WO2024088339A1 - 一种电极组件和电池 - Google Patents

一种电极组件和电池 Download PDF

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Publication number
WO2024088339A1
WO2024088339A1 PCT/CN2023/126777 CN2023126777W WO2024088339A1 WO 2024088339 A1 WO2024088339 A1 WO 2024088339A1 CN 2023126777 W CN2023126777 W CN 2023126777W WO 2024088339 A1 WO2024088339 A1 WO 2024088339A1
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WIPO (PCT)
Prior art keywords
protective layer
positive electrode
electrode assembly
conductive material
region
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PCT/CN2023/126777
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English (en)
French (fr)
Inventor
张健
彭冲
李俊义
陈瑶
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珠海冠宇电池股份有限公司
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Publication of WO2024088339A1 publication Critical patent/WO2024088339A1/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
    • 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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • H01M4/64—Carriers or collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/572—Means for preventing undesired use or discharge
    • H01M50/584—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries
    • H01M50/586—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries inside the batteries, e.g. incorrect connections of electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • 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 disclosure relates to an electrode assembly and a battery, and to the technical field of batteries.
  • the battery includes an electrode assembly that can carry out electrochemical reactions and a casing that seals the electrode assembly.
  • an electrode assembly that can carry out electrochemical reactions
  • a casing that seals the electrode assembly.
  • the most common short circuit situations include: short circuit between the positive current collector and the negative current collector, short circuit between the positive current collector and the negative active material layer, short circuit between the positive active material layer and the negative current collector, and short circuit between the positive active material layer and the negative active material layer.
  • the short circuit between the positive current collector and the negative active material layer generates the fastest heat, is most likely to cause thermal runaway, and has a greater safety hazard.
  • the present disclosure provides an electrode assembly for solving the problem that a short circuit is easily generated between a positive electrode current collector and a negative electrode active material layer when the battery encounters mechanical abuse, thereby improving the safety of the battery.
  • the first aspect of the present disclosure provides an electrode assembly, the electrode assembly comprising a wound positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector, a first protective layer and a positive electrode active material layer, wherein:
  • the positive electrode current collector includes a first surface close to the winding center and a second surface away from the winding center, the second surface includes a first region and a second region, the first surface and the first region are provided with the first protective layer and the positive electrode active material layer, and the first protective layer is located between the positive electrode active material layer and the positive electrode current collector, and the second region is provided with the first protective layer;
  • the first protection layer includes a conductive material and an adhesive.
  • the positive electrode sheet further includes a second protective layer, the first protective layer and the second protective layer are sequentially stacked on the second region, and the second protective layer includes an inorganic material and Binder.
  • the thickness of the first protective layer disposed in the first region is less than or equal to the thickness of the first protective layer disposed in the second region.
  • the difference between the thickness of the first protective layer disposed in the first region and the thickness of the first protective layer disposed in the second region is 0 ⁇ m-10 ⁇ m.
  • the conductive material includes a first conductive material and/or a second conductive material
  • the first conductive material includes one or more of SnO2 , In2O3 , Sb-doped SnO2 , F-doped SnO2 , Sn -doped In2O3 , and Al-doped ZnO
  • the second conductive material includes a base particle and a coating layer coated on the surface of the base particle, the base particle is one or more of aluminum oxide, magnesium oxide, titanium oxide, zinc oxide, silicon oxide, boehmite, cobalt oxide, iron phosphate, lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium iron manganese phosphate
  • the coating layer includes one or more of carbon, SnO2 , In2O3 , Sb-doped SnO2 , F-doped SnO2 , Sn -doped In2O3 , and Al-doped ZnO.
  • the Dv50 of the conductive material is 0.05 ⁇ m-5 ⁇ m.
  • the resistivity of the conductive material is 0.01 ⁇ m-1 ⁇ m.
  • the mass of the conductive material is 40%-98% of the total mass of the first protective layer.
  • the resistivity of the inorganic material is greater than 10 4 ⁇ cm.
  • the second application of the present disclosure provides a battery, comprising any of the electrode assemblies described above.
  • the present disclosure provides an electrode assembly, which reduces the empty foil area on the surface of the positive electrode collector by arranging a first protective layer on the surface of the positive electrode collector and at least covers the positive electrode collector located at the outermost circle of the electrode assembly, thereby reducing the short circuit risk between the positive electrode collector and the negative electrode active material layer and improving the safety of the battery; at the same time, the first protective layer includes a conductive material, which can take into account the conductivity of the positive electrode sheet and improve the cycle performance of the battery.
  • the present disclosure can further improve the safety of the battery by providing a second protective layer including an inorganic material on the surface of the first protective layer.
  • the battery provided by the present disclosure includes the above-mentioned electrode assembly and has good safety and cycle performance.
  • FIG1 is a schematic diagram of the structure of an electrode assembly provided by the prior art
  • FIG2 is a schematic diagram of the structure of a positive electrode sheet provided by the prior art
  • FIG3 is a schematic structural diagram of an electrode assembly provided in one embodiment of the present disclosure.
  • FIG4 is a schematic diagram of the structure of a positive electrode sheet provided in one embodiment of the present disclosure.
  • FIG5 is a top view of the second surface of the positive electrode current collector provided in one embodiment of the present disclosure.
  • FIG6 is a schematic diagram of the structure of a positive electrode sheet provided in another embodiment of the present disclosure.
  • FIG. 7 is a schematic diagram of the structure of a positive electrode plate provided in yet another embodiment of the present disclosure.
  • FIG. 1 is a schematic diagram of the structure of an electrode assembly provided by the prior art
  • Figure 2 is a schematic diagram of the structure of a positive electrode sheet provided by the prior art.
  • the electrode assembly includes a positive electrode sheet and a negative electrode sheet wound from the inside to the outside, and a diaphragm (not shown in the figure) is provided between the positive electrode sheet and the negative electrode sheet to prevent a short circuit between the two.
  • the diaphragm ruptures, which can easily lead to a short circuit between the positive electrode sheet and the negative electrode sheet, causing thermal runaway, and posing a safety hazard to the use of the battery.
  • the inside of the electrode assembly is used as the winding starting point, and the electrode sheet is wound from the inside to the outside along the length direction, and the end position is the winding end point.
  • Figures 1-2 it can be seen that there are a large number of empty foil areas on the surface of the positive electrode collector 101 near the winding end point.
  • the positive electrode collector 101 located on the outer circle of the electrode assembly is very likely to short-circuit with the negative electrode active material layer 202, which is most likely to cause thermal runaway and is a safety weak area.
  • the present disclosure provides a first protective layer on both surfaces of the positive electrode current collector, so that it covers the surface of the positive electrode current collector and at least covers the positive electrode current collector located at the outermost circle of the electrode assembly, thereby effectively reducing the short circuit risk between the positive electrode current collector and the negative electrode active material layer and improving the safety of the battery; in addition, the present disclosure selects conductive materials and binders as the composition of the first protective layer, which effectively takes into account the conductivity of the positive electrode sheet and the cycle performance of the battery on the basis of improving the safety of the battery.
  • FIG. 3 is a schematic diagram of the structure of an electrode assembly provided in an embodiment of the present disclosure
  • FIG. 4 is a schematic diagram of the structure of a positive electrode sheet provided in an embodiment of the present disclosure
  • FIG. 5 is a top view of the second surface of a positive current collector provided in an embodiment of the present disclosure. As shown in FIGS.
