WO2022206128A1 - 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
WO2022206128A1
WO2022206128A1 PCT/CN2022/072438 CN2022072438W WO2022206128A1 WO 2022206128 A1 WO2022206128 A1 WO 2022206128A1 CN 2022072438 W CN2022072438 W CN 2022072438W WO 2022206128 A1 WO2022206128 A1 WO 2022206128A1
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layer
pole piece
active material
electrochemical device
average pore
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PCT/CN2022/072438
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English (en)
French (fr)
Inventor
谢先惠
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宁德新能源科技有限公司
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Publication of WO2022206128A1 publication Critical patent/WO2022206128A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application relates to the field of electronic technology, in particular to electrochemical devices and electronic devices.
  • the coating amount per unit area of the active material layer can be increased.
  • increasing the coating amount per unit area of the active material layer poses challenges to the adhesion and resistance of the pole piece.
  • the embodiments of the present application provide an electrochemical device, the electrochemical device includes an electrode assembly, and the electrode assembly includes a positive pole piece, a negative pole piece, and a separator between the positive pole piece and the negative pole piece.
  • the positive electrode sheet or the negative electrode sheet includes a current collector, a first layer, a second layer, and an active material layer. The first layer is located between the current collector and the second layer, and the second layer is located between the first layer and the active material layer. The average pore size of the first layer is smaller than the average pore size of the second layer.
  • the average pore size of the first layer is 0.01 ⁇ m to 0.1 ⁇ m, and the average pore size of the second layer is 0.1 ⁇ m to 50 ⁇ m. In some embodiments, the average thickness of the first layer is 0.1 ⁇ m to 10 ⁇ m, and the average thickness of the second layer is 0.1 ⁇ m to 10 ⁇ m.
  • the first layer includes a first conductive agent and a first binder, and the second layer includes a second conductive agent and a second binder.
  • the first conductive agent and the second conductive agent each independently include at least one of carbon black, carbon nanotubes, conductive graphite, acetylene black, ketjen black, or graphene.
  • the first binder and the second binder each independently comprise at least one of acrylic resin, styrene butadiene rubber, polyacrylic acid, sodium carboxymethyl cellulose, or sodium alginate.
  • the mass ratio of the first conductive agent to the first binder is 1:(0.1 to 1).
  • the mass ratio of the second conductive agent to the second binder is 1:(0.1 to 1).
  • the bonding force between the active material layer and the second layer is 10 N/m to 50 N/m.
  • Embodiments of the present application also provide an electronic device, including the above electrochemical device.
  • the embodiment of the present application increases the contact area between the current collector and the active material layer by disposing two coatings between the current collector and the active material layer, and making the average pore size of the first layer smaller than the average pore size of the second layer, In turn, the bonding force of the pole piece is improved, the charge transfer distance is shortened, and the internal resistance of the pole piece is reduced.
  • FIG. 1 shows a cross-sectional view of a pole piece of some embodiments of the present application, taken in a plane defined by a thickness direction and a width direction.
  • the electrochemical device includes an electrode assembly, and the electrode assembly includes a positive pole piece, a negative pole piece, and a separator disposed between the positive pole piece and the negative pole piece.
  • the positive or negative electrode sheet includes a current collector 101 , a first layer 102 , a second layer 103 and an active material layer 104 , the first layer 102 is located between the current collector 101 and the second layer 104 . Between the layers 103 , the second layer 103 is located between the first layer 102 and the active material layer 104 .
  • the positive pole piece As an example, and it should be understood that the negative pole piece may adopt a corresponding structure. It should be understood that the first layer 102 , the second layer 103 and the active material layer 104 may be located on one side of the current collector 101 , or may all be located on both sides of the current collector 101 .
  • the active material layer 104 includes an active material, eg, a positive active material.
  • the average pore size of the first layer 102 is smaller than the average pore size of the second layer 103 . Since the first layer 102 is closer to the current collector 101 than the second layer 103 , when the average pore size of the first layer 102 is smaller than that of the second layer 103 , it is beneficial to enhance the contact between the current collector 101 and the first layer 102 .
  • the combination of the first layer 102 and the second layer 103 with different pore sizes increases the contact area between the active material layer 104, the second layer 103, the first layer 102 and the current collector 101, and increasing the contact area can improve the The adhesion of the pole piece and the shortening of the electron transfer path reduce the resistance of the pole piece.
