WO2022141473A1

WO2022141473A1 - Electrochemical device, electronic device, and preparation method for electrochemical device

Info

Publication number: WO2022141473A1
Application number: PCT/CN2020/142323
Authority: WO
Inventors: 刘晓欠
Original assignee: 东莞新能源科技有限公司
Priority date: 2020-12-31
Filing date: 2020-12-31
Publication date: 2022-07-07
Also published as: CN113939927B; CN113939927A

Abstract

An electrochemical device, an electronic device, and a preparation method for the electrochemical device. The electrochemical device comprises a positive electrode comprising a current collector (10). At least one surface of the current collector (10) is provided with a second active substance layer (22), and a first active substance layer (21) is arranged between the current collector (10) and the second positive electrode active substance layer (22). The first active substance layer (21) comprises a first active substance, a first binder and a conductive agent, wherein the first binder comprises a copolymer formed by the polymerization of an acrylate, acrylamide and acrylonitrile. The first binder has a low swelling rate, which can ensure a good binding force between the first active substance layer (21) and the current collector (10). The electrochemical device has good pass rates in a nail penetration test and an impact test, and can effectively improve the safety of the electrochemical device.

Description

Electrochemical device, electronic device and method for preparing electrochemical device

technical field

The present application relates to the field of electrochemistry, in particular to an electrochemical device, an electronic device and a method for preparing the electrochemical device.

Background technique

Lithium-ion batteries have the advantages of high energy storage density, high open circuit voltage, low self-discharge rate, long cycle life, and good safety performance. They are widely used in various fields such as electrical energy storage, mobile electronic equipment, electric vehicles, and aerospace equipment. With the rapid development of mobile electronic devices and electric vehicles, the market has put forward higher and higher requirements for the energy density, safety performance, cycle performance and service life of lithium-ion secondary batteries, among which safety performance is particularly important.

At present, during the use of lithium-ion batteries, safety accidents still occur due to external impact or puncture, which hinders the wide application of lithium-ion batteries. Therefore, there is an urgent need for a technical means that can further improve the safety performance of lithium-ion batteries.

SUMMARY OF THE INVENTION

The purpose of the present application is to provide an electrochemical device, an electronic device and a method for preparing the electrochemical device, so as to improve the safety performance of the electrochemical device.

It should be noted that, in the following content, 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 solutions are as follows:

A first aspect of the present application provides an electrochemical device including a positive electrode, the positive electrode comprising: a current collector; a first active material layer, the first active material layer comprising a first active material, a first binder and a conductive agent and a second active material layer, the second active material layer includes a second active material; at least one surface of the current collector is provided with a second active material layer, and the first active material layer is provided on the current collector and the second active material layer between;

Wherein, the first binder includes a copolymer formed by the polymerization of acrylate, acrylamide and acrylonitrile.

In one embodiment of the present application, the first binder comprises a copolymer formed by the polymerization of acrylate, acrylamide, and acrylonitrile. The copolymer was soaked in the electrolyte at 85°C for 24 hours or at 25°C for 7 days, and the swelling rate was less than 5%, so that the first active material layer and the current collector, or the first active material layer and the second active material layer had Good adhesion.

In this application, the weight average molecular weight of the first binder is not particularly limited, as long as the purpose of the application can be achieved. For example, the weight average molecular weight of the first binder can be 100,000 to 2,000,000, preferably 300,000 to 800,000. .

In the present application, "swelling" refers to the phenomenon in which the above-mentioned polymer expands in volume in the electrolyte. Swelling rate=(volume after soaking-volume before soaking)/volume before soaking×100%.

In the present application, a second active material layer is disposed on at least one surface of the current collector, and the first active material layer is disposed between the current collector and the second active material layer. It should be noted that the "surface" here can be the entire area of the current collector surface or a partial area of the current collector surface, which is not particularly limited in this application, as long as the purpose of the application can be achieved.

By arranging the first active material layer between the current collector and the second active material layer, metal burrs that may be generated in the current collector can be wrapped under abnormal conditions such as nail penetration and impact, so as to effectively prevent the short circuit in the lithium ion battery. At the same time, the thermal runaway caused by the local overheating of the lithium-ion battery can be prevented, thereby avoiding the overheating and burning of the lithium-ion battery and improving its safety.

In general, the electrochemical device provided by the present application includes a positive electrode, and the positive electrode includes: a current collector, at least one surface of the current collector is provided with a second active material layer, and the first active material layer is provided on the current collector and the second active material layer. between layers of matter. Wherein, the first active material layer includes a first active material, a first binder and a conductive agent, and the first binder includes a copolymer formed by polymerization of acrylonitrile, acrylate and acrylamide. The swelling rate of the first binder is small, which can ensure good adhesion between the first active material layer and the current collector. During the nail penetration test or the impact test, the first active material layer adheres to the surface of the current collector , increase contact resistance, reduce temperature rise and safety risks, and improve the pass rate of nail penetration test and impact test, thereby effectively improving the safety of lithium-ion batteries.

In one embodiment of the present application, the resistance of the positive electrode after the electrochemical device is fully charged is 10Ω or more, preferably 30Ω to 100Ω. Controlling the positive electrode resistance within the above-mentioned range can increase the internal resistance of the lithium-ion battery when it is short-circuited, reduce the short-circuit current, and reduce the temperature rise, thereby improving the safety of the lithium-ion battery.

In an embodiment of the present application, based on the total mass of the above copolymer, the mass percentage content of acrylonitrile is 1% to 70%, the mass percentage content of acrylate is 1% to 70%, and the mass percentage of acrylamide is 1% to 70%. The percentage is from 1% to 70%. Preferably, based on the total mass of the above copolymer, the mass percentage content of acrylonitrile is 10% to 70%, the mass percentage content of acrylate is 10% to 70%, and the mass percentage content of acrylamide is 10% to 70%. 70%. More preferably, based on the total mass of the copolymer, the mass percentage content of acrylonitrile is 40% to 60%, the mass percentage content of acrylate is 10% to 50%, and the mass percentage content of acrylamide is 10% to 50%. 50%. By controlling the acrylonitrile, acrylate and acrylamide within the above-mentioned range of the total mass of the copolymer, the first adhesive can have better cohesive force in use.

In an embodiment of the present application, the first active material layer further includes a leveling agent, and the leveling agent may include polymers of olefin derivatives, carboxylate polymers, siloxane polymers, alkenoic acid At least one of ester-based polymers, alcohol-based polymers, ether-based polymers, and the like. Preferably, the leveling agent may include at least one of sodium carboxylate polymer, oxygen-containing propylene olefin polymer, polysiloxane, and the like. For example, the leveling agent may include at least one of polyethoxypropoxypropene, polysiloxane, polymethyl acrylate, polyethylene glycol, sodium polycarboxylate, polyacryl alcohol, and the like. Adding a leveling agent to the first active material layer can reduce the surface tension of the first active material, increase its leveling, improve the wettability, spreading and leveling of the first active material on the surface of the current collector, and reduce the first active material. The probability of leakage of the active material layer to the current collector enables the first active material to be uniformly coated on the current collector, thereby optimizing the safety performance of the lithium-ion battery.

In the present application, the weight-average molecular weight of the leveling agent is not particularly limited, as long as the purpose of the present application can be achieved. For example, the weight-average molecular weight of the leveling agent may not be higher than 50,000.