  • the electrode assembly includes a positive electrode sheet wound from the inside to the outside, and the positive electrode sheet includes a positive current collector 101, a first protective layer 103, and a positive active material layer 102, wherein the positive current collector 101 includes a first surface a and a second surface b that are parallel and opposite to each other, the first surface a is a surface close to the winding center, the second surface b is a surface away from the winding center, and the second surface Surface b includes a first region c and a second region d, and the first surface a and the first region c are provided with a first protective layer 103 and a positive electrode active material layer 102, and the first protective layer 103 is located between the positive electrode active material layer 102 and the positive electrode collector 101, that is, the first protective layer 103 and the positive electrode active material layer 102 are sequentially stacked on the first surface a and the first region c of the second surface b of the positive electrode collector 101, and the second region d is provided with the first protective layer
  • the lengths of the first protective layer 103 and the positive electrode active material layer 102 arranged on the first surface a and the first region c can be determined according to the winding method of the electrode assembly.
  • the lengths of the first protective layer 103 and the positive electrode active material layer 102 arranged on the first surface a and the first region c are the same.
  • the focus of the present disclosure is to completely cover the second region d of the second surface b that is not covered with the positive electrode active material layer 102 with the first protective layer 103, so that the first protective layer 103 arranged on the second surface b completely covers the positive electrode collector 101 of the outermost circle of the electrode assembly, specifically the second surface of the outermost circle positive electrode collector away from the winding center, so as to reduce the short circuit risk between the positive electrode collector and the negative electrode active material layer and improve the safety of the battery.
  • the first protective layer 103 includes a conductive material and a binder.
  • the conductive material can act as a filler.
  • the conductive material can act as a barrier to prevent short circuits between the burrs generated by the positive electrode collector and the negative electrode active material layer.
  • it can play a conductive role, and its construction forms a good conductive network, so that the first protective layer battery maintains stable conductivity during the charge and discharge process, and improves the cycle performance of the battery.
  • the binder plays a bonding role, and can bond the conductive materials, the first protective layer and the positive electrode collector, and the first protective layer and the positive electrode active material layer to each other.
  • the first protective layer 103 is composed of a conductive material and a binder, and does not include non-conductive materials (such as ceramic particles); it helps to take into account the conductivity of the positive electrode sheet and the cycle performance of the battery on the basis of improving the safety performance of the battery. It is understandable that the first protective layer 103 may contain conventional functional additives in the art, such as leveling agents, solvents, and thickeners, and the content of the functional additives in the protective layer is less than 0.1% by weight; that is, the first protective layer 103 is composed of a conductive material, a binder, and a functional additive, and does not include non-conductive materials.
  • the present disclosure provides an electrode assembly, which reduces the empty foil area on the surface of the positive electrode collector by setting a first protective layer on the surface of the positive electrode collector and at least covers the positive electrode collector located at the outermost circle of the electrode assembly, thereby reducing the short circuit risk between the positive electrode collector and the negative electrode active material layer, and improving the safety of the battery; at the same time, the first protective layer includes a conductive material, which can take into account the conductivity of the positive electrode sheet and improve the cyclability of the battery able.
  • the thickness of the first protective layer 103 is 1 ⁇ m-10 ⁇ m, for example, 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 3 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m or a range composed of any two of them. Further, the thickness of the first protective layer 103 is 2 ⁇ m-5 ⁇ m.
  • Figure 6 is a schematic diagram of the structure of the positive electrode plate provided in another embodiment of the present disclosure. As shown in Figure 6, in order to further improve the protective effect of the first protective layer 103 on the electrode assembly, the thickness of the first protective layer 103 arranged on the first area c is less than or equal to the thickness of the first protective layer 103 arranged on the second area d.
  • the difference between the thickness of the first protective layer 103 arranged in the first area c and the thickness of the first protective layer 103 arranged in the second area d is 0 ⁇ m-10 ⁇ m, for example, 0 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 3 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m or a range consisting of any two of them.
  • the peeling force between the first protective layer 103 and the positive current collector 101 should be greater than the peeling force between the first protective layer 103 and the positive active material layer 102.
  • the first protective layer 103 is not easy to fall off from the surface of the positive current collector 101, resulting in failure.
  • the binder content in the first protective layer 103 can be increased to be greater than the binder content in the positive active material layer 102, or the adhesion of the binder in the first protective layer 103 can be increased to be stronger than the adhesion of the binder in the positive active material layer 102.
  • the resistance of the first protective layer is 0.01 ⁇ -2 ⁇ (for example, 0.01 ⁇ , 0.05 ⁇ , 0.1 ⁇ , 0.3 ⁇ , 0.5 ⁇ , 0.7 ⁇ , 1 ⁇ , 1.3 ⁇ , 1.5 ⁇ , 1.7 ⁇ , 2 ⁇ ), and the resistance refers to the resistance in the thickness direction of the first protective layer, which can be obtained by testing with a volume resistance meter, wherein the probe diameter of the detector is 15mm.
  • the conductive material includes a first conductive material and/or a second conductive material, wherein the first conductive material includes SnO 2 , In 2 O 3 , Sb-doped SnO 2 (ATO), F-doped SnO 2 (FTO), One or more of Sn-doped In 2 O 3 (ITO), Al-doped ZnO;
  • the second conductive material comprises a base particle and a coating layer coated on the surface of the base particle, the base particle is one or more of aluminum oxide, magnesium oxide, titanium oxide, zinc oxide, silicon oxide, boehmite, cobalt oxide, iron phosphate, lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium iron manganese phosphate;
  • the coating layer comprises one or more of carbon, SnO 2 , In 2 O 3 , Sb-doped SnO 2 , F-doped SnO 2 , Sn-doped In 2 O 3 , and Al-doped Zn
  • the conductive material is preferably a second conductive material
  • the base particles are one or more of aluminum oxide, magnesium oxide, titanium oxide, zinc oxide, silicon oxide, boehmite, cobalt oxide, and iron phosphate
  • the coating layer is Sb-doped SnO2 , wherein the mass of the coating layer is 5%-40% (for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%) of the total mass of the second conductive material.
  • the Dv50 of the conductive material is 0.05 ⁇ m-5 ⁇ m, for example, 0.05 ⁇ m, 0.10 ⁇ m, 0.15 ⁇ m, 0.20 ⁇ m, 0.50 ⁇ m, 1.0 ⁇ m, 2.0 ⁇ m, 5.0 ⁇ m or a range consisting of any two of them; further, the Dv50 of the conductive material is 0.1 ⁇ m-1 ⁇ m, and Dv50 refers to the particle size corresponding to 50% of the volume distribution of the conductive material, which can be obtained by detection with a particle size analyzer. By limiting the particle size of the conductive material, it can be better adhered to the positive electrode collector, thereby improving the protective effect of the protective layer on the positive electrode collector, and taking into account the thickness limitation of the protective layer and the processing difficulty of the pole piece.
  • the resistivity of the conductive material is 0.01 ⁇ m-1 ⁇ m, for example, 0.01 ⁇ m, 0.02 ⁇ m, 0.05 ⁇ m, 0.10 ⁇ m, 0.20 ⁇ m, 0.25 ⁇ m, 0.50 ⁇ m, 1 ⁇ m or a range consisting of any two of them. Selecting a conductive material with a suitable resistivity can effectively ensure the resistance of the protective layer and improve the conductive performance of the positive electrode sheet.
