WO2022110050A1 - 一种电化学装置和电子装置 - Google Patents

一种电化学装置和电子装置 Download PDF

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Publication number
WO2022110050A1
WO2022110050A1 PCT/CN2020/132394 CN2020132394W WO2022110050A1 WO 2022110050 A1 WO2022110050 A1 WO 2022110050A1 CN 2020132394 W CN2020132394 W CN 2020132394W WO 2022110050 A1 WO2022110050 A1 WO 2022110050A1
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Prior art keywords
insulating layer
electrochemical device
binder
leveling agent
present application
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PCT/CN2020/132394
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English (en)
French (fr)
Inventor
刘晓欠
王可飞
韩冬冬
刘胜奇
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东莞新能源科技有限公司
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Priority to CN202080024068.7A priority Critical patent/CN113632273B/zh
Priority to PCT/CN2020/132394 priority patent/WO2022110050A1/zh
Publication of WO2022110050A1 publication Critical patent/WO2022110050A1/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
    • H01M10/052—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
    • H01M10/04—Construction or manufacture in general
    • 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
    • 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
    • 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 technical field of electrochemistry, and in particular, to an electrochemical device and an electronic device.
  • Lithium-ion batteries have the characteristics of large specific energy, high operating voltage, low self-discharge rate, small size and light weight, and are widely used in various fields such as electrical energy storage, portable electronic devices and electric vehicles.
  • Lithium-ion batteries usually include a positive electrode, a negative electrode, and a separator, and the separator is located between the positive electrode and the negative electrode.
  • the positive electrode usually includes a current collector, an active material layer and an insulating layer, wherein the insulating layer is usually provided on the surface of the current collector where the active material layer is not provided, so as to improve the overall insulating performance of the positive electrode.
  • the inventor's research found that when the insulating layer is coated on the surface of the current collector, the crater-like protrusions shown in Fig. 1 are often formed. performance of lithium-ion batteries.
  • the purpose of the present application is to provide an electrochemical device and an electronic device to reduce or eliminate the crater-like protrusions in the insulating layer, thereby improving the performance of the electrochemical device.
  • the present application is explained by taking a lithium ion battery as an example of an electrochemical device, but the electrochemical device of the present application is not limited to a lithium ion battery.
  • a first aspect of the present application provides an electrochemical device, which includes a positive electrode, the positive electrode includes a current collector, and the current collector includes a coated area provided with an active material and an uncoated area without an active material; the uncoated area at least Parts are provided with an insulating layer, the insulating layer includes a binder, inorganic particles and a leveling agent, and the number of crater-like protrusions in the insulating layer is 0/cm 2 to 0.25/cm 2 .
  • the area where the active material is provided on the surface of the current collector of the positive electrode may be referred to as a coated area, and the area where the active material is not provided on the surface of the current collector is referred to as an uncoated area.
  • An insulating layer may be provided at least partially in the above-mentioned uncoated area, and different setting methods may be adopted, for example, it may include but not limited to: disposing the insulating layer on both sides of the electrode along the length direction, and disposing the insulating layer on the side of the electrode. On the start end side, the insulating layer is provided on the end end side of the electrode.
  • the above setting methods can be used individually or in combination.
  • the starting end and the ending end may refer to the starting end and ending end of the winding structure in the lithium ion battery of the winding structure.
  • the said crater-like protrusion presents a convex shape around the middle depression, which may be caused by the influence of the component content of the insulating layer slurry during the formation of the insulating layer.
  • the adhesion between them is affected.
  • the positive electrode of the present application includes a binder, inorganic particles and a leveling agent, and the number of crater-like protrusions is 0/cm 2 to 0.25/cm 2 , which can make the insulating layer have higher flatness and improve the The adhesion between the insulating layer and the current collector improves the safety performance of the lithium-ion battery.
  • the difference between the maximum thickness and the minimum thickness of the insulating layer is not more than 3 ⁇ m.
  • the difference between the maximum thickness and the minimum thickness of the insulating layer is not more than 3 ⁇ m.
  • the leveling agent is a polymer with a molecular weight of not higher than 50,000.
  • olefin polymers, siloxane polymers, alkenoate polymers, alcohol polymers or ether polymers having a molecular weight of not higher than 50,000.
  • the leveling agent can interact with the binder to improve the leveling property of the insulating layer paste, so that the crater-like protrusions are leveled, thereby eliminating or reducing insulation The number of crater-like bulges in the layer.
  • the leveling agent may include at least one of oxygen-containing propylene olefin polymers, silicone polymers, acrylate polymers, acryl alcohol polymers, or glycol ether polymers, the above The molecular weight of the leveling agent may also be not higher than 50,000. In one embodiment of the present application, the leveling agent may include at least one of polyethoxypropoxypropene, polysiloxane, polymethyl acrylate or polyacryl alcohol or poly(ethylene glycol), the above The molecular weight of the leveling agent may also be not higher than 50,000.
  • the coverage of the insulating layer is not less than 95%.
  • the coverage of the insulating layer covering the uncoated area is not less than 95%.
  • the weight average molecular weight of the binder is 100,000 to 2,000,000, preferably 300,000 to 800,000.
  • the leveling agent can interact with the binder to improve the leveling property of the insulating layer slurry, so that the crater-like protrusions flow. level, thereby reducing or eliminating the number of crater-like protrusions in the insulation.
  • the binder may include at least one of a copolymer of propylene derivatives, polyacrylate, acrylonitrile multipolymer or carboxymethyl cellulose salt.
  • the addition of the binder can improve the viscosity of the insulating layer, thereby improving the adhesion between the insulating layer and the current collector.
  • the binder may include a polymer formed by polymerizing at least one monomer of acrylonitrile, acrylate, acrylamide, and acrylate.
  • the binder may comprise a polymer formed by polymerizing at least one monomer of acrylonitrile, acrylate and acrylamide.
  • the binder of the present application can be a water-based binder, wherein the metal ions in the acrylate can replace part of the hydrogen ions, thereby increasing the hydrophilicity of the binder and reducing the swelling of the binder in the electrolyte , to maintain high adhesion.
  • the metal ions in the acrylate can replace part of the hydrogen ions, thereby increasing the hydrophilicity of the binder and reducing the swelling of the binder in the electrolyte , to maintain high adhesion.
  • hydrogen ions easily obtain electrons to form hydrogen gas, when the hydrogen ions are reduced, it can also prevent the flatulence problem of lithium-ion batteries caused by too many hydrogen ions.
  • the mass percentage content of acrylonitrile is 25% to 70%
  • the mass backup content of acrylate is 10% to 60%
  • the mass percentage of acrylamide is The content is 10% to 60%
  • the mass percentage content of acrylate is 0% to 10%.
  • the inorganic particles include at least one of boehmite, diaspore, alumina, barium sulfate, calcium sulfate or calcium silicate, preferably boehmite and alumina at least one.
  • the addition of inorganic particles can improve the strength and insulating properties of the insulating layer.
  • the mass percentage content of the leveling agent is 0.1% to 5%
  • the mass percentage content of the binder is 2% to 50%
  • the content of the inorganic particles The mass percentage is 50% to 98%.
  • the thickness of the insulating layer is 1 ⁇ m to 10 ⁇ m.
  • the thickness of the insulating layer when the thickness of the insulating layer is too low, such as less than 1 ⁇ m, the strength of the insulating layer is too low, and the insulating performance is affected; when the thickness of the insulating layer is too high, such as higher than 10 ⁇ m, the relative content of the active material in the positive electrode decrease, affecting the energy density of lithium-ion batteries.
  • the insulating layer can have good strength and insulating properties.
  • the Dv99 of the inorganic particles is 0.01 ⁇ m to 10 ⁇ m, preferably 1 ⁇ m to 10 ⁇ m.
  • the flatness of the insulating layer can be improved. It is advisable that the Dv99 of the inorganic particles does not exceed the thickness of the insulating layer, otherwise the aluminum foil will be easily stabbed during the cold pressing process, resulting in uneven spots exceeding the thickness of the target insulating layer.
