WO2022199628A1 - 一种正极片和锂离子电池 - Google Patents

一种正极片和锂离子电池 Download PDF

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Publication number
WO2022199628A1
WO2022199628A1 PCT/CN2022/082551 CN2022082551W WO2022199628A1 WO 2022199628 A1 WO2022199628 A1 WO 2022199628A1 CN 2022082551 W CN2022082551 W CN 2022082551W WO 2022199628 A1 WO2022199628 A1 WO 2022199628A1
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Prior art keywords
positive electrode
lithium
safety coating
electrode sheet
coating
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PCT/CN2022/082551
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English (en)
French (fr)
Inventor
张双虎
彭宁
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珠海冠宇电池股份有限公司
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Priority to EP22744638.2A priority Critical patent/EP4086982A1/en
Priority to CN202280002238.0A priority patent/CN115066767A/zh
Priority to US17/816,729 priority patent/US20220376265A1/en
Publication of WO2022199628A1 publication Critical patent/WO2022199628A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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 a positive electrode sheet and a lithium ion battery, and relates to the technical field of lithium ion batteries.
  • lithium-ion batteries have become an ideal power supply device, and at the same time, higher requirements have been placed on the safety of lithium-ion batteries.
  • the winding process is to prepare the battery cell by winding the positive electrode sheet, the negative electrode sheet and the separator, so the winding process is used to prepare the battery cell.
  • the obtained battery core is also called a roll core, and after the roll core is prepared, a lithium ion battery can be prepared through processes such as packaging and liquid injection.
  • the general winding core is terminated with a positive electrode sheet, that is, the outermost layer of the winding core is the positive electrode current collector.
  • the present application provides a positive electrode sheet for improving the puncture pass rate of a lithium ion battery.
  • a first aspect of the present application provides a positive electrode sheet, the positive electrode sheet includes a positive electrode current collector, a functional layer and a first safety coating;
  • both the upper surface and the lower surface of the positive electrode current collector include a first coating area and a second coating area, and the first coating area is provided with the first safety coating; the second coating area
  • the functional layer is disposed on the cladding area, and the functional layer sequentially includes a second safety coating and a positive electrode active layer in a direction away from the positive electrode current collector.
  • FIG. 1 is a schematic structural diagram of a positive electrode sheet provided by an embodiment of the application. As shown in FIG.
  • the upper and lower surfaces of the positive electrode current collector 101 both include a first coating area and a Two coating areas, the first safety coating 102 is provided on the first coating area, and a functional layer is provided on the second coating area, and the functional layer is in a direction away from the positive electrode current collector Including the second safety coating 103 and the positive electrode active layer 104 in turn, that is, the second safety coating 103 is arranged on the second coating area of the upper surface and the lower surface of the positive electrode current collector 101, and the positive active layer 104 is arranged on the second safety coating. away from the surface of the positive electrode current collector 101 .
  • the positive electrode sheet provided by the present application, by setting the first safety coating on the surface of the positive electrode current collector, it can effectively prevent the positive electrode current collector from contacting the negative electrode active layer, increase the short-circuit internal resistance during the acupuncture process, prevent the temperature from rising, and improve the lithium ion battery. puncture pass rate.
  • the first safety coating includes inorganic particles, the inorganic particles are CuO, Gd 2 O, Lu 2 O 3 , Sm 2 O 3 , NiO, SiO 2 , Al 2 O 3 , TiO 2 , WO 3 , ZnO, Ag 2 Se, MoS 2 , ZrO 2 , Y 2 O 3 , SiC, CeO 2 , SnO 2 , Al 2 O 3 /Ag/ZnO, Al 2 O 3 /CdS, Al 2 O 3 One or more of /MgO, Al 2 O 3 /ZnO, Al(OH) 3 , Mg(OH) 2 , Ca(OH) 2 , Ba 2 SO 4 , and ⁇ -AlOOH.
  • the inorganic particles have D10 of 0.05-0.3 ⁇ m, D50 of 0.5-1.5 ⁇ m, D90 of less than 4.5 ⁇ m, and specific surface area of 0.1-16 m 2 /g.
  • FIG. 2 is a schematic structural diagram of a lithium ion battery provided by an embodiment of the application. As shown in FIG. 2 , it includes a positive electrode sheet 100, a negative electrode sheet 200 and a separator that are wound from the inside to the outside.
  • the area covered by the non-functional layer of the positive electrode current collector is covered with the first safety coating, and the first safety coating is located in the outer layer of the winding core, and those skilled in the art know that,
  • tape it is necessary to use tape to glue the outermost first safety coating to the outer casing to prevent the risk of short circuit caused by the folding of the pole pieces during the falling process of lithium-ion batteries. Therefore, in order to further improve the safety of lithium-ion batteries
  • fillers with rough surface can be selected and added to the first safety coating, thereby improving the peel strength of the first safety coating and the tape, and improving the drop pass rate of the lithium ion battery, specifically:
  • the first safety coating includes fillers, and the fillers are lithium cobalt oxide, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium iron phosphate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, One or more of lithium-rich manganese-based materials, lithium nickel cobalt aluminate, lithium titanate, aluminum fibers and aluminum silicate fibers; the filler selected in this application is a common material in the field, has high stability, and is not compatible with Electrolyte and active material have the advantages of electrochemical reaction, and the above materials are easy to obtain, which has economic benefits and practical application value.
  • the fillers are further divided into particle fillers and fiber fillers.
  • the particle size of the particle fillers should not be too large, otherwise the compactness of the first safety coating will be affected, thereby affecting the safety of lithium-ion batteries.
  • the lithium cobalt oxide, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium iron phosphate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadium phosphate, lithium-rich manganese-based materials, nickel-cobalt aluminate The D10 of lithium and lithium titanate is 0.01-0.5 ⁇ m, D50 is 0.02-1.5 ⁇ m, D90 is 1.6-4.0 ⁇ m, and the specific surface area is 0.1-15m 2 /g; the diameter and length of the fiber filler should not be too high, otherwise it will It affects the thickness and compactness of the first safety coating. In addition, too long fiber length is not conducive to the dispersion of fiber fillers. Specifically, the diameter of the aluminum fibers and aluminum silicate fibers is 0.1-3 ⁇ m and the length is 1-20 ⁇ m. .
  • the puncture pass rate of lithium ion battery will decrease instead. Therefore, in order to take into account the puncture pass rate and drop pass rate of lithium ion battery, the The mass of the filler is not more than 40% of the mass of the first safety coating.
  • the present application tested the peel strength between the first safety coating and the fixing tape, and the test results showed that the peeling force between the first safety coating and the fixing tape was 3-30N/m.
  • the peeling force between the first safety coating and the fixing tape can be further improved, the drop passing rate of the lithium ion battery can be improved, and the safety can be improved.
  • the first safety coating can also include a conductive agent.
  • the conductive agent is a common material in the field, and its thermal conductivity is relatively high.
