WO2022188136A1 - 电化学装置和电子装置 - Google Patents

电化学装置和电子装置 Download PDF

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Publication number
WO2022188136A1
WO2022188136A1 PCT/CN2021/080416 CN2021080416W WO2022188136A1 WO 2022188136 A1 WO2022188136 A1 WO 2022188136A1 CN 2021080416 W CN2021080416 W CN 2021080416W WO 2022188136 A1 WO2022188136 A1 WO 2022188136A1
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Prior art keywords
active material
positive electrode
electrode active
material layer
electrochemical device
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PCT/CN2021/080416
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English (en)
French (fr)
Inventor
李娅洁
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宁德新能源科技有限公司
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Priority to CN202180003374.7A priority Critical patent/CN113853699B/zh
Priority to EP21929612.6A priority patent/EP4300615A1/en
Priority to PCT/CN2021/080416 priority patent/WO2022188136A1/zh
Publication of WO2022188136A1 publication Critical patent/WO2022188136A1/zh
Priority to US18/464,700 priority patent/US20230420687A1/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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • 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
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • 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
    • 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 electrochemical energy storage, in particular to electrochemical devices and electronic devices.
  • electrochemical devices eg, lithium-ion batteries
  • higher and higher requirements have been placed on their rate performance and energy density.
  • the current technologies for improving electrochemical devices can improve the rate performance and energy density of electrochemical devices to a certain extent, they are still unsatisfactory, and further improvements are expected.
  • Some embodiments of the present application provide an electrochemical device that includes a positive electrode, the positive electrode includes a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode active material and a composite carbon material.
  • the volume of the positive electrode active material layer is the first volume A, and the volume of pores with a diameter of less than 2 ⁇ m in the positive electrode active material layer is the second volume B, where 14% ⁇ B/A ⁇ 20%.
  • the volume of pores with a pore diameter of less than or equal to 200 nm in the positive electrode active material layer is the third volume C, 24% ⁇ C/B ⁇ 36%.
  • the composite carbon material includes carbon nanotubes and two-dimensional inorganic materials.
  • the tube length of the carbon nanotubes is greater than or equal to 2 ⁇ m.
  • the two-dimensional inorganic material includes at least one of graphene, V 2 O 5 , Nb 2 O 5 , TiO 2 , Co 3 V 2 O 8 , MoS 2 or SnO 2 .
  • the mass ratio of carbon nanotubes and the two-dimensional inorganic material is greater than or equal to 1 and less than or equal to 20.
  • the Dv50 of the two-dimensional inorganic material is less than 8 ⁇ m.
  • the mass content of the positive electrode active material in the positive electrode active material layer is greater than or equal to 97%. In some embodiments, the compaction density of the positive electrode active material layer is less than or equal to 4.2 g/cm 3 . In some embodiments, the resistance of the positive active material layer is less than 0.2 ⁇ . In some embodiments, the electrochemical device adopts a 4C discharge rate test with a capacity retention rate of ⁇ 80%.
  • the electrochemical device further includes a negative electrode that includes a negative electrode active material layer.
  • the mass content of the negative electrode active material in the negative electrode active material layer is greater than or equal to 97.4%.
  • the compaction density of the negative active material layer is less than or equal to 1.7 g/cm 3 .
  • the negative active material includes at least one of graphite, hard carbon, silicon, silicon oxide, or organosilicon.
  • Embodiments of the present application also provide an electronic device, including the above electrochemical device.
  • the positive electrode active material layer include a positive electrode active material and a composite carbon material
  • the composite carbon material can play the role of structural bonding and pore formation.
  • the binding agent makes the lithium ion production process more environmentally friendly and is conducive to improving the energy density of lithium ion batteries.
  • the use of composite carbon materials makes the volume B of the pores with a diameter of less than 2 ⁇ m in the positive active material layer and the volume of the positive active material layer.
  • the ratio of A is: 14% ⁇ B/A ⁇ 20%, which indicates that the formed cathode has abundant pores for lithium ion transport, which is beneficial to improve the rate performance of lithium ion batteries.
  • the present application provide an electrochemical device including a positive electrode including a positive electrode active material layer.
  • the positive electrode active material layer includes a positive electrode active material and a composite carbon material.
  • the volume of the positive electrode active material layer is the first volume A, and the volume of pores with a pore diameter of less than 2 ⁇ m in the positive electrode active material layer is the second volume B, where 14% ⁇ B/A ⁇ 20%.
  • the above pore volumes can be tested by the pore volume test method discussed below, but this is only exemplary and other suitable methods can be used.
  • the porosity of the positive electrode active material layer may be adjusted by cold pressing pressure, but this is only exemplary and not intended to limit the present application.
  • the composite carbon material in the positive electrode active material layer can play the role of structural bonding and pore formation.
  • 14% ⁇ B/A indicates that the formed positive electrode has abundant pores for lithium ion transport, thereby improving the electrical conductivity formed by the positive electrode. Rate capability of chemical devices. If the B/A is too small, for example, less than 14%, the positive electrode active layer is unfavorable for lithium ion transport, reducing the rate capability of the electrochemical device. However, if the B/A is too large, eg, 20% ⁇ B/A, the energy density of the electrochemical device is adversely affected.
  • the volume of pores with a pore diameter of less than or equal to 200 nm in the positive electrode active material layer is the third volume C, 24% ⁇ C/B ⁇ 36%.
  • the more pores with pore size ⁇ 200nm the more abundant the lithium ion transport channels, which is more conducive to the rapid deintercalation of lithium ions on the surface of the active material, which is particularly important for fast charging capability.
  • the cathode with 24% ⁇ C/B has better rate performance. , and enables the electrochemical device to achieve a capacity retention rate of more than 80% at a 4C discharge rate. If C/B is too small, the rapid deintercalation of lithium ions on the surface of the active material cannot be sufficiently achieved.
