98.89wt%, a content of the first binder of 1wt% to 20wt%, a content of the conductive agent of 0.1wt% to 20wt%, and a content of the leveling agent of 0.01wt% to 10wt%.
4. The electrochemical device according to claim 1, wherein Dv99 of the first active material is 0.01 μm to 19.9 μm.
5. The electrochemical device according to claim 1, wherein the first active material layer has a monolayer thickness of 0.04 μm to 20 μm, and the second active material layer has a monolayer thickness of 20 μm to 200 μm.
6. The electrochemical device according to claim 2, wherein the current collector includes a coated region where the first and second active materials are provided, and an uncoated region where the first and second active materials are not provided; the uncoated zone is at least partially provided with an insulating layer.
7. The electrochemical device according to claim 6, wherein the adhesion between the insulating layer and the positive electrode current collector is 201N/m or more.
8. The electrochemical device of claim 6, wherein the coverage of the insulating layer is 90% to 100%.
9. The electrochemical device according to claim 6, wherein the insulating layer further comprises inorganic particles, a second binder, and the leveling agent;
the inorganic particles comprise at least one of boehmite, diaspore, alumina, barium sulfate, calcium sulfate, or calcium silicate;
the second binder comprises at least one of copolymer of propylene derivative, polyacrylate, acrylonitrile multipolymer, carboxymethyl cellulose salt or nitrile rubber.
10. The electrochemical device according to claim 9, wherein the content of the inorganic particles in the insulating layer is 40 to 97.99wt%, the content of the binder is 2 to 50wt%, and the content of the leveling agent is 0.01 to 10wt%.
11. The electrochemical device according to claim 6, wherein the insulating layer has a thickness of 0.02 to 10 μm.
12. The electrochemical device of claim 10, wherein the electrochemical device satisfies at least one of the following characteristics:
(a) The resistance of the positive electrode after the electrochemical device is fully charged is 30-100 omega;
(c) The leveling agent comprises at least one of a sodium carboxylate polymer, an oxygen-containing propylene olefin polymer or polysiloxane;
(d) The inorganic particles comprise at least one of boehmite or alumina;
(e) The second binder comprises at least one of a propylene-based polymer or a nitrile rubber;
(f) The content of the inorganic particles in the insulating layer is 72wt% to 94.9wt%, the content of the binder is 5wt% to 25wt%, and the content of the leveling agent is 0.1wt% to 3wt%.
13. The electrochemical device according to claim 2, wherein the leveling agent includes at least one of polyethoxypropoxyalkene, polysiloxane, polymethyl acrylate, polyethylene glycol, sodium polycarboxylate, or polyallyl alcohol.
14. An electronic device comprising the electrochemical device of any one of claims 1 to 13.
15. A method of making the electrochemical device of any one of claims 1 to 13, comprising:
mixing a first active material, a first binder, a conductive agent and a solvent to obtain first active material layer slurry;
coating the first active material layer slurry on a current collector, and drying to obtain a first active material layer;
mixing a second active material, a binder, a conductive agent and a solvent to obtain second active material layer slurry;
coating the second active material layer slurry on the first active material layer, and drying to obtain a positive electrode;
and sequentially stacking the anode, the isolating membrane and the cathode, winding to obtain an electrode assembly, packaging the electrode assembly into a packaging bag, and packaging to obtain the electrochemical device.
16. A method of making an electrochemical device according to claim 15, further comprising: an insulating layer is coated on the uncoated region of the current collector.
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