  • the adhesive force between the insulating layer and the current collector is not less than 201 N/m, it can be seen that the insulating layer and the current collector of the present application have excellent adhesive properties, thereby improving the lithium ion Safety performance of ion batteries.
  • the preparation method of the binder of the present application is not particularly limited, and a preparation method known to those skilled in the art can be adopted, for example, the following preparation method can be adopted:
  • Distilled water was added to the reactor, stirring was started, and after nitrogen was introduced to remove oxygen, at least one of the above-mentioned components such as acrylonitrile, acrylate, acrylamide and acrylate was added in different mass ratios, and heated to 65 °C under an inert atmosphere. °C and constant temperature, then add an initiator to initiate the reaction, and the reaction ends after about 20 hours.
  • the initiator in the present application there is no particular limitation on the initiator in the present application, as long as it can initiate the polymerization of the monomer, for example, it can be a 20% ammonium persulfate solution.
  • the added amounts of distilled water and initiator in the present application there are no particular restrictions on the added amounts of distilled water and initiator in the present application, as long as the added monomers can be guaranteed to undergo a polymerization reaction.
  • alkali solution can also be added to the reacted precipitate for neutralization, so that the pH value is 6.5-9.
  • the reaction product can also be filtered, washed, dried, pulverized, sieved and the like.
  • the positive electrode of the present application may have an active material layer on one surface thereof, or may have an active material layer on both surfaces thereof.
  • the insulating layer of the present application may be provided on at least one surface of the positive electrode, for example, the insulating layer may be provided on one surface of the positive electrode, or may be provided on both surfaces of the positive electrode.
  • the positive electrode current collector is not particularly limited, and can be any positive electrode current collector known in the art, such as aluminum foil, aluminum alloy foil, or composite current collector.
  • the positive electrode active material layer includes a positive electrode active material.
  • the positive electrode active material is not particularly limited, and any positive electrode active material known in the art can be used. At least one of lithium, lithium iron phosphate, lithium-rich manganese-based material, lithium cobaltate, lithium manganate, lithium iron manganese phosphate, or lithium titanate.
  • the negative electrode in the present application is not particularly limited as long as the purpose of the present application can be achieved.
  • the negative electrode typically includes a negative electrode current collector and a negative electrode active material layer.
  • the negative electrode current collector is not particularly limited, and any negative electrode current collector known in the art can be used, such as copper foil, aluminum foil, aluminum alloy foil, and composite current collector.
  • the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material is not particularly limited, and any negative electrode active material known in the art can be used.
  • at least one of artificial graphite, natural graphite, mesocarbon microspheres, soft carbon, hard carbon, silicon, silicon carbon, lithium titanate, and the like may be included.
  • the lithium ion battery of the present application further includes an electrolyte, and the electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolyte, and the electrolyte includes a lithium salt and a non-aqueous solvent.
  • the lithium salt is selected from LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2.
  • LiPF 6 can be chosen as the lithium salt because it can give high ionic conductivity and improve cycle characteristics.
  • the non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof.
  • the above-mentioned carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof.
  • Examples of the above-mentioned chain carbonate compound are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), carbonic acid Methyl ethyl ester (MEC) and combinations thereof.
  • Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), and combinations thereof.
  • fluorocarbonate compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Ethyl carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-dicarbonate Fluoro-1-methylethylene, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof.
  • FEC fluoroethylene carbonate
  • 1,2-difluoroethylene carbonate 1,1-difluoroethylene carbonate
  • 1,1,2-trifluoroethylene carbonate Ethyl carbonate 1,1,2,2-tetrafluoroethylene carbonate
  • 1-fluoro-2-methylethylene carbonate 1-fluoro-1-methylethylene carbonate
  • 1,2-dicarbonate Fluoro-1-methylethylene 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethyl
  • carboxylate compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone , caprolactone, valerolactone, mevalonolactone, caprolactone, and combinations thereof.
  • ether compounds examples include dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethyl ether Oxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.
  • Examples of the above-mentioned other organic solvents are dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, Formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters and combinations thereof.
  • a second aspect of the present application provides an electronic device, including the electrochemical device described in the first aspect.
  • 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.
  • an electrochemical device can be manufactured by the following process: overlapping the positive electrode and the negative electrode through a separator, and putting them into a case after winding, folding, etc. as required, injecting the electrolyte into the case and sealing, the separator used therein The above-mentioned separator provided in this application.
  • an overcurrent preventing element, a guide plate, etc. may be placed in the case to prevent pressure rise and overcharge and discharge inside the electrochemical device.
  • the present application provides an electrochemical device and an electronic device, which include a positive electrode, the positive electrode includes a current collector, and the current collector includes a coated area provided with an active material and an uncoated area without an active material. At least a part of the insulating layer is provided, and the insulating layer includes a binder, inorganic particles and a leveling agent, so that the number of crater-like protrusions in the insulating layer is 0/cm 2 to 0.25/cm 2 , which eliminates or reduces the insulation The number of crater-like protrusions in the layer can make the insulating layer and the current collector have good adhesion, thereby improving the safety performance of the electrochemical device.
  • Fig. 1 is the crater-shaped protrusion formed on the surface of the existing insulating layer
  • FIG. 2 is a schematic structural diagram of a positive pole piece according to an embodiment of the application.
  • 3a is a schematic structural diagram of a positive electrode plate according to another embodiment of the present application.
  • 3b is a schematic structural diagram of a positive electrode plate according to still another embodiment of the present application.
  • 3c is a schematic structural diagram of a positive electrode plate according to still another embodiment of the present application.
  • FIG. 4 is a schematic structural diagram of a positive pole piece according to another embodiment of the application.
  • FIG. 5 is an SEM image of one of the crater-shaped protrusions in the existing insulating layer
  • FIG. 6 is a schematic diagram showing the relationship between the adhesion force and the stroke in the adhesion force test.
  • FIG. 2 shows a schematic structural diagram (top view) of a positive electrode piece in an embodiment of the present application.
  • the positive electrode piece is usually rectangular.
  • the coverage area that is, the area where the active material layer 1 is not provided, and the current collector 3 is exposed in the uncoated area.
  • the insulating layer 2 can be disposed on the uncoated area, and specifically can be disposed on both sides of the positive electrode along the length direction.
  • the positive electrode can also be arranged only on one side of the positive electrode along the length direction.
  • Figures 3a-3c respectively show the structural schematic diagrams (top views) of the positive pole pieces in the other three embodiments of the present application.
  • the insulating layer 2 can be arranged on the starting end side and the ending end side of the positive electrode piece at the same time, or it can be arranged on one of the starting end side and the ending end side of the positive electrode piece as shown in FIG. 3b or FIG. 3c.
  • FIG. 4 shows a schematic structural diagram (top view) of a positive electrode piece in another embodiment of the present application. There may be uncoated areas on both sides of the positive electrode piece along the length direction, as well as at the starting end and the ending end. As shown in FIG. 4 , the insulating layers 2 can be simultaneously disposed on both sides of the positive electrode along the length direction, as well as on the starting end and the ending end.
  • Fig. 5 shows a SEM (scanning electron microscope) image of one of the crater-shaped protrusions in the existing insulating layer. It can be seen from Fig. 5 that the crater-shaped protrusion has a morphology of protrusions around it and a depression in the middle. Affects the thickness uniformity of the insulating layer.
  • FIG. 6 shows the relationship between the adhesion force and the stroke in the adhesion force test.
  • N the number of crater-like protrusions in the insulating layer of the pole piece sample in 1) by the naked eye, CCD microscope or SEM, denoted as N;
  • Binder weight average molecular weight test :
  • the weight average molecular weight of the binder in the insulating layer was tested by gel permeation chromatography (GPC).
  • the weight-average molecular weight refers to a molecular weight that is statistically averaged by mass.
