WO2025112488A1 - 负极极片及其制备方法、电池和用电设备 - Google Patents

负极极片及其制备方法、电池和用电设备 Download PDF

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Publication number
WO2025112488A1
WO2025112488A1 PCT/CN2024/100868 CN2024100868W WO2025112488A1 WO 2025112488 A1 WO2025112488 A1 WO 2025112488A1 CN 2024100868 W CN2024100868 W CN 2024100868W WO 2025112488 A1 WO2025112488 A1 WO 2025112488A1
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Prior art keywords
negative electrode
active material
material layer
electrode active
lithium
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English (en)
French (fr)
Inventor
冯念云
李晓伟
裴振兴
牛从酥
陈雪芳
杨周飞
姚斌
杨丽美
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • 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
    • H01M4/13—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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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
    • 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
    • H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
    • 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 belongs to the technical field of secondary batteries, and specifically relates to a negative electrode plate and a preparation method thereof, a battery and an electrical device.
  • Secondary batteries are not only used in energy storage power systems such as hydropower, thermal, wind and solar power stations, but are also widely used in electric transportation vehicles such as electric bicycles, electric motorcycles, electric cars, as well as in military equipment, aerospace and other fields.
  • the negative electrode plate of a battery generally includes a current collector and a negative electrode active material layer disposed on the current collector.
  • the existing negative electrode active material layer is easy to fall off, and the cycle performance and fast charging performance of the battery are poor.
  • the present application provides a negative electrode plate, aiming to solve the problem that the negative electrode active material layer is easy to fall off and the cycle performance and fast charging performance of the battery containing it are poor.
  • the negative electrode active material layer has pores, and at least part of the acrylic acid lithium polymer is embedded in the pores. In this way, the contact area between the acrylic acid lithium polymer and the negative electrode active material layer can be increased, and the fast charging ability and cycle life of the battery can be improved without affecting the bonding force between the negative electrode active material layer and the current collector. performance.
  • At least one of the following conditions is met:
  • Z k 1%-60%
  • Z k is the reliable permeability of the acrylic lithium polymer in the negative electrode active material layer
  • the distance between the acrylic lithium polymer and the negative electrode active material layer in the pore away from the surface of the current collector is a mm
  • the thickness of the negative electrode sheet is D mm
  • the permeability a/D ⁇ 100%
  • the permeability corresponding to the permeability distribution number reaching 90% is the reliable permeability.
  • the surface density of the conductive layer is 0.05g/1540.25mm 2 -0.4g/1540.25mm 2. Therefore, the surface density of the conductive layer is within the range of 0.05g/1540.25mm 2 -0.4g/1540.25mm 2 , which can improve the cycle life and fast charging performance of the secondary battery, and the bonding force between the negative electrode active material layer and the current collector is strong and not easy to fall off.
  • the mass fraction of lithium is 3%-8.9%. Therefore, the mass fraction of lithium in the acrylic lithium polymer is within the above range, which can improve the cycle life and fast charging performance of the secondary battery, and the bonding force between the negative electrode active material layer and the current collector is strong and not easy to fall off.
  • the mass fraction of lithium is 5%-7.5%. Therefore, the mass fraction of lithium in the acrylic lithium polymer is within the above range, which can improve the cycle life and fast charging performance of the secondary battery, and the bonding force between the negative electrode active material layer and the current collector is strong and not easy to fall off.
  • the number average molecular weight Mn of the acrylic acid lithium polymer is 100,000-500,000. Therefore, when the number average molecular weight Mn of the acrylic acid lithium polymer is within the above range, the cycle life and fast charging performance of the secondary battery can be improved, and the bonding force between the negative electrode active material layer and the current collector is strong and not easy to fall off.
  • the conductive layer comprises a lithium acrylic acid polymer
  • the bonding force between the negative electrode active material layer and the current collector is negatively correlated with the surface density of the conductive layer.
  • the negative electrode sheet prepared by the above method has a strong bonding force between the negative electrode active material layer and the current collector, and is not easy to The secondary battery containing it has excellent cycle life and fast charging performance.
  • a lithium acrylate polymer is sprayed on the side of the negative electrode active material layer away from the current collector by a spraying method to form a conductive layer, and at least part of the lithium acrylate polymer is embedded in the pores of the negative electrode active material layer.
  • the spray pressure is 0.1 kPa-100 kPa.
  • the negative electrode active material layer has a strong bonding force with the current collector and is not easy to fall off, and the secondary battery containing it has excellent cycle life and fast charging performance.
  • the spraying temperature is 70° C.-150° C.
  • the negative electrode active material layer has a strong bonding force with the current collector and is not easy to fall off, and the secondary battery containing the negative electrode active material layer has excellent cycle life and fast charging performance.
  • a current collector containing a negative electrode active material layer is immersed in a lithium acrylate polymer solution to form a conductive layer on the negative electrode active material layer away from the current collector, and at least part of the lithium acrylate polymer is embedded in the pores of the negative electrode active material layer.
  • the negative electrode active material layer has a strong bonding force with the current collector and is not easy to fall off, and the secondary battery containing it has excellent cycle life and fast charging performance.
  • the mass proportion of the lithium acrylate polymer is 0.5%-50%.
  • the mass of the lithium acrylate polymer accounts for 10%-20%.
  • the negative electrode active material layer has a strong bonding force with the current collector and is not easy to fall off, and the secondary battery containing it has excellent cycle life and fast charging performance.
  • a fourth aspect of the present application provides an electrical device, which includes the battery described in the third aspect.
  • FIG1 is a schematic structural diagram of a battery cell according to an embodiment of the present application.
  • FIG3 is a schematic structural diagram of a battery pack according to an embodiment of the present application.
  • FIG4 is an exploded view of FIG3 ;
  • FIG5 is a schematic diagram of an embodiment of an electric device using a battery as a power source
  • FIG. 6 is a scanning electron microscope image of the negative electrode active material layer of Example 1 of the present application.
  • any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and any upper limit can be combined with any other upper limit to form an unspecified range.
  • each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.
  • Secondary batteries have a small size and weight, making them easy to carry and use; they have a high specific energy and can provide a larger amount of energy storage.
  • Lithium-ion batteries have no memory effect and do not need to be fully discharged and recharged, so secondary batteries have broad application prospects.
  • acrylic acid lithium polymers are added to the negative electrode, the Lewis acid small molecules in the electrolyte and the negatively charged carboxyl groups in the added acrylic acid lithium polymers are complexed with each other, which can further increase the electronegativity of the carboxyl groups, making it easier for lithium ions to dissociate and improve the fast charging performance of the battery.
  • acrylic acid lithium polymers are directly mixed with negative electrode active materials and applied to battery poles, the The compound is a linear binder, which weakens the binding force between the negative electrode active material particles and the current collector, resulting in a decrease in the binding force between the negative electrode active material layer and the current collector, and the negative electrode active material layer is easy to fall off.
  • the acrylic lithium polymer is arranged on the side of the negative electrode active material layer away from the current collector, which can improve the liquid absorption capacity and lithium ion conductivity of the negative electrode plate, reduce the concentration polarization of the negative electrode when lithium ions are charged and discharged at the negative electrode, and improve the fast charging capability and cycle performance of the battery; at the same time, the contact probability of the acrylic lithium polymer with the current collector is low, which can reduce the influence of the acrylic lithium polymer on the bonding force between the negative electrode active material layer and the current collector, making the negative electrode active material layer not easy to fall off.
  • the negative electrode plate disclosed in the embodiment of the present application is suitable for a secondary battery, and the battery disclosed in the embodiment of the present application can be used in electrical equipment using the battery as a power source or various energy storage systems using the battery as an energy storage element.
  • Electrical equipment may include, but is not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, and the like.
  • electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like
  • spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like.
  • the present application provides a negative electrode sheet, comprising a current collector, a negative electrode active material layer and a conductive layer, wherein the negative electrode active material layer is disposed on at least one side of the current collector; the conductive layer is disposed on a side of the negative electrode active material layer away from the current collector, and the conductive layer comprises a lithium acrylic polymer;
  • the bonding force between the negative electrode active material layer and the current collector is negatively correlated with the surface density of the conductive layer.
  • lithium acrylate polymer refers to substituted or unsubstituted lithium polyacrylate
  • lithium polyacrylate means that at least one hydrogen atom in polyacrylic acid is replaced by a lithium atom.
  • the negative electrode plate proposed in the present application has a strong bonding force between the negative electrode active material layer and the current collector, and the battery containing the negative electrode plate has excellent cycle performance and fast charging performance.
  • the influence of the acrylic lithium polymer on the bonding force between the negative electrode active material layer and the current collector can be reduced, so that the negative electrode active material layer is not easy to fall off.
  • the bonding force between the negative electrode active material layer and the current collector is strong, and the battery containing the negative electrode sheet has excellent cycle performance and fast charging performance.
  • the "area density of the conductive layer” refers to the mass of the conductive layer per unit area of the current collector, which is a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be obtained by the following method:
  • Step 1 Punch the current collector containing the negative electrode active material layer into small discs with an area of 1540.25 mm2 and weigh them.
  • the mass is g1;
  • the negative electrode active material layer has pores, and at least part of the acrylic acid lithium polymer is embedded in the pores. In this way, the contact area between the acrylic acid lithium polymer and the negative electrode active material can be increased, the acrylic acid lithium polymer is in full contact with the negative electrode active material, and the fast charging capability and cycle performance of the battery are improved without affecting the bonding force between the negative electrode active material layer and the current collector.
  • the pores on the negative electrode active material layer refer to the gaps between the negative electrode active materials.
  • the pores on the negative electrode active material layer can be seen on a scanning electron microscope image.
  • the number of pores on the negative electrode active material layer can be expressed by porosity, which is described in detail below.
  • the physical meaning of permeability is the degree of penetration of the lithium acrylate polymer in the negative electrode active material layer. "The distance between the lithium acrylate polymer in the pore and the surface of the negative electrode active material layer away from the current collector” refers to the vertical distance between the lithium acrylate polymer and the surface of the negative electrode active material layer away from the current collector in the pore. On the surface of the negative electrode active material layer away from the current collector, the permeability is 0. When the lithium acrylate polymer is embedded in the interface between the current collector and the negative electrode active material layer, the permeability is 100%; that is, each position where the lithium acrylate polymer exists in the pore has a corresponding permeability value.
  • the main functional group -COO of lithium polyacrylate was identified in the thickness direction of the electrode.
  • the characteristic peak was 1460cm - 1-1300cm -1 .
  • the corresponding thickness/total thickness of the electrode was the permeability.
  • the permeability distribution number reached 90%, the corresponding permeability was the reliable permeability.
  • the thickness D of the negative electrode sheet can be measured by the following method:
  • Use a micrometer to measure the thickness Use the micrometer to take 10 points in the horizontal and vertical directions of the pole piece, and take the average value as the pole piece thickness.
  • the binding force between the negative electrode active material layer and the current collector is well known in the art and can be measured using instruments and methods well known in the art. For example, it can be obtained by the following method:
  • the bonding force between the negative electrode active material layer and the current collector is negatively correlated with Z k , which means that the larger the Z k , the smaller the bonding force between the negative electrode active material layer and the current collector. Therefore, by controlling Z k , the influence of the acrylic acid lithium polymer on the bonding force between the negative electrode active material layer and the current collector can be reduced, so that the negative electrode active material layer is not easy to fall off.
  • the bonding force between the negative electrode active material layer and the current collector is strong, and the battery containing the negative electrode sheet has excellent cycle performance and fast charging performance.
  • the bonding force between the negative electrode active material layer and the current collector is negatively correlated with the thickness of the negative electrode plate.
  • the effect of the acrylic acid lithium polymer on the bonding force between the negative electrode active material layer and the current collector can be reduced by controlling the thickness of the negative electrode plate, so that the negative electrode active material layer is not easy to fall off.
  • the bonding force between the negative electrode active material layer and the current collector is strong, and the battery containing the negative electrode plate has excellent cycle performance and fast charging performance.
  • the thickness of the negative electrode sheet at least includes the sum of the thickness of the current collector, the thickness of the negative electrode active material layer and the thickness of the conductive layer.
  • the thickness of the negative electrode sheet is well known in the art and can be measured by instruments and methods well known in the art. For example, it can be obtained by the following method: using a micrometer to measure the thickness of the electrode sheet.
  • the bonding force between the negative electrode active material layer and the current collector is positively correlated with the tortuosity of the negative electrode active material layer.
  • the bonding force between the negative electrode active material layer and the current collector is positively correlated with the tortuosity of the negative electrode active material layer, which means that the greater the tortuosity of the negative electrode active material layer, the greater the bonding force between the negative electrode active material layer and the current collector. Therefore, by controlling the tortuosity of the negative electrode active material layer, the influence of the acrylic acid lithium polymer on the bonding force between the negative electrode active material layer and the current collector can be reduced, so that the negative electrode active material layer is not easy to fall off.