  • the C/B is too large, for example, 36% ⁇ C/B, it indicates that there are too many small particles inside, the small particles are easy to agglomerate, and poor dispersion may adversely affect the resistance of the active material layer, which in turn affects the rate performance of the electrochemical device. .
  • the composite carbon material includes carbon nanotubes (CNTs) and two-dimensional inorganic materials.
  • CNTs overlap each other on the surface of the positive electrode active material, which plays the role of structural bonding.
  • Two-dimensional inorganic materials can exist at the overlap between the positive electrode active material and CNTs, forming strong bonding and good conductive sites, which also play a role in creating The role of small pores (eg, pores with a pore size ⁇ 200 nm).
  • carbon nanotubes can be single-walled, multi-walled, or few-walled.
  • the two-dimensional inorganic material in the present application refers to an inorganic material in which electrons can move freely (planar motion) only on the nanoscale (1 nm to 100 nm) in two dimensions.
  • the tube length of the carbon nanotubes is greater than or equal to 2 ⁇ m. Carbon nanotubes with larger tube lengths can play a better role in structural bonding.
  • the two-dimensional inorganic material includes at least one of graphene, V 2 O 5 , Nb 2 O 5 , TiO 2 , Co 3 V 2 O 8 , MoS 2 or SnO 2 .
  • the mass ratio of the carbon nanotubes and the two-dimensional inorganic material is greater than or equal to 1 and less than or equal to 20. If the mass ratio of carbon nanotubes and two-dimensional inorganic materials is too small, the content of carbon nanotubes is relatively small, and the structural bonding of carbon nanotubes will be affected to a certain extent.
  • the Dv50 of the two-dimensional inorganic material is less than 8 ⁇ m. If the Dv50 of the two-dimensional inorganic material is too large, the conductive properties of the cathode active material layer will be adversely affected.
  • the positive active material includes lithium cobalt oxide, lithium iron phosphate, lithium iron manganese phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadyl phosphate, sodium vanadyl phosphate, lithium vanadate, manganese At least one of lithium oxide, lithium nickelate, lithium nickel cobalt manganese oxide, lithium rich manganese based material or lithium nickel cobalt aluminate.
  • the positive electrode active material layer may further include a conductive agent.
  • the conductive agent in the positive active material layer may include at least one of conductive carbon black, Ketjen black, lamellar graphite, graphene, carbon nanotubes, or carbon fibers.
  • the mass content of the positive electrode active material in the positive electrode active material layer is greater than or equal to 97%. By using a higher mass content of the positive active material, the energy density of the corresponding electrochemical device can be improved.
  • the compaction density of the positive electrode active material layer is less than or equal to 4.2 g/cm 3 . If the compaction density of the positive electrode active material layer is too large, the internal resistance of lithium ion transport may be increased, which is not conducive to the rapid transport of lithium ions. In some embodiments, the resistance of the positive active material layer may be less than 0.2 ⁇ . Therefore, it is beneficial to improve the kinetic performance of the corresponding electrochemical device.
  • the composite carbon material functions as a binder in the positive electrode active material layer.
  • the mass ratio of the positive electrode active material, the conductive agent and the composite carbon material in the positive electrode active material layer may be (95-99.5):(0-1):(0.5-5).
  • the thickness of the cathode active material layer may be 10 ⁇ m to 500 ⁇ m. It should be understood that the above description is only an example, and the positive electrode active material layer of the positive electrode may adopt any other suitable material, thickness and mass ratio.
  • the positive electrode may further include a positive electrode current collector on which the positive electrode active material layer is disposed.
  • the cathode active material layer is disposed on one or both sides of the cathode current collector.
  • the positive electrode current collector may use Al foil, and of course, other positive electrode current collectors commonly used in the art may also be used.
  • the thickness of the cathode current collector may be 1 ⁇ m to 200 ⁇ m.
  • the cathode active material layer may be coated only on a partial area of the cathode current collector.
  • the electrochemical device may also include a negative electrode.
  • the electrochemical device may include an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode.
  • the negative electrode includes a negative electrode active material layer.
  • the anode active material layer includes an anode active material, and the anode active material may include at least one of graphite, hard carbon, silicon, silicon oxide, or organic silicon.
  • the mass content of the negative electrode active material in the negative electrode active material layer is greater than or equal to 97.4%. By using a higher mass content of the negative electrode active material, the energy density of the electrochemical device formed from the negative electrode can be increased.
  • the compaction density of the negative electrode active material layer is less than or equal to 1.7 g/cm 3 under the condition that the stored electricity is discharged. If the compaction density of the negative electrode active material layer is too large, the internal resistance of lithium ion transport may be increased, which is not conducive to the rapid transport of lithium ions, and lithium is easily precipitated during the charging process of the electrochemical device.
  • a conductive agent and a binder may also be included in the anode active material layer.
  • the conductive agent in the negative active material layer may include at least one of conductive carbon black, Ketjen black, lamellar graphite, graphene, carbon nanotubes, or carbon fibers.
  • the binder in the negative active material layer may include carboxymethyl cellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyimide, polyamideimide, polysilicon At least one of oxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene.
  • the mass ratio of the negative electrode active material, the conductive agent and the binder in the negative electrode active material layer may be (90 ⁇ 98):(0.1 ⁇ 10):(0.1 ⁇ 10). It should be understood that the above are only examples and any other suitable materials and mass ratios may be employed.
  • the negative electrode may further include a negative electrode current collector, and the negative electrode active material layer is disposed on one or both sides of the negative electrode current collector.
  • the negative electrode current collector may use at least one of copper foil, nickel foil or carbon-based current collector.
  • the release membrane includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid.
  • the polyethylene includes at least one selected from high density polyethylene, low density polyethylene or ultra-high molecular weight polyethylene. Especially polyethylene and polypropylene, they have a good effect on preventing short circuits and can improve the stability of the battery through the shutdown effect.