  • the conductive agent can prevent the accumulation of heat, thereby reducing the local temperature of the lithium-ion battery and improving the safety of the lithium-ion battery; High and porous, it can effectively absorb the electrolyte between the lithium-ion battery cell and the outer casing, and improve the electrolyte injection efficiency.
  • adding a conductive agent to the first safety coating helps prevent the internal temperature of the lithium-ion battery
  • the content of the conductive agent should not be too high, otherwise it will affect the internal resistance of the first safety coating and reduce the puncture pass rate of the lithium-ion battery. Therefore, it is necessary to adjust the content of the conductive agent.
  • Control is carried out so that the total volumetric internal resistance of the first safety coating and the positive electrode current collector is 10-3500m ⁇ , and further, the total volumetric internal resistance of the first safety coating and the positive electrode current collector is 20-3500m ⁇ , and the total volumetric internal resistance is Refers to the volume internal resistance of the first safety coating and the positive electrode current collector as a whole.
  • the resistance test is performed using the ACCFILM diaphragm resistance test system, and the positive electrode sheet containing the first safety coating is placed between the test indenters for testing.
  • the conductive agent can be a conventional material in the art, for example, the conductive agent is one or more of carbon black, carbon fiber, carbon nanotube, graphite, graphene, metal powder, composite conductive material, and conductive ceramic powder.
  • the first safety coating includes inorganic particles; or inorganic particles and conductive agents; or inorganic particles and fillers; or inorganic particles, Filler and conductive agent, in addition, in order to bond the first safety coating with the positive electrode current collector, the first safety coating also includes a binder, specifically, the binder is selected from polyvinylidene fluoride, polyvinylidene fluoride, Copolymer of vinyl fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethacrylic acid Methyl ester, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber, polyethersulfone, polyimide, polyethylene terephthalate, s
  • the binder is selected from polyvinylidene fluoride, polyvinylid
  • the first safety coating is less than or equal to the thickness of the second safety coating.
  • the thickness of the first safety coating is 3-15 ⁇ m.
  • the second safety coating compared with the first safety coating, the second safety coating also needs to participate in the electrochemical reaction. Therefore, the second safety coating must include a conductive agent, and the content of the conductive agent should be greater than that of the first safety coating.
  • the content of the conductive agent in the coating that is, the materials of the first safety coating and the second safety coating are different.
  • the second safety coating slurry is applied to different positions on the surface of the positive electrode current collector. Therefore, in order to facilitate the preparation of lithium ion batteries, an interval can be set between the functional layer and the first safety coating. Specifically, the The distance between the functional layer and the first safety coating is d, 0 ⁇ d ⁇ 10mm.
  • FIG. 3 is a schematic structural diagram of a positive electrode sheet provided by another embodiment of the present application.
  • the second safety coating 103 on the upper surface or the lower surface of the positive electrode current collector 101 , the positive active layer 104 and the first safety coating A space is set between 102, and the distance between the two is d.
  • the distance d between the upper surface and the lower surface of the positive electrode current collector 101 can be the same or different, and those skilled in the art can set it according to actual needs.
  • FIG. 4 is a schematic structural diagram of a positive electrode sheet provided by another embodiment of the application. As shown in FIG. 4 , the positive active layer The length of 104 is slightly larger than the length of the second safety coating 103 , and the distance d between the functional layer and the first safety coating is the distance between the positive active layer 104 and the first safety coating 102 .
  • the positive electrode current collector is aluminum foil
  • the second safety coating slurry includes a first active material, a binder and a conductive agent, and the first active material is lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium iron phosphate, manganese phosphate
  • the first active material is lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium iron phosphate, manganese phosphate
  • the positive electrode active layer slurry includes a second positive electrode active material, a conductive agent and a binder, and the second active material is lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium-rich manganese-based material, lithium iron phosphate One or more of them, D50 is 7-15 ⁇ m, D90 is less than or equal to 25 ⁇ m;
  • the selection of conductive agent and binder is the same as that of the first safety coating.
  • the mass of the first active substance in the second safety coating is 45-95% of the total mass of the second safety coating, further 47-94%, and the quality of the binder is 3-50% of the total mass of the second safety coating %, the mass of the conductive agent is 1-5% of the total mass of the second safety coating;
  • the mass of the second positive active material in the positive active layer is 93-98% of the total mass of the positive active layer, the mass of the binder is 1-3% of the total mass of the positive active layer, and the mass of the conductive agent is the total mass of the positive active layer. 0.5-2%.
  • the thickness of the second safety coating is 3-20 ⁇ m; the thickness of the active material layer is more than 25 ⁇ m.
  • the present application provides a positive electrode sheet.
  • a first safety coating on the surface of the positive electrode current collector, it can effectively prevent the positive electrode current collector from contacting the negative electrode active layer, increase the short-circuit internal resistance during the acupuncture process, and prevent the temperature from rising. , to improve the puncture pass rate of lithium-ion batteries.
  • a second aspect of the present application provides a lithium ion battery, the lithium ion battery comprising any one of the negative electrode sheets described above.
  • the present application provides a lithium ion battery.
  • a coil core is prepared with a negative electrode sheet and a separator through a winding process, and a lithium ion battery is obtained after packaging and liquid injection.
  • the lithium ion battery provided by the present application has a good puncture pass rate.
  • the length of the cathode current collector covered by the non-functional layer should be reduced as much as possible, specifically, the length of the first safety coating covering the inner surface of the outermost cathode current collector near the winding center less than or equal to 1/2 of the outermost cathode current collector.
  • the upper and lower surfaces of the cathode current collector on the far left of the lithium ion battery are not covered by functional layers. Therefore, the length of this part of the cathode current collector should be reduced as much as possible.
  • the length of the first safety coating near the inner surface of the winding center is equal to the length of the cathode current collector covered by the non-functional layer, therefore, the length of the first safety coating disposed on the inner surface of the outermost cathode current collector close to the winding center Less than 1/2 of the outermost cathode current collector.
  • the length of the negative electrode sheet is greater than the length of the positive electrode sheet. Therefore, the vertical alignment between the negative electrode sheet and the first safety coating on the outermost positive electrode sheet The projections must be partially overlapped. Specifically, the overlapping area of the portion of the negative electrode sheet beyond the positive electrode sheet and the vertical projection of the first safety coating on the outermost positive electrode sheet is greater than or equal to 0.5 ⁇ m.
  • the length of the negative electrode sheet 200 is greater than the length of the positive electrode sheet 100, and the part of the negative electrode sheet 200 beyond the positive electrode sheet 100 (the part in the dashed box in FIG. 2) and the first safety coating 102 are in the outermost positive electrode
  • the positive electrode sheet provided by this application by setting the first safety coating on the surface of the positive electrode current collector, can effectively prevent the positive electrode current collector from contacting the negative electrode active layer, increase the short-circuit internal resistance during the acupuncture process, prevent the temperature from rising, and increase the lithium ion The puncture pass rate of the ion battery.
  • the drop passing rate of the lithium ion battery can be further improved, and the safety of the lithium ion battery can be improved.
