WO2025200345A1 - 负极及其制备方法、电池和用电设备 - Google Patents

负极及其制备方法、电池和用电设备

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Publication number
WO2025200345A1
WO2025200345A1 PCT/CN2024/121232 CN2024121232W WO2025200345A1 WO 2025200345 A1 WO2025200345 A1 WO 2025200345A1 CN 2024121232 W CN2024121232 W CN 2024121232W WO 2025200345 A1 WO2025200345 A1 WO 2025200345A1
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WIPO (PCT)
Prior art keywords
negative electrode
current collector
active material
material layer
electrode active
Prior art date
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Pending
Application number
PCT/CN2024/121232
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English (en)
French (fr)
Inventor
何科峰
雷宇
袁晓涛
赵可欣
张博福
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BYD Co Ltd
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BYD Co Ltd
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Publication date
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Publication of WO2025200345A1 publication Critical patent/WO2025200345A1/zh
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • H01M4/0435—Rolling or calendering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0438—Processes of manufacture in general by electrochemical processing
    • H01M4/045—Electrochemical coating; Electrochemical impregnation
    • H01M4/0457—Electrochemical coating; Electrochemical impregnation from dispersions or suspensions; Electrophoresis
    • 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
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M4/625—Carbon or graphite
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • 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 discloses an electrical device comprising the battery described in the third aspect.
  • the graphite in the negative electrode active material layer provided by the present application has a low orientation degree, which is beneficial to improving the ion and electron transmission capacity of the negative electrode.
  • the bonding force between the negative electrode current collector and the negative electrode active material layer is good, which is beneficial to improving the stability and reliability of the negative electrode structure with low orientation degree to adapt to the influence of rapid lithium deintercalation on the negative electrode;
  • the preparation method of the negative electrode is simple and easy to operate, and industrial production can be realized;
  • the battery with the negative electrode has excellent charge and discharge rate, cycle capacity retention rate and service life, which is beneficial to its use in electrical equipment.
  • FIG1 is a schematic cross-sectional view of a negative electrode provided in one embodiment of the present application.
  • FIG2 is a flow chart of a method for preparing a negative electrode according to an embodiment of the present application
  • FIG3 is a schematic diagram of a negative electrode current collector and a magnetic field according to an embodiment of the present application.
  • FIG4 is a schematic diagram of a negative electrode current collector and a magnetic field according to an embodiment of the present application.
  • FIG5 is a schematic diagram of a negative electrode current collector and a magnetic field according to an embodiment of the present application.
  • FIG6 is an electron microscope cross-sectional view of a negative electrode prepared in one embodiment of the present application.
  • the term "and/or” describes the association relationship between associated objects, indicating that three relationships can exist.
  • a and/or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.
  • the character "/" generally indicates that the associated objects are in an "or” relationship.
  • FIG1 is a schematic cross-sectional view of a negative electrode provided in one embodiment of the present application.
  • the negative electrode 10 includes a negative electrode current collector 11 and a negative electrode active material layer 12 disposed on the surface of the negative electrode current collector 11.
  • the negative electrode active material layer 12 includes graphite.
  • the orientation value of the negative electrode active material layer 12 is less than or equal to 3, and the bonding force between the negative electrode current collector 11 and the negative electrode active material layer 12 is greater than or equal to 0.25 N/40 mm.
  • the orientation value (OI value) of the negative electrode active material layer 12 is used to represent the orientation index of the graphite in the negative electrode active material layer 12, that is, the degree of anisotropy of the graphite arrangement in the negative electrode active material layer 12.
  • the OI value is the ratio of the peak area of the (004) characteristic diffraction peak to the peak area of the (110) characteristic diffraction peak in the X-ray diffraction (XRD) spectrum of the negative electrode.
  • the material with a layered structure for example, graphite
  • the material with a layered structure is preferentially arranged in a direction parallel to the current collector.
  • the graphite is arranged approximately parallel to the direction of the negative electrode current collector, which hinders the transmission of ions and electrons, making it impossible to improve the charge and discharge rate of the battery.
  • graphite is used as the negative electrode active material in the negative electrode to ensure the performance of the negative electrode.
  • the particle size D50 of the graphite is 1 ⁇ m-30 ⁇ m, so that the ion migration path is suitable, which is beneficial to improving the ion transmission capacity in the negative electrode; it is also beneficial to increase the compaction density of the negative electrode while reducing the side reactions between the electrolyte during use, thereby further improving the performance of the negative electrode and the battery.
  • the particle size D50 of the graphite can be, but is not limited to, 1 ⁇ m, 5 ⁇ m, 9 ⁇ m, 10 ⁇ m, 13 ⁇ m, 15 ⁇ m, 17 ⁇ m, 20 ⁇ m, 23 ⁇ m, 25 ⁇ m, 28 ⁇ m or 30 ⁇ m, etc.
  • the particle size D50 of the graphite can be 5 ⁇ m-25 ⁇ m. In another embodiment of the present application, the particle size D50 of the graphite can be 7 ⁇ m-22 ⁇ m. In another embodiment of the present application, the particle size D50 of the graphite can be 8 ⁇ m-20 ⁇ m, which is beneficial to further improve the electrochemical performance and performance of the negative electrode. In another embodiment of the present application, the graphite particle size D50 can be 9 ⁇ m-15 ⁇ m. Controlling the graphite particle size D50 within an appropriate range is beneficial for balancing the orientation of the graphite in the negative electrode active material layer 12 and the binding force between the negative electrode current collector 11 and the negative electrode active material layer 12.
  • a smaller particle size D50 indicates an appropriate orientation of the graphite in the negative electrode active material layer 12, but a relatively weak binding force; a larger particle size D50 indicates an appropriate binding force between the negative electrode current collector 11 and the negative electrode active material layer 12, but a poor orientation of the graphite in the negative electrode active material layer 12.
  • Particle size D50 refers to the median particle size of the graphite particles, also known as the volume average particle size, representing the particle size corresponding to a material's cumulative volume distribution percentage of 50%.
  • the graphite particle size D50 can be measured using a laser force tester.
  • Graphite includes at least one of artificial graphite and natural graphite.
  • graphite is used as the negative electrode active material in the negative electrode active material layer.
  • the negative electrode active material in the negative electrode can be only graphite, or can include graphite and other negative electrode active materials.
  • other negative electrode active materials can include but are not limited to at least one of silicon-based materials, intermediate phase microcarbon beads, hard carbon and soft carbon.
  • the mass content of graphite in the negative electrode active material layer is greater than or equal to 80% of the total mass content of the negative electrode active material layer, thereby ensuring the orientation of the negative electrode active material in the negative electrode active material layer, further improving the ion and electron transmission capacity, and improving the rate and cycle performance of the negative electrode.
  • the mass content of graphite in the negative electrode active material layer may be, but is not limited to, 80%, 82%, 85%, 88%, 90%, 91%, 95%, 96%, 96.2%, 96.5%, 96.8%, 97%, 97.3%, 97.5%, 97.9%, 98%, 98.3%, 98.5%, 98.6%, 99%, 99.1%, 99.5%, or 99.8%.
  • the mass content of graphite in the negative electrode active material layer may be 80%-99.9%.
  • the mass content of graphite in the negative electrode active material layer may be 96%-98%.
  • the mass content of graphite in the negative electrode active material layer may be greater than or equal to 50%, which helps to improve the migration rate of ions and electrons in the negative electrode active material layer.
  • the orientation value of the negative electrode active material layer 12 when the orientation value of the negative electrode active material layer 12 is too small, on the one hand, the energy consumption of inducing graphite orientation in the negative electrode active material layer 12 is high, increasing manufacturing costs; on the other hand, during battery charge and discharge, the graphite in the active material layer 12 has too low an orientation value, resulting in a significant expansion direction of the graphite, causing cracking in the negative electrode active material layer 12 and affecting the battery's cycle life.
  • the orientation value of the negative electrode active material layer 12 is too large, the ion and electron transport capabilities are reduced, which is detrimental to the rate performance of the negative electrode. Therefore, the orientation value of the negative electrode active material layer 12 should be within an appropriate range.
  • the orientation value of the negative electrode active material layer 12 may be, but is not limited to, 0.06, 0.09, 0.1, 0.2, 0.5, 0.8, 1, 1.33, 1.5, 1.7, 2, 2.4, 2.5 or 2.8, etc.
  • the orientation value of the negative electrode active material layer 12 may be 0.06-2.5.
  • the orientation value of the negative electrode active material layer 12 may be 0.09-2.5.
  • the orientation value of the negative electrode active material layer 12 may be 0.09-1.33, thereby further improving the ion and electron transfer rate of the negative electrode and improving the performance of the negative electrode.
  • the orientation value of the negative electrode active material layer 12 may be 0.1-2.5.
  • the graphitization degree of the graphite is greater than or equal to 60%, which results in fewer defects in the graphite crystals and better graphite stability, which is beneficial to improving the specific capacity and ion deintercalation ability of the graphite, thereby improving the negative electrode and battery cycle performance and energy density.
  • the graphitization degree of the graphite can be, but is not limited to, greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%, greater than or equal to 85%, greater than or equal to 90%, greater than or equal to 95%, etc.
  • the graphitization degree of the graphite can be measured using X-ray diffraction (XRD).
  • G is the degree of graphitization (%); 0.3440 is the interlayer spacing of non-graphitized carbon (nm); 0.3354 is the interlayer spacing of an ideal graphite crystal (nm), which is also 1/2 of the c-axis lattice constant of hexagonal graphite; d002 is the interlayer spacing of the (002) crystal plane of the graphite material (nm).
  • the negative electrode active material layer further includes a conductive agent.
  • the addition of the conductive agent to the negative electrode active material layer can improve the conductivity of the negative electrode, reduce the resistivity, accelerate the mobility of electrons, increase the migration rate of ions, and improve the charge and discharge efficiency and output power of the battery.
  • the mass content of the conductive agent in the negative electrode active material layer accounts for 0.1%-6.7% of the total mass content of the negative electrode active material layer, which can not only reduce the resistivity of the negative electrode, but also ensure the liquid absorption capacity of the negative electrode active material layer, thereby improving the rate performance of the negative electrode and the battery.
  • the mass content of the conductive agent in the negative electrode active material layer can be, but is not limited to, 0.1%, 0.5%, 0.7%, 1%, 1.1%, 1.4%, 1.5%, 1.7%, 2.2%, 2.5%, 2.6%, 3%, 3.3%, 3.7%, 4%, 4.2%, 4.5%, 5%, 5.5%, 5.8%, 6%, 6.3%, 6.5% or 6.7%, etc.
