WO2022141508A1 - 一种电化学装置和电子装置 - Google Patents

一种电化学装置和电子装置 Download PDF

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WO2022141508A1
WO2022141508A1 PCT/CN2020/142392 CN2020142392W WO2022141508A1 WO 2022141508 A1 WO2022141508 A1 WO 2022141508A1 CN 2020142392 W CN2020142392 W CN 2020142392W WO 2022141508 A1 WO2022141508 A1 WO 2022141508A1
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Prior art keywords
material layer
binder
electrochemical device
positive electrode
content
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PCT/CN2020/142392
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English (en)
French (fr)
Inventor
刘晓欠
刘胜奇
韩冬冬
王可飞
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东莞新能源科技有限公司
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Priority to PCT/CN2020/142392 priority Critical patent/WO2022141508A1/zh
Priority to CN202080016363.8A priority patent/CN113498558B/zh
Publication of WO2022141508A1 publication Critical patent/WO2022141508A1/zh

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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
    • 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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of electrochemistry, in particular to an electrochemical device and an electronic device.
  • 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 and service life of lithium-ion batteries.
  • Lithium-ion batteries usually include a positive electrode, a negative electrode, and a separator, and the separator is located between the positive electrode and the negative electrode.
  • the positive electrode contains an active material layer.
  • the selection and content of the binder often affect the feasibility of the positive electrode process and the performance (such as capacity, power, cycle, etc.) of the lithium ion battery.
  • the purpose of the present application is to provide an electrochemical device and an electronic device to improve the energy density of the electrochemical device.
  • 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.
  • a first aspect of the present application provides an electrochemical device including a positive electrode, the positive electrode includes a current collector, a first material layer and a second material layer, at least one surface of the current collector is provided with a second material layer, the first material layer is A material layer is disposed between the current collector and the second material layer, the second material layer contains a second active material, a second conductive agent and a second binder, and the specific surface area of the second active material is 0.05 m 2 /g to 20 m 2 /g; the first material layer comprises a first active material, a first conductive agent and a first binder, the first binder comprising at least one monomer in acrylate or acrylamide polymerized of polymers.
  • At least one surface of the current collector is provided with a first material layer and a second material layer, and the first material layer is provided between the current collector and the second material layer.
  • 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.
  • a first material layer and a second material layer are sequentially disposed on one surface of the current collector. In some embodiments of the present application, the first material layer and the second material layer are sequentially disposed on both surfaces of the current collector.
  • the specific surface area of the second active material is 0.05 m 2 /g to 20 m 2 /g.
  • the specific surface area of the second active material is too small, for example, less than 0.05m 2 /g, the second active material cannot be fully contacted with the electrolyte, and thus cannot provide more oxide active sites, which will affect the lithium ion Battery kinetics;
  • the specific surface area of the second active material is too large, for example, more than 20m 2 /g, the slurry is not easy to disperse uniformly, and it will cause too many active sites, increase side reactions, deteriorate the stability of the cell, and consume more
  • the proportion of the second binder is likely to reduce the adhesion between the second material layer and the first material layer, and increase the growth rate of internal resistance.
  • the first binder comprises a polymer obtained by polymerizing at least one monomer of acrylate or acrylamide.
  • the polymer is soaked in the electrolyte at 85°C for 24 hours or at 25°C for 7 days, and the swelling rate is less than 5%, which can make the first material layer and the current collector or the first material layer and the second material layer have good bonding force.
  • the use of the first adhesive in the first material layer improves the adhesion of the first material layer, increases the adhesion between the first material layer and the second material layer, and makes the second material layer in the The amount of the second binder is reduced.
  • controlling the specific surface area of the second active material within the scope of the present application also reduces the content of the second binder.
  • the decrease in the content of the second binder in the second material layer increases the relative content ratio of the second active material in the second active material layer, thereby effectively improving the energy density of the lithium ion battery.
  • the content A of the first binder in the first material layer is 1 wt % to 20 wt %.
  • the content of the first binder is too low, for example, less than 1 wt%, the film-forming property of the first positive active layer is poor, which is not conducive to the improvement of coverage;
  • the content of the first binder is too high, for example, higher than 20wt%, due to the high cohesive force of the first binder itself, the shrinkage of the first material layer increases during the drying process of film formation, while the current collector substrate (such as aluminum foil) basically does not shrink, and the shrinkage ratio of the two is The difference is large, causing the first material layer to peel off from the current collector substrate in a large area.
  • the polymer in the first binder further comprises acrylonitrile monomer.
  • the mass percentage content of acrylonitrile is 30% to 70%, and the sum of the mass percentage content of acrylate and acrylamide is 30% to 70%.
  • the mass percentage content of acrylonitrile is 40% to 60%, and the sum of the mass percentage content of acrylate and acrylamide is 40% to 60%.
  • the weight-average molecular weight of the first binder 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 first binder is 100,000 to 2,000,000.
  • the weight-average molecular weight of the first binder is too large, and the thickening effect of the first binder is enhanced, resulting in excessively high slurry viscosity and poor fluidity, which may easily lead to the leakage of the first positive electrode active layer slurry. coating; the weight average molecular weight of the first binder is too small, resulting in too low viscosity of the slurry, poor film-forming property of the slurry, and leakage of the insulating layer slurry.
  • the slurry of the first material layer can form a thin film with a uniform thickness on the surface of the current collector base material, thereby forming the first material layer, which can improve the relationship between the first material layer and the current collector. Adhesion between current collectors.
  • the second binder includes at least one of polyacrylic acid, polyvinylidene fluoride, polytetrafluoroethylene-hexafluoropropylene, sodium polyacrylate, nitrile rubber or polyacrylate .
  • the second binder includes at least one of polyacrylic acid, polyvinylidene fluoride or nitrile rubber.
  • the weight-average molecular weight of the second binder 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 second binder is 100,000 to 2,000,000.
  • the content B of the second binder in the second material layer is 0.5 wt % to 10 wt %.
  • the content of the second binder is too low, for example, less than 0.5wt%, the adhesion of the second material layer is too low, it is easy to release the film, and the performance of the cell is deteriorated.
  • the film formation of the second material layer is poor, which is not conducive to Improvement of coverage; when the content of the second binder is too high, for example, higher than 10wt%, because the shrinkage of the second material layer is different from that of the first material layer during the drying process of film formation, it is easy to cause the second material layer to shrink.
  • the material layer falls off from the first material layer in a large area, the content of the second active material is reduced, and the energy density of the cell is reduced.
  • the content of the second binder within the above content range, it is beneficial to improve the adhesion between the first material layer and the second material layer.
  • the adhesive force between the first material layer and the second material layer is more than 5 N/m, indicating that the first material layer and the second material layer have excellent adhesive properties.
  • the content B of the second binder in the second material layer is 0.5 wt % to 3.99 wt %; the content A of the first binder in the first material layer is the same as that of the second binder.
  • the increase of the content of the first binder in the first material layer can reduce the amount of the second binder in the second material layer, The relative content of the second active material in the second material layer is increased, thereby increasing the energy density of the lithium-ion battery.
  • the single-layer thickness of the first material layer is 0.01 ⁇ m to 20 ⁇ m.
  • the thickness of the first material layer is too low, for example, less than 0.01 ⁇ m, the first material layer is too thin, and the safety performance affected; when the thickness of the first material layer is too high, for example, higher than 20 ⁇ m, the relative content of the first active material in the positive electrode decreases, which affects the energy density of the lithium-ion battery.
  • the single-layer thickness of the second material layer is 20 ⁇ m to 300 ⁇ m.
  • the thickness of the second material layer is too low, for example, less than 20 ⁇ m, under the condition of a certain capacity, the lithium-ion battery will be affected. Energy density, and is not easy to process; when the thickness of the second material layer is too high, eg higher than 300 ⁇ m, the lithium-ion battery kinetics are deteriorated.