  • the lithium ion battery provided in this application has a good puncture pass rate.
  • FIG. 1 is a schematic structural diagram of a positive electrode sheet provided in an embodiment of the application
  • FIG. 2 is a schematic structural diagram of a lithium ion battery provided in an embodiment of the application.
  • FIG. 3 is a schematic structural diagram of a positive electrode sheet provided by another embodiment of the present application.
  • FIG. 4 is a schematic structural diagram of a positive electrode sheet provided by another embodiment of the present application.
  • the positive electrode sheet provided in this embodiment has the structure shown in FIG. 1 , including a positive electrode current collector aluminum foil, a first safety coating, a positive electrode active layer and a second safety coating, specifically:
  • the first safety coating includes 90 parts by mass of aluminum oxide (Al 2 O 3 ) and 10 parts by mass of polyvinylidene fluoride (PVDF), wherein the D10 of aluminum oxide (Al 2 O 3 ) is 0.15 ⁇ m , D50 is 0.32 ⁇ m, D90 is 0.65 ⁇ m, the specific surface area is 15.6 m 2 /g, and the single-sided thickness of the first safety coating is 5 ⁇ m.
  • Al 2 O 3 aluminum oxide
  • PVDF polyvinylidene fluoride
  • the second safety coating comprises 65 parts by mass of lithium iron phosphate, 30 parts by mass of polyvinylidene fluoride and 5 parts by mass of carbon black, D50 of lithium iron phosphate is 0.75 ⁇ m, D90 is 5.05 ⁇ m, and thickness is 8 ⁇ m;
  • the positive active layer includes 97 parts by mass of lithium cobalt oxide, 1.3 parts by mass of polyvinylidene fluoride and 1.7 parts by mass of carbon black, D50 of lithium cobalt oxide is 10 ⁇ m, D90 is 25 ⁇ m, and thickness is 95 ⁇ m;
  • a gravure coater is used to coat the first safety coating slurry on the first coating area of the upper surface and the lower surface of the aluminum foil, and after drying at 110°C, the first safety coating is obtained;
  • the first safety coating includes 80 parts by mass of aluminum oxide (Al 2 O 3 ), 10 parts by mass of LiFePO 4 and 10 parts by mass of polyvinylidene fluoride (PVDF);
  • the D10 of LiFePO 4 is 0.37 ⁇ m, the D50 is 0.75 ⁇ m, the D90 is 2.30 ⁇ m, and the specific surface area is 10 m 2 /g.
  • the first safety coating layer includes 70 parts by mass of aluminum oxide (Al 2 O 3 ), 20 parts by mass of LiFePO 4 and 10 parts by mass of polyvinylidene fluoride (PVDF).
  • Al 2 O 3 aluminum oxide
  • LiFePO 4 LiFePO 4
  • PVDF polyvinylidene fluoride
  • the first safety coating layer includes 60 parts by mass of aluminum oxide (Al 2 O 3 ), 30 parts by mass of LiFePO 4 and 10 parts by mass of polyvinylidene fluoride (PVDF).
  • Al 2 O 3 aluminum oxide
  • LiFePO 4 LiFePO 4
  • PVDF polyvinylidene fluoride
  • the first safety coating comprises 85 parts by mass of aluminum oxide (Al 2 O 3 ), 5 parts by mass of aluminum fibers and 10 parts by mass of polyvinylidene fluoride (PVDF);
  • the diameter of the aluminum fibers is 2 ⁇ m and the length is 15 ⁇ m.
  • the first safety coating comprises 85 parts by mass of aluminum oxide (Al 2 O 3 ), 5 parts by mass of aluminum silicate fibers and 10 parts by mass of polyvinylidene fluoride (PVDF);
  • the aluminosilicate fibers were 2 ⁇ m in diameter and 15 ⁇ m in length.
  • the first safety coating layer includes 80 parts by mass of aluminum oxide (Al 2 O 3 ), 10 parts by mass of LiFePO 4 , 1.5 parts by mass of carbon black as a conductive agent, and 8.5 parts by mass of polyvinylidene fluoride (PVDF).
  • Al 2 O 3 aluminum oxide
  • LiFePO 4 LiFePO 4
  • carbon black as a conductive agent
  • PVDF polyvinylidene fluoride
  • the first safety coating layer includes 80 parts by mass of aluminum oxide (Al 2 O 3 ), 10 parts by mass of LiFePO 4 , 2.5 parts by mass of carbon black as a conductive agent, and 7.5 parts by mass of polyvinylidene fluoride (PVDF).
  • Al 2 O 3 aluminum oxide
  • LiFePO 4 LiFePO 4
  • carbon black as a conductive agent
  • PVDF polyvinylidene fluoride
  • the first safety coating layer includes 78 parts by mass of aluminum oxide (Al 2 O 3 ), 2.5 parts by mass of carbon black as a conductive agent, and 19.5 parts by mass of polyvinylidene fluoride (PVDF).
  • the first safety coating layer includes 75.5 parts by mass of aluminum oxide (Al 2 O 3 ), 5 parts by mass of carbon black as a conductive agent, and 19.5 parts by mass of polyvinylidene fluoride (PVDF).
  • Al 2 O 3 aluminum oxide
  • carbon black as a conductive agent
  • PVDF polyvinylidene fluoride
  • the first safety coating layer includes 70.5 parts by mass of aluminum oxide (Al 2 O 3 ), 10 parts by mass of carbon black as a conductive agent, and 19.5 parts by mass of polyvinylidene fluoride (PVDF).
  • Al 2 O 3 aluminum oxide
  • PVDF polyvinylidene fluoride
  • the first safety coating layer includes 65.5 parts by mass of aluminum oxide (Al 2 O 3 ), 15 parts by mass of carbon black as a conductive agent, and 19.5 parts by mass of polyvinylidene fluoride (PVDF).
  • Al 2 O 3 aluminum oxide
  • carbon black as a conductive agent
  • PVDF polyvinylidene fluoride
  • the first safety coating layer includes 60.5 parts by mass of aluminum oxide (Al 2 O 3 ), 20 parts by mass of carbon black as a conductive agent, and 19.5 parts by mass of polyvinylidene fluoride (PVDF).
  • Al 2 O 3 aluminum oxide
  • carbon black carbon black
  • PVDF polyvinylidene fluoride
  • the first safety coating layer includes 50.5 parts by mass of aluminum oxide (Al 2 O 3 ), 30 parts by mass of carbon black as a conductive agent, and 19.5 parts by mass of polyvinylidene fluoride (PVDF).
  • Al 2 O 3 aluminum oxide
  • carbon black as a conductive agent
  • PVDF polyvinylidene fluoride
  • the first safety coating layer includes 79.5 parts by mass of aluminum oxide (Al 2 O 3 ), 1 part by mass of carbon black as a conductive agent, and 19.5 parts by mass of polyvinylidene fluoride (PVDF).