  • the mass content of the conductive agent in the negative electrode active material layer can be 0.1%-2%. In another embodiment of the present application, the mass content of the conductive agent in the negative electrode active material layer can be 1%-3%. In another embodiment of the present application, the mass content of the conductive agent in the negative electrode active material layer may be 1%-3.5%. In another embodiment of the present application, the mass content of the conductive agent in the negative electrode active material layer may be 4%-6.5%. In the present application, the conductive agent may be selected from materials that can be used in the art to perform a conductive role in the negative electrode. Specifically, the conductive agent may include, but is not limited to, at least one of acetylene black, carbon black, Ketjen black, carbon nanotubes, graphene, carbon nanofibers, and the like.
  • the negative electrode active material layer is made of graphite and a conductive agent.
  • the negative electrode active material layer includes graphite, a conductive agent, and an additive. Adding an additive further enhances the performance of the negative electrode.
  • the additive includes at least one of a binder and a dispersant. Adding a binder can improve the bonding strength within the negative electrode active material layer and between the negative electrode active material layer and the negative electrode current collector, thereby improving the structural stability of the negative electrode. Adding a dispersant can improve the uniformity of the dispersion of graphite and the conductive agent in the negative electrode active material layer, thereby improving the performance of the negative electrode.
  • the weight content of the binder in the negative electrode active material layer is less than or equal to 2.5%.
  • the weight content of the binder in the negative electrode active material layer can be, but is not limited to, 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.4%, 1.5%, 1.7%, 2%, 2.1%, or 2.5%.
  • the weight content of the binder in the negative electrode active material layer may be 0.05%-2.5%.
  • the binder may include, but is not limited to, at least one of polytetrafluoroethylene, polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene latex, and nitrile rubber.
  • the weight content of the dispersant in the negative electrode active material layer is less than or equal to 2.5%.
  • the weight content of the dispersant in the negative electrode active material layer may be, but is not limited to, 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.4%, 1.5%, 1.7%, 2%, 2.1%, or 2.5%.
  • the weight content of the dispersant in the negative electrode active material layer may be 0.05%-2.5%.
  • the dispersant may include, but is not limited to, at least one of sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, lithium carboxymethyl cellulose, and nanocellulose.
  • the distribution density of the conductive agent on the side away from the negative electrode current collector is less than the distribution density of the conductive agent on the side close to the negative electrode current collector.
  • the distribution density of the conductive agent refers to the amount of conductive agent per unit area. In this way, the conductivity of the negative electrode active material layer close to the negative electrode current collector is better, further improving the rate performance of the negative electrode.
  • the distribution density of the conductive agent on the negative electrode current collector side is higher, which is beneficial to increase the bonding strength between the negative electrode active material layer and the negative electrode current collector, and increase the cycle life of the battery.
  • the distribution density of the conductive agent can be tested by SEM.
  • the bonding force between the negative electrode current collector and the negative electrode active material layer is too high, the amount of binder required to be added to the negative electrode increases, and the battery's rate performance will be affected. Therefore, when the bonding force between the negative electrode current collector and the negative electrode active material layer is 0.25N/40mm-2.8N/40mm, it is beneficial to improve the negative electrode's cycle performance and have higher rate performance.
  • the binding force between the negative electrode current collector and the negative electrode active material layer is 0.25N/40mm-2.2N/40mm, the binding force between the negative electrode current collector and the negative electrode active material layer is high and the preparation is convenient.
  • the binding force between the negative electrode current collector and the negative electrode active material layer is 0.3N/40mm-2.2N/40mm.
  • the binding force between the negative electrode current collector and the negative electrode active material layer is 0.8N/40mm-1.3N/40mm.
  • the binding force between the negative electrode current collector and the negative electrode active material layer is 0.25N/40mm-1.8N/40mm.
  • the binding force between the negative electrode current collector and the negative electrode active material layer is 1N/40mm-2.5N/40mm.
  • the resistivity of the negative electrode is 0.1 ⁇ cm-2 ⁇ cm.
  • the orientation value of the negative electrode active material layer 12 in the present application is relatively low, which can form a directional and orderly transmission channel, which is beneficial to the transmission of ions and electrons, and reduces the ion transfer impedance, reduces the resistivity of the negative electrode, is more conducive to fast charging and discharging of the battery, and improves the performance of the battery.
  • the resistivity of the negative electrode can be, but is not limited to, 0.1 ⁇ cm, 0.5 ⁇ cm, 0.9 ⁇ cm, 1 ⁇ cm, 1.2 ⁇ cm, 1.5 ⁇ cm, 1.8 ⁇ cm or 2 ⁇ cm, etc.
  • the resistivity of the negative electrode can be 0.1 ⁇ cm-1.8 ⁇ cm.
  • the resistivity of the negative electrode can be 0.1 ⁇ cm-1.5 ⁇ cm.
  • the thickness of the negative electrode current collector and the negative electrode active material layer can be selected as needed and is not limited thereto.
  • the present application also provides a method for preparing a negative electrode. Please refer to Figure 2, which is a flow chart of the method for preparing a negative electrode provided in one embodiment of the present application, including:
  • S101 providing a negative electrode current collector, coating a negative electrode slurry containing graphite on at least one surface of the negative electrode current collector, and adjusting the orientation of the graphite in the negative electrode slurry using a magnetic field.
  • the orientation of the graphite in the negative electrode slurry is changed under the action of a magnetic field, the orientation of the graphite in the negative electrode active material layer is improved, and a reasonable and orderly arrangement of the graphite in the negative electrode active material layer is achieved, thereby creating a path that makes it easier for ions and electrons to be transported, and improving the migration rate of ions and electrons. This can improve the transmission obstruction and negative electrode performance degradation caused by the natural parallel arrangement of graphite in the negative electrode active material layer.
  • the migration rate of ions and electrons is improved, which is beneficial for use in batteries and improves the battery's charge and discharge rate, cycle capacity retention rate, and service life.
  • the negative electrode current collector includes a first surface and a second surface disposed opposite to each other, and a magnetic field is provided on one side of the first surface and/or the second surface, and the angle between the magnetic moment direction of the magnetic field and the negative electrode current collector is 10°-90°.
  • the angle between the magnetic moment direction of the magnetic field and the surface of the negative electrode current collector to be 10°-90° (e.g., 20°, 30°, 40°, 50°, 60°, 70°, 75°, 80°, or 90°, etc.)
  • the graphite in the negative electrode slurry can be oriented under the action of the magnetic field, achieving directional induction, and obtaining a negative electrode active material layer that facilitates ion transport and electron transport.
  • the magnetic field may be, but is not limited to, generated by a magnetic field device.
  • the magnetic field device may be, but is not limited to, an electromagnet, a permanent magnet, or the like, and may be selected as needed.
  • the magnetic field device may be disposed on a side of the first surface facing away from the second surface, and spaced apart from the first surface; and/or the magnetic field device may be disposed on a side of the second surface facing away from the first surface, and spaced apart from the second surface.
  • FIG. 3 is a schematic diagram of the negative electrode current collector and the magnetic field provided in one embodiment of the present application.
  • the negative electrode current collector 10 includes a first surface 111 and a second surface arranged opposite each other.
  • the arrow indicates the direction of the magnetic moment of the magnetic field.
  • the magnetic field can be generated by a magnetic field device 20.
  • the angle between the magnetic moment direction of the magnetic field and the first surface is ⁇ 1.
  • the angle between the magnetic moment direction of the magnetic field and the first surface is 30°-90°, which is conducive to further optimizing the arrangement of graphite and improving the performance of the negative electrode.
  • the angle between the magnetic moment direction of the magnetic field and the first surface is 40°-80°.
  • the angle between the magnetic moment direction of the magnetic field and the first surface is 60°-90°, which can further cause the graphite in the negative electrode active material layer to tend to be perpendicular to the negative electrode current collector, reduce the tortuosity of the negative electrode, optimize the ion transmission path in the thickness direction of the negative electrode, and further improve the rate performance of the negative electrode.
  • the magnetic field performs at least one of reciprocating motion and rotational motion. That is, under the premise of maintaining the angle between the magnetic moment direction of the magnetic field and the first surface at 10 ° -90 °, the magnetic field can perform reciprocating motion and/or rotational motion, thereby further optimizing the arrangement of graphite, improving the rate performance of the negative electrode, and increasing the cycle performance.
  • the magnetic field can perform reciprocating motion, rotational motion, and reciprocating motion and rotational motion at the same time.
  • the angle between the direction of reciprocating motion and the extension direction of the negative electrode current collector is 0 ° -90 ° (such as 10 °, 20 °, 30 °, 40 °, 45 °, 50 °, 60 °, 70 °, 80 ° or 90 °, etc.).
  • the extension direction of the negative electrode current collector is the length direction of the negative electrode current collector.
  • FIG 4 is a schematic diagram of a negative electrode current collector and a magnetic field according to another embodiment of the present application.
  • the magnetic field can be generated by a magnetic field device 20, which reciprocates in the direction indicated by arrow a.
  • the direction indicated by arrow a is parallel to the first surface, and the direction indicated by arrow b is the extension direction of the negative electrode current collector.
  • the angle between the reciprocating motion and the extension direction of the negative electrode current collector is ⁇ 2. In one embodiment of the present application, the angle between the reciprocating motion and the extension direction of the negative electrode current collector is 10°-80°. In another embodiment of the present application, the angle between the reciprocating motion and the extension direction of the negative electrode current collector is 30°-90°.
  • the angle between the reciprocating motion and the extension direction of the negative electrode current collector is 40°-90°. In yet another embodiment of the present application, the angle between the reciprocating motion and the extension direction of the negative electrode current collector is 50°-90°.
  • the uniformity of graphite distribution can be improved by rotational motion; rotational motion is rotation along the axis.
  • rotational motion is rotation along the axis.
  • the magnetic field device generates a magnetic field, and the magnetic field device can rotate along the central axis of the magnetic field device, so that the magnetic field generates a rotational motion.
  • the magnetic field device can rotate along other axial directions.
  • Figure 5 is a schematic diagram of the negative electrode current collector and the magnetic field provided in another embodiment of the present application.
  • the magnetic field can be generated by the magnetic field device 20, and the magnetic field device rotates along the central axis c of the magnetic field device.
  • the rotation speed of the magnetic field device can be 10r/min (round/min)-60r/min.
  • the rotation speed of the magnetic field device can be, but is not limited to, 15r/min, 20r/min, 25r/min, 30r/min, 35r/min, 40r/min, 45r/min or 50r/min, etc.
  • the strength of the magnetic field is 0.1T-2T, which can not only produce a directional induction effect on graphite, improve the orientation of graphite in the negative electrode active material layer, but also reduce the difficulty of preparation, and will not affect the negative electrode current collector, so as to obtain a negative electrode with excellent performance.
  • the strength of the magnetic field can be, but is not limited to, 0.1T, 0.2T, 0.3T, 0.5T, 0.8T, 0.9T, 1T, 1.2T, 1.5T, 1.7T or 2T, etc.
  • the strength of the magnetic field can be 0.2T-2T.