  • the resistance of the positive electrode after the electrochemical device is fully charged is 10 ⁇ or more, preferably 30 ⁇ to 100 ⁇ . 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.
  • the first conductive agent and the second conductive agent each independently comprise at least one of lamellar, mesh, wire, or zero-dimensional conductive agents.
  • the first conductive agent and the second conductive agent each independently comprise at least one of graphene, reticulated graphite fibers, carbon nanotubes, Ketjen black, graphite fibers or nanoparticle conductive carbon.
  • 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.
  • the initiator in the present application 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.
  • 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.
  • an alkaline solution is added to the reacted precipitate for neutralization to make the pH value 6.5 to 9.
  • the reaction product is filtered, washed, dried, pulverized, sieved and the like.
  • the preparation method of the second 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:
  • the reaction kettle containing the stirrer is evacuated, and nitrogen is evacuated to replace the oxygen. Then, deionized water, vinylidene fluoride, initiator, emulsifier and chain transfer agent are added to the reaction kettle, and the second binder is obtained after polymerization.
  • the initiator is not particularly limited, for example, it can be selected from dicumyl hydroperoxide; the emulsifier is not particularly limited, for example, it can be selected from perfluoroalkyl carboxylates; the chain transfer agent is not particularly limited, for example, it can be is selected from isopropanol. As long as the purpose of this application can be achieved.
  • 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 material layer includes a first active material
  • the second material layer includes a second active material.
  • the first active material and the second active material are not particularly limited, and active materials known in the art can be used, for example, the first active material and the second active material are not limited.
  • One active material may include at least one of lithium iron phosphate, lithium iron manganese phosphate or lithium manganate
  • the second active material may include lithium cobalt oxide, lithium nickel cobalt manganate (811, 622, 523, 111), nickel cobalt At least one of lithium aluminate, lithium iron phosphate, lithium iron manganese phosphate or lithium manganate.
  • the thickness of the current collector 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 ⁇ m to 12 ⁇ m.
  • the surface of the current collector is provided with a first material layer and a second material layer, and the first material layer and the second material layer usually do not completely coat the surface of the current collector.
  • Those skilled in the art can, according to actual needs, provide an insulating layer in the area where the first material layer and the second material layer are not provided on the surface of the current collector, which is not particularly limited in this application, as long as the purpose of the application can be achieved.
  • the negative electrode of the present application is not particularly limited as long as the purpose of the present application can be achieved.
  • negative electrodes typically contain current collectors and layers of materials.
  • the current collector is not particularly limited, and current collectors known in the art, such as copper foil, copper alloy foil, and composite current collectors, can be used.
  • the 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.
  • the thicknesses of the current collector and the material layer are not particularly limited as long as the purpose of the present application can be achieved.
  • the thickness of the current collector is 4 ⁇ m to 10 ⁇ m
  • the thickness of the material layer is 30 ⁇ m to 120 ⁇ m.
  • the negative electrode may further comprise a conductive layer located between the current collector and the material layer.
  • the composition of the conductive layer is not particularly limited, and may be a conductive layer commonly used in the art.
  • the conductive layer includes a conductive agent and a binder.
  • the conductive agent is not particularly limited as long as the purpose of the present application can be achieved.
  • 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.
  • 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.
  • SBR styrene-butadiene rubber
  • SBR styrene-butadiene rubber
  • 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.
  • the separator is not particularly limited as long as the purpose of the present application can be achieved.
  • PET polyethylene terephthalate
  • cellulose films such as polyethylene terephthalate (PET) films
  • PET polyamide Imine film
  • PA polyamide film
  • spandex or aramid film woven film
  • non-woven film non-woven film (non-woven fabric)
  • microporous film composite film, diaphragm paper, laminated film, spinning film, etc. at least one of them.
  • 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.
  • polypropylene porous membranes, polyethylene porous membranes, polypropylene non-woven fabrics, polyethylene non-woven fabrics, or polypropylene-polyethylene-polypropylene porous composite membranes may be used.
  • 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.
  • 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.
  • 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.
  • LiPF 6 may be chosen as the lithium salt because it gives high ionic conductivity and improves cycling 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.
  • 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.
  • FEC fluoroethylene carbonate
  • 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, trifluoromethyl
  • carboxylate compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone , caprolactone, valerolactone, mevalonolactone, caprolactone, and combinations thereof.
  • ether compounds examples include 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.
  • 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.
  • 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.
  • 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 present application provides an electrochemical device and an electronic device, which include a positive electrode, the positive electrode includes a current collector, a first material layer and a second material layer, at least one surface of the current collector is provided with a second material layer, the first material layer is A material layer is disposed between the current collector and the second material layer, the second material layer contains a second active material, a second conductive agent and a second binder, and the specific surface area of the second active material is 0.05 m 2 /g to 20 m 2 /g; the first material layer comprises a first active material, a first conductive agent and a first binder, the first binder comprising at least one monomer in acrylate or acrylamide polymerized of polymers.
  • the bonding force of the first material layer to the second material layer in the positive electrode is significantly increased, so that the content of the second binder in the second material layer of the positive electrode is reduced, and the proportion of the relative content of the second active material is increased.
  • the positive electrode is applied to an electrochemical device, which can effectively improve the energy density of the electrochemical device.
  • FIG. 1 is a schematic diagram of a positive electrode structure according to an embodiment of the application.
  • FIG. 2 is a schematic diagram of a positive electrode structure according to another embodiment of the application.
  • Figure 3 shows the relationship between the adhesion force and the stroke in the adhesion force test.
  • Reference numerals 10. Current collector, 21. First material layer, 22. Second material layer.
  • 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 diagram of a positive electrode structure according to an embodiment of the present application.
  • a first material layer 21 and a second material layer 22 are provided on the first surface and the second surface of the current collector 10 , wherein the first surface of the current collector 10 is provided with a first material layer 21 and a second material layer 22 .
  • the area of the area where the first material layer 21 and the second material layer 22 are provided is larger than the second surface of the current collector 10 , of course, the area of the area where the first material layer 21 and the second material layer 22 are provided on the first surface of the current collector 10 It can also be smaller than the second surface of the current collector 10 ; and the first material layers 21 are all disposed between the current collector 10 and the second material layer 22 .
  • FIG. 2 shows a schematic diagram of a positive electrode structure according to another embodiment of the present application, and only a first material layer 21 and a second material layer 22 are provided on the first surface of the current collector 10 .
  • the first material layer 21 and the second material layer 22 may also be provided on the second surface of the current collector 10 .
  • FIG. 3 shows the relationship between the adhesive force and the stroke of the present application in the adhesive force test.
  • the first binder weight average molecular weight test :
  • the weight average molecular weight of the first binder in the first material layer was tested using gel permeation chromatography (GPC).
  • GPC gel permeation chromatography
  • the weight-average molecular weight refers to a molecular weight that is statistically averaged by mass.
  • the specific surface area of the second active material was tested by nitrogen adsorption method.
  • the length and width values can be adjusted proportionally according to the actual situation.
  • a part of the sample is attached to the steel plate from one end of the sample through double-sided tape, and the adhesion length is not less than 40mm; The other end is adhered to the steel plate, and the sample is put into the chuck through the connector or directly clamped, wherein the part of the sample that is pulled up and the steel plate have an included angle of 90° in space.
  • the chuck pulls the sample at a speed of 5 mm/min to separate the first material layer from the second material layer, and the average tensile force in the final measured plateau area is recorded as the adhesive force between the first material layer and the second material layer. As shown in FIG. 3, it is required that the ratio of the standard deviation to the average value of the adhesion force data in the above-mentioned plateau area does not exceed 10%.
  • Thickness test of the first material layer and the second material layer :
  • the adjacent test points are separated by 2mm to 3mm, and at least 15 different points are tested, and the average resistance of all test points is recorded as the positive pole piece diaphragm. resistance.
  • the parameters are: the area of the indenter is 153.94mm 2 , the pressure is 3.5t, and the holding time is 50s.
