WO2023050230A1 - 电极极片及包含其的二次电池 - Google Patents

电极极片及包含其的二次电池 Download PDF

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WO2023050230A1
WO2023050230A1 PCT/CN2021/121955 CN2021121955W WO2023050230A1 WO 2023050230 A1 WO2023050230 A1 WO 2023050230A1 CN 2021121955 W CN2021121955 W CN 2021121955W WO 2023050230 A1 WO2023050230 A1 WO 2023050230A1
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Prior art keywords
inorganic
isolation layer
layer
pore
electrode sheet
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PCT/CN2021/121955
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English (en)
French (fr)
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王曦童
唐代春
杜鑫鑫
喻鸿钢
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宁德时代新能源科技股份有限公司
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Priority to EP21944415.5A priority Critical patent/EP4184701A4/en
Priority to CN202180088008.6A priority patent/CN116686153A/zh
Priority to PCT/CN2021/121955 priority patent/WO2023050230A1/zh
Priority to US18/105,725 priority patent/US20230223660A1/en
Publication of WO2023050230A1 publication Critical patent/WO2023050230A1/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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • 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
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • 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
    • H01M4/62—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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • 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
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • 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
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/446—Composite material consisting of a mixture of organic and inorganic 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
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • 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
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
    • 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
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of batteries, in particular to electrode pole pieces and secondary batteries containing them, battery modules, battery packs and electrical devices.
  • the separator plays the role of isolating the positive and negative electrodes and allowing lithium ion conduction, which is an important part of the battery.
  • polyolefin separator materials with microporous structure are mainly used in commercially available secondary batteries, such as single-layer or multi-layer films of polyethylene (PE) and polypropylene (PP).
  • PE polyethylene
  • PP polypropylene
  • Polyolefin separators can provide sufficient mechanical strength and chemical stability for secondary batteries, but exhibit large thermal shrinkage under high temperature conditions. Such heat shrinkage leads to contact and short circuit of the positive and negative electrodes, thus causing safety accidents such as fire, combustion and even explosion.
  • a pore-forming method is likely to introduce new impurities or consume a large amount of energy during the pore-forming process (for example, when sintering pore-forming, the sintering temperature can be as high as 700 ° C or more), and the high temperature environment is harmful to Components contained in the electrode active material layer, such as binders and additives, may cause adverse effects.
  • pores can be formed by adding a substance that generates gas when conventionally heated (for example, a substance that decomposes when heated) to a layer to be pore-formed.
  • a substance that generates gas when conventionally heated for example, a substance that decomposes when heated
  • the generated gas will form large bubbles during the escape process, and the bubbles will squeeze the inorganic particles on both sides of the gap away during the escape process through the gap between the inorganic particles.
  • forming a wedge-shaped channel In this way, a channel for lithium ions to penetrate can be formed, thereby improving the ion conductivity of the inorganic isolation layer.
  • the inventors of the present application found through further research that the shape and size of the pores are not easy to control.
  • the shape and size of each hole formed are not uniform, which easily leads to non-uniform mechanical properties of the inorganic separation layer, thus easily causing defects such as cracks when pressing or winding the electrode pole piece, thus easily causing electrode safety and reduction in capacity.
  • the thickness of the inorganic separation layer is prepared to be relatively thin in order to increase the mass energy density, the above-mentioned inorganic separation layer with wedge-shaped channels is prone to self-discharge due to the large opening at one end of the channels, and it is also more likely A short circuit has occurred.
  • the inventors of the present application have accomplished the present invention in order to solve the above-mentioned problems.
  • an electrode pole piece includes a current collector and an active material layer disposed on at least one surface of the current collector,
  • a first inorganic isolation layer and a second inorganic isolation layer are sequentially formed on the active material layer
  • the first inorganic isolation layer contains a plurality of channels and the pore diameter of the channels is 300nm-600nm,
  • Each of the plurality of channels extends from the first inorganic isolation layer toward the second inorganic isolation layer and penetrates the second inorganic isolation layer, and
  • the pore diameters of the channels in the second inorganic isolation layer are uniform.
  • the manufacturing cost of the battery can be greatly reduced; compared with the technology of using a non-porous inorganic separator as a separator, this implementation
  • the method can significantly increase the mass energy density of the battery by forming through pores in the inorganic separator, and significantly improve the ion conductivity of the inorganic separator, thereby significantly reducing the impedance of the battery; in addition, compared with the technology with wedge-shaped pores
  • by forming a plurality of channels each extending from the first inorganic spacer layer toward the second inorganic spacer layer and penetrating through the second inorganic spacer layer with a pore diameter of 300 nm to 600 nm it is possible to avoid This leads to problems such as uneven mechanical properties of the inorganic separator, self-discharge or even short-circuit of the battery.
  • the sum of the thicknesses of the first inorganic isolation layer and the second inorganic isolation layer is 7 ⁇ m to 30 ⁇ m, thereby improving the mass energy density of the battery and ensuring insulation.
  • the thickness of the first inorganic spacer layer is 2 ⁇ m to 10 ⁇ m, so that it is easy to form
  • the inorganic isolation layer has a plurality of channels with relatively uniform pore diameters of 300nm to 600nm.
  • the porosity of the first inorganic separation layer and the second inorganic separation layer are each 40% to 55%, which can improve the mass energy density of the battery, ensure insulation and excellent Mechanical behavior.
  • each of the first inorganic isolation layer and the second inorganic isolation layer includes inorganic particles and a binder, thereby improving the self-discharge rate and impedance of the battery.
  • the first inorganic isolation layer includes 90% to 95% by weight of inorganic particles and 5% to 10% by weight of binder
  • the second inorganic isolation layer includes 95% to 98% by weight of inorganic particles and 2% to 5% by weight of binder. Thus, the mechanical performance and insulation of the electrode pole piece can be improved.
  • the volume median particle diameter Dv50 of the inorganic particles is 30nm-500nm, thereby increasing the mass energy density of the battery and improving the ion conductivity of the electrode sheet.
  • the inorganic particles include at least one selected from the group consisting of silicon oxide, aluminum oxide, boehmite, magnesium oxide, titanium oxide, zinc oxide, and aluminum magnesium oxide.
  • the binder includes carboxymethyl cellulose, polyvinylidene fluoride, styrene-butadiene rubber, polyimide, polyethylene, polyvinylidene fluoride-hexafluoropropylene copolymer At least one of the group consisting of objects.
  • the electrode sheet is a positive electrode sheet or a negative electrode sheet.
  • a secondary battery which includes the electrode sheet of the above-mentioned first embodiment. Since the secondary battery includes the electrode tab of the first embodiment described above, the secondary battery has excellent mass energy density and low self-discharge rate and impedance.
  • a battery module including the secondary battery of the second embodiment above.
  • the battery module has excellent mass energy density and low self-discharge rate and impedance.
  • a battery pack which includes the battery module of the above third embodiment.
  • the battery pack has excellent mass energy density and low self-discharge rate and impedance.
  • an electric device which includes at least one of the secondary battery of the second embodiment, the battery module of the third embodiment, or the battery pack of the fourth embodiment.
  • the electric device has excellent mass energy density and low self-discharge rate and impedance.
  • a method for preparing an electrode sheet comprising the following steps:
  • step (e) heat-treating the product obtained after step (d) at the pore-forming temperature of the pore-forming agent to obtain The electrode pole piece of the second inorganic separation layer
  • the first inorganic isolation layer comprises a plurality of channels and the pore diameter of the channels is 300nm-600nm,
  • Each of the plurality of channels extends from the first inorganic isolation layer toward the second inorganic isolation layer and penetrates the second inorganic isolation layer, and
  • the pore diameters of the channels in the second inorganic isolation layer are uniform.
  • a secondary battery including the electrode tab of the present embodiment can have excellent mass energy density and low self-discharge rate and impedance.
  • the first inorganic particles, the first binder, the first dispersant and the pore-forming agent in the slurry for forming the first inorganic isolation layer The content of each is 35% by weight to 45% by weight, 1% by weight to 4% by weight, 45% by weight to 55% by weight, 5% by weight to 10% by weight, and
  • the contents of the second inorganic particles, the second binder and the second dispersant in the slurry for forming the second inorganic isolation layer are respectively 40% by weight to 55% by weight, and 1% by weight % to 5% by weight, 40% to 55% by weight.
  • the electrode tab including the first inorganic separator layer and the second inorganic separator layer of this embodiment can be easily manufactured.
  • the method further comprises the step of pressing after step (a) and/or step (e).
  • step (e) By pressing the active material layer or the inorganic isolation layer, the volume of the electrode sheet can be reduced, thereby increasing the mass energy density of the battery.
  • the sum of the thicknesses of the first inorganic isolation layer and the second inorganic isolation layer is 7 ⁇ m to 30 ⁇ m.
  • the thickness of the first inorganic isolation layer is 2 ⁇ m ⁇ 10 ⁇ m.
  • the porosity of the first inorganic isolation layer and the second inorganic isolation layer is 40%-55% respectively.
  • the volume median particle diameter Dv50 of the first inorganic particle and the second inorganic particle may be 30nm ⁇ 500nm, respectively.
  • the mass energy density of the battery can be increased and the ion conductivity of the electrode sheet can be improved.
  • each of the first dispersant and the second dispersant comprises a compound selected from the group consisting of water, methanol, ethanol, n-propanol, isopropanol, acetone, and N-methylpyrrolidone. at least one of .
  • the pore former includes at least one selected from the group consisting of ammonium carbonate and ammonium bicarbonate.
  • the present application provides an electrode pole piece, which can significantly increase the mass energy density of the battery by forming through holes with relatively uniform pore diameters in the inorganic separation layer, and significantly improve the ion conductivity of the inorganic separation layer, Thereby significantly reducing the impedance of the battery; in addition, compared with the technology with wedge-shaped pores, the electrode tabs extend from the first inorganic separator layer toward the second inorganic separator layer and penetrate through the second inorganic separator layer by forming
  • the inorganic isolation layer and multiple channels with a pore size of 300nm to 600nm can avoid problems such as uneven mechanical properties of the inorganic isolation layer, self-discharge or even short circuit of the battery caused by wedge-shaped channels.
  • the secondary battery comprising the above-mentioned electrode sheet of the present application has excellent mass energy density and low self-discharge rate and impedance.
  • the present application provides a battery module, a battery pack, and an electrical device including the secondary battery.
  • the battery modules, battery packs and electrical consumers also have excellent mass energy density and low self-discharge rate and impedance.
  • FIG. 1 is a schematic diagram of a secondary battery according to one embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an electrical device in which a secondary battery is used as a power source according to an embodiment of the present application.
  • Fig. 7 is a schematic diagram of the structure of an electrode pad according to an embodiment of the present application.
  • Fig. 8 is a schematic diagram of an electrode sheet formed with a wedge-shaped hole.
  • the electrode sheet of the present application and the secondary battery, battery module, battery pack and electric device containing it will be described in detail below.
  • the first embodiment of the present application may provide an electrode pole piece (please refer to FIG. 7 ), the electrode pole piece 6 includes a current collector 7 and an active material layer 8 disposed on at least one surface of the current collector 7,
  • a first inorganic isolation layer 9 and a second inorganic isolation layer 10 are sequentially formed on the active material layer 8,
  • the first inorganic isolation layer 9 includes a plurality of channels 11 and the diameter of the channels 11 is 300nm-600nm,
  • Each of the plurality of channels 11 extends from the first inorganic isolation layer 9 toward the second inorganic isolation layer 10 and penetrates through the second inorganic isolation layer 10, and
  • the pore diameters of the channels 11 in the second inorganic isolation layer 10 are uniform.
  • this embodiment by using an inorganic separator as a separator to replace a conventional polymer such as a polypropylene separator, the manufacturing cost of the battery can be greatly reduced (as we all know, polymers such as polyethylene film and polypropylene as a separator for batteries The cost of the membrane is significantly greater than the cost of the inorganic barrier layer).