  • the thickness of the isolation film is in the range of about 5 ⁇ m to 50 ⁇ m.
  • the surface of the separator may further include a porous layer, the porous layer is disposed on at least one surface of the substrate of the separator, the porous layer includes inorganic particles and a binder, and the inorganic particles are selected from alumina (Al 2 O 3 ), silicon oxide (SiO 2 ), magnesium oxide (MgO), titanium oxide (TiO 2 ), hafnium dioxide (HfO 2 ), tin oxide (SnO 2 ), ceria (CeO 2 ), nickel oxide (NiO) ), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO 2 ), yttrium oxide (Y 2 O 3 ), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, hydroxide At least one of calcium or barium sulfate.
  • alumina Al 2 O 3
  • silicon oxide SiO 2
  • magnesium oxide MgO
  • titanium oxide TiO 2
  • hafnium dioxide
  • the pores of the isolation membrane have diameters in the range of about 0.01 ⁇ m to 1 ⁇ m.
  • the binder of the porous layer is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyamide At least one of vinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • the porous layer on the surface of the separator can improve the heat resistance, oxidation resistance and electrolyte wettability of the separator, and enhance the adhesion between the separator and the pole piece.
  • the electrode assembly of the electrochemical device is a wound electrode assembly, a stacked electrode assembly, or a folded electrode assembly.
  • the positive electrode and/or the negative electrode of the electrochemical device may be a multi-layer structure formed by winding or stacking, or may be a single-layer structure in which a single-layer positive electrode, a separator, and a single-layer negative electrode are stacked.
  • the electrochemical device includes a lithium-ion battery, although the present application is not so limited.
  • the electrochemical device may also include an electrolyte.
  • the electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolytic solution, and the electrolytic solution includes a lithium salt and a non-aqueous solvent.
  • the lithium salt is selected from LiPF6, LiBF4 , LiAsF6, LiClO4 , LiB ( C6H5 ) 4 , LiCH3SO3 , LiCF3SO3 , LiN ( SO2CF3 ) 2 , LiC ( SO2CF3 ) 3 , LiSiF 6 , LiBOB or one or more of lithium difluoroborate.
  • LiPF 6 is chosen as the lithium salt because it has high ionic conductivity and can improve cycle characteristics.
  • the non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof.
  • the carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof.
  • chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl carbonate Ethyl esters (MEC) and combinations thereof.
  • chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl carbonate Ethyl esters (MEC) and combinations thereof.
  • Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), or a combination thereof.
  • fluorocarbonate compound examples include fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-carbonate -Difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, or a combination thereof.
  • FEC fluoroethylene carbonate
  • 1,2-difluoroethylene carbonate 1,1-difluoroethylene carbonate
  • 1,1,2-trifluoroethylene carbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-carbonate -Difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene
  • carboxylate compounds are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, decolactone, Valerolactone, mevalonolactone, caprolactone, methyl formate, or a combination thereof.
  • ether compounds are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxy Ethane, 2-methyltetrahydrofuran, tetrahydrofuran, or a combination thereof.
  • organic solvents examples include dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, methyl amide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters or combinations thereof.
  • the positive electrode, the separator, and the negative electrode are wound or stacked in sequence to form electrode parts, and then packed into, for example, an aluminum-plastic film for encapsulation, injected with electrolyte, and formed into, Encapsulation, that is, to make a lithium-ion battery. Then, the performance test of the prepared lithium-ion battery was carried out.
  • electrochemical devices eg, lithium ion batteries
  • electrochemical devices eg, lithium ion batteries
  • Other methods commonly used in the art may be employed without departing from the disclosure of the present application.
  • Embodiments of the present application also provide electronic devices including the above electrochemical devices.
  • the electronic device in the embodiment of the present application is not particularly limited, and it may be used in any electronic device known in the prior art.
  • 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.
  • Preparation of the positive electrode The positive active material lithium cobalt oxide, conductive carbon black, carbon nanotubes, and two-dimensional inorganic material titanium dioxide (TiO 2 ) were dissolved in N-methylpyrrolidone (NMP) in a weight ratio of 98.2:0.5:1.182:0.118 ) solution to form a positive electrode slurry.
  • NMP N-methylpyrrolidone
  • the positive electrode slurry is coated on the positive electrode current collector to obtain a positive electrode active material layer, and the positive electrode is obtained after drying, cold pressing and cutting.
  • Graphite, sodium carboxymethyl cellulose (CMC) and binder styrene-butadiene rubber were dissolved in deionized water in a weight ratio of 97.8:1.3:0.9 to form a negative electrode slurry.
  • CMC carboxymethyl cellulose
  • binder styrene-butadiene rubber were dissolved in deionized water in a weight ratio of 97.8:1.3:0.9 to form a negative electrode slurry.
  • the negative electrode slurry was coated on the negative electrode current collector, dried, and cut to obtain a negative electrode.
  • the isolation film substrate is polyethylene (PE) with a thickness of 8 ⁇ m, and 2 ⁇ m alumina ceramic layers are coated on both sides of the isolation film substrate, and finally, 2.5 ⁇ m alumina ceramic layers are coated on both sides of the coated ceramic layer. mg/cm 2 binder polyvinylidene fluoride (PVDF), dried.
  • PE polyethylene
  • PVDF polyvinylidene fluoride
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • PC propylene carbonate
  • VC Vinyl ester
  • Preparation of lithium ion battery stack the positive electrode, the separator and the negative electrode in sequence, so that the separator is placed between the positive electrode and the negative electrode for isolation, and then the electrode assembly is obtained by winding.
  • the electrode assembly is placed in the outer packaging aluminum-plastic film, and after dehydration at 80°C, the above electrolyte is injected and packaged, and the lithium ion battery is obtained through the process of forming, degassing, and trimming.
