WO2021237466A1 - 正极及使用其的电化学装置和电子装置 - Google Patents

正极及使用其的电化学装置和电子装置 Download PDF

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WO2021237466A1
WO2021237466A1 PCT/CN2020/092382 CN2020092382W WO2021237466A1 WO 2021237466 A1 WO2021237466 A1 WO 2021237466A1 CN 2020092382 W CN2020092382 W CN 2020092382W WO 2021237466 A1 WO2021237466 A1 WO 2021237466A1
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positive electrode
lithium
active material
layer
conductive layer
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PCT/CN2020/092382
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English (en)
French (fr)
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韩冬冬
王可飞
张青文
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宁德新能源科技有限公司
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Priority to EP20937631.8A priority Critical patent/EP4024506A4/en
Priority to CN202080047826.7A priority patent/CN114072933A/zh
Priority to PCT/CN2020/092382 priority patent/WO2021237466A1/zh
Publication of WO2021237466A1 publication Critical patent/WO2021237466A1/zh
Priority to US17/710,160 priority patent/US20220223844A1/en

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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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • H01M4/623—Binders being polymers fluorinated polymers
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes

Definitions

  • This application relates to the field of energy storage, in particular to a positive electrode and an electrochemical device and electronic device using the same.
  • Electrochemical devices e.g., lithium-ion batteries
  • wearable devices smart phones, drones, electric vehicles, and large-scale energy storage devices due to their advantages of high energy density, long cycle life, and no memory effect.
  • How to improve the safety performance and cyclic storage performance of lithium-ion batteries has become an urgent technical problem to be solved. Improving the pole piece is one of the means to solve the above-mentioned problems.
  • the present application attempts to solve at least one problem in the related field at least to some extent by providing an electrochemical device and an electronic device having a positive electrode and using the same.
  • the application provides a positive electrode, which includes a positive electrode current collector, a positive electrode active material layer, an adhesive layer, and a conductive layer.
  • the adhesive layer is disposed on the positive electrode current collector and the positive electrode active material layer.
  • the conductive layer is disposed between the adhesive layer and the positive active material layer, wherein the conductive layer includes a conductive agent and a first binder, and is based on the total weight of the conductive layer
  • the content of the conductive agent is 20 wt% to 95 wt%
  • the content of the first binder is 5 wt% to 80 wt%.
  • the conductive layer further includes a first positive active material, and based on the total weight of the conductive layer, the content of the first positive active material is not more than 75 wt%.
  • the thickness of the conductive layer is 0.01 ⁇ m to 10 ⁇ m.
  • the adhesion layer includes a second binder
  • the positive active material layer includes a third binder
  • the content of the second binder in the adhesion layer is greater than that of the second binder.
  • the content of the third binder in the positive electrode active material layer is greater than that of the second binder.
  • the adhesive layer further includes a second positive electrode active material selected from the group consisting of lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium manganate, lithium iron manganese phosphate, At least one of lithium vanadium phosphate, lithium vanadyl phosphate, lithium iron phosphate, lithium titanate, and lithium-rich manganese-based materials.
  • a second positive electrode active material selected from the group consisting of lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium manganate, lithium iron manganese phosphate, At least one of lithium vanadium phosphate, lithium vanadyl phosphate, lithium iron phosphate, lithium titanate, and lithium-rich manganese-based materials.
  • the positive active material layer, the adhesive layer, and the conductive layer are disposed on one side of the positive current collector.
  • both sides of the positive electrode current collector are provided with the positive electrode active material layer, the adhesive layer, and the conductive layer.
  • the conductive agent is selected from at least one of carbon black, acetylene black, carbon nanotubes, conductive graphite, and graphene.
  • the first binder is selected from at least polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene butadiene rubber, polyurethane, fluorinated rubber, and polyvinyl alcohol. A sort of.
  • the first positive electrode active material is selected from at least one of lithium cobalt oxide, lithium nickel cobalt manganate, lithium iron phosphate, and lithium manganate.
  • the present application provides an electrochemical device, which includes the positive electrode, the negative electrode, and the electrolyte according to the present application.
  • the present application provides an electronic device, which includes the electrochemical device according to the present application.
  • Fig. 1 shows a schematic structural diagram of a positive electrode according to an embodiment of the present application.
  • Fig. 2 shows a schematic structural diagram of another positive electrode according to an embodiment of the present application.
  • a list of items connected by the term "at least one of” can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (exclude B); B and C (exclude A); or all of A, B, and C.
  • Project A can contain a single element or multiple elements.
  • Project B can contain a single element or multiple elements.
  • Project C can contain a single element or multiple elements.
  • the present application provides a positive electrode, which includes a positive electrode current collector, a positive electrode active material layer, an adhesive layer, and a conductive layer.
  • the adhesive layer is disposed on the positive electrode.
  • FIG. 1 shows a schematic diagram of the structure of a positive electrode according to an embodiment of the present application.
  • the positive electrode includes a positive electrode current collector 1, a positive electrode active material layer 2, an adhesive layer 3 and a conductive layer 4.
  • the content of the conductive agent is 30 wt% to 90 wt% based on the total weight of the conductive layer. In some embodiments, the content of the conductive agent is 30 wt% to 80 wt% based on the total weight of the conductive layer. In some embodiments, the content of the conductive agent is 40 wt% to 70 wt% based on the total weight of the conductive layer. In some embodiments, based on the total weight of the conductive layer, the content of the conductive agent is 50 wt% to 60 wt%.
  • the content of the conductive agent is 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt% %, 70% by weight, 75% by weight, 80% by weight, 85% by weight, 90% by weight, 95% by weight, or within a range composed of any two of the foregoing values.
  • the content of the first binder is 10 wt% to 70 wt%. In some embodiments, the content of the first binder is 20-60% by weight based on the total weight of the conductive layer. In some embodiments, based on the total weight of the conductive layer, the content of the first binder is 30 wt% to 50 wt%.
  • the content of the first binder is 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt% %, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt% or within the range composed of any two of the above values.
  • the conductive agent can provide conductivity for the conductive layer, and it has the function of connecting the interfaces on both sides of the conductive layer and helps to improve the interface resistance.
  • the presence of the first binder can bond the conductive layer with the positive electrode current collector.
  • the content of the first binder in the conductive layer is higher (that is, the content of the conductive agent is lower), the adhesion of the conductive layer increases, but the conductivity decreases.
  • the electrochemical device expands during cycling, It may cause the connection between the conductive agents to be broken, and the function of the conductive layer will disappear.
  • the content of the first binder and the content of the conductive agent in the conductive layer are within the above range, there are enough conductive sites in the conductive layer, which can avoid the problem of the conductive agent being unable to connect due to expansion during the cycle of the electrochemical device, thereby It can significantly reduce the cycle performance and high-temperature storage performance of the electrochemical device.
  • the conductive layer further includes a first positive active material, and based on the total weight of the conductive layer, the content of the first positive active material is not more than 75 wt%. In some embodiments, based on the total weight of the conductive layer, the content of the first positive active material is not more than 70 wt%. In some embodiments, based on the total weight of the conductive layer, the content of the first positive active material is not more than 60 wt%. In some embodiments, based on the total weight of the conductive layer, the content of the first positive active material is not more than 50 wt%.
  • the content of the first positive active material is not more than 30 wt%. In some embodiments, based on the total weight of the conductive layer, the content of the first positive active material is not more than 20 wt%. In some embodiments, based on the total weight of the conductive layer, the content of the first positive active material is not more than 10 wt%.
  • the content of the first positive active material is 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt% %, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt% or within the range composed of any two of the above values.
  • the conductive layer contains the first positive electrode active material having the above content, the cycle performance and high-temperature storage performance of the electrochemical device can be further improved.
