WO2023221380A1 - 负极极片及其制备方法、二次电池、电池模块、电池包及用电装置 - Google Patents

负极极片及其制备方法、二次电池、电池模块、电池包及用电装置 Download PDF

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WO2023221380A1
WO2023221380A1 PCT/CN2022/124775 CN2022124775W WO2023221380A1 WO 2023221380 A1 WO2023221380 A1 WO 2023221380A1 CN 2022124775 W CN2022124775 W CN 2022124775W WO 2023221380 A1 WO2023221380 A1 WO 2023221380A1
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negative electrode
layer
polymer
lithium
battery
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PCT/CN2022/124775
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English (en)
French (fr)
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刘晓梅
李成凤
杨龙飞
陈永爱
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宁德时代新能源科技股份有限公司
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • 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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • 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
    • 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 secondary batteries, in particular to negative electrode plates and preparation methods thereof, secondary batteries, battery modules, battery packs and electrical devices.
  • Prelithiation technology can be divided into negative electrode lithium supplement and positive electrode lithium supplement.
  • positive electrode lithium supplementation is widely used because it is more operable, safer and has no special requirements for equipment than negative electrode lithium supplementation.
  • positive electrode lithium supplementation may cause the proportion of active materials in the positive electrode to decrease. For example, using When Li 5 FeO 4 is used, the content needs to reach 7%, and the product after lithium supplementation is inactive, which affects the further improvement of the energy density of lithium-ion batteries.
  • the negative electrode plate can realize safe lithium replenishment and can effectively improve the traditional
  • the negative electrode lithium supplement is not safe and the positive electrode lithium supplement has limited improvement in energy density.
  • a first aspect of the present application provides a negative electrode sheet, which includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode film layer includes a stacked The negative active material layer, lithium supplement layer and polymer layer;
  • the negative active material layer is located on the negative current collector
  • the lithium replenishing layer is located on a side of the negative active material layer away from the negative current collector
  • the polymer layer is located on the lithium replenishing layer. The side facing away from the negative active material layer.
  • this application at least includes the following beneficial effects:
  • lithium is replenished by setting a lithium replenishing layer on the surface of the negative active material layer, which avoids the complex process of replenishing lithium by coating the surface of the negative active material particles in the traditional technology and the poor compatibility with the aqueous negative electrode preparation process. problem; by arranging a polymer layer on the surface of the lithium replenishment layer, it can effectively prevent the lithium replenishment layer from reacting with water or oxygen, thereby improving the safety and lithium replenishment efficiency of the negative electrode.
  • the polymer layer is made of polymethyl methacrylate, polyethylene oxide, polyacrylonitrile, polystyrene, perfluoropolyether, dimethyl silicone oil, and methyl methacrylate.
  • the polymer layer includes a first polymer and a second polymer
  • the first polymer includes polymethyl methacrylate, polyethylene oxide, polyacrylonitrile, polystyrene, and One or more block copolymers of polymethylmethacrylate-propylene sulfite
  • the second polymer includes perfluoropolyether and/or dimethyl silicone oil.
  • the mass ratio of the first polymer and the second polymer is (1-9):1.
  • the negative electrode film layer is provided on both sides of the negative electrode current collector.
  • the thickness of the polymer layer included in the negative electrode sheet is 1 ⁇ m to 12 ⁇ m.
  • the material of the lithium supplement layer includes elemental lithium.
  • the lithium replenishing layer includes several mutually parallel stripe-shaped hollow spaces.
  • the width of the stripe-shaped hollow spaces is 0.1 ⁇ m to 100 ⁇ m.
  • the width of the solid part between them is 50 ⁇ m ⁇ 10mm.
  • the thickness of each lithium replenishing layer is 0.1 ⁇ m to 15 ⁇ m.
  • a second aspect of the present application provides a secondary battery, the manufacturing method of which includes immersing the electrode assembly in an electrolyte;
  • the electrode assembly includes the negative electrode piece, the isolation film and the positive electrode piece described in any of the above embodiments, and the isolation film is disposed between the negative electrode piece and the positive electrode piece.
  • the mass of the polymer layer accounts for 0.1% to 4% of the sum of the mass of the polymer layer and the electrolyte.
  • a third aspect of the present application provides a battery module, which includes the secondary battery described in one or more of the foregoing embodiments.
  • a fourth aspect of the present application provides a battery pack, which includes the aforementioned battery module.
  • a fifth aspect of the present application provides an electrical device, which includes one or more of the secondary battery described in one or more of the aforementioned embodiments, the aforementioned battery module, and the aforementioned battery pack.
  • the sixth aspect of the present application provides a method for preparing the negative electrode sheet according to any of the preceding embodiments, which includes the following steps:
  • a polymer layer is formed on the surface of the lithium supplement layer.
  • the operation of forming the polymer layer on the surface of the lithium supplement layer includes the following steps:
  • the polymer is dissolved in an organic solvent to prepare a polymer solution, the polymer solution is applied on the surface of the lithium supplement layer to form a polymer coating, and the polymer layer is obtained after drying.
  • the organic solvent includes dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 1,3-dioxopentane, diphenyl carbonate, propylene sultone, propylene -One or more of 1,3 sultone, triphenyl phosphate, triphenyl phosphite and sulfolane.
  • the mass percentage of the polymer in the polymer solution is 1% to 15%.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the 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.
  • Figure 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 an embodiment of the present application shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
  • first and second are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features. Therefore, features defined as “first” and “second” may explicitly or implicitly include at least one of these features.
  • “multiple” means at least two, such as two, three, etc., unless otherwise explicitly and specifically limited.
  • everal means at least one, such as one, two, etc., unless otherwise expressly and specifically limited.
  • the technical features described in open format include closed technical solutions composed of the listed features, and also include open technical solutions including the listed features.
  • the above numerical interval is considered to be continuous and includes the minimum value and maximum value of the range, as well as every value between such minimum value and maximum value. Further, when a range refers to an integer, every integer between the minimum value and the maximum value of the range is included. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to include any and all subranges subsumed therein.
  • the percentage content involved in this application refers to mass percentage for solid-liquid mixing and solid-solid phase mixing, and refers to volume percentage for liquid-liquid phase mixing.
  • the percentage concentrations mentioned in this application refer to the final concentration unless otherwise specified.
  • the final concentration refers to the proportion of the added component in the system after adding the component.
  • the temperature parameters in this application allow for constant temperature treatment or treatment within a certain temperature range.
  • the thermostatic treatment described allows the temperature to fluctuate within the accuracy of the instrument control.
  • lithium replenishment is often carried out by coating the surface of the negative electrode active material with a lithium replenishing agent.
  • the negative electrode lithium replenishing agent is usually elemental lithium, which is very reactive and easily reacts with water and oxygen in the air, so it cannot
  • the anode preparation process that is compatible with water systems requires the use of organic solvents, causing more environmental pollution.