  • the bonding force between the negative electrode active material layer and the current collector is strong, and the battery containing the negative electrode sheet has excellent cycle performance and fast charging performance.
  • Tortuosity is the degree of tortuosity.
  • the flow of electrolyte in the negative electrode active material layer does not move forward in a straight line, but flows forward in a circuitous manner.
  • Tortuosity is equal to the ratio of the actual length of the electrolyte in the pore to the apparent length (macroscopic distance, i.e. the thickness of the negative electrode active material layer) passing through the negative electrode active material layer, that is, the actual length of the trajectory of the electrolyte particle in the pore when it passes through a unit distance of the negative electrode active material layer.
  • the tortuosity of the negative electrode active material layer is well known in the art and can be measured using instruments and methods well known in the art. For example, it can be obtained by the following method:
  • the thickness of the electrode is L, the porosity is ⁇ , and the area is A; the conductivity of the electrolyte is ⁇ ;
  • the thickness L of the pole piece is measured using a micrometer. Take 10 points in the horizontal and vertical directions of the pole piece and take the average value. The value is taken as the pole piece thickness;
  • the conductivity ⁇ of the electrolyte can be measured using instruments and methods known in the art.
  • the industry standard HG/T4067-2015 "Lithium Hexafluorophosphate Electrolyte" can be referred to
  • the measurement temperature of the density meter can be set to 20°C
  • the sample can be injected into the measurement cell of the instrument, the measurement can be performed, and the data can be read.
  • the bonding force between the negative electrode active material layer and the current collector is negatively correlated with the porosity of the negative electrode active material layer.
  • the influence of the acrylic acid lithium polymer on the bonding force between the negative electrode active material layer and the current collector can be reduced by controlling the porosity of the negative electrode active material layer, so that the negative electrode active material layer is not easy to fall off.
  • the bonding force between the negative electrode active material layer and the current collector is strong, and the battery containing the negative electrode sheet has excellent cycle performance and fast charging performance.
  • the porosity of the negative electrode active material layer refers to the percentage of the pore volume in the negative electrode active material layer to the total volume of the negative electrode active material layer.
  • the porosity of the negative electrode active material layer is well known in the art and can be measured using instruments and methods well known in the art. For example, it can be obtained by the following method:
  • a/D ⁇ 100% 20%-50%, for example, a/D ⁇ 100% can be 20%-49%, 22%-47%, 25%-45%, 28%-41%, 30%-40%, 32%-38%, 34%-35%, etc.
  • the acrylic acid lithium polymer can be reduced from entering the interface between the negative electrode active material layer and the current collector, the bonding force between the negative electrode active material layer and the current collector is strong, and the battery containing the negative electrode sheet has excellent cycle performance and fast charging performance.
  • a/D ⁇ 100% 25%-40%.
  • the surface density of the conductive layer is 0.05 g/1540.25 mm 2 -0.4 g/1540.25 mm 2 .
  • the surface density Q of the conductive layer can be 0.05g/ 1540.25mm2-0.35g /1540.25mm2 , 0.1g/ 1540.25mm2-0.3g /1540.25mm2, 0.15g /1540.25mm2-0.25g/ 1540.25mm2 , 0.15g/ 1540.25mm2-0.2g /1540.25mm2, etc.
  • the porosity of the negative electrode active material layer is 20%-40%.
  • the porosity ⁇ of the negative electrode active material layer can be 20%-39%, 22%-37%, 25%-35%, 27%-34%, 30%-32%, etc.
  • the porosity of the negative electrode active material layer is within the above range, the bonding force between the negative electrode active material layer and the current collector is strong, and the battery containing the negative electrode sheet has excellent cycle performance and fast charging performance.
  • the porosity of the negative electrode active material layer is 25%-35%.
  • the tortuosity of the negative electrode active material layer is 0.5-7.
  • the tortuosity ⁇ of the negative electrode active material layer can be 0.5-6.9, 1-6.5, 1.5-6, 2-5.5, 2.5-5, 3-4.5, 3.5-4, etc.
  • the tortuosity of the negative electrode active material layer is within the above range, which can reduce the entry of acrylic acid lithium polymer into the interface between the negative electrode active material layer and the current collector, and the bonding force between the negative electrode active material layer and the current collector is strong, and the battery containing the negative electrode sheet has excellent cycle performance and fast charging performance.
  • ⁇ 2-4.
  • the bonding force between the negative electrode active material layer and the current collector is 5N/m-20N/m.
  • the bonding force F between the negative electrode active material layer and the current collector may be 5N/m-19N/m. 7N/m-18N/m, 10N/m-15N/m, 12N/m-14N/m, etc., the bonding force between the negative electrode active material layer and the current collector is in the range of 5N/m-20N/m, the bonding force between the negative electrode active material layer and the current collector is strong, and the battery containing the negative electrode sheet has excellent cycle performance and fast charging performance.
  • F 7N/m-15N/m.
  • the lithium acrylate polymer includes at least one of lithium polyacrylate, lithium polymethacrylate, lithium polyethylacrylate or lithium polypropylacrylate.
  • the conductive layer includes the lithium acrylate polymer, which can improve the liquid absorption capacity of the negative electrode plate and the lithium ion conductivity, and can improve the fast charging capacity and cycle performance of the battery, and the bonding force between the negative electrode active material layer and the current collector is strong.
  • the mass fraction of lithium is 3%-8.9%.
  • the mass fraction of lithium can be 3%-8.9%, 3.5%-8.5%, 4%-7%, 4%-6%, etc.
  • the mass fraction of lithium the mass of lithium/the mass of the acrylic lithium polymer. The mass fraction of lithium is within the above range.
  • a portion of the acrylic lithium polymer penetrates into the pores of the negative electrode active material layer, which can improve the liquid absorption capacity of the negative electrode plate, and significantly improve the conductivity of lithium ions, which can improve the electronic conductivity of the negative electrode plate, reduce the internal resistance, and increase the diffusion coefficient of lithium ions in the electrode material, thereby improving the fast charging capacity and cycle performance of the battery, and the bonding force between the negative electrode active material layer and the current collector is strong.
  • the mass fraction of lithium is 5%-7.5%.
  • the mass fraction of lithium based on the total mass of the lithium acrylate polymer can be determined by the following method:
  • the sample to be tested is prepared by the following method: weigh 0.2g sample in a beaker, add 10mL concentrated HNO3 solution, place it on a 180°C heating plate for digestion for 30min, after the sample is digested for 30min, cool to room temperature, transfer the digestion solution to a 50mL volumetric flask through a funnel to make up the volume, and test it according to the industry standard USEPA-6010D-2018, prepare a standard test solution, the standard test solution is the ICP analysis multi-element standard solution of the National Nonferrous Metals Testing Center, and the curve concentration points are 0, 0.2, 0.5, 1.0, and 2.0mg/L respectively. Prepare the standard solution calibration curve through the instrument, input the sample mass and volume, and then test the digested solution. The solution beyond the curve range needs to be diluted before testing. Finally, the element content is determined based on the intensity of the spectral lines (quantitative analysis).
  • the number average molecular weight Mn of the acrylic acid lithium polymer is 3,000-1,000,000.
  • the number average molecular weight Mn of the acrylic acid lithium polymer can be 3,000-990,000, 5,000-950,000, 10,000-900,000, 50,000-800,000, 100,000-700,000, 200,000-600,000, 300,000-500,000, 400,000-500,000, etc.
  • the number average molecular weight Mn range of the above-mentioned acrylic acid lithium polymer it is sufficient to improve the liquid absorption capacity of the negative electrode sheet and the lithium ion conductivity, which can improve the fast charging capacity and cycle performance of the battery, and has little effect on the bonding force between the negative electrode active material layer and the current collector, thereby reducing The probability of the negative electrode active material layer falling off from the current collector is low.
  • the number average molecular weight Mn of the lithium acrylic acid polymer is 100,000-500,000.
  • the "number average molecular weight Mn of the lithium acrylate polymer” has a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be obtained by the following method:
  • test steps Use ultra-high performance polymer chromatograph: ACQUITY APC; detector: ACQUITY differential refractive index detector.
  • the test steps are as follows: (1) Preheating: Install the chromatographic column and pipeline, turn on the console in turn, test the power supply, etc., and open the test software Empower; (2) Parameter setting, injection volume: 0 ⁇ L to 50 ⁇ L (depending on the sample concentration); pump flow rate: 0.2mL/min; mobile phase: 30mol/L LiBr in NMP solution; seal cleaning liquid: isopropanol; pre-column: PLgel10umMiniMIX-BGuard (size: 50mm ⁇ 4.6mm ⁇ 2); analytical phase: PLgel10umMiniMIX-B (size: 250mm ⁇ 4.6mm); standard: polystyrene sleeve; running time: 30min; detector: ACQUITY differential refractive index (RI) detector; column oven temperature: 90°C; detector temperature: 55°C.
  • RI differential refractive index
  • Sample testing a. Standard sample and test sample preparation: Weigh 0.002g to 0.004g of standard sample/test sample respectively and add 2mL of mobile phase liquid to prepare a 0.1% to 0.5% mixed standard, and store in the refrigerator for >8h; b. Standard solution/sample testing: Edit the sample group to be tested, select the established sample group method, and after the baseline is stable, click the run queue to start testing the sample; (4) Data processing: Based on the relationship between retention time and molecular weight, use the chemical workstation to establish a calibration curve, integrate and quantify the sample spectrum, and the chemical workstation automatically generates the molecular weight and molecular weight distribution results.
  • the current collector may be a metal foil or a composite current collector.
  • a metal foil a copper foil may 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 substrate.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode active material layer includes a negative electrode active material
  • the negative electrode active material can be a negative electrode active material for a battery known in the art.
  • the negative electrode 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, etc.
  • 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 negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode active material includes at least one of a single substance of lithium or a lithium alloy.
  • the lithium alloy includes at least one of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, platinum, boron, carbon, and silicon.
  • Lithium alloy refers to an alloy formed by lithium and other metals and/or non-metals, and the other metals and/or non-metals include at least one of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, platinum, boron, carbon, and silicon.
  • the low operating voltage and high specific capacity of lithium are used to greatly improve the energy density of the battery.
  • the negative electrode active material layer may further optionally include a binder.
  • the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode active material layer may further include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • a conductive agent which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener eg, sodium carboxymethyl cellulose (CMC-Na)
  • the second aspect of the present application provides a method for preparing a negative electrode sheet, comprising:
  • the bonding force between the negative electrode active material layer and the current collector is negatively correlated with the surface density of the conductive layer
  • the acrylic acid lithium polymer is arranged on the side of the negative electrode active material layer away from the current collector.
  • the small molecules of the electrolyte can be complexed with the carboxylate in the acrylic acid lithium polymer, which can improve the liquid absorption capacity and lithium ion conductivity of the negative electrode sheet, and reduce the concentration polarization of the negative electrode when the negative electrode is charged and discharged with lithium ions, which can improve the fast charging capacity and cycle performance of the battery;
  • the contact probability between the acrylic acid lithium polymer and the current collector is low, which can reduce the influence of the acrylic acid lithium polymer on the bonding force between the negative electrode active material layer and the current collector, so that the negative electrode active material layer is not easy to fall off.
  • the bonding force between the negative electrode active material layer and the current collector is strong and not easy to fall off, and the secondary battery containing it has excellent cycle life and fast charging performance.
  • the negative electrode active material layer can be prepared in the following manner: the above-mentioned components for preparing the negative electrode plate, such as the negative electrode active material, the conductive agent, the binder and any other 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 collector, and after drying, cold pressing and other processes, the negative electrode active material layer can be obtained.
  • a solvent such as deionized water
  • a lithium acrylate polymer is sprayed on the side of the negative electrode active material layer away from the current collector by a spraying method to form a conductive layer, and at least part of the lithium acrylate polymer is embedded in the pores of the negative electrode active material layer.
  • the negative electrode active material layer has a strong bonding force with the current collector and is not easy to fall off, and the lithium acrylate polymer can fully contact the negative electrode active material, and the secondary battery containing it has excellent cycle life and fast charging performance. different.
  • the spray method is to spray the slurry containing the lithium acrylate polymer to the side of the negative electrode active material layer away from the current collector, and the slurry containing the lithium acrylate polymer forms mist-like small droplets, which are attached to the side of the negative electrode active material layer away from the current collector and enter the pores. After drying, a conductive layer is formed.
  • the conductive layer prepared by this method has good uniformity and is not easy to fall off from the negative electrode active material layer.
  • a spray box is used, and the liquid inside the spray box is a slurry of a lithium acrylic polymer.
  • the current collector containing the negative electrode active material layer passes through the spray box and is dried to complete the preparation of the conductive layer.
  • the spray pressure is 0.1kPa-100kPa
  • the spray pressure is the atomization pressure inside the spray box.
  • the spray pressure can be 0.1kPa-99kPa, 0.5kPa-98kPa, 1kPa-95kPa, 10kPa-90kPa, 20kPa-80kPa, 30kPa-70kPa, 40kPa-60kPa, 50kPa-60kPa, etc.