  • Distilled water was added to the reaction kettle and stirring was started. After 2 hours of deoxygenation by introducing nitrogen into the reaction kettle, the following monomers acrylonitrile, sodium acrylate and acrylamide were added to the reaction kettle in a mass ratio of 40:45:15, and heated to 65°C under an inert atmosphere. And keep a constant temperature, then add 20% ammonium persulfate solution as an initiator to start the reaction, take out the precipitate after 22 hours of reaction, add alkaline solution 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.
  • the reaction kettle containing the stirrer was evacuated, and after nitrogen was used to replace the oxygen, deionized water, vinylidene fluoride, initiator dicumyl hydrogen peroxide, emulsifier perfluoroalkyl carboxylate, chain
  • the pressure of the transfer agent isopropyl alcohol to the reaction kettle is 3.5MPa, wherein the deionized water is 7 times the mass of the vinylidene fluoride monomer, the initiator accounts for 0.2% of the mass of the vinylidene fluoride monomer, and the emulsifier accounts for the mass of the vinylidene fluoride monomer. 0.5% of the chain transfer agent, and the chain transfer agent accounts for 5% of the mass of vinylidene fluoride monomer.
  • the temperature was raised to 60°C, the speed of the stirrer was 80r/min, and the polymerization reaction was started.
  • the vinylidene fluoride monomer was continuously added to maintain the pressure of the reactor at 3.5MPa, and the reaction was stopped until the solid content of the emulsion in the reactor reached 25%, and the unreacted monomer was recovered.
  • the polymer emulsion is released, and after centrifugation, washing and drying, polyvinylidene fluoride is obtained.
  • the first active material lithium iron phosphate, the first binder, the first conductive agent nanoparticle conductive carbon and carbon nanotubes are mixed in a mass ratio of 95.8:3.0:0.7:0.5, and then N-methylpyrrolidone (NMP) is added as Solvent, prepared into a slurry with a solid content of 35%, and stirred evenly.
  • NMP N-methylpyrrolidone
  • the slurry is uniformly coated on a current collector aluminum foil with a thickness of 10 ⁇ m, and dried at 90° C. to obtain a first material layer with a thickness of 5 ⁇ m; wherein, the weight-average molecular weight of the first binder is 500,000;
  • the above steps are repeated on the other surface of the positive electrode to obtain a positive electrode coated with the first material layer and the second positive electrode layer on both sides. 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%. Stir well.
  • the slurry was uniformly coated on the copper foil of the negative electrode current collector, dried at 110° C., and after cold pressing, a negative electrode with a single-sided coating material layer with a material layer thickness of 150 ⁇ m was obtained.
  • these steps are also completed on the back side of the negative electrode by the same method, that is, a negative electrode with double-sided coating is obtained.
  • the negative electrode is cut into sheets with a size of 76 mm ⁇ 851 mm and the tabs are welded for use.
  • 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 ⁇ m, average pore size 0.073 ⁇ m, 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 ⁇ m.
  • PVDF Polyvinylidene fluoride
  • polyacrylate was 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 ⁇ m.
  • 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 same as in Example 1, except that in ⁇ Preparation of Positive Electrode>, the specific surface area of the second active material was controlled to be 0.05 m 2 /g.
  • Example 2 The same as in Example 1, except that in ⁇ Preparation of Positive Electrode>, the specific surface area of the second active material was controlled to be 0.1 m 2 /g.
  • Example 2 The same as in Example 1, except that in ⁇ Preparation of Positive Electrode>, the specific surface area of the second active material was controlled to be 4.0 m 2 /g.
  • Example 2 The same as in Example 1, except that in ⁇ Preparation of Positive Electrode>, the specific surface area of the second active material was controlled to be 8.0 m 2 /g.
  • Example 2 The same as in Example 1, except that in ⁇ Preparation of Positive Electrode>, the specific surface area of the second active material was controlled to be 15 m 2 /g.
  • Example 2 The same as in Example 1, except that in ⁇ Preparation of Positive Electrode>, the specific surface area of the second active material was controlled to be 20 m 2 /g.
  • the binder is selected from sodium polyacrylate, the rest is the same as in Example 1.
  • the monomers were selected from acrylamide and sodium acrylate with a mass ratio of 40:60, the rest were the same as those in Example 1.
  • the monomers are selected from acrylonitrile and acrylamide with a mass ratio of 40:60, the rest are the same as those in Example 1.
  • the monomers were selected from acrylonitrile and sodium acrylate with a mass ratio of 40:60, the rest were the same as those in Example 1.
  • the monomers are selected from acrylonitrile, sodium acrylate and acrylamide with a mass ratio of 30:60:10, the rest are the same as in Example 1.
  • the monomers are selected from acrylonitrile, sodium acrylate and acrylamide with a mass ratio of 30:10:60, the rest are the same as those in Example 1.
  • the monomers were selected as acrylonitrile, sodium acrylate and acrylamide with a mass ratio of 50:40:10, the rest were the same as those in Example 1.
  • the monomers were selected from acrylonitrile, sodium acrylate and acrylamide with a mass ratio of 60:10:30, the rest were the same as in Example 1.
  • the monomers were selected from acrylonitrile, sodium acrylate and acrylamide with a mass ratio of 70:20:10, the rest were the same as those in Example 1.
  • Example 2 The same as in Example 1, except that in ⁇ Preparation of Positive Electrode>, the mass ratio of the first active material to the first binder was 88.8:10.0.
  • Example 2 The same as in Example 1, except that in ⁇ Preparation of Positive Electrode>, the mass ratio of the first active material to the first binder was 78.8:20.0.
  • the weight-average molecular weight of the first binder was 800,000, the rest was the same as that of Example 1.
  • the binder is selected from polyvinylidene fluoride, the rest is the same as that of Example 1.
  • the specific surface area of the second active material of the present application is within the range of the present application, and the adhesive force between the first material layer and the second material layer is lithium ion batteries.
  • the adhesive force between the first material layer and the second material layer reached more than 35N/m, which will reduce the content of the second adhesive in the second material layer, and the second material.
  • the increase in the relative content of the second active material in the layer is beneficial to the improvement of the energy density of the lithium-ion battery; and the pass rate of the nail penetration test is significantly improved, which can effectively improve the safety of the lithium-ion battery.
  • the first material layer contains the first binder of the present application, and the lithium ion battery with the content of the first binder within the scope of the present application, the first The adhesion between the material layer and the second material layer is significantly improved, especially in Examples 14-15 and 18-21, the adhesion between the first material layer and the second material layer reaches 30N/m
  • the above, up to 55N/m, will reduce the content of the second binder in the second material layer and increase the relative content of the second active material in the second material layer, which is beneficial to the improvement of the energy density of lithium-ion batteries ;
  • the pass rate of the nail penetration test is significantly improved, which can effectively improve the safety of lithium-ion batteries.
  • controlling the content of the second binder within the scope of the present application can effectively improve the adhesion between the first material layer and the second material layer, thereby improving the lithium ion battery energy density and safety.

