WO2024066106A1 - 负极极片、电池、电池包及用电设备 - Google Patents

负极极片、电池、电池包及用电设备 Download PDF

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WO2024066106A1
WO2024066106A1 PCT/CN2022/143192 CN2022143192W WO2024066106A1 WO 2024066106 A1 WO2024066106 A1 WO 2024066106A1 CN 2022143192 W CN2022143192 W CN 2022143192W WO 2024066106 A1 WO2024066106 A1 WO 2024066106A1
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negative electrode
battery
electrode plate
material layer
value
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PCT/CN2022/143192
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English (en)
French (fr)
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林颖鑫
沈刘学
文佳琪
张敏
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厦门海辰储能科技股份有限公司
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Priority to EP22944065.6A priority Critical patent/EP4376116A1/en
Priority to IL309047A priority patent/IL309047A/en
Priority to US18/531,743 priority patent/US20240128454A1/en
Publication of WO2024066106A1 publication Critical patent/WO2024066106A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • 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
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of battery technology, and in particular to a negative electrode plate, a battery and an electrical device.
  • Hard carbon materials are a type of carbon material obtained by high-temperature pyrolysis of polymer precursors. They have large interlayer spacing and rich disordered structures, and have long charge and discharge cycle life. They are considered to be a very promising battery negative electrode material. However, hard carbon materials still have problems such as low first-cycle discharge efficiency, poor cycle stability, and poor rate characteristics. These problems hinder the development of hard carbon materials as battery negative electrode materials.
  • the present application provides a negative electrode plate, which includes two hard carbon particles with different defect values.
  • the negative electrode plate combines the excellent performance of the two hard carbon particles, so that the negative electrode plate has excellent performance, while meeting the requirements of high energy density, high first-cycle discharge efficiency and excellent rate performance of the battery.
  • the present application provides a negative electrode plate, which includes: a negative electrode current collector and a negative electrode material layer, wherein the negative electrode material layer is arranged on the surface of the negative electrode current collector, the negative electrode material layer includes a hard carbon material, and the hard carbon material includes primary particles and secondary particles, and the defect value of the primary particles is different from the defect value of the secondary particles.
  • the negative electrode plate of the embodiment of the present application includes a negative electrode current collector and a negative electrode material layer, wherein the negative electrode material layer includes a hard carbon material, wherein the hard carbon material includes primary particles and secondary particles, and the defect value of the primary particles is different from the defect value of the secondary particles.
  • Hard carbon particles with larger defect values have more active sites, which increase the storage sites of active ions, so that the battery has higher energy density and rate performance; hard carbon particles with smaller defect values have fewer active sites, which can reduce the side reactions between the negative electrode plate and the electrolyte, thereby improving the first-cycle discharge efficiency of the battery.
  • the negative electrode plate Compared with the solution of using only one hard carbon particle with the same defect value as the negative electrode material layer, the negative electrode plate provided by the embodiment of the present application improves the performance of the hard carbon material by compounding hard carbon particles with larger defect values with hard carbon particles with smaller defect values, so that the negative electrode plate has good performance, and can simultaneously meet the requirements of high energy density and high first-cycle discharge efficiency of the battery, thereby improving the kinetic performance and cycle performance of the battery.
  • the defect value of the primary particle is G1
  • the defect value of the secondary particle is G2, and 0.04 ⁇
  • the primary particle and the secondary particle have different advantages due to their different defect values.
  • the hard carbon particles with a larger defect value can improve the energy density of the battery, and the hard carbon particles with a smaller defect value can improve the first-cycle discharge efficiency of the battery, which is beneficial to the adjustment of the parameters of the overall structure of the negative electrode material layer, so that the negative electrode material layer has better performance.
  • the defect value G1 of the primary particles is in the range of 0.5 ⁇ G1 ⁇ 0.8; the defect value G2 of the secondary particles is in the range of 0.5 ⁇ G2 ⁇ 0.8.
  • the negative electrode sheet can have moderate defects, and the negative electrode material layer can have higher active sites and less side reactions with the electrolyte, thereby improving the energy density and cycle stability of the battery while improving the first-cycle discharge efficiency.
  • the value range of the number content N of primary particles in the negative electrode material layer is: 0.1 ⁇ N ⁇ 0.9.