  • the polymer protective layer is soluble in the electrolyte, after the injection liquid is dissolved, the active material particles will The adhesion between them will become worse. If the polymer protective layer cannot be dissolved in the electrolyte, it will increase the impedance of the battery and reduce the electrical performance.
  • a negative electrode sheet which includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode film layer includes a stacked negative electrode active material layer, Lithium supplement layer and polymer layer;
  • the negative active material layer is located on the negative current collector
  • the lithium replenishing layer is located on the side of the negative active material layer facing away from the negative active material layer
  • the polymer layer is located on the side of the lithium replenishing layer facing away from the negative active material layer.
  • lithium is replenished by setting a lithium replenishing layer on the surface of the negative active material layer, which avoids the complex process of replenishing lithium by coating the surface of the negative active material particles in the traditional technology and the related problems.
  • the inventor found that when the negative electrode sheet of the present application meets the above design conditions and optionally meets one or more of the following conditions, the safety of lithium supplementation of the negative electrode can be further improved. and lithium supplementation efficiency.
  • the polymer layer is made of polymethyl methacrylate (PMMA), polyethylene oxide (PEO), polyacrylonitrile (PAN), polystyrene (PS), and perfluoropolyether (PEFE). , dimethyl silicone oil (PDMS) and one or more of methyl methacrylate-propylene sulfite block copolymers.
  • PMMA polymethyl methacrylate
  • PEO polyethylene oxide
  • PAN polyacrylonitrile
  • PS polystyrene
  • PEFE perfluoropolyether
  • PDMS dimethyl silicone oil
  • the polymer layer will dissolve in the electrolyte, which can avoid the increase in battery impedance caused by the presence of the protective layer.
  • the polymer layer includes a first polymer and a second polymer, the first polymer including polymethyl methacrylate, polyethylene oxide, polyacrylonitrile, polystyrene, and polymethyl methacrylate. - one or more block copolymers of propylene sulfite, the second polymer comprising perfluoropolyether and/or dimethicone.
  • the conductivity is high, which helps to improve the electrical performance of the battery;
  • the second polymer has poor conductivity, but has good barrier properties against moisture and gas, and can effectively protect the lithium replenishing layer from moisture. and oxygen erosion.
  • the combined use of the first polymer and the second polymer can both protect the lithium replenishing layer and improve the electrical performance of the battery.
  • the mass ratio of the first polymer to the second polymer is (1 ⁇ 9):1.
  • the mass ratio of the first polymer to the second polymer can also be, for example, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1: 5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8 or 1:8.5. Controlling the mass ratio of the two within an appropriate range can balance the protective performance of the lithium supplement layer and the electrical performance of the battery to a greater extent.
  • negative electrode film layers are provided on both sides of the negative electrode current collector.
  • the polymer layer included in the negative electrode sheet has a thickness of 1 ⁇ m to 12 ⁇ m.
  • the thickness of the polymer layer can also be, for example, 1.5 ⁇ m, 2 ⁇ m, 2.5 ⁇ m, 3 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, 4.5 ⁇ m, 5 ⁇ m, 5.5 ⁇ m, 6 ⁇ m, 6.5 ⁇ m, 7 ⁇ m, 7.5 ⁇ m, 8 ⁇ m, 8.5 ⁇ m, 9 ⁇ m, 9.5 ⁇ m, 10 ⁇ m, 10.5 ⁇ m, 11 ⁇ m or 11.5 ⁇ m.
  • the thickness of the polymer layer is set within an appropriate range.
  • the concentration of the polymer in the electrolyte is moderate. Even if the protective effect is met, the viscosity of the electrolyte will not be too high due to excessive concentration, which cannot meet the basic requirements. Usage requirements.
  • the "thickness of the polymer layer” mentioned here refers to the total thickness of the polymer layer included in the entire negative electrode piece. If there is only one polymer layer, the thickness of the polymer layer is 1 ⁇ m ⁇ 12 ⁇ m. If there are two polymer layer, the sum of the thicknesses of the two polymer layers is 1 ⁇ m to 12 ⁇ m. When there are two polymer layers, the thicknesses of the two polymer layers may be equal or unequal.
  • the material of the lithium supplement layer includes elemental lithium.
  • the lithium replenishing layer includes several mutually parallel stripe-shaped hollow gaps, the width of the stripe-shaped hollow gaps is 0.1 ⁇ m ⁇ 100 ⁇ m, and the width of the solid portion between two adjacent stripe-shaped hollow gaps is 50 ⁇ m ⁇ 10mm.
  • the width of the stripe-shaped hollow gaps may be, for example, 10 ⁇ m, 20 ⁇ m, 30 ⁇ m, 40 ⁇ m, 50 ⁇ m, 60 ⁇ m, 70 ⁇ m, 80 ⁇ m or 90 ⁇ m; the width of the solid portion between two adjacent strip-shaped hollow gaps may be, for example, 100 ⁇ m, 200 ⁇ m, 300 ⁇ m, 400 ⁇ m, 500 ⁇ m, 600 ⁇ m, 700 ⁇ m, 800 ⁇ m, 900 ⁇ m, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5 mm, 9mm or 9.5mm.
  • the structure of the lithium-replenishing layer containing the lithium-replenishing layer is similar to a zebra crossing.
  • the stripes with the lithium-replenishing layer and the hollow gaps without the lithium-replenishing layer are arranged parallel to each other, which can make the electrode plate more wettable to the electrolyte, thus conducive to the improvement of battery performance.
  • Appropriate stripe width and gap width can take into account both lithium replenishment efficiency and wettability.
  • the thickness of each lithium replenishing layer is 0.1 ⁇ m ⁇ 15 ⁇ m.
  • the thickness of the lithium supplement layer can be, for example, 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 2.5 ⁇ m, 3 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, 4.5 ⁇ m, 5 ⁇ m, 5.5 ⁇ m, 6 ⁇ m, 6.5 ⁇ m, 7 ⁇ m, 7.5 ⁇ m, 8 ⁇ m, 8.5 ⁇ m, or 9 ⁇ m. , 9.5 ⁇ m, 10 ⁇ m, 10.5 ⁇ m, 11 ⁇ m, 11.5 ⁇ m, 12 ⁇ m, 12.5 ⁇ m, 13 ⁇ m, 13.5 ⁇ m, 14 ⁇ m or 14.5 ⁇ m. Controlling the thickness of the lithium replenishment layer within an appropriate range can more fully replenish lithium for the battery at a lower cost.
  • the "thickness of each lithium supplement layer” mentioned here refers to the thickness of a single lithium supplement layer. If there is more than one lithium supplement layer in the pole piece, the total thickness of the lithium supplement layer is the thickness of each lithium supplement layer. sum.
  • Embodiments of the present application also provide a secondary battery, the manufacturing method of which includes immersing the electrode assembly in an electrolyte;
  • the electrode assembly includes the negative electrode piece, the isolation film and the positive electrode piece of any of the above embodiments, and the isolation film is disposed between the negative electrode piece and the positive electrode piece.
  • the polymer layer in the negative electrode plate will dissolve in the electrolyte to avoid increasing the impedance of the battery.