  • the mass of the conductive material is 40%-98% (for example, 40%, 50%, 60%, 70%, 80%, 90%, 98%) of the total mass of the first protective layer 103. If the content of the conductive material is too low, the conductive material cannot play a protective role on the positive electrode collector, affecting the conductivity of the positive electrode sheet.
  • the binder can be a conventional binder in the art, specifically including one or more of polyvinylidene fluoride, acrylic acid-modified polyvinylidene fluoride, polyacrylate, polyimide, styrene-butadiene rubber, and styrene-propylene rubber.
  • the mass of the binder is 2%-60% (for example, 2%, 5%, 10%, 20%, 30%, 40%, 50%, 60%) of the total mass of the protective layer.
  • FIG7 is a schematic diagram of the structure of a positive electrode sheet provided by another embodiment of the present disclosure.
  • the positive electrode sheet further includes a second protective layer 104, which is disposed on the surface of the first protective layer 103 located in the second region d, that is, the first protective layer 103 and the second protective layer 104 are sequentially stacked on the second region d, and the second protective layer 104 includes an inorganic material and a binder.
  • the thickness of the first protective layer 103 disposed in the first region c and the second region d can be the same.
  • the second protective layer includes an inorganic material and a binder.
  • the resistivity of the inorganic material is greater than 10 4 ⁇ cm.
  • the inorganic material is one or more of aluminum oxide, boehmite, silicon oxide, titanium oxide, calcium carbonate, barium sulfate, and barium carbonate.
  • the mass of the inorganic material is 60%-95% (for example, 60%, 70%, 80%, 90%, 95%) of the total mass of the second protective layer.
  • the binder can be the same as that in the first protective layer 103.
  • the positive electrode active material layer 102 includes a positive electrode active material, a conductive agent and a binder.
  • the positive electrode active material is one or more of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide
  • the conductive agent includes one or more of conductive carbon black, carbon nanotubes, conductive graphite, and graphene
  • the binder includes one or more of polyvinylidene fluoride (PVDF), acrylic modified PVDF, polyacrylate polymers, polyimide, styrene-butadiene rubber, and styrene-acrylic rubber.
  • PVDF polyvinylidene fluoride
  • the positive electrode plate also includes a positive electrode tab 300, which serves as a conductor for connecting the positive electrode plate to an external circuit and can be configured according to conventional technical means in the art, which will not be elaborated in detail in the present disclosure.
  • the preparation method of the positive electrode plate includes the following steps: first, preparing a first protective layer slurry and a positive active material layer slurry respectively.
  • the preparation method of the first protective layer slurry includes: mixing a conductive material and a binder according to a certain proportion and dispersing them in a solvent, and adjusting the solid content to prepare the first protective layer slurry;
  • the preparation method of the positive active material layer slurry includes: mixing a positive active material, a conductive agent and a binder according to a certain proportion and dispersing them in a solvent, and adjusting the solid content to prepare the positive active material layer slurry; then, coating the first protective layer slurry on the first surface and the second surface of the positive current collector to obtain a first protective layer, and then coating the prepared positive active material layer slurry on the surface of the protective layer away from the positive current collector to obtain the positive active material layer, and finally, welding the pole ear on the surface of the positive current collector to obtain the positive electrode plate.
  • the thickness of the first protective layer in the second region is greater than the thickness of the first protective layer in the first region
  • a layer of the first protective layer slurry is further coated on the surface of the first protective layer not coated with the positive electrode active material layer slurry, so that the thickness of the first protective layer in the second region is greater than the thickness of the first protective layer in the first region; or, it can also be achieved by gravure coating, specifically, the second region
  • the mesh number of the gravure roller corresponding to the first domain is less than the mesh number of the gravure roller corresponding to the first region.
  • the positive electrode plate includes a second protective layer
  • the electrode assembly also includes a negative electrode sheet and a separator formed by winding from the inside to the outside.
  • the separator is located between the positive electrode sheet and the negative electrode sheet.
  • the negative electrode sheet includes a negative electrode collector 201, a negative electrode active material layer 202 and a negative electrode tab 400.
  • the negative electrode sheet and the separator are conventional materials in the field. Those skilled in the art can select appropriate materials according to actual needs and obtain the electrode assembly by winding through a winding process.
  • the present disclosure provides an electrode assembly, which reduces the empty foil area on the surface of the positive electrode collector by setting a first protective layer on the surface of the positive electrode collector and at least covers the positive electrode collector located at the outermost circle of the electrode assembly, thereby reducing the short circuit risk between the positive electrode collector and the negative electrode active material layer and improving the safety of the battery; at the same time, the first protective layer includes a conductive material, which can take into account the conductivity of the positive electrode sheet and improve the cycle performance of the battery.
  • a second aspect of the present disclosure provides a battery, comprising the electrode assembly described in any one of the above items.
  • the electrode assembly provided in the first aspect of the present disclosure is sealed in a battery housing and injected with electrolyte, and then a battery can be obtained after conventional processes such as formation.
  • the battery provided in the present disclosure includes the above-mentioned electrode assembly, and thus has good safety performance and cycle performance.
  • the electrode assembly provided in this embodiment has a structure as shown in FIG3 , including a positive electrode sheet and a negative electrode sheet wound from the inside to the outside, and the positive electrode sheet has a structure as shown in FIG4 , including a positive electrode current collector aluminum foil, a first protective layer and a positive electrode active material layer, wherein:
  • the first protective layer includes 95 parts by mass of a second conductive material and 5 parts by mass of polyvinylidene fluoride PVDF, the second conductive material includes base particles TiO 2 , the coating layer includes Sb-doped SnO 2 , the mass ratio of the base particles to the coating layer is 9:1, wherein the resistivity of the conductive material is 0.20 ⁇ m;
  • the positive electrode active material layer includes 96 parts by mass of lithium cobalt oxide, 1 part by mass of carbon black, 1 part by mass of carbon nanotubes, and 2 parts by mass of polyvinylidene fluoride PVDF.
  • the negative electrode sheet includes a negative electrode current collector copper foil and a negative electrode active material layer arranged on the surface of the negative electrode current collector copper foil, and the negative electrode active material layer includes 96 parts by mass of artificial graphite, 1 part by mass of carbon black, 1.5 parts by mass of styrene-butadiene rubber and 1.5 parts by mass of sodium carboxymethyl cellulose.
  • the thickness of the first protective layer located on the first surface/second surface of the positive electrode current collector aluminum foil is 3 ⁇ m.
  • Step 1 Mix the second conductive material and polyvinylidene fluoride (PVDF) according to the above mass fractions and disperse them in a solvent NMP, adjust the solid content to 40%, and prepare a first protective layer slurry.
  • PVDF polyvinylidene fluoride
  • Step 2 Mix lithium cobalt oxide, carbon black, carbon nanotubes and PVDF according to the above mass fractions and disperse them in a solvent NMP, adjust the solid content to 70%, and prepare a positive electrode active material layer slurry.