In an 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%, and the content of the conductive agent The content of the leveling agent is 0.1 wt % to 20 wt %, and the content of the leveling agent is 0.01 wt % to 10 wt %.

By controlling the contents of the first active material, the first binder, the conductive agent and the leveling agent in the first active material layer within the above range, the adhesion between the first active material layer and the current collector can be ensured, and the The first active material can be uniformly distributed on the first active material layer, thereby reducing the temperature rise of the lithium ion battery, improving the safety and reliability, and improving the pass rate of the piercing test and the impact test of the lithium ion battery.

In one embodiment of the present application, the conductive agent is not particularly limited, as long as the purpose of the present application can be achieved. A sort of. Preferably, the conductive agent may comprise at least one of graphene, reticulated graphite fibers, carbon nanotubes, Ketjen black, graphite fibers or nanoparticle conductive carbon, and the like. By adding a conductive agent to the first active material layer, the migration rate of lithium ions in the first active material can be effectively improved, thereby improving the charging and discharging efficiency of the lithium ion battery.

In one embodiment of the present application, the Dv99 of the first active substance is 0.01 μm to 19.9 μm. By controlling the Dv99 of the first active material to be within the above range, the flatness of the first active material layer can be improved; it is advisable that the Dv99 of the first active material does not exceed the thickness of the first active material layer, otherwise, it is easy to be difficult during the cold pressing process. The aluminum foil is stabbed to form concave and convex points that exceed the thickness of the target first active material layer.

In an embodiment of the present application, the single-layer thickness of the first active material layer is 0.04 μm to 20 μm. 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 an embodiment of the present application, the single-layer thickness of the second active material layer is 20 μm to 200 μm. When the thickness of the second active material layer is too low, for example, less than 20 μm, under the condition of a certain capacity, the lithium The ion battery has energy density and is not easy to process; when the thickness of the second active material layer is too high, eg above 200 μm, the kinetics of the lithium ion battery is deteriorated.

In one embodiment of the present application, the adhesive force between the first active material layer and the current collector is 201 N/m or more, it can be seen that the first active material layer of the present application and the current collector have excellent adhesive properties, which can Effectively improve the pass rate of the piercing test of lithium-ion batteries.

In one embodiment of the present application, the current collector includes a coated area provided with the first active material and the second active material, and an uncoated area without the first active material and the second active material; uncoated The region is at least partially provided with an insulating layer. Through the arrangement of the insulating layer, the insulating performance of the region where the insulating layer is coated in the present application can be improved, thereby improving the safety performance of the lithium ion battery. In the electrochemical device of the present application, an insulating layer may be disposed at least partially in the above-mentioned uncoated area, and different disposition methods may be adopted, for example, including but not limited to: disposing the insulating layer on two lengthwise directions of the positive electrode. The insulating layer is provided on the starting end side of the positive electrode, and the insulating layer is provided on the trailing end side of the positive electrode. The above setting methods can be used individually or in combination. The starting end and the ending end may refer to the starting end and ending end of the winding structure in the lithium ion battery of the winding structure.

In an embodiment of the present application, the adhesive force between the insulating layer and the current collector is above 201 N/m. It can be seen that the insulating layer and the current collector of the present application have excellent adhesive properties, thereby reducing the thickness of the lithium ion battery. growth rate and internal resistance growth rate.

In one embodiment of the present application, the coverage of the insulating layer is 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 above-mentioned inorganic particles may include at least one of boehmite, diaspore, alumina, barium sulfate, calcium sulfate or calcium silicate, etc.; preferably, the inorganic particles may include at least one of boehmite or alumina, etc. kind. The addition of inorganic particles can improve the strength and insulating properties of the insulating layer.

The above-mentioned second binder may include at least one of propylene derivative copolymers, polyacrylates, acrylonitrile multipolymers, carboxymethyl cellulose salts or nitrile rubber, etc.; preferably, the second binder The agent may include at least one of acrylic polymer or nitrile rubber. The swelling ratio of the second binder in the electrolyte is small and maintains a high cohesive force.

In this application, the weight average molecular weight of the second binder is not particularly limited, as long as the purpose of the application can be achieved. For example, the weight average molecular weight of the second binder can be 100,000 to 2,000,000, preferably 300,000 to 800,000. .

In an embodiment of the present application, the content of the inorganic particles in the insulating layer is 40wt% to 97.99wt%, the content of the second binder is 2wt% to 50wt%, and the content of the leveling agent is 0.01wt% to 10wt% . Preferably, the content of 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 content of the inorganic particles, the second binder and the leveling agent in the insulating layer to be within the above ranges, the insulating layer can be uniformly coated on the current collector of the positive electrode, thereby improving the strength of the insulating layer and the bonding between the insulating layer and the current collector. Adhesion, thereby improving the safety performance of lithium-ion batteries.

In one embodiment of the present application, the thickness of the insulating layer is 0.02 μm to 10 μm. When the thickness of the insulating layer is less than 0.02 μm, the strength of the insulating layer is too low, and it is easy to break, which affects the insulating performance of the area; when the thickness of the insulating layer is greater than 10 μm, the insulating layer is too thick, which will affect the energy density of lithium-ion batteries.

The preparation method of the first binder of the present application is not particularly limited, and a preparation method known to those skilled in the art can be adopted, for example, the following preparation method can be adopted:

Distilled water was added to the reactor, stirring was started, and after nitrogen was introduced to remove oxygen, at least one of the above-mentioned components such as acrylonitrile, acrylate and acrylamide was added in different mass ratios, heated to about 65°C under an inert atmosphere, and the Constant temperature, and then adding an initiator to initiate the reaction, the reaction ends after about 20 hours.

There is no particular limitation on the initiator in the present application, as long as it can initiate the polymerization of the monomer, for example, it can be a 20% ammonium persulfate solution. There are no particular restrictions on the added amounts of distilled water and initiator in the present application, as long as the added monomers can be guaranteed to undergo a polymerization reaction. After the reaction, an alkaline solution is added to the reacted precipitate for neutralization to make the pH value 6.5 to 9. Then, the reaction product is filtered, washed, dried, pulverized, sieved and the like.

Those skilled in the art should understand 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 material layer. The insulating layer of the present application may be provided on at least one surface of the positive electrode, 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 can be a current collector known in the art, such as aluminum foil, aluminum alloy foil, or composite current collector. The first active material layer includes a first active material, and the second active material layer includes a second active material. In this application, the first active material and the second active material may be the same or different. The active material is not particularly limited, and active materials known in the art can be used. For example, each independently includes nickel cobalt lithium manganate (811, 622, 523, 111), nickel cobalt lithium aluminate, lithium iron phosphate, lithium rich manganese At least one of base material, lithium cobaltate, lithium manganate, 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 purpose of the present application can be achieved, 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 purpose of the present application can be achieved. For example, a negative electrode typically includes a current collector and an active material layer. In the present application, the current collector is not particularly limited, and current collectors known in the art can be used, such as copper foil, copper alloy foil, composite current collector, and the like. 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 microspheres, silicon, silicon carbon, silicon oxide, soft carbon, hard carbon, lithium titanate or niobium titanate, and the like may be included. In the present application, the thicknesses of the current collector and active material layer of the negative electrode are not particularly limited as long as the purpose 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 located 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 purpose 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 fiber or graphene, and the like. The above-mentioned binders are not particularly limited, and binders known in the art can be used as long as the purpose 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 carboxymethyl cellulose (CMC-Na), and the like. For example, styrene-butadiene rubber (SBR) can be selected as the binder.