  • the mass of the polymer layer accounts for 0.1% to 4% of the sum of the mass of the polymer layer and the electrolyte.
  • the proportion can also be 0.2%, 0.35%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8 %, 3%, 3.2%, 3.4%, 3.5%, 3.6% or 3.8%.
  • the mass proportion of the polymer layer is within an appropriate range, which can take into account the protective performance of the lithium replenishing layer before dissolution and the viscosity of the electrolyte after dissolution, so as to avoid adverse effects on battery performance.
  • the total mass ratio of the two polymers is 0.1% to 4%.
  • the first polymer and the second polymer coexist in the polymer layer, and negative electrode film layers are provided on both sides of the current collector.
  • the thickness of the polymer layer in the aforementioned embodiment is recorded as D ( ⁇ m)
  • the mass of the first polymer as a percentage of the sum of the masses of the polymer layer and the electrolyte is expressed as wt 1 (%)
  • the mass of the first polymer is expressed as wt 1 (%).
  • the percentage of the mass of a polymer to the sum of the mass of the polymer layer and the electrolyte is recorded as wt 2 (%), the total mass of the electrolyte and polymer layer is recorded as m (g), and the length of the negative electrode piece is recorded
  • wt 2 The percentage of the mass of a polymer to the sum of the mass of the polymer layer and the electrolyte is recorded as wt 2 (%), the total mass of the electrolyte and polymer layer is recorded as m (g), and the length of the negative electrode piece is recorded.
  • the total thickness of the two polymer layers ranges from 1 ⁇ m to 12 ⁇ m. At this time, there is no obvious negative impact on the viscosity and conductivity of the electrolyte after the polymer is dissolved, and the polymer layer has a good protective effect on the lithium replenishing layer before dissolution.
  • An embodiment of the present application also provides a battery module, which includes the secondary battery of one or more of the foregoing embodiments.
  • An embodiment of the present application also provides a battery pack, which includes the aforementioned battery module.
  • An embodiment of the present application also provides an electrical device, which includes one or more of the secondary battery of one or more of the foregoing embodiments, the foregoing battery module, and the foregoing battery pack.
  • the embodiments of the present application also provide a method for preparing the negative electrode sheet of any of the preceding embodiments, which includes the following steps:
  • a polymer layer is formed on the surface of the lithium supplement layer.
  • the operation of forming a polymer layer on the surface of the lithium replenishing layer includes the following steps:
  • the polymer is dissolved in an organic solvent to prepare a polymer solution, the polymer solution is applied on the surface of the lithium supplement layer to form a polymer coating, and the polymer layer is obtained after drying.
  • the application process includes one or more of spraying, coating, infiltration, and microgravure. Coating is preferred.
  • the organic solvent includes dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), 1,3-dioxopentane, diphenyl carbonate, propylene sulfonic acid
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • 1,3-dioxopentane diphenyl carbonate
  • diphenyl carbonate propylene sulfonic acid
  • DEC is preferred.
  • the mass percentage of the polymer in the polymer solution is 1% to 15%.
  • the mass percentage of the polymer can also be, for example, 2%, 4%, 6%, 8%, 10%, 12% or 14%.
  • a polymer solution of appropriate concentration can be applied more uniformly with the fewest possible application times.
  • a secondary battery is provided.
  • a secondary battery typically includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the cathode active material may be a cathode active material known in the art for batteries.
  • the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • 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 , 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 (can also be abbreviated to NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (can also be abbreviated to NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (can also be abbreviated to 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 Li Li
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon. At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • composites of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate and carbon.
  • At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components 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 positive electrode piece can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode piece is selected from the negative electrode pieces provided in the first aspect of this application.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material in the negative active material layer may be a negative active material for batteries known in the art.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode film layer optionally further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative active material layer can be prepared by dispersing the above-mentioned components used to prepare the negative electrode sheet, such as the negative active material, conductive agent, binder and any other components in a solvent (such as (ionized 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, a negative electrode active material layer is obtained.
  • a solvent such as (ionized water
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is an electrolyte solution.
  • the electrolyte solution includes electrolyte salts and solvents.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.
  • the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl 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 electrolyte optionally further includes additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • 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 shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • 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 may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 1 shows a square-structured secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into 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 specific actual needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. 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 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • 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. Those skilled in the art can select the specific number 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 2 and a lower box 3 .
  • the upper box 2 can be covered with the lower box 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 electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device.
  • the electrical devices may include mobile equipment, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
  • mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc. , but not limited to this.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • FIG. 6 shows an electrical device 6 as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • the device may be a mobile phone, a tablet, a laptop, etc.
  • the device is usually required to be thin and light, and secondary batteries can be used as power sources.
  • the weight described in the description of the embodiments of this application may be mass units well-known in the field of chemical engineering such as ⁇ g, mg, g, kg, etc. If the manufacturer of the reagents or instruments used is not indicated, they are all conventional products that can be purchased commercially.
  • Step a Mix the negative active material artificial graphite (gram capacity: 340mAh/g), conductive agent acetylene black, binder SBR (styrene-butadiene rubber latex), and binder CMC (sodium carboxymethyl cellulose) in a weight ratio of 95 :1.5:3.1:0.4, add the solvent deionized water, stir thoroughly and mix evenly to obtain the negative electrode slurry, and then coat it on both surfaces of the negative electrode current collector copper foil, where the coating amount of the negative electrode slurry is 0.136 g/1540.25mm 2 (based on weight excluding solvent), dried and cold pressed;
  • Step b Composite two pieces of 10 ⁇ m thick lithium foil (gram capacity: 3861mAh/g) to the two surfaces of the product obtained in step a by rolling to form two lithium replenishing layers, in which the amount of lithium foil is 3.45 mg/1540.25mm 2 ; the obtained lithium supplement layer has mutually parallel stripe-shaped hollow spaces, the width of the striped hollow spaces is 50 ⁇ m, and the width of the solid part between two adjacent striped hollow spaces is 200 ⁇ m.
  • Step c Dissolve 100g PMMA (polymethyl methacrylate) in 900g DMC (dimethyl carbonate) to obtain a PMMA solution with a mass fraction of 10%, and cover the solution on both sides of the product obtained in step b by spraying. surface, and air-dried at 25°C for 30 minutes to obtain the negative electrode piece.
  • PMMA polymethyl methacrylate
  • DMC dimethyl carbonate
  • Polyethylene porous membrane is used as the isolation membrane.
  • Example 1 The process is the same as in Example 1 (if it contains two polymers, the two polymers are dissolved together to prepare a solution), but the ratio, thickness, solvent used and preparation process of the polymer layer are different. See Table 1 for details. .
  • the lithium replenishing layer prepared in step b is a solid lithium replenishing layer without striped hollow spaces.
  • Example 2 It is basically the same as Example 1, except that when preparing the negative electrode piece in step (2), the solute PMMA is not included in step c.
  • step c is not included when preparing the negative electrode piece in step (2).