  • the thickness of the conductive layer is 0.01 ⁇ m to 10 ⁇ m. In some embodiments, the thickness of the conductive layer is 0.05 ⁇ m to 8 ⁇ m. In some embodiments, the thickness of the conductive layer is 0.1 ⁇ m to 6 ⁇ m. In some embodiments, the thickness of the conductive layer is 0.5 ⁇ m to 5 ⁇ m. In some embodiments, the thickness of the conductive layer is 1 ⁇ m to 3 ⁇ m.
  • the thickness of the conductive layer is 0.01 ⁇ m, 0.05 ⁇ m, 0.1 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, or any two of the foregoing. Within the range of numerical values. When the thickness of the conductive layer is within the above range, the cycle performance and high-temperature storage performance of the electrochemical device can be further improved.
  • the positive active material layer, the adhesive layer, and the conductive layer are disposed on one side of the positive current collector. As shown in FIG. 1, the positive electrode active material layer 2, the adhesive layer 3 and the conductive layer 4 are provided only on one side of the positive electrode current collector 1.
  • both sides of the positive electrode current collector are provided with the positive electrode active material layer, the adhesive layer, and the conductive layer. As shown in FIG. 2, both sides of the positive electrode current collector 1 are provided. A positive electrode active material layer 2, an adhesive layer 3, and a conductive layer 4 are provided.
  • the conductive agent is selected from at least one of carbon black, acetylene black, carbon nanotubes, conductive graphite, and graphene.
  • the first binder is selected from at least polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene butadiene rubber, polyurethane, fluorinated rubber, and polyvinyl alcohol. A sort of.
  • the first positive electrode active material is selected from at least one of lithium cobalt oxide, lithium nickel cobalt manganate, lithium iron phosphate, and lithium manganate.
  • the adhesion layer includes a second binder
  • the positive active material layer includes a third binder
  • the content of the second binder in the adhesion layer is greater than that of the second binder.
  • the high binder content in the adhesion layer helps to improve the adhesion of the adhesion layer, and can ensure that the adhesion layer and the positive current collector (aluminum substrate) have a strong adhesion force, thereby avoiding electricity
  • the adhesive layer separates from the positive electrode current collector, so that the positive electrode current collector does not directly contact the negative electrode active material layer, thereby reducing the risk of short circuit.
  • the second active material in the adhesive layer has a suitable internal resistance at high voltage, which can reduce the instantaneous discharge current when the electrochemical device is short-circuited by external force. As a result, the safety of the electrochemical device can be improved.
  • the positive electrode active material layer has a relatively low content of binder, which can ensure the compaction density of the entire positive electrode and the positive electrode active material content of the positive electrode active material, thereby ensuring the energy density of the electrochemical device.
  • the ratio of the content of the second binder in the adhesive layer to the content of the third binder in the positive active material layer is in the range of 1.1 to 4. In some embodiments, the ratio of the content of the second binder in the adhesive layer to the content of the third binder in the positive active material layer is in the range of 1.5 to 3. In some embodiments, the ratio of the content of the second binder in the adhesive layer to the content of the third binder in the positive active material layer is in the range of 2 to 2.5.
  • the ratio of the content of the second binder in the adhesive layer to the content of the third binder in the positive active material layer is 1.1, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4 or within the range of any two of the above values.
  • the adhesive layer can effectively protect the positive electrode current collector, and the positive electrode active material layer can Maintaining high energy density helps improve the safety of electrochemical devices while maintaining high energy density.
  • the content of the third binder in the positive electrode active material layer is 0.1 wt% to 5 wt%. In some embodiments, based on the total weight of the positive electrode, the content of the third binder in the positive electrode active material layer is 0.5 wt% to 4 wt%. In some embodiments, based on the total weight of the positive electrode, the content of the third binder in the positive active material layer is 1 wt% to 3 wt%. In some embodiments, based on the total weight of the positive electrode, the content of the third binder in the positive active material layer is 2 wt% to 2.5 wt%.
  • the content of the third binder in the positive active material layer is 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt% or within the range composed of any two of the above values.
  • the content of the second binder in the adhesive layer is 0.11 wt% to 20 wt%. In some embodiments, based on the total weight of the positive electrode, the content of the second binder in the adhesive layer is 0.2 wt% to 18 wt%. In some embodiments, based on the total weight of the positive electrode, the content of the second binder in the adhesive layer is 0.5 wt% to 15 wt%. In some embodiments, based on the total weight of the positive electrode, the content of the second binder in the adhesive layer is 1 wt% to 10 wt%.
  • the content of the second binder in the adhesive layer is 3 wt% to 5 wt%. In some embodiments, based on the total weight of the positive electrode, the content of the second binder in the adhesive layer is 0.11wt%, 0.3wt%, 0.5wt%, 1wt%, 3wt%, 5wt% %, 8% by weight, 10% by weight, 12% by weight, 15% by weight, 18% by weight, 20% by weight, or within a range composed of any two of the foregoing values.
  • the thickness of the adhesive layer is 0.01 ⁇ m to 15 ⁇ m. In some embodiments, the thickness of the adhesive layer is 0.05 ⁇ m to 10 ⁇ m. In some embodiments, the thickness of the adhesive layer is 0.1 ⁇ m to 8 ⁇ m. In some embodiments, the thickness of the adhesive layer is 0.5 ⁇ m to 5 ⁇ m. In some embodiments, the thickness of the adhesive layer is 1 ⁇ m to 3 ⁇ m. In some embodiments, the thickness of the adhesive layer is 1 ⁇ m to 2 ⁇ m.
  • the thickness of the adhesive layer is 0.01 ⁇ m, 0.05 ⁇ m, 0.1 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m or within the range of any two of the above values.
  • the second binder includes polyvinylidene fluoride, vinylidene fluoride-fluorinated olefin copolymer, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene butadiene rubber, polyurethane, At least one of fluorinated rubber or polyvinyl alcohol.
  • the third adhesive is the same as or different from the second adhesive.
  • the adhesive layer further includes a second positive electrode active material selected from the group consisting of lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium manganate, lithium iron manganese phosphate, At least one of lithium vanadium phosphate, lithium vanadyl phosphate, lithium iron phosphate, lithium titanate, and lithium-rich manganese-based materials.
  • the second positive active material further includes lithium cobaltate.
  • the positive electrode active material layer includes a third positive electrode active material
  • the third positive electrode active material includes lithium cobalt oxide, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium manganate, and manganese phosphate.
  • the positive active material layer further includes a conductive material.
  • the positive electrode conductive material may include any conductive material as long as it does not cause a chemical change.
  • Non-limiting examples of positive electrode conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., Including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (for example, polyphenylene derivatives), and mixtures thereof.
  • the positive electrode current collector may be aluminum (Al), but is not limited thereto.
  • the application also provides an electrochemical device, which includes a positive electrode, a negative electrode and an electrolyte.
  • the positive electrode used in the electrochemical device according to the present application has the structure and materials described above.
  • the negative electrode includes a current collector and a negative electrode active material layer provided on the current collector.
  • the specific types of negative electrode active materials are not subject to specific restrictions, and can be selected according to requirements.
  • the negative active material is selected from natural graphite, artificial graphite, mesophase micro-carbon spheres (MCMB for short), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li -Sn-O alloy, Sn, SnO, SnO 2 , spinel structure lithiated TiO 2 -Li 4 Ti 5 O 12 , one or more of Li-Al alloy.
  • MCMB mesophase micro-carbon spheres
  • Non-limiting examples of carbon materials include crystalline carbon, amorphous carbon, and mixtures thereof.
  • the crystalline carbon may be amorphous or flake-shaped, flake-shaped, spherical or fibrous natural graphite or artificial graphite.
  • Amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbide, calcined coke and the like.
  • the negative active material layer may include a binder, and optionally a conductive material.
  • binders include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-containing Oxygen polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylic (ester) styrene butadiene rubber, epoxy resin, Nylon etc.
  • the anode active material layer includes a conductive material, thereby imparting conductivity to the electrode.
  • the conductive material may include any conductive material as long as it does not cause a chemical change.