  • a uniform conductive layer can be formed, and the conductive layer is not easy to fall off from the negative electrode active material layer, and the bonding force between the negative electrode active material layer and the current collector is strong and not easy to fall off, and the acrylic lithium polymer can fully contact the negative electrode active material, and the secondary battery containing it has excellent cycle life and fast charging performance.
  • the spray temperature is 70°C-150°C.
  • the spray temperature is the temperature inside the atomization box.
  • the spray temperature can be 70°C-149°C, 80°C-140°C, 90°C-130°C, 100°C-120°C, etc.
  • a uniform conductive layer can be formed, the conductive layer is not easy to fall off from the negative electrode active material layer, the negative electrode active material layer and the current collector have strong bonding force and are not easy to fall off, and the acrylic acid lithium polymer can fully contact the negative electrode active material, and the secondary battery containing it has excellent cycle life and fast charging performance.
  • the speed of the current collector containing the negative electrode active material layer is 0.1m/s-10m/s.
  • the speed of the current collector containing the negative electrode active material layer can be 0.1m/s-9.9m/s, 0.5m/s-9.5m/s, 1m/s-9m/s, 2m/s-8m/s, 3m/s-7m/s, 4m/s-6m/s, etc., and a uniform conductive layer can be formed, and the conductive layer is not easy to fall off from the negative electrode active material layer.
  • the speed of the current collector containing the negative electrode active material layer is 2m/s-5m/s.
  • a current collector containing a negative electrode active material layer is immersed in a lithium acrylate polymer solution to form a conductive layer on the negative electrode active material layer away from the current collector, and at least part of the lithium acrylate polymer is embedded in the pores of the negative electrode active material layer.
  • the conductive layer prepared by this method has good uniformity and is not easy to fall off from the negative electrode active material layer.
  • the negative electrode active material layer and the current collector have strong bonding force and are not easy to fall off.
  • the lithium acrylate polymer can fully contact the negative electrode active material, and the secondary battery containing it has excellent cycle life and fast charging performance.
  • the temperature of the slurry of the lithium acrylate polymer is 50°C-80°C.
  • the temperature of the slurry of the lithium acrylate polymer can be 50°C-79°C, 55°C-75°C, 60°C-70°C, etc.
  • the current collector containing the negative electrode active material layer is moved at a speed of 1 m/min-50 m/min.
  • the current collector containing the negative electrode active material layer passes through the soaking solution containing the lithium acrylic polymer at a speed of 1m/min-49m/min, 5m/min-45m/min, 10m/min-40m/min, 20m/min-30m/min, etc., so that a uniform conductive layer can be formed, and the conductive layer is not easy to fall off from the negative electrode active material layer.
  • the current collector containing the negative electrode active material layer passes through the soaking solution containing the lithium acrylic polymer at a speed of 8m/min-15m/min.
  • the mass proportion of the lithium acrylate polymer is 0.5%-50%.
  • the mass proportion of the lithium acrylate polymer can be 0.5%-49%, 1%-45%, 5%-40%, 10%-30%, 15%-25%, etc.
  • the bonding force between the negative electrode active material layer and the current collector is strong and not easy to fall off, and the lithium acrylate polymer can be in full contact with the negative electrode active material, and the secondary battery containing it has excellent cycle life and fast charging performance.
  • the mass proportion of the lithium acrylate polymer is 10%-20%.
  • the conductive layer may be prepared by a dry process. Specifically, the lithium acrylate polymer powder is mixed with a conductive agent and the like, and then directly pressed onto the current collector by a dry process in a dry state.
  • the third aspect of the present application provides a battery, which includes the negative electrode sheet described in the first aspect of the present application or the negative electrode sheet prepared by the method described in the second aspect.
  • the bonding force between the negative electrode active material layer and the current collector is strong and not easy to fall off, and the battery has excellent cycle life and fast charging performance.
  • a battery is a battery that can be used again by recharging the active materials after discharge.
  • the battery proposed in this application is a lithium-ion battery.
  • a battery cell includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte.
  • active metal ions lithium ions
  • the separator is set between the positive electrode sheet and the negative electrode sheet to play a role of isolation.
  • the electrolyte plays a role of conducting active metal ions between the positive electrode sheet and the negative electrode sheet.
  • the positive electrode plate includes a positive current collector
  • the positive current collector may be a metal foil, a foam metal or a composite current collector.
  • a metal foil aluminum or stainless steel, stainless steel, copper, aluminum, carbon electrode, carbon, nickel or titanium, etc., which are treated with silver surface, may be used.
  • the composite current collector may include a polymer material base and a metal layer.
  • the foam metal may be a nickel foam, a copper foam, an aluminum foam, an alloy foam, etc.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).
  • a metal material aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.
  • a polymer material substrate such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.
  • the positive electrode plate may further include a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode active material.
  • the specific type of the positive electrode active material is not limited, and active materials known in the art that can be used for battery positive electrodes can be used. Those skilled in the art can select according to actual needs.
  • the positive electrode active material may include, but is not limited to, at least one of lithium transition metal oxides, lithium-containing phosphates of olivine structure and their respective modified compounds.
  • lithium transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and their modified compounds.
  • lithium-containing phosphates of olivine structure may include, but are not limited to, at least one of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon and their modified compounds. These materials can all be obtained commercially.
  • the battery will be accompanied by Li deintercalation and consumption during the charging and discharging process, and the amount of Li in the battery is different when it is discharged to different states.
  • the amount of Li in the material is the initial state of the material, that is, the state before feeding.
  • the positive electrode material is used in the battery system, and after the charge and discharge cycle, the amount of Li in the material will change.
  • the molar content of O is only a theoretical value.
  • the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.
  • the modified compounds of the above materials may be doping-modified and/or surface-coated modified materials.
  • the positive electrode active material layer may also optionally include a binder, a conductive agent and other optional auxiliary agents.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene and carbon nanofibers.
  • the adhesive may include at least one of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB).
  • SBR styrene-butadiene rubber
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • EVA ethylene-vinyl acetate copolymer
  • PAA polyacrylic acid
  • CMC carboxymethyl cellulose
  • PVA polyvinyl alcohol
  • PVB polyvinyl butyral
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.
  • the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.
  • the solvent can be selected from at least one of 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, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • additives such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the present application has no special restrictions and any known porous structure isolation membrane with electrochemical stability and mechanical stability can be selected according to actual needs.
  • it can include a single-layer or multi-layer film containing at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • FIG1 is a battery cell 5 of a square structure as an example.
  • the battery cell 5 may include an outer packaging, which is used to package the positive electrode sheet, the negative electrode sheet and the electrolyte.
  • the outer packaging may include a shell and a cover plate.
  • the shell may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell has an opening connected to the receiving cavity, and the cover plate can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the separator can be wound or laminated to form an electrode assembly.
  • the electrode assembly is packaged in the receiving cavity.
  • the number of electrode assemblies contained in the battery cell can include one or more, which can be adjusted according to demand.
  • the outer packaging of the battery cell may include a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.
  • the outer packaging of the battery cell 5 may also include a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).
  • battery cells may be assembled into a battery module.
  • the battery module may contain multiple batteries, and the specific number may be adjusted according to the application and capacity of the battery module.
  • FIG2 is a battery module 4 as an example.
  • a plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.
  • the battery module 4 may also include a housing having a storage space, in which a plurality of battery cells 5 are stored.
  • the battery modules may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted 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 modules 4.
  • the plurality of battery modules 4 can be arranged in any manner. Arranged in the battery box.
  • the fourth aspect of the present application provides an electrical device, which includes the battery described in the third aspect.
  • the battery can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device.
  • the electrical device may include, but is not limited to, mobile devices (such as mobile phones, laptops), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships and satellites, and energy storage systems.
  • Fig. 5 is an example of an electric device, which includes a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • the electric device may include a mobile phone, a tablet computer, and a notebook computer.
  • the electric device is usually required to be thin and light, and a battery may be used as a power source.
  • the positive electrode active material lithium iron phosphate (LFP), the conductive agent acetylene black, and the binder polyvinylidene fluoride are mixed in a mass ratio of 98:1:1, and the solvent N-methylpyrrolidone is added and stirred until the system becomes uniform to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on both sides of the positive electrode current collector aluminum foil, dried at room temperature, transferred to an oven for further drying, and then cut into 40mm ⁇ 50mm rectangles as positive electrode sheets, and the positive electrode surface capacity is 3.5mAh/ cm2 .
  • the negative electrode slurry is uniformly coated on the current collector by a coating machine and dried to obtain a current collector containing a negative electrode active material layer.
  • lithium polyacrylate slurry lithium polyacrylate is dispersed in deionized water to prepare a dispersion.
  • the dried electrode sheets are rolled into coils and rolled normally to obtain negative electrode sheets.
  • a polyethylene porous membrane was selected as the isolation membrane.
  • the electrolyte was prepared by dissolving 1 M LiPF6 in a solution in which vinylene carbonate was added to a solvent in which ethylene carbonate, diethyl carbonate, and dimethyl carbonate were mixed in a volume ratio of 1:1:2.
  • the positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then they are wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried secondary battery. After vacuum packaging, standing, formation, and shaping processes, a secondary battery is obtained.
  • Example 2-51 and Comparative Example 1-2 are the same as Example 1 except for the different parameters (see Table 1).
  • Example 20 except that the ratio of the negative electrode slurry is different from that in Example 1, the rest is the same as Example 1.
  • the negative electrode slurry of Example 20 contains 98wt.%t of negative electrode active material graphite, 1wt.% of styrene butadiene rubber (SBR) binder, and 1wt.% of SP conductive carbon black.
  • the negative electrode slurry contains 95.5wt.% of negative electrode active material graphite, 3.5wt.% of styrene butadiene rubber (SBR) binder, and 1wt.% of SP conductive carbon black.
  • Comparative Example 2 is the same as Example 1 except that [Preparation of Negative Electrode Sheet] is different from Example 1, and the rest is the same as Example 1, and [Preparation of Negative Electrode Sheet] is replaced by: 95%wt of negative electrode active material graphite, 2.5%wt of styrene butadiene rubber (SBR) binder, 1%wt of SP conductive carbon, and lithium polyacrylate are evenly dispersed in a deionized water solvent to prepare a negative electrode slurry. The negative electrode slurry is evenly coated on the current collector by a coater and dried to obtain a negative electrode sheet.
  • SBR styrene butadiene rubber
  • the main functional group -COO of lithium polyacrylate was identified in the thickness direction of the electrode, with a characteristic peak of 1460 -1 -1300 cm -1 .
  • the corresponding thickness/thickness of the negative electrode is the permeability.
  • the permeability distribution number reaches 90%, the corresponding permeability is the reliable permeability.
  • Use a micrometer to measure the thickness Use the micrometer to take 10 points in the horizontal and vertical directions of the pole piece, and take the average value as the pole piece thickness.
  • Step 1 Punch the current collector containing the negative electrode active material layer into small discs with an area of 1540.25 mm2 and weigh them, with a mass of g1;
  • Step 2 After the conductive layer is coated on both sides, the electrode is punched into small discs with an area of 1540.25 mm2 and weighed, with a mass of g2;
  • the thickness of the electrode is L, the porosity is ⁇ , and the area is A; the conductivity of the electrolyte is ⁇ ;
  • the thickness L of the pole piece is measured using a micrometer. 10 points are taken in the horizontal and vertical directions of the pole piece, and the average value is taken as the thickness of the pole piece.
  • the porosity ⁇ can be obtained by referring to the national standard GB/T24586-2009 "Determination of apparent density, true density and porosity of iron ore".
  • Specific test method immerse the electrode in ethyl methyl carbonate (EMC) for cleaning; based on the gas displacement method, place the negative electrode in a true density tester, a closed test system, and introduce helium according to the procedure, and detect the pressure of the gas in the sample chamber and the expansion chamber.
  • EMC ethyl methyl carbonate
  • the percentage of the pore volume in the electrode to the total volume of the electrode is the electrode porosity
  • the conductivity ⁇ of the electrolyte can be measured using instruments and methods known in the art.
  • the industry standard HG/T4067-2015 "Lithium Hexafluorophosphate Electrolyte" can be referred to, the density meter is set to a temperature of 20°C, and the sample is injected into The measuring cell of the instrument performs the measurement and reads the data.
  • the sample to be tested is prepared by the following method: weigh 0.2g sample in a beaker, add 10mL concentrated HNO3 solution, place it on a 180°C heating plate for digestion for 30min, after the sample is digested for 30min, cool it to room temperature, transfer the digestion solution to a 50mL volumetric flask through a funnel to make up the volume, and test it according to the industry standard USEPA-6010D-2018. Prepare a standard test solution.
  • the standard test solution is the ICP analysis multi-element standard solution of the National Nonferrous Metals Testing Center.
  • the curve concentration points are 0, 0.2, 0.5, 1.0, and 2.0 mg/L respectively.