  • Step 3 coating the first protective layer slurry prepared in step 1 on the first surface and the second surface of the positive electrode current collector aluminum foil to obtain a protective layer, and then coating the positive electrode active material layer slurry prepared in step 2 on the surface of the protective layer away from the positive electrode current collector, and drying to obtain a positive electrode sheet;
  • Step 4 artificial graphite, carbon black, styrene-butadiene rubber and sodium carboxymethyl cellulose are mixed according to the above mass fractions and dispersed in a solvent of deionized water, and the solid content is adjusted to 40% to prepare a negative electrode active material layer slurry; the prepared negative electrode active material layer slurry is coated on the surface of the negative electrode current collector copper foil, and the negative electrode sheet is obtained after drying;
  • Step 5 Use a roller press to roll the positive electrode sheet and the negative electrode sheet to a designed thickness, use a slitting machine to cut the positive electrode sheet and the negative electrode sheet to a designed width, and then weld the positive electrode tab and the negative electrode tab on the positive electrode sheet and the negative electrode sheet respectively;
  • Step 6 Place the separator between the positive electrode sheet and the negative electrode sheet, wind them as shown in FIG3 to obtain an electrode assembly, and fix them with glue.
  • the electrode assembly provided in this embodiment can refer to Example 1, except that the structure of the positive electrode plate is shown in Figure 6, the thickness of the first protective layer located in the first area of the second surface of the positive electrode collector is 2 ⁇ m, and the thickness of the protective layer in the second area is 5 ⁇ m, see Table 1 for details.
  • the electrode assembly provided in this embodiment can refer to Embodiment 2, except that the thickness of the protective layer in the second region is 8 ⁇ m, see Table 1 for details.
  • the electrode assembly provided in this embodiment can refer to Embodiment 2, except that the thickness of the protective layer in the second region is 10 ⁇ m, see Table 1 for details.
  • the electrode assembly provided in this embodiment can refer to Example 2, except that the structure of the positive electrode plate is as shown in Figure 7, the thickness of the first protective layer is 2 ⁇ m, the thickness of the second protective layer is 3 ⁇ m, that is, the total thickness of the protective layer arranged in the second area of the second surface of the positive electrode collector is 5 ⁇ m, and the second protective layer includes 95 parts by mass of aluminum oxide and 5 parts by mass of PVDF, see Table 1 for details.
  • the electrode assembly provided in this embodiment can refer to Example 2, except that the structure of the positive electrode plate is shown in Figure 7, the thickness of the first protective layer is 2 ⁇ m, the thickness of the second protective layer is 6 ⁇ m, that is, the total thickness of the protective layer arranged in the second area of the second surface of the positive electrode collector is 8 ⁇ m, see Table 1 for details.
  • the electrode assembly provided in this embodiment can refer to Example 2, except that the structure of the positive electrode plate is shown in Figure 7, the thickness of the first protective layer is 2 ⁇ m, the thickness of the second protective layer is 8 ⁇ m, that is, the total thickness of the protective layer arranged in the second area of the second surface of the positive electrode collector is 10 ⁇ m, see Table 1 for details.
  • the electrode assembly provided in this embodiment can refer to the embodiment 1, except that the first protective layer includes the first conductive material SnO 2 , see Table 1 for details.
  • the electrode assembly provided in this embodiment group can refer to the embodiment 1, except that the proportion of the mass of the coating layer in the second conductive material is changed, as follows:
  • the electrode assembly provided in this embodiment can refer to Example 1, except that the mass of the coating layer is 5% of the total mass of the second conductive material, wherein the resistivity of the resulting conductive material is 0.28 ⁇ m.
  • the electrode assembly provided in this embodiment can refer to Example 1, except that the mass of the coating layer is 20% of the total mass of the second conductive material, wherein the resistivity of the resulting conductive material is 0.13 ⁇ m.
  • the electrode assembly provided in this embodiment can refer to Example 1, except that the mass of the coating layer is 30% of the total mass of the second conductive material, wherein the resistivity of the obtained conductive material is 0.06 ⁇ m.
  • the electrode assembly provided in this embodiment can refer to Embodiment 1, except that the mass of the coating layer is 40% of the total mass of the second conductive material, wherein the resistivity of the obtained conductive material is 0.02 ⁇ m;
  • the electrode assembly provided in this embodiment group can refer to the embodiment 1, except that the type of the base particles or the type of the coating layer is changed, as follows:
  • the electrode assembly provided in this embodiment group can refer to embodiment 1, except that the base particles are lithium iron phosphate;
  • the electrode assembly provided in this embodiment group can refer to embodiment 1, except that the coating layer is carbon;
  • the electrode assembly provided in this comparative example can refer to Example 2, except that the thickness of the protective layer in the second region is 1 ⁇ m, see Table 1 for details.
  • the electrode assembly provided in this comparative example can refer to Example 2, except that the thickness of the protective layer in the second region is 2 ⁇ m, see Table 1 for details.
  • the electrode assembly provided in this comparative example can refer to Example 1, except that the conductive material includes mixed TiO 2 and Sb-doped SnO 2 , and the mass ratio of the two is 9:1. See Table 1 for details.
  • the electrode assembly provided in this comparative example can refer to Example 1, except that the first protective layer is not provided in the second region of the second surface of the positive electrode current collector, see Table 1 for details.
  • the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer arranged on the surface of the positive electrode current collector, but does not include a first protective layer and a second protective layer.
  • a first protective layer and a second protective layer For details, see Table 1.
  • the electrode assemblies provided in Examples 1-13 and Comparative Examples 1-2 were packaged with aluminum-plastic films and then baked until the water The electrolyte was injected into the battery to obtain a lithium-ion battery. The battery was then tested for safety.
  • the test method is as follows. The test results are shown in Table 2:
  • Needle penetration test prepare 30 identical lithium-ion batteries, fully charge the lithium-ion batteries, put them on the test bench of the needle penetration test equipment, and pierce the middle of the lithium-ion battery with a tungsten steel needle with a diameter of 3mm and a needle tip length of 3.62mm at a speed of 100mm/s.
  • the lithium-ion battery is considered to have passed the test if it does not catch fire or explode, and it is considered to have failed if the battery catches fire or explodes.
  • the result is expressed as "pass quantity/test quantity”. For example, if the test quantity is 30 and the pass quantity is 28, the result is expressed as "28/30".
  • 45°C cycle test At 45°C, the lithium-ion battery is charged and discharged at 1.5C charge/0.5C discharge, and the discharge capacity Q2 of the 500th charge and discharge and the discharge capacity Q1 of the first charge and discharge are recorded.
  • the capacity retention rate Q2/Q1 ⁇ 100%.