  • this embodiment can significantly increase the mass energy density of the battery by forming through holes in the inorganic separator, and significantly improve the ion conduction of the inorganic separator. performance, thereby significantly reducing the impedance of the battery.
  • the invention of the present application creates pores by adding a pore-forming agent to the first inorganic isolation layer, and utilizes the gas generated by the pore-forming agent to flow between the first inorganic isolation layer and the second inorganic isolation layer.
  • the formation of through-holes with relatively uniform pore diameters (300nm-600nm) in the layer can significantly increase the mass energy density of the battery, and significantly improve the ion conductivity of the inorganic isolation layer, thereby significantly reducing the impedance of the battery.
  • the pore size of the channels in the layer is uniform.
  • the pore diameter of the channels is uniform means that the respective pore diameters of the channels do not change greatly in the through direction (that is, non-wedge-shaped channels are formed).
  • the pore diameter of the channels is uniform means that: in the through direction, the maximum value of the respective pore diameters of the channels is less than 1.3 times the minimum value.
  • the diameters of the channels formed by the gaps between the inorganic particles in the inorganic isolation layer are usually less than 300 nm (about 200 nm).
  • the pore diameter of the channel formed by adding the pore-forming agent is more than 300nm, and the channel runs through the first inorganic isolation layer and the second inorganic isolation layer, thus the inorganic isolation layer can be reduced.
  • the pore diameter of the through-hole channel can be controlled to be below 600nm.
  • the pore diameter of the through channel 11 is 300nm-550nm, 350nm-500nm, 300nm-450nm, 300nm-4000nm, or 350nm-400nm.
  • the term “penetrating” means that the channel connects the two main surfaces of the inorganic isolation layer, and the path of the channel can be straight or curved.
  • the term “penetrating” does not include the case where the two main surfaces of the inorganic separation layer are communicated through wedge-shaped channels. These through channels in the inorganic separator can not only reduce the mass of the inorganic separator per unit volume to increase the mass energy density of the battery, but also provide a moving path for active ions, thereby significantly improving the ion conductivity of the inorganic separator as a separator. .
  • the sum of the thicknesses of the first inorganic separator layer and the second inorganic separator layer may be 7 ⁇ m to 30 ⁇ m.
  • the sum of the thicknesses of the first inorganic isolation layer and the second inorganic isolation layer may be 8 ⁇ m-25 ⁇ m, 9 ⁇ m-23 ⁇ m, 10 ⁇ m-20 ⁇ m, 12 ⁇ m-18 ⁇ m or 15 ⁇ m-20 ⁇ m.
  • the sum of the thicknesses of the first inorganic isolation layer and the second inorganic isolation layer is more than 7 ⁇ m, the insulation of the inorganic isolation layer as an isolation film can be better ensured, and the inorganic isolation layer can be significantly reduced. quality, thereby increasing the mass energy density of the battery.
  • the sum of the thicknesses of the first inorganic separator layer and the second inorganic separator layer is 30 ⁇ m or less, the inorganic separator layer can function as a separator separating the positive and negative electrodes without reducing the mass energy density of the battery. effect. Therefore, the sum of the thicknesses of the first inorganic separator layer and the second inorganic separator layer in this embodiment may be within the above range, thereby significantly improving the mass energy density of the battery while ensuring insulation.
  • the The thickness of the first inorganic isolation layer may be 2 ⁇ m ⁇ 10 ⁇ m.
  • the thickness of the first inorganic isolation layer may be 2 ⁇ m-9 ⁇ m, 3 ⁇ m-8 ⁇ m, 4 ⁇ m-7 ⁇ m, 3 ⁇ m-5 ⁇ m, 4 ⁇ m-6 ⁇ m or 5 ⁇ m-10 ⁇ m.
  • the first inorganic isolation layer extends toward the second inorganic isolation layer and runs through the second inorganic isolation layer, and has a plurality of channels with relatively uniform pore diameters of 300 nm to 600 nm.
  • the thickness of the first inorganic spacer layer is greater than 10 ⁇ m, since the thickness of the inorganic spacer layer containing the pore-forming agent is relatively large, the gas generated in the pore-forming stage is easy to be in this layer and synthesize large bubbles, thereby It is easy to form wedge-shaped channels in the first inorganic spacer layer and the diameter of the channels formed in the second inorganic spacer layer is relatively large. Therefore, it is easy to cause problems such as uneven mechanical properties of the inorganic isolation layer, self-discharge or even short circuit of the battery.
  • the thickness of the first inorganic spacer layer in this embodiment can be within the above-mentioned range, so that it is easy to form layers extending from the first inorganic spacer layer toward the second inorganic spacer layer and penetrating through the second inorganic spacer layer.
  • the isolation layer has a plurality of channels with a relatively uniform pore diameter of 300nm to 600nm. Therefore, a secondary battery including the electrode tab of the present embodiment may have excellent mass energy density and low self-discharge rate and impedance.
  • the porosity of the first inorganic separator layer and the second inorganic separator layer may be 40% to 55%, respectively.
  • the porosity of the inorganic isolation layer without pore formation reported in the prior art is about 35%. Therefore, in the invention of the present application, fine through-hole channels are formed in the inorganic isolation layer by forming holes to increase the porosity in the inorganic isolation layer to more than 40%, which can increase the mass energy density of the battery and improve the performance of the inorganic isolation layer. ionic conductivity, thereby significantly reducing the impedance of the battery.
  • the porosity in the inorganic separator to 55% or less, it is possible to ensure that the inorganic separator as a separator has excellent mechanical strength and can secure insulation. Therefore, the porosity of the first inorganic separator layer and the second inorganic separator layer in this embodiment can be within the above range, thereby improving the mass energy density of the battery, ensuring insulation and excellent mechanical properties.
  • the thickness of the first inorganic spacer layer is very thin, and the total thickness of the two inorganic spacer layers is also relatively thin, it is difficult to measure the porosity of the two inorganic spacer layers respectively, so the The porosity of the first inorganic isolation layer and the second inorganic isolation layer refers to the porosity of the two inorganic isolation layers.
  • each of the first inorganic separator layer and the second inorganic separator layer may include inorganic particles and a binder.
  • the first inorganic separation layer may include 90% to 95% by weight of inorganic particles and 5% to 10% by weight of a binder; and the The second inorganic isolation layer may include 95% to 98% by weight of inorganic particles and 2% to 5% by weight of a binder.
  • the first inorganic isolation layer may include 5% by weight to 10% by weight % of a higher amount of binder.
  • the second inorganic spacer layer does not contain a pore-forming agent, no vacancies due to the disappearance of the pore-forming agent will appear in this layer during the pore-forming stage. Therefore, a lesser amount of the binder may be included in the second inorganic spacer layer in an amount of 2 wt % to 5 wt %.
  • Including the inorganic particles within the above content range in the inorganic separation layer can improve the mechanical properties and insulation properties of the electrode sheet. Therefore, the contents of the inorganic particles and the binder in the first inorganic separation layer and the second inorganic separation layer of the present embodiment may be within the above ranges, thereby improving the mechanical properties and insulation properties of the electrode sheet.
  • the first inorganic isolation layer and the second inorganic isolation layer may also contain other components such as fiber materials to improve the mechanical properties of the inorganic isolation layer.
  • the volume median particle diameter Dv50 of the inorganic particles may be 30 nm to 500 nm.
  • the volume median particle diameter Dv50 of inorganic particles can be measured with reference to the standard GB/T 19077.1-2016, using a laser particle size analyzer (such as Malvern Master Size 3000).
  • a laser particle size analyzer such as Malvern Master Size 3000.
  • the physical definition of Dv50 is as follows: Dv50: the particle size corresponding to when the cumulative volume distribution percentage of inorganic particles reaches 50%.
  • the volume median particle diameter Dv50 of the inorganic particles When the volume median particle diameter Dv50 of the inorganic particles is less than 30nm, the inorganic particles in the inorganic separation layer tend to accumulate densely, thereby easily blocking the pores in the inorganic separation layer. Therefore, when the volume median particle diameter Dv50 of the inorganic particles is less than 30 nm, the ion conductivity of the electrode sheet may be poor. On the other hand, when the volume median diameter Dv50 of the inorganic particles is larger than 500nm, the gap between the inorganic particles in the inorganic isolation layer is relatively large, and it is not easy to form a plurality of fine pores with a relatively uniform pore diameter of 300nm to 600nm. .
  • the volume median particle diameter Dv50 of the inorganic particles in this embodiment can be within the above range, thereby improving the mass energy density of the battery and improving the ion conductivity of the electrode sheet (thus reducing the impedance of the electrode sheet) .
  • the inorganic particles may include at least one selected from the group consisting of silicon oxide, aluminum oxide, boehmite, magnesium oxide, titanium oxide, zinc oxide, and aluminum magnesium oxide.
  • the inorganic particles may include at least one selected from the group consisting of boehmite and alumina magnesium.
  • the binder may include carboxymethyl cellulose, polyvinylidene fluoride, styrene-butadiene rubber, polyimide, polyethylene, polyvinylidene fluoride-hexafluoropropylene copolymer At least one of the group consisting of.
  • the binder may include at least one selected from the group consisting of carboxymethyl cellulose, polyvinylidene fluoride and styrene-butadiene rubber.
  • the electrode sheet may be a positive electrode sheet or a negative electrode sheet.
  • a second embodiment of the present application may provide a secondary battery including the electrode sheet of the above embodiment.
  • the secondary battery has excellent mass energy density and low self-discharge rate and impedance.
  • This embodiment provides a method for preparing an electrode pole piece, and the method may include the following steps:
  • step (e) heat-treating the product obtained after step (d) at the pore-forming temperature of the pore-forming agent to obtain The electrode pole piece of the second inorganic separation layer
  • the first inorganic isolation layer comprises a plurality of channels and the thickness of the first inorganic isolation layer is 2 ⁇ m to 10 ⁇ m,
  • Each of the plurality of channels extends from the first inorganic isolation layer toward the second inorganic isolation layer and penetrates through the second inorganic isolation layer, and
  • the pore diameters of the channels in the second inorganic isolation layer are uniform.
  • the method of coating the active material layer on at least one surface of the current collector is not particularly limited, and coating methods commonly used in the art can be used.
  • coating may be performed by a method of coating an active material slurry on one surface of a current collector and then uniformly dispersing it using a doctor blade or the like.
  • the coating method may also include various coating methods such as casting, comma blade coating, screen printing coating, gravure coating, and the like.
  • the method of coating the slurry for forming the first inorganic isolation layer on the active material layer is not particularly limited, and coating methods commonly used in the art can be used.
  • coating may be performed by applying a slurry for forming the first inorganic barrier layer on the surface of the active material layer and then uniformly dispersing it using a doctor blade or the like.
  • the coating method may also include the above-mentioned various coating methods.
  • step (c) the method of drying the applied slurry is not particularly limited, as long as 30% to 60% by weight of the pore-forming agent can be dried and removed at a temperature lower than the pore-forming temperature of the pore-forming agent.
  • the above-mentioned first dispersant gets final product.
  • various drying methods such as oven drying, infrared drying, and natural drying can be used for the above-mentioned drying.
  • the pore-forming temperature of the pore-forming agent varies depending on the type of pore-forming agent.
  • the above-mentioned pore-forming temperature refers to the temperature at which ammonium bicarbonate starts to decompose. Ammonium bicarbonate begins to decompose slowly at 35°C and completely decomposes at 60°C. Therefore, in the case of using ammonium bicarbonate as a pore-forming agent, the heat treatment temperature in step (c) should be lower than the temperature at which ammonium bicarbonate begins to decompose, ie lower than 35°C.
  • step (c) The purpose of heat treatment in step (c) is to coat the slurry for forming the second inorganic isolation layer on the partially dried first inorganic isolation layer to avoid mixing of the two slurries.
  • the first inorganic spacer layer is substantially completely dried (for example, more than 60% by weight of the first dispersant is removed by drying)
  • the gas generated during the pore-forming stage will be difficult or impossible to pass through the first inorganic spacer layer.