  • the strength of the magnetic field can be 0.5T-2T.
  • the strength of the magnetic field can be 0.2T-1T.
  • the strength of the magnetic field can be 0.8T-2T, which is conducive to further improving the performance of the negative electrode.
  • the graphite in the negative electrode slurry is oriented and moved under the influence of a magnetic field, thereby producing a high-performance negative electrode.
  • the graphite particle size D50 can be 1 ⁇ m-30 ⁇ m, which facilitates the transport of ions and electrons and reduces side reactions with the electrolyte.
  • the graphite has a degree of graphitization greater than or equal to 60%, which is beneficial for improving the negative electrode and battery cycle performance and energy density.
  • the dispersant content in the negative electrode slurry may be less than or equal to 2%.
  • the dispersant content in the negative electrode slurry may be, but is not limited to, 0.1%, 0.5%, 0.9%, 1%, 1.5%, 1.8%, or 2%.
  • the dispersant content in the negative electrode slurry may be between 0.5% and 2%.
  • the negative electrode slurry may include a solvent to adjust the viscosity of the negative electrode slurry, which is beneficial for coating the negative electrode slurry and orienting the graphite in the negative electrode slurry.
  • the magnetic field can be applied after the negative electrode slurry is set on the surface of the negative electrode current collector, or the magnetic field can be set on one side of the negative electrode current collector before the negative electrode slurry is set.
  • the negative electrode current collector can be placed in a conveying device, and the negative electrode current collector can move with the movement of the conveying device. During the movement, the negative electrode slurry is set on the surface of the negative electrode current collector, and at the same time, the magnetic field is set on one side of the negative electrode current collector. In the present application, the magnetic field can be set on one side of the first surface or the second surface.
  • the final baking temperature is 60°C-200°C, and the time is 1min-30min, so that the graphite can maintain the orientation after induction, and is also beneficial to the bonding of the negative electrode current collector and the negative electrode active material layer, thereby improving the performance of the negative electrode.
  • the final baking temperature may be, but is not limited to, 10°C, 50°C, 70°C, 100°C, 130°C, 150°C, 180°C, or 200°C
  • the final baking time may be, but is not limited to, 1 minute, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes.
  • the final baking temperature is 60°C-180°C, and the time is 5 minutes-25 minutes.
  • the final baking temperature is 140°C-180°C, and the time is 5 minutes-15 minutes.
  • roller pressing is further included.
  • the pressure of the roller pressing is 2t (ton)-35t
  • the roller speed is 0.5m/s-2m/s.
  • the pressure of the roller pressing can be, but is not limited to, 2t, 5t, 9t, 10t, 12t, 15t, 20t, 25t, 30t or 35t
  • the roller speed can be, but is not limited to, 0.5m/s, 1m/s, 1.5m/s, 1.8m/s or 2m/s, etc.
  • An electric field is applied to the negative electrode current collector to impart a positive charge to the negative electrode current collector. Under the action of this electric field, the conductive agent is attracted to move toward one side of the negative electrode current collector, thereby improving the conductivity of the negative electrode active material layer near the negative electrode current collector, thereby reducing the resistivity of the negative electrode.
  • the graphite Under the action of the charge, the graphite also moves toward the current collector, thereby improving the density of the graphite arrangement, optimizing the liquid phase transmission pores, and increasing the liquid storage capacity of the negative electrode active material layer, thereby ensuring the cycle life and rate performance of the battery.
  • the conductive agent and graphite Under the action of the magnetic field and electric field, the conductive agent and graphite are in closer contact near the negative electrode current collector, and the contact surface between the conductive agent and the graphite and the negative electrode current collector is larger. This increases the bonding strength between the negative electrode active material layer and the negative electrode current collector, improving the bonding reliability, which is beneficial for use in the battery and improves the battery's rate performance and rate performance.
  • the negative electrode current collector can be connected to the positive pole of a power supply to make it positively charged.
  • the negative electrode current collector is connected to a DC electric field to make the negative electrode current collector positively charged.
  • a rolling conductive device can be used to connect to the negative electrode current collector to make the negative electrode current collector positively charged.
  • the rolling conductive device has two rollers that clamp the negative electrode current collector in the thickness direction of the negative electrode current collector. The rollers apply a voltage to the negative electrode current collector to make the negative electrode current collector positively charged.
  • an electric field is applied to the negative electrode current collector to make the negative electrode current collector negatively charged.
  • the conductive agent and/or graphite surface can be modified to be positively charged, and then the conductive agent and/or graphite move to one side of the current collector under the action of electrostatic attraction.
  • the voltage of the negative electrode current collector is 0.1V-120V. This can not only make the conductive agent move toward the negative electrode current collector, but also ensure the distribution of the conductive agent in the negative electrode active material layer on the side away from the negative electrode current collector, and it is also beneficial to enhance the dense arrangement of graphite, improve the compaction density and rate performance of the negative electrode.
  • the voltage of the negative electrode current collector can be, but is not limited to, 0.1V, 1V, 5V, 10V, 15V, 20V, 25V, 30V, 50V, 75V, 90V, 100V, 110V, 115V, etc.
  • the voltage of the negative electrode current collector is 5V-35V, which further reduces the difficulty of preparation and ensures preparation safety. At the same time, it is beneficial to further optimize the distribution of graphite and conductive agent in the negative electrode active material layer, further improving the electrochemical performance of the negative electrode.
  • the voltage of the negative electrode current collector is 10V-50V. In another embodiment of the present application, the voltage of the negative electrode current collector is 10 V to 80 V. In one embodiment, the negative electrode current collector is connected to a DC electric field and maintains a voltage of 0.1 V to 120 V. In the present application, during the preparation process of the negative electrode, the voltage of the negative electrode current collector remains stable, which is more conducive to improving the performance of the negative electrode.
  • the negative electrode current collector may be positively charged in any step before the negative electrode slurry on the negative electrode current collector is dried.
  • the negative electrode slurry may be applied to the surface of the negative electrode current collector before an electric field is applied and the negative electrode current collector is positively charged.
  • the negative electrode slurry may be applied after an electric field is applied to one side of the negative electrode current collector and the negative electrode current collector is positively charged.
  • the resistivity of the negative electrode prepared by applying a magnetic field and/or an electric field in the present application is reduced by 5%-60% compared with the ordinary pole piece without applying a magnetic field, which greatly improves the rate performance of the negative electrode and the battery.
  • the preparation method provided by the present application is simple to operate, has controllable process conditions, and low energy consumption. It can effectively improve the ion and electron diffusion capacity, binding force, resistivity, etc. of the negative electrode to obtain a negative electrode with excellent performance. This will thereby improve the charge and discharge rate of the battery and the high-rate cycle capacity retention rate, especially conducive to the electrochemical performance of batteries with high surface density and high compaction density, breaking through the charge and discharge rate and capacity bottlenecks of traditional batteries.
  • the above ions may include, but are not limited to, one of lithium ions, sodium ions, potassium ions, magnesium ions and aluminum ions.
  • the present application also provides a battery comprising a negative electrode according to any of the above embodiments and a positive electrode.
  • the battery having the negative electrode has excellent charge and discharge rates, cycle capacity retention, and service life, which facilitates its use in electrical devices.
  • the battery may be, but is not limited to, a power battery (such as a lithium-ion power battery), an energy storage battery, or the like.
  • the battery further comprises an electrolyte.
  • the positive electrode is immersed in the electrolyte, and at least a portion of the negative electrode is immersed in the electrolyte, thereby ensuring normal operation of the battery.
  • the electrolyte comprises a lithium salt and an organic solvent.
  • the lithium salt may include, but is not limited to, at least one of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium hexafluoroborate, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate , LiC( CF3SO3 ) 2 , and LiN ( C4F9SO2 )( CF3SO3 );
  • the organic solvent may include, but is not limited to , at least one of an ether-based solvent, a nitrile-based solvent, a cyanate-based solvent, a fluoroester-based solvent, a tetrazole -based solvent, a fluorosulfonyl solvent, a chlorosulfonyl solvent, a nitro solvent, a carbonate-based solvent, a dicarbonate-based solvent, a nitrate-based solvent, a fluoroamide-based solvent
  • the battery further comprises a separator disposed between the positive electrode and the negative electrode.
  • the present application has no particular restrictions on the positive electrode and the separator, and can employ, but is not limited to, materials that can be used as battery positive electrodes and separators in the art.
  • the present application also provides an electrical device comprising a battery according to any of the above embodiments.
  • the electrical device can achieve rapid charging and discharging, meeting usage requirements, and has a long service life, thereby enhancing product competitiveness.
  • the electrical device may be a vehicle, electronic device, energy storage system, or the like, and the battery may be provided in the electrical device in the form of a single cell, battery module, or battery pack.
  • graphite particle size D50 is 9.5 ⁇ m
  • carbon black styrene-butadiene rubber
  • carboxymethyl cellulose water
  • the mass content of graphite (artificial graphite) in the negative electrode slurry is 96.5%
  • the mass content of carbon black is 1.5%
  • the mass content of styrene-butadiene rubber is 1%
  • the mass content of carboxymethyl cellulose is 1%.
  • the negative electrode slurry and copper foil are placed in a continuous coating device.
  • the negative electrode slurry is applied to the first surface of the copper foil.
  • a voltage of 25V is applied to the copper foil to make the copper foil positively charged.
  • a magnetic field device is placed at the negative electrode slurry coating outlet.
  • the magnetic field device is set on the side of the second surface opposite to the first surface.
  • the magnetic field strength is 0.8T.
  • the magnetic moment direction of the magnetic field is at an angle of 90° with the first surface of the copper foil.
  • the magnetic field device simultaneously reciprocates.
  • the angle between the reciprocating motion direction and the extension direction of the copper foil i.e., the moving direction
  • the coated negative electrode slurry passes through the magnetic field area for 10 minutes.
  • the temperature of the negative electrode slurry in the magnetic field is 40°C. After drying at 140°C for 10 minutes, it is rolled under a pressure of 10t and a roller speed of 0.5m/s to obtain a negative electrode.
  • the process is similar to that of Example 1, except that the voltage applied to the copper foil is 5V.
  • Example 2 It is substantially the same as Example 1, except that the angle between the reciprocating motion direction and the copper foil extension direction is 40°.
  • the method is substantially the same as Example 1, except that the time for the coated negative electrode slurry to pass through the magnetic field region is 1 minute.
  • the process is substantially the same as that of Example 1, except that the magnetic field strength is 3 T and a voltage of 0.3 V is applied to the copper foil.
  • Example 2 It is roughly the same as Example 1, except that the rolling pressure is 45t.
  • the process is substantially the same as that of Example 1, except that no voltage is applied to the copper foil.
  • the method is substantially the same as Example 1, except that the negative electrode slurry consists of 98% by mass of graphite, 1% by mass of styrene-butadiene rubber, 1% by mass of carboxymethyl cellulose, and the balance of water.