The lithium ion battery of the present application further includes a separator for separating the positive electrode and the negative electrode, preventing the internal short circuit of the lithium ion battery, allowing the free passage of electrolyte ions, and completing the role of the electrochemical charging and discharging process. In the present application, the separator is not particularly limited as long as the purpose of the present application can be achieved.

For example, polyethylene (PE), polypropylene (PP)-based polyolefin (PO) separator films, polyester films (such as polyethylene terephthalate (PET) films), cellulose films, polyamide Imine film (PI), polyamide film (PA), spandex or aramid film, woven film, non-woven film (non-woven fabric), microporous film, composite film, diaphragm paper, laminated film, spinning film, etc. at least one of them.

For example, the release film may include a substrate layer and a surface treatment layer. The substrate layer can be a non-woven fabric, film or composite film with a porous structure, and the material of the substrate layer can include at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, etc. kind. Optionally, polypropylene porous membranes, polyethylene porous membranes, polypropylene non-woven fabrics, polyethylene non-woven fabrics, or polypropylene-polyethylene-polypropylene porous composite membranes may be used. Optionally, at least one surface of the substrate layer is provided with a surface treatment layer, and the surface treatment layer can 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, the inorganic particles are not particularly limited, and can be selected from aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, nickel oxide, for example , at least one of zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate. The binder is not particularly limited, for example, it can be selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyethylene One or a combination of rolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene. The polymer layer contains a polymer, and the material of the polymer includes polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly( At least one of vinylidene fluoride-hexafluoropropylene) and the like.

The lithium ion battery of the present application further includes an electrolyte, and the electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolyte, and the electrolyte includes a lithium salt and a non-aqueous solvent.

In some embodiments of the present application, 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. One or more of LiC(SO ₂ CF ₃ ) ₃ , LiSiF ₆ , LiBOB and lithium difluoroborate. For example, LiPF ₆ can be chosen as the lithium salt because 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 solvents, or a combination thereof.

The above-mentioned carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof.

Examples of the above-mentioned chain carbonate compound are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), carbonic acid Methyl ethyl ester (MEC) and combinations thereof. Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), and combinations thereof. Examples of fluorocarbonate compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Ethyl carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-dicarbonate Fluoro-1-methylethylene, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof.

Examples of the above-mentioned carboxylate compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone , caprolactone, valerolactone, mevalonolactone, caprolactone, and combinations thereof.

Examples of the above ether compounds are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethyl ether Oxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.

Examples of the above-mentioned other organic solvents are dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 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, including the electrochemical device provided in the first aspect of the present application.

The electronic device of the present application is not particularly limited, and it can be used in any electronic device known in the prior art. In some embodiments, electronic devices may include, but are not limited to, notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, assisted bicycles, bicycles, Lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large-scale household storage batteries and lithium-ion capacitors, etc.

The preparation process of 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 making an electrochemical device includes:

(1) mixing the first active material, the first binder, the conductive agent and the solvent to obtain the first active material layer slurry;

(2) coating the first active material layer slurry on the current collector, and drying to obtain the first active material layer;

(3) mixing the second active material, the binder, the conductive agent and the solvent to obtain the 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) stacking the positive electrode, the separator and the negative electrode in sequence, winding to obtain an electrode assembly, putting the electrode assembly into a packaging bag, and obtaining an electrochemical device after subsequent processing.

In one embodiment of the present application, a method of making an electrochemical device includes coating an insulating layer on an uncoated region of a current collector.

For example, electrochemical devices can be manufactured by the following process: the positive electrode and the negative electrode are overlapped through a separator, and they are wound, folded, etc., as required, and placed in a case, and the electrolyte is injected into the case and sealed. In addition, if necessary, an overcurrent preventing element, a guide plate, etc. may be placed in the case to prevent pressure rise and overcharge and discharge inside the electrochemical device.

The application provides an electrochemical device and an electronic device, which include a positive electrode, the positive electrode includes a current collector, at least one surface of the current collector is provided with a second active material layer, and the first active material layer is provided on the current collector and the second active material layer. between layers of matter. The first active material layer includes a first active material, a first binder and a conductive agent, and the first binder includes a copolymer formed by polymerizing acrylate, acrylamide and acrylonitrile. The swelling ratio of the first binder is small, which can ensure good adhesion between the first active material layer and the current collector. The electrochemical device has a good pass rate of the nail penetration test and the impact test, which can effectively improve the safety of the electrochemical device.

Description of drawings

In order to illustrate the technical solutions of the present application and the prior art more clearly, the following briefly introduces the drawings required in the embodiments and the prior art. Obviously, the drawings in the following description are only for the present application. some examples.

1 is a schematic structural diagram of a positive electrode according to an embodiment of the application;

2 is a schematic structural diagram of a positive electrode of another embodiment of the application;

3 is a schematic structural diagram of a positive electrode of yet another embodiment of the application;

FIG. 4 shows the relationship between the adhesive force and the stroke in the adhesive force test of the present application.

Reference numerals: 10. Current collector, 21. First active material layer, 22. Second active material layer, 30. Insulating layer.

Detailed ways

In order to make the objectives, technical solutions, and advantages of the present application more clear, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in this application, all other technical solutions obtained by those of ordinary skill in the art belong to the scope of protection of this application.

It should be noted that, in the specific 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 diagram of a positive electrode in an embodiment of the present application. There may be uncoated areas on the left and right sides of the positive electrode, that is, areas where the first active material layer 21 and the second active material layer 22 are not provided. The fluid 10 is exposed in the uncoated area. In FIG. 1 , the insulating layer 30 may be disposed in the uncoated area, and may be disposed on both sides of the positive electrode along the length direction. Of course, the positive electrode can also be arranged only on one side along the length direction.

FIG. 2 shows a schematic structural diagram of a positive electrode in another embodiment of the present application. The A surface of the current collector 10 is provided with a first active material layer 21 and a second active material layer 22, and the A surface of the current collector 10 may be There are uncoated areas; there may be uncoated areas on the B surface of the current collector 10 . In FIG. 2 , the insulating layer 30 may be provided on both sides of the coating area along the length direction of the A surface of the current collector 10 , and the insulating layer 30 may also be provided on the B surface of the current collector 10 .

FIG. 3 shows a schematic structural diagram 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 is provided. Uncoated areas may exist. In FIG. 3 , the insulating layer 30 may be disposed on the surface B of the current collector 10 .

FIG. 4 shows the relationship between the adhesion force and the stroke of the present application in the adhesion force test.

Example

Hereinafter, the embodiment of the present application will be described more specifically with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

Test methods and equipment:

Adhesion test:

Use a high-speed iron tensile machine and a 90° angle method to test the adhesion between the insulating layer/first active material layer and the current collector: Cut the positive electrode with the insulating layer/first active material layer part in the finished lithium-ion battery as For strip samples of 20mm×60mm, the length and width can be adjusted proportionally according to the actual situation. Along the length direction of the sample, from one end of the sample, the insulating layer or a part of the first active material layer is adhered to the steel plate by double-sided tape, wherein the adhesion length is not less than 40mm; then the steel plate is fixed on the high-speed rail tensioner At the corresponding position, pull up the other end that is not adhered to the steel plate, and clamp the sample into the chuck through the connector or directly, and the angle between the pulled-up sample part and the steel plate is 90° in space . The chuck pulls the sample at a speed of 5mm/min to separate the insulating layer/first active material layer from the current collector, and the average tensile force in the final measured plateau area is recorded as the distance between the insulating layer/first active material layer and the current collector. adhesion. As shown in FIG. 4, it is required that the ratio of the standard deviation to the average value of the adhesive force data in the above-mentioned plateau area does not exceed 10%.