  • the sandwich electrodes were punched into small stacks of 41mm ⁇ 49.5mm, and the copper foil with lithium coating on the surface was punched into 43.5mm ⁇ 51mm.
  • the sandwich structure lithium sheet, isolation film, sandwich electrode, isolation film, and lithium sheet are stacked in order, so that the isolation film is between the positive and negative electrodes to play an isolation role, and a laminated bare cell is obtained.
  • the bare battery core is placed in the outer package, the prepared electrolyte is injected and packaged to obtain a lithium-ion secondary battery. Then use the sandwich structure electrode as the positive electrode and the lithium electrode as the negative electrode, charge it to 2V at 0.04C (1C, that is, the current value that completely discharges the theoretical capacity within 1 hour), and detect its charging capacity C1 (unit: mAh).
  • Lithium efficiency of lithium-ion secondary battery C1/(41 ⁇ 49.5/1540.25 ⁇ m ⁇ 2 ⁇ 3.861) ⁇ 100%, where m is the total amount of lithium supplement (mg)
  • the lithium-ion secondary battery At 25°C, first charge the lithium-ion secondary battery with a constant current of 1C (that is, the current value that completely discharges the theoretical capacity within 1 hour) to a voltage of 3.65V, and then charge with a constant voltage of 3.65V to a current of 0.05C. After leaving it for 5 minutes, discharge the lithium-ion secondary battery at a constant current of 1C until the voltage is 2.5V. This is a charge and discharge cycle process, and the discharge capacity this time is the discharge capacity of the first cycle.
  • the lithium-ion secondary battery is subjected to multiple cycle charge and discharge tests according to the above method until the discharge capacity of the lithium-ion secondary battery decays to 80%, and the number of cycles of the lithium-ion secondary battery is recorded.
  • the lithium-ion secondary battery At 60°C, first charge the lithium-ion secondary battery with a constant current of 1C (that is, the current value that completely discharges the theoretical capacity within 1 hour) until the voltage is 3.65V, and then charge with a constant voltage of 3.65V until the current is 0.05C. After leaving it for 5 minutes, discharge the lithium-ion secondary battery at a constant current of 1C until the voltage is 2.5V. This is a charge and discharge cycle process, and the discharge capacity this time is the discharge capacity of the first cycle.
  • the lithium-ion secondary battery was subjected to multiple cycle charge and discharge tests according to the above method, and the discharge capacity of the 500th cycle was detected.
  • Capacity retention rate of a lithium-ion secondary battery after 500 cycles at 60° C. (discharge capacity of the 500th cycle/discharge capacity of the first cycle) ⁇ 100%.
  • Comparing Examples 3 and 11 to 15 it can be seen that when different types of solvents are used to dissolve the polymer for coating, the performance of the final battery is slightly different. This may be because some solvents remain after the polymer layer is dried. Among them, DEC Works best as a solvent. Comparing Examples 3 and 16 to 18, it can be seen that different application processes have different effects on battery performance. Among them, the coating process has the best effect, followed by spraying. Comparing Example 3 and Example 19, it can be seen that the use of a non-solid lithium replenishing layer with stripe-like hollow gaps can improve the wettability of the electrode piece to the electrolyte, thereby improving various performance of the battery.
  • Comparative Example 1 which contains only the lithium replenishing layer, and Comparative Example 2, a blank control group containing only a solvent and containing no polymer, were set up.