  • test steps Use ultra-high performance polymer chromatograph: ACQUITY APC; Detector: ACQUITY differential refractometer.
  • the test steps are as follows: (1) Preheating: Install the chromatographic column and pipelines, turn on the console in turn, test the power supply, etc., and open the test software Empower; (2) Parameter setting, injection volume: 0 ⁇ L to 50 ⁇ L (depending on the sample concentration); pump flow rate: 0.2mL/min; mobile phase: 30mol/L LiBr in NMP solution; sealing cleaning liquid: isopropanol; pre-column: PLgel10umMiniMIX-BGuard (size: 50mm ⁇ 4.6mm ⁇ 2); analytical phase: PLgel10umMiniMIX-B (size: 250mm ⁇ 4.6mm); standard: polystyrene sleeve; running time: 30min; Detector: ACQUITY differential refractive index (RI) detector; Column oven temperature: 90°C; Detector temperature: 55°C.
  • Sample testing a. Standard sample and test sample preparation: Weigh 0.002g to 0.004g of standard sample/test sample respectively and add 2mL of mobile phase liquid to prepare a 0.1% to 0.5% mixed standard, and store in the refrigerator for >8h; b. Standard solution/sample testing: Edit the sample group to be tested, select the established sample group method, and after the baseline is stable, click the run queue to start testing the sample; (4) Data processing: Based on the relationship between retention time and molecular weight, use the chemical workstation to establish a calibration curve, integrate and quantify the sample spectrum, and the chemical workstation automatically generates the molecular weight and molecular weight distribution results.
  • Example 1 the ambient temperature of the secondary battery cycle is set to 25°C, and a charge and discharge rate of 0.5C (i.e., 70mA) is used for charge and discharge cycles.
  • the cut-off voltages for charge and discharge are set to 3.8V and 2.0V, respectively.
  • the discharge capacity of the 1500th cycle is recorded, which is the capacity of the battery after 1500 cycles.
  • the ratio of the capacity of the battery after 1500 cycles to the initial capacity of the battery (the discharge capacity of the first cycle) is the cycle capacity retention rate.
  • the cycle capacity retention rate test results of Examples 1-51 and Comparative Examples 1-2 are shown in Table 2.
  • Example 1 the Cu wire is used as the three electrodes and charged at a charging rate of 5C until the negative electrode potential drops to 0 mV, then the battery is switched to low-rate charging and charged at low rates of 4C, 3C, 2C, and 1C in sequence to obtain the maximum charging capacity Map of the battery.
  • step charging is performed using the battery's maximum capacity charging map until the battery cutoff voltage reaches 3.8V.
  • the time required to charge from 0% SOC to 3.8V is recorded as the battery charging time.
  • the current collector containing the negative electrode active material layer obtained in the [Negative Electrode Sheet Preparation] step of Example 1 was subjected to a cross-section scanning electron microscope, and Figure 6 was obtained. It can be seen that the current collector of the embodiment of the present application is provided with a negative electrode active material layer, and the negative electrode active material layer has channels.
  • the acrylic acid lithium polymer is disposed on the side of the negative electrode active material layer away from the current collector, the bonding force between the negative electrode active material layer and the current collector is strong, and the battery containing the negative electrode sheet has excellent cycle performance and fast charging performance.
  • Comparative Example 1 does not add acrylic acid lithium polymer, and Comparative Example 2 has a uniform mixture of acrylic acid lithium polymer and negative electrode active material, and its fast charging performance and cycle performance are worse than those of Examples 1-51.

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Abstract

负极极片及其制备方法、电池和用电设备，负极极片包括集流体、负极活性材料层和导电层，所述负极活性材料层设在所述集流体的至少一侧；所述导电层设在所述负极活性材料层远离所述集流体的一侧，所述导电层包括丙烯酸锂类聚合物，所述负极活性材料层与所述集流体之间的粘结力与所述导电层的面密度负相关。该负极极片，负极活性材料层与集流体之间的粘结力强，且含有负极极片的电池的循环性能和快充性能优异。

Description

负极极片及其制备方法、电池和用电设备
优先权信息
本申请请求2023年12月01日向中国国家知识产权局提交的专利申请202311631966.0的优先权和权益，并且通过参照将其全文并入此处。
技术领域
本申请属于二次电池技术领域，具体涉及一种负极极片及其制备方法、电池和用电设备。
背景技术
二次电池不仅被应用于水力、火力、风力和太阳能电站等储能电源系统，而且还被广泛应用于电动自行车、电动摩托车、电动汽车等电动交通工具，以及军事装备和航空航天等多个领域。
电池的负极极片一般包括集流体和设在集流体上的负极活性材料层。然而，现有的负极活性材料层容易脱落，且电池的循环性能和快充性能差。
发明内容
鉴于背景技术中存在的技术问题，本申请提供一种负极极片，旨在解决负极活性材料层容易脱落，且含有其的电池的循环性能和快充性能差的问题。
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，包括集流体、负极活性材料层和导电层，所述负极活性材料层设在所述集流体的至少一侧；所述导电层设在所述负极活性材料层远离所述集流体的一侧，所述导电层包括丙烯酸锂类聚合物；所述负极活性材料层与所述集流体之间的粘结力与所述导电层的面密度负相关。
本申请至少包括如下所述的有益效果：将丙烯酸锂类聚合物设于负极活性材料层的远离集流体的一侧，所述负极活性材料层与所述集流体之间的粘结力与所述导电层的面密度负相关，可以提升电池的快充能力及循环性能，且可以降低丙烯酸锂类聚合物对负极活性材料层与集流体之间粘结力的影响，使得负极活性材料层不易从集流体上脱落。
在本申请一些实施方式中，所述负极活性材料层上具有孔道，至少部分所述丙烯酸锂类聚合物嵌入到所述孔道中。由此，可以提高丙烯酸锂类聚合物与负极活性材料层的接触面积，在不影响负极活性材料层与集流体间粘结力的前提下，提升电池的快充能力及循环 性能。
在本申请一些实施方式中，满足以下条件中的至少之一：
所述负极活性材料层与所述集流体之间的粘结力与Zk负相关，Zk为所述丙烯酸锂类聚合物在所述负极活性材料层的可靠渗透度，所述孔道中所述丙烯酸锂类聚合物与所述负极活性材料层远离所述集流体的一侧表面的距离为a毫米，所述负极极片的厚度为D毫米，渗透度＝a/D×100％，渗透度分布数达到90％时对应的渗透度为可靠渗透度；
所述负极活性材料层与所述集流体之间的粘结力与所述负极极片的厚度负相关；
所述负极活性材料层与所述集流体之间的粘结力与所述负极活性材料层的曲折度正相关；
所述负极活性材料层与所述集流体之间的粘结力与所述负极活性材料层的孔隙率负相关。由此，可以提升二次电池的循环寿命和快充性能，降低了丙烯酸锂类聚合物对负极活性材料层粘结力的影响，负极活性材料层与集流体间的粘结力强，不易脱落。
在本申请一些实施方式中，Zk＝1％-60％，Zk为所述丙烯酸锂类聚合物在所述负极活性材料层的可靠渗透度，所述孔道中所述丙烯酸锂类聚合物与所述负极活性材料层远离所述集流体的一侧表面的距离为a毫米，所述负极极片的厚度为D毫米，渗透度＝a/D×100％，渗透度分布数达到90％时对应的渗透度为可靠渗透度。由此，可以提升二次电池的循环寿命和快充性能，负极活性材料层与集流体间的粘结力强，不易脱落。
在本申请一些实施方式中，Zk＝25％-45％。由此，可以提升二次电池的循环寿命和快充性能，降低了丙烯酸锂类聚合物对负极活性材料层粘结力的影响，负极活性材料层与集流体间的粘结力强，不易脱落。
在本申请一些实施方式中，a/D×100％＝20％-50％。由此，a/D×100％在上述范围内，可以提升二次电池的循环寿命和快充性能，负极活性材料层与集流体间的粘结力强，不易脱落。
在本申请一些实施方式中，a/D×100％＝25％-40％。由此，a/D×100％在上述范围内，可以提升二次电池的循环寿命和快充性能，负极活性材料层与集流体间的粘结力强，不易脱落。