  • Example 2 the ratio B/A of the volume of pores having a pore diameter of less than 2 ⁇ m in the positive electrode active material layer to the volume of the positive electrode active material layer was different from that of Example 1.
  • Example 8 the ratio C/B of the volume of pores with a pore diameter of 200 nm or less in the positive electrode active material layer and the volume of pores with a pore diameter of less than 2 ⁇ m in the positive electrode active material layer was different from Example 4.
  • Example 15 to 21 the kind of the two-dimensional inorganic material was different from that of Example 4.
  • Example 29 to 35 the mass ratios of carbon nanotubes and two-dimensional inorganic materials were different from those in Example 4.
  • Example 36 to 39 the Dv50 of the two-dimensional inorganic material was different from that of Example 4.
  • Example 40 the mass content of the conductive agent in the positive electrode active material layer was different from that in Example 4.
  • Example 45 to 49 the mass content of the positive electrode active material in the positive electrode active material layer was different from that of Example 4.
  • Example 55 the mass content of the negative electrode active material in the negative electrode active material layer was different from that of Example 4.
  • Comparative Examples 1 and 2 polyvinylidene fluoride (PVDF) was used as the binder.
  • the ratio B/A of the volume of pores with a pore diameter of less than 2 ⁇ m in the positive electrode active material layer to the volume of the positive electrode active material layer is less than or equal to 14%, and the positive electrode active material layer in Comparative Example 5 has a pore diameter of less than or equal to 200 nm.
  • the ratio of the volume of pores to the volume of pores having a pore diameter of less than 2 ⁇ m in the positive electrode active material layer is C/B ⁇ 24%.
  • Table 1 shows the respective parameters and evaluation results of Examples 1 to 7 and Comparative Examples 1, 2 and 4.
  • Table 2 shows the respective parameters and evaluation results of Examples 8 to 14.
  • Table 3 shows the respective parameters and evaluation results of Examples 15 to 21 and Comparative Example 3.
  • Table 4 shows the respective parameters and evaluation results of Examples 22 to 28 and Comparative Example 5.
  • Table 5 shows the respective parameters and evaluation results of Examples 29 to 35.
  • Table 6 shows the respective parameters and evaluation results of Examples 36 to 44.
  • Table 7 shows the respective parameters and evaluation results of Examples 45 to 55.
  • Table 8 shows the respective parameters and evaluation results of Examples 56 to 65.

Abstract