  • the ratio of primary particles to secondary particles in the negative electrode material layer is within a reasonable range, so that the negative electrode material layer has both sufficient hard carbon particles with larger defect values and sufficient hard carbon particles with smaller defect values.
  • Particles with larger defect values can provide more active sites for the negative electrode material layer, thereby improving the energy density of the battery, and particles with smaller defect values can reduce the side reactions between the negative electrode material layer and the electrolyte, and improve the first-cycle discharge efficiency of the battery, so that the negative electrode plate can simultaneously meet the requirements of high energy density and high first-cycle discharge efficiency of the battery.
  • the numerical value SSA of the specific surface area of the hard carbon material has a value range of: 1.3 ⁇ SSA ⁇ 6.
  • the numerical value SSA of the specific surface area of the hard carbon material satisfies 1.3 ⁇ SSA ⁇ 6, the numerical value of the specific surface area of the hard carbon material is within a reasonable range, and the size of the specific surface area of the hard carbon material can not only allow the hard carbon material to have sufficient contact area with the electrolyte, which is beneficial to the transmission of active ions and improves the rate performance and energy density of the battery; at the same time, the numerical value of the specific surface area of the hard carbon material prevents the side reaction between the negative electrode plate and the electrolyte from being too excessive and affecting the first-cycle discharge efficiency of the battery.
  • the negative electrode plate has good performance and can simultaneously meet the battery's requirements for high first-cycle efficiency, high energy density and high rate performance.
  • the value range of the porosity P of the negative electrode material layer is: 0.32 ⁇ P ⁇ 0.4.
  • the porosity P of the negative electrode material layer satisfies 0.32 ⁇ P ⁇ 0.4, the porosity P of the negative electrode material layer is within a reasonable range, which improves the wettability and liquid retention capacity of the electrolyte in the negative electrode plate, reduces the transmission resistance of the active ions, is beneficial to the transmission of the active ions, and makes the negative electrode plate have a higher rate performance and prolongs the cycle life of the negative electrode plate.
  • the performance factor h of the negative electrode sheet can be further regulated, so that the primary particles and secondary particles can play their respective advantages, thereby balancing the cycle performance and charge and discharge performance of the battery, while improving the energy density and first-cycle discharge efficiency of the negative electrode sheet, and ultimately making the negative electrode sheet have better comprehensive performance, higher energy density and rate performance, and good cycle performance and stability.
  • the value range of the particle size R1 of the primary particle D50 is: 4 ⁇ m ⁇ R1 ⁇ 12 ⁇ m; the value range of the particle size R2 of the secondary particle is: 8 ⁇ m ⁇ R2 ⁇ 18 ⁇ m, wherein D50 is the particle size corresponding to when the cumulative particle size distribution percentage of the particle reaches 50%.
  • the secondary particles are conducive to achieving a tighter stacking with the primary particles, thereby improving the energy density of the battery; in addition, regulating the particle size of the primary particles and the particle size of the secondary particles is conducive to regulating the porosity of the negative electrode sheet, thereby improving the degree of electrolyte infiltration into the negative electrode sheet, increasing the transmission speed of active ions, and ultimately improving the rate performance of the battery and extending the cycle life of the battery.
  • the weight of the primary particles is M1
  • the weight of the secondary particles is M2
  • M1/M2 satisfies 0.03 ⁇ M1/M2 ⁇ 15.
  • the present application also provides a battery, which includes: an electrolyte, a positive electrode sheet, a separator and a negative electrode sheet provided by the present application, wherein the positive electrode sheet is at least partially immersed in the electrolyte; the separator is located on one side of the positive electrode sheet and is at least partially immersed in the electrolyte; the negative electrode sheet is arranged on the side of the separator away from the positive electrode sheet and is at least partially immersed in the electrolyte.
  • the battery includes the negative electrode sheet in the embodiment of the present application, and the negative electrode sheet improves its comprehensive performance by adjusting the overall structure of the negative electrode material layer, so that the battery including the negative electrode sheet has high energy density and high first cycle efficiency.
  • the present application also provides a battery pack, which includes: a box and the battery provided by the present application, wherein the multiple batteries are contained in the box, and the connection mode of the multiple batteries includes at least one of series connection and parallel connection.
  • the battery pack has the function of fixing and protecting the battery.
  • the battery pack has a high energy density and a high first cycle efficiency, and also has high cycle performance and safety performance.