  • Inorganic particles are opened to form pores.
  • step (c) 30% to 60% by weight of the first dispersant is removed by heat treatment to achieve partial drying of the first inorganic isolation layer.
  • the method of coating the slurry for forming the second inorganic isolation layer on the first inorganic isolation layer is not particularly limited, and a coating method commonly used in the art can be used.
  • the following method can be used for coating: the slurry used to form the second inorganic isolation layer is evenly coated on the surface of the first inorganic isolation layer by extrusion spraying.
  • the coating method may also include the above-mentioned various coating methods.
  • step (e) the product obtained after step (d) is heat-treated at the pore-forming temperature of the pore-forming agent, whereby the first inorganic separating layer and the second inorganic separating layer are treated by the pore-forming agent. Make holes.
  • the pore-forming temperature of the pore-forming agent refers to the temperature range in which the pore-forming agent can produce pores in the inorganic barrier layer by thermal decomposition or the like (for example, in the case of using ammonium bicarbonate as the pore-forming agent, the pore-forming The temperature is 40°C to 60°C).
  • the above heat treatment may be a step heat treatment.
  • the product obtained after step (d) can be firstly heat-treated at 40°C to 50°C to slowly decompose ammonium bicarbonate so that the generated bubbles do not A large amount of bubbles will be gathered in the first inorganic isolation layer to form large bubbles and avoid the formation of wedge-shaped channels or large-diameter channels in the first inorganic isolation layer during the escape process of the bubbles. Then, heat treatment is carried out at 70° C. to 80° C. to completely decompose the ammonium bicarbonate and make the air bubbles quickly penetrate the inorganic isolation layer.
  • the generated gas can be formed along the first inorganic barrier layer without merging into large bubbles. and the gap in the second inorganic isolation layer escape, while the inorganic particles on both sides of the gap are squeezed away when passing through the first inorganic isolation layer and the second inorganic isolation layer in sequence to form a pore diameter of 300nm in the inorganic isolation layer ⁇ 600nm fine pores.
  • the channels extend from the first inorganic isolation layer toward the second inorganic isolation layer and pass through the second inorganic isolation layer, and the apertures of the channels in the second inorganic isolation layer are uniform.
  • a secondary battery including the electrode tab of the present embodiment may have excellent mass energy density and low self-discharge rate and impedance.
  • the first inorganic spacer layer in the slurry for forming the first inorganic spacer layer may be 35% to 45% by weight, 1% to 4% by weight, and 45% to 55% by weight. %, 5% by weight to 10% by weight, and
  • the content of the second inorganic particles, the second binder and the second dispersant in the slurry for forming the second inorganic isolation layer may be 40% by weight to 55% by weight, 1 % by weight to 5% by weight, and 40% by weight to 55% by weight.
  • the content of the pore-forming agent in the slurry for forming the first inorganic isolation layer may be 5% to 9% by weight, 5% to 9.5% by weight, and 5% to 9.9% by weight. % by weight, 5% to 7% by weight, 6% to 9.5% by weight and 7% to 9.9% by weight.
  • the preparation method of the electrode sheet may further include a step of pressing after step (a) and/or step (e).
  • step (e) By pressing the active material layer or the inorganic isolation layer, the volume of the electrode sheet can be reduced, thereby increasing the mass energy density of the battery.
  • the sum of the thicknesses of the first inorganic separator layer and the second inorganic separator layer may be 7 ⁇ m to 30 ⁇ m.
  • the sum of the thicknesses of the first inorganic isolation layer and the second inorganic isolation layer may be 8 ⁇ m-25 ⁇ m, 9 ⁇ m-23 ⁇ m, 10 ⁇ m-20 ⁇ m, 12 ⁇ m-18 ⁇ m or 15 ⁇ m-20 ⁇ m.
  • step (a) and/or step (e) is followed by a pressing step, the sum of the thicknesses of the first inorganic isolation layer and the second inorganic isolation layer refers to the sum of the thicknesses after pressing.
  • the sum of the thicknesses of the first inorganic separator layer and the second inorganic separator layer in this embodiment can be within the above range, thereby significantly improving the mass energy of the battery under the condition of ensuring insulation. density.
  • the thickness of the first inorganic isolation layer may be 2 ⁇ m ⁇ 10 ⁇ m.
  • the thickness of the first inorganic isolation layer may be 2 ⁇ m-9 ⁇ m, 3 ⁇ m-8 ⁇ m, 4 ⁇ m-7 ⁇ m, 3 ⁇ m-5 ⁇ m, 4 ⁇ m-6 ⁇ m or 5 ⁇ m-10 ⁇ m.
  • the thickness of the first inorganic spacer layer in this embodiment can be within the above range, so that it is easy to form
  • the second inorganic isolation layer has a plurality of channels with relatively uniform pore diameters of 300nm to 600nm. Therefore, a secondary battery including the electrode tab of the present embodiment may have excellent mass energy density and low self-discharge rate and impedance.
  • the porosity of the first inorganic separator layer and the second inorganic separator layer may each be 40% to 55% from the viewpoint of improving the mass energy density of the battery, ensuring insulation, and excellent mechanical properties. .
  • the porosity of the first inorganic separator layer and the second inorganic separator layer of this embodiment may be within the above range, thereby improving the mass energy density of the battery, ensuring insulation and excellent mechanical properties.
  • the volume median particle diameter Dv50 of the inorganic particles may be 30 nm to 500 nm.
  • the volume median diameter Dv50 of the inorganic particles of the present embodiment can be within the above-mentioned range, thereby improving the mass energy density of the battery and improving the ion conductivity of the electrode sheet (thereby reducing the ionic conductivity of the electrode sheet). impedance).
  • the type of the inorganic particles is not particularly limited.
  • the inorganic particles may include at least one selected from the group consisting of silicon oxide, aluminum oxide, boehmite, magnesium oxide, titanium oxide, zinc oxide, and aluminum magnesium oxide.
  • the inorganic particles may include at least one selected from the group consisting of boehmite and alumina magnesium.
  • the type of the binder is not particularly limited.
  • the binder may include a compound selected from the group consisting of carboxymethyl cellulose, polyvinylidene fluoride, styrene-butadiene rubber, polyimide, polyethylene, polyvinylidene fluoride-hexafluoropropylene copolymer at least one of .
  • the binder may include at least one selected from the group consisting of carboxymethyl cellulose, polyvinylidene fluoride and styrene-butadiene rubber.
  • each of the first dispersant and the second dispersant may include a compound selected from the group consisting of water, methanol, ethanol, n-propanol, At least one selected from the group consisting of isopropanol, acetone, and N-methylpyrrolidone.
  • the dispersant can vary depending on the type of pole piece used. For example, N-methylpyrrolidone can be used as the dispersant when it is applied to the positive electrode sheet; water can be used as the dispersant when it is applied to the negative electrode sheet.
  • the pore-forming agent should be a substance whose pore-forming temperature is lower than the evaporation temperature of the dispersant. If the pore-forming temperature of the pore-forming agent is higher than the evaporation temperature of the dispersing agent, the dispersing agent will be preferentially removed during the heat treatment, and accordingly the inorganic particles will be bound by the binder, so that the gas generated by the pore-forming agent cannot The through-hole channel is extruded in the inorganic isolation layer.
  • the pore former includes at least one selected from the group consisting of ammonium carbonate and ammonium bicarbonate.
  • the electrode sheet may be a positive electrode sheet or a negative electrode sheet.
  • a secondary battery in one embodiment, includes a positive pole piece, a negative pole piece, an electrolyte, and a separator.
  • a positive pole piece During the charging and discharging process of the battery, lithium ions are intercalated and extracted back and forth between the positive pole piece and the negative pole piece.
  • the electrolyte plays the role of conducting lithium ions between the positive pole piece and the negative pole piece.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows ions to pass through.
  • the electrode pole piece in this application includes both the active material layer and the inorganic isolation layer as the isolation film.
  • the electrode sheet (for example, positive electrode sheet) of the present application is combined with the corresponding counter electrode sheet (for example, negative electrode sheet) to obtain a battery comprising a positive electrode sheet, a separator and the electrode assembly of the negative pole piece.
  • the electrode sheet for example, positive electrode sheet
  • the corresponding counter electrode sheet for example, negative electrode sheet
  • the positive electrode sheet may include a positive electrode current collector, a positive electrode active material layer and the aforementioned inorganic separator layer disposed on at least one surface of the positive electrode current collector.
  • the positive active material layer may include a positive active material and optionally a binder and a conductive agent.
  • the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode active material layer is disposed on either or both of the opposing two surfaces of the positive electrode current collector.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • aluminum foil can be used as the metal foil.
  • the composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate Formed on substrates such as polyethylene formate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.
  • PP polypropylene
  • PET polyethylene formate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode active material may be a positive electrode active material known in the art for secondary batteries.
  • the positive active material may include at least one of the following materials: olivine-structured lithium-containing phosphate, lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for secondary batteries can also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 and LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also abbreviated as NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.
  • the olivine structure contains Examples of lithium phosphate may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also may be abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon At least one of a composite material, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also may be abbreviated as LFP)
  • composite materials of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the positive electrode active material layer may optionally further include other additives such as a lithium supplementing agent.
  • the lithium supplementation agent may include lithium supplementation agents commonly used in the art.
  • the lithium replenishing agent may include Li 6 CoO 4 , Li 5 FeO 4 , Li 3 VO 4 , Li 2 MoO 3 , Li 2 RuO 3 , Li 2 MnO 2 , Li 2 NiO 2 , Li 2 Cu At least one of x Ni 1-x M y O 2 , wherein 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 0.1, and M is at least one selected from Zn, Sn, Mg, Fe and Mn.
  • the lithium replenishing agent preferably includes Li 6 CoO 4 , Li 5 FeO 4 , Li 2 NiO 2 , Li 2 CuO 2 and at least one of Li 2 Cu 0.6 Ni 0.4 O 2 .
  • the positive active material layer may further optionally include a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexa At least one selected from the group consisting of fluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • the positive active material layer may further optionally include a conductive agent.
  • conductive agents generally used in the art can be used.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon nanotubes, carbon nanorods, graphene and carbon nanofibers.
  • the positive electrode active material layer coated on the positive electrode current collector can be prepared in the following manner: the above-mentioned components used to prepare the positive electrode sheet, such as positive electrode active material, conductive agent, binder and any other The components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the coating on the positive electrode can be obtained.
  • a solvent such as N-methylpyrrolidone
  • the positive electrode active material layer coated on the positive electrode current collector can be manufactured by casting the positive electrode slurry for forming the positive electrode active material layer on a separate carrier, The film obtained by peeling off from the support was then laminated on the positive electrode current collector. Afterwards, an inorganic separator layer can be coated on the positive electrode active material layer with reference to the method for preparing the electrode sheet of the present application.
  • the negative electrode sheet may include a negative electrode current collector, a negative electrode active material layer and the aforementioned inorganic separator layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode active material layer may include negative electrode active materials and optional binders, conductive agents and other auxiliary agents.
  • the anode current collector has two opposing surfaces in its own thickness direction, and the anode active material layer is disposed on either or both of the two opposing surfaces of the anode current collector.
  • the negative electrode current collector may use a metal foil or a composite current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate.
  • Composite current collectors can be formed by metal materials (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) Formed on substrates such as polyethylene formate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.
  • the negative electrode active material can be a negative electrode active material known in the art for batteries.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of simple tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials of batteries can also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative active material layer may further optionally include a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative active material layer may further optionally include a conductive agent.
  • the conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon nanotubes, carbon nanorods, graphene and carbon nanofibers.
  • the negative electrode active material layer may also optionally include other additives, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode active material layer coated on the negative electrode current collector can be prepared in the following manner: the above-mentioned components used to prepare the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other The components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, it can be coated on the negative electrode current collector.