  • Example 2 It is substantially the same as Example 1, except that no magnetic field device is provided.
  • the process is substantially the same as that of Example 1, except that no voltage is applied to the copper foil and no magnetic field device is provided.
  • Example 2 Similar to Example 1, the magnetic field was adjusted so that the orientation value of the negative electrode active material layer was 2.5, and the bonding force between the negative electrode current collector and the negative electrode active material layer was 0.24 N/40 mm.
  • the negative electrodes prepared in Example 1 and Comparative Example 2 were subjected to electron microscopy, where Figure 6 is an electron microscopic cross-sectional view of the negative electrode prepared in Example 1, and Figure 7 is an electron microscopic cross-sectional view of the negative electrode prepared in Comparative Example 2. It can be seen that the arrangement of graphite in the negative electrode of Example 1 tends to be perpendicular to the current collector or stacked at an angle to the current collector, while the arrangement of graphite in the negative electrode of Comparative Example 2 tends to be stacked parallel to the current collector. At the same time, the electron microscopic image of the negative electrode prepared in Comparative Example 1 is similar to that of Comparative Example 2, and the graphite in the negative electrode tends to be stacked parallel to the current collector. Therefore, the preparation method provided in the present application can modify the orientation of graphite, thereby improving the performance of the negative electrode.
  • Areal density test Use a 1.5 cm diameter cutter to sample the negative electrode (including the current collector and the negative electrode active material layer disposed on the current collector) and the negative electrode current collector foil. Weigh the weight using an electronic scale to calculate the negative electrode areal density in g/m 2 .
  • m 1 is the mass content of the negative electrode
  • m 2 is the mass content of the negative electrode current collector
  • the negative electrode areal density m 0 (m 1 - m 2 )/( ⁇ ⁇ (1.5/2) ⁇ (1.5/2)).
  • Compaction density test Use a micrometer to measure and calculate the thickness h 0 of the negative electrode active material layer.
  • the compaction density of the negative electrode can be obtained (unit: g/cm 3 ) .
  • Orientation value (OI value) test The 004 peak intensity and 110 peak intensity of the negative electrode (the negative electrode includes the current collector and the negative electrode active material layer arranged on the current collector) are measured by XRD (scanning range 5°-90°, voltage 1mV, scanning speed 0.5°/min), and the OI value of the negative electrode active material layer is calculated.
  • Adhesion (peel strength) test Apply transparent tape evenly to one side of the negative electrode, tear off one end, and secure it to a test fixture. Use a tensile tester to record the force (N) applied as the tape peels off the electrode sheet.
  • the measurement length is 40 mm, which is the length of time the transparent tape peels from the electrode sheet at the start of the measurement, also known as the device's measurement length.
  • Resistivity test Cut the negative electrode into 40mm x 100mm pieces and place them in a sheet resistance tester. Set the pressure to 400kg and press the start button to automatically test the negative electrode.
  • the negative electrode consists of a current collector and an active material layer.
  • the negative electrodes prepared in the above embodiments and comparative examples were cut to prepare negative electrode sheets with an area density of 230 ⁇ 23g/ m2 , and matched with positive electrode lithium iron phosphate sheets of corresponding size and an area density of 500 ⁇ 50g/ m2 (the mass ratio of lithium iron phosphate, conductive carbon black, and PVDF was 96:2:2); 1 mol of LiPF6 was dissolved in 1 L of organic solvent (the volume ratio of ethylene carbonate and diethyl carbonate was 1:1) to obtain an electrolyte; in a glove box, under an argon atmosphere, the positive electrode, diaphragm, and negative electrode were alternately stacked, and the electrolyte was injected to prepare a soft-pack battery with a designed battery capacity of 1.8Ah.
  • the prepared battery was tested as follows, and the results are shown in Table 2.
  • DC internal resistance test Adjust the state of charge of the above batteries to 50% SOC at 25°C, then charge them at 1.5C for 30s, record the voltage drop of each battery, and calculate the DC resistance DCIR.
  • Discharge capacity ratio The battery is tested at 25°C to measure the variation of discharge capacity with cycle number at different rates of 0.2C, 2C and 5C, with a voltage range of 2.0V-3.8V.
  • the ratio of the first-cycle discharge capacity at 5C rate to the first-cycle discharge capacity at 0.2C (5C/0.2C discharge ratio) is calculated, as is the ratio of the battery capacity after 1000 charge and discharge cycles at 2C rate to the first-cycle 0.2C discharge capacity (2C/0.2C-1000 cycle capacity). These two ratios can be used to evaluate the battery's high-rate charge and discharge capabilities.