  • the average pore size of the first layer 102 is 0.01 ⁇ m to 0.1 ⁇ m
  • the average pore size of the second layer 103 is 0.1 ⁇ m to 50 ⁇ m.
  • the average pore size of the second layer 103 is similar to the particle size of the active material, which facilitates the matching contact between the active material and the second layer 103 .
  • the average pore size of the first layer 102 is 0.01 ⁇ m to 0.1 ⁇ m, which is smaller than that of the second layer 103 , which is beneficial to enhance the contact between the current collector 101 and the first layer 102 .
  • the average pore size of the first layer 102 is too large, it is not conducive to the improvement of the adhesion between the first layer 102 and the current collector 101 . If the average pore size of the second layer 103 is too large, it is not conducive to the improvement of the energy density of the electrochemical device.
  • the average pore size of the first layer 102 and the second layer 103 can be tested by the following method: using a scanning electron microscope to test the cross-section of the coating after the cross-section polishing process, randomly selecting 100 holes in the coating, The 25 pores with the largest pore size and the 25 pores with the smallest pore size were eliminated, and the average pore size of the remaining 50 pores was calculated as the average pore size of the coating.
  • this is only exemplary, and other suitable average pore size testing methods may also be employed.
  • the average thickness of the first layer 102 is 0.1 ⁇ m to 10 ⁇ m
  • the average thickness of the second layer 103 is 0.1 ⁇ m to 10 ⁇ m. If the thickness of the first layer 102 and/or the second layer 103 is too small, it is unfavorable to improve the adhesion of the pole piece. If the thickness of the first layer 102 and/or the second layer 103 is too large, it is not conducive to the improvement of the energy density of the electrochemical device.
  • the average thickness of the first layer 102 is 0.1 ⁇ m to 5 ⁇ m
  • the average thickness of the second layer 103 is 0.1 ⁇ m to 5 ⁇ m.
  • the average thickness of the first layer 102 is 0.1 ⁇ m to 3 ⁇ m
  • the average thickness of the second layer 103 is 0.1 ⁇ m to 3 ⁇ m.
  • the average thickness of the first layer 102 and the second layer 103 can be tested by the following method: use a scanning electron microscope to test the cross-section of the coating after the cross-section polishing process, make a straight line perpendicular to the plane of the current collector, vertical The line intersects the upper and lower edges of the coating at two points, and the distance between the two points is measured as the thickness of the coating.
  • 100 thickness values of the coating are randomly selected, and the 25 thickness values with the largest value and the 25 thickness values with the smallest value are selected. If it is eliminated, the average value of the remaining 50 thickness values is calculated as the average thickness of the coating.
  • the first layer 102 includes a first conductive agent and a first binder
  • the second layer 103 includes a second conductive agent and a second binder.
  • the first conductive agent and the second conductive agent each independently include at least one of carbon black, carbon nanotubes, conductive graphite, acetylene black, ketjen black, or graphene.
  • the first binder and the second binder each independently comprise at least one of acrylic resin, styrene butadiene rubber, polyacrylic acid, sodium carboxymethyl cellulose, or sodium alginate.
  • the mass ratio of the first conductive agent to the first binder is 1:(0.1 to 1). In some embodiments, the mass ratio of the second conductive agent to the second binder is 1:(0.1 to 1).
  • the mass ratio By adopting such a mass ratio, on the basis of ensuring the adhesive force between the current collector 101 , the first layer 102 , the second layer 103 and the active material layer 104 , it is helpful to reduce the first layer 102 and the second layer 103 The electron transfer resistance, thereby reducing the pole piece resistance. If the mass content of the first conductive agent is too small, the electrical conductivity of the first layer 102 will be adversely affected, and furthermore, the reduction of the electrode sheet resistance will be adversely affected. If the mass content of the first conductive agent is too large, the excess first conductive agent will adversely affect the performance of the adhesion performance of the first layer 102 because the first conductive agent itself has slightly weaker adhesion performance.
  • the mass content of the second conductive agent is too small, the conductivity of the second layer 103 will be adversely affected, and furthermore, the reduction of the electrode sheet resistance will be adversely affected. If the mass content of the second conductive agent is too large, the excess of the second conductive agent will adversely affect the performance of the adhesion performance of the second layer 103 because the adhesion performance of the second conductive agent itself is slightly weak.