  • Non-limiting examples of conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., such as Copper, nickel, aluminum, silver, etc.), conductive polymers (for example, polyphenylene derivatives), and mixtures thereof.
  • the current collector used for the negative electrode described in the present application may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, polymer substrate coated with conductive metal, and combinations thereof.
  • the lithium salt that can be used in the electrolyte of the embodiment of the present application includes, but is not limited to: inorganic lithium salt, such as LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiSbF 6 , LiSO 3 F, LiN(FSO 2 ) 2, etc.
  • inorganic lithium salt such as LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiSbF 6 , LiSO 3 F, LiN(FSO 2 ) 2, etc.
  • Fluorine-containing organic lithium salts such as LiCF 3 SO 3 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , cyclic 1, 3 -Lithium hexafluoropropane disulfonimide, lithium cyclic 1,2-tetrafluoroethane disulfonimide, LiN(CF 3 SO 2 )(C 4 F 9 SO 2 ), LiC(CF 3 SO 2 ) 3 , LiPF 4 (CF 3 ) 2 , LiPF 4 (C 2 F 5 ) 2 , LiPF 4 (CF 3 SO 2 ) 2 , LiPF 4 (C 2 F 5 SO 2 ) 2 , LiBF 2 (CF 3 ) 2 , LiBF2(C2F5)2, LiBF 2 (CF 3 SO 2 ) 2 , LiBF 2 (C 2 F 5 SO 2 ) 2 ; Lithium salt containing dicarboxylic acid complex, such
  • the concentration of the lithium salt is in the range of 0.8 mol/L to 3 mol/L, in the range of 0.8 mol/L to 2.5 mol/L, in the range of about 0.8 mol/L to about 2 mol/L, or about In the range of 1 mol/L to about 2 mol/L. In some embodiments, the concentration of the lithium salt is about 1 mol/L, about 1.15 mol/L, about 1.2 mol/L, about 1.5 mol/L, about 2 mol/L, or about 2.5 mol/L.
  • Solvents that can be used in the electrolyte of the embodiments of this application include, but are not limited to: cyclic carbonate, chain carbonate, cyclic carboxylic acid ester, chain carboxylic acid ester, cyclic ether, chain ether, phosphorus-containing Organic solvents, sulfur-containing organic solvents and aromatic fluorine-containing solvents.
  • the cyclic carbonate includes, but is not limited to: ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate. In some embodiments, the cyclic carbonate has 3-6 carbon atoms.
  • the chain carbonate includes, but is not limited to: dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl n-propyl carbonate, ethyl n-propyl carbonate Carbonic acid esters, di-n-propyl carbonate and other chain carbonates, as chain carbonates substituted by fluorine, such as bis(fluoromethyl)carbonate, bis(difluoromethyl)carbonate, bis(trifluoromethyl) ) Carbonate, bis(2-fluoroethyl)carbonate, bis(2,2-difluoroethyl)carbonate, bis(2,2,2-trifluoroethyl)carbonate, 2-fluoroethyl Methyl carbonate, 2,2-difluoroethyl methyl carbonate and 2,2,2-trifluoroethyl methyl carbonate.
  • fluorine such as bis(fluoromethyl)carbonate, bis(difluoromethyl)carbonate,
  • cyclic carboxylic acid esters include, but are not limited to: ⁇ -butyrolactone and ⁇ -valerolactone.
  • part of the hydrogen atoms of the cyclic carboxylic acid ester may be substituted by fluorine.
  • the chain carboxylic acid esters include, but are not limited to: methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, tertiary acetate Butyl ester, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate , Methyl valerate, ethyl valerate, methyl pivalate and ethyl pivalate.
  • part of the hydrogen atoms of the chain carboxylic acid ester may be replaced by fluorine.
  • the fluorine-substituted chain carboxylic acid esters include, but are not limited to: methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and trifluoroacetic acid 2,2 , 2-Trifluoroethyl ester.
  • cyclic ethers include, but are not limited to: tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl 1,3-dioxolane, 4-methyl 1 , 3-Dioxolane, 1,3-dioxane, 1,4-dioxane and dimethoxypropane.
  • chain ethers include, but are not limited to: dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxymethane, 1 ,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxymethoxyethane and 1,2-ethoxymethane Oxyethane.
  • the phosphorus-containing organic solvent includes, but is not limited to: trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, ethylene methyl phosphate, ethylene phosphate Ethyl ester, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl) phosphate and tris(2,2, 3,3,3-pentafluoropropyl) ester.
  • sulfur-containing organic solvents include, but are not limited to: sulfolane, 2-methyl sulfolane, 3-methyl sulfolane, dimethyl sulfone, diethyl sulfone, ethyl methyl sulfone, methyl propyl sulfone Sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate, and dibutyl sulfate.
  • part of the hydrogen atoms of the sulfur-containing organic solvent may be replaced by fluorine.
  • the aromatic fluorine-containing solvent includes, but is not limited to: fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and trifluoromethylbenzene.
  • the solvent used in the electrolyte of the present application includes one or more of the above.
  • the solvent used in the electrolyte of the present application includes cyclic carbonate, chain carbonate, cyclic carboxylic acid ester, chain carboxylic acid ester, and combinations thereof.
  • the solvent used in the electrolyte of the present application includes an organic solvent selected from the group consisting of: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propionic acid Propyl ester, n-propyl acetate, ethyl acetate and combinations thereof.
  • the solvent used in the electrolyte of the present application includes: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, ⁇ -butyrolactone or a combination thereof .
  • the additives that can be used in the electrolyte of the embodiments of the present application include, but are not limited to: compounds with 2-3 cyano groups, cyclic carbonates containing carbon-carbon double bonds, compounds containing sulfur-oxygen double bonds, difluorophosphoric acid lithium.
  • compounds with 2-3 cyano groups may include succinonitrile (SN), adiponitrile (ADN), ethylene glycol bis(propionitrile) ether (EDN), 1, 3, 5-Pentyltricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile (HTCN), 1,2,6-hexanetricarbonitrile, 1,2,3-tris(2 -At least one of cyanoethoxy)propane (TCEP) or 1,2,4-tris(2-cyanoethoxy)butane.
  • SN succinonitrile
  • ADN adiponitrile
  • EDN ethylene glycol bis(propionitrile) ether
  • HTCN 1,3,6-hexanetricarbonitrile
  • TCEP 1,2,4-tris(2-cyanoethoxy)butane.
  • the cyclic carbonate having a carbon-carbon double bond specifically includes, but is not limited to: vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, vinyl ethylene ethylene carbonate, or At least one of carbonic acid-1,2-dimethyl vinylene ester.
  • compounds containing sulfur and oxygen double bonds include, but are not limited to: vinyl sulfate, 1,2-propanediol sulfate, 1,3-propane sultone, 1-fluoro-1,3-propanesulfon At least one of acid lactone, 2-fluoro-1,3-propane sultone or 3-fluoro-1,3-propane sultone.
  • a separator may be provided between the positive electrode and the negative electrode to prevent short circuits.
  • the material and shape of the isolation film that can be used in the embodiments of the present application are not particularly limited, and may be any technology disclosed in the prior art.
  • the isolation membrane includes a polymer or an inorganic substance formed of a material that is stable to the electrolyte of the present application.
  • the isolation film may include a substrate layer and a surface treatment layer.
  • the substrate layer is a non-woven fabric, film or composite film with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide.
  • a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be selected.
  • a surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic substance layer, or a layer formed by a mixed polymer and an inorganic substance.
  • the inorganic layer includes inorganic particles and binding materials.
  • the inorganic particles are selected from the group consisting of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, One or a combination of yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.
  • the binding material is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, One or a combination of polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
  • the polymer layer contains a polymer, and the material of the polymer is selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, poly At least one of (vinylidene fluoride-hexafluoropropylene).
  • the electrochemical device of the present application includes any device that undergoes an electrochemical reaction, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors.
  • the electrochemical device is a lithium secondary battery, a sodium secondary battery, a zinc secondary battery, and the like.