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Abstract

本申请提供了一种电化学装置和电子装置，其包括正极，该正极包括集流体、第一材料层和第二材料层，该集流体的至少一个表面上设置有第二材料层，第一材料层设置在集流体和第二材料层之间，第二材料层包含第二活性材料、第二导电剂和第二粘结剂，第二活性材料的比表面积为0.05m 2/g至20m 2/g；第一材料层包含第一活性材料、第一导电剂和第一粘结剂，该第一粘结剂包含丙烯酸盐或丙烯酰胺中的至少一种单体聚合而成的聚合物。通过上述设计，使正极的第二材料层中第二粘结剂的含量减少、第二活性材料的相对含量占比增加，将该正极应用于电化学装置中，能够有效提升电化学装置的能量密度。

Description

一种电化学装置和电子装置 技术领域
本申请涉及电化学领域，具体涉及一种电化学装置和电子装置。
背景技术
锂离子电池具有储能密度大、开路电压高、自放电率低、循环寿命长、安全性能好等优点，广泛应用于电能储存、移动电子设备、电动汽车和航天航空设备等各个领域。随着移动电子设备和电动汽车进入高速发展阶段，市场对锂离子电池的能量密度、安全性和使用寿命等都提出了越来越高的要求。
锂离子电池通常包括正极、负极和隔离膜，隔离膜位于正极和负极之间。正极中包含活性材料层，现有的活性材料层中往往因为粘结剂种类的选择和含量的增加而影响正极工艺可行性及锂离子电池的性能(例如容量、功率、循环等)。
发明内容
本申请的目的在于提供一种电化学装置和电子装置，以提高电化学装置的能量密度。
需要说明的是，在以下内容中，以锂离子电池作为电化学装置的例子来解释本申请，但是本申请的电化学装置并不仅限于锂离子电池。
具体技术方案如下：
本申请的第一方面提供了一种电化学装置，包括正极，该正极包括集流体、第一材料层和第二材料层，该集流体的至少一个表面上设置有第二材料层，该第一材料层设置在集流体和第二材料层之间，该第二材料层包含第二活性材料、第二导电剂和第二粘结剂，第二活性材料的比表面积为0.05m 2/g至20m 2/g；该第一材料层包含第一活性材料、第一导电剂和第一粘结剂，该第一粘结剂包含丙烯酸盐或丙烯酰胺中的至少一种单体聚合而成的聚合物。
在本申请的一种实施方案中，上述集流体的至少一个表面上设置有第一材料层和第二材料层，该第一材料层设置在集流体和第二材料层之间。需要说明的是，这里的“表面”可以是集流体表面的全部区域，也可以是集流体表面的部分区域，本申请没有特别限制，只要能实现本申请目的即可。
在本申请的一些实施例中，集流体的一个表面上依次设置第一材料层和第二材料层。在本申请的一些实施例中，集流体的两个表面上均依次设置第一材料层和第二材料层。
在本申请中，第二活性材料的比表面积为0.05m 2/g至20m 2/g。不限于任何理论，第二活性材料的比表面积过小，例如小于0.05m 2/g，第二活性材料与电解液无法充分接触，从而无法提供更多的氧化物活性位点，将影响锂离子电池动力学；第二活性材料的比表面积过大，例如大于20m 2/g，浆料不易分散均匀，且会造成活性位点过多，副反应增多恶化电芯稳定性，且需要消耗更多比例的第二粘结剂，容易造成第二材料层与第一材料层之间的粘结力降低，内阻增长率升高。
在本申请中，第一粘结剂包含丙烯酸盐或丙烯酰胺中的至少一种单体聚合而成的聚合物。该聚合物在电解液中85℃下浸泡24h或25℃下浸泡7天，溶胀率小于5％，能够使第一材料层与集流体或第一材料层与第二材料层具有良好的粘结力。
本申请中“溶胀”是指，上述聚合物在电解液中体积发生膨胀的现象。溶胀率＝(浸泡后体积-浸泡前体积)/浸泡前体积×100％。
综上，第一材料层中第一粘结剂的使用，使第一材料层的粘结力提升，增加第一材料层与第二材料层之间的粘结力，使第二材料层中第二粘结剂的用量减少。同时，将第二活性材料的比表面积控制在本申请范围内，也使第二粘结剂的含量减少。第二材料层中第二粘结剂含量的减少，使第二活性材料层中的第二活性材料的相对含量占比增加，从而有效提高了锂离子电池的能量密度。
本申请的一种实施方案中，第一粘结剂在第一材料层中的含量A为1wt％至20wt％。不限于任何理论，当第一粘结剂含量过低，例如低于1wt％，第一正极活性层成膜性差，不利于覆盖度的提升；当第一粘结剂含量过高，例如高于20wt％，由于第一粘结剂本身的粘结力高，导致第一材料层在烘干成膜过程中收缩程度增大，而集流体基材(例如铝箔)基本不收缩，二者收缩率差异大，导致第一材料层大面积从集流体基材上脱落。通过将第一粘结剂的含量控制在上述含量范围内，有利于提高集流体与第一材料层之间的粘结力。
在本申请的一种实施方案中，第一粘结剂中的聚合物还包括丙烯腈单体。
在本申请的一种实施方案中，基于聚合物的总质量，丙烯腈的质量百分含量为30％至70％，丙烯酸盐和丙烯酰胺的质量百分含量之和为30％至70％。优选地，基于所述聚合物的总质量，丙烯腈的质量百分含量为40％至60％，丙烯酸盐和丙烯酰胺的质量百分含量之 和为40％至60％。通过将丙烯腈、丙烯酸盐和丙烯酰胺控制在聚合物总质量的上述范围内，能够使第一粘结剂在使用中具有更好的粘结力。
在本申请中，对第一粘结剂的重均分子量没有特别限制，只要能够实现本申请目的即可，例如，第一粘结剂的重均分子量为100000至2000000。不限于任何理论，第一粘结剂的重均分子量过大，第一粘结剂的增稠作用增强，导致浆料粘度过高、流动性变差，易导致第一正极活性层浆料漏涂；第一粘结剂的重均分子量过小，导致浆料粘度过低，浆料成膜性差，也会导致绝缘层浆料漏涂。通过控制第一粘结剂的重均分子量在上述范围内，能够使第一材料层浆料在集流体基材表面形成厚度均匀的薄膜，从而形成第一材料层，能够提高第一材料层与集流体之间的粘结力。
在本申请的一种实施方案中，第二粘结剂包括包括聚丙烯酸、聚偏氟乙烯、聚四氟乙烯-六氟丙烯、聚丙烯酸钠、丁腈橡胶或聚丙烯酸酯中的至少一种。优选地，第二粘结剂包括聚丙烯酸、聚偏氟乙烯或丁腈橡胶中的至少一种。
在本申请中，对第二粘结剂的重均分子量没有特别限制，只要能够实现本申请目的即可，例如，第二粘结剂的重均分子量为100000至2000000。
在本申请的一种实施方案中，第二粘结剂在第二材料层中的含量B为0.5wt％至10wt％。不限于任何理论，当第二粘结剂含量过低，例如低于0.5wt％，第二材料层粘结力过低，易脱膜，恶化电芯性能第二材料层成膜性差，不利于覆盖度的提升；当第二粘结剂含量过高，例如高于10wt％，由于第二材料层在烘干成膜过程中收缩程度与第一材料层的收缩率程度不同，易导致第二材料层大面积从第一材料层上脱落，第二活性材料含量减少，降低电芯能量密度，同时第二粘结剂含量过高导致正极中离子扩散阻力增加，恶化锂离子电池功率性能。通过将第二粘结剂的含量控制在上述含量范围内，有利于提高第一材料层与第二材料层之间的粘结力。
在本申请的一种实施方案中，第一材料层与第二材料层的粘结力为5N/m以上，表明第一材料层与第二材料层间具有优异的粘结性能。
在本申请的一种实施方案中，第二粘结剂在第二材料层中的含量B为0.5wt％至3.99wt％；第一粘结剂在第一材料层中的含量A与第二粘结剂在第二材料层中的含量B之间满足：B＝n 1×A+n 2，且-0.4≤n 1≤-0.01、0.8％≤n 2≤4％。当第一粘结剂的含量与第二粘结剂的含量满足上述关系时，第一材料层中第一粘结剂含量的增加，能够降低第二材料层 中第二粘结剂的用量，使第二材料层中第二活性材料的相对含量提高，从而提高锂离子电池的能量密度。
在本申请的一种实施方案中，第一材料层的单层厚度为0.01μm至20μm，当第一材料层的厚度过低时，例如低于0.01μm，第一材料层过薄，安全性能受到影响；当第一材料层的厚度过高时，例如高于20μm，正极中第一活性材料相对含量下降，影响锂离子电池的能量密度。