  • the present application also provides an electric device, which includes: an electric device body and a battery provided in an embodiment of the present application, wherein the electric device body includes a positive electrode and a negative electrode; the positive electrode plate of the battery is used to electrically connect the positive electrode of the electric device body, and the negative electrode plate of the battery is used to electrically connect the negative electrode of the electric device body, and the battery is used to supply power to the electric device body.
  • the battery has high energy density and high first cycle efficiency, and has high cycle performance and safety performance, providing stable and safe electric energy for the electric device.
  • the above-mentioned negative electrode plate includes a negative electrode current collector and a negative electrode material layer, wherein the negative electrode material layer is a hard carbon material prepared by mixing the primary particles and the secondary particles, and the defect value of the primary particles is different from the defect value of the secondary particles.
  • Hard carbon particles with larger defect values have more active sites, which increase the storage sites of active ions, so that the battery has higher energy density and rate performance; hard carbon particles with smaller defect values have fewer active sites, which can reduce the side reactions between the negative electrode plate and the electrolyte, thereby improving the first-cycle discharge efficiency of the battery.
  • the negative electrode plate provided in the embodiment of the present application improves the performance of the hard carbon material by compounding hard carbon particles with larger defect values with hard carbon particles with smaller defect values, so that the negative electrode plate has good performance, and can simultaneously meet the requirements of high energy density and high first-cycle discharge efficiency of the battery, thereby improving the kinetic performance and cycle performance of the battery.
  • FIG1 is a structural diagram of a negative electrode sheet according to an embodiment of the present application.
  • FIG2 is a schematic cross-sectional view of a negative electrode sheet according to an embodiment of the present application along the A-A direction in FIG1 ;
  • FIG3 is a schematic diagram of the structure of a battery according to an embodiment of the present application.
  • FIG4 is a perspective schematic diagram of a battery according to an embodiment of the present application.
  • FIG5 is a schematic diagram of the structure of a battery pack according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of the structure of an electrical device according to an embodiment of the present application.
  • 1-electrical equipment 10-electrical equipment body, 30-battery pack, 20-battery, 100-negative electrode plate, 110-negative electrode collector, 130-negative electrode material layer, 200-positive electrode plate, 300-electrolyte, 400-diaphragm, 50-casing.
  • Hard carbon materials have large interlayer spacing and rich disordered structures, and their charge-discharge cycle life is long, making them a very promising battery negative electrode material.
  • hard carbon materials still have problems such as low first-cycle discharge efficiency, poor cycle stability, and poor rate characteristics, which hinder the development of hard carbon materials as battery negative electrode materials.
  • the following methods can be used to improve the shortcomings of hard carbon materials as negative electrode materials for batteries.
  • Second, the method of doping other atoms in the hard carbon material is used to increase the interlayer distance of the hard carbon material. This method improves the energy density and rate performance of the battery, but at the same time, the side reactions between the negative electrode sheet and the electrolyte increase, which reduces the first-cycle discharge efficiency of the battery.
  • an embodiment of the present application provides a negative electrode plate 100, which can be used as the negative electrode plate 100 of the battery 20.
  • the negative electrode plate 100 has excellent performance and meets the performance requirements of the battery 20 such as high energy density and high first-cycle discharge efficiency.
  • an embodiment of the present application provides a negative electrode plate 100, which includes: a negative electrode current collector 110 and a negative electrode material layer 130, wherein the negative electrode material layer 130 is arranged on the surface of the negative electrode current collector 110, and the negative electrode material layer 130 includes a hard carbon material, and the hard carbon material includes primary particles and secondary particles, and the defect value of the primary particles is different from the defect value of the secondary particles.
  • the negative electrode current collector 110 includes at least one of copper foil, stainless steel foil, copper alloy foil, carbon-coated copper foil, aluminum foil, and carbon-coated aluminum foil.
  • the negative electrode material layer 130 is arranged on the surface of the negative electrode collector 110, and the negative electrode material layer 130 is arranged on the entire surface of one surface of the negative electrode collector 110 or a part of the surface of one surface, or the negative electrode material layer 130 is arranged on the entire surface of both surfaces of the negative electrode collector 110 or a part of the surface of both surfaces.
  • the negative electrode material layer 130 includes a hard carbon material, and the hard carbon material includes primary particles and secondary particles.
  • the secondary particles refer to hard carbon materials prepared by secondary granulation using primary particles as aggregates.