Insulation Coverage Test:

1) Cut the pole piece coated with the insulating coating to obtain the pole piece sample coated with the insulating coating, and mark the area on the side coated with the insulating coating as S1;

2) Use a CCD microscope with a resolution of 0.02 μm to count 1) the collector area (ie, the leakage area) that is not covered by the insulating material on the side of the middle pole piece sample coated with the insulating layer, which is denoted 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:

The Dv99 of the inorganic particles was tested using a laser particle sizer.

Dv99 refers to the particle size of the inorganic particles in the volume-based particle size distribution from the small particle size side to 99% of the cumulative volume, that is, the volume of the inorganic particles smaller than this particle size accounts for 99% of the total volume of the inorganic particles.

Insulation thickness test:

1) Under the environment of (25±3)℃, remove the pole piece coated with insulating coating from the finished cell. Wipe off the residual electrolyte on the surface of the pole piece with dust-free paper;

2) The pole piece coated with the insulating layer is cut under the plasma to obtain its cross section;

3) Observe the cross section of the pole piece obtained in 2) under SEM, and test the thickness of the single-sided insulating coating. The adjacent test points are separated by 2mm to 3mm, and at least 15 different points are tested, and the average of all test points is recorded as insulation. the thickness of the coating.

Thickness test of the first active material layer and the second active material layer:

1) Remove the positive pole piece coated with the first active material layer and the second active material layer from the finished lithium-ion battery;

2) using plasma cutting technology, cutting the positive electrode pole piece obtained in 1) along the positive electrode thickness direction to obtain the cross section of the first active material layer and the second active material layer;

3) Under SEM (electron microscope), observe the cross-sections of the first active material layer and the second active material layer obtained in 2) (the length of the observed cross-section should be no less than 2cm), and test the first active material layer under SEM. The single-sided thickness of the first active material layer and the second active material layer, the adjacent test points are separated by 2mm to 3mm, at least 15 different points are tested, and the average thickness of all test positions of each layer is recorded as the thickness value of the corresponding layer.

Positive full charge internal resistance test:

1) Charge with a constant current of 0.05C to a voltage of 4.45V (that is, full charge voltage), and then charge with a constant voltage of 4.45V to a current of 0.025C (cut-off current), so that the lithium-ion battery is fully charged;

2) disassemble the lithium-ion battery to obtain a positive electrode;

3) After soaking the positive electrode obtained in 2) in DMC (dimethyl carbonate) at 25° C. for 1 h, dry it in a fume hood;

4) Use the BER1200 type diaphragm resistance tester to test the resistance of the positive pole piece obtained in 3), the adjacent test points are separated by 2mm to 3mm, and at least 15 different points are tested. Note that the average resistance of all test points is the diaphragm of the positive pole piece resistance. The parameters are: the area of the indenter is 153.94mm ² , the pressure is 3.5t, and the holding time is 50s.

90° vertical side nail penetration test pass rate test:

Charge the lithium-ion battery to be tested with a constant current of 0.05C to a voltage of 4.45V (that is, full charge voltage), and then charge it with a constant voltage of 4.45V to a current of 0.025C (cut-off current), so that the lithium-ion battery is fully charged. Charge state, record the appearance of the lithium-ion battery before the test. The battery is subjected to a piercing test in an environment of 25±3℃. The diameter of the steel nail is 4mm, the piercing speed is 30mm/s, and the piercing position is located on the side of the lithium-ion battery. The test is carried out for 3.5min or the surface temperature of the electrode assembly drops to 50℃. Stop the test , Take 10 lithium-ion batteries as a group, observe the state of the lithium-ion battery during the test, take the lithium-ion battery not burning and not exploding as the judgment standard, 20 times the nail penetration test is passed more than 15 times and it is judged as passing the nail penetration test.

Example 1

Distilled water was added to the reaction kettle and stirring was started. After nitrogen was introduced to remove oxygen for 2 hours, sodium acrylate monomer was added to the reaction kettle, heated to 65°C under an inert atmosphere and kept at a constant temperature, and then 20% ammonium persulfate solution was added as a trigger. The reagent started to react, and after 22 hours of reaction, the precipitate was taken out, and lye was added to neutralize the pH to 6.5. Among them, the mass ratio between distilled water, monomer and initiator is 89.5:10:0.5. After the reaction, the reaction product is filtered, washed, dried, pulverized, sieved and the like to obtain the first binder.

Distilled water was added to the reaction kettle and stirring was started. After nitrogen was introduced to remove oxygen for 2 hours, methyl acrylate monomer was added to the reaction kettle, heated to 65°C under an inert atmosphere and kept at a constant temperature, and then 20% ammonium persulfate solution was added as a The initiator started to react, and after 22 hours of reaction, the precipitate was taken out, and lye was added to neutralize the pH to 6.5. Among them, the mass ratio between distilled water, monomer and initiator is 89.5:10:0.5. After the reaction, the reaction product is filtered, washed, dried, pulverized, sieved and the like to obtain the second binder.

Disperse the second binder, the inorganic particle boehmite and the leveling agent polyethoxypropoxypropene in deionized water, stir evenly until the viscosity of the slurry is stable, and obtain an insulating layer slurry with a solid content of 30%, The mass ratio between the second binder, the inorganic particles and the leveling agent is 15:84.9:0.1. The weight-average molecular weight of the leveling agent was 20,000, and the weight-average molecular weight of the second binder was 500,000.

Mix the first active material lithium iron phosphate, the first binder, nanoparticle conductive carbon, carbon nanotubes and leveling agent polyethoxypropoxypropene in a mass ratio of 95.6:3:0.7:0.5:0.2, Then, N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75%, and the mixture was stirred uniformly. The slurry is uniformly coated on the current collector aluminum foil with a thickness of 10 μm, and dried at 90° C. to obtain a first active material layer with a thickness of 5 μm; wherein, the weight-average molecular weight of the first binder is 500,000, and the leveling agent The weight average molecular weight of 20000, the Dv99 of the first active substance is 4μm;

Mix the second active material lithium cobaltate (LCO), polyvinylidene fluoride (PVDF), conductive carbon black, and carbon nanotubes in a mass ratio of 97.7:1.3:0.5:0.5, and then add N-methylpyrrolidone (NMP) As a solvent, it was prepared into a slurry with a solid content of 75%, and stirred uniformly. uniformly coating the slurry on the first active material layer, and drying at 90° C. to obtain a second active material layer with a thickness of 85 μm;

The prepared insulating layer slurry was coated on the area of the aluminum foil surface where the first active material layer and the second active material layer were not coated, that is, the uncoated area, to obtain an insulating layer with a thickness of 6 μm, and the coverage of the insulating layer was is 95%.

The above steps are then repeated on the other surface of the positive electrode to obtain a positive electrode coated on both sides with the first active material layer, the second active material layer and the insulating layer. Cut the positive electrode into a size of 74mm×867mm and weld the tabs for later use.