  • the performance of the batteries produced by both showed a very significant decline.
  • Comparative Example 3 the thickness of the polymer layer is too thin, the protection effect is poor, the lithium replenishment efficiency is low, and the battery performance is poor; in Comparative Example 4, the polymer layer is too thick, and although the lithium replenishment efficiency is high, it also increases the battery cost. impedance, thus resulting in a decrease in cycle performance.

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Abstract

本申请涉及一种负极极片及其制备方法、二次电池、电池模块、电池包及用电装置。其中的负极极片包括负极集流体以及设置于负极集流体至少一个表面之上的负极膜层，负极膜层包括层叠设置的负极活性材料层、补锂层以及聚合物层；其中，负极活性材料层位于负极集流体之上，补锂层位于负极活性材料层背离负极集流体的一侧，聚合物层位于补锂层背离负极活性材料层的一侧。

Description

负极极片及其制备方法、二次电池、电池模块、电池包及用电装置
本申请要求享有2022年05月19日提交的名称为“负极极片及其制备方法、二次电池、电池模块、电池包及用电装置”的中国专利申请CN2022105437419的优先权，其全部内容通过引用并入本文中。
技术领域
本申请涉及二次电池技术领域，特别是涉及负极极片及其制备方法、二次电池、电池模块、电池包及用电装置。
背景技术
由于消费市场对二次电池日渐增长的品质需求，如何有效提升电池的循环寿命和能量密度成为二次电池领域的研究热点。研究发现，在锂离子电池首次充电过程中，有机电解液会在石墨等负极表面还原分解，形成固体电解质相界面膜，永久地消耗大量来自正极的锂，造成首次循环的库仑效率偏低，降低了锂离子电池的容量和能量密度。为了解决这个问题，人们研究了预锂化技术，通过预锂化对电极材料进行补锂，抵消形成SEI膜造成的不可逆锂损耗，能有效提高电池的总容量和能量密度。
预锂化技术可以分为负极补锂和正极补锂。传统技术中，正极补锂由于较负极补锂可操作性更强、安全性更高、对设备无特殊需求而被广泛使用，但正极补锂可能会导致正极的活性物质的比例下降，例如使用Li 5FeO 4时，需要达到7％的含量，而其补锂后的产物是没有活性的，影响了锂离子电池能量密度的进 一步提高。
发明内容
鉴于背景技术中存在的技术问题，有必要提供一种负极极片及其制备方法、二次电池、电池模块、电池包及用电装置，该负极极片可以实现安全补锂，能有效改善传统技术中存在的负极补锂安全性较差、正极补锂对能量密度提升有限的难题。
为了实现上述目的，本申请的第一方面提供了一种负极极片，其包括负极集流体以及设置于所述负极集流体至少一个表面之上的负极膜层，所述负极膜层包括层叠设置的负极活性材料层、补锂层以及聚合物层；
其中，所述负极活性材料层位于所述负极集流体之上，所述补锂层位于所述负极活性材料层背离所述负极集流体的一侧，所述聚合物层位于所述补锂层背离所述负极活性材料层的一侧。
相对于现有技术，本申请至少包括如下所述的有益效果：
本申请的技术方案中，通过在负极活性材料层表面设置补锂层进行补锂，避免了传统技术中通过在负极活性材料颗粒表面进行包覆补锂的复杂工艺和与水系负极制备工艺兼容性差的问题；通过在补锂层表面设置聚合物层，能有效阻隔补锂层与水或氧气发生反应，提高了负极补锂的安全性和补锂效率。
在本申请任意实施方式中，所述聚合物层的材质包括聚甲基丙烯酸甲酯、聚氧化乙烯、聚丙烯腈、聚苯乙烯、全氟聚醚、二甲基硅油以及甲基丙烯酸甲酯-亚硫酸丙烯酯的嵌段共聚物中的一种或多种。
在本申请任意实施方式中，所述聚合物层包括第一聚合物和第二聚合物，所述第一聚合物包括聚甲基丙烯酸甲酯、聚氧化乙烯、聚丙烯腈、聚苯乙烯以 及聚甲基丙烯酸甲酯-亚硫酸丙烯酯的嵌段共聚物中的一种或多种，所述第二聚合物包括全氟聚醚和/或二甲基硅油。
在本申请任意实施方式中，所述第一聚合物和所述第二聚合物的质量比为(1～9):1。
在本申请任意实施方式中，所述负极集流体的两侧表面上均设置有所述负极膜层。
在本申请任意实施方式中，所述负极极片中包括的聚合物层的厚度为1μm～12μm。
在本申请任意实施方式中，所述补锂层的材质包括单质锂。
在本申请任意实施方式中，所述补锂层中包括若干个相互平行的条纹状中空间隙，所述条纹状中空间隙的宽度为0.1μm～100μm，相邻两个所述条纹状中空间隙之间实心部分的宽度为50μm～10mm。
在本申请任意实施方式中，每个所述补锂层的厚度为0.1μm～15μm。
本申请的第二方面提供了一种二次电池，其制作方法包括将电极组件浸于电解液中；
其中，所述电极组件包括前述任一实施方式所述的负极极片、隔离膜以及正极极片，所述隔离膜设置于所述负极极片和所述正极极片之间。
在本申请任意实施方式中，所述聚合物层的质量占所述聚合物层与所述电解液的质量之和的0.1％～4％。
本申请的第三方面提供了一种电池模块，其包括前述一种或多种实施方式所述的二次电池。
本申请的第四方面提供了一种电池包，其包括前述的电池模块。
本申请的第五方面提供了一种用电装置，其包括前述一种或多种实施方式 所述的二次电池、前述的电池模块以及前述的电池包中的一种或多种。
本申请的第六方面提供了前述任一实施方式所述的负极极片的制备方法，其包括以下步骤：
在负极集流体的至少一个表面形成负极活性材料层；
在所述负极活性材料层的表面形成补锂层；
在所述补锂层表面形成聚合物层。
在本申请任意实施方式中，在所述补锂层表面形成所述聚合物层的操作包括以下步骤：
将聚合物溶于有机溶剂制备成聚合物溶液，将所述聚合物溶液施涂在所述补锂层的表面形成聚合物涂层，干燥后制得所述聚合物层。
在本申请任意实施方式中，所述有机溶剂包括碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、1,3-二氧戊烷、碳酸二苯酯、丙烯磺酸内酯、丙烯基-1,3磺内酯、磷酸三苯酯、亚磷酸三苯酯以及环丁砜中的一种或多种。
在本申请任意实施方式中，所述聚合物溶液中，所述聚合物的质量百分含量为1％～15％。
本申请的一个或多个实施例的细节在下面的附图和描述中提出。本申请的其它特征、目的和优点将从说明书、附图以及权利要求书变得明显。
附图说明
为了更清楚地说明本申请的技术方案，下面将对本申请中所使用的附图作简单介绍。显而易见地，下面所描述的附图仅仅是本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是本申请一实施方式的电池模块的示意图。
图4是本申请一实施方式的电池包的示意图。
图5是图4所示的本申请一实施方式的电池包的分解图。
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。
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：盖板。
具体实施方式
下面结合具体实施方式，进一步阐述本申请。应理解，这些具体实施方式仅用于说明本申请而不用于限制本申请的范围。
为了便于理解本申请，下面将参照相关附图对本申请进行更全面的描述。附图中给出了本申请的较佳实施例。但是，本申请可以以许多不同的形式来实现，并不限于本文所描述的实施例。相反地，提供这些实施例的目的是使对本申请的公开内容的理解更加透彻全面。
此外，术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括至少一个该特征。在申请的描述中，“多种”的含义是至少两种，例如两种，三种等，除非另有明确具体的限定。在本申请的描述中，“若干”的含义是至少一个，例如一个，两个等，除非另有明确具体的限定。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术 领域的技术人员通常理解的含义相同。本文中在本申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请。本文所使用的术语“和/或”包括一个或多个相关的所列项目的任意的和所有的组合。