  • negative electrode active material layer can be manufactured by casting the negative electrode slurry for forming the negative electrode active material layer on a separate carrier, and then separating the The film is laminated on the negative electrode current collector. Afterwards, an inorganic separator layer can be coated on the negative electrode active material layer with reference to the method for preparing the electrode sheet of the present application.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • electrolytes can be liquid or gel.
  • the electrolyte of the embodiment of the present application includes additives.
  • the additives may include additives commonly used in this field.
  • the additives may include, for example, halogenated alkylene carbonate compounds (such as difluoroethylene carbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, (glyme) Ethers, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts , pyrrole, 2-methoxyethanol or aluminum trichloride.
  • the additive may be included in an amount of 0.1 wt% to 5 wt%, or the amount of the additive may be adjusted by those skilled in the art according to
  • the electrolyte is an electrolytic solution.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium difluorodifluorooxalatephosphate and lithium tetrafluorooxalatephosphate.
  • the solvent may be selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the secondary battery may include an outer package.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag can be plastic. Examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG. 1 shows a square-shaped secondary battery 5 as an example.
  • the outer package may include a casing 51 and a cover plate 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece and the separator can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the accommodating cavity. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to actual needs.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 3 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 are arranged in sequence along the length direction of the battery module 4 .
  • multiple secondary batteries 5 may also be arranged in any other manner.
  • the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device.
  • the electric devices may include mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, etc.) , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.
  • a secondary battery, a battery module or a battery pack can be selected according to its use requirements.
  • FIG. 6 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • a device may be a cell phone, tablet, laptop, or the like.
  • the device is generally required to be light and thin, and a secondary battery can be used as a power source.
  • the positive electrode active material lithium iron phosphate, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black in the solvent N-methylpyrrolidone (NMP) according to the mass ratio of 97:2:1, and stir and mix evenly Finally, the positive electrode slurry is obtained; after that, the positive electrode slurry is evenly coated on the aluminum foil of the positive electrode current collector, and then dried and cold pressed to obtain the positive electrode active material layer.
  • NMP N-methylpyrrolidone
  • boehmite volume median particle diameter Dv50 is 200nm
  • ammonium bicarbonate as pore-forming agent
  • NMP as dispersant
  • SBR styrene-butadiene rubber
  • a slurry for forming a second inorganic spacer layer is coated, and the slurry includes boron as second inorganic particles in a weight ratio of 48:2:50.
  • Bouillonite volume median particle diameter Dv50 is 200nm
  • SBR volume median particle diameter
  • NMP volume median particle diameter
  • the obtained product was heat-treated at 50° C. to form pores, thereby obtaining a positive electrode sheet.
  • the physical parameters of the positive pole piece are shown in Table 1 below.
  • Negative active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), thickener carboxymethylcellulose sodium (CMC-Na) are dissolved in the solvent according to the mass ratio of 95:2:2:1
  • Deionized water is uniformly mixed with deionized water as a solvent to prepare negative electrode slurry; then the negative electrode slurry is evenly coated on the negative electrode current collector copper foil, and then dried, cold pressed, and cut to obtain negative electrode sheets.
  • the above-mentioned positive electrode sheet and negative electrode sheet are stacked in the order of one layer of anode on top of one layer of cathode structure, so that the inorganic separator layer as the separator is between the positive and negative active material layers to play the role of isolation, and then multi-layer stacked to obtain Electrode assembly: put the electrode assembly in the aluminum-plastic film bag of the battery case, inject the above-mentioned electrolyte after drying, and then produce a secondary battery through processes such as formation and standing.
  • Example 1 In addition to adjusting the coating amount of the slurry as shown in Table 1 below to adjust the thickness of the inorganic isolation layer, and to adjust the content of the pore-forming agent in the first inorganic isolation layer and the second inorganic isolation layer, the same method as in Example 1 was used. Methods The secondary batteries of Examples 2-6 and Comparative Examples 1-4 were prepared.
  • the secondary battery of Example 7 was prepared in the same manner as in Example 1, except that the pole piece was cold-pressed (10 t pressure) after step (a) in the preparation process.
  • the aperture measurement of the obtained pole piece was carried out by using a JW-K aperture tester (Beijing Jingwei Gaobo Science and Technology Co., Ltd.).
  • the impedances of the secondary batteries obtained in the above examples and comparative examples were tested by a WK65120B tester and by a DC discharge internal resistance measurement method. The measurement results are shown in Table 1 above.
  • the thickness of the first inorganic spacer layer is preferably in the range of 2 ⁇ m to 10 ⁇ m.
  • the sum of the thicknesses of the first inorganic spacer and the second inorganic spacer is preferably in the range of 7 ⁇ m to 30 ⁇ m.