  • Example 17 SEM analysis reveals that in the negative electrode prepared in Example 1, the distribution density of the conductive agent gradually increases along the direction from the negative electrode active material layer to the negative electrode current collector. In the negative electrode prepared in Example 17, the conductive agent is roughly evenly distributed throughout the negative electrode active material. This indicates that applying an electric field can further improve the distribution density of the conductive agent, further reducing the resistivity of the negative electrode, and further improving the distribution of graphite, thereby enhancing battery performance. Compared to Example 18, the overall performance of the battery in Example 1 is improved, indicating that the addition of a conductive agent can further enhance the electrochemical performance of the negative electrode and the battery.

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Abstract

一种负极及其制备方法、电池和用电设备。该负极包括负极集流体以及设置在负极集流体表面的负极活性材料层，该负极活性材料层包括石墨，该负极活性材料层的取向值小于或等于3，负极集流体与负极活性材料层之间的结合力大于或等于0.25N/40mm；所述取向值为负极在X射线衍射谱图中（004）特征衍射峰的峰面积与（110）特征衍射峰的峰面积的比值。

Description

负极及其制备方法、电池和用电设备
本申请要求于2024年03月29日提交中国专利局、申请号为202410382797X、申请名称为“负极及其制备方法、电池和用电设备”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及电池技术领域，具体涉及一种负极及其制备方法、电池和用电设备。
背景技术
石墨材料由于具有成本低、能量密度高等优势，在电池负极中广泛使用。目前，随着用户使用需求的不断提高，越来越多的用电产品需要实现快充功能，这就需要对用电产品中的电池进行研究和改进。然而，电池负极中石墨材料的层状结构，会使其在制片过程中，更易于平行于集流体排布，进而快充性能不理想。
发明内容
有鉴于此，本申请的目的在于提供一种负极及其制备方法、电池和用电设备，该负极具有优异的离子和电子扩散能力，并且内部稳定性好，有利于提升电池的充放电倍率、循环容量保持率以及使用寿命。
第一方面，本申请公开了一种负极，包括负极集流体以及设置在所述负极集流体表面的负极活性材料层，所述负极活性材料层包括石墨，所述负极活性材料层的取向值小于或等于3，所述负极集流体与所述负极活性材料层之间的结合力大于或等于0.25N/40mm。
第二方面，本申请公开了一种负极的制备方法，包括：提供负极集流体，将含有石墨的负极浆料涂覆在所述负极集流体至少一侧表面上，用磁场调整所述负极浆料中所述石墨的取向；
经烘干后得到负极活性材料层的取向值小于或等于3的负极；负极集流体与负极活性材料层之间的结合力大于或等于0.25N/40mm。
第三方面，本申请公开了一种电池，包括第一方面所述的负极或第二方面所述的制备方法制得的负极，以及正极。
第四方面，本申请公开了一种用电设备，包括第三方面所述的电池。
结合上述技术方案，本申请提供的负极活性材料层中石墨的取向度低，有利于提升负极的离子和电子传输能力，同时负极集流体与负极活性材料层之间的结合力佳，有利于提升低取向度的负极结构的稳定性、可靠性以适应快速脱嵌锂对负极的影响；该负极的制备方法简单，操作方便，可以实现工业化生产；具有该负极的电池的充放电倍率、循环容量保持率和使用寿命优异，有利于其在用电设备中使用。
附图说明
图1为本申请一实施方式提供的负极的截面示意图；
图2为本申请一实施例提供的负极的制备方法流程图；
图3为本申请一实施例提供的负极集流体与磁场的示意图；
图4为本申请一实施例提供的负极集流体与磁场的示意图；
图5为本申请一实施例提供的负极集流体与磁场的示意图；
图6为本申请一实施例制得的负极的电镜截面图；
图7为本申请一对比例制得的负极的电镜截面图。
具体实施方式
本申请实施例中术语“和/或”，描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。字符“/”一般表示前后关联对象是一种“或”的关系。
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
请参阅图1，为本申请一实施方式提供的负极的截面示意图，负极10包括负极集流体11以及设置在负极集流体11表面的负极活性材料层12，负极活性材料层12包括石墨，负极活性材料层12的取向值小于或等于3，负极集流体11与负极活性材料层12之间的结合力大于或等于0.25N/40mm。可以理解的，负极活性材料层12的取向值(OI值)用于表示负极活性材料层12中石墨的取向指数，即负极活性材料层12中石墨排列的各向异性程度，OI值为负极在X射线衍射(XRD)谱图中(004)特征衍射峰的峰面积与(110)特征衍射峰的峰面积的比值。
电池负极制程中，涂布、辊压等工序会使具有层状结构的材料(例如，石墨)产生优先取向，也即，使具有层状结构的材料优先按平行于集流体的方向排列。石墨近似平行于负极集流体的方向排列，阻碍离子和电子的传输，使得电池的充放电倍率无法得到提升。本申请负极活性材料层12中石墨的取向度低，有利于离子和电子的传输，提高了离子和电子的迁移速率；并且离子嵌入发生的膨胀可以在负极活性材料层12中均匀分散，从而有利于负极倍率性能以及循环性能的发挥。同时负极集流体与负极活性材料层12之间的结合力较高(大于或等于0.25N/40mm)，有利于提升负极内部结构的稳定性以适应快速脱嵌锂对负极的影响，从而有助于负极在电池中使用，提升电池的充放电倍率、高倍率循环容量保持率。
在本申请中，石墨作为负极中的负极活性材料，保证了负极的使用性能。
在本申请一实施方式中，石墨的粒径D50为1μm-30μm，使得离子迁移路径合适，有利于提升负极中离子的传输能力；还有利于增加负极的压实密度同时，减少使用时与电解液之间的副反应，从而进一步提升负极和电池的性能。具体的，石墨的粒径D50可以但不限于为1μm、5μm、9μm、10μm、13μm、15μm、17μm、20μm、23μm、25μm、28μm或30μm等。在本申请一实施例中，石墨的粒径D50可以为5μm-25μm。在本申请另一实施例中，石墨的粒径D50可以为7μm-22μm。在本申请又一实施例中，石墨的粒径D50可以为8μm-20μm，有利于进一步提升负极的电化学性能和使用性能。在本申请又一实施例中，石墨的粒径D50可以为9μm-15μm。石墨的粒径D50控制在合适的范围内，有利于平衡负极活性材料层12中石墨的取向度和负极集流体11与负极活性材料层12之间的结合力。粒径D50较小，负极活性材料层12中石墨的取向度合适，但结合力相对较弱；粒径D50较大，负极集流体11与负极活性材料层12之间的结合力合适，但负极活性材料层12中石墨的取向度较差。粒径D50指的是石墨颗粒的中值粒径，又称体积平均粒径，表示材料累计体积分布百分数达到50％时所对应的粒径。石墨的粒径D50可用激光力度测试仪测试得到。石墨包括人造石墨或天然石墨中至少一种。
在本申请中，石墨作为负极活性材料层中的负极活性材料，可以理解的，负极中的负极活性材料可以仅为石墨，也可以包括石墨和其他负极活性材料。具体的，其他负极活性材料可以但不限于包括硅基材料、中间相微碳球、硬碳和软碳等中的至少一种。在本申请一实施方式中，负极活性材料层中石墨的质量含量大于或等于所述负极活性材料层总质量含量的80％，从而保证了负极活性材料层中负极活性材料的取向，进一步提升离子和电子传输能力，提高负极的倍率和循环性能。具体的，负极活性材料层中石墨的质量含量可以但不限于为80％、82％、85％、88％、90％、91％、95％、96％、96.2％、96.5％、96.8％、97％、97.3％、97.5％、97.9％、98％、98.3％、98.5％、98.6％、99％、99.1％、99.5％或99.8％等。在本申请一实施例中，负极活性材料层中石墨的质量含量可以为80％-99.9％，在本申请另一实施例中，负极活性材料层中石墨的质量含量可以为96％-98％。在本申请又一实施例中，负极活性材料层中石墨的质量含量可以为96.5％-99％。在本申请又一实施例中，负极活性材料层中石墨的质量含量可以为97％-99％。在本申请又一实施例中，负极活性材料层中石墨的质量含量可以为80％-96％。在本申请又一实施例中，负极活性材料层中石墨的质量含量可以为85％-93％。在本申请另一实施方式中，负极活性材料层中的负极活性材料包括石墨和其他负极活性材料时，负极活性材料层中石墨的质量含量可以大于或等于50％，有助于提升负极活性材料层中离子和电子的迁移速率。
在本申请中，负极活性材料层12的取向值小于或等于3，从而使得负极活性材料层中石墨的取向更有利于离子和电子传输，提高负极的倍率性能。在本申请一实施方式中，负极活性材料层12的取向值为0.06-3，既能够保证负极使用过程中离子和电子的传输能力，增加负极的倍率性能和循环性能，同时也可以降低负极的制备难度以及制备成本，有利于该负极的商业应用。可以理解的，当负极活性材料层12的取向值过小，一方面，诱导负极活性材料层12中石墨取向的能耗较高，增加制造成本；另一方面，电池充放电过程中，活性材料层12中的石墨取向度过小，使得石墨的膨胀方向明显，造成负极活性材料层12开裂，影响电池的循环寿命。当负极活性材料层12的取向值过大，离子和电子的传输能力降低，不利于负极的倍率性能。因此，负极活性材料层12的取向值应在合适的范围内。具体的，负极活性材料层12的取向值可以但不限于为0.06、0.09、0.1、0.2、0.5、0.8、1、1.33、1.5、1.7、2、2.4、2.5或2.8等。在本申请一实施例中，负极活性材料层12的取向值可以为0.06-2.5。在本申请另一实施例中，负极活性材料层12的取向值可以为0.09-2.5。在本申请又一实施例中，负极活性材料层12的取向值可以为0.09-1.33，从而进一步提升负极的离子和电子传输速率，提高负极的性能。在本申请又一实施例中，负极活性材料层12的取向值可以为0.1-2.5。