  • the secondary particles have good isotropy and good liquid retention capacity, and can provide multiple channels for active ions, thereby reducing the internal resistance of the battery 20, further improving the dynamic performance of the battery 20, and improving the first-cycle discharge efficiency and rate performance of the battery 20.
  • the defect value of the primary particles is different from the defect value of the secondary particles, and the defect value of the primary particles may be greater than the defect value of the secondary particles, or may be less than the defect value of the secondary particles.
  • the secondary particles are hard carbon materials prepared by secondary granulation using primary particles as aggregates. When the defect value of the primary particles is greater than the defect value of the secondary particles, that is, the defect value of the secondary particles prepared by secondary granulation is smaller than the defect value of the primary particles, this solution is easier to control the process than secondary granulation to produce secondary particles with larger defect values, and can reduce the difficulty of production, thereby reducing the cost of production.
  • the hard carbon particles with larger defect values have more active sites, which increase the storage sites of active ions, so that the battery 20 has higher energy density and rate performance; but relatively, the more defects the hard carbon particles have, the more side reactions the hard carbon material has with the electrolyte 300, resulting in an unstable SEI film (Solid Electrolyte Interface), which reduces the first-cycle discharge efficiency of the battery 20.
  • SEI film Solid Electrolyte Interface
  • the hard carbon particles with smaller defect values have fewer active sites and a smaller specific surface area, which makes the energy density and rate performance of the battery 20 lower, but relatively, the smaller the defect value of the hard carbon particles, the less side reactions the hard carbon material has with the electrolyte 300, which is conducive to the formation of a stable SEI film at the solid-liquid interface between the negative electrode sheet 100 and the electrolyte 300, and improves the first-cycle discharge efficiency of the battery 20. Therefore, by setting hard carbon particles with different defect values, the advantages of the two hard carbon particles can be combined to improve the performance of the negative electrode sheet 100, thereby improving the performance of the battery 20.
  • the negative electrode plate 100 of the embodiment of the present application includes a negative electrode current collector 110 and a negative electrode material layer 130, wherein the negative electrode material layer 130 includes a hard carbon material, wherein the hard carbon material includes primary particles and secondary particles, and the defect value of the primary particles is different from the defect value of the secondary particles.
  • the negative electrode plate 100 provided in the embodiment of the present application improves the performance of the hard carbon material by compounding hard carbon particles with larger defect values with hard carbon particles with smaller defect values, so that the negative electrode plate 100 has good performance, and can simultaneously meet the performance requirements of the battery 20 such as high energy density and high first-cycle discharge efficiency, thereby improving the dynamic performance and cycle performance of the battery 20.
  • the secondary particles include a main body and a coating layer, and the coating layer is wrapped around the surface of the main body.
  • the coating layer of the secondary particles is conducive to reducing the defect value of the hard carbon particles, so that the side reaction between the negative electrode material layer 130 and the electrolyte 300 is reduced, which is conducive to the formation of a stable SEI film at the interface between the negative electrode plate 100 and the electrolyte 300, and improves the first cycle discharge efficiency of the battery 20; in addition, during the battery charging and discharging process, the coating layer can withstand the expansion of the hard carbon material, improve the safety performance of the negative electrode plate 100, and help improve the cycle performance of the battery 20.
  • the defect value of the primary particles is G1
  • the defect value of the secondary particles is G2, and 0.04 ⁇
  • the defect value of the primary particle is G1, and G1 can be calculated by the intensity ID1 of the D peak and the intensity IG1 of the G peak in the Raman spectrum.
  • the intensity ID1 of the D peak in the Raman spectrum of the primary particle is larger, and the defect value G1 of the primary particle is larger.
  • the defect value of the secondary particle is G2, and G2 can be calculated by the intensity ID2 of the D peak and the intensity IG2 of the G peak in the Raman spectrum.
  • the intensity ID2 of the D peak in the Raman spectrum of the secondary particle is larger, and the defect value G2 of the secondary particle is larger.
  • the primary particles and the secondary particles have different advantages due to their different defect values.
  • the hard carbon particles with larger defect values can improve the energy density of the battery 20, and the hard carbon particles with smaller defect values can improve the first-week discharge efficiency of the battery 20.
  • By controlling the difference between the defect value of the primary particles and the defect value of the secondary particles it is beneficial to adjust the parameters of the overall structure of the negative electrode material layer 130, so that the negative electrode material layer 130 has better performance.