  • the bonding force between the active material layer 104 and the second layer 103 is 10 N/m to 50 N/m. By achieving such a cohesive force, the cohesive force of the entire pole piece is improved. Generally, the bonding between the active material layer 104 and the second layer 103 in the pole piece is relatively weak, so the average bonding force between the active material layer 104 and the second layer 103 can be regarded as the overall adhesion of the pole piece knot force.
  • the adhesive force between the active material layer 104 and the second layer 103 can be tested by the following method: adhering the double-sided tape to any side of the pole piece with a size of 15*60mm to be tested, and using The pressure roller is compacted to make the pressure roller and the pole piece completely fit; the other side of the above double-sided tape is pasted on the surface of the stainless steel plate, and the tensile machine is used to test it.
  • the bending angle is 90°
  • the bending end of the sample is fixed on the clamp above the tensile machine
  • the angle of the sample is adjusted to ensure that one end of the sample is in a vertical position with the other end, and then the sample is stretched at a speed of 50mm/min until the sample is All are peeled off from the stainless steel plate, and the displacement and force during the recording process are recorded.
  • the force when the force is balanced is the adhesion force of the pole piece; 10 samples are randomly tested, and the average value of the adhesion force is taken as the adhesion force.
  • this is only exemplary, and other suitable adhesion testing methods may also be used.
  • the pole pieces have an average resistance of 0.5 Ohm to 5 Ohm. In this way, good electrical performance of the electrochemical device can be obtained.
  • the average resistance of the pole piece can be tested by the following methods: using a two-probe resistance tester for testing, adjusting the pressure between the two probes to 0.4t, placing the pole piece to be tested in the middle of the probes, Run the instrument, record the internal resistance value shown by the resistance tester after 5 seconds, test 20 different points according to the above method, and calculate the average value of the recorded 20 internal resistances as the average resistance of the pole piece.
  • this is only exemplary, and other suitable resistance testing methods may also be used.
  • the internal resistance (IMP) of the battery may be 1 mOhm to 10 mOhm. In this way, good electrical performance of the electrochemical device can be obtained.
  • the IMP of the battery can be tested by the following methods: use a manual OCV/IMP voltage internal resistance tester to test, place the battery to be tested on the material level of the tester, run the instrument, and record the internal resistance after 5 seconds For the IMP value shown by the tester, test 20 different batteries according to the above method, and calculate the average value of the internal resistance of the 20 batteries recorded as the IMP of the battery corresponding to the pole piece. Of course, this is only an example, and other suitable internal resistance testing methods can also be used.
  • the first layer 102 and the second layer 103 may be formed by an electrospinning method. By using the electrospinning method, the pore size and thickness of the first layer 102 and the second layer 103 can be better controlled.
  • the active material layer 104 is a positive electrode active material layer and includes a positive electrode active material.
  • 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 positive electrode active material layer may further include a binder, and the binder in the positive electrode active material layer may include carboxymethyl cellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyamide At least one of imine, polyamideimide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene.
  • CMC carboxymethyl cellulose
  • the mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode active material layer may be (80 to 99):(0.1 to 10):(0.1 to 10).
  • the thickness of the cathode active material layer may be 10 ⁇ m to 500 ⁇ m. It should be understood that the above descriptions are only examples, and any other suitable materials, thicknesses and mass ratios may be used for the positive electrode active material layer of the positive electrode sheet.
  • the current collector of the positive electrode sheet can be made of Al foil, of course, other current collectors commonly used in the art can also be used.
  • the thickness of the current collector of the positive electrode sheet may be 1 ⁇ m to 200 ⁇ m.
  • the positive active material layer may be coated only on a partial area of the current collector of the positive electrode sheet.
  • the active material layer 104 is a negative electrode active material layer when the negative electrode pole piece includes the above structure.
  • 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.
  • 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 anode active material, the conductive agent, and the binder in the anode active material layer may be (80 to 98):(0.1 to 10):(0.1 to 10). It should be understood that the above are only examples and any other suitable materials and mass ratios may be employed.
  • the current collector of the negative electrode sheet can be 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 isolation membrane may further include a porous layer, the porous layer is disposed on at least one surface of the substrate of the isolation membrane, 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 pole piece and/or the negative pole piece of the electrochemical device may be a multi-layer structure formed by winding or stacking, or may be a single-layer positive pole piece, a separator, and a single-layer negative pole piece superimposed single-layer structure.