  • the lithium secondary battery may include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • the application also provides an electronic device, which includes the electrochemical device according to the application.
  • the use of the electrochemical device of the present application is not particularly limited, and it can be used in any electronic device known in the prior art.
  • the electrochemical device of the present application can be used in, but not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, and headsets.
  • Stereo headsets video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, power assistance Bicycles, bicycles, lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries, lithium-ion capacitors, etc.
  • lithium ion battery is taken as an example and the preparation of a lithium ion battery is described in conjunction with specific examples. Those skilled in the art will understand that the preparation methods described in this application are only examples, and any other suitable preparation methods are described in this application. Within range.
  • LiCoO 2 lithium cobaltate
  • SP acetylene black
  • PVDF polyvinylidene fluoride
  • NMP N-methylpyrrolidone
  • LiFePO 4 lithium iron phosphate
  • SP acetylene black and (SP) polyvinylidene fluoride
  • NMP N-methylpyrrolidone
  • the conductive agent, the first binder and the first positive electrode active material were mixed, N-methylpyrrolidone (NMP) was added, and the mixture was thoroughly stirred and mixed to obtain a conductive layer slurry, wherein the conductive layer
  • NMP N-methylpyrrolidone
  • the positive electrode active material layer slurry was coated on the conductive layer and dried at 85° C. to form the positive electrode active material layer. Then, after cutting and welding the tabs, the positive electrode is obtained.
  • LiPF 6 In a dry argon atmosphere, add LiPF 6 to a solvent mixed with propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) (weight ratio 1:1:1) and mix well , The concentration of LiPF 6 is 1.5 mol/L, and the electrolyte is obtained.
  • PC propylene carbonate
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • a 3 ⁇ m ceramic coating is coated on the surface of a 7 ⁇ m PE porous polymer film to obtain an isolation membrane.
  • the positive electrode, the separator and the negative electrode are stacked in order, wound, placed in an outer package, injected with electrolyte, and packaged. After vacuum packaging, standing, forming, shaping, capacity testing and other technological processes, the lithium ion battery is obtained.
  • High temperature storage internal resistance increase rate (R1-R0)/R0 ⁇ 100%.
  • Cycle resistance increase rate (Rb-Ra)/Ra ⁇ 100%.
  • Table 1 shows the effect of the conductive layer in the positive electrode on the performance of the lithium-ion battery. There is no conductive layer in the positive electrode used in Comparative Example 1. In Comparative Examples 2-5 and Examples 1-26, the thickness of the conductive layer was 2 ⁇ m.
  • Comparative Example 1 when there is no conductive layer in the positive electrode of the lithium ion battery, the high temperature storage internal resistance increase rate and the cycle internal resistance increase rate of the lithium ion battery are higher, and the performance is poor.
  • Comparative Example 2 when the positive electrode contains a conductive layer but the conductive layer contains a very high content of the first binder (up to 95wt%), the high-temperature storage internal resistance of the lithium ion battery has an extremely high rate of increase. The cycle internal resistance test When diving occurs, the performance of lithium-ion batteries is extremely poor.
  • Comparative Examples 3 and 4 when the conductive agent in the conductive layer of the positive electrode increases but the content is small (less than 20wt%), the high temperature storage internal resistance increase rate and cycle internal resistance increase rate of the lithium ion battery decrease, but Still high, the performance of lithium-ion batteries is poor. As shown in Comparative Example 5, when the content of the conductive agent in the conductive layer of the positive electrode increases to more than 95 wt%, the high temperature storage internal resistance increase rate and the cycle internal resistance increase rate of the lithium ion battery are high, and the performance is poor.