  • the difference between the defect value G1 of the primary particle and the defect value G2 of the secondary particle that is, the value of
  • the defect value G1 of the primary particles is in the range of 0.5 ⁇ G1 ⁇ 0.8.
  • the defect value G1 of the primary particle When the defect value G1 of the primary particle is in the range of 0.5 ⁇ G1 ⁇ 0.8, the primary particle has enough active sites, which is beneficial to the storage of active ions, so that the battery 20 has a higher energy density and rate performance; and the defect value of the primary particle is not too much to cause the first cycle discharge efficiency of the battery 20 to be greatly reduced. Therefore, when 0.5 ⁇ G1 ⁇ 0.8, the defect value of the primary particle is beneficial to balance the kinetic performance and cycle performance of the negative electrode material layer 130, so that the negative electrode plate 100 can simultaneously meet the requirements of the battery 20 for high energy density and high first cycle efficiency.
  • the defect value G1 of the primary particle When the defect value G1 of the primary particle is greater than 0.8, the side reaction between the negative electrode material layer 130 and the electrolyte 300 will be greatly increased, making the SEI film generated at the interface between the negative electrode plate 100 and the electrolyte 300 unstable, reducing the first cycle discharge efficiency of the battery 20.
  • the defect value G1 of the primary particle is less than 0.5, the defect value of the primary particle is small, and the active sites thereof are fewer, which reduces the storage sites of active ions and will reduce the energy density and rate performance of the battery 20 .
  • the defect value G1 of the primary particles may be, but is not limited to, 0.51, 0.54, 0.60, 0.65, 0.76 or 0.8, etc.
  • the primary particles have an appropriate amount of active sites, which can not only meet the storage of active ions, but also reduce the side reactions between the negative electrode material layer 130 and the electrolyte 300, so that the negative electrode material layer 130 has better performance, while improving the energy density and rate performance of the battery 20 and improving the first-cycle discharge efficiency of the battery 20.
  • the defect value G2 of the secondary particles is in the range of 0.5 ⁇ G2 ⁇ 00.8.
  • the defect value G2 of the secondary particles is in the range of 0.5 ⁇ G2 ⁇ 0.8, the secondary particles have enough active sites, which is conducive to the storage of active ions, so that the battery 20 has a higher energy density and rate performance; and the defect value of the secondary particles is not too much to cause the first cycle discharge efficiency of the battery 20 to be greatly reduced. Therefore, when 0.5 ⁇ G2 ⁇ 0.8, the defect value of the secondary particles is conducive to balancing the kinetic performance and cycle performance of the hard carbon material, so that the negative electrode plate 100 can simultaneously meet the requirements of the battery 20 for high energy density and high first cycle efficiency.
  • the defect value G2 of the secondary particles When the defect value G2 of the secondary particles is greater than 0.8, the side reaction of the hard carbon material and the electrolyte 300 will be greatly increased, making the SEI film generated at the interface between the negative electrode plate 100 and the electrolyte 300 unstable, reducing the first cycle discharge efficiency of the battery 20.
  • the defect value G2 of the secondary particles is less than 0.5, the defect value of the secondary particles is small, and the active sites are less, which reduces the storage of active ions and reduces the energy density and rate performance of the battery 20.
  • the defect value G2 of the secondary particles may be, but is not limited to, 0.5, 0.51, 0.54, 0.60, 0.65, 0.76 or 0.79, etc.
  • the secondary particles have an appropriate amount of active sites, which can not only meet the storage of active ions, but also reduce the side reactions between the negative electrode material layer 130 and the electrolyte 300, so that the negative electrode material layer 130 has better performance, thereby improving the first-cycle discharge efficiency of the battery 20 while improving the energy density and rate performance of the battery 20.
  • the number content N of the primary particles in the negative electrode material layer 130 is in the range of 0.1 ⁇ N ⁇ 0.9.
  • the ratio of the primary particles to the secondary particles in the negative electrode material layer 130 is within a reasonable range, so that the negative electrode material layer 130 has both sufficient hard carbon particles with large defect values and sufficient hard carbon particles with small defect values.
  • the particles with large defect values can provide more active sites for the negative electrode material layer 130, thereby improving the energy density of the battery 20, and the particles with small defect values can reduce the side reactions between the negative electrode material layer 130 and the electrolyte 300, and improve the first cycle discharge efficiency of the battery 20, so that the negative electrode plate 100 can simultaneously meet the requirements of high energy density and high first cycle discharge efficiency of the battery 20.