  • 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, separator, and negative electrode are sequentially wound or stacked to form electrode parts, which are then packaged in, for example, an aluminum-plastic film, and then injected into an electrolytic film. Liquid, chemical formation, packaging, that is, into 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.
  • the positive pole piece includes the first layer and the second layer.
  • Preparation of positive pole piece using aluminum foil as the current collector of the positive pole piece, and uniformly coating the surface of the aluminum foil with conductive coating slurry, specifically: acetylene black, graphene and acrylic resin in a weight ratio of 1:0.05:0.8 After mixing, stir evenly to obtain conductive coating slurry; put the conductive coating slurry into the electrospinning machine, adjust the voltage of the electrospinning machine to 10kV, the slurry pushing speed is 0.5mL/h, and the electrospinning nozzle is connected to the collector. The distance of the fluid was 15 cm; after spraying the conductive coating slurry onto the current collector, it was baked at 110° C.
  • conductive coating slurry specifically: acetylene black, graphene and acrylic resin in a weight ratio of 1:0.05:0.8
  • the positive electrode active material lithium iron phosphate, the conductive agent conductive carbon black, and the binder polyacrylic acid are dissolved in N-methylpyrrolidone (NMP) solution in a weight ratio of 98.2:0.5:1.3 to form a positive electrode slurry.
  • NMP N-methylpyrrolidone
  • the material was coated on the second layer with a thickness of 200 ⁇ m, baked at 110° C. for 10 min, and then cold-pressed and cut to obtain a positive pole piece.
  • negative pole piece graphite, sodium carboxymethyl cellulose (CMC) and binder styrene-butadiene rubber are dissolved in deionized water in a weight ratio of 97.8:1.3:0.9 to form a negative electrode slurry.
  • a 10 ⁇ m-thick copper foil was used as the current collector of the negative electrode, and the negative electrode slurry was coated on the current collector of the negative electrode, dried, and cut to obtain a negative electrode.
  • the isolation film substrate is polyethylene (PE) with a thickness of 8 ⁇ m, and a 2 ⁇ m alumina ceramic layer is coated on both sides of the isolation film substrate, and finally 2.5 ⁇ m is coated on both sides of the coated ceramic layer.
  • PE polyethylene
  • PVDF polyvinylidene fluoride
  • EC ethylene carbonate
  • PC propylene carbonate
  • Preparation of lithium ion battery stack the positive pole piece, the separator and the negative pole piece in order, so that the separator is in the middle of the positive pole piece and the negative pole piece to play a role of isolation, and coil to obtain an electrode assembly.
  • 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.
  • Table 1 shows the respective parameters and evaluation results of Examples 1 to 12 and Comparative Examples 1 to 3.
  • the average pore diameter of the first layer was different from that of Example 1, and the average pore diameter of the second layer in Examples 4 to 7, 9 to 12 and Comparative Examples 1 to 2 Different from Example 1, other parameters are the same as Example 1.
  • the second layer was not formed in the positive electrode sheet, and the thickness of the first layer was 0.05 ⁇ m.
  • Table 2 shows the respective parameters and evaluation results of Examples 13 to 31. Among them, in Examples 13 to 31, the average pore diameter of the first layer was 0.05 ⁇ m, and the average pore diameter of the second layer was 9 ⁇ m. In Examples 13 to 31, other parameters refer to Example 1 except that the thickness of the first layer and the second layer, the composition and content of the conductive agent, and the composition and content of the binder are different from those in Example 1.