  • the insulating layer at one end of the sample is adhered to the steel plate by double-sided tape, and the adhesion length is not less than 40mm;
  • the pole piece sample is placed in the chuck through a connector or directly clamped, wherein the part of the sample that is pulled up and the steel plate have an included angle of 90° in space.
  • the clip pulls the pole piece at a speed of 5mm/min to separate the insulating layer from the current collector, and finally the average value of the tensile force in the stable area is recorded as the bonding force between the insulating layer and the current collector.
  • the ratio of the standard deviation to the average value of the adhesion data in the above-mentioned plateau area does not exceed 10%.
  • Dv99 represents the particle size at which the volume-based particle size distribution of the inorganic particles reaches 99% by volume from the small particle size side.
  • the lithium-ion battery to be tested with a constant current of 0.05C to a voltage of 4.45V (that is, full charge voltage), and then charge it with a constant voltage of 4.45V to a current of 0.025C (cut-off current), so that the lithium-ion battery is fully charged.
  • Charge state record the appearance of the lithium-ion battery before the test.
  • the battery is subjected to a piercing test in an environment of 25 ⁇ 3°C.
  • the diameter of the steel nail is 4mm
  • the piercing speed is 30mm/s
  • the piercing position is located on the side of the lithium-ion battery.
  • the test is carried out for 3.5min or the surface temperature of the electrode assembly drops to 50°C.
  • Distilled water was added to the reaction kettle and stirring was started. After 2 hours of deoxygenation by introducing nitrogen into the reaction kettle, the following monomers were added to the reaction kettle in a mass ratio of 45:45:10: acrylonitrile, sodium acrylate and acrylamide, and heated to 65 °C under an inert atmosphere. °C and keep a constant temperature, then add 20% ammonium persulfate solution as an initiator to start the reaction, take out the precipitate after 22 hours of reaction, add alkaline solution to neutralize the pH to 6.5. Among them, the mass ratio between distilled water, monomer and initiator is 89.5:10:0.5. After the reaction, the reaction product is filtered, washed, dried, pulverized, sieved and the like to obtain a binder.
  • the weight-average molecular weight of the leveling agent is 20,000
  • the weight-average molecular weight of the binder is 500,000
  • the Dv99 of the inorganic particles is 3 ⁇ m.
  • the positive active material lithium iron phosphate, PVDF, conductive carbon black, and carbon nanotubes are mixed in a mass ratio of 96.8:2:0.7:0.5, and then N-methylpyrrolidone (NMP) is added as a solvent to prepare a solid content of 75%.
  • NMP N-methylpyrrolidone
  • Slurry A stir well.
  • the slurry A is uniformly coated on one surface of a current collector aluminum foil with a thickness of 12 ⁇ m, and dried at 90° C. to obtain a first active layer with a thickness of 50 ⁇ m;
  • the prepared insulating layer slurry was coated on the surface of the aluminum foil where the first active layer was not coated to obtain an insulating layer with a thickness of 6 ⁇ m, wherein the binder accounted for 15% of the total mass of the insulating layer, and the inorganic
  • the mass percentage of the particles in the total mass of the insulating layer is 84.9%, and the mass percentage of the leveling agent in the total mass of the insulating layer is 0.10%;
  • the positive active material lithium cobaltate (LCO), polyvinylidene fluoride (PVDF), conductive carbon black, and carbon nanotubes were mixed in a mass ratio of 97:1.5:0.8:0.7, and then N-methylpyrrolidone (NMP) was added as Solvent, prepared into slurry B with a solid content of 75%, and stirred evenly.
  • the slurry B was uniformly coated on the first active layer, and dried at 90° C. to obtain a second active layer with a thickness of 50 ⁇ m.
  • the first active layer and the second active layer together constitute the positive active material layer of the positive electrode sheet.
  • the above steps are repeated on the other surface of the positive electrode sheet to obtain a positive electrode sheet coated with a positive electrode active material layer on both sides. Cut the positive pole piece into a size of 74mm ⁇ 867mm and weld the tabs for later use.
  • the negative electrode active material graphite, styrene-butadiene rubber, and sodium carboxymethyl cellulose are mixed in a weight ratio of 97.5:1.3:1.2, and deionized water is added as a solvent to prepare a slurry with a solid content of 70%, and stir evenly.
  • the slurry was uniformly coated on the negative electrode current collector copper foil, dried at 110°C, and cold pressed to obtain a negative electrode pole piece with a negative electrode active material layer thickness of 150 ⁇ m on one side coated with a negative electrode active material layer.
  • these steps are also completed on the back side of the negative electrode pole piece by the same method, that is, the negative pole piece with double-sided coating is obtained.
  • the negative pole pieces are cut into sheets with a size of 76mm ⁇ 851mm, and the tabs are welded for use.
  • Alumina and polyacrylate were mixed in a mass ratio of 90:10 and dissolved in deionized water to form a ceramic slurry with a solids content of 50%. Then, the ceramic slurry was uniformly coated on one side of the porous substrate (polyethylene, thickness 7 ⁇ m, average pore size 0.073 ⁇ m, porosity 26%) by gravure coating, and dried to obtain a ceramic coating
  • the bilayer structure with the porous substrate, the thickness of the ceramic coating is 50 ⁇ m.
  • PVDF Polyvinylidene fluoride
  • polyacrylate was mixed in a mass ratio of 96:4 and dissolved in deionized water to form a polymer slurry with a solids content of 50%. Then, the polymer slurry is uniformly coated on both surfaces of the above-mentioned double-layer structure of the ceramic coating layer and the porous substrate by the gravure coating method, and is subjected to drying treatment to obtain a separator, wherein the single layer formed by the polymer slurry is The coating thickness is 2 ⁇ m.
  • the above-prepared positive electrode, separator, and negative electrode are stacked in sequence, so that the separator is in the middle of the positive and negative electrodes for isolation, and the electrode assembly is obtained by winding.
  • the electrode assembly is put into an aluminum-plastic film packaging bag, and the moisture is removed at 80 ° C, the prepared electrolyte is injected, and the lithium ion battery is obtained through vacuum packaging, standing, forming, and shaping.
  • Example 2 The rest is the same as in Example 1, except that in ⁇ Preparation of Positive Electrode Sheet>, the mass percentage of the leveling agent in the total mass of the insulating layer is 1.00%.
  • Example 2 The rest is the same as in Example 1, except that in ⁇ Preparation of Insulation Layer Paste>, the mass percentage of the leveling agent in the total mass of the insulation layer is 2.00%.
  • the mass percentage of the leveling agent in the total mass of the insulating layer is 5.00%, and the thickness of the insulating layer is 10 ⁇ m, the rest is the same as that of Example 1.
  • the leveling agent is selected from polysiloxane, the rest is the same as that of Example 3.
  • the leveling agent is selected from polypropylene alcohol, the rest is the same as that of Example 3.
  • the mass percentage of the leveling agent in the total mass of the insulating layer is 0.18%, and the weight average molecular weight of the leveling agent is 5000, the rest is the same as that of Example 1.
  • the mass percentage of the leveling agent in the total mass of the insulating layer is 0.18%, and the weight-average molecular weight of the leveling agent is 30,000, the rest is the same as Example 1.
  • the mass percentage of the leveling agent in the total mass of the insulating layer is 0.18%, and the weight-average molecular weight of the leveling agent is 50,000, the rest is the same as Example 1.
  • the binder is polymethyl acrylate
  • the weight-average molecular weight of the binder is 50,000
  • the mass percentage of the leveling agent in the total mass of the insulating layer is 0.20%
  • the inorganic particles account for the total mass of the insulating layer.
  • the rest is the same as that of Example 1.
  • the binder is selected from acrylonitrile multipolymer, the rest is the same as that of Example 14.
  • Binder was selected from sodium carboxymethyl cellulose, the rest was the same as that of Example 14.
  • the monomers are acrylamide and sodium acrylate with a mass ratio of 40:60, the mass percentage of the leveling agent in the total mass of the insulating layer is 0.20%, and the binder in the total mass of the insulating layer is 0.20%. Except for the mass percentage of 84.80%, the rest are the same as in Example 1.