  • Table 2 shows the influence of the thickness of the conductive layer in the positive electrode on the performance of the lithium ion battery. Except that the thickness of the conductive layer is different, the other settings of Embodiments 27-33 are the same as those of Embodiment 5.
  • the results show that when the thickness of the conductive layer is in the range of 0.01 ⁇ m to 10 ⁇ m, the high-temperature storage internal resistance increase rate, high-temperature storage capacity recovery loss rate and cycle internal resistance increase rate of the lithium-ion battery can be further reduced.
  • references to “embodiments”, “partial examples”, “one embodiment”, “another example”, “examples”, “specific examples” or “partial examples” throughout the specification mean that At least one embodiment or example in this application includes the specific feature, structure, material, or characteristic described in the embodiment or example. Therefore, descriptions appearing in various places throughout the specification, such as: “in some embodiments”, “in embodiments”, “in one embodiment”, “in another example”, “in an example “In”, “in a specific example” or “exemplified”, which are not necessarily quoting the same embodiment or example in this application.
  • the specific features, structures, materials, or characteristics herein can be combined in one or more embodiments or examples in any suitable manner.

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Abstract

本申请涉及一种正极及使用其的电化学装置和电子装置。具体而言，本申请提供一种正极，其包括正极集流体、正极活性物质层、粘合层和导电层，所述粘合层设置在所述正极集流体和所述正极活性物质层之间，所述导电层设置在所述粘合层和所述正极活性物质层之间，其中所述导电层包含20wt％至95wt％的导电剂和5wt％至80wt％粘结剂。本申请的正极有助于改善电化学装置的循环性能和高温存储性能。

Description

正极及使用其的电化学装置和电子装置 技术领域
本申请涉及储能领域，具体涉及一种正极及使用其的电化学装置和电子装置。
背景技术
电化学装置(例如，锂离子电池)由于具有高能量密度、长循环寿命及无记忆效应等优点而被广泛应用于穿戴设备、智能手机、无人机、电动汽车及大型储能等设备等领域，已成为当今世界最具发展潜力的新型绿色化学电源。如何提升锂离子电池的安全性能和循环存储性能已成为亟待解决的技术问题。改善极片是解决上述问题的手段之一。
有鉴于此，确有必要提供一种改进的正极及使用其的电化学装置和电子装置。
发明内容
本申请通过提供一种具有正极及使用其的电化学装置和电子装置以试图在至少某种程度上解决至少一种存在于相关领域中的问题。
根据本申请的一个方面，本申请提供了一种正极，其包括正极集流体、正极活性物质层、粘合层和导电层，所述粘合层设置在所述正极集流体和所述正极活性物质层之间，所述导电层设置在所述粘合层和所述正极活性物质层之间，其中所述导电层包括导电剂和第一粘结剂，并且基于所述导电层的总重量，所述导电剂的含量为20wt％至95wt％，所述第一粘结剂的含量为5wt％至80wt％。
根据本申请的实施例，所述导电层进一步包括第一正极活性物质，且基于所述导电层的总重量，所述第一正极活性物质的含量不大于75wt％。
根据本申请的实施例，所述导电层的厚度为0.01μm至10μm。
根据本申请的实施例，所述粘合层包括第二粘结剂，所述正极活性物质层包括第三粘结剂，所述粘合层中的所述第二粘结剂的含量大于所述正极活性物质层中的所述第三粘结剂的含量。
根据本申请的实施例，所述粘合层还包括第二正极活性物质，所述第二正极活性物质选自镍钴锰酸锂、镍钴铝酸锂、锰酸锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、磷酸铁锂、钛酸锂和富锂锰基材料中的至少一种。
根据本申请的实施例，所述正极活性物质层、所述粘合层和所述导电层设置在所述正极集流体的一侧。
根据本申请的实施例，所述正极集流体的两侧均设置有所述正极活性物质层、所述粘合层和所述导电层。
根据本申请的实施例，所述导电剂选自炭黑、乙炔黑、碳纳米管、导电石墨和石墨烯中的至少一种。
根据本申请的实施例，所述第一粘结剂选自聚偏二氟乙烯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚胺酯、氟化橡胶和聚乙烯醇中的至少一种。
根据本申请的实施例，所述第一正极活性物质选自钴酸锂、镍钴锰酸锂、磷酸铁锂和锰酸锂中的至少一种。
根据本申请的另一个方面，本申请提供了一种电化学装置，其包括根据本申请所述的正极、负极和电解液。
根据本申请的又一个方面，本申请提供了一种电子装置，其包括根据本申请所述的电化学装置。
本申请的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
附图说明
在下文中将简要地说明为了描述本申请实施例或现有技术所必要的附图以便于描述本申请的实施例。显而易见地，下文描述中的附图仅只是本申请中的部分实施例。对本领域技术人员而言，在不需要创造性劳动的前提下，依然可以根据这些附图中所例示的结构来获得其他实施例的附图。
图1展示了根据本申请实施例的一正极的结构示意图。
图2展示了根据本申请实施例的另一正极的结构示意图。
附图标记如下：
1：正极集流体
2：正极活性物质层
3：粘合层3
4：导电层4
具体实施方式
本申请的实施例将会被详细的描示在下文中。本申请的实施例不应该被解释为对本 申请的限制。
在具体实施方式及权利要求书中，由术语“中的至少一种”连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一种”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一种”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
随着电化学装置(例如，锂离子电池)的广泛应用，其存储性能和循环性能备受关注。为了同时改善电化学装置的循环性能和高温存储性能，本申请提供了一种正极，其包括正极集流体、正极活性物质层、粘合层和导电层，所述粘合层设置在所述正极集流体和所述正极活性物质层之间，所述导电层设置在所述粘合层和所述正极活性物质层之间，其中所述导电层包括导电剂和第一粘结剂，并且基于所述导电层的总重量，所述导电剂的含量为20wt％至95wt％，所述第一粘结剂的含量为5wt％至80wt％。图1展示了根据本申请实施例的一正极的结构示意图，其中正极包括正极集流体1、正极活性物质层2、粘合层3和导电层4。在一些实施例中，基于所述导电层的总重量，所述导电剂的含量为30wt％至90wt％。在一些实施例中，基于所述导电层的总重量，所述导电剂的含量为30wt％至80wt％。在一些实施例中，基于所述导电层的总重量，所述导电剂的含量为40wt％至70wt％。在一些实施例中，基于所述导电层的总重量，所述导电剂的含量为50wt％至60wt％。在一些实施例中，基于所述导电层的总重量，所述导电剂的含量为20wt％、25wt％、30wt％、35wt％、40wt％、45wt％、50wt％、55wt％、60wt％、65wt％、70wt％、75wt％、80wt％、85wt％、90wt％、95wt％或在上述任意两个数值所组成的范围内。