  • the value of the number content N of the primary particles in the negative electrode material layer 130 is greater than 0.9, the value of the number n1 of the primary particles in the negative electrode material layer 130 is much greater than the number n2 of the secondary particles. If the defect value of the primary particles is greater than the defect value of the secondary particles, the side reactions of the hard carbon material and the electrolyte 300 increase, resulting in instability of the SEI film generated at the interface between the negative electrode plate 100 and the electrolyte 300, thereby reducing the first-week discharge efficiency of the battery 20; if the defect value of the primary particles is less than the defect value of the secondary particles, the hard carbon material has fewer active sites, reducing the storage sites of active ions, thereby reducing the energy density of the battery 20 containing the negative electrode plate 100.
  • the value of the number content N of the primary particles in the negative electrode material layer 130 is less than 0.1, the value of the number n1 of the primary particles in the negative electrode material layer 130 is much smaller than the number n2 of the secondary particles. If the defect value of the primary particles is greater than the defect value of the secondary particles, the hard carbon material has fewer active sites, which reduces the storage sites of active ions, thereby reducing the energy density of the battery 20 containing the negative electrode plate 100.
  • the defect value of the primary particles is less than the defect value of the secondary particles, the side reactions of the hard carbon material and the electrolyte 300 increase, resulting in an unstable SEI film formed at the interface between the negative electrode plate 100 and the electrolyte 300, thereby reducing the first-cycle discharge efficiency of the battery 20;
  • the value of the quantity content N of the primary particles in the negative electrode material layer 130 may be, but is not limited to, 0.1, 0.2, 0.4, 0.55, 0.6, 0.7, 0.8, 0.9, etc.
  • the specific surface area SSA of the hard carbon material is in the range of 1.3 ⁇ SSA ⁇ 6.
  • the numerical value SSA of the specific surface area of the hard carbon material can be that the numerical value SSA of the specific surface area of the hard carbon material after the primary particles and the secondary particles are mixed.
  • the hard carbon material is in full contact with the electrolyte 300, the transmission rate of active ions is improved, and at the same time, the side reaction between the hard carbon material and the electrolyte 300 is reduced, thereby making the battery 20 have better rate performance and higher first-cycle discharge efficiency.
  • the numerical value SSA of the specific surface area of the hard carbon material is obtained by testing with a specific surface area analyzer.
  • the value of the specific surface area of the hard carbon material is within a reasonable range.
  • the value of the specific surface area of the hard carbon material can not only ensure that the hard carbon material has sufficient contact area with the electrolyte 300, which is beneficial to the transmission of active ions and improves the rate performance and energy density of the battery 20; at the same time, the value of the specific surface area of the hard carbon material can prevent the side reactions between the negative electrode plate 100 and the electrolyte 300 from being excessive and affecting the first-cycle discharge efficiency of the battery 20.
  • the negative electrode plate 100 has good performance and can simultaneously meet the requirements of the battery 20 for high first-cycle efficiency, high energy density and high rate performance.
  • the contact area between the hard carbon material and the electrolyte 300 is too large, which easily causes an increase in the side reactions between the hard carbon material and the electrolyte 300, resulting in an unstable SEI film generated at the interface between the negative electrode plate 100 and the electrolyte 300, thereby reducing the first-cycle discharge efficiency of the battery 20; at the same time, the SSA value of the specific surface area of the hard carbon material is too large, which is not conducive to the processing and production of the negative electrode plate 100, and increases the production cost.
  • the contact area between the hard carbon material and the electrolyte 300 is too small, which reduces the transmission rate of active ions, thereby reducing the rate performance and energy density of the battery 20.
  • the value of the specific surface area SSA of the hard carbon material may be, but is not limited to, 1.3, 2.3, 3.2, 4.5, 5, 5.6, 6, etc.
  • the porosity P of the negative electrode material layer 130 is in the range of 0.32 ⁇ P ⁇ 0.4.
  • the porosity P of the negative electrode material layer 130 is obtained by a pressure pump method (also known as a "mercury intrusion method"). Among them, since the average particle size of the primary particles is different from the average particle size of the secondary particles, during the preparation process of the negative electrode plate 100, the porosity P of the negative electrode material layer 130 can be regulated by rolling pressure.