在本申请一实施方式中，石墨的石墨化度大于或等于60％，使得石墨晶体中缺陷少，石墨稳定性更好，有利于提高石墨的克容量和离子脱嵌能力，从而有利于提升负极和电池循环性能和能量密度。具体的，石墨的石墨化度可以但不限于大于或等于70％、大于或等于75％、大于或等于80％、大于或等于85％、大于或等于90％、大于或等于95％等。石墨的石墨化度可使用X射线衍射法(XRD法)测量。获得负极的XRD图谱，基于图谱计算得到负极中石墨(002)晶面层间距d002，然后代入Mering–Maire公式(也称富兰克林公式)计算：G＝(0.3440–d002)/(0.3440–0.3354)×100％。其中，G为石墨化度(％)；0.3440为非石墨化炭的层间距(nm)；0.3354为理想石墨晶体的层间距(nm)，亦为六方晶系石墨c轴点阵常数的1/2；d002为石墨材料(002)晶面的层间距(nm)。
在本申请一实施方式中，负极活性材料层还包括导电剂。负极活性材料层中导电剂的加入可以提高负极的电导率，减小电阻率，加速电子的移动速率，也能够提高离子的迁移速率，提升电池的充放电效率、输出功率等。
在本申请一实施方式中，负极活性材料层中导电剂的质量含量占所述负极活性材料层总质量含量的0.1％-6.7％，既能够降低负极的电阻率，还保证了负极活性材料层的吸液量，提升负极和电池的倍率性能。具体的，负极活性材料层中导电剂的质量含量可以但不限于为0.1％、0.5％、0.7％、1％、1.1％、1.4％、1.5％、1.7％、2.2％、2.5％、2.6％、3％、3.3％、3.7％、4％、4.2％、4.5％、5％、5.5％、5.8％、6％、6.3％、6.5％或6.7％等。在本申请一实施例中，负极活性材料层中导电剂的质量含量可以为0.1％-2％。在本申请另一实施例中，负极活性材料层中导电剂的质量含量可以为1％-3％。在本申请又一实施例中，负极活性材料层中导电剂的质量含量可以为1％-3.5％。在本申请又一实施例中，负极活性材料层中导电剂的质量含量可以为4％-6.5％。在本申请中，导电剂可以选择本领域中能够用于负极中起到导电作用的材料，具体的，导电剂可以但不限于包括乙炔黑、炭黑、科琴黑、碳纳米管、石墨烯、碳纳米纤维等中的至少一种。
在本申请一实施方式中，负极活性材料层的材质为石墨和导电剂。在本申请另一实施方式中，负极活性材料层的材质包括石墨、导电剂和助剂。通过加入助剂进一步提升负极的性能。在本申请一实施例中，助剂包括粘结剂和分散剂中的至少一种。通过加入粘结剂可以提高负极活性材料层内部以及负极活性材料层与负极集流体之间的结合力，从而提高负极的结构稳定性；通过加入分散剂可以提高负极活性材料层中石墨、导电剂的分散均匀性，从而提升负极的使用性能。在一实施例中，负极活性材料层中粘结剂的质量含量小于或等于2.5％。具体的，负极活性材料层中粘结剂的质量含量可以但不限于为0.05％、0.1％、0.3％、0.5％、0.8％、1％、1.4％、1.5％、1.7％、2％、2.1％或2.5％等。在一具体实施例中，负极活性材料层中粘结剂的质量含量可以为0.05％-2.5％。在本申请中，粘结剂可以但不限于包括聚四氟乙烯、聚偏氟乙烯、羧甲基纤维素钠、丁苯胶乳、丁腈橡胶中的至少一种。在一实施例中，负极活性材料层中分散剂的质量含量小于或等于2.5％。具体的，负极活性材料层中分散剂的质量含量可以但不限于为0.05％、0.1％、0.3％、0.5％、0.8％、1％、1.4％、1.5％、1.7％、2％、2.1％或2.5％等。在一具体实施例中，负极活性材料层中分散剂的质量含量可以为0.05％-2.5％。在本申请中，分散剂可以但不限于包括羧甲基纤维素钠、羧甲基纤维素钾、羧甲基纤维素锂、纳米纤维素中的至少一种等。
在本申请一实施方式中，负极活性材料层中，远离负极集流体一侧的导电剂的分布密度小于靠近负极集流体一侧的导电剂的分布密度。导电剂的分布密度，是指单位区域内的导电剂的数量。如此，使得靠近负极集流体一侧的负极活性材料层的导电性能更好，进一步提升负极的倍率性能。同时，导电剂在负极集流体侧分布密度较高，有利于增加负极活性材料层和负极集流体的粘结强度，增加电池的循环寿命。导电剂的分布密度可通过SEM进行测试，例如对负极使用Cross Section Polisher，CP(氩离子束对负极片进行切割抛光，切割方向为垂直于负极集流体的方向)处理得到极片截面，分别对极片界面处进行扫描，即可获导电剂的分布密度，从而可进一步统计得远离负极集流体一侧的导电剂的分布密度与靠近负极集流体一侧的导电剂的分布密度趋势。
在本申请一实施方式中，沿负极活性材料层至负极集流体的方向上，导电剂的分布密度逐渐增加。如此，使负极中的离子和电子的迁移速率均匀提升，且使负极活性材料层12与负极集流体的之间，以及负极活性材料层12中负极活性材料彼此之间结合力更稳定，有利于提升电池的使用稳定性。示例性的，负极活性材料层至负极集流体的方向为图1中箭头所指示的方向。在本申请一实施方式中，负极集流体为金属材质。金属材质包括铜、镍、铁、钴中的至少一种以及不锈钢。在一具体实施例中，负极集流体为铜箔。
在本申请中，负极集流体与负极活性材料层之间的结合力大于或等于0.25N/40mm，使负极具有较佳的稳定性。在本申请中，
在本申请一实施方式中，负极集流体与负极活性材料层之间的结合力为0.25N/40mm-2.8N/40mm，使负极内部的稳定性和可靠性高，有利于提升负极的循环性能还具备较高的倍率性能。可以理解的，当负极活性材料层12的取向值减小(也即在本申请范围内)，负极活性材料层12中石墨的状态由现有技术中平行于集流体的排布方式，向垂直负极集流体的排布方式转变。此时，负极活性材料层11中石墨与集流体的接触面积降低，粘结力减弱，不利于电池的循环性能。负极集流体与负极活性材料层之间的结合力过高时，负极中需要添加的粘结剂含量增加，电池的倍率性能会受到影响。因此，负极集流体与负极活性材料层之间的结合力为0.25N/40mm-2.8N/40mm时，有利于提升负极的循环性能还具备较高的倍率性能。具体的，负极集流体与负极活性材料层之间的结合力可以但不限于为0.25N/40mm、0.3N/40mm、0.5N/40mm、0.8N/40mm、1N/40mm、1.2N/40mm、1.4N/40mm、1.5N/40mm、1.6N/40mm、1.7N/40mm、1.8N/40mm、1.9N/40mm、2N/40mm、2.1N/40mm、2.2N/40mm、2.3N/40mm、2.4N/40mm、2.5N/40mm、2.6N/40mm、2.7N/40mm或2.8N/40mm等。在本申请一实施例中，负极集流体与负极活性材料层之间的结合力为0.25N/40mm-2.2N/40mm，负极集流体与负极活性材料层之间的结合力高且制备方便。在本申请另一实施例中，负极集流体与负极活性材料层之间的结合力为0.3N/40mm-2.2N/40mm。在本申请又一实施例中，负极集流体与负极活性材料层之间的结合力为0.8N/40mm-1.3N/40mm。在本申请又一实施例中，负极集流体与负极活性材料层之间的结合力为0.25N/40mm-1.8N/40mm。在本申请又一实施例中，负极集流体与负极活性材料层之间的结合力为1N/40mm-2.5N/40mm。
在本申请一实施方式中，负极的电阻率为0.1Ω·cm-2Ω·cm。本申请中负极活性材料层12的取向值较低，可以形成定向有序的传输通道，有利于离子和电子的传输，并且减小离子传递阻抗，降低负极的电阻率，更有利于电池的快充快放，提升电池的使用性能。具体的，负极的电阻率可以但不限于为0.1Ω·cm、0.5Ω·cm、0.9Ω·cm、1Ω·cm、1.2Ω·cm、1.5Ω·cm、1.8Ω·cm或2Ω·cm等。在本申请一实施方式中，负极的电阻率可以为0.1Ω·cm-1.8Ω·cm。在本申请另一实施方式中，负极的电阻率可以为0.1Ω·cm-1.5Ω·cm。
在本申请中，负极集流体和负极活性材料层的厚度可以根据需要进行选择，对此不作限定。
本申请还提供了一种负极的制备方法。请参阅图2，为本申请一实施方式提供的负极的制备方法流程图，包括：
S101：提供负极集流体，将含有石墨的负极浆料涂覆在负极集流体至少一侧表面上，用磁场调整负极浆料中石墨的取向。
S102：经烘干后得到负极活性材料层的取向值小于或等于3的负极，负极集流体与负极活性材料层之间的结合力大于或等于0.25N/40mm。
本申请提供的负极的制备方法中，在磁场作用下改变负极浆料中石墨取向方式，改善负极活性材料层中石墨的取向度，实现负极活性材料层中石墨的合理有序排列，产生更容易使离子和电子传输的路径，提高离子和电子的迁移速率，可以改善负极活性材料层中石墨自然的平行排列带来的传输阻碍及负极性能劣化的问题。同时，在保证负极活性材料层与负极集流体的结合力大于或等于0.25N/40mm的情况下，提高离子和电子的迁移速率，如此有利于在电池中使用，提升电池的充放电倍率、循环容量保持率和使用寿命。
在本申请一实施方式中，负极集流体包括相对设置的第一表面和第二表面，在第一表面和/或第二表面的一侧设置磁场，磁场的磁矩方向与负极集流体的夹角为10°-90°。在本申请中，通过控制磁场的磁矩方向与负极集流体表面的夹角为10°-90°(如20°、30°、40°、50°、60°、70°、75°、80°或90°等)，从而使得负极浆料涂覆在负极集流体后，负极浆料中的石墨可以在磁场作用下发生取向，实现定向诱导，获得便于离子传输与电子传输的负极活性材料层。
本申请中磁场可以但不限于由磁场装置产生，磁场装置可以但不限于为电磁体、永磁体等，具体可以根据需要进行选择。在本申请一实施方式中，磁场装置可以设置在第一表面背离第二表面的一侧，且与第一表面间隔设置；和/或，磁场装置可以设置在第二表面背离第一表面的一侧，且与第二表面间隔设置。
请参阅图3，为本申请一实施方式提供的负极集流体与磁场的示意图，其中负极集流体10包括相对设置的第一表面111和第二表面，箭头所指示为磁场的磁矩方向，磁场可以由磁场装置20产生，磁场的磁矩方向与第一表面的夹角为θ1。在本申请一实施方式中，磁场的磁矩方向与第一表面的夹角为30°-90°，有利于进一步优化石墨的排列方式，提升负极的性能。在本申请另一实施方式中，磁场的磁矩方向与第一表面的夹角为40°-80°。在本申请又一实施方式中，磁场的磁矩方向与第一表面的夹角为60°-90°，可以进一步使负极活性材料层中的石墨产生趋向垂直负极集流体排列形式，降低负极迂曲度，优化离子在负极厚度方向上的传输路径，进一步提升负极的倍率性能。
在本申请一实施方式中，磁场进行往复运动和旋转运动中的至少一种。也就是说，在保持磁场的磁矩方向与第一表面的夹角为10°-90°的前提下，磁场可以进行往复运动和/或旋转运动，从而进一步优化石墨的排布情况，提升负极的倍率性能的同时，还能增加循环性能。磁场可以进行往复运动，也可以进行旋转运动，还可以同时进行往复运动和旋转运动。在本申请一实施方式中，往复运动的运动方向与负极集流体的延伸方向的夹角为0°-90°(如10°、20°、30°、40°、45°、50°、60°、70°、80°或90°等)。可以理解的，负极集流体的延伸方向为负极集流体的长度方向。通过采用往复运动，可以改善石墨的排列角度，进一步优化离子在平行于负极集流体方向的扩散路径和电子传输方向上的扩散路径，提升负极的使用性能。
请参阅图4，为本申请另一实施方式提供的负极集流体与磁场的示意图，磁场可以由磁场装置20产生，磁场装置20沿箭头a所指示的方向进行往复运动，其中箭头a所指示的方向与第一表面平行，箭头b所指示的方向为负极集流体的延伸方向，往复运动的运动方向与负极集流体的延伸方向的夹角为θ2。在本申请一实施例中，往复运动的运动方向与负极集流体的延伸方向的夹角为10°-80°。在本申请另一实施例中，往复运动的运动方向与负极集流体的延伸方向的夹角为30°-90°。在本申请又一实施例中，往复运动的运动方向与负极集流体的延伸方向的夹角为40°-90°。在本申请又一实施例中，往复运动的运动方向与负极集流体的延伸方向的夹角为50°-90°。
在本申请中，通过旋转运动可以提升石墨分布的均匀性；旋转运动为沿轴心发生旋转。在一具体实施例中，磁场装置产生磁场，磁场装置可以沿磁场装置的中心轴旋转，从而使磁场产生旋转运动。当然，在其他实施例中，磁场装置可以沿其他轴向旋转。请参阅图5，为本申请又一实施方式提供的负极集流体与磁场的示意图，磁场可以由磁场装置20产生，磁场装置沿磁场装置的中心轴c旋转。在本申请一实施方式中，磁场装置旋转速度可以为10r/min(round/min)-60r/min。具体的，磁场装置旋转速度可以但不限于为15r/min、20r/min、25r/min、30r/min、35r/min、40r/min、45r/min或50r/min等。