The active material graphite, styrene-butadiene polymer and sodium carboxymethyl cellulose are mixed according to the weight ratio of 97.5:1.3:1.2, and deionized water is added as a solvent to prepare a slurry with a solid content of 70%, and Stir well. The slurry was uniformly coated on the current collector copper foil, dried at 110°C, and cold pressed to obtain a negative electrode with an active material layer coated on one side with an active material layer thickness of 150 μm.

After the above steps are completed, the same method is used to complete these steps on the back side of the negative electrode, that is, a negative electrode with double-sided coating is obtained. After the coating was completed, the negative electrode was cut into sheets with a size of 76 mm×851 mm and the tabs were welded for use.

In a dry argon atmosphere, the organic solvents ethylene carbonate, methyl ethyl carbonate and diethyl carbonate were mixed in a mass ratio of EC:EMC:DEC=30:50:20 to obtain an organic solution, and then lithium salt was added to the organic solvent Lithium hexafluorophosphate was dissolved and mixed uniformly to obtain an electrolyte solution with a lithium salt concentration of 1.15 mol/L.

Alumina and polyvinylidene fluoride were mixed in a mass ratio of 90:10 and dissolved in deionized water to form a ceramic slurry with a solids content of 50%. Then, the ceramic slurry was uniformly coated on one side of the porous substrate (polyethylene, thickness 7 μm, average pore size 0.073 μm, porosity 26%) by gravure coating, and dried to obtain a ceramic coating The bilayer structure with the porous substrate, the thickness of the ceramic coating is 50 μm.

Polyvinylidene fluoride (PVDF) and polyacrylate were mixed in a mass ratio of 96:4 and dissolved in deionized water to form a polymer slurry with a solids content of 50%. Then, the polymer slurry is uniformly coated on both surfaces of the above-mentioned double-layer structure of the ceramic coating layer and the porous substrate by the gravure coating method, and is subjected to drying treatment to obtain a separator, wherein the single layer formed by the polymer slurry is The coating thickness is 2 μm.

The positive electrode, the separator and the negative electrode prepared above are stacked in sequence, so that the separator is placed between the positive and negative electrodes to play a role of isolation, and the electrode assembly is obtained by winding. The electrode assembly is put into an aluminum-plastic film packaging bag, and the moisture is removed at 80 ° C, the prepared electrolyte is injected, and the lithium ion battery is obtained through vacuum packaging, standing, forming, and shaping.

Example 2

The rest is the same as Example 1, except that in <Preparation of First Binder>, the sodium acrylate monomer is replaced with acrylamide monomer.

Example 3

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced with the monomer acrylamide:sodium acrylate in a mass ratio of 40:60.

Example 4

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced with the monomer acrylonitrile:acrylamide in a mass ratio of 40:60.

Example 5

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced with the monomer acrylonitrile:sodium acrylate in a mass ratio of 40:60.

Example 6

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced with the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 30:60:10.

Example 7

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced by the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 30:10:60.

Example 8

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced with the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 40:50:10.

Example 9

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced with the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 40:10:50.

Example 10

The same as in Example 1, except that in <Preparation of First Binder>, the sodium acrylate monomer was replaced by the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 45:45:10.

Example 11

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced by the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 45:10:45.

Example 12

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced by the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 50:40:10.

Example 13

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced by the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 50:10:40.

Example 14

The same as in Example 1, except that in <Preparation of the first binder>, sodium acrylate was replaced by the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 55:35:10.

Example 15

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced with the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 55:10:35.

Example 16

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced with the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 60:30:10.

Example 17

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced by the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 60:10:30.

Example 18

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced with the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 70:20:10.

Example 19

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced with the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 70:10:20.

Example 20

The same as in Example 1, except that in <Preparation of the First Binder>, the sodium acrylate monomer was replaced by the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 10:70:20.

Example 21

The same as in Example 1, except that in <Preparation of the first binder>, the sodium acrylate monomer was replaced with the monomer acrylonitrile:sodium acrylate:acrylamide in a mass ratio of 10:20:70.

Example 22

Except that the content of the first binder in <Preparation of Positive Electrode> was 1 wt %, the rest was the same as that of Example 10.

Example 23

Except that the content of the first binder in <Preparation of Positive Electrode> was 2 wt %, the rest was the same as that of Example 10.

Example 24

Except that the content of the first binder in <Preparation of Positive Electrode> was 4 wt %, the rest was the same as that of Example 10.

Example 25

Except that the content of the first binder in <Preparation of Positive Electrode> was 5 wt %, the rest was the same as that of Example 10.

Example 26

Except that the content of the first binder in <Preparation of Positive Electrode> was 8 wt %, the rest was the same as that of Example 10.

Example 27

Except that the content of the first binder in <Preparation of Positive Electrode> was 10 wt %, the rest was the same as that of Example 10.

Example 28

Except that the content of the first binder in <Preparation of Positive Electrode> was 12 wt %, the rest was the same as that of Example 10.

Example 29

Except that the content of the first binder in <Preparation of Positive Electrode> was 15 wt %, the rest was the same as that of Example 10.

Example 30

Except that the content of the first binder in <Preparation of Positive Electrode> was 18 wt %, the rest was the same as that of Example 10.

Example 31

Except that the content of the first binder in <Preparation of Positive Electrode> was 20 wt %, the rest was the same as that of Example 10.

Example 32

The procedure was the same as that of Example 10, except that in <Preparation of Positive Electrode>, lithium iron phosphate was replaced with lithium iron manganese phosphate.

Example 33

The procedure was the same as that of Example 10, except that in <Preparation of Positive Electrode>, lithium iron phosphate was replaced with lithium manganate.

Example 34

Except in <Preparation of Positive Electrode>, 0.7 wt % of nanoparticle conductive carbon and 0.5 wt % of carbon nanotubes were replaced by 1.2 wt % of carbon nanotubes, the Dv99 of the first positive electrode active material was 0.01 μm, the first positive electrode active material The thickness of the layer was the same as that of Example 32 except that the thickness of the layer was 0.04 μm.

Example 35

In <Preparation of Positive Electrode>, the procedure was the same as Example 34, except that the 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

In <Preparation of Positive Electrode>, the procedure was the same as Example 34, except that the 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

In <Preparation of Positive Electrode>, the procedure was the same as Example 34, except that the 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

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, and the rest was the same as that of Example 34.

Example 39

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 96 wt %, the content of nanoparticle conductive carbon is 0.3 wt %, the Dv99 of the first positive electrode active material is 0.5 μm, and the thickness of the first positive electrode active material layer is 2 μm. , and the rest are the same as in Example 32.

Example 40

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, and the rest was the same as that of Example 39.

Example 41

The procedure was the same as that of Example 32, except that in <Preparation of Positive Electrode>, the Dv99 of the first positive electrode active material was 3 μm.

Example 42

In <Preparation of Positive Electrode>, the procedure was the same as Example 32 except that the 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

In <Preparation of Positive Electrode>, the procedure was the same as that of Example 32, except that the 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

In <Preparation of Positive Electrode>, the procedure was the same as that of Example 32, except that the 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

In <Preparation of Positive Electrode>, the procedure was the same as that of Example 32, except that the 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

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, the rest was the same as that of Example 32.