在本申请一些实施方式中，所述导电层的面密度为0.05g/1540.25mm2-0.4g/1540.25mm2。由此，导电层的面密度在0.05g/1540.25mm2-0.4g/1540.25mm2范围内，可以提升二次电池的循环寿命和快充性能，负极活性材料层与集流体间的粘结力强，不易脱落。
在本申请一些实施方式中，所述负极活性材料层的孔隙率为20％-40％。由此，负极活性材料层的孔隙率在上述范围内，可以提升二次电池的循环寿命和快充性能，负极活性材 料层与集流体间的粘结力强，不易脱落。
在本申请一些实施方式中，所述负极极片的厚度为0.1mm-0.3mm。由此，负极极片的厚度在0.1mm-0.3mm范围内，可以提升二次电池的循环寿命和快充性能，负极活性材料层与集流体间的粘结力强，不易脱落。
在本申请一些实施方式中，所述负极活性材料层的曲折度为0.5-7。由此，负极活性材料层的曲折度在上述范围内，可以提升二次电池的循环寿命和快充性能，负极活性材料层与集流体间的粘结力强，不易脱落。
在本申请一些实施方式中，所述负极活性材料层与所述集流体之间的粘结力为5N/m-20N/m。由此，负极活性材料层与集流体之间的粘结力在5N/m-20N/m范围内，可以提升二次电池的循环寿命和快充性能，负极活性材料层与集流体间的粘结力强，不易脱落。
在本申请一些实施方式中，所述丙烯酸锂类聚合物包括聚丙烯酸锂、聚甲基丙烯酸锂、聚乙基丙烯酸锂或聚丙基丙烯酸锂中的至少一种。由此，丙烯酸锂类聚合物采用以上物质中的至少一种，可以提升二次电池的循环寿命和快充性能，负极活性材料层与集流体间的粘结力强，不易脱落。
在本申请一些实施方式中，基于所述丙烯酸锂类聚合物的总质量，锂的质量分数为3％-8.9％。由此，丙烯酸锂类聚合物中锂的质量分数在上述范围内，可以提升二次电池的循环寿命和快充性能，负极活性材料层与集流体间的粘结力强，不易脱落。
在本申请一些实施方式中，基于所述丙烯酸锂类聚合物的总质量，锂的质量分数为5％-7.5％。由此，丙烯酸锂类聚合物中锂的质量分数在上述范围内，可以提升二次电池的循环寿命和快充性能，负极活性材料层与集流体间的粘结力强，不易脱落。
在本申请一些实施方式中，所述丙烯酸锂类聚合物的数均分子量Mn为3千-100万。由此，丙烯酸锂类聚合物的数均分子量Mn在上述范围内，可以提升二次电池的循环寿命和快充性能，负极活性材料层与集流体间的粘结力强，不易脱落。
在本申请一些实施方式中，所述丙烯酸锂类聚合物的数均分子量Mn为10万-50万。由此，丙烯酸锂类聚合物的数均分子量Mn在上述范围内，可以提升二次电池的循环寿命和快充性能，负极活性材料层与集流体间的粘结力强，不易脱落。
本申请第二方面提供了一种制备负极极片的方法，包括：
在集流体的至少一侧形成负极活性材料层；
在所述负极活性材料层上远离所述集流体的一侧形成导电层，所述导电层包括丙烯酸锂类聚合物；
所述负极活性材料层与所述集流体之间的粘结力与所述导电层的面密度负相关。
由此，采用上述方法制备的负极极片，负极活性材料层与集流体间的粘结力强，不易 脱落，含有其的二次电池的循环寿命和快充性能优异。
在本申请一些实施方式中，采用喷雾法，将丙烯酸锂类聚合物喷涂在负极活性材料层远离所述集流体的一侧，以形成导电层，并使至少部分所述丙烯酸锂类聚合物嵌入到负极活性材料层的孔道中。由此，负极活性材料层与集流体间的粘结力强，不易脱落，含有其的二次电池的循环寿命和快充性能优异。
在本申请的一些实施方式中，喷雾的压力为0.1kPa-100kPa。由此，负极活性材料层与集流体间的粘结力强，不易脱落，含有其的二次电池的循环寿命和快充性能优异。
在本申请的一些实施方式中，喷雾的温度为70℃-150℃。由此，负极活性材料层与集流体间的粘结力强，不易脱落，含有其的二次电池的循环寿命和快充性能优异。
在本申请的一些实施方式中，将含有负极活性材料层的集流体浸泡在丙烯酸锂类聚合物溶液中，以在所述负极活性材料层上远离所述集流体的一侧形成导电层，并使至少部分所述丙烯酸锂类聚合物嵌入到负极活性材料层的孔道中。由此，负极活性材料层与集流体间的粘结力强，不易脱落，含有其的二次电池的循环寿命和快充性能优异。
在本申请的一些实施方式中，基于所述丙烯酸锂类聚合物溶液的总质量，所述丙烯酸锂类聚合物的质量占比为0.5％-50％。由此，负极活性材料层与集流体间的粘结力强，不易脱落，含有其的二次电池的循环寿命和快充性能优异。
在本申请的一些实施方式中，基于所述丙烯酸锂类聚合物溶液的总质量，所述丙烯酸锂类聚合物的质量占比为10％-20％。由此，负极活性材料层与集流体间的粘结力强，不易脱落，含有其的二次电池的循环寿命和快充性能优异。
本申请第三方面提供了一种电池，其包括本申请第一方面的所述的负极极片或第二方面所述的方法制备的负极极片。由此，负极活性材料层与集流体间的粘结力强，不易脱落，该电池的循环寿命和快充性能优异。
本申请第四方面提供了一种用电设备，其包括第三方面所述的电池。
本申请的附加方面和优点将在下面的描述中部分给出，部分将从下面的描述中变得明显，或通过本申请的实践了解到。
附图说明
通过阅读对下文优选实施方式的详细描述，各种其它的优点和益处对于本领域普通技术人员将变得清楚明了。附图仅用于示出优选实施方式的目的，而并不认为是对本申请的限制。而且在全部附图中，用相同的附图标号表示相同的部件。在附图中：
图1是本申请一实施方式的电池单体的结构示意图；
图2是本申请一实施方式的电池模块的结构示意图；
图3是本申请一实施方式的电池包的结构示意图；
图4是图3的分解图；
图5是电池用作电源的用电设备的一实施方式的示意图；
图6是本申请实施例1的负极活性物质层的扫描电镜图。
附图标记说明：
1：电池包；2：上箱体；3：下箱体；4：电池模块；5：电池单体。
具体实施方式
下面对本申请技术方案的实施例进行详细的描述。以下实施例仅用于更加清楚地说明本申请的技术方案，因此只作为示例，而不能以此来限制本申请的保护范围。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。本领域技术人员显式地和隐式地理解的是，本文所描述的实施例可以与其它实施例相结合。
为了简明，本文仅具体地公开了一些数值范围。然而，任意下限可以与任意上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，每个单独公开的点或单个数值自身可以作为下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
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；本申请的说明书和权利要求书及上述附图说明中的术语“包括”和“具有”以及它们的任何变形，意图在于覆盖不排他的包含。
随着电动汽车与可充电移动设备的技术发展和需求提升，二次电池作为新能源领域的代表，与其相关的研究工作也迅猛发展。二次电池具有小的体积和重量，便于携带和使用；比能量较高，能够提供更大的能量储存量，且锂离子电池没有记忆效应，不需要完全放电再充电，因此二次电池具有广泛的应用前景。
人们对二次电池的快充性能要求越来越高，当负极极片中加入丙烯酸锂类聚合物时，电解液的路易斯酸小分子与加入的丙烯酸锂类聚合物中带负电的基团羧酸根相互络合，可以进一步提升羧酸根的电负性，从而使锂离子更容易解离出来，提升电池快充性能。然而，将丙烯酸锂类聚合物直接和负极活性材料混合后应用于电池极片中时，由于丙烯酸锂类聚 合物是线性粘结剂，对负极活性材料颗粒与集流体之间的束缚力变弱，导致负极活性材料层与集流体之间的粘结力降低，负极活性材料层容易脱落。
在本申请中，将丙烯酸锂类聚合物设于负极活性材料层远离集流体的一侧，可以提升负极极片的吸液能力以及锂离子传导能力，在负极发生锂离子充放电时，降低负极的浓差极化，提升电池的快充能力及循环性能；同时丙烯酸锂类聚合物与集流体的接触几率低，可以降低丙烯酸锂类聚合物对负极活性材料层与集流体之间粘结力的影响，使得负极活性材料层不易脱落。
本申请实施例公开的负极极片适用于二次电池，并且本申请实施例公开的电池可以用于使用电池作为电源的用电设备或者使用电池作为储能元件的各种储能系统。用电设备可以包括但不限于手机、平板、笔记本电脑、电动玩具、电动工具、电瓶车、电动汽车、轮船、航天器等等。其中，电动玩具可以包括固定式或移动式的电动玩具，例如，游戏机、电动汽车玩具、电动轮船玩具和电动飞机玩具等等，航天器可以包括飞机、火箭、航天飞机和宇宙飞船等等。
本申请第一方面提出了一种负极极片，包括集流体、负极活性材料层和导电层，所述负极活性材料层设在所述集流体的至少一侧；所述导电层设在所述负极活性材料层远离所述集流体的一侧，所述导电层包括丙烯酸锂类聚合物；
所述负极活性材料层与所述集流体之间的粘结力与所述导电层的面密度负相关。
可以理解的是，丙烯酸锂类聚合物是指取代或未取代的聚丙烯酸锂，聚丙烯酸锂是指聚丙烯酸中的至少一个氢原子被锂原子取代。
本申请至少包括如下所述的有益效果：将丙烯酸锂类聚合物设于负极活性材料层远离集流体的一侧，一方面电解液的小分子可以与丙烯酸锂类聚合物中的羧酸根络合，可以提升负极极片的吸液能力以及对锂离子传导能力，在负极发生锂离子充放电时，降低负极的浓差极化，可以提升电池的快充能力及循环性能；另一方面，丙烯酸锂类聚合物与集流体之间的接触几率低，可以降低丙烯酸锂类聚合物对负极活性材料层与集流体之间粘结力的影响，使得负极活性材料层不易脱落。综上，本申请提出的负极极片，负极活性材料层与集流体之间的粘结力强，且含有负极极片的电池的循环性能和快充性能优异。
可以通过控制导电层的面密度，降低丙烯酸锂类聚合物对负极活性材料层与集流体之间粘结力的影响，使得负极活性材料层不易脱落。负极活性材料层与集流体之间的粘结力强，且含有负极极片的电池的循环性能和快充性能优异。
“导电层的面密度”是指单位面积集流体上的导电层的质量，为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以通过如下方法得到：
第一步：将含有负极活性材料层的集流体冲切成面积为1540.25mm2的小圆片并称重， 质量为g1；
第二步：双面涂布导电层后的极片冲切成面积为1540.25mm2的小圆片并称重，质量为g2；
面密度＝(g2-g1)/1540.25，单位g/1540.25mm2。
在本申请的一些实施方式中，所述负极活性材料层上具有孔道，至少部分所述丙烯酸锂类聚合物嵌入到所述孔道中。由此，可以提高丙烯酸锂类聚合物与负极活性材料的接触面积，丙烯酸锂类聚合物与负极活性材料充分接触，且在不影响负极活性材料层与集流体间粘结力的前提下，提升电池的快充能力及循环性能。
可以理解，所述负极活性材料层上的孔道，是指负极活性物质之间的间隙，负极活性物质层上的孔道可以在扫描电镜图上看出来，负极活性材料层上的孔道的多少可以用孔隙率表示，具体下文详述。
在本申请的一些实施方式中，所述负极活性材料层与所述集流体之间的粘结力与Zk负相关，Zk为所述丙烯酸锂类聚合物在所述负极活性材料层的可靠渗透度，所述孔道中所述丙烯酸锂类聚合物与所述负极活性材料层远离所述集流体的一侧表面的距离为a毫米，所述负极极片的厚度为D毫米，渗透度＝a/D×100％，渗透度分布数达到90％时对应的渗透度为可靠渗透度。
可以理解的是，渗透度的物理意义在于，丙烯酸锂类聚合物在负极活性材料层中的渗透程度，“所述孔道中所述丙烯酸锂类聚合物与所述负极活性材料层远离所述集流体的一侧表面的距离”，是指孔道中，丙烯酸锂类聚合物与负极活性材料层远离所述集流体的一侧表面之间的垂直距离，在负极活性材料层背离集流体一侧的表面上，渗透度为0，当丙烯酸锂类聚合物嵌在集流体和负极活性材料层接触的界面上，渗透度为100％；也即，在孔道中存在丙烯酸锂类聚合物的各个位置，都有对应的渗透度的数值，可靠渗透度是指，在负极活性材料层的各个位置的渗透度中，大于该渗透度的渗透度占90％以上。丙烯酸锂类聚合物在所述负极极片的可靠渗透度可以通过以下方法测定：
通过原位拉曼光谱在线测试，在极片厚度方向识别聚丙烯酸锂主要官能团-COO，特征峰为1460cm-1-1300cm-1，对应所在厚度/极片总厚度即为渗透度，渗透度分布数达到90％时对应的渗透度为可靠渗透度。
负极极片的厚度D可以采用以下方法测定：
使用万分尺测量厚度，使用万分尺在极片横向和纵向各取点10个，取均值作为极片厚度。
负极活性材料层与集流体之间的粘结力，为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以通过如下方法得到：
参考GB/T 2792-2014《胶粘带剥离强度的试验方法》。具体地，取双面涂敷负极材料的极片约15cm-20cm；将极片用3M双面胶贴于钢板上；采用材料试验机INSTRON3365对极片进行测试，得到力与距离之间的关系；计算得出极片粘结力数值。
负极活性材料层与所述集流体之间的粘结力与Zk负相关，是指Zk越大，负极活性材料层与所述集流体之间的粘结力越小，由此，可以通过控制Zk，降低丙烯酸锂类聚合物对负极活性材料层与集流体之间粘结力的影响，使得负极活性材料层不易脱落。负极活性材料层与集流体之间的粘结力强，且含有负极极片的电池的循环性能和快充性能优异。
在本申请一些实施方式中，所述负极活性材料层与所述集流体之间的粘结力与所述负极极片的厚度负相关。由此，可以通过控制负极极片的厚度，降低丙烯酸锂类聚合物对负极活性材料层与集流体之间粘结力的影响，使得负极活性材料层不易脱落。负极活性材料层与集流体之间的粘结力强，且含有负极极片的电池的循环性能和快充性能优异。
负极极片的厚度至少包括集流体的厚度、负极活性材料层的厚度和导电层的厚度之和，负极极片的厚度为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以通过如下方法得到：使用万分尺测量极片厚度。
在本申请一些实施方式中，所述负极活性材料层与所述集流体之间的粘结力与所述负极活性材料层的曲折度正相关。