  • Al 2 O 3 aluminum oxide
  • carbon black as a conductive agent
  • PVDF polyvinylidene fluoride
  • the first safety coating layer includes 79.65 parts by mass of aluminum oxide (Al 2 O 3 ), 0.85 parts by mass of carbon black as a conductive agent, and 19.5 parts by mass of polyvinylidene fluoride (PVDF).
  • Al 2 O 3 aluminum oxide
  • PVDF polyvinylidene fluoride
  • the first safety coating layer includes 79.85 parts by mass of aluminum oxide (Al 2 O 3 ), 0.65 parts by mass of carbon black as a conductive agent, and 19.5 parts by mass of polyvinylidene fluoride (PVDF).
  • Al 2 O 3 aluminum oxide
  • PVDF polyvinylidene fluoride
  • the first safety coating layer includes 80 parts by mass of aluminum oxide (Al 2 O 3 ), 0.5 parts by mass of carbon black as a conductive agent, and 19.5 parts by mass of polyvinylidene fluoride (PVDF).
  • Al 2 O 3 aluminum oxide
  • PVDF polyvinylidene fluoride
  • the positive electrode sheet provided in this comparative example includes a positive electrode current collector, a second safety coating layer and a positive electrode active layer, that is, does not include the first safety coating layer.
  • a lithium ion battery was prepared by winding the positive electrode sheet provided in Examples 1-18 and Comparative Example 1 with a negative electrode sheet and a separator, and a safety test was carried out on the lithium ion battery.
  • the test results are shown in Table 1:
  • the preparation method of the negative electrode sheet includes: dissolving 95 parts by mass of graphite, 1.5 parts by mass of CMC, 1.5 parts by mass of SBR and 2 parts by mass of carbon black in deionized water, and uniformly mixing to obtain a negative electrode active layer slurry; The slurry was coated on the upper and lower surfaces of the copper foil, dried at 70-100°C for 2-5min, and then rolled into 1100mm ⁇ 66.5mm negative electrode sheets. The thickness of the single-sided negative electrode active layer was 120 ⁇ m.
  • the acupuncture test method includes: in the normal temperature environment, charge the lithium-ion battery with a constant current of 0.5C to a voltage of 4.35V, and then charge it with a constant voltage to a current of 0.025C; transfer the lithium-ion battery to the nail penetration test equipment On, keep the test environment temperature at 25°C, use a steel nail with a diameter of 4mm to pass through the side of the negative ear and 7mm from the side of the cell at a constant speed of 30mm/s, and keep it for 300s. The lithium-ion battery does not catch fire and does not explode. pass.
  • the pass rate of the acupuncture test the number of batteries passed by acupuncture/the total number of batteries by acupuncture.
  • the volume resistance test method includes: testing the total volume resistance of the first safety coating and the positive electrode current collector using the ACCFILM diaphragm resistance test system, the diameter D of the test indenter is 14mm, and during the test, the positive electrode sheet is Place it between the upper and lower cylindrical indenters, adjust the pressure to 0.4MPa, start the test switch, and record the test data; each group is tested with 10 data points, the distance between the test points is 5mm, and the average value is taken as the value of the volume resistance.
  • the resistance measurement accuracy of the test system is 0.1 ⁇ -100m ⁇ , and the resistance measurement range is 0.1 ⁇ -3000 ⁇ .
  • the test method for the peel strength of the first safety coating and the fixing tape includes: cutting the positive electrode sheet into small pieces of positive electrode sheet with a length of 240mm and a width of 30mm, using NITTO No. Cut it into small pieces of tape according to the specifications, stick one side of the small piece of tape on the steel plate (260mm*50mm), and bond the other side with the small piece of positive electrode to ensure that the small piece of positive electrode completely covers the small piece of tape; use a hand-held roller (diameter 95mm, width 45mm) , weight 2kg) roll back and forth 3 times, bond the positive electrode piece and the tape piece together, and then use the tensile machine (the tensile machine model Dongguan Kejian KJ-1065 series) to test (180 degree peeling), and then 10mm/min
  • the test equipment automatically records the tensile force value that changes with the peeling displacement.
  • the lithium-ion battery is placed in the fixture, and the surface drop, edge drop and point drop test are carried out.
  • the test distance is 1.2m, and each of the six three-dimensional directions is free to drop once.
  • the volume resistance and puncture pass rate of the lithium ion batteries provided in Examples 1-8 are greater than those of Comparative Example 1. Therefore, setting the first safety coating is beneficial to improve the puncture pass rate of the lithium ion battery; according to It can be seen from Example 1 and Examples 2-4 that the inclusion of particulate fillers in the first safety coating is beneficial to improve the peeling force between the first safety coating and the tape, thereby improving the drop-through rate of lithium ion batteries, but with the increase of particles When the mass fraction of the filler increases, the puncture pass rate of the lithium-ion battery will decrease.
  • the mass fraction of the particulate filler is 10%, the overall safety of the lithium-ion battery is better; according to Examples 5-6, the use of fiber The peeling force between the first safety coating and the tape is improved after filling, but since the aluminum fiber is purely conductive, the puncture pass rate of the lithium-ion battery is reduced, while the aluminum silicate fiber has better electrical insulation and volume.
  • the resistance is relatively large and has a good puncture pass rate; it can be seen from Examples 7-8 that adding an appropriate amount of conductive agent to the first safety coating is also conducive to preventing the accumulation of the internal temperature of the lithium-ion battery and improving the safety of the lithium-ion battery; According to Examples 9-18, when a conductive agent is included in the first safety coating, the content of the conductive agent should be controlled, and the total volume resistance of the current collector and the first safety coating should be controlled at 20-3500 m ⁇ .