  • the monomers were selected from acrylonitrile and acrylamide with a mass ratio of 40:60, the rest were the same as those in Example 19.
  • the monomers are selected from acrylonitrile and sodium acrylate with a mass ratio of 40:60, the rest are the same as those in Example 19.
  • the monomers were selected from acrylonitrile, sodium acrylate, acrylamide and acrylate with a mass ratio of 27:60:10:3, the rest were the same as those in Example 19.
  • Binder> the monomers were selected as acrylonitrile, sodium acrylate and acrylamide with a mass ratio of 30:60:10, the rest were the same as those in Example 19.
  • the monomers were selected from acrylonitrile, sodium acrylate and acrylamide with a mass ratio of 30:10:60, the rest were the same as those in Example 19.
  • the monomers selected are acrylonitrile, sodium acrylate and acrylamide whose mass ratio is 45:10:45, the rest are the same as those in Example 19.
  • the monomers were selected as acrylonitrile, sodium acrylate and acrylamide with a mass ratio of 60:10:30, and the Dv99 of the inorganic particles was 1 ⁇ m, the rest was the same as that of Example 19.
  • Binder> the monomers were selected as acrylonitrile, sodium acrylate and acrylamide with a mass ratio of 70:20:10, the rest were the same as those in Example 19.
  • the monomers are acrylonitrile, sodium acrylate and acrylamide with a mass ratio of 45:10:45, the mass percentage of the binder in the total mass of the insulating layer is 50%, and the inorganic particles The mass percentage of the total mass of the insulating layer is 49.8%, and the leveling agent is the same as Example 1 except that the mass percentage of the total mass of the insulating layer is 0.20%.
  • the mass percentage of the binder in the total mass of the insulating layer is 15%
  • the mass percentage of the inorganic particles in the total mass of the insulating layer is 84.8%
  • the weight-average molecular weight of the binder is It is the same as Example 28 except that it is 100000.
  • the inorganic particles are selected from diaspore, the rest is the same as that of Example 29.
  • Example 29 Except that in ⁇ Preparation of Insulation Layer Paste>, aluminum oxide (Al 2 O 3 ) was selected as the inorganic particles, the rest was the same as that of Example 29.
  • the monomers are selected from acrylamide and sodium acrylate with a mass ratio of 40:60, the rest is the same as that of Example 28.
  • the monomers were selected from acrylamide and sodium acrylate with a mass ratio of 40:60, the rest were the same as those in Example 30.
  • the monomers were selected from acrylamide and sodium acrylate with a mass ratio of 40:60, the rest were the same as those in Example 31.
  • the binder is polyacrylic acid
  • the weight-average molecular weight of the binder is 1,500,000
  • the mass ratio between the binder and the inorganic particles is 12:88.
  • the inorganic particles are the same as in Example 1 except that alumina is selected.
  • Binder> the monomers were selected as acrylonitrile, sodium acrylate and acrylamide with a mass ratio of 10:75:15, the rest were the same as those in Example 23.
  • the monomers were selected from acrylonitrile, sodium acrylate and acrylamide with a mass ratio of 80:5:15, the rest were the same as those in Example 23.
  • the insulating layer of the present application and the positive electrode sheet having the insulating layer of the present application can significantly improve the adhesion between the insulating layer and the current collector, and significantly improve the safety performance of the lithium ion battery.