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Abstract

本公开提供一种电极组件和电池。本公开第一方面提供一种电极组件，包括卷绕成形的正极极片，正极极片包括正极集流体、第一保护层和正极活性物质层，其中：正极集流体包括靠近卷绕中心的第一表面和远离卷绕中心的第二表面，所述第二表面包括第一区域和第二区域，所述第一表面和第一区域设置有所述第一保护层和正极活性物质层，且所述第一保护层位于所述正极活性物质层和正极集流体之间，所述第二区域设置有所述第一保护层；第一保护层包括导电材料和粘结剂。本公开提供一种电极组件，能够兼顾电池的安全性和循环性能。

Description

一种电极组件和电池 技术领域
本公开涉及一种电极组件和电池，涉及电池技术领域。
发明背景
电池包括能够进行电化学反应的电极组件和密封该电极组件的外壳，当电池遇到如针刺、挤压等机械滥用情况下，电极组件内部会发生较严重的短路，导致电池失效并发生热失控，给电池的使用造成安全隐患。
其中，最常见的短路情况包括：正极集流体与负极集流体之间发生短路、正极集流体与负极活性物质层之间发生短路、正极活性物质层与负极集流体之间发生短路、正极活性物质层与负极活性物质层之间发生短路，其中，正极集流体与负极活性物质层之间发生短路时的产热最快，最容易引发热失控，安全隐患较大。
发明内容
本公开提供一种电极组件，用于解决当电池遇到机械滥用时，正极集流体与负极活性物质层之间容易发生短路的问题，提高电池的安全性。
本公开第一方面提供一种电极组件，所述电极组件包括卷绕成形的正极极片，所述正极极片包括正极集流体、第一保护层和正极活性物质层，其中：
所述正极集流体包括靠近卷绕中心的第一表面和远离卷绕中心的第二表面，所述第二表面包括第一区域和第二区域，所述第一表面和第一区域设置有所述第一保护层和正极活性物质层，且所述第一保护层位于所述正极活性物质层和正极集流体之间，所述第二区域设置有所述第一保护层；
所述第一保护层包括导电材料和粘结剂。
在一种具体实施方式中，所述正极极片还包括第二保护层，所述第一保护层和第二保护层依次层叠设置在所述第二区域上，所述第二保护层包括无机材料和 粘结剂。
在一种具体实施方式中，设置在所述第一区域的第一保护层的厚度小于等于设置在所述第二区域的第一保护层的厚度。
在一种具体实施方式中，设置在所述第一区域的第一保护层的厚度与设置在所述第二区域的第一保护层的厚度的差值为0μm-10μm。
在一种具体实施方式中，所述导电材料包括第一导电材料和/或第二导电材料，所述第一导电材料包括SnO2、In2O3、掺Sb的SnO2、掺F的SnO2、掺Sn的In2O3、掺Al的ZnO中的一种或多种；所述第二导电材料包括基体颗粒以及包覆在所述基体颗粒表面的包覆层，所述基体颗粒为氧化铝、氧化镁、氧化钛、氧化锌、氧化硅、勃姆石、氧化钴、磷酸铁、磷酸铁锂、镍钴锰酸锂、磷酸铁锰锂中的一种或多种，所述包覆层包括碳、SnO2、In2O3、掺Sb的SnO2、掺F的SnO2、掺Sn的In2O3、掺Al的ZnO中的一种或多种。
在一种具体实施方式中，所述导电材料的Dv50为0.05μm-5μm。
在一种具体实施方式中，所述导电材料的电阻率为0.01Ω·m-1Ω·m。
在一种具体实施方式中，所述导电材料的质量为所述第一保护层总质量的40％-98％。
在一种具体实施方式中，所述无机材料的电阻率＞104Ω·cm。
本公开第二申请提供一种电池，包括上述任一所述的电极组件。
本公开的实施，至少具有以下优势：
1、本公开提供一种电极组件，通过在正极集流体表面设置第一保护层，并至少覆盖位于电极组件最外圈的正极集流体，从而降低正极集流体表面的空箔区，降低正极集流体与负极活性物质层之间的短路风险，提高电池的安全性；同时第一保护层中包括导电材料，能够兼顾正极极片的导电性，提高电池的循环性能。
2、本公开通过在第一保护层表面设置包括无机材料的第二保护层，能够进一步提高电池的安全性。
3、本公开提供的电池包括上述电极组件，具备较好的安全性和循环性能。
附图说明
为了更清楚地说明本公开实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作一简单地介绍，显而易见地，下面描述中的附图是本公开的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动性的前提下，还可以根据这些附图获得其他的附图。
图1为现有技术提供的电极组件的结构示意图；
图2为现有技术提供的正极极片的结构示意图；
图3为本公开一实施例提供的电极组件的结构示意图；
图4为本公开一实施例提供的正极极片的结构示意图；
图5为本公开一实施例提供的正极集流体第二表面的俯视图；
图6为本公开又一实施例提供的正极极片的结构示意图；
图7为本公开再一实施例提供的正极极片的结构示意图。
附图标记说明：
101-正极集流体；
a-第一表面；
b-第二表面；
c-第一区域；
d-第二区域；
102-正极活性物质层；
103-第一保护层；
104-第二保护层；
201-负极集流体；
202-负极活性物质层；
300-正极极耳；
400-负极极耳。
具体实施方式
为使本公开的目的、技术方案和优点更加清楚，下面将结合本公开的实施例，对本公开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公开一部分实施例，而不是全部的实施例。基于本公开中的实施例，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，都属于本公开保护的范围。
图1为现有技术提供的电极组件的结构示意图，图2为现有技术提供的正极极片的结构示意图，如图1-2所示，电极组件包括由内向外卷绕成形的正极极片和负极极片，正极极片和负极极片之间设置有隔膜(图中未示出)，用于防止二者之间发生短路，但当电池遇到机械滥用的情况时，隔膜发生破裂，容易导致正极极片和负极极片之间的短路，引发热失控，给电池的使用造成安全隐患。
根据极片的卷绕方式，本公开中以电极组件内部为卷绕起点，沿极片长度方向由内向外卷绕成形，收尾位置即为卷绕终点，根据图1-2可以看出，靠近卷绕终点的正极集流体101表面存在大量的空箔区，当电池发生机械滥用时，位于电极组件外圈的正极集流体101极易与负极活性物质层202之间发生短路，最容易引发热失控，是安全的薄弱区域。
基于上述分析，本公开在正极集流体的两个表面均设置第一保护层，使其覆盖在正极集流体表面，且至少覆盖位于电极组件最外圈的正极集流体，有效降低了正极集流体与负极活性物质层之间的短路风险，提高了电池的安全性；此外，本公开选择导电材料和粘结剂作为第一保护层的组成，在提高电池的安全性的基础上，有效兼顾了正极极片的导电性和电池的循环性能。