Abstract

本申请提供一种正极片和锂离子电池。本申请第一方面提供了一种正极片，所述正极片包括正极集流体、功能层和第一安全涂层；其中，所述正极集流体的上表面和下表面均包括第一涂覆区和第二涂覆区，所述第一涂覆区上设置有所述第一安全涂层；所述第二涂覆区上设置有所述功能层，且所述功能层在远离所述正极集流体的方向上依次包括第二安全涂层和正极活性层。本申请提供的正极片，通过在正极集流体表面设置第一安全涂层，可有效阻止正极集流体与负极活性层接触，增加针刺过程中的短路内阻，阻止温度上升，提高了锂离子电池的穿刺通过率。

Description

一种正极片和锂离子电池
本申请要求于2021年03月23日提交中国专利局、申请号为202110310733.5、申请名称为“一种正极片和锂离子电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及一种正极片和锂离子电池，涉及锂离子电池技术领域。
背景技术
随着消费类电子和电动汽车的迅猛发展，锂离子电池已成为其理想的供电装置，与此同时，也对锂离子电池的安全性提出了更高的要求。
根据锂离子电池制作工艺的不同，可分为叠片工艺和卷绕工艺，其中，卷绕工艺是将正极片、负极片和隔膜以卷绕的方式制备得到电芯，因此由卷绕工艺制备得到的电芯也称为卷芯，在制备得到卷芯后即可经封装、注液等工序制备得到锂离子电池。
一般的卷芯采用正极片收尾，即卷芯最外层为正极集流体，当卷芯在高SOC下发生穿刺情况时，其内部易发生短路，容易造成冒烟、起火的问题。因此如何提高通过卷绕工艺制备得到的锂离子电池的穿刺通过率受到了越来越多的关注。
发明内容
本申请提供了一种正极片，用于提高锂离子电池的穿刺通过率。
本申请第一方面提供了一种正极片，所述正极片包括正极集流体、功能层和第一安全涂层；
其中，所述正极集流体的上表面和下表面均包括第一涂覆区和第二涂覆区，所述第一涂覆区上设置有所述第一安全涂层；所述第二涂覆区上设置有所述功能层，且所述功能层在远离所述正极集流体的方向上依次包括第二安全涂层和正极活性层。
本申请提供了一种正极片，由于正极集流体与负极活性层的接触是造成锂离子电池起火的主要原因，因此，本申请在裸露的正极集流体表面设置第一安全涂层，以提高锂离子电池的穿刺通过率，例如，图1为本申请一实施例提供的正极片的结构示意图，如图1所示，正极集流体101的上表面和下表面均包括第一涂覆区和第二涂覆区，所述第一涂覆区上设置有所述第一安全涂层102，第二涂覆区上设置有功能层，且所述功能层在远离所述正极集流体的方向上依次包括第二安全涂层103和正极活性层104，即第二安全涂层103设置在正极集流体101上表面和下表面的第二涂覆区，正极活性层104设置在第二安全涂层远离正极集流体101的表面。本申请提供的正极片，通过在正极集流体表面设置第一安全涂层，可有效阻止正极集流体与负极活性层接触，增加针刺过程中的短路内阻，阻止温度上升，提高锂离子电池的穿刺通过率。
在一种实施方式中，所述第一安全涂层包括无机粒子，所述无机粒子为CuO、Gd 2O、Lu 2O 3、Sm 2O 3、NiO、SiO 2、Al 2O 3、TiO 2、WO 3、ZnO、Ag 2Se、MoS 2、ZrO 2、Y 2O 3、SiC、CeO 2、SnO 2、Al 2O 3/Ag/ZnO、Al 2O 3/CdS、Al 2O 3/MgO、Al 2O 3/ZnO、Al(OH) 3、Mg(OH) 2、Ca(OH) 2、Ba 2SO 4、γ-AlOOH中的一种或多种。
进一步地，所述无机粒子的D10为0.05-0.3μm，D50为0.5-1.5μm，D90小于4.5μm，比表面积为0.1-16m 2/g。
当本申请提供的正极片通过卷绕工艺制备得到卷芯时，以图1所示的正极片的最左侧为卷绕中心，根据卷芯的实际生产需要进行卷绕，第一安全涂层位于远离卷绕中心的位置，例如，图2为本申请一实施例提供的锂离子电 池的结构示意图，如图2所示，其包括由内向外卷绕的正极片100、负极片200和隔膜(图中未示出)，从图2可以看出，正极集流体无功能层覆盖的区域均覆盖第一安全涂层，且第一安全涂层位于卷芯外层，本领域技术人员知晓，锂离子电池制备过程中，需要使用胶带将最外层的第一安全涂层与外壳胶粘，防止锂离子电池跌落过程因极片翻折导致的短路风险，因此，为了进一步提高锂离子电池的跌落通过率，可以选取表面粗糙的填料添加在第一安全涂层中，从而提高第一安全涂层与胶带的剥离强度，提高锂离子电池的跌落通过率，具体地：
所述第一安全涂层包括填料，所述填料为钴酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、磷酸铁锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、富锂锰基材料、镍钴铝酸锂、钛酸锂、铝纤维和硅酸铝纤维中的一种或多种；本申请所选取的填料为本领域常见材料，具有稳定性高，不与电解液以及活性物质发生电化学反应的优点，同时上述材料易获得，具有经济效益和实际应用价值。
根据填料形状的不同，将填料进一步分为颗粒填料和纤维填料，其中，颗粒填料的粒径不宜过大，否则会影响第一安全涂层的致密性，进而影响锂离子电池的安全性，具体地，所述钴酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、磷酸铁锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、富锂锰基材料、镍钴铝酸锂和钛酸锂的D10为0.01-0.5μm，D50为0.02-1.5μm，D90为1.6-4.0μm，比表面积为0.1-15m 2/g；纤维填料的直径和长度也不宜过高，否则会影响第一安全涂层的厚度和致密性，此外，纤维长度过长也不利于纤维填料的分散，具体地，所述铝纤维和硅酸铝纤维的直径为0.1-3μm，长度为1-20μm。
通过进一步研究发现，随着第一安全涂层中填料的质量分数的不断增加，锂离子电池的穿刺通过率反而会降低，因此，为了兼顾锂离子电池的穿刺通过率和跌落通过率，所述填料的质量不大于所述第一安全涂层质量的40％。
进一步地，本申请测试了第一安全涂层与固定胶带之间的剥离强度，测试结果显示，第一安全涂层与固定胶带之间的剥离力为3-30N/m，当第一安 全涂层包括上述填料时，可进一步提高第一安全涂层与固定胶带之间的剥离力，提高锂离子电池的跌落通过率，提高安全性。
此外，热失控也是影响锂离子电池安全性的重要因素之一，为了进一步提高锂离子电池的安全性，第一安全涂层也可以包括导电剂，导电剂为本领域常见材料，其导热性能较好，当锂离子电池发生热失控时，导电剂可防止热量发生聚集，从而降低锂离子电池的局部温度，提高锂离子电池的安全性；此外，由于导电剂的粒径在纳米级别，比表面积高，孔隙多，可有效吸收锂离子电池电芯和外壳之间的电解液，提高电解液的注液效率，因此，在第一安全涂层中添加导电剂有助于防止锂离子电池内部温度的聚集，提高锂离子电池的安全性，但是，导电剂的含量不宜过高，否则会影响第一安全涂层的内阻，降低锂离子电池的穿刺通过率，因此，需对导电剂的含量进行控制，使得第一安全涂层和正极集流体的总体积内阻在10-3500mΩ，进一步地，第一安全涂层和正极集流体的总体积内阻在20-3500mΩ，总体积内阻是指第一安全涂层和正极集流体作为整体的体积内阻，测试使用ACCFILM膜片电阻测试系统进行电阻测试，将包含第一安全涂层的正极片放置于测试压头之间进行测试。