本申请中，以开放式描述的技术特征中，包括所列举特征组成的封闭式技术方案，也包括包含所列举特征的开放式技术方案。
本申请中，涉及到数值区间，如无特别说明，上述数值区间内视为连续，且包括该范围的最小值及最大值，以及这种最小值与最大值之间的每一个值。进一步地，当范围是指整数时，包括该范围的最小值与最大值之间的每一个整数。此外，当提供多个范围描述特征或特性时，可以合并该范围。换言之，除非另有指明，否则本文中所公开之所有范围应理解为包括其中所归入的任何及所有的子范围。
本申请中涉及的百分比含量，如无特别说明，对于固液混合和固相-固相混合均指质量百分比，对于液相-液相混合指体积百分比。
本申请中涉及的百分比浓度，如无特别说明，均指终浓度。所述终浓度，指添加成分在添加该成分后的体系中的占比。
本申请中的温度参数，如无特别限定，既允许为恒温处理，也允许在一定温度区间内进行处理。所述的恒温处理允许温度在仪器控制的精度范围内进行波动。传统技术中，往往通过在负极活性材料表面包覆补锂剂进行补锂，然而，负极补锂剂通常为单质锂，其性质非常活泼，容易与水和空气中的氧气等发生反应，因此无法兼容水系的负极制备工艺，需采用有机溶剂，造成更多的环境污染。为了解决这一问题，人们通过在补锂层的表面再包覆一层聚合物保护层以隔绝水氧，然而，若聚合物保护层可溶于电解液，注液溶解后，活性材料颗粒之间的粘结性会变差，若聚合物保护层不能溶于电解液，则会增加电池的阻 抗，降低电性能。
基于以上背景，本申请的实施例提供了一种负极极片，其包括负极集流体以及设置于负极集流体至少一个表面之上的负极膜层，负极膜层包括层叠设置的负极活性材料层、补锂层以及聚合物层；
其中，负极活性材料层位于负极集流体之上，补锂层位于负极活性材料层背离负极集流体的一侧，聚合物层位于补锂层背离负极活性材料层的一侧。
不希望限于任何理论，本申请的技术方案中，通过在负极活性材料层表面设置补锂层进行补锂，避免了传统技术中通过在负极活性材料颗粒表面进行包覆补锂的复杂工艺和与水系负极制备工艺兼容性差的问题；通过在补锂层表面设置聚合物层，能有效阻隔补锂层与水或氧气发生反应，提高了负极补锂的安全性和补锂效率。
本发明人经深入研究发现，当本申请的负极极片在满足上述设计条件的基础上，若还可选地满足下述条件中的一个或几个时，可以进一步提升负极补锂的安全性和补锂效率。
在一些实施例中，聚合物层的材质包括聚甲基丙烯酸甲酯(PMMA)、聚氧化乙烯(PEO)、聚丙烯腈(PAN)、聚苯乙烯(PS)、全氟聚醚(PEFE)、二甲基硅油(PDMS)以及甲基丙烯酸甲酯-亚硫酸丙烯酯的嵌段共聚物中的一种或多种。通过选用合适种类的聚合物制备聚合物层，当极片与电解液接触时，聚合物层会溶于电解液中，能够避免保护层的存在造成电池阻抗的增加。
在一些实施例中，聚合物层包括第一聚合物和第二聚合物，第一聚合物包括聚甲基丙烯酸甲酯、聚氧化乙烯、聚丙烯腈、聚苯乙烯以及聚甲基丙烯酸甲酯-亚硫酸丙烯酯的嵌段共聚物中的一种或多种，第二聚合物包括全氟聚醚和/或二甲基硅油。第一聚合物溶胀或溶解后，电导率较高，有助于提升电池电性 能；第二聚合物电导率较差，但对水分和气体的阻隔性良好，能有效保护补锂层不受水分和氧气侵蚀。将第一聚合物和第二聚合物复配使用，能兼顾对补锂层的保护和电池的电性能提升。
在一些实施例中，第一聚合物和第二聚合物的质量比为(1～9):1。第一聚合物和第二聚合物的质量比例如还可以是1:1.5、1:2、1:2.5、1:3、1:3.5、1:4、1:4.5、1:5、1:5.5、1:6、1:6.5、1:7、1:7.5、1:8或1:8.5。将两者的质量比控制在合适范围内，能更大程度平衡对补锂层的保护性能以及电池的电性能。
在一些实施例中，负极集流体的两侧表面上均设置有负极膜层。
在一些实施例中，负极极片中包括的聚合物层的厚度为1μm～12μm。聚合物层的厚度例如还可以是1.5μm、2μm、2.5μm、3μm、3.5μm、4μm、4.5μm、5μm、5.5μm、6μm、6.5μm、7μm、7.5μm、8μm、8.5μm、9μm、9.5μm、10μm、10.5μm、11μm或11.5μm。聚合物层的厚度设置在合适范围内，溶于电解液后聚合物在电解液中的浓度适中，即满足了保护效果，也不会因浓度过大而引起电解液粘度过高，不能满足基本使用需求。
此处所述的“聚合物层的厚度”是指整个负极极片中包括的聚合物层的总厚度，若只有一个聚合物层，则该聚合物层厚度为1μm～12μm，若有两个聚合物层，则两个聚合物层的厚度之和为厚度为1μm～12μm。有两个聚合物层时，两个聚合物层的厚度可以相等或不相等。
在一些实施方式中，补锂层的材质包括单质锂。
在一些实施方式中，补锂层中包括若干个相互平行的条纹状中空间隙，条纹状中空间隙的宽度为0.1μm～100μm，相邻两个条纹状中空间隙之间实心部分的宽度为50μm～10mm。条纹状中空间隙的宽度例如可以是10μm、20μm、 30μm、40μm、50μm、60μm、70μm、80μm或90μm；相邻两个条纹状中空间隙之间实心部分的宽度例如可以是100μm、200μm、300μm、400μm、500μm、600μm、700μm、800μm、900μm、1mm、1.5mm、2mm、2.5mm、3mm、3.5mm、4mm、4.5mm、5mm、5.5mm、6mm、6.5mm、7mm、7.5mm、8mm、8.5mm、9mm或9.5mm。包含中空间隙的补锂层结构类似于斑马线，有补锂层的条纹和没有补锂层的中空间隙彼此平行排列，能使得极片对电解液的浸润性更好，从而有利于电池性能的提高。合适的条纹宽度和间隙宽度能兼顾补锂效率和浸润性。
在一些实施方式中，每个补锂层的厚度为0.1μm～15μm。补锂层的厚度例如还可以是1μm、1.5μm、2μm、2.5μm、3μm、3.5μm、4μm、4.5μm、5μm、5.5μm、6μm、6.5μm、7μm、7.5μm、8μm、8.5μm、9μm、9.5μm、10μm、10.5μm、11μm、11.5μm、12μm、12.5μm、13μm、13.5μm、14μm或14.5μm。控制补锂层的厚度在合适范围内，能对电池进行更充分的补锂，同时成本较低。
此处所述的“每个补锂层的厚度”是指单个补锂层的厚度，若极片中不仅存在一个补锂层，则补锂层的总厚度为每个补锂层的厚度的总和。
本申请的实施例还提供了一种二次电池，其制作方法包括将电极组件浸于电解液中；
其中，电极组件包括前述任一实施方式的负极极片、隔离膜以及正极极片，隔离膜设置于负极极片和正极极片之间。
电极组件浸于电解液中后，负极极片中的聚合物层会溶解在电解液中，避免增加电池的阻抗。
在一些实施例中，聚合物层的质量占聚合物层与电解液的质量之和的百分比为0.1％～4％。该占比例如还可以是0.2％、0.35％、0.4％、0.6％、0.8％、1％、 1.2％、1.4％、1.6％、1.8％、2％、2.2％、2.4％、2.6％、2.8％、3％、3.2％、3.4％、3.5％、3.6％或3.8％。聚合物层的质量占比在合适范围内，能够兼顾溶解前对补锂层的保护性能，及溶解后电解液的粘度，避免对电池性能造成不利影响。当聚合物层中存在两种聚合物时，两种聚合物的总质量占比为0.1％～4％。
在一些实施例中，聚合物层中同时存在第一聚合物和第二聚合物，且集流体两侧均设置有负极膜层。此时，将前述实施方式中聚合物层的厚度记作D(μm)，将第一聚合物的质量占聚合物层与电解液的质量之和的百分比记作wt 1(％)，将第一聚合物的质量占聚合物层与电解液的质量之和的百分比记作wt 2(％)，将电解液和聚合物层的总质量记作m(g)，将负极极片的长度记作a(mm)，宽度记作b(mm)，第一聚合物的密度记作ρ 1(g/cm 3)，第二聚合物的密度记作ρ 2(g/cm 3)，上述参数满足以下关系：
Figure PCTCN2022124775-appb-000001
根据上述公式，当wt 1和wt 2的取值范围均为0.1％～2％时，相应地，两个聚合物层的总厚度范围为1μm～12μm。此时，聚合物溶解后对于电解液粘度和电导率无明显负面影响，且溶解前聚合物层对补锂层的保护效果良好。
本申请的实施例还提供了一种电池模块，其包括前述一种或多种实施例的二次电池。
本申请的实施例还提供了一种电池包，其包括前述的电池模块。
本申请的实施例还提供了一种用电装置，其包括前述一种或多种实施例的二次电池、前述的电池模块以及前述的电池包中的一种或多种。
本申请的实施例还提供了前述任一实施例的负极极片的制备方法，其包括以下步骤：
在负极集流体的至少一个表面形成负极活性材料层；
在负极活性材料层的表面形成补锂层；
在补锂层表面形成聚合物层。
在一些实施例中，在补锂层表面形成聚合物层的操作包括以下步骤：
将聚合物溶于有机溶剂制备成聚合物溶液，将聚合物溶液施涂在补锂层的表面形成聚合物涂层，干燥后制得聚合物层。