  • Example 2 From the comparison of Example 2 and Comparative Example 2 in Table 1 above, it can be seen that when a pore-forming agent is added to the overall inorganic isolation layer during the pore-forming stage, wedge-shaped channels will be formed in the inorganic isolation layer. Moreover, when the thickness of the inorganic isolation layer is constant, the pore diameter at the larger end of the wedge-shaped channel is obviously larger than the pore diameter in Example 2 of the present application. Correspondingly, this causes a significant increase in the self-discharge rate of the battery.
  • a pore-forming agent to the first inorganic isolation layer to create pores in the first inorganic isolation layer and the second inorganic isolation layer, so as to form pores with uniform pore diameters in the second inorganic isolation layer.
  • the pore diameter of the channels in the inorganic isolation layer is preferably 300 nm to 600 nm.
  • the secondary battery of the present application has excellent mass energy density and low self-discharge rate and impedance.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请涉及一种电极极片及包含其的二次电池。所述电极极片包括集流体和设置在所述集流体的至少一个表面上的活性材料层，所述活性材料层上依次形成有第一无机隔离层和第二无机隔离层，所述第一无机隔离层包含多个孔道并且所述孔道的孔径为300nm～600nm，所述多个孔道各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述第二无机隔离层，并且所述第二无机隔离层中的所述孔道的孔径是均一的。

Description

电极极片及包含其的二次电池 技术领域
本申请涉及电池技术领域，具体地涉及电极极片及包含其的二次电池、电池模块、电池包和用电装置。
背景技术
近年来，随着人们对清洁能源需求的日益递增，二次电池已广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、交通工具、军用设备、航空航天等多个领域。由于二次电池的应用领域得到了极大的扩展，因此对其性能也提出了更高的要求。
在二次电池中，隔离膜起到隔离正负极并允许锂离子传导的作用，是电池重要的构成部分。目前，市售二次电池中采用的主要是具有微孔结构的聚烯烃类隔离膜材料，如聚乙烯(PE)、聚丙烯(PP)的单层或多层膜。聚烯烃隔离膜可以提供用于二次电池的足够的机械强度和化学稳定性，但是在高温条件下则表现出较大的热收缩性。这样的热收缩导致正负极接触及短路，从而引发起火、燃烧甚至爆炸等安全事故。
为此，已经报道了采用无机陶瓷粉体对二次电池聚烯烃类隔离膜进行陶瓷化涂布改性的技术，即利用陶瓷较好的高温热稳定性提高隔离膜的热稳定性能。此外，利用陶瓷材料较好的电解液可润湿性，还可以改善诸如循环性能和放电效率等的电池性能。进一步地，已经报道了采用诸如陶瓷材料的无机隔离层作为隔离膜替换常规使用的聚烯烃类隔离膜的技术。但是，在这样的无机隔离层中，因为无机颗粒的密集堆积而容易堵塞无机隔离层中由无机颗粒之间的间隙形成的缝隙。这会降低无机隔离层的电解液的吸收率，并且由于导离子通道的堵塞而会降低电池动力学能力。而且，这样的无机隔离层的厚度虽然可以调控，但是其总体的质量仍然不可忽视，由此会严重降低电池的质量能量密度。
发明内容
技术问题
为了改善诸如质量能量密度降低的上述问题，已经提出了对无机隔离层进行造孔的技 术。但是，如何造出适合于电池应用的孔隙是一个亟需解决的问题。现有技术报道的是通过将蚀刻牺牲相或烧蚀牺牲相(在烧结时消失的物质)添加到无机隔离层中来进行造孔。但是，这样的造孔方式容易造成引入新的杂质或者在造孔过程中需要耗费大量的能量(例如，在通过烧结造孔时，烧结温度可高达例如700℃以上)的问题，并且高温环境对电极活性物质层中包含的各成分如粘结剂和添加剂等可能会造成不利影响。
本申请的发明人通过深入的研究发现，可以通过在要进行造孔的层中添加能在常规加热时产生气体的物质(例如，加热时分解的物质)进行造孔。在这样的造孔过程中，产生的气体会在逸出过程中并合成大的气泡，并且所述气泡在通过无机颗粒之间的间隙逸出的过程中会将间隙两侧的无机颗粒挤开而形成楔形孔道。由此能形成锂离子穿透的通道，从而提高无机隔离层的离子传导性。然而，本申请的发明人通过进一步研究发现，该孔道的形状及大小不容易控制。因此，所形成的各个孔道的形状及大小不均一，这容易导致无机隔离层机械性能不均一，从而容易在例如压制或卷绕电极极片时造成裂纹等缺陷，由此容易造成电极安全性和容量的降低。另外，在为了提高质量能量密度而将无机隔离层厚度制备为较薄的情况下，上述具有楔形孔道的无机隔离层由于孔道的一端开口较大而导致电池容易发生自放电，并且也更有可能发生短路。
技术方案
本申请的发明人为了解决上述问题而完成了本发明。
根据本申请的第一方面，提供一种电极极片，所述电极极片包括集流体和设置在所述集流体的至少一个表面上的活性材料层，
所述活性材料层上依次形成有第一无机隔离层和第二无机隔离层，
所述第一无机隔离层包含多个孔道并且所述孔道的孔径为300nm～600nm，
所述多个孔道各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述第二无机隔离层，并且
所述第二无机隔离层中的所述孔道的孔径是均一的。
在本方面，通过使用无机隔离层作为隔离膜替代常规的聚合物如聚丙烯隔离膜，可以大幅降低电池的制造成本；与使用未造孔的无机隔离层作为隔离膜的技术相比，本实施方式通过在无机隔离层中形成贯穿孔道而可以显著地提高电池的质量能量密度，并且显著地 提高无机隔离层的离子传导性，从而显著降低电池的阻抗；此外，与形成有楔形孔道的技术相比，本实施方式通过形成各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述第二无机隔离层且孔径为300nm～600nm的多个孔道，可以避免由于楔形孔道而导致的诸如无机隔离层的机械性能不均一、电池容易发生自放电甚至是短路的问题。
根据本申请的任一方面，所述第一无机隔离层和所述第二无机隔离层的厚度之和为7μm～30μm，由此可以改善电池的质量能量密度和确保绝缘性。
根据本申请的任一方面，所述第一无机隔离层的厚度为2μm～10μm，由此容易形成各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述第二无机隔离层且具有300nm～600nm的较为均一的孔径的多个孔道。
根据本申请的任一方面，所述第一无机隔离层和所述第二无机隔离层的孔隙率各自为40％～55％，由此可以提高电池的质量能量密度、确保绝缘性和优异的机械性能。
根据本申请的任一方面，所述第一无机隔离层和所述第二无机隔离层各自包括无机颗粒和粘结剂，由此可以改善电池的自放电率和阻抗。
根据本申请的任一方面，所述第一无机隔离层包括90重量％～95重量％的无机颗粒和5重量％～10重量％的粘结剂；并且
所述第二无机隔离层包括95重量％～98重量％的无机颗粒和2重量％～5重量％的粘结剂。由此，可以改善电极极片的机械性能和绝缘性。
根据本申请的任一方面，所述无机颗粒的体积中值粒径Dv50为30nm～500nm，由此可以提高电池的质量能量密度和改善电极极片的离子传导性。
根据本申请的任一方面，所述无机颗粒包括选自由氧化硅、氧化铝、勃姆石、氧化镁、氧化钛、氧化锌、氧化铝镁构成的组中的至少一种。
根据本申请的任一方面，所述粘结剂包括选自由羧甲基纤维素、聚偏二氟乙烯、丁苯橡胶、聚酰亚胺、聚乙烯、聚偏二氟乙烯-六氟丙烯共聚物构成的组中的至少一种。
根据本申请的任一方面，所述电极极片为正极极片或负极极片。
根据本申请的第二方面，提供一种二次电池，所述二次电池包括上述第一实施方式的电极极片。由于所述二次电池包括上述第一实施方式的电极极片，因此所述二次电池具有优异的质量能量密度以及低的自放电率和阻抗。
根据本申请的第三方面，提供一种电池模块，其包括上述第二实施方式的二次电池。所述电池模块具有优异的质量能量密度以及低的自放电率和阻抗。
根据本申请的第四方面，提供一种电池包，其包括上述第三实施方式的电池模块。所述电池包具有优异的质量能量密度以及低的自放电率和阻抗。
根据本申请的第五方面，提供一种用电装置，其包括上述第二实施方式的二次电池、第三实施方式的电池模块或第四实施方式的电池包中的至少一种。所述用电装置具有优异的质量能量密度以及低的自放电率和阻抗。
根据本申请的第六方面，提供一种电极极片的制备方法，所述方法包括如下步骤：
(a)在集流体的至少一个表面上涂布活性材料层，
(b)在所述活性材料层上涂布用于形成第一无机隔离层的浆料，所述浆料包括第一无机颗粒、第一粘结剂、第一分散剂和造孔剂，
(c)在低于所述造孔剂的造孔温度的温度下对涂布的所述用于形成第一无机隔离层的浆料进行干燥以除去30重量％～60重量％的所述第一分散剂，
(d)在步骤(c)之后得到的初步干燥的第一无机隔离层上，涂布用于形成第二无机隔离层的浆料，所述浆料包括第二无机颗粒、第二粘结剂和第二分散剂，
(e)在所述造孔剂的造孔温度下对在步骤(d)之后得到的产物进行热处理，以得到包括所述集流体、所述活性材料层、所述第一无机隔离层和所述第二无机隔离层的电极极片，
其中所述第一无机隔离层包含多个孔道并且所述孔道的孔径为300nm～600nm，
所述多个孔道各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述第二无机隔离层，并且
所述第二无机隔离层中的所述孔道的孔径是均一的。
根据本申请的上述制备方法，可以避免形成在单层无机隔离层中添加造孔剂时出现的楔形孔道，并且能够形成各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述第二无机隔离层且具有300nm～600nm的较为均一的孔径的多个孔道。由此，包含本实施方式的电极极片的二次电池可以具有优异的质量能量密度以及低的自放电率和阻抗。
根据本申请的任一方面，所述用于形成第一无机隔离层的浆料中的所述第一无机颗粒、所述第一粘结剂、所述第一分散剂和所述造孔剂的含量各自为35重量％～45重量％，1重量％～4重量％，45重量％～55重量％，5重量％～10重量％，并且
所述用于形成第二无机隔离层的浆料中的所述第二无机颗粒、所述第二粘结剂和所述第二分散剂的含量各自为40重量％～55重量％，1重量％～5重量％，40重量％～55重量％。由此，可以易于制造本实施方式的包含所述第一无机隔离层和所述第二无机隔离层的电极极片。
根据本申请的任一方面，所述方法还包括在步骤(a)和/或步骤(e)之后进行压制的步骤。通过对活性材料层或者无机隔离层进行压制，可以减小电极极片的体积，从而增加电池的质量能量密度。
根据本申请的任一方面，所述第一无机隔离层和所述第二无机隔离层的厚度之和为7μm～30μm。由此，可以改善电池的质量能量密度和确保绝缘性。
根据本申请的任一方面，所述第一无机隔离层的厚度为2μm～10μm。由此，可以容易形成各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述第二无机隔离层且具有300nm～600nm的较为均一的孔径的多个孔道。
根据本申请的任一方面，所述第一无机隔离层和所述第二无机隔离层的孔隙率各自为40％～55％。由此，可以提高电池的质量能量密度、确保绝缘性和优异的机械性能。
根据本申请的任一方面，所述第一无机颗粒和所述第二无机颗粒的体积中值粒径Dv50 可以各自为30nm～500nm。由此，可以提高电池的质量能量密度和改善电极极片的离子传导性。
根据本申请的任一方面，所述第一分散剂和所述第二分散剂各自包括选自由水、甲醇、乙醇、正丙醇、异丙醇、丙酮、N-甲基吡咯烷酮构成的组中的至少一种。由此，在制备过程中易于形成适合于涂布的浆料、易于操作且不损害电池性能。
根据本申请的任一方面，所述造孔剂包括选自由碳酸铵和碳酸氢铵构成的组中的至少一种。由此，可以在低温下简单方便地在第一无机隔离层和第二无机隔离层中形成均一的贯穿孔道。
有益效果
本申请提供一种电极极片，所述电极极片通过在无机隔离层中形成孔径较为均一的贯穿孔道而可以显著地提高电池的质量能量密度，并且显著地提高无机隔离层的离子传导性，从而显著降低电池的阻抗；此外，与形成有楔形孔道的技术相比，所述电极极片通过形成各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述第二无机隔离层且孔径为300nm～600nm的多个孔道，可以避免由于楔形孔道而导致的诸如无机隔离层的机械性能不均一、电池容易发生自放电甚至是短路的问题。因此，本申请的包含上述电极极片的二次电池具有优异的质量能量密度以及低的自放电率和阻抗。此外，本申请提供包含所述二次电池的电池模块、电池包和用电装置。所述电池模块、电池包和用电装置也具有优异的质量能量密度以及低的自放电率和阻抗。
附图说明
图1是本申请的一个实施方式的二次电池的示意图。
图2是图1所示的本申请的一个实施方式的二次电池的分解图。