导电剂可以为本领域的常规材料，例如，导电剂为炭黑、碳纤维、碳纳米管、石墨、石墨烯、金属粉末、复合导电材料、导电陶瓷粉末中的一种或多种。
本领域技术人员可依据实际需要选择第一安全涂层的材料，例如，第一安全涂层包括无机粒子；或者包括无机粒子和导电剂；再或者包括无机粒子和填料；再或者包括无机粒子、填料和导电剂，此外，为了使第一安全涂层与正极集流体进行粘结，第一安全涂层中还包括粘结剂，具体地，所述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、羧甲基纤维素纳、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯、聚六氟丙烯、丁苯橡胶、聚醚砜、 聚酰亚胺、聚对苯二甲酸乙二醇酯、苯乙烯-丁二烯橡胶、苯乙烯-丙烯酸丁酯共聚物、丙烯酸改性SBR树脂、苯乙烯-(甲基)丙烯酸酯共聚物、聚乙烯醇、聚丙烯酸钠、聚偏二氟乙烯、聚酰胺酰亚胺、脱乙酰壳多糖、四氟乙烯-全氟烷基乙烯基醚共聚物、乙酸乙烯酯共聚物、邻苯二甲酸乙酸纤维素、羟丙基甲基纤维素、聚四氟乙烯中的一种或多种。
随着第一安全涂层厚度的不断增加，锂离子电池的安全性不断提高，但会导致能量密度的降低，因此，为了兼顾锂离子电池安全性和能量密度，所述第一安全涂层的厚度小于等于所述第二安全涂层的厚度。
进一步地，所述第一安全涂层的厚度为3-15μm。
本领域技术人员知晓，与第一安全涂层相比，第二安全涂层还需要参与电化学反应，因此，第二安全涂层中必须包括导电剂，且导电剂的含量应大于第一安全涂层中导电剂的含量，即第一安全涂层和第二安全涂层的材料不同，在正极片的制备过程中，需要分别配制第一安全涂层浆料、正极活性层浆料和第二安全涂层浆料，并将其分别涂布在正极集流体表面不同位置，因此，为了便于锂离子电池的制备，功能层和第一安全涂层之间可设置间隔，具体地，所述功能层与所述第一安全涂层之间的距离为d，0≤d≤10mm。
图3为本申请又一实施例提供的正极片的结构示意图，如图3所示，正极集流体101上表面或下表面的第二安全涂层103和正极活性层104与第一安全涂层102之间设置有间隔，并且二者之间的距离为d，正极集流体101上表面和下表面的距离d可以相同或不同，本领域技术人员可根据实际需要进行设置。
此外，本领域技术人员知晓，正极集流体表面应尽可能多的覆盖正极活性层，因此，正极活性层的长度通常略大于第二安全涂层的长度，因此，所述功能层与所述第一安全涂层之间的距离也就是正极活性层与第一安全涂层的距离，例如，图4为本申请又一实施例提供的正极片的结构示意图，如图4所示，正极活性层104的长度略大于第二安全涂层103的长度，功能层与 第一安全涂层的距离d也就是正极活性层104与第一安全涂层102的距离。
本领域技术人员可根据常规技术手段制备该正极片，具体地，分别制备得到第一安全涂层浆料、正极活性层浆料和第二安全涂层浆料，并采用凹版涂布、挤压涂布、喷涂、丝网印刷中的一种将上述浆料分别涂布在正极集流体上，制备得到正极片，其中：
正极集流体为铝箔；
第二安全涂层浆料中包括第一活性物质、粘结剂和导电剂，第一活性物质为钴酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、磷酸铁锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、富锂锰基材料、镍钴铝酸锂和钛酸锂中的一种或多种，D50为0.6-1.8μm，D90为2-10μm；
正极活性层浆料中包括第二正极活性物质、导电剂和粘结剂，第二活性物质为钴酸锂、镍钴锰酸锂、镍钴铝酸锂、富锂锰基材料、磷酸铁锂中的一种或多种，D50为7-15μm，D90小于等于25μm；
导电剂和粘结剂的选择同第一安全涂层。
第二安全涂层中第一活性物质的质量为第二安全涂层总质量的45-95％，进一步为47-94％，粘结剂的质量为第二安全涂层总质量的3-50％，导电剂的质量为第二安全涂层总质量的1-5％；
正极活性层中第二正极活性物质的质量为正极活性层总质量的93-98％、粘结剂的质量为正极活性层总质量的1-3％、导电剂的质量为正极活性层总质量的0.5-2％。
第二安全涂层的厚度为3-20μm；活性物质层的厚度为25μm以上。
综上，本申请提供了一种正极片，通过在正极集流体表面设置第一安全涂层，可有效阻止正极集流体与负极活性层接触，增加针刺过程中的短路内阻，阻止温度上升，提高锂离子电池的穿刺通过率。
本申请第二方面提供了一种锂离子电池，所述锂离子电池包括上述任一所述负极片。
本申请提供了一种锂离子电池，在本申请提供的正极片的基础上，与负极片、隔膜通过卷绕工艺制备得到卷芯，并经封装、注液后得到锂离子电池。本申请提供的锂离子电池具有较好的穿刺通过率。
为了进一步提高锂离子电池的能量密度，应尽可能降低无功能层覆盖的正极集流体的长度，具体地，覆盖在最外层正极集流体靠近卷绕中心内表面的第一安全涂层的长度小于等于所述最外层正极集流体的1/2。
继续参考图2，锂离子电池最左侧的正极集流体的上表面和下表面均无功能层覆盖，因此，这部分正极集流体的长度应尽可能减少，由于设置在最外层正极集流体靠近卷绕中心内表面的第一安全涂层的长度等于无功能层覆盖的正极集流体的长度，因此，设置在最外层正极集流体靠近卷绕中心内表面的第一安全涂层的长度小于最外层正极集流体的1/2。
此外，本领域技术人员知晓，为了增加负极片的储锂量，所述负极片的长度大于所述正极片的长度，因此，负极片与第一安全涂层在最外层正极片上的竖直投影必然会有部分重叠，具体地，所述负极片超出所述正极片的部分与第一安全涂层在最外层正极片的竖直投影的重叠区域大于等于0.5μm。
继续参考图2可知，负极片200的长度要大于正极片100的长度，且负极片200超出正极片100的部分(图2虚框中的部分)与第一安全涂层102在最外层正极片的竖直投影重叠，且重叠区域的长度大于等于0.5μm。
本申请的实施，至少具有以下优势：
1、本申请提供的正极片，通过在正极集流体表面设置第一安全涂层，可有效阻止正极集流体与负极活性层接触，增加针刺过程中的短路内阻，阻止温度上升，提高锂离子电池的穿刺通过率。
2、通过在第一安全涂层内添加填料，可进一步提高锂离子电池的跌落通过率，提高锂离子电池的安全性。
3、通过在第一安全涂层内添加导电剂，有助于防止锂离子电池内部温度 的聚集，提高锂离子电池的安全性。
4、本申请提供的锂离子电池具有较好的穿刺通过率。
附图说明
图1为本申请一实施例中提供的正极片的结构示意图；
图2为本申请一实施例中提供的锂离子电池的结构示意图；