Example 47

In <Preparation of Positive Electrode>, the procedure was the same as that of Example 32, except that the 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

In <Preparation of Positive Electrode>, the procedure was the same as Example 32, except that the 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

In <Preparation of Positive Electrode>, the procedure was the same as Example 32 except that the 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

In <Preparation of Positive Electrode>, the procedure was the same as that of Example 32, except that the 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

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 96.7 wt %, 0.7 wt % of nanoparticle conductive carbon and 0.5 wt % of carbon nanotubes are replaced by 0.1 wt % of meshed graphite fibers, the rest are the same as the implementation Example 32 is the same.

Example 52

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 96.3 wt %, and the content of nanoparticle conductive carbon is 0 wt %, the rest is the same as that of Example 32.

Example 53

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 96.2 wt %, and the content of nanoparticle conductive carbon is 0.1 wt %, the rest is the same as that of Example 32.

Example 54

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 96 wt %, and the content of nanoparticle conductive carbon is 0.3 wt %, the rest is the same as that of Example 32.

Example 55

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 95.4 wt %, and the content of nanoparticle conductive carbon is 0.9 wt %, the rest is the same as that of Example 32.

Example 56

The same as in Example 32, except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 95.2 wt %, and the content of nanoparticle conductive carbon is 1.1 wt %.

Example 57

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 95 wt %, and the content of nanoparticle conductive carbon is 1.3 wt %, the rest is the same as that of Example 32.

Example 58

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 94.8 wt %, and the content of nanoparticle conductive carbon is 1.5 wt %, the rest is the same as that of Example 32.

Example 59

The same as in Example 32 except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 96 wt %, the content of nanoparticle conductive carbon is 0.5 wt %, and the content of carbon nanotubes is 0.3 wt %.

Example 60

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 95.8 wt %, and the content of nanoparticle conductive carbon is 0.5 wt %, the rest is the same as that of Example 32.

Example 61

The same as in Example 32, except that in <Preparation of Positive Electrode>, the nanoparticle conductive carbon content was 0.5 wt% and the carbon nanotube content was 0.7 wt%.

Example 62

The same as in Example 32 except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 95.4 wt %, the content of nanoparticle conductive carbon is 0.5 wt %, and the content of carbon nanotubes is 0.9 wt %.

Example 63

The same as Example 32, except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 95.2 wt %, the content of nanoparticle conductive carbon is 0.5 wt %, and the content of carbon nanotubes is 1.1 wt %.

Example 64

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 95.3wt%, 0.7wt% of nanoparticle conductive carbon and 0.5wt% of carbon nanotubes are replaced by 1.5wt% of nanoparticle conductive carbon, the rest is the same as the implementation Example 32 is the same.

Example 65

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 94.8 wt %, and the content of nanoparticle conductive carbon is 2.0 wt %, the rest is the same as that of Example 64.

Example 66

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 86.8 wt %, the content of nanoparticle conductive carbon is 5.0 wt %, and the content of first binder is 8 wt %, the rest is the same as that of Example 64.

Example 67

The same as in Example 64, except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 79.8 wt %, the content of nanoparticle conductive carbon is 10.0 wt %, and the content of the first binder is 10 wt %.

Example 68

The same as in Example 64, except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 71.8 wt %, the content of nanoparticle conductive carbon is 15.0 wt %, and the content of the first binder is 13 wt %.

Example 69

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 59.8 wt %, the content of nanoparticle conductive carbon is 15 wt %, the content of carbon nanotubes is 5 wt %, and the content of the first binder is 20 wt %. Example 32 is the same.

Example 70

The procedure was the same as in Example 32, except that in <Preparation of Positive Electrode>, polyethoxypropoxypropene was replaced with sodium polycarboxylate.

Example 71

The same procedure as in Example 32 was performed except that polyethoxypropoxypropene was replaced with polysiloxane in <Preparation of Positive Electrode>.

Example 72

The procedure was the same as in Example 32, except that in <Preparation of Positive Electrode>, polyethoxypropoxypropene was replaced with polymethyl acrylate.

Example 73

The procedure was the same as that of Example 32, except that in <Preparation of Positive Electrode>, polyethoxypropoxypropene was replaced with polypropylene alcohol.

Example 74

The procedure was the same as that of Example 32, except that in <Preparation of Positive Electrode>, polyethoxypropoxypropene was replaced with polyethylene glycol.

Example 75

The same as in Example 32, except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate was 95.79 wt % and the content of polyethoxypropoxy propene was 0.01 wt %.

Example 76

The same as in Example 32, except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate was 95.75 wt % and the content of polyethoxypropoxy propene was 0.05 wt %.

Example 77

The same as in Example 32, except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate was 95.7 wt% and the content of polyethoxypropoxypropene was 0.1 wt%.

Example 78

The same as in Example 32, except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate was 95.5 wt % and the content of polyethoxypropoxy propene was 0.3 wt %.

Example 79

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 95.3 wt %, and the content of polyethoxypropoxy propene is 0.5 wt %, the rest is the same as that of Example 32.

Example 80

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 95 wt %, and the content of polyethoxypropoxy propene is 0.8 wt %, the rest is the same as that of Example 32.

Example 81

The same as in Example 70, except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate was 94.8 wt % and the content of sodium polycarboxylate was 1 wt %.

Example 82

The same as Example 70, except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 92.7 wt %, the content of carbon nanotubes is 0.6 wt %, and the content of sodium polycarboxylate is 3 wt %.

Example 83

The same as Example 70 except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 90.6 wt %, the content of carbon nanotubes is 0.7 wt %, and the content of sodium polycarboxylate is 5 wt %.

Example 84

The same as in Example 73, except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate was 87.5 wt %, the content of carbon nanotubes was 0.8 wt %, and the content of polyacryl alcohol was 8 wt %.

Example 85

Example 73 was the same as in Example 73, except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate was 85.4 wt%, the content of carbon nanotubes was 0.9 wt%, and the content of polyacryl alcohol was 10 wt%.

Example 86

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate is 98.89 wt %, and the content of polyethoxypropoxy propene is 1 wt %, the rest is the same as that of Example 51.

Example 87

Except that in <Preparation of Positive Electrode>, the content of lithium iron manganese phosphate was 50 wt % and the content of polyethoxypropoxy propene was 20 wt %, the rest was the same as that of Example 69.

Example 88

The same as in Example 78, except that in <Preparation of Insulation Layer Paste>, the inorganic particle content was 84.99 wt % and the leveling agent content was 0.2 wt %.

Example 89

Except that in <Preparation of Second Binder>, the second binder is selected from acrylonitrile multipolymer, the rest is the same as that of Example 88.

Example 90

Except that in <Preparation of Second Binder>, sodium carboxymethyl cellulose was selected as the second binder, the rest was the same as that of Example 88.

Example 91

Except that in <Preparation of Second Binder>, the second binder was selected from sodium polyacrylate, the rest was the same as that of Example 88.

Example 92

Except that in <Preparation of Second Binder>, polyacrylamide was selected as the second binder, the rest was the same as that of Example 88.

Example 93

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer with a mass ratio of 40:60 acrylamide:sodium acrylate, in <Preparation of positive electrode>: the coverage of the insulating layer was 96 Except for %, the rest is the same as in Example 88.

Example 94

Except in <Preparation of Second Binder>: the methyl acrylate monomer is replaced with a monomer acrylonitrile:acrylamide in a mass ratio of 40:60, in <Preparation of Positive Electrode>: the coverage of the insulating layer is 97 Except for %, the rest is the same as in Example 88.