  • the porosity P of the negative electrode material layer 130 When the porosity P of the negative electrode material layer 130 satisfies 0.32 ⁇ P ⁇ 0.4, the porosity P of the negative electrode material layer 130 is within a reasonable range, which improves the wetting performance and liquid retention capacity of the electrolyte 300 in the negative electrode plate 100, reduces the transmission resistance of active ions, is beneficial to the transmission of active ions, and makes the negative electrode plate 100 have a higher rate performance and prolongs the cycle life of the negative electrode plate 100.
  • the value of the porosity P of the negative electrode material layer 130 is greater than 0.4, the side reaction between the negative electrode material layer 130 and the electrolyte 300 is aggravated, which reduces the first cycle discharge efficiency of the battery 20 and reduces the cycle performance of the battery 20.
  • the wetting performance and liquid retention capacity of the electrolyte 300 in the negative electrode plate 100 are poor, which increases the transmission resistance of active ions, makes the rate performance of the negative electrode plate 100 low, and reduces the cycle life of the battery 20.
  • the porosity P of the negative electrode material layer 130 may be, but is not limited to, 0.32, 0.35, 0.36, 0.37, 0.39, 0.4, and the like.
  • the particle size R1 of the primary particle D50 has a value range of 4 ⁇ m ⁇ R1 ⁇ 12 ⁇ m, wherein D50 is the particle size corresponding to when the cumulative particle size distribution percentage reaches 50%.
  • a particle group is usually composed of a large number of particles of different sizes, which are divided into several levels according to the particle size.
  • the relative content of particles in each level is called differential distribution; the total content of particles smaller than a certain level is called cumulative distribution.
  • the particle size R1 of the primary particle D50 is the equivalent diameter of the primary particle when the cumulative distribution is 50% in the particle size distribution curve.
  • the number of primary particles with a particle size greater than R1 accounts for 50% of the number of all primary particles
  • the number of primary particles with a particle size less than R1 accounts for 50% of the number of all primary particles.
  • the primary particle is conducive to achieving a relatively compact stacking with the secondary particles, thereby improving the energy density of the battery 20; in addition, it is also conducive to the regulation of the porosity of the negative electrode plate 100, thereby improving the degree of infiltration of the electrolyte 300 into the negative electrode plate 100, improving the transmission speed of active ions, and ultimately improving the rate performance of the battery 20 and extending the cycle life of the battery 20.
  • the particle size of the primary particle is too large, and it is difficult to achieve a compact stacking with the secondary particles, thereby reducing the energy density of the battery 20; furthermore, in the process of regulating the porosity of the negative electrode plate 100, the primary particle with a large particle size is difficult to fill the gaps between the secondary particles, so that the porosity of the negative electrode plate 100 is too large, and the side reaction between the negative electrode material layer 130 and the electrolyte 300 is aggravated, which reduces the first cycle discharge efficiency of the battery 20 and reduces the cycle performance of the battery 20.
  • the particle size of the primary particle is too small and it is easy to fill the particle size between the secondary particles, so that the porosity of the negative electrode plate 100 is too small, resulting in poor wetting performance and liquid retention capacity of the electrolyte 300 in the negative electrode plate 100, increasing the active ion transmission resistance, making the rate performance of the negative electrode plate 100 low, and reducing the cycle life of the battery 20.
  • the particle size R1 of the primary particles D50 may be, but is not limited to, 4 ⁇ m, 4.1 ⁇ m, 4.3 ⁇ m, 5 ⁇ m, 7 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, etc.
  • the value range of the particle size R2 of the secondary particles D50 is: 8 ⁇ m ⁇ R2 ⁇ 18 ⁇ m, wherein D50 is the particle size corresponding to when the cumulative particle size distribution percentage of the particles reaches 50%.
  • the particle size R2 of the secondary particle D50 is the equivalent diameter of the secondary particle when the cumulative distribution is 50% in the particle size distribution curve.
  • the number of secondary particles with a particle size greater than R2 accounts for 50% of the number of all secondary particles
  • the number of secondary particles with a particle size less than R2 accounts for 50% of the number of all secondary particles.