负极活性材料层与所述集流体之间的粘结力与负极活性材料层的曲折度正相关，是指负极活性材料层的曲折度越大，负极活性材料层与所述集流体之间的粘结力越大，由此，可以通过控制负极活性材料层的曲折度，降低丙烯酸锂类聚合物对负极活性材料层与集流体之间粘结力的影响，使得负极活性材料层不易脱落。负极活性材料层与集流体之间的粘结力强，且含有负极极片的电池的循环性能和快充性能优异。
曲折度即迂曲度，电解液在负极活性材料层中的流动不是沿直线前进，而是迂回曲折地向前流动，迂曲度(tortuosity)就是反映这种迂回曲折的程度，曲折度等于电解液在孔道的实际长度与穿过负极活性材料层的视长度(宏观距离，即负极活性材料层的厚度)的比值，即电解液质点穿越负极活性材料层单位距离时，质点在孔道中运动轨迹的真实长度。
负极活性材料层的曲折度为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以通过如下方法得到：
1.相同的两个极片与隔膜组装成对称电池；
2.注入电解液后浸润；
3.进行电化学阻抗测试，拟合得到电极离子阻抗Rion，计算得到锂电池电极曲折度ε；
4.极片的厚度为L，孔隙率为τ，面积为A；电解液的电导率为σ；
极片的厚度L使用万分尺测量厚度，使用万分尺在极片横向和纵向各取点10个，取均 值作为极片厚度；
孔隙率τ可以参考国家标准GB/T24586-2009《铁矿石表观密度、真密度和孔隙率的测定》测试得到。具体测试方法：将极片浸渍于碳酸甲乙酯(EMC)中清洗；基于气体置换法测定，将负极极片置于真密度测试仪，密闭测试系统，按程序通入氦气，通过检测样品室和膨胀室中的气体的压力。其中，极片中的孔体积占极片总体积的百分比即为极片孔隙率，计算公式：孔隙率＝(V-V0)/V×100％，其中V0为真体积，V为表观体积。
电解液的电导率σ测试可以用本领域公知的仪器及方法进行测定。例如可以参照行业标准HG/T4067-2015《六氟磷酸锂电解液》，设定密度仪的测定温度为20℃，将试样注入仪器的测定池，进行测定并读取数据。
5.曲折度计算采用公式：ε＝(Rion·A·τ·σ)/L。
在本申请一些实施方式中，所述负极活性材料层与所述集流体之间的粘结力与所述负极活性材料层的孔隙率负相关。由此，可以通过控制负极活性材料层的孔隙率，降低丙烯酸锂类聚合物对负极活性材料层与集流体之间粘结力的影响，使得负极活性材料层不易脱落。负极活性材料层与集流体之间的粘结力强，且含有负极极片的电池的循环性能和快充性能优异。
负极活性材料层的孔隙率是指，负极活性材料层中孔隙体积与负极活性材料层总体积的百分比。负极活性材料层的孔隙率为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以通过如下方法得到：
1.用镊子选用＞20片不包含导电层的负极极片，外观良好，边缘无掉粉的圆片装入样品杯。记录片数，计算表观体积V2，表观体积V2＝S×H×A，式中，
S-面积，cm2；
H-厚度，cm；
A-样品数，EA；
2.将装有样品的样品杯，置于真密度测试仪，密闭测试系统，按程序通入氦气，通过检测样品室和膨胀室中的气体的压力；
3.再根据玻尔定律(PV＝nRT)来计算真实体积V1，从而根据下列公式得到待测样品的孔隙率：
孔隙率＝(V2-V1)/V2×100％。
在本申请一些实施方式中，Zk＝1％-60％。例如，Zk可以是1％-59％，5％-55％，10％-50％，15％-45％，20％-40％，25％-35％等，丙烯酸锂类聚合物在负极极片的可靠渗透度在上述范围内，可以提升负极极片的吸液能力以及对锂离子传导能力，提升电池的快充能力及循环性能；此外，丙烯酸锂类聚合物与集流体之间的接触几率低，可以降低丙烯酸锂类聚合物 对负极活性材料层与集流体之间粘结力的影响，使得负极活性材料层不易脱落。负极活性材料层与集流体之间的粘结力强，且含有负极极片的电池的循环性能和快充性能优异。在本申请另一些实施方式中，Zk＝25％-45％。
在本申请一些实施方式中，a/D×100％＝20％-50％，例如，a/D×100％可以是20％-49％，22％-47％，25％-45％，28％-41％，30％-40％，32％-38％，34％-35％等，上述a/D×100％范围内，可以降低丙烯酸锂类聚合物进入负极活性材料层和集流体之间的界面，负极活性材料层与集流体之间的粘结力强，且含有负极极片的电池的循环性能和快充性能优异。在本申请的另一些实施方式中，a/D×100％＝25％-40％。
在本申请一些实施方式中，所述导电层的面密度为0.05g/1540.25mm2-0.4g/1540.25mm2。例如，导电层的面密度Q可以是0.05g/1540.25mm2-0.35g/1540.25mm2，0.1g/1540.25mm2-0.3g/1540.25mm2，0.15g/1540.25mm2-0.25g/1540.25mm2，0.15g/1540.25mm2-0.2g/1540.25mm2等，具体地，导电层的面密度在0.05g/1540.25mm2-0.4g/1540.25mm2范围内，负极活性材料层与集流体之间的粘结力强，且含有负极极片的电池的循环性能和快充性能优异。在本申请的另一些实施方式中，所述导电层的面密度为0.1g/1540.25mm2-0.2g/1540.25mm2。
在本申请一些实施方式中，所述负极活性材料层的孔隙率为20％-40％。例如，所述负极活性材料层的孔隙率τ可以是20％-39％，22％-37％，25％-35％，27％-34％，30％-32％等，具体地，负极活性材料层的孔隙率在上述范围内，负极活性材料层与集流体之间的粘结力强，且含有负极极片的电池的循环性能和快充性能优异。在本申请的另一些实施方式中，所述负极活性材料层的孔隙率为25％-35％。
在本申请一些实施方式中，所述负极极片的厚度为0.1mm-0.3mm。例如，所述负极极片的厚度D可以是0.1mm-0.29mm，0.12mm-0.27mm，0.15mm-0.25mm，0.17mm-0.23mm等，具体地，负极极片的厚度在0.1毫米-0.3毫米范围内，负极活性材料层与集流体之间的粘结力强，且含有负极极片的电池的循环性能和快充性能优异。在本申请的另一些实施方式中，所述负极极片的厚度为0.1mm-0.15mm。
在本申请一些实施方式中，所述负极活性材料层的曲折度为0.5-7，例如，所述负极活性材料层的曲折度ε可以是0.5-6.9，1-6.5，1.5-6，2-5.5，2.5-5，3-4.5，3.5-4等，负极活性材料层的曲折度在上述范围内，可以降低丙烯酸锂类聚合物进入负极活性材料层和集流体之间的界面，负极活性材料层与集流体之间的粘结力强，且含有负极极片的电池的循环性能和快充性能优异。在本申请的另一些实施方式中，ε＝2-4。
在本申请一些实施方式中，所述负极活性材料层与所述集流体之间的粘结力为5N/m-20N/m，例如，所述负极活性材料层与所述集流体之间的粘结力F可以是5N/m-19N/m， 7N/m-18N/m，10N/m-15N/m，12N/m-14N/m等，负极活性材料层与所述集流体之间的粘结力在5N/m-20N/m的范围内，负极活性材料层与集流体之间的粘结力强，且含有负极极片的电池的循环性能和快充性能优异。在本申请的另一些实施方式中，F＝7N/m-15N/m。
在本申请一些实施方式中，所述丙烯酸锂类聚合物包括聚丙烯酸锂、聚甲基丙烯酸锂、聚乙基丙烯酸锂或聚丙基丙烯酸锂中的至少一种。具体地，导电层包括上述丙烯酸锂类聚合物，可以提升负极极片的吸液能力以及对锂离子传导能力，可以提升电池的快充能力及循环性能，且负极活性材料层与集流体之间的粘结力强。
在本申请一些实施方式中，基于所述丙烯酸锂类聚合物的总质量，锂的质量分数为3％-8.9％，例如，基于所述丙烯酸锂类聚合物的总质量，锂的质量分数可以是3％-8.9％，3.5％-8.5％，4％-7％，4％-6％等，基于所述丙烯酸锂类聚合物的总质量，锂的质量分数＝锂的质量/丙烯酸锂类聚合物的质量，锂的质量分数在上述范围内，一部分的丙烯酸锂类聚合物渗入到负极活性材料层的孔道中，可以提升负极极片的吸液能力，又会明显提高对锂离子的传导能力，可以提高负极极片的电子电导率，降低内阻，提高锂离子在电极材料中的扩散系数，从而可以提升电池的快充能力及循环性能，且负极活性材料层与集流体之间的粘结力强。在本申请的另一些实施方式中，基于所述丙烯酸锂类聚合物的总质量，锂的质量分数为5％-7.5％。
具体地，“基于所述丙烯酸锂类聚合物的总质量，锂的质量分数”可以通过以下方法测定：
取一定质量M的丙烯酸锂类聚合物样品，采用电感耦合等离子体发射光谱(ICP)法测试锂元素的质量m1，则，锂元素聚合物锂盐中的质量百分数均值＝m1/M×100％。其中，待测样品通过如下方法制备得到：在烧杯中称取0.2g样品，加入10mL浓HNO3溶液，放置在180℃加热板上消解30min，待样品30min消解完成后，冷却到室温，通过漏斗转移消解液到50mL容量瓶中定容，根据行标USEPA-6010D-2018进行测试，准备好标准测试溶液，标准测试溶液为国家有色金属测试中心ICP分析多元素标准溶液，曲线浓度点分别为0、0.2、0.5、1.0、2.0mg/L，通过仪器先做好标准溶液校准曲线，输入样品质量和体积，再测试消解好的溶液，超出曲线范围的溶液需要稀释后在进行测试。最后依据光谱线的强度来测定元素的含量(定量分析)。
在本申请一些实施方式中，所述丙烯酸锂类聚合物的数均分子量Mn为3千-100万，例如，丙烯酸锂类聚合物的数均分子量Mn可以为3千-99万，5千-95万，1万-90万，5万-80万，10万-70万，20万-60万，30万-50万，40万-50万等，上述丙烯酸锂类聚合物的数均分子量Mn范围内，足以提升负极极片的吸液能力以及对锂离子传导能力，可以提升电池的快充能力及循环性能，且对负极活性材料层与集流体之间的粘结力影响较小，降 低负极活性材料层从集流体上脱落的概率。在本申请的另一些实施方式中，所述丙烯酸锂类聚合物的数均分子量Mn为10万-50万。
“丙烯酸锂类聚合物的数均分子量Mn”为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以通过如下方法得到：
采用凝胶渗透色谱法，并参照国家标准GB/T21863-2008《凝胶渗透色谱法(GPC)用四氢呋喃做淋洗液》。
具体可参考如下测试步骤：使用超高效聚合物色谱仪：ACQUITYAPC；检测器：ACQUITY示差折光检测器。测试步骤如下：(1)开机预热：安装好色谱柱和管路，依次打开控制台，测试电源等，打开测试软件Empower；(2)参数设定，进样体积：0μL至50μL(视样品浓度定)；泵流速：0.2mL/min；流动相：30mol/LLiBr的NMP溶液；密封清洗液：异丙醇；预柱：PLgel10umMiniMIX-BGuard(尺寸：50mm×4.6mm×2)；分析相：PLgel10umMiniMIX-B(尺寸：250mm×4.6mm)；标准品：聚苯乙烯套；运行时间：30min；检测器：ACQUITY示差折光(RI)检测器；柱温箱温度：90℃；检测器温度：55℃。(3)样品测试：a.标准样和测试样品配置：分别称取0.002g至0.004g标准样/测试样加入2mL流动相液体，配制成0.1％至0.5％的混标，至于冰箱中>8h；b.标液/样品测试：编辑待测样品组，选择已建立的样品组方法，待基线稳定后，点击运行队列，开始测试样品；(4)数据处理：根据保留时间和分子量的关系，利用化学工作站建立校正曲线，对样品谱图进行积分定量，化学工作站自动生成分子量和分子量分布结果。
在本申请一些实施方式中，所述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。
在本申请一些实施方式中，负极活性材料层中包括负极活性材料，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，还可以使用其它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。
在本申请一些实施方式中，所述负极活性材料包括单质锂或锂合金中的至少一种，所 述锂合金包括锡、锌、铝、镁、银、金、镓、铟、铂、硼、碳、硅中的至少一种。锂合金是指锂与其它金属和/或非金属形成的合金，其它金属和/或非金属包括锡、锌、铝、镁、银、金、镓、铟、铂、硼、碳、硅中的至少一种。利用锂的低工作电压和高比容量，大幅提高了电池的能量密度。
在本申请一些实施方式中，负极活性材料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。
在本申请一些实施方式中，负极活性材料层还可选地包括导电剂。导电剂可包括超导碳、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。
在本申请一些实施方式中，负极活性材料层还可选地包括其它助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
本申请第二方面提供了一种制备负极极片的方法，包括：
S100、在集流体的至少一侧形成负极活性材料层
S200、在所述负极活性材料层上远离所述集流体的一侧形成导电层，所述导电层包括丙烯酸锂类聚合物；
所述负极活性材料层与所述集流体之间的粘结力与所述导电层的面密度负相关
由此，采用上述方法制备的负极极片，将丙烯酸锂类聚合物设于负极活性材料层远离集流体的一侧，一方面电解液的小分子可以与丙烯酸锂类聚合物中的羧酸根络合，可以提升负极极片的吸液能力以及对锂离子传导能力，在负极发生锂离子充放电时，降低负极的浓差极化，可以提升电池的快充能力及循环性能；另一方面，丙烯酸锂类聚合物与集流体之间的接触几率低，可以降低丙烯酸锂类聚合物对负极活性材料层与集流体之间粘结力的影响，使得负极活性材料层不易脱落。负极活性材料层与集流体间的粘结力强，不易脱落，含有其的二次电池的循环寿命和快充性能优异。