在本申请的一种实施方案中，第二材料层的单层厚度为20μm至300μm，当第二材料层的厚度过低时，例如低于20μm，在容量一定的情况下，影响锂离子电池能量密度，并且不易加工；当第二材料层的厚度过高时，例如高于300μm，恶化锂离子电池动力学。
在本申请的一种实施方案中，正极在电化学装置满充后的电阻为10Ω以上，优选30Ω至100Ω。将正极电阻控制在上述范围内，能够增大锂离子电池短路时的内阻，降低短路电流，降低温升，从而提高锂离子电池的安全性。
在本申请的一种实施方案中，第一导电剂和所述第二导电剂各自独立地包含片层状、网状、线状或零维导电剂中的至少一种。优选地，第一导电剂和第二导电剂各自独立地包含石墨烯、网状石墨纤维、碳纳米管、科琴黑、石墨纤维或纳米颗粒导电碳中的至少一种。通过在第一材料层中添加第一导电剂、在第二材料层中添加第二导电剂，能够有效提高锂离子在第一活性材料和第二活性材料中的迁移速率，从而提高锂离子电池的充放电效率。
本申请的第一粘结剂的制备方法没有特别限制，可以采用本领域技术人员公知的制备方法，例如可以采用如下制备方法：
在反应釜中加入蒸馏水，启动搅拌，通入氮气除氧后，按不同质量比加入丙烯腈、丙烯酸盐和丙烯酰胺等上述组分中的至少一种，在惰性气氛下加热至65℃左右并恒温，然后加入引发剂引发反应，至反应20小时左右后结束。
本申请对引发剂没有特别限制，只要能引发单体聚合即可，例如可以为20％的过硫酸铵溶液。本申请对蒸馏水和引发剂的添加量没有特别限制，只要能保证加入的单体发生聚合反应即可。在反应后，向反应的沉淀物中加入碱液以进行中和，使pH值为6.5至9。然后，对反应产物进行过滤、洗涤、烘干、粉碎、过筛等处理。
本申请的第二粘结剂的制备方法没有特别限制，可以采用本领域技术人员公知的制备方法，例如可以采用如下制备方法：
对含有搅拌器的反应釜抽真空，抽氮气置换氧气后，向反应釜内加入去离子水、偏氟乙烯、引发剂、乳化剂、链转移剂，经聚合反应后得到第二粘结剂。
其中，对引发剂没有特别限制，例如可以选自二异丙苯过氧化氢；对乳化剂没有特别限制，例如可以选自全氟烷基羧酸盐；对链转移剂没有特别限制，例如可以选自异丙醇。只要能实现本申请目的即可。
本申请的正极中，集流体没有特别限制，可以为本领域公知的集流体，例如铝箔、铝合金箔或复合集流体等。第一材料层包括第一活性材料，第二材料层包括第二活性材料，在本申请中，第一活性材料和第二活性材料没有特别限制，可以使用本领域公知的活性材料，例如，第一活性材料可以包括磷酸铁锂、磷酸铁锰锂或锰酸锂中的至少一种，第二活性材料可以包括钴酸锂、镍钴锰酸锂(811、622、523、111)、镍钴铝酸锂、磷酸铁锂、磷酸铁锰锂或锰酸锂中的至少一种。在本申请中，集流体的厚度没有特别限制，只要能够实现本申请目的即可，例如，集流体的厚度为8μm至12μm。
在本申请的正极中，集流体表面设置有第一材料层和第二材料层，而第一材料层和第二材料层通常不会将集流体的表面完全涂满。本领域技术人员可以根据实际需要，在集流体表面未设置有第一材料层和第二材料层的区域中设置绝缘层，在本申请中没有特别限定，只要能够实现本申请目的即可。
本申请的负极没有特别限制，只要能够实现本申请目的即可。例如，负极通常包含集流体和材料层。在本申请负极中，其集流体没有特别限制，可以使用本领域公知的集流体，例如铜箔、铜合金箔以及复合集电体等。所述材料层没有特别限制，可以使用本领域公知的活性材料。例如，可以包括人造石墨、天然石墨、中间相碳微球、硅、硅碳、硅氧化合物、软碳、硬碳、钛酸锂或钛酸铌等中的至少一种。在本申请的负极中，集流体和材料层的厚度没有特别限制，只要能够实现本申请目的即可。例如，集流体的厚度为4μm至10μm，材料层的厚度为30μm至120μm。
任选地，所述负极还可以包含导电层，所述导电层位集流体和材料层之间。所述导电层的组成没有特别限制，可以是本领域常用的导电层。所述导电层包括导电剂和粘结剂。
上述所述导电剂没有特别限制，只要能实现本申请目的即可。例如，导电剂可以包括导电炭黑(Super P)、碳纳米管(CNTs)、碳纤维或石墨烯等中的至少一种。上述所述粘结剂没有特别限制，可以使用本领域公知的粘结剂，只要能实现本申请目的即可。例如，粘 结剂可以包括丁苯橡胶(SBR)、聚乙烯醇(PVA)、聚四氟乙烯(PTFE)或羧甲基纤维素钠(CMC-Na)等中的至少一种。例如，粘结剂可选用丁苯橡胶(SBR)。
本申请的锂离子电池还包括隔离膜，用以分隔正极和负极，防止锂离子电池内部短路，允许电解质离子自由通过，完成电化学充放电过程的作用。在本申请中，隔离膜没有特别限制，只要能够实现本申请目的即可。
例如，聚乙烯(PE)、聚丙烯(PP)为主的聚烯烃(PO)类隔离膜，聚酯膜(例如聚对苯二甲酸二乙酯(PET)膜)、纤维素膜、聚酰亚胺膜(PI)、聚酰胺膜(PA)，氨纶或芳纶膜、织造膜、非织造膜(无纺布)、微孔膜、复合膜、隔膜纸、碾压膜、纺丝膜等中的至少一种。
例如，隔离膜可以包括基材层和表面处理层。基材层可以为具有多孔结构的无纺布、膜或复合膜，基材层的材料可以包括聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯和聚酰亚胺等中的至少一种。任选地，可以使用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。任选地，基材层的至少一个表面上设置有表面处理层，表面处理层可以是聚合物层或无机物层，也可以是混合聚合物与无机物所形成的层。
例如，无机物层包括无机颗粒和粘结剂，所述无机颗粒没有特别限制，例如可以选自氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙和硫酸钡等中的至少一种。所述粘结剂没有特别限制，例如可以选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯和聚六氟丙烯中的一种或几种的组合。聚合物层中包含聚合物，聚合物的材料包括聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚偏氟乙烯或聚(偏氟乙烯-六氟丙烯)等中的至少一种。
本申请的锂离子电池还包括电解质，电解质可以是凝胶电解质、固态电解质和电解液中的一种或多种，电解液包括锂盐和非水溶剂。
在本申请一些实施方案中，锂盐选自LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB和二氟硼酸锂中的 一种或多种。举例来说，锂盐可以选用LiPF 6，因为它可以给出高的离子导电率并改善循环特性。
非水溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物、其它有机溶剂或它们的组合。
上述碳酸酯化合物可为链状碳酸酯化合物、环状碳酸酯化合物、氟代碳酸酯化合物或其组合。
上述链状碳酸酯化合物的实例为碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸甲乙酯(MEC)及其组合。环状碳酸酯化合物的实例为碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)、碳酸乙烯基亚乙酯(VEC)及其组合。氟代碳酸酯化合物的实例为碳酸氟代亚乙酯(FEC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯、碳酸三氟甲基亚乙酯及其组合。
上述羧酸酯化合物的实例为甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯、甲瓦龙酸内酯、己内酯及其组合。