图3是本申请的一个实施方式的电池模块的示意图。
图4是本申请的一个实施方式的电池包的示意图。
图5是图4所示的本申请的一个实施方式的电池包的分解图。
图6是本申请的一个实施方式的二次电池用作电源的用电装置的示意图。
图7是本申请的一个实施方式的电极极片的结构的示意图。
图8是形成有楔形孔道的电极极片的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件；6电极极片；7集流体；8活性材料层；9第一无机隔离层；10第二无机隔离层；11孔道；12楔形孔道。
具体实施方式
以下，对本申请的电极极片进行详细说明，但是会存在省略不必要的详细说明的情况。例如，存在省略对众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，以下说明及实施例是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合而形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合而形成新的技术方案。
以下对本申请的电极极片及包含其的二次电池、电池模块、电池包和用电装置进行详细说明。
本申请的第一实施方式可以提供一种电极极片(请参照图7)，所述电极极片6包括集流体7和设置在所述集流体7的至少一个表面上的活性材料层8，
所述活性材料层8上依次形成有第一无机隔离层9和第二无机隔离层10，
所述第一无机隔离层9包含多个孔道11并且所述孔道11的孔径为300nm～600nm，
所述多个孔道11各自从所述第一无机隔离层9朝向所述第二无机隔离层10延伸并贯穿所述第二无机隔离层10，并且
所述第二无机隔离层10中的孔道11的孔径是均一的。
在本实施方式中，通过使用无机隔离层作为隔离膜替代常规的聚合物如聚丙烯隔离膜，可以大幅降低电池的制造成本(众所周知，作为电池用隔离膜的聚合物如聚乙烯膜和聚丙 烯膜的成本显著大于无机隔离层的成本)。与使用未造孔的无机隔离层作为隔离膜的技术相比，本实施方式通过在无机隔离层中形成贯穿孔道而可以显著地提高电池的质量能量密度，并且显著地提高无机隔离层的离子传导性，从而显著降低电池的阻抗。
此外，当通过在作为隔离膜的单层无机隔离层中添加造孔剂进行造孔时，在造孔过程中，产生的气体会在逸出过程中并合成大的气泡，并且所述气泡在通过无机颗粒之间的间隙逸出的过程中会将间隙两侧的无机颗粒挤开而形成楔形孔道(请参照图8)。如上所述，这样的孔道的形状及大小不容易控制，因此所形成的各个孔道的形状及大小不均一，这容易导致无机隔离层机械性能不均一，从而容易在例如压制或卷绕电极极片时造成裂纹等缺陷。由此，容易造成电极安全性和容量的降低。另外，如上所述，上述具有楔形孔道的无机隔离层由于孔道的一端开口较大而导致电池容易发生自放电，并且也更有可能发生短路。
相比之下，如下文中所详细描述地，本申请发明通过在第一无机隔离层中添加造孔剂进行造孔，并利用造孔剂产生的气体在第一无机隔离层和第二无机隔离层中形成孔径较为均一的贯穿孔道(孔径为300nm～600nm)，可以显著地提高电池的质量能量密度，并且显著地提高无机隔离层的离子传导性，从而显著降低电池的阻抗。在本申请中，如下文所述的，由于在电极极片的制造过程中在第二无机隔离层中不包含造孔剂，因此在该层中不会发生气泡的并合，第二无机隔离层中的孔道的孔径是均一的。在本申请中，所述孔道的孔径是均一的是指所述孔道各自的孔径在贯穿方向上不发生大的变化(即形成的是非楔形孔道)。具体地，所述孔道的孔径是均一的是指：在贯穿方向上，所述孔道各自的孔径的最大值为最小值的1.3倍以下。
在不添加造孔剂的情况下，无机隔离层中由无机颗粒之间的间隙形成的孔道的直径通常均小于300nm(200nm左右)。相比之下，在本申请发明中，通过添加造孔剂形成的孔道的孔径为300nm以上，并且所述孔道贯穿第一无机隔离层和第二无机隔离层，由此可以通过降低无机隔离层的质量而显著地提高电池的质量能量密度，并且通过具有较大孔径的贯穿孔道而显著地提高无机隔离层的离子传导性，从而显著降低电池的阻抗。此外，如下文中所详细描述地，通过选择造孔剂的种类和控制造孔条件(例如造孔工序中的加热温度)并且仅在第一无机隔离层中添加造孔剂(以防止造孔剂在整体无机隔离层中产生气体并所述气体在逸出过程中并合成大的气泡)，可以将贯穿孔道的孔径控制为600nm以下。通过 将贯穿孔道的孔径控制为600nm以下，可以防止由于孔径较大而导致的电池容易发生自放电甚至是发生短路的问题。可选地，所述孔道11的孔径为300nm～550nm，350nm～500nm，300nm～450nm，300nm～4000nm，或350nm～400nm。
在本申请发明中，术语“贯穿”是指孔道将无机隔离层的两个主表面连通，并且孔道的路径可以为直线型也可以为曲线型。术语“贯穿”不包括通过楔形孔道将无机隔离层的两个主表面连通的情形。无机隔离层中的这些贯穿孔道既能够减少单位体积的无机隔离层的质量从而提高电池的质量能量密度，又能够为活性离子提供移动路径，从而显著提高作为隔离膜的无机隔离层的离子传导性。
从改善电池的质量能量密度和确保绝缘性的观点考虑，所述第一无机隔离层和所述第二无机隔离层的厚度之和可以为7μm～30μm。可选地，所述第一无机隔离层和所述第二无机隔离层的厚度之和可以为8μm～25μm，9μm～23μm，10μm～20μm，12μm～18μm或15μm～20μm。
当所述第一无机隔离层和所述第二无机隔离层的厚度之和为7μm以上时，可以更好地确保作为隔离膜的无机隔离层的绝缘性，并且能够显著地降低无机隔离层的质量，从而提高电池的质量能量密度。当所述第一无机隔离层和所述第二无机隔离层的厚度之和为30μm以下时，无机隔离层可以在不降低电池的质量能量密度的条件下起到隔离正负电极的隔离膜的作用。因此，本实施方式的所述第一无机隔离层和所述第二无机隔离层的厚度之和可以在上述范围内，由此可以在确保绝缘性的条件下显著地改善电池的质量能量密度。
从容易形成各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述第二无机隔离层且具有300nm～600nm的较为均一的孔径的多个孔道的观点考虑，所述第一无机隔离层的厚度可以为2μm～10μm。可选地，所述第一无机隔离层的厚度可以为2μm～9μm，3μm～8μm，4μm～7μm，3μm～5μm，4μm～6μm或5μm～10μm。
当第一无机隔离层的厚度小于2μm时，由于需要涂布得非常薄，因此实际上在工艺上难以实现。此外，当第一无机隔离层的厚度小于2μm时，不易在该层中均匀地添加造孔剂，并且在造孔阶段不易形成能够穿过第二无机隔离层的气泡，由此不易形成各自从第一无机 隔离层朝向第二无机隔离层延伸并贯穿第二无机隔离层且具有300nm～600nm的较为均一的孔径的多个孔道。相反地，当第一无机隔离层的厚度大于10μm时，由于含有造孔剂的无机隔离层的厚度相对较大，因此在造孔阶段产生的气体容易在该层中并合成大的气泡，从而容易在第一无机隔离层中形成楔形孔道并且在第二无机隔离层中形成的孔道的直径相对较大。因此，容易导致诸如无机隔离层的机械性能不均一、电池容易发生自放电甚至是短路的问题。因此，本实施方式的所述第一无机隔离层的厚度可以在上述范围内，由此容易形成各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述第二无机隔离层且具有300nm～600nm的较为均一的孔径的多个孔道。因此，包含本实施方式的电极极片的二次电池可以具有优异的质量能量密度以及低的自放电率和阻抗。
从提高电池的质量能量密度、确保绝缘性和优异的机械性能的观点考虑，所述第一无机隔离层和所述第二无机隔离层的孔隙率可以各自为40％～55％。
现有技术报道的未进行造孔的无机隔离层的孔隙率为35％左右。因此，在本申请发明中，通过造孔在无机隔离层中形成微细的贯穿孔道以将无机隔离层中的孔隙率提高至40％以上，可以提高电池的质量能量密度，并且改善无机隔离层的离子传导性，从而显著降低电池的阻抗。另一方面，通过将无机隔离层中的孔隙率控制为55％以下，可以确保作为隔离膜的无机隔离层具有优异的机械强度并且能够确保绝缘性。因此，本实施方式的第一无机隔离层和第二无机隔离层的孔隙率可以在上述范围内，由此可以提高电池的质量能量密度、确保绝缘性和优异的机械性能。
在本申请中，由于第一无机隔离层的厚度非常薄，并且实质上两层无机隔离层的总厚度也较薄，所以难以分别测定两个无机隔离层各自的孔隙率，因此本申请中的所述第一无机隔离层和所述第二无机隔离层的孔隙率指的是两层无机隔离层的孔隙率。
从改善电池的自放电率和阻抗的观点考虑，所述第一无机隔离层和所述第二无机隔离层各自可以包括无机颗粒和粘结剂。
从改善电极极片的机械性能和绝缘性的观点考虑，所述第一无机隔离层可以包括90重量％～95重量％的无机颗粒和5重量％～10重量％的粘结剂；并且所述第二无机隔离层可 以包括95重量％～98重量％的无机颗粒和2重量％～5重量％的粘结剂。
在本申请发明中，由于在第一无机隔离层中包含造孔剂，因此为了避免因为造孔阶段的造孔损害无机隔离层的机械性能，第一无机隔离层可以包括5重量％～10重量％的较多量的粘结剂。相比之下，由于第二无机隔离层中不包含造孔剂，因此在造孔阶段该层中不会出现由于造孔剂的消失而产生的空位。因此，在第二无机隔离层中可以包括2重量％～5重量％的较少量的粘结剂。在无机隔离层中包含上述含量范围内的无机颗粒，可以改善电极极片的机械性能和绝缘性。因此，本实施方式的第一无机隔离层和第二无机隔离层的无机颗粒和粘结剂的含量各自可以在上述范围内，由此可以改善电极极片的机械性能和绝缘性。
此外，在本申请中，根据实际需要，所述第一无机隔离层和所述第二无机隔离层还可以包含其它成分如纤维类材料等以改善无机隔离层的机械性能等性能。
从提高电池的质量能量密度和改善电极极片的离子传导性的观点考虑，所述无机颗粒的体积中值粒径Dv50可以为30nm～500nm。
在本申请中，无机颗粒的体积中值粒径Dv50可以参照标准GB/T 19077.1-2016、使用激光粒度分析仪(如Malvern Master Size 3000)进行测定。其中，Dv50的物理定义如下：Dv50：无机颗粒累计体积分布百分数达到50％时所对应的粒径。
当无机颗粒的体积中值粒径Dv50小于30nm时，无机隔离层中的无机颗粒容易密集堆积，从而容易堵塞无机隔离层中的孔道。因此，当无机颗粒的体积中值粒径Dv50小于30nm时，电极极片的离子传导性可能较差。另一方面，当无机颗粒的体积中值粒径Dv50大于500nm时，无机隔离层中的无机颗粒之间的间隙较大，不容易形成具有300nm～600nm的较为均一的孔径的多个微细的孔道。由此，可能无法改善电池的质量能量密度和改善电极极片的离子传导性。因此，本实施方式的所述无机颗粒的体积中值粒径Dv50可以在上述范围内，由此可以改善电池的质量能量密度和改善电极极片的离子传导性(从而降低电极极片的阻抗)。
在本实施方式中，所述无机颗粒可以包括选自由氧化硅、氧化铝、勃姆石、氧化镁、氧化钛、氧化锌、氧化铝镁构成的组中的至少一种。可选地，所述无机颗粒可以包括选自勃姆石和氧化铝镁构成的组中的至少一种。
在本实施方式中，所述粘结剂可以包括选自由羧甲基纤维素、聚偏二氟乙烯、丁苯橡胶、聚酰亚胺、聚乙烯、聚偏二氟乙烯-六氟丙烯共聚物构成的组中的至少一种。可选地，所述粘结剂可以包括选自羧甲基纤维素、聚偏二氟乙烯和丁苯橡胶构成的组中的至少一种。
在本实施方式中，对所述电极极片的种类没有特别限制。例如，所述电极极片可以为正极极片或负极极片。
本申请的第二实施方式可以提供一种二次电池，所述二次电池包括上述实施方式的电极极片。所述二次电池具有优异的质量能量密度以及低的自放电率和阻抗。
以下对本申请的电极极片的制造方法进行详细说明。
本实施方式提供一种电极极片的制备方法，所述方法可以包括如下步骤：
(a)在集流体的至少一个表面上涂布活性材料层，
(b)在所述活性材料层上涂布用于形成第一无机隔离层的浆料，所述浆料包括第一无机颗粒、第一粘结剂、第一分散剂和造孔剂，
(c)在低于所述造孔剂的造孔温度的温度下对涂布的所述用于形成第一无机隔离层的浆料进行干燥以除去30重量％～60重量％的所述第一分散剂，
(d)在步骤(c)之后得到的初步干燥的第一无机隔离层上，涂布用于形成第二无机隔离层的浆料，所述浆料包括第二无机颗粒、第二粘结剂和第二分散剂，
(e)在所述造孔剂的造孔温度下对在步骤(d)之后得到的产物进行热处理，以得到包括所述集流体、所述活性材料层、所述第一无机隔离层和所述第二无机隔离层的电极极片，
其中所述第一无机隔离层包含多个孔道并且所述第一无机隔离层的厚度为2μm～10μm，
所述多个孔道各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述 第二无机隔离层，并且
所述第二无机隔离层中的所述孔道的孔径是均一的。
在步骤(a)中，在集流体的至少一个表面上涂布活性材料层的方法没有特别限制，可以采用本领域常用的涂布方法。例如，可以采用如下方法进行涂布：将活性材料浆料涂布在集流体的一个表面上，然后使用刮刀等进行均匀分散。此外，所述涂布方法还可以包括诸如流延、逗号式刮刀涂布、丝网印刷涂布、凹版印刷涂布等的各种涂布方法。
在步骤(b)中，在活性材料层上涂布用于形成第一无机隔离层的浆料的方法没有特别限制，可以采用本领域常用的涂布方法。例如，可以采用如下方法进行涂布：将用于形成第一无机隔离层的浆料涂布在活性材料层的表面上，然后使用刮刀等进行均匀分散。此外，所述涂布方法还可以包括上述的各种涂布方法。
在步骤(c)中，对所涂布的浆料进行干燥的方法没有特别限制，只要能够在低于所述造孔剂的造孔温度的温度下干燥除去30重量％～60重量％的所述第一分散剂即可。例如，上述干燥可以采用烘箱干燥、红外干燥、自然干燥等的各种干燥方法。
所述造孔剂的造孔温度依据造孔剂种类的不同而不同。例如，在采用碳酸氢铵作为造孔剂的情况下，上述造孔温度是指碳酸氢铵开始分解的温度。碳酸氢铵在35℃上开始缓慢分解，并且在60℃时完全分解。因此，在采用碳酸氢铵作为造孔剂的情况下，步骤(c)中的热处理温度应该低于碳酸氢铵开始分解的温度，即低于35℃。在步骤(c)中进行热处理的目的是为了在部分干燥的第一无机隔离层上涂布用于形成第二无机隔离层的浆料以避免两种浆料的混合。但是，如果将第一无机隔离层基本上完全干燥(例如，干燥除去大于60重量％的第一分散剂)，则在造孔阶段产生的气体将难以或者无法通过在第一无机隔离层中挤开无机颗粒而形成孔道。相反地，如果仅除去小于30重量％的第一分散剂，则在步骤(d)中在第一无机隔离层上涂布用于形成第二无机隔离层的浆料时易于将两种浆料混合。因此，在步骤(c)中，通过热处理除去30重量％～60重量％的第一分散剂以实现第一无机隔离层的部分干燥。