在本申请一实施方式中，磁场的强度为0.1T-2T，既能够对石墨产生定向诱导作用，改善负极活性材料层中石墨的取向，同时降低制备难度，又不会对负极集流体产生影响，能够获得性能优异的负极。具体的，磁场的强度可以但不限于为0.1T、0.2T、0.3T、0.5T、0.8T、0.9T、1T、1.2T、1.5T、1.7T或2T等。在一实施例中，磁场的强度可以为0.2T-2T。在另一实施例中，磁场的强度可以为0.5T-2T。在又一实施例中，磁场的强度可以为0.2T-1T。在又一实施例中，磁场的强度可以为0.8T-2T，有利于进一步提升负极的性能。
在本申请中，负极浆料中的石墨在磁场作用下发生定向取向，石墨在磁场作用下发生移动，从而得到性能优异的负极。在本申请一实施方式中，石墨的粒径D50可以为1μm-30μm，有利于离子和电子的传输以及降低与电解液之间的副反应。在本申请一实施方式中，石墨的石墨化度大于或等于60％，有利于提升负极和电池循环性能和能量密度。
在本申请一实施方式中，为提高负极的导电性能，优选地，负极浆料中还包括导电剂。在本申请另一实施方式中，负极浆料中可以包括助剂，进一步提升负极活性材料层的结构稳定性。在本申请一实施例中，助剂包括粘结剂和分散剂中的至少一种。在一实施例中，负极浆料中粘结剂的质量含量可以小于或等于2％。具体的，负极浆料中粘结剂的质量含量可以但不限于为0.1％、0.5％、0.9％、1％、1.5％、1.8％或2％等。例如，负极浆料中粘结剂的质量含量可以为0.5％-2％。在一实施例中，负极浆料中分散剂的质量含量可以小于或等于2％。具体的，负极浆料中分散剂的质量含量可以但不限于为0.1％、0.5％、0.9％、1％、1.5％、1.8％或2％等。例如，负极浆料中分散剂的质量含量可以为0.5％-2％。在本申请又一实施方式中，负极浆料中可以包括溶剂，调节负极浆料的粘度，有利于负极浆料的涂覆和负极浆料中石墨的取向。具体的，溶剂可以但不限于为水、乙醇、甲苯、二甲苯、苯甲醚、乙腈、庚烷、癸烷、乙酸乙酯、丙酸乙酯、丁酸丁酯、N-甲基吡咯烷酮、丙酮等中的至少一种。
在本申请一实施方式中，负极浆料的粘度为1500mPa·s-5000mPa·s。该负极浆料粘度适宜，有利于石墨以及导电剂的均匀分散，并且还有有利于负极浆料的涂覆和负极浆料中石墨的合理取向。具体的，负极浆料的粘度可以但不限于为1500mPa·s、2000mPa·s、2500mPa·s、3000mPa·s、3500mPa·s、4000mPa·s、4500mPa·s、5000mPa·s等。
在本申请一实施方式中，在10℃-40℃(如20℃、25℃、30℃、35℃或40℃等)条件下将负极活性材料涂覆在负极集流体的表面，有利于负极浆料的流平和稳定纯在，同时还有利于磁场对石墨诱导，促进石墨的合理取向。
在本申请一实施方式中，磁场对负极浆料的作用时间为1min-30min，从而获得优异取向的石墨以及优异性能的负极。具体的，负极浆料在磁场中的时间可以但不限于为1min、5min、10min、15min、20min、25min或30min等。可以理解的，负极浆料受到磁场作用的同时，会受到负极集流体上正电荷的作用，即电荷对负极浆料作用的时间为1min-30min。在本申请一实施例中，磁场对负极浆料的作用时间可以为1min-10min。在本申请另一实施例中，磁场对负极浆料的作用时间可以为5min-20min。在本申请一实施方式中，负极浆料在磁场中时，温度为40℃-60℃(如40℃、45℃、50℃、55℃、60℃等)，从而产生预烘干的效果，有利于负极浆料在负极集流体表面附着以及定向诱导后石墨的固定。也就是说，负极浆料经过预烘干，预烘干的温度为40℃-60℃，时间为1min-30min。
在本申请中，可以在负极集流体表面设置负极浆料后，再施加磁场，也可以设置在负极集流体一侧设置好磁场后，再进行负极浆料的设置。在本申请一实施方式中，可以将负极集流体置于传送装置中，负极集流体可以随传送装置的运动发生移动，在移动过程中将负极浆料设置在负极集流体表面，与此同时磁场设置在负极集流体一侧。在本申请中，磁场可以设置在第一表面或第二表面的一侧。在本申请一实施例中，磁场可以设置在第二表面的一侧，从而可以避免对负极浆料的影响。例如，采用磁场装置产生磁场时，磁场装置设置在第二表面的一侧可以避免接触负极浆料，更有利于负极浆料的设置。
在本申请一实施方式中，烘干的温度为40℃-200℃，时间为2min-60min。在本申请一实施方式中，烘干包括预烘干和终烘，从而有利于负极集流体与负极活性材料层的结合。在本申请一实施例中，预烘干温度小于终烘温度，如此，有利于控制磁诱导后的负极浆料中溶剂的蒸发速度和蒸发量，增加负极活性材料层与集流体之间，以及负极活性材料层中负极活性材料之间的粘结力，保证负极的结构稳定性。在本申请一实施例中，终烘的温度为60℃-200℃，时间为1min-30min，从而可以使石墨保持诱导后的取向，并且还有利于负极集流体与负极活性材料层的结合，提升负极的性能。具体的，终烘的温度可以但不限于为10℃、50℃、70℃、100℃、130℃、150℃、180℃或200℃等，终烘的时间可以但不限于为1min、5min、10min、15min、20min、25min或30min等。在一实施例中，终烘的温度为60℃-180℃，时间为5min-25min。在另一实施例中，终烘的温度为140℃-180℃，时间为5min-15min。
在本申请一实施方式中，烘干后还包括辊压。通过辊压控制负极的厚度、改善压实密度和结合力，还有利于进一步提高石墨排布的有序性。在本申请一实施方式中，辊压的压力为2t(吨)-35t，辊速为0.5m/s-2m/s。具体的，辊压的压力可以但不限于为2t、5t、9t、10t、12t、15t、20t、25t、30t或35t等，辊速可以但不限于为0.5m/s、1m/s、1.5m/s、1.8m/s或2m/s等。
在本申请一实施方式中，负极浆料还含有导电剂，在负极集流体上的负极浆料被烘干前给负极集流体带正电以使导电剂远离负极集流体一侧的导电剂的分布密度小于靠近负极集流体一侧的导电剂的分布密度。在该实施方式中采用了磁场和电场共同作用，其中磁场作用下改变负极浆料中石墨平行或近似平行于负极集流体的取向方式，使得石墨与负极集流体的夹角增加，也即石墨与集流体的垂直排列趋势增大，改善石墨的取向度，实现石墨的合理有序堆叠，产生更容易使离子和电子传输的路径，提高离子和电子的迁移速率。对负极集流体施以电场，以使负极集流体带正电，在该电场作用下，吸引导电剂朝向负极集流体的一侧移动，使得靠近负极集流体一侧的负极活性材料层的导电性能更好，从而有利于降低负极的电阻率并且在电荷作用下，石墨也会向集流体一侧移动，从而提高石墨排列的致密性，优化液相传输孔隙，增加负极活性材料层的储液量，保证电池的循环寿命和倍率性能。在磁场以及电场的作用下，导电剂和石墨在靠近负极集流体侧接触更加紧密，同时两者与负极集流体的接触面更大，负极活性材料层与负极集流体的结合力增加，提高了结合可靠性，如此有利于在电池中使用，提升电池的倍率性能和倍率性能。
在本申请中，对负极集流体施以电场的方法没有限制，只要能够使负极集流体带正电荷即可。可以理解的，本领域常用的导电剂粒径小，比较面积大，当其分散在负极浆料中是，通常会少量的负电荷。因此，当集流体到带正电时，由于静电吸引作用，导电剂会下沉，实现在集流体侧导电剂的分布密度增加。在本申请一实施方式中，可以将负极集流体与电源的正极相连，而使其带正电荷。在本申请另一实施方式中，负极集流体与直流电场相连，从而使负极集流体带正电荷。在本申请一实施例中，可以采用滚动式导电装置与负极集流体相连，从而使负极集流体带正电荷。在一具体实施例中，滚动式导电装置具有两个滚轮，在负极集流体的厚度方向上，两个滚轮夹持负极集流体，滚轮向负极集流体施加电压，从而使负极集流体带正电荷。
在本申请中，对负极集流体施以电场使负极集流体带正电荷，可通过改性的方式，使导电剂和/或石墨表面带负电，进而在静电吸引作用下导电剂和/或石墨向集流体一侧移动。
在本申请一实施方式中，对负极集流体施以电场使负极集流体带负电荷，可通过改性的方式，使导电剂和/或石墨表面带正电，进而在静电吸引作用下导电剂和/或石墨向集流体一侧移动。
在本申请一实施方式中，负极集流体的电压为0.1V-120V，如此既能够使导电剂朝向负极集流体的方向移动，同时又保证负极活性材料层中导电剂在远离负极集流体一侧的分布情况，并且还有利于增强石墨致密的排列效果，提升负极的压实密度和倍率性能。具体的，负极集流体的电压可以但不限于为0.1V、1V、5V、10V、15V、20V、25V、30V、50V、75V、90V、100V、110V、115V等。在本申请一实施例中，负极集流体的电压为5V-35V，如此进一步降低制备难度，保证制备安全性，同时有利于进一步优化负极活性材料层中石墨和导电剂的分布，进一步提升负极的电化学性能。在本申请另一实施例中，负极集流体的电压为10V-50V。在本申请又一实施例中，负极集流体的电压为10V-80V。在一实施例中，负极集流体与直流电场相连，保持电压0.1V-120V。在本申请中，在负极的制备过程中，负极集流体的电压保持稳定，更有利于负极性能的提升。
在本申请中，可以在负极集流体上的负极浆料烘干前的任一步骤中使负极集流体带正电。例如，可以在负极集流体表面设置负极浆料后，再施加电场以及使负极集流体带正电荷，也可以设置在负极集流体一侧设置好电场以及负极集流体带正电荷后，再进行负极浆料的设置。
在本申请一实施方式中，可以将负极集流体置于传送装置中，负极集流体可以随传送装置的运动发生移动，在移动过程中将负极浆料设置在负极集流体表面，与此同时负极集流体与电源连接带正电荷，并且磁场设置在负极集流体一侧。
在相同制备条件下，相较于未施加磁场或未施加磁场和电场制得的负极，本申请通过施加磁场和/或电场制得的负极的电阻率相较于普通未施加磁场的极片下降了5％-60％，极大地提高了负极和电池的倍率性能。本申请提供的制备方法操作简单、工艺条件可控、能耗低，可有效改善负极的离子和电子扩散能力、结合力、电阻率等，获得性能优异的负极。进而提高电池的充放电倍率和高倍率循环容量保持率，尤其是有利于高面密度和高压实密度的电池的电化学性能发挥，突破传统电池充放电倍率和容量瓶颈。
在本申请中，上述离子可以但不限于包括锂离子、钠离子、钾离子、镁离子和铝离子中的一种。
本申请还提供了一种电池，包括上述任一实施方式中的负极，以及正极。具有该负极的电池的充放电倍率、循环容量保持率和使用寿命优异，有利于其在用电设备中使用。电池可以但不限于为动力电池(如锂离子动力电池)、储能电池等。
在本申请一实施方式中，电池还包括电解液。在本申请一实施例中，至少部分正极浸没于电解液中，以及至少部分负极浸没于电解液中，如此保证电池正常工作。在本申请一实施例中，电解液包括锂盐和有机溶剂。具体的，锂盐可以但不限于包括六氟磷酸锂、六氟砷酸锂、高氯酸锂、六氟硼酸锂、双三氟甲烷磺酰亚胺锂、三氟甲磺酸锂、LiC(CF3SO3)2和LiN(C4F9SO2)(CF3SO3)中的至少一种；有机溶剂可以但不限于包括醚基溶剂、腈基溶剂、氰酯基溶剂、氟酯基溶剂、四唑基溶剂、氟磺酰基溶剂、氯磺酰基溶剂、硝基溶剂、碳酸酯基溶剂、二碳酸酯基溶剂、硝酸酯基溶剂、氟酰胺基溶剂、二酮基溶剂、唑基溶剂和三嗪基溶剂中的至少一种。例如，有机溶剂可以但不限于包括碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯、碳酸甲乙酯和碳酸二甲酯中的至少一种。
在本申请一实施方式中，电池还包括设置在正极和负极之间的隔膜。本申请对正极、隔膜没有特殊限制，可以但不限于采用本领域中能够作为电池正极、隔膜的物质。
本申请还提供了一种用电设备，包括上述任一实施方式中的电池。该用电设备可以实现快速充放电，满足使用需求，并且使用寿命长，产品竞争力得到提升。具体的，用电设备可以是指车辆、电子设备、储能系统等，上述电池可以是以单体电池、电池模组、电池包等形式设置在用电设备中。