上述醚化合物的实例为二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基乙烷、2-甲基四氢呋喃、四氢呋喃及其组合。
上述其它有机溶剂的实例为二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯、和磷酸酯及其组合。
本申请的第二方面提供了一种电子装置，包括本申请第一方面提供的电化学装置。
本申请的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，电子装置可以包括，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
电化学装置的制备过程为本领域技术人员所熟知的，本申请没有特别的限制。例如电化学装置可以通过以下过程制造：将正极和负极经由隔离膜重叠，并根据需要将其卷绕、折叠等操作后放入壳体内，将电解液注入壳体并封口。此外，也可以根据需要将防过电流元件、导板等置于壳体中，从而防止电化学装置内部的压力上升、过充放电。
本申请提供了一种电化学装置和电子装置，其包括正极，该正极包括集流体、第一材料层和第二材料层，该集流体的至少一个表面上设置有第二材料层，该第一材料层设置在集流体和第二材料层之间，该第二材料层包含第二活性材料、第二导电剂和第二粘结剂，第二活性材料的比表面积为0.05m 2/g至20m 2/g；该第一材料层包含第一活性材料、第一导电剂和第一粘结剂，该第一粘结剂包含丙烯酸盐或丙烯酰胺中的至少一种单体聚合而成的聚合物。通过上述设计，显著增加了正极中第一材料层对第二材料层的粘结力，使正极的第二材料层中第二粘结剂的含量减少、第二活性材料的相对含量占比增加，将该正极应用于电化学装置中，能够有效提升电化学装置的能量密度。
附图说明
为了更清楚地说明本申请和现有技术的技术方案，下面对实施例和现有技术中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例。
图1为本申请的一种实施方案的正极结构示意图；
图2为本申请的另一种实施方案的正极结构示意图；
图3为在粘结力测试中粘结力与行程之间的关系。
附图标记：10.集流体，21.第一材料层，22.第二材料层。
具体实施方式
为使本申请的目的、技术方案、及优点更加清楚明白，以下参照附图和实施例，对本申请进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员所获得的所有其他技术方案，都属于本申请保护的范围。
需要说明的是，本申请的具体实施方式中，以锂离子电池作为电化学装置的例子来解释本申请，但是本申请的电化学装置并不仅限于锂离子电池。
图1示出了本申请一种实施方案的正极结构示意图，集流体10的第一表面、第二表 面均设置有第一材料层21和第二材料层22，其中集流体10的第一表面设置有第一材料层21和第二材料层22的区域面积大于集流体10的第二表面，当然，集流体10的第一表面设置有第一材料层21和第二材料层22的区域面积也可以小于集流体10的第二表面；且第一材料层21均设置于集流体10和第二材料层22之间。
图2示出了本申请另一种实施方案的正极结构示意图，仅在集流体10的第一表面设置有第一材料层21和第二材料层22。当然，也可以在集流体10的第二表面设置有第一材料层21和第二材料层22。
图3示出了本申请在粘结力测试时粘结力与行程之间的关系。
实施例
以下，举出实施例及对比例来对本申请的实施方式进行更具体地说明。各种的试验及评价按照下述的方法进行。另外，只要无特别说明，“份”、“％”为质量基准。
测试方法和设备：
第一粘结剂重均分子量测试：
采用凝胶渗透色谱法(GPC)测试第一材料层中的第一粘结剂的重均分子量。本申请中，重均分子量是指按质量统计平均的分子量。
比表面积(BET)测试：
采用氮气吸附法测试第二活性材料的比表面积。
粘结力测试：
使用高铁拉力机、90°角法测试第一材料层与第二材料层之间的粘结力：将成品锂离子电池中设置有第一材料层部分的正极极片裁切为20mm×60mm的条状样品，其长宽值可根据实际情况按比例调整。沿样品的长度方向，从样品的一端将该样品的一部分通过双面胶粘附在钢板上，其中粘附长度不低于40mm；然后将钢板固定在高铁拉力机的相应位置，拉起未被粘附在钢板上的另一端，通过连接物或直接将样品放入夹头内夹紧，其中被拉起的试样部分与钢板在空间上夹角为90°。夹头以5mm/min的速度拉动样品，使第一材料层与第二材料层分离，最终测得平稳区域的拉力平均值记为第一材料层与第二材料层之间的粘结力。如图3所示，要求上述平稳区域的粘结力数据的标准差与平均值的比值不超过10％。
第一材料层和第二材料层的厚度测试：
1)将涂有第一材料层和第二材料层的正极从成品锂离子电池中拆出；
2)使用等离子体切割技术，沿正极厚度方向切割1)中所得正极，得到第一材料层和第二材料层的横截面；
3)在SEM(电子显微镜)下，观察2)中所得第一材料层和第二材料层的横截面(要求所观察的横截面长度需不少于2cm)，在SEM下分别测试第一材料层、第二材料层的单面厚度，相邻测试点间隔2mm至3mm，至少测试15个不同点，记各层所有测试位置的厚度均值为对应层的厚度值。
正极满充内阻测试：
1)0.05C的倍率恒流充电至电压为4.45V(即满充电压)，随后以4.45V恒压充电至电流为0.025C(截止电流)，使锂离子电池达到满充状态
2)将锂离子电池拆解，得到正极；
3)将2)中所得正极在DMC(碳酸二甲酯)中25℃浸泡1h后，在通风橱中晾干；
4)使用BER1200型号膜片电阻测试仪测试3)中所得正极极片电阻，相邻测试点间隔2mm至3mm，至少测试15个不同点，记所有测试点的电阻均值为正极极片的膜片电阻。其中参数为：压头面积153.94mm 2，压力3.5t，保持时间50s。
冲击测试：
在20±5℃环境下，将待测的锂离子电池以0.05C的倍率恒流充电至电压为4.45V(即满充电压)，随后以4.45V恒压充电至电流为0.025C(截止电流)，使锂离子电池达到满充状态，记录测试前锂离子电池外观。在将直径15.8±0.1mm圆棒放置在电池中心，重9.1±0.46kg铁块从610±25mm高度落到电池上，在此过程中被冲击样品不起火、不爆炸视为通过冲击测试。
实施例1
<第一粘结剂的制备>
在反应釜中加入蒸馏水并启动搅拌，通入氮气除氧2h后，按质量比40:45:15向反应釜加入以下单体丙烯腈、丙烯酸钠和丙烯酰胺，在惰性气氛下加热至65℃并保持恒温，然 后加入20％的过硫酸铵溶液作为引发剂开始反应，至反应22小时后取出沉淀物，加入碱液中和pH至6.5。其中，蒸馏水、单体、引发剂之间的质量比为89.5︰10︰0.5。反应后对反应产物进行过滤、洗涤、烘干、粉碎、过筛等处理，得到第一粘结剂。
<第二粘结剂的制备>
对含有搅拌器的反应釜抽真空，抽氮气置换氧气后，向反应釜内加入去离子水、偏氟乙烯、引发剂二异丙苯过氧化氢、乳化剂全氟烷基羧酸盐、链转移剂异丙醇至反应釜压力为3.5MPa，其中去离子水为偏氟乙烯单体质量的7倍，引发剂占偏氟乙烯单体质量的0.2％，乳化剂占偏氟乙烯单体质量的0.5％，链转移剂占偏氟乙烯单体质量的5％。然后升温至60℃，搅拌器转速80r/min，开始聚合反应，同时不断补加偏氟乙烯单体保持反应釜压力3.5MPa，直到反应器中乳液固含量达到25％停止反应，回收未反应单体，放出聚合物乳液，经离心、洗涤、干燥后，得到聚偏氟乙烯。
<正极的制备>