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Abstract

本申请提供了一种电化学装置和电子装置，电化学装置包括正极，正极包括集流体，集流体包括设置有活性物质的涂覆区和未设置活性物质的未涂覆区；未涂覆区至少部分设置有绝缘层，绝缘层包括粘结剂、无机颗粒和流平剂，绝缘层中的火山口状凸起数量为0个/cm 2至0.25个/cm 2。本申请能够消除或降低了绝缘层中火山口状凸起的数量，并能使绝缘层与集流体之间具有良好的粘结力，从而提高电化学装置的安全性能。

Description

一种电化学装置和电子装置 技术领域
本申请涉及电化学技术领域，具体涉及一种电化学装置和电子装置。
背景技术
锂离子电池具有比能量大、工作电压高、自放电率低、体积小、重量轻等特点，广泛应用于电能储存、便携式电子设备和电动汽车等各个领域。
锂离子电池通常包括正极、负极和隔离膜，隔离膜位于正极和负极之间。正极中通常包含集流体、活性物质层以及绝缘层，其中绝缘层通常设置于集流体表面未设置活性物质层的区域，以提高正极整体的绝缘性能。发明人研究发现，在集流体表面涂布绝缘层时，常会形成图1所示的火山口状凸起，这些火山口状凸起会影响绝缘层与集流体之间的粘结力，进而影响锂离子电池的性能。
发明内容
本申请的目的在于提供一种电化学装置和电子装置，以减少或消除绝缘层中的火山口状凸起，从而提高电化学装置的性能。
需要说明的是，以下内容中，以锂离子电池作为电化学装置的例子来解释本申请，但是本申请的电化学装置并不仅限于锂离子电池。
具体技术方案如下：
本申请的第一方面提供了一种电化学装置，其包括正极，正极包括集流体，集流体包括设置有活性物质的涂覆区和未设置活性物质的未涂覆区；未涂覆区至少部分设置有绝缘层，绝缘层包括粘结剂、无机颗粒和流平剂，绝缘层中的火山口状凸起数量为0个/cm 2至0.25个/cm 2。
本申请的电化学装置中，正极的集流体的表面设置有活性物质的区域可以称为涂覆区，集流体的表面未设置有活性物质的区域称为未涂覆区。可以在上述未涂覆区至少部分设置绝缘层，并且可以采用不同的设置方式，例如可以包括但不限于：将绝缘层设置在电极的沿长度方向上的两侧，将绝缘层设置在电极的起始端侧，将绝缘层设置在电极的收尾端侧。上述设置方式可以单独采用，也可以组合采用。所说的起始端和收尾端可以指在卷绕结构的锂离子电池中，卷绕结构的起始端和收尾端。
所说的火山口状凸起呈现出中间凹陷四周凸起状，可能是在绝缘层形成过程中受绝缘 层浆料的组分含量影响产生的，对绝缘层的平整性以及与绝缘层集流体之间的粘结力均有影响。本申请的正极中包括粘结剂、无机颗粒和流平剂，火山口状凸起数量为0个/cm 2至0.25个/cm 2，能够使绝缘层具有更高的平整性，还能提升绝缘层与集流体之间粘结力，从而提高锂离子电池的安全性能。
在本申请的一种实施方案中，绝缘层最大厚度与最小厚度之差不大于3μm。通过控制绝缘层最大厚度与最小厚度之差不大于3μm，减少或消除了绝缘层中火山口状凸起的数量，并且使绝缘层更加平整，更有利于绝缘层与集流体之间粘结力的提升。
在本申请的一种实施方案中，所述流平剂为分子量不高于50000的聚合物。例如分子量不高于50000的烯烃聚合物、硅氧烷聚合物、烯酸酯聚合物、醇聚合物或醚聚合物。通过控制流平剂的分子量在上述范围内，能够使流平剂与粘结剂相互作用，提高绝缘层浆料的流平性，从而使火山口状的凸起流平，从而消除或降低绝缘层中火山口状凸起的数量。
在本申请的一种实施方案中，流平剂可以包括含氧丙烯烃聚合物、硅氧烷聚合物、丙烯酸酯聚合物、丙烯醇聚合物或乙二醚聚合物中的至少一种，上述流平剂的分子量也可以不高于50000。在本申请的一种实施方案中，流平剂可以包括聚乙氧基丙氧基丙烯烃、聚硅氧烷、聚丙烯酸甲酯或聚丙烯醇或聚乙二醚中的至少一种，上述流平剂的分子量也可以不高于50000。
在本申请的一种实施方案中，所述绝缘层的覆盖度不低于95％。通过控制绝缘层覆盖所述未涂覆区的覆盖度不低于95％，能够使正极具有更高的绝缘性能。
在本申请的一种实施方案中，粘结剂的重均分子量为100000至2000000，优选为300000至800000。不限于任何理论，通过控制粘结剂的重均分子量在上述范围内，能够使流平剂与粘结剂相互作用，提高绝缘层浆料的流平性，从而使火山口状的凸起流平，从而减少或消除绝缘层中火山口状凸起的数量。
在本申请的一种实施方案中，粘结剂可以包括丙烯烃类衍生物的共聚物、聚丙烯酸酯、丙烯腈多元共聚物或羧甲基纤维素盐中的至少一种。粘结剂的加入能够提高绝缘层的粘性，从而提高绝缘层与集流体之间的粘结力。
在本申请的一种实施方案中，粘结剂可以包括丙烯腈、丙烯酸盐、丙烯酰胺和丙烯酸酯中的至少一种单体聚合形成的聚合物。优选地，粘结剂可以包括丙烯腈、丙烯酸盐和丙烯酰胺中的至少一种单体聚合形成的聚合物。
本申请的粘结剂可以是一种水性粘结剂，其中，丙烯酸盐中的金属离子能够取代部分 氢离子，从而增加粘结剂的亲水性，使粘结剂在电解液中溶胀减小，保持较高的粘结力。另外，由于氢离子易得电子而形成氢气，因此当氢离子减少后，还可防止产生因氢离子过多而导致的锂离子电池胀气问题。
在本申请的一种实施方案中，基于聚合物的总质量，丙烯腈的质量百分含量为25％至70％，丙烯酸盐的质量备份含量为10％至60％，丙烯酰胺的质量百分含量为10％至60％，丙烯酸酯的质量百分含量为0％至10％。不限于任何理论，通过控制丙烯腈、丙烯酸盐、丙烯酰胺和丙烯酸酯的质量百分含量在上述范围内，能够得到粘结性良好的粘结剂，从而提高绝缘层与集流体之间的粘结力。
在本申请的一种实施方案中，所述无机颗粒包括勃姆石、水铝石、氧化铝、硫酸钡、硫酸钙或硅酸钙中的至少一种，优选为勃姆石和氧化铝中的至少一种。无机颗粒的加入能够提高绝缘层的强度和绝缘性能。在本申请的一种实施方案中，基于绝缘层的总质量，流平剂的质量百分含量为0.1％至5％，粘结剂的质量百分含量为2％至50％，无机颗粒的质量百分含量为50％至98％。不限于任何理论，通过控制流平剂、粘结剂和无机颗粒的质量百分含量在上述含量范围内，能够减少或消除绝缘层中火山口状凸起的数量，并且使绝缘层更加平整，更有利于绝缘层与集流体之间粘结力的提升。在本申请的一种实施方案中，绝缘层的厚度为1μm至10μm。不限于任何理论，当绝缘层的厚度过低时，例如低于1μm，绝缘层强度过低，绝缘性能受到影响；当绝缘层的厚度过高时，例如高于10μm，正极中活性物质相对含量下降，影响锂离子电池的能量密度。通过控制绝缘层的厚度在上述范围内，能够使绝缘层具有良好的强度和绝缘性能。
在本申请的一种实施方案中，所述无机颗粒的Dv99为0.01μm至10μm，优选为1μm至10μm。不限于任何理论，通过控制无机颗粒的Dv99在上述范围内，能够提高绝缘层的平整度。以无机颗粒的Dv99不超过绝缘层的厚度为宜，否则在冷压过程中易刺伤铝箔，形成凹凸点超出目标绝缘层厚度。在本申请的一种实施方案中，绝缘层与所述集流体之间的粘结力不小于201N/m，可见本申请的绝缘层与集流体之间具有优异的粘结性能，从而提高锂离子电池的安全性能。本申请的粘结剂的制备方法没有特别限制，可以采用本领域技术人员公知的制备方法，例如可以采用如下制备方法：
在反应釜中加入蒸馏水，启动搅拌，通入氮气除氧后，按不同质量比加入丙烯腈、丙烯酸盐、丙烯酰胺和丙烯酸酯等上述组分中的至少一种，在惰性气氛下加热至65℃左右并恒温，然后加入引发剂引发反应，至反应20小时左右后结束。
本申请对引发剂没有特别限制，只要能引发单体聚合即可，例如可以为20％的过硫酸铵溶液。本申请对蒸馏水和引发剂的添加量没有特别限制，只要能保证加入的单体发生聚合反应即可。在反应后，还可以向反应的沉淀物中加入碱液已进行中和，使pH值为6.5～9。还可以对反应产物进行过滤、洗涤、烘干、粉碎、过筛等处理。
本领域技术人员应当理解，本申请的正极可以在其一个表面具有活性物质层，也可以在其两个表面均具有活性物质层。本申请的绝缘层可以设置在正极的至少一个表面，例如，绝缘层可以设置正极的一个表面，也可以设置在正极的两个表面。