电化学装置和电子装置。电化学装置包括正极，正极包括正极活性材料层，正极活性材料层包括正极活性材料和复合碳材料，正极活性材料层的体积为第一体积A，正极活性材料层中孔径小于2μm的孔的体积为第二体积B，其中，14％≤B/A≤20％。通过使正极活性材料层包括正极活性材料和复合碳材料，并且使得14％≤B/A≤20％，14％≤B/A≤20％表明形成的正极中有丰富的孔道用于锂离子传输。

Description

电化学装置和电子装置 技术领域
本申请涉及电化学储能领域，尤其涉及电化学装置和电子装置。
背景技术
随着电化学装置(例如，锂离子电池)的发展和进步，对其倍率性能和能量密度提出了越来越高的要求。虽然目前的改进电化学装置的技术能够在一定程度上提升电化学装置的倍率性能和能量密度，但是仍然令人不满意，期待进一步的改进。
发明内容
本申请的一些实施例提供了一种电化学装置，包括正极，该正极包括正极活性材料层，正极活性材料层包括正极活性材料和复合碳材料。正极活性材料层的体积为第一体积A，正极活性材料层中孔径小于2μm的孔的体积为第二体积B，其中，14％≤B/A≤20％。
在一些实施例中，正极活性材料层中孔径小于等于200nm的孔的体积为第三体积C，24％≤C/B≤36％。在一些实施例中，复合碳材料包括碳纳米管和二维无机材料。在一些实施例中，碳纳米管的管长大于等于2μm。在一些实施例中，二维无机材料包括石墨烯、V 2O 5、Nb 2O 5、TiO 2、Co 3V 2O 8、MoS 2或SnO 2中的至少一种。在一些实施例中，碳纳米管和所述二维无机材料的质量比大于等于1并且小于等于20。在一些实施例中，二维无机材料的Dv50小于8μm。
在一些实施例中，正极活性材料层中的所述正极活性材料的质量含量大于等于97％。在一些实施例中，正极活性材料层的压实密度小于等于4.2g/cm 3。在一些实施例中，正极活性材料层的电阻小于0.2Ω。在一些实施例中，电化学装置采用4C放电倍率测试，容量保持率≥80％。
在一些实施例中，电化学装置还包括负极，负极包括负极活性材料层。在一些实施例中，负极活性材料层中的负极活性材料的质量含量大于等于 97.4％。在一些实施例中，负极活性材料层的压实密度小于等于1.7g/cm 3。在一些实施例中，负极活性材料包括石墨、硬碳、硅、氧化亚硅或有机硅中的至少一种。
本申请的实施例还提供了一种电子装置，包括上述电化学装置。
本申请的实施例通过使正极活性材料层包括正极活性材料和复合碳材料，复合碳材料可以起到结构粘接和造孔的作用，一方面，由于采用复合碳材料取代现有的聚合物粘结剂，使得锂离子制作过程更环保且有利于提升锂离子电池能量密度，另一方面，采用复合碳材料，使得正极活性材料层中孔径小于2μm的孔的体积B与正极活性材料层的体积A的比值为：14％≤B/A≤20％，从而表明形成的正极中有丰富的孔道用于锂离子传输，有利于提升锂离子电池的倍率性能。
具体实施方式
下面的实施例可以使本领域技术人员更全面地理解本申请，但不以任何方式限制本申请。
本申请的一些实施例提供了一种电化学装置，该电化学装置包括正极，该正极包括正极活性材料层。在一些实施例中，正极活性材料层包括正极活性材料和复合碳材料。在一些实施例中，正极活性材料层的体积为第一体积A，正极活性材料层中孔径小于2μm的孔的体积为第二体积B，其中，14％≤B/A≤20％。上述孔体积可以通过下面讨论的孔体积测试方法进行测试，但这仅是示例性的，还可以采用其他合适的方法进行测试。在一些实施例中，可以通过冷压压力调节正极活性材料层的孔隙率，但这仅是示例性的，而不用于限制本申请。
正极活性材料层中的复合碳材料可以起到结构粘接和造孔的作用，14％≤B/A表明形成的正极中有丰富的孔道用于锂离子传输，从而改善由该正极形成的电化学装置的倍率性能。如果B/A太小，例如小于14％，则使得正极活性层不利于锂离子传输，降低电化学装置的倍率性能。然而，如果B/A太大，例如，20％＜B/A，则不利地影响电化学装置的能量密度。
在一些实施例中，正极活性材料层中孔径小于等于200nm的孔的体积为第三体积C，24％≤C/B≤36％。孔径≤200nm的孔越多，表明锂离子传输通 道越丰富，更有利于锂离子在活性材料表面快速脱嵌，对于快充能力尤为重要，24％≤C/B的正极具有更优异的倍率性能，并且使得电化学装置在4C放电倍率下能够实现80％以上的容量保持率。如果C/B太小，则不能充分实现锂离子在活性材料表面的快速脱嵌。另外，如果C/B太大，例如，36％＜C/B，则表明内部小颗粒过多，小颗粒易团聚，分散不良可能不利地影响活性材料层电阻，进而影响电化学装置的倍率性能。
在一些实施例中，复合碳材料包括碳纳米管(CNT)和二维无机材料。CNT在正极活性材料表面互相搭接，起到结构粘接的作用，二维无机材料可以存在于正极活性材料与CNT的搭接处，形成强粘接和良好的导电位点，也起到造小孔(例如，孔径≤200nm的孔)的作用。在一些实施例中，碳纳米管可以是单壁、多壁或少壁的。本申请的二维无机材料指的是电子仅可在两个维度的纳米尺度(1nm至100nm)上自由运动(平面运动)的无机材料。
在一些实施例中，碳纳米管的管长大于等于2μm。管长较大的碳纳米管可以更好地起到结构粘接的作用。在一些实施例中，二维无机材料包括石墨烯、V 2O 5、Nb 2O 5、TiO 2、Co 3V 2O 8、MoS 2或SnO 2中的至少一种。在一些实施例中，碳纳米管和二维无机材料的质量比大于等于1并且小于等于20。如果碳纳米管和二维无机材料的质量比太小，则碳纳米管含量相对较少，碳纳米管的结构粘接作用会受到一定的影响，而如果碳纳米管和二维无机材料的质量比太大，则二维无机材料的增强粘接、增加导电位点和造小孔的效果可能受到不利影响。在一些实施例中，二维无机材料的Dv50小于8μm。如果二维无机材料的Dv50太大，会不利地影响正极活性材料层的导电性能。
在一些实施例中，正极活性材料包括钴酸锂、磷酸铁锂、磷酸锰铁锂、磷酸铁钠、磷酸钒锂、磷酸钒钠、磷酸钒氧锂、磷酸钒氧钠、钒酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、富锂锰基材料或镍钴铝酸锂中的至少一种。在一些实施例中，正极活性材料层还可以包括导电剂。在一些实施例中，正极活性材料层中的导电剂可以包括导电炭黑、科琴黑、片层石墨、石墨烯、碳纳米管或碳纤维中的至少一种。在一些实施例中，正极活性材料层中的正极活性材料的质量含量大于等于97％。通过采用较高的正极活性材料的质量含量，可以提高相应的电化学装置的能量密度。在一些实施例中，正极活性材料层的压实密度小于等于4.2g/cm 3。如果正极活性材料层的压实密度太 大，则可能增大锂离子传输的内阻，不利于锂离子的快速传输。在一些实施例中，正极活性材料层的电阻可以小于0.2Ω。从而有利于提高相应的电化学装置的动力学性能。