将第一活性材料磷酸铁锂、第一粘结剂、第一导电剂纳米颗粒导电碳和碳纳米管按质量比95.8∶3.0∶0.7∶0.5混合，然后加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成固含量为35％的浆料，并搅拌均匀。将浆料均匀涂覆在厚度10μm的集流体铝箔上，90℃条件下烘干，得到厚度为5μm的第一材料层；其中，第一粘结剂的重均分子量为500000；
将第二活性材料钴酸锂(LCO)、第二粘结剂聚偏氟乙烯(PVDF)、第二导电剂导电炭黑和碳纳米管按质量比97.3∶1.6∶0.6∶0.5混合，然后加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成固含量为75％的浆料，并搅拌均匀。将浆料均匀涂覆在第一材料层上，90℃条件下烘干，得到厚度为85μm的第二材料层，其中，第二活性材料的比表面积为2.0m 2/g；
然后在该正极的另一个表面上重复以上步骤，得到双面涂覆有第一材料层和第二正极层的正极。将正极裁切成74mm×867mm的规格并焊接极耳后待用。
<负极的制备>
将活性材料石墨、苯乙烯-丁二烯聚合物和羧甲基纤维素钠按照重量比97.5︰1.3︰1.2进行混合，加入去离子水作为溶剂，调配成为固含量为70％的浆料，并搅拌均匀。将浆料均匀涂覆在负极集流体铜箔上，110℃条件下烘干，冷压后得到材料层厚度为150μm的单面涂覆材料层的负极。
以上步骤完成后，采用同样的方法在该负极背面也完成这些步骤，即得到双面涂布完成的负极。涂布完成后，将负极裁切成规格为76mm×851mm的片材并焊接极耳待用。
<电解液的制备>
在干燥氩气气氛中，将有机溶剂碳酸乙烯酯、碳酸甲乙酯和碳酸二乙酯以质量比EC︰EMC︰DEC＝30︰50︰20混合得到有机溶液，然后向有机溶剂中加入锂盐六氟磷酸锂溶解并混合均匀，得到锂盐的浓度为1.15Mol/L的电解液。
<隔离膜的制备>
将氧化铝与聚偏氟乙烯依照质量比90∶10混合并将其溶入到去离子水中以形成固含量为50％的陶瓷浆料。随后采用微凹涂布法将陶瓷浆料均匀涂布到多孔基材(聚乙烯，厚度7μm，平均孔径为0.073μm，孔隙率为26％)的其中一面上，经过干燥处理以获得陶瓷涂层与多孔基材的双层结构，陶瓷涂层的厚度为50μm。
将聚偏二氟乙烯(PVDF)与聚丙烯酸酯依照质量比96∶4混合并将其溶入到去离子水中以形成固含量为50％的聚合物浆料。随后采用微凹涂布法将聚合物浆料均匀涂布到上述陶瓷涂层与多孔基材双层结构的两个表面上，经过干燥处理以获得隔离膜，其中聚合物浆料形成的单层涂层厚度为2μm。
<锂离子电池的制备>
将上述制备的正极、隔离膜、负极按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到电极组件。将电极组件装入铝塑膜包装袋中，并在80℃下脱去水分，注入配好的电解液，经过真空封装、静置、化成、整形等工序得到锂离子电池。
实施例2
除了在<正极的制备>中，控制第二活性材料的比表面积为0.05m 2/g以外，其余与实施例1相同。
实施例3
除了在<正极的制备>中，控制第二活性材料的比表面积为0.1m 2/g以外，其余与实施例1相同。
实施例4
除了在<正极的制备>中，控制第二活性材料的比表面积为4.0m 2/g以外，其余与实施例1相同。
实施例5
除了在<正极的制备>中，控制第二活性材料的比表面积为8.0m 2/g以外，其余与实施例1相同。
实施例6
除了在<正极的制备>中，控制第二活性材料的比表面积为15m 2/g以外，其余与实施例1相同。
实施例7
除了在<正极的制备>中，控制第二活性材料的比表面积为20m 2/g以外，其余与实施例1相同。
实施例8
除了在<第一粘结剂的制备>中，粘结剂选用聚丙烯酸钠以外，其余与实施例1相同。
实施例9
除了在<第一粘结剂的制备>中，单体选用质量比为40:60的丙烯酰胺和丙烯酸钠以外，其余与实施例1相同。
实施例10
除了在<第一粘结剂的制备>中，单体选用质量比为40:60的丙烯腈和丙烯酰胺以外，其余与实施例1相同。
实施例11
除了在<第一粘结剂的制备>中，单体选用质量比为40:60的丙烯腈和丙烯酸钠以外，其余与实施例1相同。
实施例12
除了在<第一粘结剂的制备>中，单体选用质量比为30:60:10的丙烯腈、丙烯酸钠和丙烯酰胺以外，其余与实施例1相同。
实施例13
除了在<第一粘结剂的制备>中，单体选用质量比为30:10:60的丙烯腈、丙烯酸钠和丙烯酰胺以外，其余与实施例1相同。
实施例14
除了在<第一粘结剂的制备>中，单体选用质量比为50:40:10的丙烯腈、丙烯酸钠和丙烯酰胺以外，其余与实施例1相同。
实施例15
除了在<第一粘结剂的制备>中，单体选用质量比为60:10:30的丙烯腈、丙烯酸钠和丙烯酰胺以外，其余与实施例1相同。
实施例16
除了在<第一粘结剂的制备>中，单体选用质量比为70:20:10的丙烯腈、丙烯酸钠和丙烯酰胺以外，其余与实施例1相同。
实施例17
除了在<正极的制备>中，第一活性材料与第一粘结剂的质量比为97.8:1.0以外，其余与实施例1相同。
实施例18
除了在<正极的制备>中，第一活性材料与第一粘结剂的质量比为93.8:5.0以外，其余与实施例1相同。
实施例19
除了在<正极的制备>中，第一活性材料与第一粘结剂的质量比为88.8:10.0以外，其余与实施例1相同。
实施例20
除了在<正极的制备>中，第一活性材料与第一粘结剂的质量比为83.8:15.0以外，其余与实施例1相同。
实施例21
除了在<正极的制备>中，第一活性材料与第一粘结剂的质量比为78.8:20.0以外，其余与实施例1相同。
实施例22
除了在<正极的制备>中，第一粘结剂的重均分子量为100000以外，其余与实施例1相同。
实施例23
除了在<正极的制备>中，第一粘结剂的重均分子量为800000以外，其余与实施例1相同。
实施例24
除了在<正极的制备>中，第一粘结剂的重均分子量为1000000以外，其余与实施例1相同。
实施例25
除了在<正极的制备>中，第一粘结剂的重均分子量为1400000以外，其余与实施例1相同。
实施例26
除了在<正极的制备>中，第一粘结剂的重均分子量为2000000以外，其余与实施例1相同。
实施例27
除了在<正极的制备>中，第二粘结剂选用丁腈橡胶以外，其余与实施例1相同。
实施例28
除了在<正极的制备>中，第二活性材料与第二粘结剂的质量比为98.4:0.5以外，其余与实施例1相同。
实施例29
除了在<正极的制备>中，第二活性材料与第二粘结剂的质量比为93.9:5.0以外，其余与实施例1相同。
实施例30
除了在<正极的制备>中，第二活性材料与第二粘结剂的质量比为88.9:10以外，其余与实施例1相同。
实施例31
除了在<正极的制备>中，磷酸铁锂和第一粘结剂的质量比为97.8:1.0、钴酸锂和第二粘结剂的质量比为96.3:2.6、n1＝-0.4、n2＝3％以外，其余与实施例1相同。
实施例32
除了在<正极的制备>中，磷酸铁锂和第一粘结剂的质量比为96.8:2.0、钴酸锂和第二粘结剂的质量比为96.7:2.2以外，其余与实施例31相同。
实施例33
除了在<正极的制备>中，钴酸锂和第二粘结剂的质量比为97.1:1.8、n1＝-0.2、n2＝2.4％以外，其余与实施例1相同。
实施例34
除了在<正极的制备>中，磷酸铁锂和第一粘结剂的质量比为94.8:4.0、钴酸锂和第二粘结剂的质量比为97.3:1.6以外，其余与实施例33相同。
实施例35
除了在<正极的制备>中，磷酸铁锂和第一粘结剂的质量比为93.8:5.0、钴酸锂和第二粘结剂的质量比为97.5:1.4以外，其余与实施例33相同。
实施例36
除了在<正极的制备>中，磷酸铁锂和第一粘结剂的质量比为82.8:16、钴酸锂和第二粘结剂的质量比为98.26:0.64、n1＝-0.01、n2＝0.8％以外，其余与实施例1相同。
实施例37