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Abstract

本申请提供了电化学装置和电子装置。电化学装置包括正极极片、负极极片以及位于正极极片和负极极片之间的隔离膜。正极极片或负极极片包括集流体、第一层、第二层和活性材料层。第一层位于集流体和第二层之间，第二层位于第一层和活性材料层之间。第一层的平均孔径小于第二层的平均孔径。本申请的实施例通过在集流体和活性材料层之间设置两个涂层，并且使第一层的平均孔径小于第二层的平均孔径，增大了集流体与活性材料层的接触面积，进而提高极片粘结力，缩短电荷传递距离，减小极片内阻。

Description

电化学装置和电子装置
相关申请的交叉引用
本申请基于申请号为202110342108.9、申请日为2021年03月30日，名称为“电化学装置和电子装置”的中国专利申请提出，并要求该中国专利申请的优先权，该中国专利申请的全部内容在此引入本申请作为参考。
技术领域
本申请涉及电子技术领域，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)的在各类电子产品中的广泛应用，用户对于电化学装置的能量密度、倍率性能和循环性能也提出了越来越高的要求。通常地，为了提高电化学装置的能量密度，可以增大活性材料层的单位面积的涂覆量。然而，增大活性材料层的单位面积的涂覆量，给极片的粘结力和电阻提出了挑战。
因此，期待对极片的粘结力和电阻性能的进一步改进。
发明内容
本申请的实施例提供了一种电化学装置，电化学装置包括电极组件，电极组件包括正极极片、负极极片以及位于正极极片和负极极片之间的隔离膜。正极极片或负极极片包括集流体、第一层、第二层和活性材料层。第一层位于集流体和第二层之间，第二层位于第一层和活性材料层之间。第一层的平均孔径小于第二层的平均孔径。
在一些实施例中，第一层的平均孔径为0.01μm至0.1μm，第二层的平均孔径为0.1μm至50μm。在一些实施例中，第一层的平均厚度为0.1μm至10μm，第二层的平均厚度为0.1μm至10μm。在一些实施例中，第一层包括第一导电剂和第一粘结剂，第二层包括第二导电剂和第二粘结剂。在一些实施例中，第一导电剂和第二导电剂各自独立地包括炭黑、碳纳米管、导电石墨、乙炔 黑、科琴黑或石墨烯中的至少一种。在一些实施例中，第一粘结剂和第二粘结剂各自独立地包括丙烯酸树脂、丁苯橡胶、聚丙烯酸类、羧甲基纤维素钠或海藻酸钠中的至少一种。在一些实施例中，第一导电剂与第一粘结剂的质量比为1:(0.1至1)。在一些实施例中，第二导电剂与所述第二粘结剂的质量比为1:(0.1至1)。在一些实施例中，活性材料层与第二层之间的粘结力为10N/m至50N/m。
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在集流体和活性材料层之间设置两个涂层，并且使第一层的平均孔径小于第二层的平均孔径，增大了集流体与活性材料层的接触面积，进而提高极片粘结力，缩短电荷传递距离，减小极片内阻。
附图说明
图1示出了本申请的一些实施例的极片在厚度方向和宽度方向限定的平面截取的截面图。
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，电化学装置包括电极组件，电极组件包括正极极片、负极极片以及设置在正极极片和负极极片之间的隔离膜。在一些实施例中，如图1所示，正极极片或负极极片包括集流体101、第一层102、第二层103和活性材料层104，第一层102位于集流体101和第二层103之间，第二层103位于第一层102和活性材料层104之间。为了简单的目的，下面以正极极片为例进行说明，应该理解，负极极片可以采用相应的结构。应该理解，第一层102、第二层103和活性材料层104可以位于集流体101的一侧上，也可以均位于集流体101的两侧上。
在一些实施例中，活性材料层104包括活性材料，例如，正极活性材料。在一些实施例中，第一层102的平均孔径小于第二层103的平均孔径。由于第一层102相对于第二层103更靠近集流体101，在第一层102的平均孔径小于第二层103的平均孔径时，有利于增强集流体101与第一层102的接触。 另外，不同孔径的第一层102和第二层103的组合，增大了活性材料层104、第二层103、第一层102和集流体101之间的接触面积，增大接触面积可提高极片的粘结力以及缩短电子传递途径，减小极片的电阻。
在一些实施例中，第一层102的平均孔径为0.01μm至0.1μm，第二层103的平均孔径为0.1μm至50μm。第二层103的平均孔径与活性材料的粒径相近，有利于活性材料与第二层103的匹配接触。另外，第一层102的平均孔径为0.01μm至0.1μm，比第二层103的平均孔径更小，有利于增强集流体101与第一层102的接触。如果第一层102的平均孔径过大，则不利于第一层102与集流体101的粘结力的提升。如果第二层103的平均孔径过大，则不利于电化学装置的能量密度的提升。