在一种具体实施方式中，图3为本公开一实施例提供的电极组件的结构示意图，图4为本公开一实施例提供的正极极片的结构示意图，图5为本公开一实施例提供的正极集流体第二表面的俯视图，如图3-5所示，电极组件包括由内向外卷绕成形的正极极片，正极极片包括正极集流体101、第一保护层103和正极活性物质层102，其中，正极集流体101包括平行且相对的第一表面a和第二表面b，第一表面a为靠近卷绕中心的表面，第二表面b为远离卷绕中心的表面，第二表 面b包括第一区域c和第二区域d，第一表面a和第一区域c设置有第一保护层103和正极活性物质层102，且第一保护层103位于正极活性物质层102和正极集流体101之间，即第一保护层103和正极活性物质层102依次层叠设置在正极集流体101的第一表面a和第二表面b的第一区域c上，第二区域d设置有第一保护层103。
设置在第一表面a和第一区域c上的第一保护层103和正极活性物质层102的长度可以根据电极组件的卷绕方式决定，第一表面a和第一区域c上设置的第一保护层103和正极活性物质层102的长度相同，本公开的重点在于将第二表面b未覆盖正极活性物质层102的第二区域d全部覆盖第一保护层103，使得设置在第二表面b的第一保护层103完全覆盖电极组件最外圈的正极集流体101，具体为最外圈正极集流体远离卷绕中心的第二表面，以降低正极集流体与负极活性物质层之间的短路风险，提高电池的安全性。
为了兼顾正极极片的导电性，第一保护层103包括导电材料和粘结剂，导电材料一方面能够起到填充物的效果，在电池遇到针刺和异物挤压等机械滥用时，导电材料能够起到阻隔的作用，防止正极集流体产生的毛刺与负极活性物质层之间发生短路，另一方面能够起到导电的效果，其构建形成良好的导电网络，从而使第一保护层电池在充放电过程中保持稳定的导电能力，提高电池的循环性能，而粘结剂起粘结的作用，能够将导电材料之间、第一保护层与正极集流体之间、第一保护层与正极活性物质层之间相互粘结。
在一种优选实施例中，第一保护层103由导电材料和粘结剂组成，不包括非导电材料(例如陶瓷颗粒)；有助于在提高电池安全性能的基础上，兼顾正极极片的导电性以及电池的循环性能。可以理解的是，第一保护层103中可以含有本领域常规的功能性助剂，例如流平剂、溶剂、增稠剂，在所述保护层中所述功能性助剂的含量在0.1重量％以下；即第一保护层103由导电材料、粘结剂和功能性助剂组成，不包括非导电材料。
因此，本公开提供一种电极组件，通过在正极集流体表面设置第一保护层，并至少覆盖位于电极组件最外圈的正极集流体，从而降低正极集流体表面的空箔区，降低正极集流体与负极活性物质层之间的短路风险，提高电池的安全性；同时第一保护层中包括导电材料，能够兼顾正极极片的导电性，提高电池的循环性 能。
可以理解，随着第一保护层103厚度的提高，当电池发生机械滥用时，对正极集流体101的保护作用也就越好，但随着第一保护层103厚度的提高，容易影响电池的能量密度，因此，为了兼顾电池的安全性和能量密度，第一保护层103的厚度为1μm-10μm，例如1μm、1.5μm、2μm、3μm、5μm、8μm、10μm或其中的任意两者组成的范围，进一步地，第一保护层103的厚度为2μm-5μm。
图6为本公开又一实施例提供的正极极片的结构示意图，如图6所示，为了进一步提高第一保护层103对电极组件的保护效果，设置在第一区域c上的第一保护层103的厚度小于等于设置在第二区域d上的第一保护层103的厚度。
进一步地，为了兼顾电池的能量密度，设置在所述第一区域c的第一保护层103的厚度与设置在第二区域d的第一保护层103的厚度的差值为0μm-10μm，例如0μm、0.5μm、1μm、1.5μm、2μm、3μm、5μm、8μm、10μm或其中的任意两者组成的范围。
为了进一步提高第一保护层103对正极集流体101的保护作用，所述第一保护层103与所述正极集流体101之间的剥离力应大于所述第一保护层103与所述正极活性物质层102之间的剥离力，当电池发生机械滥用时，第一保护层103不易从正极集流体101表面脱落，导致失效；具体地，可以提高第一保护层103中粘结剂含量，使其大于正极活性物质层102中粘结剂含量，或者，也可以提高第一保护层103中粘结剂的粘结性，使其强于正极活性物质层102中粘结剂的粘结性。
为了兼顾正极极片的导电性，所述第一保护层的电阻为0.01Ω-2Ω(例如，0.01Ω、0.05Ω、0.1Ω、0.3Ω、0.5Ω、0.7Ω、1Ω、1.3Ω、1.5Ω、1.7Ω、2Ω)，电阻是指第一保护层厚度方向的电阻，可通过体电阻仪测试得到，其中，探测仪的探头直径为15mm，测试过程中，首先测试正极集流体101的体电阻，记为R1，再测试第一保护层+正极集流体的极片体电阻，记为R2，则第一保护层厚度方向的体电阻R＝R2-R1；进一步地，第一保护层的电阻为0.1Ω-1Ω，例如0.1Ω、0.2Ω、0.3Ω、0.35Ω、0.4Ω、0.5Ω、0.8Ω、1Ω或其中的任意两者组成的范围。
在一种具体实施方式中，所述导电材料包括第一导电材料和/或第二导电材料，所述第一导电材料包括SnO2、In2O3、掺Sb的SnO2(ATO)、掺F的SnO2(FTO)、 掺Sn的In2O3(ITO)、掺Al的ZnO中的一种或多种；所述第二导电材料包括基体颗粒以及包覆在所述基体颗粒表面的包覆层，所述基体颗粒为氧化铝、氧化镁、氧化钛、氧化锌、氧化硅、勃姆石、氧化钴、磷酸铁、磷酸铁锂、镍钴锰酸锂、磷酸铁锰锂中的一种或多种，所述包覆层包括碳、SnO2、In2O3、掺Sb的SnO2、掺F的SnO2、掺Sn的In2O3、掺Al的ZnO中的一种或多种，掺杂和包覆方法均可采用本领域常规技术手段，包覆层的质量为第二导电材料总质量的5％-40％(例如，5％、10％、15％、20％、25％、30％、35％、40％)，否则，包覆层含量过低，容易影响导电材料的导电效果，进而对电池循环性能造成影响。
进一步地，导电材料优选第二导电材料，更进一步地，基体颗粒为氧化铝、氧化镁、氧化钛、氧化锌、氧化硅、勃姆石、氧化钴、磷酸铁中的一种或多种，包覆层为掺Sb的SnO2，其中，包覆层的质量为第二导电材料总质量的5％-40％(例如，5％、10％、15％、20％、25％、30％、35％、40％)。
进一步地，所述导电材料的Dv50为0.05μm-5μm，例如0.05μm、0.10μm、0.15μm、0.20μm、0.50μm、1.0μm、2.0μm、5.0μm或其中的任意两者组成的范围；更进一步地，所述导电材料的Dv50为0.1μm-1μm，Dv50是指导电材料的体积分布中50％所对应的粒度，可以根据粒度分析仪检测得到，通过限定导电材料的粒度，能够使其更好地附着在正极集流体上，提高保护层对正极集流体的保护作用，并且能够兼顾保护层的厚度限制以及极片的加工难度。
进一步地，所述导电材料的电阻率为0.01Ω·m-1Ω·m，例如0.01Ω·m、0.02Ω·m、0.05Ω·m、0.10Ω·m、0.20Ω·m、0.25Ω·m、0.50Ω·m、1Ω·m或其中的任意两者组成的范围，选择合适电阻率的导电材料，能够有效保证保护层的电阻，提高正极极片的导电性能。
进一步地，所述导电材料的质量为所述第一保护层103总质量的40％-98％(例如，40％、50％、60％、70％、80％、90％、98％)，导电材料含量过低，则无法发挥导电材料对正极集流体的保护作用，影响正极极片的导电性。
所述粘结剂可以为本领域常规粘结剂，具体包括聚偏氟乙烯、丙烯酸改性的聚偏氟乙烯、聚丙烯酸酯、聚酰亚胺、丁苯橡胶、苯丙橡胶中的一种或多种，粘结剂的质量为保护层总质量的2％-60％(例如，2％、5％、10％、20％、30％、40％、50％、60％)。