在步骤(d)中，在第一无机隔离层上涂布用于形成第二无机隔离层的浆料的方法没有 特别限制，可以采用本领域常用的涂布方法。例如，可以采用如下方法进行涂布：将用于形成第二无机隔离层的浆料通过挤压喷涂均匀的涂布在第一无机隔离层的表面上。此外，所述涂布方法还可以包括上述的各种涂布方法。
在步骤(e)中，在所述造孔剂的造孔温度下对在步骤(d)之后得到的产物进行热处理，由此通过造孔剂对第一无机隔离层和第二无机隔离层进行造孔。所述造孔剂的造孔温度是指所述造孔剂能够通过热分解等而在无机隔离层中制造孔道的温度区间(例如，在使用碳酸氢铵作为造孔剂的情况下，造孔温度为40℃～60℃)。上述热处理可以是分步热处理。例如，在采用碳酸氢铵作为造孔剂的情况下，可以首先在40℃～50℃下对在步骤(d)之后得到的产物进行热处理以使碳酸氢铵缓慢分解，以使得产生的气泡不会在第一无机隔离层中大量聚集而形成大的气泡并且避免气泡在逸出过程中在第一无机隔离层中形成楔形孔道或大直径的孔道。然后，在70℃～80℃下进行热处理，以使碳酸氢铵彻底分解并使气泡快速贯穿无机隔离层。通过选择造孔剂的种类并根据造孔剂的种类合理地调节步骤(e)中进行热处理的温度，可以使得产生的气体在不并合为大的气泡的情况下沿着第一无机隔离层和第二无机隔离层中的间隙逸出，同时在依次穿过第一无机隔离层和第二无机隔离层时将间隙两侧的无机颗粒挤开而在所述无机隔离层中形成孔径为300nm～600nm的微细孔道。所述孔道从第一无机隔离层朝向第二无机隔离层延伸并贯穿第二无机隔离层，并且所述第二无机隔离层中的孔道的孔径是均一的。
在本申请的电极极片的制备方法中，由于仅在第一无机隔离层中添加造孔剂并且通过选择造孔剂的种类并根据造孔剂的种类合理地调节步骤(e)中进行热处理的温度，因此可以避免形成在单层无机隔离层中添加造孔剂时出现的楔形孔道，并且能够形成各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述第二无机隔离层且具有300nm～600nm的较为均一的孔径的多个孔道。因此，包含本实施方式的电极极片的二次电池可以具有优异的质量能量密度以及低的自放电率和阻抗。
从易于制造本实施方式的包含所述第一无机隔离层和所述第二无机隔离层的电极极片的观点考虑，所述用于形成第一无机隔离层的浆料中的所述第一无机颗粒、所述第一粘结剂、所述第一分散剂和所述造孔剂的含量各自可以为35重量％～45重量％，1重量％～4重量％，45重量％～55重量％，5重量％～10重量％，并且
所述用于形成第二无机隔离层的浆料中的所述第二无机颗粒、所述第二粘结剂和所述第二分散剂的含量各自可以为40重量％～55重量％，1重量％～5重量％，40重量％～55重量％。
在本申请中，所述用于形成第一无机隔离层的浆料中的所述造孔剂的含量可以为5重量％～9重量％，5重量％～9.5重量％，5重量％～9.9重量％，5重量％～7重量％，6重量％～9.5重量％和7重量％～9.9重量％。
从进一步提高电池的质量能量密度的观点考虑，所述电极极片的制备方法还可以包括在步骤(a)和/或步骤(e)之后进行压制的步骤。通过对活性材料层或者无机隔离层进行压制，可以减小电极极片的体积，从而增加电池的质量能量密度。
如上所述，从改善电池的质量能量密度和确保绝缘性的观点考虑，所述第一无机隔离层和所述第二无机隔离层的厚度之和可以为7μm～30μm。可选地，所述第一无机隔离层和所述第二无机隔离层的厚度之和可以为8μm～25μm，9μm～23μm，10μm～20μm，12μm～18μm或15μm～20μm。在步骤(a)和/或步骤(e)之后进行了压制的步骤的情况下，所述第一无机隔离层和所述第二无机隔离层的厚度之和是指压制后的厚度之和。
如上所述，本实施方式的所述第一无机隔离层和所述第二无机隔离层的厚度之和可以在上述范围内，由此可以在确保绝缘性的条件下显著地改善电池的质量能量密度。
如上所述，从容易形成各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述第二无机隔离层且具有300nm～600nm的较为均一的孔径的多个孔道的观点考虑，所述第一无机隔离层的厚度可以为2μm～10μm。可选地，所述第一无机隔离层的厚度可以为2μm～9μm，3μm～8μm，4μm～7μm，3μm～5μm，4μm～6μm或5μm～10μm。
如上所述，本实施方式的所述第一无机隔离层的厚度可以在上述范围内，由此容易形成各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述第二无机隔离层且具有300nm～600nm的较为均一的孔径的多个孔道。因此，包含本实施方式的电极极片的二次电池可以具有优异的质量能量密度以及低的自放电率和阻抗。
如上所述，从提高电池的质量能量密度、确保绝缘性和优异的机械性能的观点考虑，所述第一无机隔离层和所述第二无机隔离层的孔隙率可以各自为40％～55％。
如上所述，本实施方式的第一无机隔离层和第二无机隔离层的孔隙率可以在上述范围内，由此可以提高电池的质量能量密度、确保绝缘性和优异的机械性能。
如上所述，从提高电池的质量能量密度和改善电极极片的离子传导性的观点考虑，所述无机颗粒的体积中值粒径Dv50可以为30nm～500nm。
如上所述，本实施方式的所述无机颗粒的体积中值粒径Dv50可以在上述范围内，由此可以改善电池的质量能量密度和改善电极极片的离子传导性(从而降低电极极片的阻抗)。
如上所述，在本实施方式中，所述无机颗粒的种类没有特别限制。例如，所述无机颗粒可以包括选自由氧化硅、氧化铝、勃姆石、氧化镁、氧化钛、氧化锌、氧化铝镁构成的组中的至少一种。可选地，所述无机颗粒可以包括选自勃姆石和氧化铝镁构成的组中的至少一种。
如上所述，在本实施方式中，所述粘结剂的种类没有特别限制。例如，所述粘结剂可以包括选自由羧甲基纤维素、聚偏二氟乙烯、丁苯橡胶、聚酰亚胺、聚乙烯、聚偏二氟乙烯-六氟丙烯共聚物构成的组中的至少一种。可选地，所述粘结剂可以包括选自羧甲基纤维素、聚偏二氟乙烯和丁苯橡胶构成的组中的至少一种。
从易于形成适合于涂布的浆料、易于操作且不损害电池性能的观点考虑，所述第一分散剂和所述第二分散剂各自可以包括选自由水、甲醇、乙醇、正丙醇、异丙醇、丙酮、N-甲基吡咯烷酮构成的组中的至少一种。所述分散剂可以根据所适用的极片类型而变化。例如，在适用于正极极片时，所述分散剂可以使用N-甲基吡咯烷酮；在适用于负极极片时，所述分散剂可以使用水。
从在造孔阶段在第一无机隔离层和第二无机隔离层中可以形成贯穿孔道的观点考虑，所述造孔剂应该为造孔温度低于分散剂的蒸发温度的物质。如果造孔剂的造孔温度高于分散剂的蒸发温度，则分散剂在热处理过程中会被优先除去，相应地无机颗粒会被粘结剂粘结，从而导致造孔剂产生的气体无法在无机隔离层中挤开贯穿的孔道。在本实施方式中，所述造孔剂包括选自由碳酸铵和碳酸氢铵构成的组中的至少一种。
在本实施方式中，对所述电极极片的种类没有特别限制。例如，所述电极极片可以为正极极片或负极极片。
本发明的实施方式的详细说明
以下适当地参照附图对本申请的二次电池、电池模块、电池包和用电装置进行详细说明。
在本申请的一个实施方式中，提供一种二次电池。通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，锂离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导锂离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。本申请中的电极极片既包括活性材料层又包括作为隔离膜的无机隔离层。因此，在制备二次电池时，将本申请的电极极片(例如，正极极片)与相应的对电极极片(例如，负极极片)进行组合，即可得到包含正极极片、隔离膜和负极极片的电极组件。以下对二次电池的各构成要素进行详细说明。
[正极极片]
正极极片可以包括正极集流体以及设置在正极集流体的至少一个表面上的正极活性材料层和上述的无机隔离层。所述正极活性材料层可以包括正极活性材料以及可选的粘结剂和导电剂。
作为示例，正极集流体具有在其自身厚度方向上相对的两个表面，正极活性材料层设置在正极集流体的相对的两个表面中的任一者或两者上。
在一些实施方式中，所述正极集流体可以采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铝箔。复合集流体可以包括高分子材料基材和形成于高分子材料基材的至少一个表面上的金属层。复合集流体可以通过将金属材料(如铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可以采用本领域公知的用于二次电池的正极活性材料。作为示例，正极活性材料可以包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可以被用作二次电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可以包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2和LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可以包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在本申请的实施方式中，正极活性材料层可选地还可以包括其它添加剂如补锂剂。所述补锂剂可以包括本领域通常使用的补锂剂。具体地，所述补锂剂可以包括选自Li 6CoO 4、Li 5FeO 4、Li 3VO 4、Li 2MoO 3、Li 2RuO 3、Li 2MnO 2、Li 2NiO 2、Li 2Cu xNi 1-xM yO 2中的至少一种，其中0＜x≤1，0≤y＜0.1，且M为选自Zn、Sn、Mg、Fe和Mn中的至少一种。从提高二次电池的比容量和倍率性能尤其是高温存储后的倍率性能的观点考虑，所述补锂剂优选包括选自Li 6CoO 4、Li 5FeO 4、Li 2NiO 2、Li 2CuO 2和Li 2Cu 0.6Ni 0.4O 2中的至少一种。
在一些实施方式中，正极活性材料层还可以选择性地包括粘结剂。作为示例，所述粘结剂可以包括选自由聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏二氟乙烯-四氟乙烯 -丙烯三元共聚物、偏二氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂构成的组中的至少一种。
在一些实施方式中，正极活性材料层还可以选择性地包括导电剂。作为示例，可以使用本领域通常使用的导电剂。所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳纳米管、碳纳米棒、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备涂布在正极集流体上的正极活性材料层：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂布在正极集流体上，经烘干、冷压等工序后，即可以得到涂布在正极集流体上的正极活性材料层。可替代地，在另一个实施方式中，可以通过如下方式来制造涂布在正极集流体上的正极活性材料层：将用于形成正极活性材料层的正极浆料流延在单独的载体上，然后将通过从载体剥离而获得的膜层压在正极集流体上。之后，可以参照本申请的电极极片的制备方法在正极活性材料层上涂布无机隔离层。
[负极极片]
负极极片可以包括负极集流体以及设置在负极集流体的至少一个表面上的负极活性材料层和上述的无机隔离层。所述负极活性材料层可以包括负极活性材料以及可选的粘结剂、导电剂和其他助剂。
作为示例，负极集流体具有在其自身厚度方向上相对的两个表面，负极活性材料层设置在负极集流体的相对的两个表面中的任一者或两者上。
在一些实施方式中，所述负极集流体可以采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可以包括高分子材料基材和形成于高分子材料基材的至少一个表面上的金属层。复合集流体可以通过将金属材料(如铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可以采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可以包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可以选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可以选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可以被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极活性材料层还可以选择性地包括粘结剂。所述粘结剂可以选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极活性材料层还可以选择性地包括导电剂。导电剂可以选自超导碳、乙炔黑、炭黑、科琴黑、碳纳米管、碳纳米棒、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极活性材料层还可以选择性地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备涂布在负极集流体上的负极活性材料层：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂布在负极集流体上，经烘干、冷压等工序后，即可以得到涂布在负极集流体上的负极活性材料层。可替代地，在另一个实施方式中，可以通过如下方式来制造负极活性材料层：将用于形成负极活性材料层的负极浆料流延在单独的载体上，然后将通过从载体剥离而获得的膜层压在负极集流体上。之后，可以参照本申请的电极极片的制备方法在负极活性材料层上涂布无机隔离层。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有 具体的限制，可以根据需求进行选择。例如，电解质可以是液态的或凝胶态的。