在一些实施例中，第一层102和第二层103的平均孔径可以采用以下方法进行测试：采用扫描电子显微镜测试经截面抛光处理后的涂层截面，随机选取涂层中的100个孔，将其中孔径最大的25个孔以及孔径最小的25个孔剔除，计算剩余50个孔的孔径均值即为该涂层的平均孔径。当然，这仅是示例性的，还可以采用其他合适的平均孔径测试方法。
在一些实施例中，第一层102的平均厚度为0.1μm至10μm，第二层103的平均厚度为0.1μm至10μm。如果第一层102和/或第二层103的厚度过小，则不利于极片的粘结力的提高。如果第一层102和/或第二层103的厚度过大，则不利于电化学装置的能量密度的提升。在一些实施例中，第一层102的平均厚度为0.1μm至5μm，第二层103的平均厚度为0.1μm至5μm。在一些实施例中，第一层102的平均厚度为0.1μm至3μm，第二层103的平均厚度为0.1μm至3μm。
在一些实施例中，第一层102和第二层103的平均厚度可以采用以下方法进行测试：采用扫描电子显微镜测试经截面抛光处理后的涂层截面，做垂直于集流体平面的直线，垂线与涂层上下边缘相交于两点，量取两点间距离为涂层厚度，依照上述方法随机选取涂层的100个厚度值，将其中数值最大的25个以及数值最小的25个厚度值剔除，计算剩余50个厚度值的均值即为该涂层的平均厚度。当然，这仅是示例性的，还可以采用其他合适的平均厚度测试方法。
在一些实施例中，第一层102包括第一导电剂和第一粘结剂，第二层103包括第二导电剂和第二粘结剂。通过采用导电剂和粘结力，这样的组合形成的第一层102和第二层103与或活性材料层104的相容性更好，可以提升第二层103与活性材料层104之间以及集流体101与第一层102之间的粘结力。另外，导电剂的存在也可以降低电子传递电阻，进而降低极片电阻。
在一些实施例中，第一导电剂和第二导电剂各自独立地包括炭黑、碳纳米管、导电石墨、乙炔黑、科琴黑或石墨烯中的至少一种。在一些实施例中，第一粘结剂和第二粘结剂各自独立地包括丙烯酸树脂、丁苯橡胶、聚丙烯酸类、羧甲基纤维素钠或海藻酸钠中的至少一种。在一些实施例中，第一导电剂与第一粘结剂的质量比为1:(0.1至1)。在一些实施例中，第二导电剂与第二粘结剂的质量比为1:(0.1至1)。通过采用这样的质量比，在确保集流体101、第一层102、第二层103和活性材料层104之间的粘结力的基础上，有助于降低第一层102和第二层103的电子传递电阻，进而降低极片电阻。如果第一导电剂的质量含量太小，则会不利地影响第一层102的导电性，进而不利于极片电阻的降低。如果第一导电剂的质量含量太大，则由于第一导电剂自身的粘结性能稍弱，过量的第一导电剂会不利地影响第一层102的粘结性能的发挥。同样地，如果第二导电剂的质量含量太小，则会不利地影响第二层103的导电性，进而不利于极片电阻的降低。如果第二导电剂的质量含量太大，则由于第二导电剂自身的粘结性能稍弱，过量的第二导电剂会不利地影响第二层103的粘结性能的发挥。
在一些实施例中，活性材料层104与第二层103之间的粘结力为10N/m至50N/m。通过达到这样的粘结力，改善了极片整体的粘结力。通常地，极片中的活性材料层104和第二层103之间的粘结较为脆弱，因此可以将活性材料层104与第二层103之间的平均粘结力视为极片的整体粘结力。在一些实施例中，活性材料层104与第二层103之间的粘结力可以通过以下方法进行测试：将双面胶粘接至需要测试的尺寸为15*60mm的极片任意一面，并用压辊压实，使压辊与极片完全贴合；将上述双面胶的另外一面粘贴于不锈钢板表面，采用拉力机测试，将不锈钢一端固定于拉力机下方夹具，将试样一端反向弯曲，弯曲角度为90°，试样弯曲末端固定于拉力机上方夹具，调整试样角度，保证试样一端与另一端处于垂直位置，然后以50mm/min的速度拉 伸试样，直到试样全部从不锈钢板剥离，记录过程中的位移和作用力，受力平衡时的力即为极片的粘结力；随机测试10个样品，取粘结力的平均值即为粘结力。当然，这仅是示例性的，还可以采用其他合适的粘结力测试方法。
在一些实施例中，极片的平均电阻为0.5Ohm至5Ohm。如此，可以获得电化学装置的良好的电性能。在一些实施例中，极片的平均电阻可以通过以下方法进行测试：采用两探针电阻测试仪进行测试，将两探针间压力调节至0.4t，将待测试极片放在探针中间，运行仪器，过5秒后记录电阻测试仪所示的内阻值，按上述方法测试20个不同的点，计算所记录的20个内阻的平均值即为极片的平均电阻。当然，这仅是示例性的，还可以采用其他合适的电阻测试方法。