在本申请一些实施方式中，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、粘结剂和任意其它组分分散于溶剂(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，即可得到负极活性材料层。
在本申请一些实施方式中，采用喷雾法，将丙烯酸锂类聚合物喷涂在负极活性材料层远离所述集流体的一侧，以形成导电层，并使至少部分所述丙烯酸锂类聚合物嵌入到负极活性材料层的孔道中。由此，负极活性材料层与集流体间的粘结力强，不易脱落，且丙烯酸锂类聚合物可以与负极活性材料充分接触，含有其的二次电池的循环寿命和快充性能优 异。
可以理解的是，喷雾法是将含有丙烯酸锂类聚合物的浆料喷向负极活性材料层背离集流体的一侧，含有丙烯酸锂类聚合物的浆料形成雾状的小液滴，附在负极活性材料层背离集流体的一侧，并进入到孔道中，经干燥之后，形成导电层。这种方法制备得到的导电层，均匀性好，且不易从负极活性材料层脱落。
在本申请一些实施方式中，采用喷雾箱，喷雾箱箱体内部液体为丙烯酸锂类聚合物的浆料，将含有负极活性材料层的集流体经过喷雾箱，干燥后，完成导电层的制备。
在本申请一些实施方式中，喷雾的压力为0.1kPa-100kPa，喷雾的压力即喷雾箱内部的雾化压力，例如，喷雾的压力可以为0.1kPa-99kPa，0.5kPa-98kPa，1kPa-95kPa，10kPa-90kPa，20kPa-80kPa，30kPa-70kPa，40kPa-60kPa，50kPa-60kPa等，上述喷雾压力范围内，可以形成均匀的导电层，导电层不易从负极活性材料层脱落，且负极活性材料层与集流体间的粘结力强，不易脱落，且丙烯酸锂类聚合物可以与负极活性材料充分接触，含有其的二次电池的循环寿命和快充性能优异。
在本申请一些实施方式中，喷雾的温度为70℃-150℃。喷雾的温度即雾化箱内部的温度，例如，喷雾的温度可以为70℃-149℃，80℃-140℃，90℃-130℃，100℃-120℃等，由此，上述喷雾温度的范围内，可以形成均匀的导电层，导电层不易从负极活性材料层脱落，负极活性材料层与集流体间的粘结力强，不易脱落，且丙烯酸锂类聚合物可以与负极活性材料充分接触，含有其的二次电池的循环寿命和快充性能优异。
在本申请一些实施方式中，含有负极活性材料层的集流体经过喷雾箱时，含有负极活性材料层的集流体的速度为0.1m/s-10m/s，例如，含有负极活性材料层的集流体的速度可以为0.1m/s-9.9m/s，0.5m/s-9.5m/s，1m/s-9m/s，2m/s-8m/s，3m/s-7m/s，4m/s-6m/s等，可以形成均匀的导电层，导电层不易从负极活性材料层脱落。在本申请的另一些实施方式中，含有负极活性材料层的集流体的速度为2m/s-5m/s。
在本申请的一些实施方式中，将含有负极活性材料层的集流体浸泡在丙烯酸锂类聚合物溶液中，以在所述负极活性材料层上远离所述集流体的一侧形成导电层，并使至少部分所述丙烯酸锂类聚合物嵌入到负极活性材料层的孔道中。这种方法制备得到的导电层，均匀性好，不易从负极活性材料层脱落，且负极活性材料层与集流体间的粘结力强，不易脱落，且丙烯酸锂类聚合物可以与负极活性材料充分接触，含有其的二次电池的循环寿命和快充性能优异。
在本申请一些实施方式中，丙烯酸锂类聚合物的浆料的温度为50℃-80℃，例如，丙烯酸锂类聚合物的浆料的温度可以为50℃-79℃，55℃-75℃，60℃-70℃等。
在本申请的一些实施方式中，将含有负极活性材料层的集流体以1m/min-50m/min的速 度通过含有丙烯酸锂类聚合物的浸泡液，例如，含有负极活性材料层的集流体通过含有丙烯酸锂类聚合物的浸泡液的速度可以是1m/min-49m/min，5m/min-45m/min，10m/min-40m/min，20m/min-30m/min等，可以形成均匀的导电层，导电层不易从负极活性材料层脱落。在本申请的另一些实施方式中，将含有负极活性材料层的集流体以8m/min-15m/min的速度通过含有丙烯酸锂类聚合物的浸泡液。
在本申请的一些实施方式中，基于所述丙烯酸锂类聚合物溶液的总质量，所述丙烯酸锂类聚合物的质量占比为0.5％-50％，例如，丙烯酸锂类聚合物的质量占比可以为0.5％-49％，1％-45％，5％-40％，10％-30％，15％-25％等。由此，负极活性材料层与集流体间的粘结力强，不易脱落，且丙烯酸锂类聚合物可以与负极活性材料充分接触，含有其的二次电池的循环寿命和快充性能优异。在本申请的另一些实施方式中，基于所述丙烯酸锂类聚合物溶液的总质量，所述丙烯酸锂类聚合物的质量占比为10％-20％。
在本申请的另一些实施方式中，可以采用干法制备导电层，具体地，将丙烯酸锂类聚合物粉末与导电剂等混合，然后在干燥状态下，通过干法工艺直接压制在集流体上。
本申请第三方面提供了一种电池，其包括本申请第一方面的所述的负极极片或第二方面所述的方法制备的负极极片。由此，负极活性材料层与集流体间的粘结力强，不易脱落，该电池的循环寿命和快充性能优异。
电池，是指在放电后可通过充电的方式使活性材料激活而继续使用的电池。
可以理解的是，本申请提出的电池，是锂离子电池。
通常情况下，电池单体包括正极极片、负极极片、隔离膜及电解液。在电池充放电过程中，活性金属离子(锂离子)在正极极片和负极极片之间往返嵌入和脱出。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。电解质在正极极片和负极极片之间起到传导活性金属离子的作用。
[正极极片]
在本申请一些实施方式中，正极极片包括正极集流体，正极集流体可采用金属箔片、泡沫金属或复合集流体。例如，作为金属箔片，可采用银表面处理的铝或不锈钢、不锈钢、铜、铝、炭精电极、碳、镍或钛等。复合集流体可包括高分子材料基层和金属层。泡沫金属可以为泡沫镍、泡沫铜、泡沫铝、泡沫合金等。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、聚对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚苯乙烯、聚乙烯等的基材)上而形成。
在本申请一些实施方式中，所述正极极片还可以包括正极活性材料层，所述正极活性材料层包括正极活性材料，所述正极活性材料的具体种类不做限制，可以采用本领域已知的能够用于电池正极的活性材料，本领域技术人员可以根据实际需求进行选择。
所述正极活性材料可以包括但不限于锂过渡金属氧化物，橄榄石结构的含锂磷酸盐及其各自的改性化合物中的至少一种。锂过渡金属氧化物的示例可包括但不限于锂钴氧化物、锂镍氧化物、锂锰氧化物、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、锂镍钴铝氧化物及其改性化合物中的至少一种。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、磷酸铁锂与碳的复合材料、磷酸锰锂、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及其改性化合物中的至少一种。这些材料均可以通过商业途径获得。
电池在充放电过程中会伴随Li的脱嵌及消耗，电池在放电到不同状态时Li的物质的量含量不同。本申请实施例中关于正极材料的列举中，Li的物质的量含量为材料初始状态，即投料前状态，正极材料应用于电池体系中，经过充放电循环，Li的物质的量含量会发生变化。
本申请实施例中关于正极材料的列举中，O的物质的量含量仅为理论状态值，晶格释氧会导致氧的物质的量含量发生变化，实际O的物质的量含量会出现浮动。
上述各材料的改性化合物可以是对材料进行掺杂改性和/或表面包覆改性。
所述正极活性材料层通常还可选地包括粘接剂、导电剂和其它可选助剂。
作为示例，导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、Super P(SP)、石墨烯及碳纳米纤维中至少一种。
作为示例，粘接剂可以包括丁苯橡胶(SBR)、水性丙烯酸树脂(water-based acrylic resin)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、乙烯-醋酸乙烯酯共聚物(EVA)、聚丙烯酸(PAA)、羧甲基纤维素(CMC)、聚乙烯醇(PVA)及聚乙烯醇缩丁醛(PVB)中的至少一种。
[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]
作为上述的隔离膜，本申请并没有特别的限制，可以根据实际需求选用任意公知的具有电化学稳定性和力学稳定性的多孔结构隔离膜，例如可以包括包含玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种的单层或多层薄膜。
本申请实施例对电池单体的形状没有特别的限制，其可以是圆柱形、方形或其它任意的形状。如图1是作为一个示例的方形结构的电池单体5。
在本申请一些实施方式中，电池单体5可包括外包装。该外包装用于封装正极极片、负极极片和电解质。
在本申请一些实施方式中，外包装可包括壳体和盖板。其中，壳体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。壳体具有与容纳腔连通的开口，盖板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。电极组件封装于所述容纳腔。电池单体所含电极组件的数量可以包括一个或几个，可根据需求来调节。
在本申请一些实施方式中，电池单体的外包装可以包括硬壳，例如硬塑料壳、铝壳、钢壳。
电池单体5的外包装也可以包括软包，例如袋式软包。软包的材质可以是塑料，如可包括聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)中的至少一种。
在本申请一些实施方式中，电池单体可以组装成电池模块，电池模块所含电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图2是作为一个示例的电池模块4。参照图2，在电池模块4中，多个电池单体5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其它任意的方式进行排布。进一步可以通过紧固件将该多个电池单体5进行固定。
电池模块4还可以包括具有容纳空间的外壳，多个电池单体5容纳于该容纳空间。在本申请一些实施方式中，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根据电池包的应用和容量进行调节。
图3和4是作为一个示例的电池包1。参照图3和4，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。
本申请第四方面提供了一种用电设备，其包括第三方面所述的电池。具体的，所述电池可以作为所述用电设备的电源，也可以作为所述用电设备的能量存储单元。所述用电设备可以包括但不限于移动设备(例如手机、笔记本电脑)、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)、电气列车、船舶及卫星、储能系统。
图5是作为一个示例的用电设备。该用电设备包括纯电动车、混合动力电动车、或插电式混合动力电动车。
作为另一个示例的用电设备可以包括手机、平板电脑、笔记本电脑。该用电设备通常要求轻薄化，可以采用电池作为电源。
为了使本申请实施例所解决的技术问题、技术方案及有益效果更加清楚，以下将结合实施例和附图进行进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。以下对至少一个示例性实施例的描述实际上仅仅是说明性的，决不作为对本申请及其应用的任何限制。基于本申请中的实施例，本领域普通技术人员在没有付出创造性劳动前提下所获得的所有其它实施例都属于本申请保护的范围。
实施例1
【正极极片制备】
将正极活性材料磷酸铁锂(LFP)、导电剂乙炔黑、粘结剂聚偏氟乙烯按质量比98:1:1进行混合，加入溶剂N-甲基吡咯烷酮搅拌至体系呈均一状，获得正极浆料；将正极浆料均匀地双面涂覆在正极集流体铝箔上，室温晾干后转移至烘箱继续干燥，然后裁切成40mm×50mm的长方形作为正极极片，正极面容量为3.5mAh/cm2。
【负极极片制备】
(1)负极浆料制备：将96.5wt.％的负极活性材料石墨，2.5wt.％的丁苯橡胶(SBR)粘结剂，1wt.％的SP导电炭黑在去离子水的溶剂中分散均匀，制成负极浆料。
(2)将负极浆料均匀地由涂布机涂覆于集流体上，烘干，得到含有负极活性材料层的集流体。
(3)聚丙烯酸锂浆料的制备：取聚丙烯酸锂分散于去离子水中制成分散液。
(4)将含有负极活性材料层的集流体以5m/s的速度通过含有聚丙烯酸锂浆料的喷雾箱后，喷雾箱的内部雾化压力为25kPa，雾化温度为85℃，再通过冷却箱体，直至聚丙烯酸锂浆料完全干燥凝固。
(5)将干燥的极片收成卷料，正常辊压后得到负极极片。
【隔离膜】
选用聚乙烯多孔膜作为隔离膜。
【电解液制备】
通过将1M的LiPF6溶解在将碳酸亚乙烯酯添加到碳酸亚乙酯、碳酸二乙酯和碳酸二甲酯以1：1：2的体积比混合的溶剂中的溶液中来制备电解液。
将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，然后卷绕得到电极组件；将电极组件置于外包装中，将上述制备好的电解液注入到干燥后的二次电池中，经过真空封装、静置、化成、整形工序，获得二次电池。
实施例2-51及对比例1-2的含有负极极片的二次电池，除参数不同外(参见表1)，其余与实施例1相同。