图3为本申请又一实施例提供的正极片的结构示意图；
图4为本申请又一实施例提供的正极片的结构示意图。
附图标记说明：
100-正极片；
200-负极片；
300-正极耳；
400-负极耳；
101-正极集流体；
102-第一安全涂层；
103-第二安全涂层；
104-正极活性层。
具体实施方式
为使本申请的目的、技术方案和优点更加清楚，下面将结合本申请的实施例，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例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在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
以下实施例中所使用的材料均可商购得到。
实施例1
本实施例提供的正极片具有图1所示的结构，包括正极集流体铝箔、第一安全涂层、正极活性层和第二安全涂层，具体地：
第一安全涂层包括90质量份的三氧化二铝(Al 2O 3)和10质量份的聚偏氟乙烯(PVDF)，其中，三氧化二铝(Al 2O 3)的D10为0.15μm，D50为0.32μm，D90为0.65μm，比表面积为15.6m 2/g，第一安全涂层的单面厚度为5μm。
第二安全涂层包括65质量份的磷酸铁锂、30质量份的聚偏氟乙烯和5质量份的碳黑，磷酸铁锂的D50为0.75μm，D90为5.05μm，厚度为8μm；
正极活性层包括97质量份的钴酸锂、1.3质量份的聚偏氟乙烯和1.7质量份的碳黑，钴酸锂的D50为10μm，D90为25μm，厚度为95μm；
本实施例提供的正极片的制备方法包括如下步骤：
1、将90质量份的三氧化二铝(Al 2O 3)和10质量份的聚偏氟乙烯(PVDF)溶于NMP中混合均匀得到第一安全涂层浆料(固含为32.5％)；
采用凹版涂布机将第一安全涂层浆料涂布在铝箔上表面和下表面的第一涂覆区，经110℃烘干后，得到第一安全涂层；
2、将65质量份的磷酸铁锂、30质量份的聚偏氟乙烯和5质量份的碳黑溶于NMP中混合均匀得到第二安全涂层浆料(固含量为15％)；
采用凹版涂布机将第二安全涂层浆料涂布在铝箔上表面和下表面的第二涂覆区，经110℃烘干后，得到第二安全涂层；
3、将97质量份的钴酸锂、1.3质量份的聚偏氟乙烯和1.7质量份的碳黑溶于NMP中混合均匀形成正极活性层浆料(固含为75％)；
采用狭缝式挤压涂布设备将正极活性层浆料涂布于第二安全涂层表面，经100℃烘干后，经辊压分切成1000mm×65mm的正极片。
实施例2
本实施例提供的正极片可参考实施例1，区别在于：
第一安全涂层包括80质量份的三氧化二铝(Al 2O 3)、10质量份的LiFePO 4和10质量份的聚偏氟乙烯(PVDF)；
LiFePO 4的D10为0.37μm，D50为0.75μm，D90为2.30μm，比表面积为10m 2/g。
实施例3
本实施例提供的正极片可参考实施例2，区别在于：
第一安全涂层包括70质量份的三氧化二铝(Al 2O 3)、20质量份的LiFePO 4和10质量份的聚偏氟乙烯(PVDF)。
实施例4
本实施例提供的正极片可参考实施例2，区别在于：
第一安全涂层包括60质量份的三氧化二铝(Al 2O 3)、30质量份的LiFePO 4和10质量份的聚偏氟乙烯(PVDF)。
实施例5
本实施例提供的正极片可参考实施例1，区别在于：
第一安全涂层包括85质量份的三氧化二铝(Al 2O 3)、5质量份的铝纤维和10质量份的聚偏氟乙烯(PVDF)；
铝纤维的直径为2μm，长度为15μm。
实施例6
本实施例提供的正极片可参考实施例1，区别在于：
第一安全涂层包括85质量份的三氧化二铝(Al 2O 3)、5质量份的硅酸铝 纤维和10质量份的聚偏氟乙烯(PVDF)；
硅酸铝纤维的直径为2μm，长度为15μm。
实施例7
本实施例提供的正极片可参考实施例2，区别在于：
第一安全涂层包括80质量份的三氧化二铝(Al 2O 3)、10质量份的LiFePO 4、1.5质量份的导电剂炭黑和8.5质量份的聚偏氟乙烯(PVDF)。
实施例8
本实施例提供的正极片可参考实施例2，区别在于：
第一安全涂层包括80质量份的三氧化二铝(Al 2O 3)、10质量份的LiFePO 4、2.5质量份的导电剂炭黑和7.5质量份的聚偏氟乙烯(PVDF)。
实施例9
本实施例提供的正极片可参考实施例1，区别在于：
第一安全涂层包括78质量份的三氧化二铝(Al 2O 3)、2.5质量份的导电剂炭黑和19.5质量份的聚偏氟乙烯(PVDF)。
实施例10
本实施例提供的正极片可参考实施例1，区别在于：
第一安全涂层包括75.5质量份的三氧化二铝(Al 2O 3)、5质量份的导电剂炭黑和19.5质量份的聚偏氟乙烯(PVDF)。
实施例11
本实施例提供的正极片可参考实施例1，区别在于：
第一安全涂层包括70.5质量份的三氧化二铝(Al 2O 3)、10质量份的导电剂炭黑和19.5质量份的聚偏氟乙烯(PVDF)。
实施例12
本实施例提供的正极片可参考实施例1，区别在于：
第一安全涂层包括65.5质量份的三氧化二铝(Al 2O 3)、15质量份的导电剂炭黑和19.5质量份的聚偏氟乙烯(PVDF)。
实施例13
本实施例提供的正极片可参考实施例1，区别在于：
第一安全涂层包括60.5质量份的三氧化二铝(Al 2O 3)、20质量份的导电剂炭黑和19.5质量份的聚偏氟乙烯(PVDF)。
实施例14
本实施例提供的正极片可参考实施例1，区别在于：
第一安全涂层包括50.5质量份的三氧化二铝(Al 2O 3)、30质量份的导电剂炭黑和19.5质量份的聚偏氟乙烯(PVDF)。
实施例15
本实施例提供的正极片可参考实施例1，区别在于：
第一安全涂层包括79.5质量份的三氧化二铝(Al 2O 3)、1质量份的导电剂炭黑和19.5质量份的聚偏氟乙烯(PVDF)。
实施例16
本实施例提供的正极片可参考实施例1，区别在于：
第一安全涂层包括79.65质量份的三氧化二铝(Al 2O 3)、0.85质量份的导电剂炭黑和19.5质量份的聚偏氟乙烯(PVDF)。
实施例17
本实施例提供的正极片可参考实施例1，区别在于：
第一安全涂层包括79.85质量份的三氧化二铝(Al 2O 3)、0.65质量份的导电剂炭黑和19.5质量份的聚偏氟乙烯(PVDF)。
实施例18
本实施例提供的正极片可参考实施例1，区别在于：
第一安全涂层包括80质量份的三氧化二铝(Al 2O 3)、0.5质量份的导电剂炭黑和19.5质量份的聚偏氟乙烯(PVDF)。
对比例1
本对比例提供的正极片包括正极集流体、第二安全涂层和正极活性层，即不包括第一安全涂层。
对实施例1-18以及对比例1提供的正极片搭配负极片和隔膜经卷绕工艺制备得到锂离子电池，并对锂离子电池进行安全性测试，测试结果见表1：