在一些实施例中，电池的内阻(IMP)可以为1mOhm至10mOhm。如此，可以获得电化学装置的良好的电性能。在一些实施例中，电池的IMP可以通过以下方法进行测试：采用手动OCV/IMP电压内阻测试机进行测试，将待测试电池放在测试机上料位，运行仪器，过5秒后记录内阻测试仪所示的IMP值，按上述方法测试20个不同的电池，计算所记录的20个电池内阻的平均值即为该极片对应电池的IMP。当然，这仅是示例性的，还可以采用其他合适的内阻测试方法。
在一些实施例中，第一层102和第二层103可以通过静电纺丝方法形成。通过采用静电纺丝方法，可以更好地控制第一层102和第二层103的孔径尺寸和厚度。
在一些实施例中，在正极极片包括上述结构时，活性材料层104为正极活性材料层，并且包括正极活性材料。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，正极活性材料层还可以包括粘结剂，正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，正极活性材料层中的正极活性材料、导电剂和粘结剂的质量比可以为(80至99)：(0.1至10)：(0.1至10)。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，正极极片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，正极极片的集流体可以采用Al箔，当然，也可以采用本领域常用的其他集流体。在一些实施例中，正极极片的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极片的集流体的部分区域上。
在一些实施例中，当负极极片包括上述结构时，活性材料层104为负极活性材料层。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(80至98)：(0.1至10)：(0.1至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，负极极片的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，电化学装置的正极极片和/或负极极片可以是卷绕或堆叠式形成的多层结构，也可以是单层正极极片、隔离膜、单层负极极片叠加的单层结构。
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，将正极极片、隔离膜、负极极片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。为了简单的目的，下面仅以正极极片包括第一层和第二层作为示例。
实施例1
正极极片的制备：采用铝箔作为正极极片的集流体，在铝箔表面均匀的涂布导电涂层浆料，具体地：将乙炔黑、石墨烯与丙烯酸树脂以1：0.05：0.8的重量比混合后搅拌均匀，得到导电涂层浆料；将导电涂层浆料装进静电纺丝机器中，调节静电纺丝机器电压10kV，浆料推速为0.5mL/h，静电纺丝喷头与集流体的距离为15cm；将导电涂层浆料喷涂到集流体后，110℃烘烤10min，得到具有0.01μm平均孔径，厚度为0.1μm的带有第一层的集流体。然后调节静电纺丝机器电压8kV，浆料推速为2mL/h，静电纺丝喷头与集流体的距离为15cm，进行第二次喷涂；将第二次喷涂后的集流体在110℃环境中烘烤10min，得到平均孔径为0.5μm，厚度为0.5μm的第二层的集流体。
将正极活性材料磷酸铁锂、导电剂导电炭黑、粘结剂聚丙烯酸按重量比98.2：0.5：1.3的比例溶于N-甲基吡咯烷酮(NMP)溶液中，形成正极浆料，将正极浆料以200μm的厚度涂覆第二层上，在110℃环境中烘烤10min，经过冷压、裁切后得到正极极片。
负极极片的制备：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厚度铜箔作为负极极片的集流体，将负极浆料涂覆于负极极片的集流体上，干燥，裁切后得到负极极片。
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)：碳酸丙烯酯(PC)＝50：50，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：将正极极片、隔离膜、负极极片按顺序依次叠好，使隔离膜处于正极极片和负极极片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的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。
表1示出了实施例1至12和对比例1至3的各个参数和评估结果。在实施例2至12以及对比例1至3中，第一层的平均孔径与实施例1不同，并且实施例4至7、9至12和对比例1至2中的第二层的平均孔径与实施例1不同，其他参数与实施例1相同。在对比例3中，正极极片中未形成第二层，且第一层的厚度为0.05μm。