其中，实施例3-5的含有负极活性材料层的集流体通过含有聚丙烯酸锂浆料的喷雾箱的速度是不同的，实施例3的速度为2m/s，Zk＝45％，实施例4的速度为10m/s，Zk＝1％，实施例5的速度为0.5m/s，Zk＝60％。
实施例20和21中，除负极浆料的配比与实施例1不同外，其余与实施例1相同，实施例20的负极浆料中，含有98wt.％t的负极活性材料石墨，1wt.％的丁苯橡胶(SBR)粘结剂，1wt.％的SP导电炭黑，实施例21中，的负极浆料中，含有95.5wt.％的负极活性材料石墨，3.5wt.％的丁苯橡胶(SBR)粘结剂，1wt.％的SP导电炭黑。
实施例45-49中，除【负极极片制备】(5)(导电层的制备方法)与实施例1不同以外，其余与实施例1相同，【负极极片制备】(5)替换为：将含有负极活性材料层的集流体以10m/min的速度通过含有丙烯酸锂类聚合物溶液的浸泡箱体，再通过冷却箱体，直至聚丙烯酸锂浆料完全干燥凝固。
对比例1中，除将【负极极片制备】(5)(导电层的制备方法)中的含有聚丙烯酸锂浆料替换为去离子水以外，其余与实施例1相同。
对比例2除【负极极片制备】与实施例1不同外，其余与实施例1相同，【负极极片制备】替换为：将95％wt的负极活性材料石墨，2.5％wt的丁苯橡胶(SBR)粘结剂，1％wt的SP导电炭，聚丙烯酸锂在去离子水的溶剂中分散均匀，制成负极浆料。将负极浆料均匀地由涂布机涂覆于集流体上，烘干，得到负极极片。
本申请实施例1-51和对比例1-2的电解液的参数如表1所示。
表1

表1中，“/”表示不添加。
参数测试：
1、可靠渗透度：
通过原位拉曼光谱在线测试，在极片厚度方向识别聚丙烯酸锂主要官能团-COO，特征峰为1460-1-1300cm-1，对应所在厚度/负极极片厚度即为渗透度，渗透度分布数达到90％时对应的渗透度为可靠渗透度。
2、负极极片厚度
使用万分尺测量厚度，使用万分尺在极片横向和纵向各取点10个，取均值作为极片厚度。
3、负极活性材料层与集流体之间的粘结力：
参考GB/T 2792-2014《胶粘带剥离强度的试验方法》。具体地，取双面涂敷负极材料的极片约15-20cm；将极片用3M双面胶贴于钢板上；采用材料试验机INSTRON3365对极片进行测试，得到力与距离之间的关系；计算得出极片粘结力数值。
4、导电层的面密度：
第一步：将含有负极活性材料层的集流体冲切成面积为1540.25mm2的小圆片并称重，质量为g1；
第二步：双面涂布导电层后的极片冲切成面积为1540.25mm2的小圆片并称重，质量为g2；
面密度＝(g2-g1)/1540.25，单位g/1540.25mm2。
5、曲折度：
1)相同的两个极片与隔膜组装成对称电池，
2)注入电解液后浸润，
3)进行电化学阻抗测试，拟合得到电极离子阻抗Rion，计算得到锂电池电极曲折度ε；
4)极片的厚度为L，孔隙率为τ，面积为A；电解液的电导率为σ；
极片的厚度L使用万分尺测量厚度，使用万分尺在极片横向和纵向各取点10个，取均值作为极片厚度；
孔隙率τ可以参考国家标准GB/T24586-2009《铁矿石表观密度、真密度和孔隙率的测定》测试得到。具体测试方法：将极片浸渍于碳酸甲乙酯(EMC)中清洗；基于气体置换法测定，将负极极片置于真密度测试仪，密闭测试系统，按程序通入氦气，通过检测样品室和膨胀室中的气体的压力。其中，极片中的孔体积占极片总体积的百分比即为极片孔隙率，计算公式：孔隙率＝(V-V0)/V×100％，其中V0为真体积，V为表观体积。
电解液的电导率σ测试可以用本领域公知的仪器及方法进行测定。例如可以参照行业标准HG/T4067-2015《六氟磷酸锂电解液》，设定密度仪的测定温度为20℃，将试样注入 仪器的测定池，进行测定并读取数据。
5)曲折度计算采用公式：ε＝(Rion·A·τ·σ)/L。
6、负极活性材料层的孔隙率：
1)用镊子选用＞20片不包含导电层的负极极片，外观良好，边缘无掉粉的圆片装入样品杯。记录片数，计算表观体积V2，表观体积V2＝S×H×A，式中，
S-面积，cm2；
H-厚度，cm；
A-样品数，EA；
2)将装有样品的样品杯，置于真密度测试仪，密闭测试系统，按程序通入氦气，通过检测样品室和膨胀室中的气体的压力；
3)再根据玻尔定律(PV＝nRT)来计算真实体积V1，从而根据下列公式得到待测样品的孔隙率：
孔隙率＝(V2-V1)/V2×100％。
7、基于丙烯酸锂类聚合物的总质量，锂的质量分数：
取一定质量M的丙烯酸锂类聚合物样品，采用电感耦合等离子体发射光谱(ICP)法测试锂元素的质量m1，则，锂元素聚合物锂盐中的质量百分数均值＝m1/M×100％。其中，待测样品通过如下方法制备得到：在烧杯中称取0.2g样品，加入10mL浓HNO3溶液，放置在180℃加热板上消解30min，待样品30min消解完成后，冷却到室温，通过漏斗转移消解液到50mL容量瓶中定容，根据行标USEPA-6010D-2018进行测试，准备好标准测试溶液，标准测试溶液为国家有色金属测试中心ICP分析多元素标准溶液，曲线浓度点分别为0、0.2、0.5、1.0、2.0mg/L，通过仪器先做好标准溶液校准曲线，输入样品质量和体积，再测试消解好的溶液，超出曲线范围的溶液需要稀释后再进行测试。最后依据光谱线的强度来测定元素的含量。
8、丙烯酸锂类聚合物的数均分子量Mn：
采用凝胶渗透色谱法，并参照国家标准GB/T21863-2008《凝胶渗透色谱法(GPC)用四氢呋喃做淋洗液》。
具体可参考如下测试步骤：使用超高效聚合物色谱仪：ACQUITYAPC；检测器：ACQUITY示差折光检测器。测试步骤如下：(1)开机预热：安装好色谱柱和管路，依次打开控制台，测试电源等，打开测试软件Empower；(2)参数设定，进样体积：0μL至50μL(视样品浓度定)；泵流速：0.2mL/min；流动相：30mol/LLiBr的NMP溶液；密封清洗液：异丙醇；预柱：PLgel10umMiniMIX-BGuard(尺寸：50mm×4.6mm×2)；分析相：PLgel10umMiniMIX-B(尺寸：250mm×4.6mm)；标准品：聚苯乙烯套；运行时间：30min； 检测器：ACQUITY示差折光(RI)检测器；柱温箱温度：90℃；检测器温度：55℃。(3)样品测试：a.标准样和测试样品配置：分别称取0.002g至0.004g标准样/测试样加入2mL流动相液体，配制成0.1％至0.5％的混标，至于冰箱中>8h；b.标液/样品测试：编辑待测样品组，选择已建立的样品组方法，待基线稳定后，点击运行队列，开始测试样品；(4)数据处理：根据保留时间和分子量的关系，利用化学工作站建立校正曲线，对样品谱图进行积分定量，化学工作站自动生成分子量和分子量分布结果。
性能测试：
1、电池的循环容量保持率测试：
以实施例1为例，二次电池的循环的环境温度设定为25℃，使用0.5C的倍率(即70mA)进行充放电循环。充放电的截止电压分别设定为3.8V与2.0V。充放电循环1500圈后，记录第1500圈的放电容量，为电池循环1500圈后的的容量。电池循环1500圈后的容量与电池的初始容量(第一圈的放电容量)的比值为循环容量保持率，实施例1-51和对比例1-2的循环容量保持率测试结果见表2。
2、电池的充电时间测试：
(1)以实施例1为例，以Cu丝为三电极，以5C充电倍率进行充电，直至负极电位降至0mV，跳转至低倍率充电，依次以4C、3C、2C、1C低倍率进行充电，得到电池的最大充电能力Map。
(2)从0％SOC开始，以电池最大能力充电Map进行阶梯充电至电池截止电压达到3.8V，记从0％SOC充电至3.8V所需时间为电池的充电时间。
将实施例1的【负极极片制备】步骤得到的含有负极活性材料层的集流体，断面做扫描电镜，得到图6，可以看出，本申请实施例的集流体上设有负极活性材料层，负极活性物质层上具有孔道。
表2

由表2可以看出，本申请实施例1-51中，将丙烯酸锂类聚合物设于负极活性材料层远离集流体的一侧，负极活性材料层与集流体之间的粘结力强，且含有负极极片的电池的循环性能和快充性能优异。对比例1没有添加丙烯酸锂类聚合物，对比例2丙烯酸锂类聚合物和负极活性材料混合均匀，其快充性能和循环性能均比实施例1-51差。
最后应说明的是：以上各实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述各实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围，其均应涵盖在本申请的权利要求和说明书的范围当中。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (25)

  1. 一种负极极片，其中，包括：
    集流体；
    负极活性材料层，所述负极活性材料层设在所述集流体的至少一侧；
    导电层，所述导电层设在所述负极活性材料层远离所述集流体的一侧，所述导电层包括丙烯酸锂类聚合物；
    所述负极活性材料层与所述集流体之间的粘结力与所述导电层的面密度负相关。
  2. 根据权利要求1所述的负极极片，其中，所述负极活性材料层上具有孔道，至少部分所述丙烯酸锂类聚合物嵌入到所述孔道中。
  3. 根据权利要求2所述的负极极片，其中，满足以下条件中的至少之一：
    所述负极活性材料层与所述集流体之间的粘结力与Zk负相关，Zk为所述丙烯酸锂类聚合物在所述负极活性材料层的可靠渗透度，所述孔道中所述丙烯酸锂类聚合物与所述负极活性材料层远离所述集流体的一侧表面的距离为a毫米，所述负极极片的厚度为D毫米，渗透度＝a/D×100％，渗透度分布数达到90％时对应的渗透度为可靠渗透度；
    所述负极活性材料层与所述集流体之间的粘结力与所述负极极片的厚度负相关；
    所述负极活性材料层与所述集流体之间的粘结力与所述负极活性材料层的曲折度正相关；
    所述负极活性材料层与所述集流体之间的粘结力与所述负极活性材料层的孔隙率负相关。
  4. 根据权利要求2所述的负极极片，其中，Zk＝1％-60％，Zk为所述丙烯酸锂类聚合物在所述负极活性材料层的可靠渗透度，所述孔道中所述丙烯酸锂类聚合物与所述负极活性材料层远离所述集流体的一侧表面的距离为a毫米，所述负极极片的厚度为D毫米，渗透度＝a/D×100％，渗透度分布数达到90％时对应的渗透度为可靠渗透度。
  5. 根据权利要求4所述的负极极片，其中，Zk＝25％-45％。
  6. 根据权利要求4所述的负极极片，其中，a/D×100％＝20％-50％。
  7. 根据权利要求4所述的负极极片，其中，a/D×100％＝25％-40％。
  8. 根据权利要求1-7中任一项所述的负极极片，其中，所述导电层的面密度为0.05g/1540.25mm2-0.4g/1540.25mm2。
  9. 根据权利要求1-7中任一项所述的负极极片，其中，所述负极活性材料层的孔隙率为20％-40％。
  10. 根据权利要求1-7中任一项所述的负极极片，其中，所述负极极片的厚度为0.1mm-0.3mm。
  11. 根据权利要求1-7中任一项所述的负极极片，其中，所述负极活性材料层的曲折度为0.5-7。
  12. 根据权利要求1-7中任一项所述的负极极片，其中，所述负极活性材料层与所述集流体之间的粘结力为5N/m-20N/m。
  13. 根据权利要求1-7中任一项所述的负极极片，其中，所述丙烯酸锂类聚合物包括聚丙烯酸锂、聚甲基丙烯酸锂、聚乙基丙烯酸锂或聚丙基丙烯酸锂中的至少一种。
  14. 根据权利要求1-7中任一项所述的负极极片，其中，基于所述丙烯酸锂类聚合物的总质量，锂的质量分数为3％-8.9％。
  15. 根据权利要求1-7中任一项所述的负极极片，其中，基于所述丙烯酸锂类聚合物的总质量，锂的质量分数为5％-7.5％。
  16. 根据权利要求1-7中任一项所述的负极极片，其中，所述丙烯酸锂类聚合物的数均分子量Mn为3千-100万。
  17. 根据权利要求1-7中任一项所述的负极极片，其中，所述丙烯酸锂类聚合物的数均分子量Mn为10万-50万。
  18. 一种制备负极极片的方法，其中，包括：
    在集流体的至少一侧形成负极活性材料层；
    在所述负极活性材料层上远离所述集流体的一侧形成导电层，所述导电层包括丙烯酸锂类聚合物
    所述负极活性材料层与所述集流体之间的粘结力与所述导电层的面密度负相关。
  19. 根据权利要求18所述的方法，其中，采用喷雾法，将丙烯酸锂类聚合物喷涂在负极活性材料层远离所述集流体的一侧，以形成导电层，并使至少部分所述丙烯酸锂类聚合物嵌入到负极活性材料层的孔道中。
  20. 根据权利要求19所述的方法，其中，满足以下条件中的至少之一：
    喷雾的压力为0.1kPa-100kPa；
    喷雾的温度为70℃-150℃。
  21. 根据权利要求18所述的方法，其中，将含有负极活性材料层的集流体浸泡在丙烯酸锂类聚合物溶液中，以在所述负极活性材料层上远离所述集流体的一侧形成导电层，并使至少部分所述丙烯酸锂类聚合物嵌入到负极活性材料层的孔道中。
  22. 根据权利要求21所述的方法，其中，基于所述丙烯酸锂类聚合物溶液的总质量，所述丙烯酸锂类聚合物的质量占比为0.5％-50％。
  23. 根据权利要求21所述的方法，其中，基于所述丙烯酸锂类聚合物溶液的总质量，所述丙烯酸锂类聚合物的质量占比为10％-20％。
  24. 一种电池，其中，包括权利要求1-17中任一项所述的负极极片或权利要求18-23中任一项所述的方法制备的负极极片。
  25. 一种用电设备，其中，包括权利要求24所述的电池。
PCT/CN2024/100868 2023-12-01 2024-06-24 负极极片及其制备方法、电池和用电设备 Pending WO2025112488A1 (zh)

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