下面通过具体示例对本申请技术方案的效果做进一步说明。
实施例1
在25℃条件下，将石墨(粒径D50为9.5μm)、炭黑、丁苯橡胶、羧甲基纤维素和水混合并搅拌均匀后得到负极浆料，负极浆料中石墨(人造石墨)的质量含量为96.5％，炭黑的质量含量为1.5％，丁苯橡胶的质量含量为1％，羧甲基纤维素的质量含量为1％。
将负极浆料、铜箔置于连续涂布设备中，使负极浆料涂在铜箔的第一表面，同时在铜箔上施加25V电压以使铜箔带正电荷，并在负极浆料涂布出口位置安置磁场装置，其中，磁场装置设置在与第一表面相对的第二表面的一侧，磁场强度为0.8T，磁场的磁矩方向与铜箔第一表面的夹角90°，磁场装置同时进行往复运动，往复运动的运动方向与铜箔延伸方向(即移动方向)的夹角为90°，保持磁场均匀稳定。涂布出来的负极浆料通过磁场区域的时间为10min，负极浆料在磁场中时温度为40℃。然后在140℃烘干10min后，再在压力10t、辊速为0.5m/s的条件下进行辊压，得到负极。
实施例2
与实施例1大致相同，不同之处在于铜箔施加的电压为5V。
实施例3
与实施例1大致相同，不同之处在于铜箔施加的电压为35V。
实施例4
与实施例1大致相同，不同之处在于磁场强度为0.2T。
实施例5
与实施例1大致相同，不同之处在于磁场强度为2T。
实施例6
与实施例1大致相同，不同之处在于磁场的磁矩方向与第一表面的夹角10°。
实施例7
与实施例1大致相同，不同之处在于磁场的磁矩方向与第一表面的夹角30°。
实施例8
与实施例1大致相同，不同之处在于磁场的磁矩方向与第一表面的夹角60°。
实施例9
与实施例1大致相同，不同之处在于往复运动的运动方向与铜箔延伸方向的夹角为10°。
实施例10
与实施例1大致相同，不同之处在于往复运动的运动方向与铜箔延伸方向的夹角为40°。
实施例11
与实施例1大致相同，不同之处在于磁场装置不进行往复运动，而是绕自身中心轴旋转，旋转速度为25r/min。
实施例12
与实施例1大致相同，不同之处在于磁场装置在进行往复运动的同时还进行旋转运动，旋转运动为绕自身中心轴旋转，旋转速度为50r/min。
实施例13
与实施例1大致相同，不同之处在于涂布出来的负极浆料通过磁场区域的时间为1min。
实施例14
与实施例1大致相同，不同之处在于石墨的粒径D50为19.5μm。
实施例15
与实施例1大致相同，不同之处在于磁场强度为3T，且铜箔上施加0.3V的电压。
实施例16
与实施例1大致相同，不同之处在于辊压压力在45t。
实施例17
与实施例1大致相同，不同之处在于铜箔上不施加电压。
实施例18
与实施例1大致相同，不同之处在于负极浆料由质量含量为98％的石墨、质量含量为1％的丁苯橡胶、质量含量为1％的羧甲基纤维素以及余量的水组成。
对比例1
与实施例1大致相同，不同之处在于不设置磁场装置。
对比例2
与实施例1大致相同，不同之处在于铜箔上不施加电压以及不设置磁场装置。
对比例3
与实施例1大致相同，通过调整磁场使得制得的负极活性材料层的取向值为2.5，负极集流体与负极活性材料层之间的结合力为0.24N/40mm。
性能检测
将实施例1和对比例2制得的负极进行电镜检测，其中图6为实施例1制得的负极的电镜截面图，图7为对比例2制得的负极的电镜截面图；可以看出，实施例1的负极中石墨的排列方式，趋向垂直集流体或与集流体呈角度定向堆叠，对比例2的负极中石墨的排列方式，趋向平行集流体堆叠。同时，对比例1制得的负极的电镜图与对比例2类似，负极中石墨沿趋向平行集流体堆叠。因此，本申请提供的制备方法能够改性石墨的取向方式，从而提升负极的性能。
检测上述实施例和对比例制得的负极的面密度、压实密度、取向值、结合力和电阻率，测试条件如下，结果如表1所示。
面密度测试：使用直径为1.5cm裁片器在负极(负极包括集流体及设置于集流体上的负极活性材料层)及负极集流体光箔中取样，电子秤称量重量，计算得出负极的面密度，单位g/m2。其中，负极的质量含量为m1，负极集流体的质量含量为m2，负极的面密度m0＝(m1-m2)/(π×(1.5/2)×(1.5/2))。
压实密度测试：使用万分尺测量并计算出负极活性材料层的厚度h0，其中，负极的厚度h1减去集流体的厚度h2即可获得负极活性材料层的厚度h0＝h1-h2，通过计算面密度m0与负极活性材料层的厚度h0的比值，可得出负极的压实密度，单位g/cm3。
取向值(OI值)测试：通过XRD(扫描范围5°-90°，电压1mv，扫描速度0.5°/min)，测定负极(负极包括集流体及设置于集流体上的负极活性材料层)的004峰强度和110峰强度，从而计算出负极活性材料层的OI值。
结合力(剥离力)测试：将透明胶均匀粘贴在负极的一侧并撕出一端固定在测试治具上，使用拉力计记录胶带剥离极片时力度(N)，测量长度为40mm，获得负极集流体与负极活性材料层之间的结合力。其中，测量长度指的是开始测量时透明胶从极片上剥离的长度，也即设备的测量长度。
电阻率测试：将负极裁成40mm×100mm的大小并放入极片电阻仪测试设备中进行测试，压力设置400kg，按下设备启动按钮进行自动测试，获得负极的电阻率。其中，负极包括负极集流体和负极活性材料层。
表1负极性能检测结果

将上述实施例和对比例制得的负极进行裁剪并制得面密度为230±23g/m2的负极极片，匹配对应尺寸以及面密度为500±50g/m2的正极磷酸铁锂极片(磷酸铁锂、导电炭黑、PVDF的质量比为96：2：2)；将1mol的LiPF6溶于1L有机溶剂(碳酸乙烯酯和碳酸二乙酯的体积比为1:1)中，得到电解液；在手套箱中，氩气气氛下将步骤正极、隔膜、负极交替层叠，并注入电解液，装备成软包电池，电池设计容量为1.8Ah，将制得的电池进行如下测试，结果如表2所示。
直流内阻测试：在25℃下调整上述电池的荷电状态为50％ SOC，然后分别在1.5C下充电30s，记录各个电池的压降，计算出直流阻抗DCIR。
放电比容量比率：在25℃下测试上述电池分别在0.2C、2C、5C不同倍率下的放电克容量随循环次数的变化情况，电压范围为2.0V-3.8V，计算5C倍率下的首圈放电容量与0.2C下的首圈放电容量的比值(5C/0.2C放电比率)，以及2C倍率下电池的充放电循环1000次后的电池容量与首圈0.2C放电容量的比值(2C/0.2C-1000次循环容量)，这两个比值可以作为评估电池高倍率充放电的能力。
液相扩散阻抗测试：将负极、隔膜、负极叠片制作成对称电池，在0.02Hz-200000Hz频率、电压5V的情况下，测试并分析出对称电池的交流阻抗，作为液相扩散阻抗。
表2电池性能检测结果

可以看出，对比例1未施加磁场，不能有效调整石墨的取向度，影响负极的性能；对比例2未施加磁场和电场，不能有效调整石墨的取向度，也无法调整负极活性材料层中石墨的致密排布，导致获得的负极性能不佳；虽然对比例3中负极活性材料层的取向度合适，但负极活性材料层和负极集流体之间的结合力弱，导致负极的综合性能不佳；而本申请实施例中通过施加磁场，可以改善石墨的取向度，降低负极的迂曲度，优化导电剂的分布，提升负极集流体与负极活性材料层之间的结合力，从而制得性能优异的负极，有利于提高电池的倍率性能，有助于电池的使用。通过SEM可以看出，实施例1制得的负极中，沿负极活性材料层至负极集流体的方向上，导电剂的分布密度逐渐增加，而实施例17制得的负极中，导电剂在负极活性材料中大致均匀分布，可以看出通过设置电场可以进一步改善导电剂的分布密度，进一步降低负极的电阻率，还可以进一步改善石墨的分布，提升电池的性能。相较于实施例18，实施例1的电池综合性能得到提升，表明导电剂的加入可以进一步提升负极以及电池的电化学性能。
以上所述是本申请的优选实施方式，但并不能因此而理解为对本申请范围的限制。应当指出，对于本技术领域的普通技术人员来说，在不脱离本申请原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也视为本申请的保护范围。

Claims (16)

  1. 一种负极，其特征在于，包括负极集流体(11)以及设置在所述负极集流体(11)表面的负极活性材料层(12)，所述负极活性材料层(12)包括石墨，所述负极活性材料层(12)的取向值小于或等于3，所述负极集流体(11)与所述负极活性材料层(12)之间的结合力大于或等于0.25N/40mm；
    所述取向值为负极在X射线衍射谱图中(004)特征衍射峰的峰面积与(110)特征衍射峰的峰面积的比值。
  2. 如权利要求1所述的负极，其特征在于，所述负极活性材料层(12)的取向值为0.06-3；和/或所述负极集流体(11)与所述负极活性材料层(12)之间的结合力为0.25N/40mm-2.8N/40mm。
  3. 如权利要求1或2所述的负极，其特征在于，所述负极活性材料层(12)还包括导电剂，远离所述负极集流体(11)一侧的所述导电剂的分布密度小于靠近所述负极集流体(11)一侧的所述导电剂的分布密度。
  4. 如权利要求3所述的负极，其特征在于，沿所述负极活性材料层(12)至所述负极集流体(11)的方向上，所述导电剂的分布密度逐渐增加。
  5. 如权利要求3或4所述的负极，其特征在于，所述负极活性材料层(12)中所述导电剂的质量含量占所述负极活性材料层(12)总质量含量的0.1％-6.7％。
  6. 如权利要求1-5任一项所述的负极，其特征在于，所述负极(10)的电阻率为0.1Ω·cm-2Ω·cm。
  7. 如权利要求1-6任一项所述的负极，其特征在于，所述负极活性材料层(12)中所述石墨的质量含量大于或等于所述负极活性材料层(12)总质量含量的80％；和/或
    所述石墨的粒径D50为1μm-30μm。
  8. 一种负极的制备方法，其特征在于，包括：
    提供负极集流体(11)，将含有石墨的负极浆料涂覆在所述负极集流体(11)至少一侧表面上，用磁场调整所述负极浆料中所述石墨的取向；
    经烘干后得到负极活性材料层(12)的取向值小于或等于3的负极(10)；所述负极集流体(11)与所述负极活性材料层(12)之间的结合力大于或等于0.25N/40mm。
  9. 如权利要求8所述的负极的制备方法，其特征在于，所述负极集流体(11)包括相对设置的第一表面(111)和第二表面，在所述第一表面(111)和/或所述第二表面的一侧设置磁场，所述磁场的磁矩方向与所述负极集流体的夹角为10°-90°。
  10. 如权利要求8或9所述的负极的制备方法，其特征在于，所述磁场进行往复运动和旋转运动中的至少一种，所述往复运动的运动方向与所述负极集流体(11)的延伸方向的夹角为0°-90°。
  11. 如权利要求8-10任一项所述的负极的制备方法，其特征在于，所述磁场的强度为0.1T-2T。
  12. 如权利要求8-11任一项所述的负极的制备方法，其特征在于，所述负极浆料还含有导电剂，在烘干前给所述负极集流体(11)带正电以使所述导电剂远离所述负极集流体(11)一侧的所述导电剂的分布密度小于靠近所述负极集流体(11)一侧的所述导电剂的分布密度；
    所述负极集流体(11)的电压为0.1V-120V。
  13. 如权利要求8-12任一项所述的负极的制备方法，其特征在于，所述烘干的温度为40℃-200℃，时间为2min-60min。
  14. 如权利要求8-13任一项所述的负极的制备方法，其特征在于，所述烘干后还包括辊压，所述辊压的压力为2t-35t，辊速为0.5m/s-2m/s。
  15. 一种电池，其特征在于，包括权利要求1-7任一项所述的负极(10)或权利要求8-13任一项所述的负极的制备方法制得的负极(10)，以及正极。
  16. 一种用电设备，其特征在于，包括权利要求15所述的电池。
PCT/CN2024/121232 2024-03-29 2024-09-25 负极及其制备方法、电池和用电设备 Pending WO2025200345A1 (zh)

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