在一些实施例中，基于所述导电层的总重量，所述第一粘结剂的含量为10wt％至70wt％。在一些实施例中，基于所述导电层的总重量，所述第一粘结剂的含量为20wt％至60wt％。在一些实施例中，基于所述导电层的总重量，所述第一粘结剂的含量为30wt％至50wt％。在一些实施例中，基于所述导电层的总重量，所述第一粘结剂的含量为5wt％、10wt％、15wt％、20wt％、25wt％、30wt％、35wt％、40wt％、45wt％、50wt％、55wt％、60wt％、65wt％、70wt％、75wt％、80wt％或在上述任意两个数值所组成的范围内。
导电剂可为导电层提供导电性，其具有连接导电层两侧界面的作用，有助于改善界 面电阻。第一粘结剂的存在可使导电层与正极集流体相粘结。当导电层中第一粘结剂的含量较高(即，导电剂的含量较低)时，导电层的粘结性增加，但导电性下降，当电化学装置在循环过程中发生膨胀时，有可能导致导电剂之间的连接断开，导电层的功能随之消失。当导电层中第一粘结剂含量和导电剂含量在上述范围时，导电层中具有足够的导电位点，可避免电化学装置的循环过程中由膨胀导致的导电剂无法连接的问题，从而可显著降低电化学装置的循环性能和高温存储性能。
根据本申请的实施例，所述导电层进一步包括第一正极活性物质，且基于所述导电层的总重量，所述第一正极活性物质的含量不大于75wt％。在一些实施例中，基于所述导电层的总重量，所述第一正极活性物质的含量不大于70wt％。在一些实施例中，基于所述导电层的总重量，所述第一正极活性物质的含量不大于60wt％。在一些实施例中，基于所述导电层的总重量，所述第一正极活性物质的含量不大于50wt％。在一些实施例中，基于所述导电层的总重量，所述第一正极活性物质的含量不大于30wt％。在一些实施例中，基于所述导电层的总重量，所述第一正极活性物质的含量不大于20wt％。在一些实施例中，基于所述导电层的总重量，所述第一正极活性物质的含量不大于10wt％。在一些实施例中，基于所述导电层的总重量，所述第一正极活性物质的含量为5wt％、10wt％、15wt％、20wt％、25wt％、30wt％、35wt％、40wt％、45wt％、50wt％、55wt％、60wt％、65wt％、70wt％、75wt％或在上述任意两个数值所组成的范围内。当导电层中包含具有上述含量的第一正极活性物质时，可以进一步改善电化学装置的循环性能和高温存储性能。
根据本申请的实施例，所述导电层的厚度为0.01μm至10μm。在一些实施例中，所述导电层的厚度为0.05μm至8μm。在一些实施例中，所述导电层的厚度为0.1μm至6μm。在一些实施例中，所述导电层的厚度为0.5μm至5μm。在一些实施例中，所述导电层的厚度为1μm至3μm。在一些实施例中，所述导电层的厚度为0.01μm、0.05μm、0.1μm、0.5μm、1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm、10μm或在上述任意两个数值所组成的范围内。当导电层的厚度在上述范围内时，可以进一步改善电化学装置的循环性能和高温存储性能。
根据本申请的实施例，所述正极活性物质层、所述粘合层和所述导电层设置在所述正极集流体的一侧。如图1所示，正极活性物质层2、粘合层3和导电层4仅设置在正极集流体1的一侧。
根据本申请的实施例，所述正极集流体的两侧均设置有所述正极活性物质层、所述 粘合层和所述导电层，如图2所示，正极集流体1的两侧均设置有正极活性物质层2、粘合层3和导电层4。
根据本申请的实施例，所述导电剂选自炭黑、乙炔黑、碳纳米管、导电石墨和石墨烯中的至少一种。
根据本申请的实施例，所述第一粘结剂选自聚偏二氟乙烯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚胺酯、氟化橡胶和聚乙烯醇中的至少一种。
根据本申请的实施例，所述第一正极活性物质选自钴酸锂、镍钴锰酸锂、磷酸铁锂和锰酸锂中的至少一种。
根据本申请的实施例，所述粘合层包括第二粘结剂，所述正极活性物质层包括第三粘结剂，所述粘合层中的所述第二粘结剂的含量大于所述正极活性物质层中的所述第三粘结剂的含量。粘合层中的高粘结剂含量有助于提升粘合层的粘合性，可保证粘合层与正极集流体(铝基材)之间具有较强的粘结力，从而可避免电化学装置在受到外力作用时粘合层脱离正极集流体，使得正极集流体不会与负极活性物质层直接接触，从而降低短路风险。同时粘合层中的第二活性物质在高电压时具有合适的内阻，可减小电化学装置受外力作用发生短路时的瞬时放电电流。由此，可改善电化学装置的安全性。正极活性物质层具有较低含量的粘结剂，其可保证正极整体的压实密度和正极活性物质的正极活性物质含量，从而保证电化学装置的能量密度。
根据本申请的实施例，所述粘合层中的所述第二粘结剂的含量与所述正极活性物质层中的所述第三粘结剂的含量比值在1.1至4的范围内。在一些实施例中，所述粘合层中的所述第二粘结剂的含量与所述正极活性物质层中的所述第三粘结剂的含量比值在1.5至3的范围内。在一些实施例中，所述粘合层中的所述第二粘结剂的含量与所述正极活性物质层中的所述第三粘结剂的含量比值在2至2.5的范围内。在一些实施例中，所述粘合层中的所述第二粘结剂的含量与所述正极活性物质层中的所述第三粘结剂的含量比值为1.1、1.5、1.8、2、2.2、2.5、2.8、3、3.2、3.5、3.8、4或在上述任意两个数值所组成的范围内。当粘合层中的第二粘结剂的含量与正极活性物质层中的第三粘结剂的含量比值在上述范围内时，粘合层可有效地保护正极集流体，正极活性物质层可以保持高能量密度，有助于提高电化学装置的安全性同时保持高能量密度。
根据本申请的实施例，基于所述正极的总重量，所述正极活性物质层中的所述第三粘结剂的含量为0.1wt％至5wt％。在一些实施例中，基于所述正极的总重量，所述正极活性物质层中的所述第三粘结剂的含量为0.5wt％至4wt％。在一些实施例中，基于 所述正极的总重量，所述正极活性物质层中的所述第三粘结剂的含量为1wt％至3wt％。在一些实施例中，基于所述正极的总重量，所述正极活性物质层中的所述第三粘结剂的含量为2wt％至2.5wt％。在一些实施例中，基于所述正极的总重量，所述正极活性物质层中的所述第三粘结剂的含量为0.1wt％、0.5wt％、1wt％、1.5wt％、2wt％、2.5wt％、3wt％、3.5wt％、4wt％、4.5wt％、5wt％或在上述任意两个数值所组成的范围内。
根据本申请的实施例，基于所述正极的总重量，所述粘合层中的所述第二粘结剂的含量为0.11wt％至20wt％。在一些实施例中，基于所述正极的总重量，所述粘合层中的所述第二粘结剂的含量为0.2wt％至18wt％。在一些实施例中，基于所述正极的总重量，所述粘合层中的所述第二粘结剂的含量为0.5wt％至15wt％。在一些实施例中，基于所述正极的总重量，所述粘合层中的所述第二粘结剂的含量为1wt％至10wt％。在一些实施例中，基于所述正极的总重量，所述粘合层中的所述第二粘结剂的含量为3wt％至5wt％。在一些实施例中，基于所述正极的总重量，所述粘合层中的所述第二粘结剂的含量为0.11wt％、0.3wt％、0.5wt％、1wt％、3wt％、5wt％、8wt％、10wt％、12wt％、15wt％、18wt％、20wt％或在上述任意两个数值所组成的范围内。
根据本申请的实施例，所述粘合层的厚度为0.01μm至15μm。在一些实施例中，所述粘合层的厚度为0.05μm至10μm。在一些实施例中，所述粘合层的厚度为0.1μm至8μm。在一些实施例中，所述粘合层的厚度为0.5μm至5μm。在一些实施例中，所述粘合层的厚度为1μm至3μm。在一些实施例中，所述粘合层的厚度为1μm至2μm。在一些实施例中，所述粘合层的厚度为0.01μm、0.05μm、0.1μm、0.5μm、1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm、10μm、11μm、12μm、13μm、14μm、15μm或在上述任意两个数值所组成的范围内。
根据本申请的实施例，所述第二粘结剂包括聚偏二氟乙烯、偏氟乙烯-氟化烯烃的共聚物、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚胺酯、氟化橡胶或聚乙烯醇中的至少一种。
根据本申请的实施例，所述第三粘结剂与所述第二粘结剂相同或不同。
根据本申请的实施例，所述粘合层还包括第二正极活性物质，所述第二正极活性物质选自镍钴锰酸锂、镍钴铝酸锂、锰酸锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、磷酸铁锂、钛酸锂和富锂锰基材料中的至少一种。在一些实施例中，所述第二正极活性物质还包含钴酸锂。
根据本申请的实施例，所述正极活性物质层包括第三正极活性物质，所述第三正极 活性物质包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、锰酸锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、磷酸铁锂、钛酸锂或富锂锰基材料中的至少一种。