本申请的正极中，正极集流体没有特别限制，可以为本领域公知的任何正极集流体，例如铝箔、铝合金箔或复合集流体等。正极活性物质层包括正极活性物质，正极活性物质没有特别限制，可以使用本领域公知的任何正极活性物质，例如，可以包括镍钴锰酸锂(811、622、523、111)、镍钴铝酸锂、磷酸铁锂、富锂锰基材料、钴酸锂、锰酸锂、磷酸锰铁锂或钛酸锂中的至少一种。
本申请中的负极没有特别限制，只要能够实现本申请目的即可。例如，负极通常包含负极集流体和负极活性物质层。其中，负极集流体没有特别限制，可以使用本领域公知的任何负极集流体，例如铜箔、铝箔、铝合金箔以及复合集流体等。负极活性物质层包括负极活性物质，负极活性物质没有特别限制，可以使用本领域公知的任何负极活性物质。例如，可以包括人造石墨、天然石墨、中间相碳微球、软碳、硬碳、硅、硅碳、钛酸锂等中的至少一种。
本申请的锂离子电池还包括电解质，电解质可以是凝胶电解质、固态电解质和电解液中的一种或多种，电解液包括锂盐和非水溶剂。
在本申请一些实施方案中，锂盐选自LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB和二氟硼酸锂中的一种或多种。举例来说，锂盐可以选用LiPF 6，因为它可以给出高的离子导电率并改善循环特性。
非水溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物、其它有机溶剂或它们的组合。
上述碳酸酯化合物可为链状碳酸酯化合物、环状碳酸酯化合物、氟代碳酸酯化合物或其组合。
上述链状碳酸酯化合物的实例为碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸甲乙酯(MEC)及其组合。 环状碳酸酯化合物的实例为碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)、碳酸乙烯基亚乙酯(VEC)及其组合。氟代碳酸酯化合物的实例为碳酸氟代亚乙酯(FEC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯、碳酸三氟甲基亚乙酯及其组合。
上述羧酸酯化合物的实例为甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯、甲瓦龙酸内酯、己内酯及其组合。
上述醚化合物的实例为二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基乙烷、2-甲基四氢呋喃、四氢呋喃及其组合。
上述其它有机溶剂的实例为二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯、和磷酸酯及其组合。
本申请的第二方面提供了一种电子装置，包括上述第一方面所述的电化学装置。
本申请的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，电子装置可以包括，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
电化学装置的制备过程为本领域技术人员所熟知的，本申请没有特别的限制。例如电化学装置可以通过以下过程制造：将正极和负极经由隔离膜重叠，并根据需要将其卷绕、折叠等操作后放入壳体内，将电解液注入壳体并封口，其中所用的隔离膜为本申请提供的上述隔离膜。此外，也可以根据需要将防过电流元件、导板等置于壳体中，从而防止电化学装置内部的压力上升、过充放电。
本申请提供了一种电化学装置和电子装置，其包括正极，正极包括集流体，集流体包括设置有活性物质的涂覆区和未设置活性物质的未涂覆区，通过在未涂覆区至少部分设置绝缘层，且绝缘层包括粘结剂、无机颗粒和流平剂，使绝缘层中的火山口状凸起数量为0 个/cm 2至0.25个/cm 2，消除或降低了绝缘层中火山口状凸起的数量，并能使绝缘层与集流体之间具有良好的粘结力，从而提高电化学装置的安全性能。
附图说明
为了更清楚地说明本申请和现有技术的技术方案，下面对实施例和现有技术中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例。
图1为现有绝缘层表面形成的火山口状凸起；
图2为本申请的一种实施方案的正极极片的结构示意图；
图3a为本申请的另一种实施方案的正极极片的结构示意图；
图3b为本申请的再一种实施方案的正极极片的结构示意图；
图3c为本申请的再一种实施方案的正极极片的结构示意图；
图4为本申请的再一种实施方案的正极极片的结构示意图；
图5为现有绝缘层中其中一火山口状凸起的SEM图像；
图6为在粘结力测试中粘结力与行程之间的关系示意图。
图中，1.活性物质层，2.绝缘层，3.集流体。
具体实施方式
为使本申请的目的、技术方案、及优点更加清楚明白，以下参照附图和实施例，对本申请进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员所获得的所有其他技术方案，都属于本申请保护的范围。
图2示出了本申请一种实施方案中的正极极片的结构示意图(俯视图)，正极极片通常为矩形，如图2所示，正极极片沿长度方向上的两侧可能存在未涂覆区，即未设置活性物质层1的区域，集流体3露出于该未涂覆区。图1中，绝缘层2可以设置于未涂覆区，具体可以设置于正极沿长度方向上的两侧。当然，也可仅设置于正极沿长度方向上的其中一侧。
图3a-3c分别示出了本申请另外三种实施方案中的正极极片的结构示意图(俯视图)，正极极片的起始端和收尾端也可能存在未涂覆区，则如图3a所示，绝缘层2可以同时设置于正极极片的起始端侧和收尾端侧，也可以如图3b或图3c所示，设置于正极极片的起始端侧和收尾端侧的其中一侧。
图4示出了本申请再一种实施方案中的正极极片的结构示意图(俯视图)，正极极片 的沿长度方向上的两侧及起始端和收尾端都可能存在未涂覆区，则如图4所示，绝缘层2可以同时设置于正极的沿长度方向上的两侧及起始端和收尾端。
图5示出了现有绝缘层中其中一个火山口状凸起的SEM(扫描电子显微镜)图像，通过图5可以看出，该火山口状凸起具有四周凸起、中间凹陷的形貌，影响绝缘层的厚度均匀性。
图6示出了在粘结力测试时粘结力与行程之间的关系。
实施例
以下，举出实施例及对比例来对本申请的实施方式进行更具体地说明。各种的试验及评价按照下述的方法进行。另外，只要无特别说明，“份”、“％”为质量基准。
测试方法和设备：
火山口状凸起数量测试：
1)裁切涂有绝缘涂层的极片，得到涂有绝缘层的极片样品，记涂有绝缘层一面的面积为S；
2)通过肉眼、CCD显微镜或SEM观测1)中极片样品的绝缘层中的火山口状凸起的数量，记为N；
3)通过以下表达式计算火山口状凸起的单位面积数量A：A＝N/S，单位为ea/cm 2(个/平方厘米)。
绝缘层厚度差测试：
1)在(25±3)℃的环境下，将涂有绝缘涂层的极片从成品电芯中拆出。用无尘纸拭去极片表面残留的电解液；
2)涂有绝缘层的极片在等离子体下切割，得到其横截面；
3)在SEM下观察2)中得到的极片横截面，并测试单面绝缘涂层的厚度，相邻测试点间隔2～3mm，至少测试15个不同点，记所有测试点的均值为绝缘涂层的厚度。
粘结剂重均分子量测试：
采用凝胶渗透色谱法(GPC)测试绝缘层中的粘结剂的重均分子量。本申请中，重均分子量是指按质量统计平均的分子量。
粘结力测试：
使用高铁拉力机、90°角法测试绝缘层与集流体之间的粘结力：将成品锂离子电池中设置有绝缘层部分的极片裁切为20mm*60mm的条状试样，其长宽值可根据实际情况按比例调整。沿试样的长度方向，将试样一端的绝缘层面通过双面胶粘附在钢板上，其中粘附长度不低于40mm；然后将钢板固定在高铁拉力机的相应位置，拉起试样的未被粘附在钢板上的另一端，通过连接物或直接将极片样品放入夹头内夹紧，其中被拉起的试样部分与钢板在空间上夹角为90°。夹头以5mm/min的速度拉动极片，使绝缘层与集流体分离，最终测得平稳区域的拉力平均值记为绝缘层与集流体之间的粘结力。如图6所示，要求上述平稳区域的粘结力数据的标准差与平均值的比值不超过10％。
覆盖度测试：
1)裁切涂有绝缘涂层的极片，得到涂有绝缘层的极片样品，记涂有绝缘层一面的面积为S1；
2)使用分辨率为0.02μm的CCD显微镜统计1)中极片样品中涂有绝缘层的一面未被绝缘材料覆盖的集流体面积(即漏涂面积)，记为S2；