在一些实施例中，复合碳材料在正极活性材料层中起到粘结剂的作用。在一些实施例中，正极活性材料层中的正极活性材料、导电剂和复合碳材料的质量比可以为(95～99.5)：(0～1)：(0.5～5)。在一些实施例中，正极活性材料层的厚度可以为10μm至500μm。应该理解，以上所述仅是示例，正极的正极活性材料层可以采用任何其他合适的材料、厚度和质量比。
在一些实施例中，正极还可以包括正极集流体，正极活性材料层设置在正极集流体上。在一些实施例中，正极活性材料层设置在正极集流体的一侧或两侧上。在一些实施例中，正极集流体可以采用Al箔，当然，也可以采用本领域常用的其他正极集流体。在一些实施例中，正极集流体的厚度可以为1μm至200μm。在一些实施例中，正极活性材料层可以仅涂覆在正极集流体的部分区域上。
在一些实施例中，电化学装置还可以包括负极。在一些实施例中，电化学装置可以包括电极组件，电极组件包括正极、负极以及设置在正极和负极之间的隔离膜。
在一些实施例中，负极包括负极活性材料层。在一些实施例中，负极活性材料层包括负极活性材料，负极活性材料可以包括石墨、硬碳、硅、氧化亚硅或有机硅中的至少一种。在一些实施例中，负极活性材料层中的负极活性材料的质量含量大于等于97.4％。通过采用较高质量含量的负极活性材料，可以提高由该负极形成的电化学装置的能量密度。在一些实施例中，在存储的电量被放空的条件下，负极活性材料层的压实密度小于等于1.7g/cm 3。如果负极活性材料层的压实密度太大，则可能增大锂离子传输的内阻，不利于锂离子的快速传输，并且在电化学装置的充电过程中容易析锂。
在一些实施例中，负极活性材料层中还可以包括导电剂和粘结剂。在一些实施例中，负极活性材料层中的导电剂可以包括导电炭黑、科琴黑、片层石墨、石墨烯、碳纳米管或碳纤维中的至少一种。在一些实施例中，负极活 性材料层中的粘结剂可以包括羧甲基纤维素(CMC)、聚丙烯酸、聚乙烯基吡咯烷酮、聚苯胺、聚酰亚胺、聚酰胺酰亚胺、聚硅氧烷、丁苯橡胶、环氧树脂、聚酯树脂、聚氨酯树脂或聚芴中的至少一种。在一些实施例中，负极活性材料层中的负极活性材料、导电剂和粘结剂的质量比可以为(90～98)：(0.1～10)：(0.1～10)。应该理解，以上所述仅是示例，可以采用任何其他合适的材料和质量比。
在一些实施例中，负极还可以包括负极集流体，负极活性材料层设置在负极集流体的一侧或两侧上。在一些实施例中，负极集流体可以采用铜箔、镍箔或碳基集流体中的至少一种。
在一些实施例中，隔离膜包括聚乙烯、聚丙烯、聚偏氟乙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺或芳纶中的至少一种。例如，聚乙烯包括选自高密度聚乙烯、低密度聚乙烯或超高分子量聚乙烯中的至少一种。尤其是聚乙烯和聚丙烯，它们对防止短路具有良好的作用，并可以通过关断效应改善电池的稳定性。在一些实施例中，隔离膜的厚度在约5μm至50μm的范围内。
在一些实施例中，隔离膜表面还可以包括多孔层，多孔层设置在隔离膜的基材的至少一个表面上，多孔层包括无机颗粒和粘结剂，无机颗粒选自氧化铝(Al 2O 3)、氧化硅(SiO 2)、氧化镁(MgO)、氧化钛(TiO 2)、二氧化铪(HfO 2)、氧化锡(SnO 2)、二氧化铈(CeO 2)、氧化镍(NiO)、氧化锌(ZnO)、氧化钙(CaO)、氧化锆(ZrO 2)、氧化钇(Y 2O 3)、碳化硅(SiC)、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙或硫酸钡中的至少一种。在一些实施例中，隔离膜的孔具有在约0.01μm至1μm的范围的直径。多孔层的粘结剂选自聚偏氟乙烯、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、羧甲基纤维素钠、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯或聚六氟丙烯中的至少一种。隔离膜表面的多孔层可以提升隔离膜的耐热性能、抗氧化性能和电解质浸润性能，增强隔离膜与极片之间的粘结性。
在本申请的一些实施例中，电化学装置的电极组件为卷绕式电极组件、堆叠式电极组件或折叠式电极组件。在一些实施例中，电化学装置的正极和/ 或负极可以是卷绕或堆叠式形成的多层结构，也可以是单层正极、隔离膜、单层负极叠加的单层结构。
在一些实施例中，电化学装置包括锂离子电池，但是本申请不限于此。在一些实施例中，电化学装置还可以包括电解质。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。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或者二氟硼酸锂中的一种或多种。例如，锂盐选用LiPF 6，因为它具有高的离子导电率并可以改善循环特性。
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。
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。
链状碳酸酯化合物的实例为碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、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。所述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)或者其组合。所述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或者其组合。
羧酸酯化合物的实例为乙酸甲酯、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、甲酸甲酯或者其组合。
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、四氢呋喃或者其组合。
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、和磷酸酯或者其组合。
在本申请的一些实施例中，以锂离子电池为例，将正极、隔离膜、负极按顺序卷绕或堆叠成电极件，之后装入例如铝塑膜中进行封装，注入电解液，化成、封装，即制成锂离子电池。然后，对制备的锂离子电池进行性能测试。
本领域的技术人员将理解，以上描述的电化学装置(例如，锂离子电池)的制备方法仅是实施例。在不背离本申请公开的内容的基础上，可以采用本领域常用的其他方法。