除了在<正极的制备>中，磷酸铁锂和第一粘结剂的质量比为80.8:18、钴酸锂和第二粘结剂的质量比为98.28:0.62以外，其余与实施例36相同。
实施例38
除了在<正极的制备>中，磷酸铁锂和第一粘结剂的质量比为78.8:20、钴酸锂和第二粘结剂的质量比为98.3:0.6以外，其余与实施例36相同。
实施例39
除了在<正极的制备>中，磷酸铁锂和第一粘结剂的质量比为97.8:1.0、钴酸锂和第二粘结剂的质量比为94.91:3.99、n1＝-0.01、n2＝4.0％以外，其余与实施例1相同。
实施例40
除了在<正极的制备>中，磷酸铁锂和第一粘结剂的质量比为78.8:20、钴酸锂和第二粘结剂的质量比为95.1:3.8以外，其余与实施例39相同。
对比例1
除了在<正极的制备>中，第二活性材料的比表面积为40m 2/g以外，其余与实施例1相同。
对比例2
除了在<第一粘结剂的制备>中，粘结剂选用聚偏氟乙烯以外，其余与实施例1相同。
对比例3
除了在<正极的制备>中，第一粘结剂的重均分子量为2500000以外，其余与实施例1相同。
各实施例和对比例的制备参数及测试结果如下表1-3所示。
表1实施例1-21和对比例1-2的制备参数和测试结果
Figure PCTCN2020142392-appb-000001
Figure PCTCN2020142392-appb-000002
表2实施例22-30和对比例3的制备参数和测试结果
Figure PCTCN2020142392-appb-000003
表3实施例31-40的制备参数和测试结果
Figure PCTCN2020142392-appb-000004
从实施例1-7和对比例1可以看出，本申请的第二活性材料的比表面积在本申请限定范围内的锂离子电池，第一材料层和第二材料层之间的粘结力明显提升，尤其是实施例3，其第一材料层和第二材料层之间的粘结力达到35N/m以上，将使第二材料层中第二粘结剂的含量减少、第二材料层中第二活性材料的相对含量占比增加，有利于锂离子电池能量密度的提升；并且穿钉测试通过率明显提高，能够有效提升锂离子电池的安全性。
从实施例8-21和对比例2可以看出，第一材料层中包含本申请的第一粘结剂，并且第一粘结剂的含量在本申请限定范围内的锂离子电池，第一材料层和第二材料层之间的粘结力明显提升，尤其是实施例14-15和实施例18-21，该第一材料层和第二材料层之间的粘结力达到30N/m以上，最高可达55N/m，将使第二材料层中第二粘结剂的含量减少、第二材料层中第二活性材料的相对含量占比增加，有利于锂离子电池能量密度的提升；并且穿钉测试通过率明显提高，能够有效提升锂离子电池的安全性。
从实施例22-26和对比例3可以看出，在本申请第二粘结剂成分相同、含量相同的情况下，本申请第一粘结剂重均分子量在本申请限定范围内的锂离子电池，第一材料层和第二材料层之间的粘结力明显提升，尤其是实施例25-26，其第一材料层和第二材料层之间的粘结力达到40N/m以上，将使第二材料层中第二粘结剂的含量减少、第二材料层中第二活性材料的相对含量占比增加，有利于锂离子电池能量密度的提升；并且穿钉测试通过率明显提高，能够有效提升锂离子电池的安全性。
从实施例27-30可以看出，将第二粘结剂的含量控制在本申请范围内，能够有效提高提高第一材料层和第二材料层之间的粘结力，从而提高锂离子电池的能量密度和安全性。
从实施例31-40可以看出，n1、n2取相同系数值时，第一粘结剂含量A的增加，使第一材料层与第二材料层之间的粘结力增加、同时使第二材料层中第二粘结剂的含量B减少，从而使第二材料层中第二活性材料的相对含量增加，有利于锂离子电池能量密度的提升；并且穿钉测试通过率明显提高，能够有效提升锂离子电池的安全性。
以上所述仅为本申请的较佳实施例，并不用以限制本申请，凡在本申请的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本申请保护的范围之内。

Claims (14)

  1. 一种电化学装置，包括正极，所述正极包括集流体、第一材料层和第二材料层，所述集流体的至少一个表面上设置有所述第二材料层，所述第一材料层设置在所述集流体和所述第二材料层之间；所述第二材料层包含第二活性材料、第二导电剂和第二粘结剂；其中，所述第二活性材料的比表面积为0.05m 2/g至20m 2/g；所述第一材料层包含第一活性材料、第一导电剂和第一粘结剂，所述第一粘结剂包含丙烯酸盐或丙烯酰胺中的至少一种单体聚合而成的聚合物。
  2. 根据权利要求1所述的电化学装置，其中，所述第一粘结剂在所述第一材料层中的含量A为1wt％至20wt％。
  3. 根据权利要求1所述的电化学装置，其中，所述第一粘结剂中的聚合物还包括丙烯腈单体。
  4. 根据权利要求3所述的电化学装置，其中，基于所述聚合物的总质量，所述丙烯腈的质量百分含量为30％至70％，所述丙烯酸盐和丙烯酰胺的质量百分含量之和为30％至70％。
  5. 根据权利要求1所述的电化学装置，其中，所述第一粘结剂的重均分子量为100000至2000000。
  6. 根据权利要求1所述的电化学装置，其中，所述第二粘结剂包括聚丙烯酸、聚偏氟乙烯、聚四氟乙烯-六氟丙烯、聚丙烯酸钠、丁腈橡胶或聚丙烯酸酯中的至少一种。
  7. 根据权利要求2所述的电化学装置，其中，所述第二粘结剂在所述第二材料层中的含量B为0.5wt％至10wt％。
  8. 根据权利要求1所述的电化学装置，其中，所述第一材料层与所述第二材料层的粘结力为5N/m以上。
  9. 根据权利要求7所述的电化学装置，其中，所述第二粘结剂在所述第二材料层中的含量B为0.5wt％至3.99wt％；
    所述第一粘结剂在所述第一材料层中的含量A与所述第二粘结剂在所述第二材料层中的含量B之间满足：
    B＝n 1×A+n 2，且-0.4≤n 1≤-0.01、0.8％≤n 2≤4％。
  10. 根据权利要求1所述的电化学装置，其中，所述第一材料层的单层厚度为0.01μm至20μm，所述第二材料层的单层厚度为20μm至300μm。
  11. 根据权利要求1所述的电化学装置，其中，所述正极在所述电化学装置满充后的电阻为10Ω以上。
  12. 根据权利要求1所述的电化学装置，其中，所述第一导电剂和所述第二导电剂各自独立地包含片层状、网状、线状或零维导电剂中的至少一种。
  13. 根据权利要求1或3所述的电化学装置，其中，所述电化学装置满足以下特征中的至少一者：
    (a)基于所述聚合物的总质量，所述丙烯腈的质量百分含量为40％至60％，所述丙烯酸盐和丙烯酰胺的质量百分含量之和为40％至60％；
    (b)所述第二粘结剂包括聚丙烯酸、聚偏氟乙烯或丁腈橡胶中的至少一种；
    (c)所述第一导电剂和所述第二导电剂各自独立地包含石墨烯、网状石墨纤维、碳纳米管、科琴黑、石墨纤维或纳米颗粒导电碳中的至少一种。
  14. 一种电子装置，其包含权利要求1至13任意一项所述的电化学装置。
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WO2023184228A1 (zh) * 2022-03-30 2023-10-05 宁德新能源科技有限公司 一种电化学装置及电子装置
CN117015866A (zh) * 2022-03-30 2023-11-07 宁德新能源科技有限公司 一种使用安全涂层的电化学装置及电子装置
CN117117086B (zh) * 2023-10-24 2024-03-29 宁德时代新能源科技股份有限公司 一种正极片、电池单体、电池及用电装置

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