3)通过以下表达式计算绝缘层的覆盖度B：B＝(S1-S2)/S1×100％。
无机颗粒Dv99测试：
使用激光粒度仪测试无机颗粒的Dv99。Dv99表示无机颗粒在体积基准的粒度分布中，从小粒径侧起，达到体积累积99％的粒径。
穿钉通过率测试：
将待测的锂离子电池以0.05C的倍率恒流充电至电压为4.45V(即满充电压)，随后以4.45V恒压充电至电流为0.025C(截止电流)，使锂离子电池达到满充状态，记录测试前锂离子电池外观。在25±3℃环境中对电池进行穿钉测试，钢钉直径4mm，穿刺速度30mm/s，穿钉位置位于锂离子电池侧面，测试进行3.5min或电极组件表面温度降到50℃以后停止测试，以10个锂离子电池为一组，观察测试过程中锂离子电池状态，以锂离子电池不燃烧、不爆炸为判定标准，20次穿钉测试通过15次以上判定为通过穿钉测试。
实施例1
<正极极片的制备>
<粘结剂的制备>
在反应釜中加入蒸馏水并启动搅拌，通入氮气除氧2h后，按质量比45︰45︰10向反应釜加入以下单体：丙烯腈、丙烯酸钠和丙烯酰胺，在惰性气氛下加热至65℃并保持恒温，然后加入20％的过硫酸铵溶液作为引发剂开始反应，至反应22小时后取出沉淀物，加入碱液中和pH至6.5。其中，蒸馏水、单体、引发剂之间的质量比为89.5︰10︰0.5。反应后对反应产物进行过滤、洗涤、烘干、粉碎、过筛等处理，得到粘结剂。
<绝缘层浆料的制备>
将制得的粘结剂、无机颗粒勃姆石和流平剂聚乙氧基丙氧基丙烯烃分散在去离子水中，搅拌均匀至浆料粘度稳定，得到固含量为30％的绝缘层浆料，其中粘结剂、无机颗粒与流平剂之间的质量比为15︰84.9︰0.1。流平剂的重均分子量为20000，粘结剂的重均分子量为500000，无机颗粒的Dv99为3μm。
<含有绝缘层的正极极片的制备>
将正极活性物质磷酸铁锂、PVDF、导电炭黑、碳纳米管按质量比96.8∶2∶0.7∶0.5混合，然后加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成固含量为75％的浆料A，并搅拌均匀。将浆料A均匀涂覆在厚度为12μm的集流体铝箔的一个表面上，90℃条件下烘干，得到厚度为50μm的第一活性层；
将制得的绝缘层浆料涂覆在铝箔表面的未涂覆第一活性层的区域，得到厚度为6μm的绝缘层，其中，粘结剂占绝缘层总质量的质量百分比为15％，无机颗粒占所述绝缘层总质量的质量百分比为84.9％，流平剂占绝缘层总质量的质量百分比为0.10％；
将正极活性物质钴酸锂(LCO)、聚偏二氟乙烯(PVDF)、导电炭黑、碳纳米管按质量比97∶1.5∶0.8∶0.7混合，然后加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成固含量为75％的浆料B，并搅拌均匀。将浆料B均匀涂覆在第一活性层上，90℃条件下烘干，得到厚度为50μm的第二活性层。第一活性层和第二活性层共同构成正极极片的正极活性物质层。然后在该正极极片的另一个表面上重复以上步骤，得到双面涂覆有正极活性物质层的正极极片。将正极极片裁切成74mm×867mm的规格并焊接极耳后待用。
<负极极片的制备>
将负极活性物质石墨、丁苯橡胶、羧甲基纤维素钠按照重量比97.5︰1.3︰1.2进行混合，加入去离子水作为溶剂，调配成为固含量为70％的浆料，并搅拌均匀。将浆料均匀涂覆在负极集流体铜箔上，110℃条件下烘干，冷压后得到负极活性物质层厚度为150μm的单面涂覆负极活性物质层的负极极片。
以上步骤完成后，采用同样的方法在该负极极片背面也完成这些步骤，即得到双面涂布完成的负极极片。涂布完成后，将负极极片裁切成规格为76mm×851mm的片材并焊接极耳待用。
<电解液的制备>
在干燥氩气气氛中，将有机溶剂碳酸乙烯酯、碳酸甲乙酯和碳酸二乙酯以质量比EC︰EMC︰DEC＝30︰50︰20混合得到有机溶液，然后向有机溶剂中加入锂盐六氟磷酸锂溶解并混合均匀，得到锂盐的浓度为1.15Mol/L的电解液。
<隔离膜的制备>
将氧化铝与聚丙烯酸酯依照质量比90∶10混合并将其溶入到去离子水中以形成固含量为50％的陶瓷浆料。随后采用微凹涂布法将陶瓷浆料均匀涂布到多孔基材(聚乙烯，厚度7μm，平均孔径为0.073μm，孔隙率为26％)的其中一面上，经过干燥处理以获得陶瓷涂层与多孔基材的双层结构，陶瓷涂层的厚度为50μm。
将聚偏二氟乙烯(PVDF)与聚丙烯酸酯依照质量比96∶4混合并将其溶入到去离子水中以形成固含量为50％的聚合物浆料。随后采用微凹涂布法将聚合物浆料均匀涂布到上述陶瓷涂层与多孔基材双层结构的两个表面上，经过干燥处理以获得隔离膜，其中聚合物浆料形成的单层涂层厚度为2μm。
<锂离子电池的制备>
将上述制备的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极极片中间起到隔离的作用，并卷绕得到电极组件。将电极组件装入铝塑膜包装袋中，并在80℃下脱去水分，注入配好的电解液，经过真空封装、静置、化成、整形等工序得到锂离子电池。
实施例2
除了在<绝缘层浆料的制备>中，流平剂占绝缘层总质量的质量百分比为0.18％以外，其余与实施例1相同。
实施例3
除了在<绝缘层浆料的制备>中，流平剂占绝缘层总质量的质量百分比为0.30％以外，其余与实施例1相同。
实施例4
除了在<正极极片的制备>中，流平剂占绝缘层总质量的质量百分比为1.00％以外，其余与实施例1相同。
实施例5
除了在<绝缘层浆料的制备>中，流平剂占绝缘层总质量的质量百分比为2.00％以外，其余与实施例1相同。
实施例6
除了在<绝缘层浆料的制备>中，流平剂占绝缘层总质量的质量百分比为5.00％，绝缘层厚度为10μm以外，其余与实施例1相同。
实施例7
除了在<绝缘层浆料的制备>中，流平剂选用聚硅氧烷以外，其余与实施例3相同。
实施例8
除了在<绝缘层浆料的制备>中，流平剂选用聚丙烯酸甲酯以外，其余与实施例3相同。
实施例9
除了在<绝缘层浆料的制备>中，流平剂选用聚丙烯醇以外，其余与实施例3相同。
实施例10
除了在<绝缘层浆料的制备>中，流平剂选用聚乙二醚，绝缘层厚度为4μm以外，其余与实施例3相同。
实施例11
除了在<绝缘层浆料的制备>中，流平剂占绝缘层总质量的质量百分比为0.18％，流平剂的重均分子量为5000以外，其余与实施例1相同。
实施例12
除了在<绝缘层浆料的制备>中，流平剂占绝缘层总质量的质量百分比为0.18％，流平剂的重均分子量为30000以外，其余与实施例1相同。
实施例13
除了在<绝缘层浆料的制备>中，流平剂占绝缘层总质量的质量百分比为0.18％，流平剂的重均分子量为50000以外，其余与实施例1相同。
实施例14
除了在<粘结剂的制备>中，粘结剂选用聚丙烯酸甲酯，粘结剂重均分子量为50000，流平剂占绝缘层总质量的质量百分比为0.20％，无机颗粒占绝缘层总质量的质量百分比为84.80％以外，其余与实施例1相同。
实施例15
除了在<粘结剂的制备>中，粘结剂选用丙烯腈多元共聚物以外，其余与实施例14相同。
实施例16
除了在<粘结剂的制备>中，粘结剂选用羧甲基纤维素钠以外，其余与实施例14相同。
实施例17
除了在<粘结剂的制备>中，粘结剂选用聚丙烯酸钠以外，其余与实施例14相同。
实施例18
除了在<粘结剂的制备>中，粘结剂选用聚丙烯酰胺以外，其余与实施例14相同。
实施例19
除了在<粘结剂的制备>中，单体选用质量比为40︰60的丙烯酰胺和丙烯酸钠，流平剂占绝缘层总质量的质量百分比为0.20％，粘结剂占绝缘层总质量的质量百分比为84.80％以外，其余与实施例1相同。
实施例20
除了在<粘结剂的制备>中，单体选用质量比为40︰60的丙烯腈和丙烯酰胺以外，其余与实施例19相同。
实施例21
除了在<粘结剂的制备>中，单体选用质量比为40︰60的丙烯腈和丙烯酸钠以外，其余与实施例19相同。
实施例22
除了在<粘结剂的制备>中，单体选用质量比为27︰60︰10︰3的丙烯腈、丙烯酸钠、丙烯酰胺和丙烯酸酯以外，其余与实施例19相同。
实施例23
除了在<粘结剂的制备>中，单体选用质量比为30︰60︰10的丙烯腈、丙烯酸钠和丙烯酰胺以外，其余与实施例19相同。
实施例24