Example 95

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer with a mass ratio of 40:60 acrylonitrile:sodium acrylate, in <Preparation of positive electrode>: the coverage of the insulating layer was 97 Except for %, the rest is the same as in Example 88.

Example 96

Except in <Preparation of the Second Binder>: the methyl acrylate monomer was replaced with a monomer with a mass ratio of 27:60:10:3 Acrylonitrile: Sodium Acrylate: Acrylamide: Acrylate, in <Preparation of Positive Electrode >Medium: Except that the coverage of the insulating layer was 97%, the rest was the same as that of Example 88.

Example 97

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer in a mass ratio of 30:60:10 acrylonitrile:sodium acrylate:acrylamide, in <Preparation of positive electrode>: insulating layer The coverage was the same as in Example 88 except that the coverage was 99%.

Example 98

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer in a mass ratio of 30:10:60 acrylonitrile:sodium acrylate:acrylamide, in <Preparation of positive electrode>: insulating layer The coverage was the same as in Example 88 except that the coverage was 99%.

Example 99

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer in a mass ratio of 40:50:10 acrylonitrile:sodium acrylate:acrylamide, in <Preparation of positive electrode>: insulating layer The coverage was the same as in Example 88 except that the coverage was 99%.

Example 100

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer in a mass ratio of 40:10:50 acrylonitrile:sodium acrylate:acrylamide, in <Preparation of positive electrode>: insulating layer The coverage was the same as in Example 88 except that the coverage was 99%.

Example 101

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer in a mass ratio of 45:45:10 acrylonitrile:sodium acrylate:acrylamide, in <Preparation of positive electrode>: insulating layer The coverage was the same as in Example 88 except that the coverage was 99%.

Example 102

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer in a mass ratio of 45:10:45 acrylonitrile:sodium acrylate:acrylamide, in <Preparation of positive electrode>: insulating layer The coverage was the same as in Example 88 except that the coverage was 99%.

Example 103

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer in a mass ratio of 50:40:10 acrylonitrile:sodium acrylate:acrylamide, in <Preparation of positive electrode>: insulating layer The coverage was the same as in Example 88 except that the coverage was 99%.

Example 104

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer in a mass ratio of 50:10:40 acrylonitrile:sodium acrylate:acrylamide, in <Preparation of positive electrode>: insulating layer The coverage was the same as in Example 88 except that the coverage was 99%.

Example 105

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer in a mass ratio of 55:35:10 acrylonitrile:sodium acrylate:acrylamide, in <Preparation of positive electrode>: insulating layer The coverage was the same as in Example 88 except that the coverage was 99%.

Example 106

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer in a mass ratio of 55:10:35 acrylonitrile:sodium acrylate:acrylamide, in <Preparation of positive electrode>: insulating layer The coverage was the same as in Example 88 except that the coverage was 99%.

Example 107

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer in a mass ratio of 60:30:10 acrylonitrile:sodium acrylate:acrylamide, in <Preparation of positive electrode>: insulating layer The coverage was the same as in Example 88 except that the coverage was 99%.

Example 108

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer in a mass ratio of 60:10:30 acrylonitrile:sodium acrylate:acrylamide, in <Preparation of positive electrode>: insulating layer The coverage was the same as in Example 88 except that the coverage was 99%.

Example 109

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer in a mass ratio of 70:20:10 acrylonitrile:sodium acrylate:acrylamide, in <Preparation of positive electrode>: insulating layer The coverage was the same as in Example 88 except that the coverage was 99%.

Example 110

Except in <Preparation of Second Binder>: the methyl acrylate monomer was replaced with a monomer in a mass ratio of 70:10:20 acrylonitrile:sodium acrylate:acrylamide, in <Preparation of positive electrode>: insulating layer The coverage was the same as in Example 88 except that the coverage was 99%.

Example 111

The same as Example 101 except that in <Preparation of Insulating Layer Paste>, the content of the second binder was 50 wt %, the content of inorganic particles was 49.8 wt %, and the coverage of the insulating layer was 95 %.

Example 112

The same as Example 101 except that in <Preparation of Insulating Layer Paste>, the content of the second binder was 40 wt %, the content of inorganic particles was 59.8 wt %, and the coverage of the insulating layer was 95 %.

Example 113

The same as Example 101 except that in <Preparation of Insulating Layer Paste>, the content of the second binder was 30 wt %, the content of inorganic particles was 69.8 wt %, and the coverage of the insulating layer was 95 %.

Example 114

The same as Example 101 except that in <Preparation of Insulating Layer Paste>, the content of the second binder was 25 wt %, the content of inorganic particles was 74.8 wt %, and the coverage of the insulating layer was 97 %.

Example 115

The same as Example 101 except that in <Preparation of Insulating Layer Paste>, the content of the second binder was 20 wt %, the content of inorganic particles was 79.8 wt %, and the coverage of the insulating layer was 99 %.

Example 116

The same as Example 101 except that in <Preparation of Insulating Layer Paste>, the content of the second binder was 10 wt %, the content of inorganic particles was 89.8 wt %, and the coverage of the insulating layer was 99 %.

Example 117

The same as Example 101 except that in <Preparation of Insulating Layer Paste>, the content of the second binder was 5 wt %, the content of inorganic particles was 94.8 wt %, and the coverage of the insulating layer was 96 %.

Example 118

Except that in <Preparation of Insulating Layer Paste>, the content of the second binder is 2 wt %, the content of inorganic particles is 97.99 wt %, the content of leveling agent is 0.01 wt %, and the coverage of the insulating layer is 95 %, the rest Same as Example 101.

Example 119

Except that in <Preparation of Insulating Layer Paste>, the content of the second binder is 5 wt %, the content of inorganic particles is 94.9 wt %, the content of leveling agent is 0.1 wt %, and the coverage of the insulating layer is 92 %, the rest Same as Example 101.

Example 120

Except that in <Preparation of Insulating Layer Paste>, the content of the second binder is 25 wt %, the content of inorganic particles is 72 wt %, the content of leveling agent is 3 wt %, and the coverage of the insulating layer is 94 %. Example 101 is the same.

Example 121

Except that in <Preparation of Insulating Layer Paste>, the content of the second binder is 45 wt %, the content of inorganic particles is 50 wt %, the content of leveling agent is 5 wt %, and the coverage of the insulating layer is 93 %. Example 101 is the same.

Example 122

The same as in Example 111, except that in <Preparation of Insulating Layer Paste>, the inorganic particle content was 40 wt %, the leveling agent content was 10 wt %, and the coverage of the insulating layer was 90 %.

Example 123

The procedure was the same as that of Example 101, except that in <Preparation of Insulation Layer Slurry>, boehmite was replaced with diaspore.

Example 124

The procedure was the same as that of Example 101, except that in <Preparation of Insulation Layer Slurry>, the boehmite was replaced with alumina.

Example 125

The procedure was the same as that of Example 101, except that in <Preparation of Insulation Layer Slurry>, the boehmite was replaced with barium sulfate.

Example 126

The procedure was the same as that of Example 101, except that calcium sulfate was used instead of boehmite in <Preparation of Insulation Layer Slurry>.

Example 127

The procedure was the same as that of Example 101, except that in <Preparation of Insulation Layer Slurry>, the boehmite was replaced with calcium silicate.

Comparative Example 1

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 the first binder was 5 wt %, the rest was the same as Example 1 .