根据本申请的实施例，所述正极活性物质层还包含导电材料。所述正极导电材料可以包括任何导电材料，只要它不引起化学变化。正极导电材料的非限制性示例包括基于碳的材料(例如，天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维等)、基于金属的材料(例如，金属粉、金属纤维等，包括例如铜、镍、铝、银等)、导电聚合物(例如，聚亚苯基衍生物)和它们的混合物。根据本申请的实施例，正极集流体可以是铝(Al)，但不限于此。
本申请还提供了一种电化学装置，其包括正极、负极和电解液。
正极
用于根据本申请的电化学装置的正极具有以上所述的结构和材料。
负极
负极包括集流体和设置在集流体上的负极活性材料层。负极活性材料的具体种类均不受到具体的限制，可根据需求进行选择。
在一些实施例中，所述负极活性材料选自天然石墨、人造石墨、中间相微碳球(简称为MCMB)、硬碳、软碳、硅、硅-碳复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化TiO 2-Li 4Ti 5O 12、Li-Al合金中的一种或几种。
碳材料的非限制性示例包括结晶碳、非晶碳和它们的混合物。结晶碳可以是无定形的或片形的、小片形的、球形的或纤维状的天然石墨或人造石墨。非晶碳可以是软碳、硬碳、中间相沥青碳化物、煅烧焦等。
在一些实施例中，负极活性材料层可以包含粘合剂，并且可选地还包括导电材料。
粘合剂提高负极活性材料颗粒彼此间的结合和负极活性材料与集流体的结合。粘合剂的非限制性示例包括聚乙烯醇、羧甲基纤维素、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1，1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂、尼龙等。
负极活性材料层包括导电材料，从而赋予电极导电性。所述导电材料可以包括任何导电材料，只要它不引起化学变化。导电材料的非限制性示例包括基于碳的材料(例如，天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维等)、基于金属的材料(例如，金属粉、金属纤维等，例如铜、镍、铝、银等)、导电聚合物(例如，聚亚苯基衍生物)和它 们的混合物。
用于本申请所述的负极的集流体可以选自铜箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜、覆有导电金属的聚合物基底和它们的组合。
电解液
可用于本申请实施例的电解液中的锂盐包括、但不限于：无机锂盐，例如LiClO 4、LiAsF 6、LiPF 6、LiBF 4、LiSbF 6、LiSO 3F、LiN(FSO 2) 2等；含氟有机锂盐，例如LiCF 3SO 3、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1，3-六氟丙烷二磺酰亚胺锂、环状1，2-四氟乙烷二磺酰亚胺锂、LiN(CF 3SO 2)(C 4F 9SO 2)、LiC(CF 3SO 2) 3、LiPF 4(CF 3) 2、LiPF 4(C 2F 5) 2、LiPF 4(CF 3SO 2) 2、LiPF 4(C 2F 5SO 2) 2、LiBF 2(CF 3) 2、LiBF2(C2F5)2、LiBF 2(CF 3SO 2) 2、LiBF 2(C 2F 5SO 2) 2；含二羧酸配合物锂盐，例如双(草酸根合)硼酸锂、二氟草酸根合硼酸锂、三(草酸根合)磷酸锂、二氟双(草酸根合)磷酸锂、四氟(草酸根合)磷酸锂等。另外，上述锂盐可以单独使用一种，也可以同时使用两种或两种以上。在一些实施例中，锂盐包括LiPF 6和LiBF 4的组合。在一些实施例中，锂盐包括LiPF 6或LiBF 4等无机锂盐与LiCF 3SO 3、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2等含氟有机锂盐的组合。在一些实施例中，锂盐的浓度在0.8mol/L至3mol/L的范围内，0.8mol/L至2.5mol/L的范围内、约0.8mol/L至约2mol/L的范围或约1mol/L至约2mol/L的范围内。在一些实施例中，锂盐的浓度为约1mol/L、约1.15mol/L、约1.2mol/L、约1.5mol/L、约2mol/L或约2.5mol/L。
可用于本申请实施例的电解液中的溶剂包括、但不限于：环状碳酸酯、链状碳酸酯、环状羧酸酯、链状羧酸酯、环状醚、链状醚、含磷有机溶剂、含硫有机溶剂和芳香族含氟溶剂。
在一些实施例中，环状碳酸酯包括，但不限于：碳酸亚乙酯(ethylene carbonate，EC)、碳酸亚丙酯(propylene carbonate，PC)和碳酸亚丁酯。在一些实施例中，环状碳酸酯具有3-6个碳原子。
在一些实施例中，链状碳酸酯包括，但不限于：碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯(diethyl carbonate，DEC)、碳酸甲基正丙基酯、碳酸乙基正丙基酯、碳酸二正丙酯等链状碳酸酯，作为被氟取代的链状碳酸酯，例如双(氟甲基)碳酸酯、双(二氟甲基)碳酸酯、双(三氟甲基)碳酸酯、双(2-氟乙基)碳酸酯、双(2，2-二氟乙基)碳酸酯、双(2，2，2-三氟乙基)碳酸酯、2-氟乙基甲基碳酸酯、2，2-二氟乙基甲基碳酸酯和2，2，2-三氟乙基甲基碳酸酯。
在一些实施例中，环状羧酸酯包括，但不限于：γ-丁内酯和γ-戊内酯。在一些实施例中，环状羧酸酯的部分氢原子可被氟取代。
在一些实施例中，链状羧酸酯包括，但不限于：乙酸甲酯、乙酸乙酯、乙酸丙酯、乙酸异丙酯、乙酸丁酯、乙酸仲丁酯、乙酸异丁酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丙酸异丙酯、丁酸甲酯、丁酸乙酯、丁酸丙酯、异丁酸甲酯、异丁酸乙酯、戊酸甲酯、戊酸乙酯、特戊酸甲酯和特戊酸乙酯。在一些实施例中，链状羧酸酯的部分氢原子可被氟取代。在一些实施例中，氟取代的链状羧酸酯包括，但不限于：三氟乙酸甲酯、三氟乙酸乙酯、三氟乙酸丙酯、三氟乙酸丁酯和三氟乙酸2，2，2-三氟乙酯。
在一些实施例中，环状醚包括，但不限于：四氢呋喃、2-甲基四氢呋喃、1，3-二氧戊环、2-甲基1，3-二氧戊环、4-甲基1，3-二氧戊环、1，3-二氧六环、1，4-二氧六环和二甲氧基丙烷。
在一些实施例中，链状醚包括，但不限于：二甲氧基甲烷、1，1-二甲氧基乙烷、1，2-二甲氧基乙烷、二乙氧基甲烷、1，1-二乙氧基乙烷、1，2-二乙氧基乙烷、乙氧基甲氧基甲烷、1，1-乙氧基甲氧基乙烷和1，2-乙氧基甲氧基乙烷。
在一些实施例中，含磷有机溶剂包括，但不限于：磷酸三甲酯、磷酸三乙酯、磷酸二甲基乙酯、磷酸甲基二乙酯、磷酸亚乙基甲酯、磷酸亚乙基乙酯、磷酸三苯酯、亚磷酸三甲酯、亚磷酸三乙酯、亚磷酸三苯酯、磷酸三(2，2，2-三氟乙基)酯和磷酸三(2，2，3，3，3-五氟丙基)酯。
在一些实施例中，含硫有机溶剂包括，但不限于：环丁砜、2-甲基环丁砜、3-甲基环丁砜、二甲基砜、二乙基砜、乙基甲基砜、甲基丙基砜、二甲基亚砜、甲磺酸甲酯、甲磺酸乙酯、乙磺酸甲酯、乙磺酸乙酯、硫酸二甲酯、硫酸二乙酯和硫酸二丁酯。在一些实施例中，含硫有机溶剂的部分氢原子可被氟取代。
在一些实施例中，芳香族含氟溶剂包括，但不限于：氟苯、二氟苯、三氟苯、四氟苯、五氟苯、六氟苯和三氟甲基苯。
在一些实施例中，本申请的电解液中使用的溶剂包括如上所述的一种或多种。在一些实施例中，本申请的电解液中使用的溶剂包括环状碳酸酯、链状碳酸酯、环状羧酸酯、链状羧酸酯及其组合。在一些实施例中，本申请的电解液中使用的溶剂包含选自由下列物质组成的群组的有机溶剂：碳酸亚乙酯、碳酸亚丙酯、碳酸二乙酯、丙酸乙酯、丙酸丙酯、乙酸正丙酯、乙酸乙酯及其组合。在一些实施例中，本申请的电解 液中使用的溶剂包含：碳酸亚乙酯、碳酸亚丙酯、碳酸二乙酯、丙酸乙酯、丙酸丙酯、γ-丁内酯或其组合。
可用于本申请实施例的电解液中的添加剂包括、但不限于：具有2-3个氰基的化合物、含碳碳双键的环状碳酸酯、含硫氧双键的化合物、二氟磷酸锂。
在一些实施例中具有2-3个氰基的化合物，可以包括选自丁二腈(SN)、己二腈(ADN)、乙二醇双(丙腈)醚(EDN)、1，3，5-戊三甲腈、1，2，3-丙三甲腈、1，3，6-己烷三甲腈(HTCN)、1，2，6-己烷三甲腈、1，2，3-三(2-氰基乙氧基)丙烷(TCEP)或1，2，4-三(2-氰基乙氧基)丁烷中的至少一种。
在一些实施例中具有碳-碳双键的环状碳酸酯具体包括，但不限于：碳酸亚乙烯酯、碳酸甲基亚乙烯酯、碳酸乙基亚乙烯酯、乙烯基碳酸乙烯亚乙酯或碳酸-1，2-二甲基亚乙烯酯中的至少一种。
在一些实施例中含硫氧双键的化合物包括，但不限于：硫酸乙烯酯、1，2-丙二醇硫酸酯、1，3-丙磺酸内酯、1-氟-1，3-丙磺酸内酯、2-氟-1，3-丙磺酸内酯或3-氟-1，3-丙磺酸内酯中的至少一种。
隔离膜
在一些实施例中，正极与负极之间可设有隔离膜以防止短路。可用于本申请的实施例中使用的隔离膜的材料和形状没有特别限制，其可为任何现有技术中公开的技术。在一些实施例中，隔离膜包括由对本申请的电解液稳定的材料形成的聚合物或无机物等。
例如，隔离膜可包括基材层和表面处理层。基材层为具有多孔结构的无纺布、膜或复合膜，基材层的材料选自聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯和聚酰亚胺中的至少一种。具体的，可选用聚丙烯多孔膜、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。
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。