此外，本申请的实施方式的电解质包括添加剂。所述添加剂可以包括本领域中常用的添加剂。所述添加剂可以包括例如卤代碳酸亚烷基酯类化合物(如二氟碳酸亚乙酯)、吡啶、亚磷酸三乙酯、三乙醇胺、环醚、乙二胺、(缩)甘醇二甲醚类、六甲基磷酸三酰胺、硝基苯衍生物、硫、醌亚胺染料、N-取代的唑烷酮、N,N-取代的咪唑烷、乙二醇二烷基醚、铵盐、吡咯、2-甲氧基乙醇或三氯化铝。此时，基于电解质的总重量，可以以0.1重量％至5重量％的量包含添加剂或者由本领域技术人员根据实际需要调整添加剂的用量。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可以选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可以选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，二次电池可以包括外包装。该外包装可以用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料。作为塑料，可以列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，外包装可以包括壳体51和盖板53。其中，壳体51可以包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可以经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可以根据实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可以根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池5沿电池模块4的长度方向依次排列设置。当然，多个二次电池5也可以按照其他任意的方式进行排布。进一步地，可以通过紧固件将所述多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间内。
在一些实施方式中，上述电池模块还可以组装成电池包。电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可以根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块或电池包中的至少一种。所述二次电池、电池模块或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、 储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下详细说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商的，均为可以通过市购获得的常规产品。
实施例1
(1)正极极片的制备
将正极活性材料磷酸铁锂、粘结剂聚偏二氟乙烯(PVDF)、导电剂乙炔黑按照质量比为97:2:1溶于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料；之后将正极浆料均匀涂布于正极集流体铝箔上，之后经过烘干和冷压得到正极活性材料层。然后，将作为第一无机颗粒的勃姆石(体积中值粒径Dv50为200nm)、作为造孔剂的碳酸氢铵、作为分散剂的NMP和作为粘结剂的丁苯橡胶(SBR)以40:8:50:2的重量比进行混合并充分分散，从而得到用于形成第一无机隔离层的浆料。然后，将上述浆料涂布在上述正极活性材料层上，并将得到的产物在30℃的烘箱中干燥以除去40重量％的NMP。然后，在得到的初步干燥的第一无机隔离层上，涂布用于形成第二无机隔离层的浆料，所述浆料以48:2:50的重量比包括作为第二无机颗粒的勃姆石(体积中值粒径Dv50为200nm)、作为第二粘结剂的SBR和作为第二分散剂的NMP。之后，在50℃下对得到的产物进行热处理以进行造孔，由此得到正极极片。该正极极片的物理参数如下表1所示。
(2)负极极片的制备
将负极活性材料人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照质量比为95:2:2:1溶于溶剂去离子水中并与溶剂去离子水均匀混合后制备成负极浆料；然后将负极浆料均匀涂布在负极集流体铜箔上，之后经过烘干、冷压、分切得到负极极片。
(3)电解液的制备
在氩气气氛手套箱中(气氛：H 2O<0.1ppm，O 2<0.1ppm)，将1mol/L LiPF 6溶解于有机溶剂(EC/DMC/EMC＝1/1/1(质量比))中，并如下表1中所示添加电解液添加剂，搅拌均匀后得到相应的电解液。
(4)二次电池的制备
将上述正极极片、负极极片按照一层阳极叠上一层阴极结构顺序，使作为隔离膜的无机隔离层处于正、负极活性材料层之间起到隔离的作用，然后多层叠加后得到电极组件；将电极组件置于电池壳体铝塑膜袋中，干燥后注入上述电解液，再经过化成、静置等工艺制得二次电池。
实施例2～6和比较例1～4
除了如下表1中所示调节浆料的涂布量以调节无机隔离层的厚度、调节造孔剂在第一无机隔离层和第二无机隔离层中的含量以外，以与实施例1相同的方式制备了实施例2～6和比较例1～4的二次电池。
实施例7
除了在制备过程中的步骤(a)之后对极片进行冷压(压力为10t)以外，以与实施例1相同的方式制备了实施例7的二次电池。
接下来，对电极极片的测试方法进行说明。
(1)孔道孔径的测试方法
按照GB/T1967-1966标准，利用JW-K型孔径测试仪(北京精微高博科学技术有限公司)对得到的极片进行孔径测量。
(2)第一无机隔离层和第二无机隔离层的孔隙率的测试方法
通过水煮法测量第一无机隔离层和第二无机隔离层的孔隙率。具体地，称量无机隔离层试样的干重m0，饱和试样水中悬浮重m1和饱和试样质量m2，利用公式P＝(m2-m0)/(m2-m1)计算得到孔隙率。
表1电极极片参数及电池性能
Figure PCTCN2021121955-appb-000001
接下来，对二次电池的测试方法进行说明。
(1)K值的测定
在测试温度50℃下，测量二次电池的开路电压OCV1(电压值1)，然后在50℃恒温烘箱中放置24小时，之和测试二次电池的开路电压OCV2，利用公式K＝(ocv2-ocv1)/24计算二次电池的K值。K值表示了电池自放电率的大小。测量结果示于上表1中。
(2)比容量的测定
在25℃下，将锂离子电池以0.33C恒流充电至3.65V，然后以3.65V恒压充电至电流小于0.05C，然后将锂离子电池以0.33C恒流放电至2.5V，记录其实际容量。根据测得的实际容量与电池的质量计算锂离子电池的比容量，结果示于上表1中。
(3)电池阻抗的测定
通过WK65120B测试仪、通过直流放电内阻测量法测试上述实施例和比较例得到的二次电池的阻抗。测量结果示于上表1中。
由上述表1中的实施例2与比较例3的比较可知，当无机隔离层的厚度一定时，通过对无机隔离层进行造孔，可以增加电池的质量能量密度。由上述表1中的实施例3与实施例5的比较可知，当第一无机隔离层的厚度太厚时，会造成电池的能量密度降低并且阻抗和自放电率一定程度上增加。因此，第一无机隔离层的厚度优选在2μm～10μm的范围内。
由上述表1中的实施例1和3与比较例1和实施例6的比较可知，当第一无机隔离层和第二无机隔离层的厚度之和较小时，电池的自放电率明显增大。相反地，当第一无机隔离层和第二无机隔离层的厚度之和较大时，电池的阻抗增大并且质量能量密度显著减小。因此，第一无机隔离层和第二无机隔离层的厚度之和优选在7μm～30μm的范围内。
由上述表1中的实施例2与比较例2的比较可知，当在造孔阶段在整体无机隔离层中添加造孔剂时，在无机隔离层中会形成楔形孔道。而且，在无机隔离层厚度一定的情况下，楔形孔道开口较大一端的孔径明显大于本申请实施例2中的孔径。相应地，这会造成电池的自放电率明显增加。因此，在本申请中，优选在第一无机隔离层中添加造孔剂对第一无机隔离层和第二无机隔离层进行造孔，以在第二无机隔离层中形成孔径均一的孔道。
由上述表1中的实施例4与比较例4的比较可知，当在第二无机隔离层中形成孔径大于600nm的孔道时，电池的自放电率显著增加。因此，无机隔离层中孔道的孔径优选为300nm～600nm。
由上述表1中的实施例1-4可知，当第一无机隔离层的厚度、第一无机隔离层和第二无机隔离层的厚度之和、无机隔离层的孔隙率以及孔道的孔径均在本申请的范围内时，本申请的二次电池具有优异的质量能量密度以及低的自放电率和阻抗。
由上述表1中的实施例1和7的比较可知，对极片进行压制可以提高二次电池的能量 密度。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (26)

  1. 一种电极极片，所述电极极片包括集流体和设置在所述集流体的至少一个表面上的活性材料层，
    所述活性材料层上依次形成有第一无机隔离层和第二无机隔离层，
    所述第一无机隔离层包含多个孔道并且所述孔道的孔径为300nm～600nm，
    所述多个孔道各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述第二无机隔离层，并且
    所述第二无机隔离层中的所述孔道的孔径是均一的。
  2. 根据权利要求1所述的电极极片，其中，所述第一无机隔离层和所述第二无机隔离层的厚度之和为7μm～30μm。
  3. 根据权利要求2所述的电极极片，其中，所述第一无机隔离层的厚度为2μm～10μm。
  4. 根据权利要求1～3中任一项所述的电极极片，其中，所述第一无机隔离层和所述第二无机隔离层的孔隙率各自为40％～55％。
  5. 根据权利要求1～4中任一项所述的电极极片，其中，所述第一无机隔离层和所述第二无机隔离层各自包括无机颗粒和粘结剂。
  6. 根据权利要求5所述的电极极片，其中，所述第一无机隔离层包括90重量％～95重量％的所述无机颗粒和5重量％～10重量％的所述粘结剂；并且
    所述第二无机隔离层包括95重量％～98重量％的所述无机颗粒和2重量％～5重量％的所述粘结剂。
  7. 根据权利要求5或6所述的电极极片，其中，所述无机颗粒的体积中值粒径Dv50为30nm～500nm。
  8. 根据权利要求5～7中任一项所述的电极极片，其中，所述无机颗粒包括选自由氧 化硅、氧化铝、勃姆石、氧化镁、氧化钛、氧化锌、氧化铝镁构成的组中的至少一种。
  9. 根据权利要求5～8中任一项所述的电极极片，其中，所述粘结剂包括选自由羧甲基纤维素、聚偏二氟乙烯、丁苯橡胶、聚酰亚胺、聚乙烯、聚偏二氟乙烯-六氟丙烯共聚物构成的组中的至少一种。
  10. 根据权利要求1～9中任一项所述的电极极片，其中，所述电极极片为正极极片或负极极片。
  11. 一种二次电池，其包括权利要求1～10中任一项所述的电极极片。
  12. 一种电池模块，其包括权利要求11所述的二次电池。
  13. 一种电池包，其包括权利要求12所述的电池模块。
  14. 一种用电装置，其包括选自权利要求11所述的二次电池、权利要求12所述的电池模块或权利要求13所述的电池包中的至少一种。
  15. 一种电极极片的制备方法，所述方法包括如下步骤：
    (a)在集流体的至少一个表面上涂布活性材料层，
    (b)在所述活性材料层上涂布用于形成第一无机隔离层的浆料，所述浆料包括第一无机颗粒、第一粘结剂、第一分散剂和造孔剂，
    (c)在低于所述造孔剂的造孔温度的温度下对涂布的所述用于形成第一无机隔离层的浆料进行干燥以除去30重量％～60重量％的所述第一分散剂，
    (d)在步骤(c)之后得到的初步干燥的第一无机隔离层上，涂布用于形成第二无机隔离层的浆料，所述浆料包括第二无机颗粒、第二粘结剂和第二分散剂，
    (e)在所述造孔剂的造孔温度下对在步骤(d)之后得到的产物进行热处理，以得到包括所述集流体、所述活性材料层、所述第一无机隔离层和所述第二无机隔离层的电极极片，
    其中所述第一无机隔离层包含多个孔道并且所述孔道的孔径为300nm～600nm，
    所述多个孔道各自从所述第一无机隔离层朝向所述第二无机隔离层延伸并贯穿所述第二无机隔离层，并且
    所述第二无机隔离层中的所述孔道的孔径是均一的。
  16. 根据权利要求15所述的电极极片的制备方法，其中，所述用于形成第一无机隔离层的浆料中的所述第一无机颗粒、所述第一粘结剂、所述第一分散剂和所述造孔剂的含量各自为35重量％～45重量％，1重量％～4重量％，45重量％～55重量％，5重量％～10重量％，并且
    所述用于形成第二无机隔离层的浆料中的所述第二无机颗粒、所述第二粘结剂和所述第二分散剂的含量各自为40重量％～55重量％，1重量％～5重量％，40重量％～55重量％。
  17. 根据权利要求15或16所述的电极极片的制备方法，其中，所述方法还包括在步骤(a)和/或步骤(e)之后进行压制的步骤。
  18. 根据权利要求15～17中任一项所述的电极极片的制备方法，其中，所述第一无机隔离层和所述第二无机隔离层的厚度之和为7μm～30μm。
  19. 根据权利要求15～18中任一项所述的电极极片的制备方法，其中，所述第一无机隔离层的厚度为2μm～10μm。
  20. 根据权利要求15～19中任一项所述的电极极片的制备方法，其中，所述第一无机隔离层和所述第二无机隔离层的孔隙率各自为40％～55％。
  21. 根据权利要求15～20中任一项所述的电极极片的制备方法，其中，所述第一无机颗粒和所述第二无机颗粒的体积中值粒径Dv50各自为30nm～500nm。
  22. 根据权利要求15～21中任一项所述的电极极片的制备方法，其中，所述第一无机颗粒和所述第二无机颗粒各自包括选自由氧化硅、氧化铝、勃姆石、氧化镁、氧化钛、氧化锌、氧化铝镁构成的组中的至少一种。
  23. 根据权利要求15～22中任一项所述的电极极片的制备方法，其中，所述第一粘结剂和所述第二粘结剂各自包括选自由羧甲基纤维素、聚偏二氟乙烯、丁苯橡胶、聚酰亚胺、聚乙烯、聚偏二氟乙烯-六氟丙烯共聚物构成的组中的至少一种。
  24. 根据权利要求15～23中任一项所述的电极极片的制备方法，其中，所述第一分散剂和所述第二分散剂各自包括选自由水、甲醇、乙醇、正丙醇、异丙醇、丙酮、N-甲基吡咯烷酮构成的组中的至少一种。
  25. 根据权利要求15～24中任一项所述的电极极片的制备方法，其中，所述造孔剂包括选自由碳酸铵和碳酸氢铵构成的组中的至少一种。
  26. 根据权利要求15～25中任一项所述的电极极片的制备方法，其中，所述电极极片为正极极片或负极极片。
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