本申请的实施例还提供了包括上述电化学装置的电子装置。本申请实施例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。
下面列举了一些具体实施例和对比例以更好地对本申请进行说明，其中，采用锂离子电池作为示例。
实施例1
正极的制备：将正极活性材料钴酸锂、导电炭黑、碳纳米管、二维无机材料二氧化钛(TiO 2)按重量比98.2：0.5：1.182：0.118的比例溶于N-甲基吡咯烷酮(NMP)溶液中，形成正极浆料。采用铝箔作为正极集流体，将正极浆料涂覆于正极集流体上，得到正极活性材料层，经过干燥、冷压、裁切后得到正极。
负极的制备：将石墨，羧甲基纤维素钠(CMC)和粘结剂丁苯橡胶按重量比97.8：1.3：0.9的比例溶于去离子水中，形成负极浆料。采用10μm厚度 铜箔作为负极集流体，将负极浆料涂覆于负极集流体上，干燥，裁切后得到负极。
隔离膜的制备：隔离膜基材为8μm厚的聚乙烯(PE)，在隔离膜基材的两侧各涂覆2μm氧化铝陶瓷层，最后在涂布了陶瓷层的两侧各涂覆2.5mg/cm 2的粘结剂聚偏氟乙烯(PVDF)，烘干。
电解液的制备：在含水量小于10ppm的环境下，将LiPF 6加入非水有机溶剂(碳酸乙烯酯(EC)：碳酸二乙酯(DEC)：碳酸丙烯酯(PC)、丙烯酸酯：碳酸亚乙烯酯(VC)＝20：30：20：28：2，重量比)，LiPF 6的浓度为1.15mol/L，混合均匀，得到电解液。
锂离子电池的制备：将正极、隔离膜、负极按顺序依次叠好，使隔离膜处于正极和负极中间起到隔离的作用，并卷绕得到电极组件。将电极组件置于外包装铝塑膜中，在80℃下脱去水分后，注入上述电解液并封装，经过化成，脱气，切边等工艺流程得到锂离子电池。
实施例和对比例是在实施例1步骤的基础上进行参数变更，具体变更的参数如下面的表格所示。
在实施例2至7中，正极活性材料层中孔径小于2μm的孔的体积和正极活性材料层的体积的比值B/A与实施例1不同。
在实施例8至14中，正极活性材料层中孔径小于等于200nm的孔的体积和正极活性材料层中孔径小于2μm的孔的体积的比值C/B与实施例4不同。
在实施例15至21中，二维无机材料的种类与实施例4不同。
在实施例22至24中，碳纳米管的种类与实施例4不同。
在实施例25至28中，碳纳米管的长度与实施例4不同。
在实施例29至35中，碳纳米管和二维无机材料的质量比与实施例4不同。
在实施例36至39中，二维无机材料的Dv50与实施例4不同。
在实施例40至44中，正极活性材料层中的导电剂的质量含量与实施例4不同。
在实施例45至49中，正极活性材料层中的正极活性材料的质量含量与实施例4不同。
在实施例50至54中，电量被放空时的正极活性材料层的压实密度与实施例4不同。
在实施例55至59中，负极活性材料层中的负极活性材料的质量含量与实施例4不同。
在实施例60至64中，电量被放空时的负极活性材料层的压实密度与实施例4不同。
在对比例1和2中，粘结剂采用聚偏氟乙烯(PVDF)。对比例3至5中正极活性材料层中孔径小于2μm的孔的体积和正极活性材料层的体积的比值B/A小于等于14％，并且对比例5中正极活性材料层中孔径小于等于200nm的孔的体积和正极活性材料层中孔径小于2μm的孔的体积的比值C/B＜24％。
下面描述本申请的各个参数的测试方法。
孔体积测试：
Autopore V 9620压汞仪，测试方法如下：
裁片模具取固定面积S的待测样品，(若待测样品为电解液接触过的样品，需先用DMC溶剂浸泡清洗3次，一次浸泡1min，晾至重量不再变化后再进行压汞测试)，万分尺测箔材厚度D1，算得样品中箔材体积V1＝S xD1；将待测样品装入膨胀计样品池。首先将膨胀计装入压汞仪低压仓，选择“低压模式”测得样品总体积V(膨胀计标准样品池体积扣除低压进汞体积算得)，活性材料层体积A＝V-V1；将膨胀计装入高压仓，仪器选择“高压模式”测得进汞曲线即为孔分布曲线，积分面积即为孔体积。≤2μm孔径对应压力的累积进汞体积为体积B，≤200nm孔径对应压力的累计进汞体积即为小孔体积C。
活性材料层电阻测试：
将电池放电至0％荷电状态下，拆解得到待测极片，日置BT3562电阻仪进行数据采集。将待测极片放置在测试样品台，调试气压至压力感器测得值在设置区间，检查测试压头是否对活性材料层结构造成破坏。确认气压正常 后进行测试。使用交流四端子测试法，向活性材料层加载交流电流I s，传感器采集测试物引起的电压降V IS，根据欧姆定律得相应电阻R＝V IS/I S。
活性材料层的压实密度测试：
将电池放电至0％荷电状态下，拆解得到待测极片，固定模具取已知面积s的极片，称重并万分尺测厚度。扣除箔材重量(已知面积与密度)与厚度(万分尺测得)。得到活性材料层的重量m与厚度h，活性材料层的重量与厚度的比值即为放空电状态的活性材料层的压实密度＝m/hs。
4C放电倍率下容量保持率测试：
将锂离子电池置于25℃±2℃的恒温箱中静置2小时，以1C倍率进行充电至4.48V，然后在4.48V下恒压充电至0.05C。以1C倍率放电至3.0V进行循环性能测试，得到参考放电容量；以4C倍率放电至3.0V进行循环性能测试，得到实际放电容量，4C放电倍率下容量保持率＝实际放电容量/参考放电容量*100％。
表1示出了实施例1至7和对比例1、2和4的各个参数和评估结果。
表1
Figure PCTCN2021080416-appb-000001
Figure PCTCN2021080416-appb-000002
通过比较实施例1至7和对比例1可知，通过采用复合碳材料，并且14％≤B/A≤20％，正极活性材料层的电阻明显减小，并且电化学装置在4C放电倍率下的容量保持率明显提升。
通过比较实施例1至7和对比例3可知，在14％≤B/A时，相对于B/A等于13％的情况，正极活性材料层的电阻变化不大，但是电化学装置在4C放电倍率下的容量保持率明显提升。
通过比较实施例1至7和对比例4可知，在B/A≤20％时，相对于B/A等于21％的情况，正极活性材料层的电阻变化不大，但是电化学装置在4C放电倍率下的容量保持率明显提升。
表2示出了实施例8至14的各个参数和评估结果。
表2
Figure PCTCN2021080416-appb-000003
通过比较实施例8至14和对比例2可知，在24％≤C/B≤36％时，采用复合碳材料的正极活性材料层的电阻明显减小，并且电化学装置在4C放电倍率下的容量保持率明显提升。
通过比较实施例8至14和对比例5可知，在24％≤C/B时，相对于C/B等于23％的情况，正极活性材料层的电阻减小，电化学装置在4C放电倍率下的容量保持率明显提升。