无机物层包括无机颗粒和粘结材料，无机颗粒选自氧化铝、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、氢氧化钙和硫酸钡中的一种或几种的组合。粘结材料选自聚偏氟乙烯、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，聚合物的材料选自聚酰胺、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、聚(偏氟乙烯-六氟丙烯)中的至少一种。
电化学装置
本申请的电化学装置包括发生电化学反应的任何装置，它的具体实例包括所有种类的一次电池、二次电池、燃料电池、太阳能电池或电容器。特别地，该电化学装置是锂二次电池、钠二次电池和锌二次电池等。锂二次电池可包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
电子装置
本申请另提供了一种电子装置，其包括根据本申请的电化学装置。本申请的电化学装置的用途没有特别限定，其可用于现有技术中已知的任何电子装置。在一些实施例中，本申请的电化学装置可用于，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。
下面以锂离子电池为例并且结合具体的实施例说明锂离子电池的制备，本领域的技术人员将理解，本申请中描述的制备方法仅是实例，其他任何合适的制备方法均在本申请的范围内。
实施例
以下说明根据本申请的锂离子电池的实施例和对比例进行性能评估。
一、锂离子电池的制备
1、正极的制备
将钴酸锂(LiCoO 2)、乙炔黑(SP)和聚偏二氟乙烯(PVDF)按照重量比为96.5∶2∶1.5溶于N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀，得到正极活性物质层浆料，其中正极活性物质层浆料的固含量为72wt％。
将磷酸铁锂(LiFePO 4)、乙炔黑和(SP)聚偏二氟乙烯(PVDF)按照重量比93∶2∶5溶于N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀，得到粘合层浆料，其中粘合层浆料的固含量为70wt％。
根据以下实施例和对比例的设置将导电剂、第一粘结剂和第一正极活性物质混合，加入N-甲基吡咯烷酮(NMP)，充分搅拌混合均匀，得到导电层浆料，其中导电层浆料的固含量为10wt％。
在正极集流体铝箔上涂覆粘合层浆料，在85℃下烘干，形成粘合层。在粘合层上涂覆导电层浆料，在85℃下烘干，形成导电层。然后在导电层上涂覆正极活性物质层浆料，在85℃下烘干，形成正极活性物质层。然后经过裁片、焊接极耳，得到正极。
2、负极的制备
将石墨、Super P、羧甲基纤维素钠(CMC)和丁苯橡胶(SBR)按照重量比96.4∶1.5∶0.5∶1.6在适量的去离子水溶剂中充分搅拌混合，使其形成均匀的负极浆料，其中负极浆料的固含量为54wt％。将该负极浆料涂覆于负极集流体铜箔上并在85℃下烘干，然后进行切边、裁片、分条、烘干，得到负极活性材料层，再经过裁片、焊接极耳，得到负极。
3、电解液的制备
在干燥氩气环境下，在碳酸丙烯酯(PC)，碳酸乙烯酯(EC)，碳酸二乙酯(DEC)(重量比1∶1∶1)混合而成的溶剂中，加入LiPF 6混合均匀，其中LiPF 6的浓度为1.5mol/L，得到电解液。
4、隔离膜的制备
在7μm的PE多孔聚合物薄膜表面涂覆3μm的陶瓷涂层，得到隔离膜。
5、锂离子电池的制备
将正极、隔离膜和负极按顺序叠好，卷绕，置于外包装中，注入电解液，封装。经过真空封装、静置、化成、整形、容量测试等工艺流程得到锂离子电池。
二、测试方法
1、锂离子电池的高温存储内阻增加率的测试方法
将锂离子电池以0.5C恒流充电至4.4V，以4.4V恒压放电至0.025C，使锂离子电池达到满充状态，测试锂离子电池的交流内阻R0。在85℃下存储8小时，测试锂离子电池的交流内阻R1。通过下式计算锂离子电池的高温存储内阻增加率：
高温存储内阻增加率＝(R1-R0)/R0×100％。
2、锂离子电池的循环内阻增加率的测试方法
将锂离子电池置于45℃恒温箱中，以0.7C恒流充电至4.4V，以4.4V恒压放电至0.025C，使锂离子电池达到满充状态，测试锂离子电池的交流内阻Ra。然后以1.0C直 流充电至3.0V，静置5分钟，以0.7C恒流充电至4.4V，以4.4V恒压放电至0.025C，静置5分钟，重复该循环过程400次，测试锂离子电池的交流内阻Rb。通过下式计算锂离子电池的循环内阻增加率：
循环内阻增加率＝(Rb-Ra)/Ra×100％。
三、测试结果
表1展示了正极中导电层对锂离子电池的性能的影响。对比例1使用的正极中不存在导电层。在对比例2-5和实施例1-26中，导电层的厚度为2μm。
如对比例1所示，当锂离子电池的正极中没有导电层时，锂离子电池的高温存储内阻增加率和循环内阻增加率较高，性能较差。如对比例2所示，当正极包含导电层但导电层包含极高含量的第一粘结剂含(高达95wt％)时，锂离子电池的高温存储内阻增加率极高，循环内阻测试时发生跳水，锂离子电池的性能极差。如对比例3和4所示，正极的导电层中的导电剂增加但含量较小(小于20wt％)时，锂离子电池的高温存储内阻增加率和循环内阻增加率有所下降，但依然较高，锂离子电池的性能较差。如对比例5所示，当正极的导电层中的导电剂含量增大至超过95wt％时，锂离子电池的高温存储内阻增加率和循环内阻增加率较高，性能较差。
如实施例1-26所示，当锂离子电池的正极中存在导电层并且导电层包含20wt％至95wt％的导电剂和5wt％至80wt％的第一粘结剂时，锂离子电池的高温存储内阻增加率和循环内阻增加率显著降低，锂离子电池具有显著改善的循环性能和高温存储性能。在正极的导电层中的导电剂含量一定的情况下，在导电层中添加不大于75wt％的第一正极活性物质可进一步降低锂离子电池的高温存储内阻增加率和循环内阻增加率。结果还表明，不同类型的导电剂、第一粘结剂和第一正极活性物质可实现基本相当的效果，即，均可以显著降低锂离子电池的高温存储内阻增加率和循环内阻增加率。
Figure PCTCN2020092382-appb-000001
Figure PCTCN2020092382-appb-000002
表2展示了正极中导电层的厚度对锂离子电池的性能的影响。除导电层厚度不同以外，实施例27-33与实施例5的其它设置相同。
表2
Figure PCTCN2020092382-appb-000003
结果表明，当导电层的厚度在0.01μm至10μm范围内时，可进一步降低锂离子电池的高温存储内阻增加率、高温存储容量恢复损失率和循环内阻增加率。
整个说明书中对“实施例”、“部分实施例”、“一个实施例”、“另一举例”、“举例”、“具体举例”或“部分举例”的引用，其所代表的意思是在本申请中的至少一个实施例或举例包含了该实施例或举例中所描述的特定特征、结构、材料或特性。因此，在整个说明书中的各处所出现的描述，例如：“在一些实施例中”、“在实施例中”、“在一个实施例中”、“在另一个举例中”，“在一个举例中”、“在特定举例中”或“举例”，其不必然是引用本申请中的相同的实施例或示例。此外，本文中的特定特征、结构、材料或特性可以以任何合适的方式在一个或多个实施例或举例中结合。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。

Claims (11)

  1. 一种正极，其包括正极集流体、正极活性物质层、粘合层和导电层，所述粘合层设置在所述正极集流体和所述正极活性物质层之间，所述导电层设置在所述粘合层和所述正极活性物质层之间，其中所述导电层包括导电剂和第一粘结剂，并且基于所述导电层的总重量，所述导电剂的含量为20wt％至95wt％，所述第一粘结剂的含量为5wt％至80wt％。
  2. 根据权利要求1所述的正极，其中所述导电层进一步包括第一正极活性物质，且基于所述导电层的总重量，所述第一正极活性物质的含量不大于75wt％。
  3. 根据权利要求1所述的正极，其中所述导电层的厚度为0.01μm至10μm。
  4. 根据权利要求1所述的正极，其中所述粘合层包括第二粘结剂，所述正极活性物质层包括第三粘结剂，所述粘合层中的所述第二粘结剂的含量大于所述正极活性物质层中的所述第三粘结剂的含量。
  5. 根据权利要求1所述的正极，其中所述粘合层还包括第二正极活性物质，所述第二正极活性物质选自镍钴锰酸锂、镍钴铝酸锂、锰酸锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、磷酸铁锂、钛酸锂和富锂锰基材料中的至少一种。
  6. 根据权利要求1所述的正极，其中：
    所述正极活性物质层、所述粘合层和所述导电层设置在所述正极集流体的一侧；或者
    所述正极集流体的两侧均设置有所述正极活性物质层、所述粘合层和所述导电层。
  7. 根据权利要求1所述的正极，其中所述导电剂选自炭黑、乙炔黑、碳纳米管、导电石墨和石墨烯中的至少一种。
  8. 根据权利要求1所述的正极，其中所述第一粘结剂选自聚偏二氟乙烯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚胺酯、氟化橡胶和聚乙烯醇中的至少一种。
  9. 根据权利要求2所述的正极，其中所述第一正极活性物质选自钴酸锂、镍钴锰酸锂、磷酸铁锂和锰酸锂中的至少一种。
  10. 一种电化学装置，其包括根据权利要求1-9中任一权利要求所述的正极。
  11. 一种电子装置，其包括根据权利要求10所述的电化学装置。
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