其中，负极片的制备方法包括：将95质量份的石墨、1.5质量份的CMC、1.5质量份的SBR和2质量份的碳黑溶于去离子水中混合均匀，得到负极活性层浆料；将该浆料涂敷于铜箔的上表面和下表面，经70-100℃烘干2-5min后，辊压分切成1100mm×66.5mm的负极片，单面负极活性层的厚度为120μm。
(一)针刺测试方法包括：在常温环境下，将锂离子电池以0.5C恒流充电至电压为4.35V，然后恒压充电至电流为0.025C；将锂离子电池转移至穿钉测试设备上，保持测试环境温度为25℃，用直径为4mm的钢钉，以30mm/s的速度匀速穿过负极耳侧距电芯侧边7mm处，保留300s，锂离子电池不起火不爆炸记为通过。
每实施例/对比例测试10只，针刺测试通过率＝针刺通过电池数量/针刺总电池数。
(二)体积电阻测试方法包括：使用设备型号为ACCFILM膜片电阻测试系统对第一安全涂层和正极集流体的总体积电阻进行测试，测试压头直径D为14mm，测试时，将正极片放置于上下两个圆柱压头之间，调整压力为0.4MPa，启动测试开关，记录测试数据；每组测试10个数据点，测试点间距5mm，并取平均值作为体积电阻的数值。该测试系统的电阻测量精度为0.1μΩ-100mΩ，电阻测量范围为0.1μΩ-3000Ω。
(三)第一安全涂层与固定胶带的剥离强度测试方法包括：将正极片裁切成长度240mm、宽度30mm的正极片小片，使用NITTO No.5000NS胶带，将胶带按照长度200mm、宽度24mm的规格裁切成胶带小片，将胶带小片的一面粘在钢板(260mm*50mm)上，另一面与正极片小片粘结，保证正极片小片完全覆盖住胶带小片；使用手持滚筒(直径95mm，宽度45mm，重量2kg)往复滚动3次，将正极片小片与胶带小片粘结在一起，然后使用拉力机(拉力机型号东莞科建KJ-1065系列)测试(180度剥离)，然后以10mm/min的速度，测试设备自动记录随着剥离位移变化的拉力值，以剥离位移为横坐标，拉力值为纵坐标，作出拉力值随剥离位移变化的曲线，取曲线走平且剥离位移大于5mm时的拉力值为剥离强度。
(四)跌落测试
依据国标GB/T 18287-2000，将锂离子电池放置于夹具中，进行面跌落、棱跌落以及点跌落测试，测试距离1.2m，三维六个方向各个自由跌落1次。
每实施例/对比例测试10只，跌落测试通过率＝跌落通过电池数量/跌落总电池数。
(五)热滥用通过率
将满电电芯放入试验箱中，以(5±2)℃/min的速率提高试验箱内温度，当温度达到130±2℃后恒温1h，观察锂离子电池是否出现起火、爆炸问题，以不起火、不爆炸为通过。
表1 实施例1-18以及对比例1提供的锂离子电池的测试结果
Figure PCTCN2022082551-appb-000001
根据表1提供的数据可知，实施例1-8提供的锂离子电池的体积电阻和穿刺通过率大于对比例1，因此，设置第一安全涂层有利于提高锂离子电池的穿刺通过率；根据实施例1以及实施例2-4可知，第一安全涂层中包括颗粒填料有利于提高第一安全涂层和胶带之间的剥离力，从而提高锂离子电池的跌落通过率，但随着颗粒填料质量分数的提高，锂离子电池的穿刺通过率反而会下降，因此，当颗粒填料的质量分数为10％时，锂离子电池的综合安全性较好；根据实施例5-6可知，使用纤维填料后第一安全涂层和胶带之间 的剥离力提高，但由于铝纤维是纯导电性的，因此导致锂离子电池的穿刺通过率降低，而硅酸铝纤维的电绝缘性较好，体积电阻较大，具备较好的穿刺通过率；通过实施例7-8可知，第一安全涂层中添加适量导电剂也有利于防止锂离子电池内部温度的聚集，提高锂离子电池的安全性；根据实施例9-18可知，当第一安全涂层中包括导电剂时，应控制导电剂的含量，并控制集流体和第一安全涂层的总体积电阻在20-3500mΩ。
最后应说明的是：以上各实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述各实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围。

Claims (10)

  1. 一种正极片，其中，所述正极片包括正极集流体、功能层和第一安全涂层；
    其中，所述正极集流体的上表面和下表面均包括第一涂覆区和第二涂覆区，所述第一涂覆区上设置有所述第一安全涂层；所述第二涂覆区上设置有所述功能层，且所述功能层在远离所述正极集流体的方向上依次包括第二安全涂层和正极活性层。
  2. 根据权利要求1所述的正极片，其中，所述第一安全涂层包括无机粒子，所述无机粒子为CuO、Gd 2O、Lu 2O 3、Sm 2O 3、NiO、SiO 2、Al 2O 3、TiO 2、WO 3、ZnO、Ag 2Se、MoS 2、ZrO 2、Y 2O 3、SiC、CeO 2、SnO 2、Al 2O 3/Ag/ZnO、Al 2O 3/CdS、Al 2O 3/MgO、Al 2O 3/ZnO、Al(OH) 3、Mg(OH) 2、Ca(OH) 2、Ba 2SO 4、γ-AlOOH中的一种或多种。
  3. 根据权利要求1或2所述的正极片，其中，所述第一安全涂层包括填料，所述填料为钴酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、磷酸铁锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、富锂锰基材料、镍钴铝酸锂、钛酸锂、铝纤维和硅酸铝纤维中的一种或多种，所述填料的质量不大于所述第一安全涂层质量的40％。
  4. 根据权利要求3所述的正极片，其中，所述钴酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、磷酸铁锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、富锂锰基材料、镍钴铝酸锂和钛酸锂的D10为0.01-0.5μm，D50为0.02-1.5μm，D90为1.6-4.0μm，比表面积为0.1-15m 2/g；所述铝纤维和硅酸铝纤维的直径为0.1-3μm，长度为1-20μm。
  5. 根据权利要求1-4任一项所述的正极片，其中，所述第一安全涂层还包括导电剂，且所述第一安全涂层和正极集流体的总体积电阻为10-3500mΩ。
  6. 根据权利要求1所述的正极片，其中，所述第一安全涂层的厚度小于 等于所述第二安全涂层的厚度。
  7. 根据权利要求6所述的正极片，其中，所述第一安全涂层的厚度为3-15μm。
  8. 一种锂离子电池，其中，所述锂离子电池包括权利要求1-7任一项所述的正极片。
  9. 根据权利要求8所述的锂离子电池，其中，覆盖在最外层正极集流体靠近卷绕中心内表面的第一安全涂层的长度小于等于所述最外层正极集流体长度的1/2。
  10. 根据权利要求8或9所述的锂离子电池，其中，所述负极片的长度大于所述正极片的长度，且所述负极片超出所述正极片的部分与第一安全涂层在最外层正极片的竖直投影的重叠区域的长度大于等于0.5μm。
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