图7为本公开再一实施例提供的正极极片的结构示意图，如图7所示，正极极片还包括第二保护层104，第二保护层104设置在位于第二区域d的第一保护层103的表面，即第一保护层103和第二保护层104依次层叠设置在第二区域d上，第二保护层104包括无机材料和粘结剂。此时，设置在第一区域c和第二区域d的第一保护层103的厚度可以相同。
第二保护层包括无机材料和粘结剂，无机材料的电阻率＞104Ω·cm，例如，无机材料为氧化铝、勃姆石、氧化硅、氧化钛、碳酸钙、硫酸钡、碳酸钡中的一种或多种，无机材料的质量为第二保护层总质量的60％-95％(例如，60％、70％、80％、90％、95％)，粘结剂可以和第一保护层103中的相同。
正极活性物质层102包括正极活性物质、导电剂和粘结剂，以锂离子电池为例，正极活性物质为钴酸锂、镍钴锰酸锂、镍钴铝酸锂、磷酸铁锂、锰酸锂中的一种或多种；导电剂包括导电炭黑、碳纳米管、导电石墨、石墨烯中的一种或多种；粘结剂包括聚偏氟乙烯(PVDF)、丙烯酸改性PVDF、聚丙烯酸酯类聚合物、聚酰亚胺、丁苯橡胶、苯丙橡胶中的一种或多种。
正极极片还包括正极极耳300，作为正极极片与外界电路导通的导电体，可以根据本领域常规技术手段进行设置，本公开在此不再进行详细阐述。
本公开提供的正极极片的制备方法包括如下步骤：首先，分别制备得到第一保护层浆料和正极活性物质层浆料，具体的，第一保护层浆料的制备方法包括：将导电材料和粘结剂按照一定的比例混合并分散在溶剂中，调整固体含量后制备得到第一保护层浆料；正极活性物质层浆料的制备方法包括：将正极活性物质、导电剂和粘结剂按照一定的比例混合并分散在溶剂中，调整固体含量后制备得到正极活性物质层浆料；接着，将第一保护层浆料涂覆在正极集流体的第一表面和第二表面，得到第一保护层，再将制备得到的正极活性物质层浆料涂覆在保护层远离正极集流体的表面，得到正极活性物质层，最后，在正极集流体表面焊接极耳后得到正极极片。
当位于第二区域的第一保护层的厚度大于位于第一区域的第一保护层的厚度时，可在制备得到正极活性物质层后，在未涂覆正极活性物质层浆料的第一保护层表面继续涂覆一层第一保护层浆料，使第二区域的第一保护层的厚度大于位于第一区域的第一保护层的厚度；或者，也可以通过凹版涂布实现，具体为第二区 域对应的凹版辊目数小于第一区域对应的凹版辊目数。
当正极极片包括第二保护层时，则需要制备得到第二保护层浆料，并在未涂覆正极活性物质层浆料的第一保护层表面涂覆第二保护层浆料，得到第二保护层。
电极组件还包括由内向外卷绕成形的负极极片和隔膜，隔膜位于正极极片和负极极片之间，负极极片包括负极集流体201、负极活性物质层202和负极极耳400，负极极片和隔膜均为本领域常规材料，本领域技术人员可根据实际需要选择合适的材料，并通过卷绕工艺卷绕得到该电极组件。
综上，本公开提供一种电极组件，通过在正极集流体表面设置第一保护层，并至少覆盖位于电极组件最外圈的正极集流体，从而降低正极集流体表面的空箔区，降低正极集流体与负极活性物质层之间的短路风险，提高电池的安全性；同时第一保护层中包括导电材料，能够兼顾正极极片的导电性，提高电池的循环性能。
本公开第二方面提供一种电池，所述电池包括上述任一项所述的电极组件。
将本公开第一方面提供的电极组件密封在电池外壳内并注入电解液，经化成等常规工序后即可得到电池。本公开提供的电池包括上述电极组件，因而具有较好的安全性能和循环性能性能。
以下结合具体实施例进行详细阐述：
实施例1
本实施例提供的电极组件具有如图3所示的结构，包括由内向外卷绕成形的正极极片和负极极片，正极极片具有如图4所示的结构，包括正极集流体铝箔、第一保护层和正极活性物质层，其中：
第一保护层包括95质量份的第二导电材料和5质量份的聚偏氟乙烯PVDF，第二导电材料包括基体颗粒TiO2，包覆层包括掺Sb的SnO2，基体颗粒与包覆层的质量比为9:1，其中导电材料的电阻率为0.20Ω·m；
正极活性物质层包括96质量份的钴酸锂、1质量份的炭黑、1质量份的碳纳米管和2质量份的聚偏氟乙烯PVDF。
负极极片包括负极集流体铜箔和设置在负极集流体铜箔表面的负极活性物质层，负极活性物质层包括96质量份的人造石墨、1质量份的炭黑、1.5质量份的丁苯橡胶和1.5质量份的羧甲基纤维素钠。
位于正极集流体铝箔第一表面/第二表面的第一保护层的厚度均为3μm。
本实施例提供的电极组件的制备方法包括如下步骤：
步骤1、将第二导电材料和聚偏氟乙烯PVDF按照上述质量分数混合并分散在溶剂NMP中，调整固含为40％，制备得到第一保护层浆料。
步骤2、将钴酸锂、炭黑、碳纳米管和PVDF按照上述质量分数混合并分散在溶剂NMP中，调整固含至70％，制备得到正极活性物质层浆料。
步骤3、将步骤1制备得到的第一保护层浆料涂覆在正极集流体铝箔的第一表面和第二表面，得到保护层，再将步骤2制备得到的正极活性物质层浆料涂覆在保护层远离正极集流体的表面，烘干后得到正极极片；
步骤4、将人造石墨、炭黑、丁苯橡胶和羧甲基纤维素钠按照上述质量分数混合并分散在溶剂去离子水，调整固含至40％，制备得到负极活性物质层浆料；将制备得到负极活性物质层浆料涂覆在负极集流体铜箔的表面上，烘干后得到负极极片；
步骤5、使用辊压机将正极极片和负极极片辊压到设计厚度，使用分条机将正极极片和负极极片至设计宽度，然后在正极极片和负极极片上分别焊接正极极耳和负极极耳；
步骤6、将隔膜放在正极极片和负极极片中间，按照图3所示的方式进行卷绕，得到电极组件，并贴胶固定。
实施例2
本实施例提供的电极组件可参考实施例1，区别在于，正极极片的结构如图6所示，位于正极集流体第二表面第一区域的第一保护层的厚度为2μm，第二区域的保护层的厚度为5μm，具体参见表1。
实施例3
本实施例提供的电极组件可参考实施例2，区别在于，第二区域的保护层的厚度为8μm，具体参见表1。
实施例4
本实施例提供的电极组件可参考实施例2，区别在于，第二区域的保护层的厚度为10μm，具体参见表1。
实施例5
本实施例提供的电极组件可参考实施例2，区别在于，正极极片的结构如图7所示，第一保护层的厚度为2μm，第二保护层的厚度为3μm，即设置在正极集流体第二表面第二区域的保护层总厚度为5μm，第二保护层包括95质量份的氧化铝和5质量份的PVDF，具体参见表1。
实施例6
本实施例提供的电极组件可参考实施例2，区别在于，正极极片的结构如图7所示，第一保护层的厚度为2μm，第二保护层的厚度为6μm，即设置在正极集流体第二表面第二区域的保护层总厚度为8μm，具体参见表1。
实施例7
本实施例提供的电极组件可参考实施例2，区别在于，正极极片的结构如图7所示，第一保护层的厚度为2μm，第二保护层的厚度为8μm，即设置在正极集流体第二表面第二区域的保护层总厚度为10μm，具体参见表1。
实施例8
本实施例提供的电极组件可参考实施例1，区别在于，第一保护层包括第一导电材料SnO2，具体参见表1。
实施例9组
本实施例组提供的电极组件可参考实施例1，区别在于，改变包覆层的质量在第二导电材料中的占比，具体如下：
实施例9a