在一些实施例中，施涂的工艺包括喷涂、涂布、浸润以及微凹版中的一种或多种。优选涂布。
在一些实施例中，有机溶剂包括碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、1,3-二氧戊烷、碳酸二苯酯、丙烯磺酸内酯、丙烯基-1,3磺内酯、磷酸三苯酯、亚磷酸三苯酯以及环丁砜中的一种或多种。优选DEC。
在一些实施例中，聚合物溶液中，聚合物的质量百分含量为1％～15％。聚合物溶液中，聚合物的质量百分含量例如还可以是2％、4％、6％、8％、10％、12％或14％。合适浓度的聚合物溶液能够使得施涂次数尽可能少的同时，施涂更均匀。
另外，以下适当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说明。
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，活性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。
正极极片
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜 层，所述正极膜层包括本申请第一方面的正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(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，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可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，还可以使用其他可被用作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、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。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-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中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、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正极极片：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；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
负极极片
负极极片选自本申请第一方面提供的负极极片。
在一些实施方式中，所述负极集流体可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。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(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，负极活性材料层中的负极活性材料可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，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(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，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，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；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，得到负极活性材料层。
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，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
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，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
隔离膜
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可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，外包装可包括壳体51和盖板53。其中，壳体51可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，本领域技术人员可根据具体实际需求进行选择。
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可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池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。
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、电动车辆、电气列车、船舶及卫星、储能系统等，但不限于此。其中，移动设备例如可以是手机、笔记本电脑等；电动车辆例如可以是纯电动车、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，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6。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。
以下结合具体实施例和对比例对本申请做进一步详细的说明。以下具体实施例中未写明的实验参数，优先参考本申请文件中给出的指引，还可以参考本领域的实验手册或本领域已知的其它实验方法，或者参考厂商推荐的实验条件。可理解，以下实施例所用的仪器和原料较为具体，在其他具体实施例中，可不限于此；本申请说明书实施例中所提到的相关成分的重量不仅仅可以指代各组分的具体含量，也可以表示各组分间重量的比例关系，因此，只要是按照本申请实施例说明书相关组分的含量按比例放大或缩小均在本申请说明书实施例公开的范围之内。具体地，本申请实施例说明书中所述的重量可以是μg、mg、g、kg等化学化工领域公知的质量单位。所用试剂或仪器未注明生产厂商者，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
将正极活性物质磷酸铁锂(克容量为139mAh/g)、导电剂乙炔黑、粘结剂PVDF(聚偏二氟乙烯)按重量比94:4:2进行混合，加入溶剂N-甲基吡咯烷酮，充分搅拌混合均匀得到正极浆料，然后涂覆于正极集流体铝箔的两个表面上，其中，正极浆料的涂布用量为0.224g/1540.25mm 2(以不包含溶剂的重量计)，然后烘干、冷压，得到正极极片。
(2)负极极片的制备
步骤a：将负极活性物质人造石墨(克容量为340mAh/g)、导电剂乙炔黑、粘结剂SBR(丁苯橡胶乳)、粘结剂CMC(羧甲基纤维素钠)按照重量比95:1.5:3.1:0.4进行混合，加入溶剂去离子水，充分搅拌混合均匀得到负极浆料，然后涂覆于负极集流体铜箔的两个表面上，其中，负极浆料的涂布用量为0.136 g/1540.25mm 2(以不包含溶剂的重量计)，烘干、冷压；
步骤b：通过辊压的方式分别将两片10μm厚的锂箔(克容量为3861mAh/g)复合到步骤a所得产品的两个表面，形成两个补锂层，其中锂箔的用量为3.45mg/1540.25mm 2；所得补锂层中具有相互平行的条纹状中空间隙，条纹状中空间隙的宽度为50μm，相邻两个条纹状中空间隙之间实心部分的宽度为200μm。
步骤c：将100g PMMA(聚甲基丙烯酸甲酯)溶解在900g的DMC(碳酸二甲酯)中，获得质量分数为10％的PMMA溶液，将该溶液通过喷涂覆盖在步骤b所得产品的两个表面，25℃下鼓风干燥30min，得到负极极片。
(3)电解液制备
在含水量<10ppm的氩气气氛手套箱中，将EC(碳酸乙烯酯)、PC(聚碳酸酯)、DMC(碳酸二甲酯)按照重量比为EC:PC:DMC＝3:3:3进行混合，然后加入LiPF 6，VC，DTD以及PS，搅拌均匀后，获得电解液，其中LiPF 6的锂离子电池电解液的浓度为1mol/L，VC，DTD，PS的质量百分数分别为3％，1％，1％。