表1
Figure PCTCN2022072438-appb-000001
其中“/”表示没有该层。
通过比较实施例1至3和对比例3可知，通过在集流体和活性材料层之间形成两个层，相对于对比例3中的一个层，极片的平均电阻显著减小，极片的粘结力显著增大，并且电化学装置的内阻IMP变化不大。
通过比较实施例1至3和对比例1可知，在第一层的平均孔径小于第二层的平均孔径时，极片的平均电阻减小，并且极片的平均粘结力增大，电化学装置的内阻也存在一定的减小。
通过比较实施例1至3、8至10、12可知，随着第一层的平均孔径的增大，极片的平均电阻先减小后增大，极片的平均粘结力先增大后减小，电化学装置的内阻有一定的增大的趋势。另外，第一层的平均孔径不宜过小，否则极片的粘结力显著降低。另外，如果第一层的平均孔径过大，极片的平均电阻和电化学装置的内阻会增大。
通过比较实施例4至7、11和对比例2可知，随着第二层的平均孔径的增大，极片的平均电阻有增大的趋势，极片的粘结力先增大后减小，电化学装置的内阻有增大的趋势。因此，第二层的平均孔径不宜过大。如果第二层的平均孔径过大，则极片的平均电阻和电化学装置的内阻增大，而极片的粘结力减小。另外，如果第二层的平均孔径太小，则极片的粘结力显著减小。
表2示出了实施例13至31的各个参数和评估结果。其中，在实施例13至31中，第一层的平均孔径为0.05μm，第二层的平均孔径为9μm。在实施例13至31中，除了第一层和第二层的厚度、导电剂成分和含量、粘结剂的成分和含量与实施例1不同之外，其他参数参见实施例1。
表2
Figure PCTCN2022072438-appb-000002
Figure PCTCN2022072438-appb-000003
通过比较实施例13至16可知，随着第一层的厚度的增大，极片的平均电阻有增大的趋势，极片的粘结力先增大后减小，电化学装置的内阻IMP不断增大。
通过比较实施例17至19可知，随着第二层的厚度的增大，极片的平均电阻有增大的趋势，极片的粘结力先增大后减小，电化学装置的内阻IMP不断增大。
通过比较实施例20至24可知，在第一层中采用不同的导电剂和粘结剂，均能改善极片的平均电阻、极片的粘结力和电化学装置的内阻IMP。
通过比较实施例25至27可知，随着第一层中的导电剂与粘结剂的质量比的减小，极片的平均电阻有增大的趋势，极片的粘结力有增大的趋势，电化学装置的内阻IMP先减小后增大。
通过比较实施例28至29可知，在第二层中采用不同的导电剂和粘结剂，均能改善极片的平均电阻、极片的粘结力和电化学装置的内阻IMP。
通过比较实施例28、30至31可知，随着第二层中的导电剂与粘结剂的质量比的减小，极片的平均电阻有增大的趋势，极片的粘结力有增大的趋势，电化学装置的内阻IMP先减小后增大。
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 (10)

  1. 一种电化学装置，其包括：
    正极极片；
    负极极片；
    隔离膜，位于所述正极极片和所述负极极片之间；
    其中，所述正极极片或所述负极极片包括集流体、第一层、第二层和活性材料层，其中，所述第一层位于所述集流体和所述第二层之间，所述第二层位于所述第一层和所述活性材料层之间，所述第一层的平均孔径小于所述第二层的平均孔径。
  2. 根据权利要求1所述的电化学装置，其中，所述第一层的平均孔径为0.01μm至0.1μm，所述第二层的平均孔径为0.1μm至50μm。
  3. 根据权利要求1所述的电化学装置，其中，所述第一层的平均厚度为0.1μm至10μm，所述第二层的平均厚度为0.1μm至10μm。
  4. 根据权利要求1所述的电化学装置，其中，所述第一层包括第一导电剂和第一粘结剂，所述第二层包括第二导电剂和第二粘结剂。
  5. 根据权利要求4所述的电化学装置，其中，所述第一导电剂和所述第二导电剂各自独立地包括炭黑、碳纳米管、导电石墨、乙炔黑、科琴黑或石墨烯中的至少一种。
  6. 根据权利要求4所述的电化学装置，其中，所述第一粘结剂和所述第二粘结剂各自独立地包括丙烯酸树脂、丁苯橡胶、聚丙烯酸类、羧甲基纤维素钠或海藻酸钠中的至少一种。
  7. 根据权利要求4所述的电化学装置，其中，所述第一导电剂与所述第一粘结剂的质量比为1:(0.1至1)。
  8. 根据权利要求4所述的电化学装置，其中，所述第二导电剂与所述第二粘结剂的质量比为1:(0.1至1)。
  9. 根据权利要求1所述的电化学装置，其中，所述活性材料层与所述第二层之间的粘结力为10N/m至50N/m。
  10. 一种电子装置，包括根据权利要求1至9中任一项所述的电化学装置。
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