除了在<粘结剂的制备>中，单体选用质量比为30︰10︰60的丙烯腈、丙烯酸钠和丙烯酰胺以外，其余与实施例19相同。
实施例25
除了在<粘结剂的制备>中，单体选用质量比为45︰10︰45的丙烯腈、丙烯酸钠和丙 烯酰胺以外，其余与实施例19相同。
实施例26
除了在<粘结剂的制备>中，单体选用质量比为60︰10︰30的丙烯腈、丙烯酸钠和丙烯酰胺，无机颗粒的Dv99为1μm以外，其余与实施例19相同。
实施例27
除了在<粘结剂的制备>中，单体选用质量比为70︰20︰10的丙烯腈、丙烯酸钠和丙烯酰胺以外，其余与实施例19相同。
实施例28
除了在<绝缘层浆料的制备>中，单体选用质量比为45︰10︰45的丙烯腈、丙烯酸钠和丙烯酰胺，粘结剂占绝缘层总质量的质量百分比为50％，无机颗粒占所述绝缘层总质量的质量百分比为49.8％，流平剂占绝缘层总质量的质量百分比为0.20％以外，其余与实施例1相同。
实施例29
除了在<绝缘层浆料的制备>中，粘结剂占绝缘层总质量的质量百分比为15％，无机颗粒占所述绝缘层总质量的质量百分比为84.8％以外，其余与实施例28相同。
实施例30
除了在<绝缘层浆料的制备>中，粘结剂占绝缘层总质量的质量百分比为2％，无机颗粒占所述绝缘层总质量的质量百分比为97.8％以外，其余与实施例28相同。
实施例31
除了在<绝缘层浆料的制备>中，粘结剂占绝缘层总质量的质量百分比为15％，无机颗粒占所述绝缘层总质量的质量百分比为84.8％，粘结剂的重均分子量为100000以外，其余与实施例28相同。
实施例32
除了在<绝缘层浆料的制备>中，粘结剂的重均分子量为800000以外，其余与实施例31相同。
实施例33
除了在<绝缘层浆料的制备>中，粘结剂的重均分子量为2000000以外，其余与实施例31相同。
实施例34
除了在<绝缘层浆料的制备>中，无机颗粒选用水铝石以外，其余与实施例29相同。
实施例35
除了在<绝缘层浆料的制备>中，无机颗粒选用氧化铝(Al 2O 3)以外，其余与实施例29相同。
实施例36
除了在<绝缘层浆料的制备>中，无机颗粒选用硫酸钡以外，其余与实施例29相同。
实施例37
除了在<绝缘层浆料的制备>中，单体选用质量比为40︰60的丙烯酰胺和丙烯酸钠以外，其余与实施例28相同。
实施例38
除了在<绝缘层浆料的制备>中，单体选用质量比为40︰60的丙烯酰胺和丙烯酸钠以外，其余与实施例30相同。
实施例39
除了在<绝缘层浆料的制备>中，单体选用质量比为40︰60的丙烯酰胺和丙烯酸钠以外，其余与实施例31相同。
对比例1
除了在<绝缘层浆料的制备>中，不添加流平剂，粘结剂与无机颗粒之间的质量比为15︰85以外，其余与实施例1相同。
对比例2
除了在<绝缘层浆料的制备>中，流平剂的重均分子量为100000以外，其余与实施例1相同。
对比例3
除了在<绝缘层浆料的制备>中，不添加流平剂，粘结剂选用PVDF，粘结剂重均分子量为700000，粘结剂与无机颗粒之间的质量比为12︰88以外，其余与实施例1相同。
对比例4
除了在<绝缘层浆料的制备>中，不添加流平剂，粘结剂选用聚丙烯酸，粘结剂重均分子量为1500000，粘结剂与无机颗粒之间的质量比为12︰88，无机颗粒选用氧化铝以外，其余与实施例1相同。
对比例5
除了在<粘结剂的制备>中，粘结剂的重均分子量为50000以外，其余与实施例29相同。
对比例6
除了在<粘结剂的制备>中，粘结剂的重均分子量为3000000以外，其余与实施例29相同。
对比例7
除了在<粘结剂的制备>中，单体选用质量比为10︰75︰15的丙烯腈、丙烯酸钠和丙烯酰胺以外，其余与实施例23相同。
对比例8
除了在<粘结剂的制备>中，单体选用质量比为80︰5︰15的丙烯腈、丙烯酸钠和丙烯酰胺以外，其余与实施例23相同。
各实施例和对比例的制备参数及测试结果如下表1-2所示：
表1 实施例1-13和对比例1-2的制备参数及测试结果
Figure PCTCN2020132394-appb-000001
表2 实施例14-39和对比例3-8的制备参数及测试结果
Figure PCTCN2020132394-appb-000002
Figure PCTCN2020132394-appb-000003
Figure PCTCN2020132394-appb-000004
从表1实施例1-13和对比例1-2可以看出，具有本申请绝缘层的锂离子电池，绝缘层中的火山口状凸起数量明显减少，表明本申请能够显著减少甚至消除绝缘层中火山口状凸起的数量。
从表1实施例1-13和对比例1-2还可以看出，绝缘层最大厚度与最小厚度之差均小于对比例1-2，表明本申请的锂离子电池中绝缘层的厚度更加均匀；绝缘层覆盖度与对比例1-2相当或提高。
从表1实施例1-13和对比例1-2还可以看出，具有本申请绝缘层的锂离子电池，其穿钉通过率明显提高，表明申请的绝缘层能够显著提高锂离子电池的安全性能。
从表2实施例14-39和对比例3-8可以看出，具有本申请绝缘层的锂离子电池，绝缘层与集流体之间的粘结力显著提高，尤其是实施例33，绝缘层与集流体之间的粘结力达到400N/m。
从表2实施例14-39和对比例3-8还可以看出，绝缘层覆盖度与对比例3-8相当或提高。
从表2实施例14-39和对比例3-8还可以看出，具有本申请绝缘层的锂离子电池，其穿钉通过率明显提高，表明申请的绝缘层能够显著提高锂离子电池的安全性能。
综上所述，本申请的绝缘层，以及具有本申请绝缘层的正极极片能够显著提高绝缘层与集流体之间的粘结力，以及显著提高锂离子电池的安全性能。
以上所述仅为本申请的较佳实施例，并不用以限制本申请，凡在本申请的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本申请保护的范围之内。

Claims (15)

  1. 一种电化学装置，包括正极，所述正极包括集流体，所述集流体包括设置有活性物质的涂覆区和未设置所述活性物质的未涂覆区；所述未涂覆区至少部分设置有绝缘层，所述绝缘层包括粘结剂、无机颗粒和流平剂，所述绝缘层中的火山口状凸起数量为0个/cm 2至0.25个/cm 2。
  2. 根据权利要求1所述的电化学装置，其中，所述绝缘层最大厚度与最小厚度之差不大于3μm。
  3. 根据权利要求1所述的电化学装置，其中，所述流平剂为重均分子量不高于50000的聚合物。
  4. 根据权利要求1所述的电化学装置，其中，所述流平剂包括含氧丙烯烃聚合物、硅氧烷聚合物、丙烯酸酯聚合物、丙烯醇聚合物或乙二醚聚合物中的至少一种。
  5. 根据权利要求1所述的电化学装置，其中，所述流平剂包括聚乙氧基丙氧基丙烯烃、聚硅氧烷、聚丙烯酸甲酯或聚丙烯醇或聚乙二醚中的至少一种。
  6. 根据权利要求1所述的电化学装置，其中，所述绝缘层的覆盖度不低于95％。
  7. 根据权利要求1所述的电化学装置，其中，所述粘结剂的重均分子量为100000至2000000。
  8. 根据权利要求1所述的电化学装置，其中，所述粘结剂包括丙烯烃类衍生物的共聚物、聚丙烯酸酯、丙烯腈多元共聚物或羧甲基纤维素盐中的至少一种。
  9. 根据权利要求1所述的电化学装置，其中，所述粘结剂包括丙烯腈、丙烯酸盐、丙烯酰胺和丙烯酸酯中的至少一种单体聚合形成的聚合物。
  10. 根据权利要求9所述的电化学装置，其中，基于所述聚合物的总质量，所述丙烯腈的质量百分含量为25％至70％，所述丙烯酸盐的质量百分含量为10％至60％，所述丙烯酰胺的质量百分含量为10％至60％，所述丙烯酸酯的质量百分含量为0％至10％。
  11. 根据权利要求1所述的电化学装置，其中，所述无机颗粒包括勃姆石、水铝石、氧化铝、硫酸钡、硫酸钙或硅酸钙中的至少一种。
  12. 根据权利要求1所述的电化学装置，其中，基于所述绝缘层的总质量，所述流平剂的质量百分含量为0.1％至5％，所述粘结剂的质量百分含量为2％至50％，所述无机颗粒的质量百分含量为50％至98％。
  13. 根据权利要求1所述的电化学装置，其中，所述绝缘层的厚度为1μm至10μm。
  14. 根据权利要求1所述的电化学装置，其中，所述绝缘层与所述集流体之间的粘结力不小于201N/m。
  15. 一种电子装置，包含权利要求1至14中任一项所述的电化学装置。
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