(4)隔离膜的制备
以聚乙烯多孔膜作为隔离膜。
(5)锂离子二次电池的制备
将步骤(1)制得的正极极片、步骤(4)中的隔离膜、步骤(2)制得的负极极片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，得到裸电芯；将裸电芯置于外包装中，注入1mL步骤(3)中配好的电解液并封装进行化成获得锂离子二次电池。
实施例2～18
与实施例1工艺相同(含有两种聚合物的，将两种聚合物一起溶解制得溶 液)，但聚合物层的配比、厚度、使用的溶剂和制备工艺有所区别，详见表1。
实施例19
与实施例1基本一致，区别在于，步骤(2)中制备负极极片时，步骤b制得的补锂层为实心补锂层，没有条纹状中空间隙。
对比例1
与实施例1基本相同，区别在于，步骤(2)中制备负极极片时，步骤c中不含溶质PMMA。
对比例2
与实施例1基本相同，区别在于，步骤(2)中制备负极极片时，不含步骤c。
对比例3～4
与实施例2工艺相同，但聚合物层的配比、厚度有所区别，详见表1。
表1
Figure PCTCN2022124775-appb-000002
Figure PCTCN2022124775-appb-000003
表征测试
将上述各实施例和对比例中制得的锂离子二次电池分别进行以下测试，所得结果见表2。
(1)锂离子二次电池的锂效率测试
将三明治电极冲切成41mm×49.5mm小叠片，表面镀锂的铜箔冲切成43.5mm×51mm。三明治结构锂片、隔离膜、三明治电极、隔离膜、锂片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，得到叠片裸电芯。将裸电芯置于外包装中，注入配好电解液并封装获得锂离子二次电池。然后以三明治结构电极作为正极，锂电极作为负极，进行0.04C(1C即1h内完全放掉理论容量的电流值)充电至2V，检测其充电容量C1(单位为mAh)。
锂离子二次电池的锂效率＝C1/(41×49.5/1540.25×m×2×3.861)×100％，其中，m为补锂总量(mg)
(2)锂离子二次电池的常温循环性能测试
在25℃下，将锂离子二次电池先以1C(即1h内完全放掉理论容量的电流值)恒流充电至电压为3.65V，然后以3.65V恒压充电至电流为0.05C，静置5min之后，将锂离子二次电池以1C恒流放电至电压为2.5V，此为一个充放电循环过程，此次的放电容量为首次循环的放电容量。将锂离子二次电池按上述方法进行多次循环充放电测试，直至锂离子二次电池的放电容量衰减至80％，记录锂离子二次电池的循环次数。
(3)锂离子二次电池的高温循环性能测试
在60℃下，将锂离子二次电池先以1C(即1h内完全放掉理论容量的电流值)恒流充电至电压为3.65V，然后以3.65V恒压充电至电流为0.05C，静置5min之后，将锂离子二次电池以1C恒流放电至电压为2.5V，此为一个充放电循环过程，此次的放电容量为首次循环的放电容量。将锂离子二次电池按上述方法进行多次循环充放电测试，检测得到第500次循环的放电容量。
锂离子二次电池60℃循环500次后的容量保持率＝(第500次循环的放电容量/首次循环的放电容量)×100％。
表2
Figure PCTCN2022124775-appb-000004
从表1和表2可知，本申请各实施例制得的锂离子电池锂效率均维持在72％以上，常温和60℃下的循环性能良好。比较实施例1和实施例3可知，维持聚 合物用量相等时，将两类聚合物复配使用，不仅能取得更好的保护效果，使锂效率更高，且电池的循环性能也更加优秀；比较实施例2～5可知，随着聚合物层厚度的增加，锂效率和循环性能均会先上升后下降，因此，厚度为5μm左右时能较好地平衡补锂层的保护效果和电池电性能两方面的需求。比较实施例3、11～15可知，采用不同种类的溶剂溶解聚合物进行涂覆，最后制得的电池性能略有差异，这可能是因为聚合物层在干燥后还残留部分溶剂，其中，DEC作为溶剂时效果最好。比较实施例3、16～18可知，不同的施涂工艺对电池性能也有不同的影响，其中，以涂布工艺效果最优，喷涂其次。比较实施例3和实施例19可知，采用非实心的、具有条纹状中空间隙的补锂层能够提升极片对电解液的浸润性，从而提升电池的各项性能。
作为对比，设置了仅含补锂层的对比例1，以及不含聚合物、仅喷涂了溶剂的空白对照组对比例2，两者制得的电池各项性能都有非常显著的下降。对比例3中，聚合物层厚度太薄，保护效果不佳，补锂效率低、电池性能差；对比例4中，聚合物层厚度太厚，虽然补锂效率高，但同时也增加了电池的阻抗，因此导致了循环性能的下降。
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。
以上所述实施例仅表达了本申请的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对发明专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请专利的保护范围应以所附权利要求为准，说明书及附图可以用于解释权利要求的内容。

Claims (18)

  1. 一种负极极片，包括负极集流体以及设置于所述负极集流体至少一个表面之上的负极膜层，所述负极膜层包括层叠设置的负极活性材料层、补锂层以及聚合物层；
    其中，所述负极活性材料层位于所述负极集流体之上，所述补锂层位于所述负极活性材料层背离所述负极集流体的一侧，所述聚合物层位于所述补锂层背离所述负极活性材料层的一侧。
  2. 如权利要求1所述的负极极片，其中所述聚合物层的材质包括聚甲基丙烯酸甲酯、聚氧化乙烯、聚丙烯腈、聚苯乙烯、全氟聚醚、二甲基硅油以及甲基丙烯酸甲酯-亚硫酸丙烯酯的嵌段共聚物中的一种或多种。
  3. 如权利要求1至2任一项所述的负极极片，其中所述聚合物层包括第一聚合物和第二聚合物，所述第一聚合物包括聚甲基丙烯酸甲酯、聚氧化乙烯、聚丙烯腈、聚苯乙烯以及聚甲基丙烯酸甲酯-亚硫酸丙烯酯的嵌段共聚物中的一种或多种，所述第二聚合物包括全氟聚醚和/或二甲基硅油。
  4. 如权利要求3所述的负极极片，其中所述第一聚合物和所述第二聚合物的质量比为(1～9):1。
  5. 如权利要求1至4任一项所述的负极极片，其中所述负极集流体的两侧表面上均设置有所述负极膜层。
  6. 如权利要求1至5任一项所述的负极极片，其中所述负极极片中包括的聚合物层的厚度为1μm～12μm。
  7. 如权利要求1至6任一项所述的负极极片，其中所述补锂层的材质包括单质锂。
  8. 如权利要求1至7任一项所述的负极极片，其中所述补锂层中包括若干个 相互平行的条纹状中空间隙，所述条纹状中空间隙的宽度为0.1μm～100μm，相邻两个所述条纹状中空间隙之间实心部分的宽度为50μm～10mm。
  9. 如权利要求1至8任一项所述的负极极片，其中每个所述补锂层的厚度为0.1μm～15μm。
  10. 一种二次电池，其制作方法包括将电极组件浸于电解液中；
    其中，所述电极组件包括权利要求1至9任一项所述的负极极片、隔离膜以及正极极片，所述隔离膜设置于所述负极极片和所述正极极片之间。
  11. 如权利要求10所述的二次电池，其中所述聚合物层的质量占所述聚合物层与所述电解液的质量之和的0.1％～4％。
  12. 一种电池模块，包括权利要求10至11任一项所述的二次电池。
  13. 一种电池包，包括权利要求12所述的电池模块。
  14. 一种用电装置，包括权利要求10至11任一项所述的二次电池、权利要求12所述的电池模块以及权利要求13所述的电池包中的一种或多种。
  15. 一种如权利要求1至9任一项所述的负极极片的制备方法，包括如下步骤：
    在负极集流体的至少一个表面形成负极活性材料层；
    在所述负极活性材料层的表面形成补锂层；
    在所述补锂层表面形成聚合物层。
  16. 如权利要求15所述的制备方法，其中在所述补锂层表面形成所述聚合物层的操作包括以下步骤：
    将聚合物溶于有机溶剂制备成聚合物溶液，将所述聚合物溶液施涂在所述补锂层的表面形成聚合物涂层，干燥后制得所述聚合物层。
  17. 如权利要求15至16任一项所述的制备方法，其中所述有机溶剂包括碳 酸二甲酯、碳酸二乙酯、碳酸甲乙酯、1,3-二氧戊烷、碳酸二苯酯、丙烯磺酸内酯、丙烯基-1,3磺内酯、磷酸三苯酯、亚磷酸三苯酯以及环丁砜中的一种或多种。
  18. 如权利要求15至17任一项所述的制备方法，其中所述聚合物溶液中，所述聚合物的质量百分含量为1％～15％。
PCT/CN2022/124775 2022-05-19 2022-10-12 负极极片及其制备方法、二次电池、电池模块、电池包及用电装置 WO2023221380A1 (zh)

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