Comparative Example 2

The procedure was the same as that of Example 1, except that the lithium iron phosphate in <Preparation of Positive Electrode> was replaced with lithium cobalt oxide.

Comparative Example 3

Except that in <Preparation of Positive Electrode>, the content of lithium iron phosphate is 71.8wt%, 0.7wt% of nanoparticle conductive carbon and 0.5wt% of carbon nanotubes are replaced by 25wt% of nanoparticle conductive carbon, the rest is the same as Example 1.

Comparative Example 4

Except not containing an insulating layer, the rest is the same as that of Example 78.

Comparative Example 5

Except in <Preparation of Second Adhesive>: the second adhesive is polyvinylidene fluoride, and in <Preparation of Insulating Layer Slurry>: the coverage of the insulating layer is 90%, the rest are the same as those in Example 124 same.

The preparation parameters and test results of each embodiment and comparative example are shown in Tables 1-3 below.

Table 1 Preparation parameters and test results of Examples 1-31 and Comparative Example 1

Table 2 Preparation parameters and test results of Examples 32-87 and Comparative Examples 2-3

Table 3 Preparation parameters and test results of Examples 88-127 and Comparative Examples 4-5

Note: "\" in Table 1-3 means no preparation parameters or test results.

It can be seen from Examples 1-31 and Comparative Example 1 that the first active material layer contains the first binder of the present application and the lithium ion battery with the binder content within the scope of the present application, the first active material layer The bonding force between the current collector and the current collector is significantly improved, especially in Example 27 and Example 28, the bonding force between the first active material layer and the current collector reaches more than 310N/m, and the positive electrode is fully charged in the lithium ion battery. The resistance after charging is improved, and the pass rate of the nail penetration test is significantly improved, which can effectively improve the safety of lithium-ion batteries.

It can be seen from Examples 32-87 and Comparative Examples 2-3 that by controlling the composition and Dv99 of the first active material, the composition and content of the conductive agent, and the composition and content of the leveling agent, the positive electrode provided by the present application is fully charged in the lithium ion battery. The resistance after charging is improved, and the pass rate of the piercing test of the lithium-ion battery is significantly improved, which can effectively improve the safety of the lithium-ion battery.

It can be seen from Examples 88-127 and Comparative Examples 4-5 that the lithium ion battery with the insulating layer of the present application, by controlling the composition and content of the second binder, the composition and content of inorganic particles, and the composition and content of the leveling agent, The adhesion between the insulating layer and the current collector is significantly improved, especially in Examples 101-106, the adhesion between the insulating layer and the current collector is over 350N/m, and the pass rate of the lithium-ion battery piercing test It has been significantly improved, which can effectively improve the safety of lithium-ion batteries.

The above are only preferred embodiments of the present application, and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection of the present application. within the range.

Claims

An electrochemical device, comprising a positive electrode, the positive electrode comprising:

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 disposed on at least one surface of the current collector, and the first active material layer is disposed between the current collector and the second active material layer;

Wherein, the first binder includes a copolymer formed by the polymerization of acrylate, acrylamide and acrylonitrile.
The electrochemical device according to claim 1, wherein the resistance of the positive electrode after the electrochemical device is fully charged is 10Ω or more.
The electrochemical device according to claim 1, wherein, based on the total mass of the copolymer, the mass percentage content of the acrylonitrile is 1% to 70%, and the mass percentage content of the acrylate is 1% to 70%, the mass percentage content of the acrylamide is 1% to 70%.
The electrochemical device according to claim 1, wherein the first active material layer further comprises a leveling agent, the leveling agent comprising an olefin-based derivative polymer, a carboxylate-based polymer, a siloxane At least one of alkene-based polymer, alkenoate-based polymer, alcohol-based polymer or ether-based polymer.
The electrochemical device according to claim 4, wherein the content of the first active material in the first active material layer is 50 wt % to 98.89 wt %, and the content of the first binder is 1 wt % to 1 wt % 20wt%, the content of the conductive agent is 0.1wt% to 20wt%, and the content of the leveling agent is 0.01wt% to 10wt%.
The electrochemical device according to claim 1, wherein Dv99 of the first active material is 0.01 μm to 19.9 μm.
The electrochemical device according to claim 1, wherein the monolayer thickness of the first active material layer is 0.04 μm to 20 μm, and the monolayer thickness of the second active material layer is 20 μm to 200 μm.
The electrochemical device according to claim 1, wherein the adhesive force between the first active material layer and the current collector is 201 N/m or more.
The electrochemical device of claim 4, wherein the current collector includes a coating region provided with the first active material and the second active material, and wherein the first active material and the second active material are not provided an uncoated area of the active material; the uncoated area is at least partially provided with an insulating layer.
The electrochemical device according to claim 9, wherein the adhesive force between the insulating layer and the positive electrode current collector is 201 N/m or more.
The electrochemical device of claim 9, wherein the insulating layer has a coverage of 90% to 100%.
The electrochemical device of claim 9, wherein the insulating layer further comprises inorganic particles, a second binder, and the leveling agent;

The inorganic particles include at least one of boehmite, diaspore, alumina, barium sulfate, calcium sulfate or calcium silicate;

The second binder includes at least one of propylene derivative copolymers, polyacrylates, acrylonitrile multipolymers, carboxymethyl cellulose salts or nitrile rubber.
The electrochemical device according to claim 12, wherein the content of the inorganic particles in the insulating layer is 40 wt % to 97.99 wt %, the content of the binder is 2 wt % to 50 wt %, the leveling The content of the agent is 0.01 wt % to 10 wt %.
The electrochemical device of claim 9, wherein the insulating layer has a thickness of 0.02 μm to 10 μm.
The electrochemical device of claim 13, 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 30Ω to 100Ω;

(b) based on the total mass of the polymer or the copolymer, the mass percentage content of the acrylonitrile is 40% to 60%, and the mass percentage content of the acrylate is 10% to 50%, so The mass percentage content of the acrylamide is 10% to 50%;

(c) described leveling agent comprises at least one in sodium carboxylate polymer, oxygen-containing propylene polymer or polysiloxane;

(d) the inorganic particles include at least one of boehmite or alumina;

(e) the second binder includes at least one of propylene polymer or nitrile rubber;

(f) The content of the inorganic particles in the insulating layer is 72 wt % to 94.9 wt %, the content of the binder is 5 wt % to 25 wt %, and the content of the leveling agent is 0.1 wt % to 3 wt % .
The electrochemical device of claim 4, wherein the leveling agent comprises polyethoxypropoxypropene, polysiloxane, polymethyl acrylate, polyethylene glycol, sodium polycarboxylate, or poly At least one of allyl alcohol.
An electronic device comprising the electrochemical device of any one of claims 1 to 16.
A method of preparing the electrochemical device of any one of claims 1 to 16, comprising:

Mixing the first active material, the first binder, the conductive agent and the solvent to obtain the first active material layer slurry;

coating the first active material layer slurry on the current collector, and drying to obtain a first active material layer;

Mixing the second active material, the binder, the conductive agent and the solvent to obtain the 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;

The positive electrode, the separator and the negative electrode are stacked in sequence, and an electrode assembly is obtained by winding, and the electrode assembly is put into a packaging bag, and the electrochemical device is obtained after packaging.
A method of fabricating an electrochemical device as claimed in claim 18, further comprising: coating an insulating layer on the uncoated regions of the current collector.