通过比较实施例8至14和对比例6可知，在C/B≤36％时，相对于C/B等于37％的情况，正极活性材料层的电阻减小，电化学装置在4C放电倍率下的容量保持率明显提升。
表3示出了实施例15至21和对比例3的各个参数和评估结果。
表3
Figure PCTCN2021080416-appb-000004
Figure PCTCN2021080416-appb-000005
通过比较实施例15至21可知，采用各种不同种类的二维无机材料，正极活性材料层的电阻变化不大，并且电化学装置在4C放电倍率下的容量保持率变化不大。
通过比较实施例15至21和对比例7可知，当不添加二维无机材料时，正极活性材料层的电阻变化不大，但是电化学装置在4C放电倍率下的容量保持率下降。
表4示出了实施例22至28和对比例5的各个参数和评估结果。
表4
Figure PCTCN2021080416-appb-000006
Figure PCTCN2021080416-appb-000007
通过比较实施例22至24可知，采用少壁或单壁的碳纳米管，相对于采用多壁的碳纳米管，正极活性材料层的电阻减小，并且电化学装置在4C放电倍率下的容量保持率提升。
通过比较实施例25至28可知，随着碳纳米管的管长的增大，正极活性材料层的电阻有降低的趋势，但是电化学装置在4C放电倍率下的容量保持率有一定程度的下降。
通过比较实施例25至28和对比例8可知，当碳纳米管的管长≥2μm时，正极活性材料层的电阻变化不大，但电化学装置在4C放电倍率下的容量保持率明显提升。
表5示出了实施例29至35的各个参数和评估结果。
表5
Figure PCTCN2021080416-appb-000008
Figure PCTCN2021080416-appb-000009
通过比较实施例29至35可知，随着碳纳米管和二维无机材料二氧化钛的质量比的增大，正极活性材料层的电阻减小，但是电化学装置在4C放电倍率下的容量保持率有一定的下降。
表6示出了实施例36至44的各个参数和评估结果。
表6
Figure PCTCN2021080416-appb-000010
Figure PCTCN2021080416-appb-000011
通过比较实施例36至39可知，在二维无机材料的Dv50小于8μm时，随着二维无机材料的Dv50的增大，正极活性材料层的电阻先减小后增大，并且电化学装置在4C放电倍率下的容量保持率先提升后降低。
通过比较实施例36至39和对比例9可知，在二维无机材料的1μm＜Dv50，相对于Dv50＝0.1μm活性材料层的电阻明显减小，并且电化学装置在4C放电倍率下的容量保持率明显提升。
通过比较实施例40至44可知，随着导电剂导电炭黑的质量含量的增大，正极活性材料层的电阻先减小后增大，并且电化学装置在4C放电倍率下的容量保持率提升。
表7示出了实施例45至55的各个参数和评估结果。
表7
Figure PCTCN2021080416-appb-000012
Figure PCTCN2021080416-appb-000013
通过比较实施例45至50可知，随着正极活性材料层中的正极活性材料的质量含量的降低，复合碳材料质量含量的增大，正极活性材料层的电阻有降低的趋势，并且电化学装置在4C放电倍率下的容量保持率有上升的趋势。
通过比较实施例51至55可知，随着正极活性材料层压实密度的增大，正极活性材料层的电阻有增大的趋势，并且电化学装置在4C放电倍率下的容量保持率有下降的趋势。
表8示出了实施例56至65的各个参数和评估结果。
表8
Figure PCTCN2021080416-appb-000014
Figure PCTCN2021080416-appb-000015
通过比较实施例56至60可知，随着负极活性材料层中的负极活性材料的质量含量的增大，正极活性材料层的电阻变化不大，并且电化学装置在4C放电倍率下的容量保持率先提升后下降。
通过比较实施例61至65可知，随着负极活性材料层压实密度的增大，正极活性材料层的电阻变化不大，并且电化学装置在4C放电倍率下的容量保持率有下降的趋势。
以上描述仅为本申请的较佳实施例以及对所运用技术原理的说明。本领域技术人员应当理解，本申请中所涉及的公开范围，并不限于上述技术特征的特定组合而成的技术方案，同时也应涵盖由上述技术特征或其等同 特征进行任意组合而形成的其它技术方案。例如上述特征与本申请中公开的具有类似功能的技术特征进行互相替换而形成的技术方案。

Claims (11)

  1. 一种电化学装置，包括正极，所述正极包括：
    正极活性材料层，所述正极活性材料层包括正极活性材料和复合碳材料，所述正极活性材料层的体积为第一体积A，所述正极活性材料层中孔径小于2μm的孔的体积为第二体积B，其中，14％≤B/A≤20％。
  2. 根据权利要求1所述的电化学装置，其中，所述正极活性材料层中孔径小于等于200nm的孔的体积为第三体积C，其中，24％≤C/B≤36％。
  3. 根据权利要求1所述的电化学装置，其中，所述复合碳材料包括碳纳米管和二维无机材料。
  4. 根据权利要求3所述的电化学装置，其中，所述碳纳米管的管长大于等于2μm。
  5. 根据权利要求3所述的电化学装置，其中，所述二维无机材料包括石墨烯、V 2O 5、Nb 2O 5、TiO 2、Co 3V 2O 8、MoS 2或SnO 2中的至少一种。
  6. 根据权利要求3所述的电化学装置，其中，所述碳纳米管和所述二维无机材料的质量比大于等于1并且小于等于20。
  7. 根据权利要求3所述的电化学装置，其中，所述二维无机材料的Dv50小于8μm。
  8. 根据权利要求1所述的电化学装置，其中，所述正极满足以下条件之一：
    所述正极活性材料层中的所述正极活性材料的质量含量大于等于97％；
    所述正极活性材料层的压实密度小于等于4.2g/cm 3；
    所述正极活性材料层的电阻小于0.2Ω。
  9. 根据权利要求1所述的电化学装置，其中，所述电化学装置采用4C放电倍率测试，容量保持率≥80％。
  10. 根据权利要求1所述的电化学装置，其中，所述电化学装置还包括负极，所述负极包括负极活性材料层，所述负极满足以下条件之一：
    所述负极活性材料层中的负极活性材料的质量含量大于等于97.4％；
    所述负极活性材料层的压实密度小于等于1.7g/cm 3；
    所述负极活性材料包括石墨、硬碳、硅、氧化亚硅或有机硅中的至少一种。
  11. 一种电子装置，包括根据权利要求1至10中任一项所述的电化学装置。
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