本实施例提供的电极组件可参考实施例1，区别在于，包覆层的质量为第二导电材料总质量的5％，其中，所得导电材料的电阻率为0.28Ω·m。
实施例9b
本实施例提供的电极组件可参考实施例1，区别在于，包覆层的质量为第二导电材料总质量的20％，其中，所得导电材料的电阻率为0.13Ω·m。
实施例9c
本实施例提供的电极组件可参考实施例1，区别在于，包覆层的质量为第二导电材料总质量的30％，其中，所得导电材料的电阻率为0.06Ω·m。
实施例9d
本实施例提供的电极组件可参考实施例1，区别在于，包覆层的质量为第二导电材料总质量的40％，其中，所得导电材料的电阻率为0.02Ω·m；
具体参见表1。
实施例10组
本实施例组提供的电极组件可参考实施例1，区别在于，改变基体颗粒的种类或包覆层的种类，具体如下：
实施例10a
本实施例组提供的电极组件可参考实施例1，区别在于，基体颗粒为磷酸铁锂；
实施例10b
本实施例组提供的电极组件可参考实施例1，区别在于，包覆层为碳；
具体参见表1。
实施例11
本对比例提供的电极组件可参考实施例2，区别在于，第二区域的保护层的厚度为1μm，具体参见表1。
实施例12
本对比例提供的电极组件可参考实施例2，区别在于，第二区域的保护层的厚度为2μm，具体参见表1。
实施例13
本对比例提供的电极组件可参考实施例1，区别在于，导电材料包括混合的TiO2和掺Sb的SnO2，二者的质量比为9:1，具体参见表1。
对比例1
本对比例提供的电极组件可参考实施例1，区别在于，正极集流体第二表面第二区域未设置第一保护层，具体参见表1。
对比例2
本对比例提供的电极组件如图1所示，即正极极片包括正极集流体和设置在正极集流体表面的正极活性物质层，不包括第一保护层和第二保护层，具体参见表1。
表1

将实施例1-13与对比例1-2提供的电极组件使用铝塑膜封装，随后烘烤至水 分合格，注入电解液，得到锂离子电池，随后对电池进行安全性测试，测试方法如下，测试结果见表2：
针刺测试：制备30只相同的锂离子电池，将锂离子电池充满电，将其放入针刺测试设备的测试台上，将直径为3mm，针尖长度为3.62mm的钨钢针，以100mm/s的速度刺穿锂离子电池中间，锂离子电池不起火、不爆炸视为测试通过，电池起火或爆炸视为未通过，其结果用“通过量/测试量”表示，例如，测试量为30，通过量为28，则结果用“28/30”表示。
异物挤压测试：制备30只相同的锂离子电池，将锂离子电池充满电，将其放入挤压设备的测试台上，将M2*4(螺杆直径为2mm，螺杆长度为4mm)的螺丝置于电池中间，然后启动挤压设备，挤压板以100mm/s的速度下压，当其挤压力达到13KN停止测试，电池不起火、不爆炸视为测试通过，电池起火或爆炸视为未通过，其结果用“通过量/测试量”表示，例如，测试量为30，通过量为28，则结果用“28/30”表示。
45℃循环测试：在45℃下，使锂离子电池以1.5C充电/0.5C放电进行充放电，记录其第500次充放电的放电容量Q2与第1次的充放电的放电容量Q1，容量保持率＝Q2/Q1×100％。
表2

最后应说明的是：以上各实施例仅用以说明本公开的技术方案，而非对其限制；尽管参照前述各实施例对本公开进行了详细的说明，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公开各实施例技术方案的范围。

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  1. 一种电极组件，其中，所述电极组件包括卷绕成形的正极极片，所述正极极片包括正极集流体、第一保护层和正极活性物质层，其中：
    所述正极集流体包括靠近卷绕中心的第一表面和远离卷绕中心的第二表面，所述第二表面包括第一区域和第二区域，所述第一表面和第一区域设置有所述第一保护层和正极活性物质层，且所述第一保护层位于所述正极活性物质层和正极集流体之间，所述第二区域设置有所述第一保护层；
    所述第一保护层包括导电材料和粘结剂。
  2. 根据权利要求1所述的电极组件，其中，所述第一保护层由导电材料、粘结剂和功能性助剂组成。
  3. 根据权利要求1或2所述的电极组件，其中，所述正极极片还包括第二保护层，所述第一保护层和第二保护层依次层叠设置在所述第二区域上，所述第二保护层包括无机材料和粘结剂。
  4. 根据权利要求1-3中任一项所述的电极组件，其中，所述第一保护层的厚度为1μm-10μm；
    和/或，设置在所述第一区域的第一保护层的厚度小于等于设置在所述第二区域的第一保护层的厚度。
  5. 根据权利要求1-4中任一项所述的电极组件，其中，设置在所述第一区域的第一保护层的厚度与设置在所述第二区域的第一保护层的厚度的差值为0μm-10μm。
  6. 根据权利要求1-5中任一项所述的电极组件，其中，所述第一保护层与所述正极集流体之间的剥离力应大于所述第一保护层与所述正极活性物质层之间的剥离力。
  7. 根据权利要求1-6中任一项所述的电极组件，其中，所述第一保护层的电阻为0.01Ω-2Ω，优选为0.1Ω-1Ω。
  8. 根据权利要求1-7中任一项所述的电极组件，其中，所述导电材料包括第一导电材料和/或第二导电材料，所述第一导电材料包括SnO2、In2O3、掺Sb的SnO2、掺F的SnO2、掺Sn的In2O3、掺Al的ZnO中的一种或多种；所述第二导 电材料包括基体颗粒以及包覆在所述基体颗粒表面的包覆层，所述基体颗粒为氧化铝、氧化镁、氧化钛、氧化锌、氧化硅、勃姆石、氧化钴、磷酸铁、磷酸铁锂、镍钴锰酸锂、磷酸铁锰锂中的一种或多种，所述包覆层包括碳、SnO2、In2O3、掺Sb的SnO2、掺F的SnO2、掺Sn的In2O3、掺Al的ZnO中的一种或多种；
    和/或，包覆层的质量为第二导电材料总质量的5％-40％。
  9. 根据权利要求1-8中任一项所述的电极组件，其中，导电材料包括第二导电材料，基体颗粒为氧化铝、氧化镁、氧化钛、氧化锌、氧化硅、勃姆石、氧化钴、磷酸铁中的一种或多种，包覆层为掺Sb的SnO2。
  10. 根据权利要求1-9中任一项所述的电极组件，其中，所述导电材料的Dv50为0.05μm-5μm，优选为0.1μm-1μm。
  11. 根据权利要求1-10中任一项所述的电极组件，其中，所述导电材料的电阻率为0.01Ω·m-1Ω·m。
  12. 根据权利要求1-11中任一项所述的电极组件，其中，所述导电材料的质量为所述第一保护层总质量的40％-98％。
  13. 根据权利要求3-12中任一项所述的电极组件，其中，所述无机材料的电阻率＞104Ω·cm；
    和/或，无机材料为氧化铝、勃姆石、氧化硅、氧化钛、碳酸钙、硫酸钡、碳酸钡中的一种或多种。
  14. 根据权利要求3-13中任一项所述的电极组件，其中，无机材料的质量为第二保护层总质量的60％-95％。
  15. 一种电池，其中，所述电池包括权利要求1-14任一项所述的电极组件。
PCT/CN2023/126777 2022-10-26 2023-10-26 一种电极组件和电池 WO2024088339A1 (zh)

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