  • the secondary particle When the particle size of the secondary particle D50 satisfies 8 ⁇ m ⁇ R2 ⁇ 18 ⁇ m, the secondary particle is conducive to achieving a relatively compact stacking with the primary particle, thereby improving the energy density of the battery 20; in addition, it is also conducive to the regulation of the porosity of the negative electrode plate 100, thereby improving the degree of infiltration of the electrolyte 300 into the negative electrode plate 100, improving the transmission speed of active ions, and ultimately improving the rate performance of the battery 20 and extending the cycle life of the battery 20.
  • the particle size of the secondary particle is too large, and it is difficult to achieve a compact stacking with the primary particle, thereby reducing the energy density of the battery 20; furthermore, in the process of regulating the porosity of the negative electrode plate 100, the particle size of the secondary particle is too large, and the primary particle is difficult to fill the gap between the secondary particles, so that the porosity of the negative electrode plate 100 is too large, and the side reaction between the negative electrode material layer 130 and the electrolyte 300 is aggravated, which reduces the first cycle discharge efficiency of the battery 20 and reduces the cycle performance of the battery 20.
  • the particle size R2 of the secondary particle D50 is less than 8 ⁇ m, the particle size of the secondary particle is too small, and the difference in size with the particle size of the primary particle is too small, making it difficult to achieve compact stacking with the primary particle, thereby reducing the energy density of the battery 20 .
  • the particle size R2 of the secondary particles D50 may be, but is not limited to, 8 ⁇ m, 10.5 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 17 ⁇ m, 18 ⁇ m, etc.
  • the weight of the primary particles is M1
  • the weight of the secondary particles is M2
  • M1/M2 satisfies 0.03 ⁇ M1/M2 ⁇ 15.
  • the value of the quantity content N of the primary particles in the negative electrode material layer 130 can be regulated. It should be noted that the value of the average particle size R1 of the primary particles and the value of the average particle size R2 of the secondary particles will also affect the value of M1/M2. In other words, if the same N value is taken, the value of M1/M2 will be different due to the difference between the average particle size R1 of the primary particles and the average particle size R2 of the secondary particles.
  • the ratio M1/M2 of the weight M1 of the primary particles to the weight M2 of the secondary particles satisfies 0.03 ⁇ M1/M2 ⁇ 15
  • the weight M1 of the primary particles is too large, which will lead to the value of the number content N of the primary particles in the negative electrode material layer 130 being too large, so that the number of primary particles in the negative electrode material layer 130 is too large and the number of secondary particles is too small.
  • the negative electrode material layer 130 cannot combine the advantages of two particles with different particle sizes and different defect values, and the performance of the negative electrode plate 100 is poor and cannot simultaneously meet the requirements of the high energy density and high first-cycle discharge efficiency of the battery 20.
  • the ratio M1/M2 of the weight M1 of the primary particles to the weight M2 of the secondary particles is less than 0.03, the mass M1 of the primary particles is too small, which will lead to the value of the number content N of the primary particles in the negative electrode material layer 130 being too small, so that the number of primary particles in the negative electrode material layer 130 is too small and the number of secondary particles is too large, and finally the negative electrode plate 100 cannot simultaneously meet the requirements of the high energy density and high first-cycle discharge efficiency of the battery 20.
  • the ratio of the weight M1 of the primary particles to the weight M2 of the secondary particles may be, but is not limited to, 0.03, 0.1, 0.5, 1, 2.6, 3.98, 5.00, 8.29, 10.50, 13.60, 15, and the like.
  • the performance factor h of the negative electrode plate 100 represents the comprehensive performance of the negative electrode plate 100, such as energy density, first cycle discharge efficiency, rate performance and other dynamic performance and cycle performance.
  • the performance factor h of the negative electrode plate 100 can be further regulated, so that the primary particles and the secondary particles can play their respective advantages, thereby balancing the cycle performance and charge and discharge performance of the battery 20, while improving the overall performance of the negative electrode plate 100, so that the battery 20 containing the negative electrode plate 100 has higher energy density and rate performance, and has good cycle performance and stability.
  • the value of the performance factor h of the negative electrode plate 100 satisfies 0.2 ⁇ h ⁇ 1.8, the energy density and first-cycle discharge efficiency of the battery 20 containing the negative electrode plate 100 are high, and the cycle performance and power performance of the battery 20 are good.
  • the value of the performance factor h of the negative electrode plate 100 is greater than 1.8, the comprehensive performance of the negative electrode plate 100 is poor, and the negative electrode plate 100 cannot simultaneously meet the requirements of the battery 20 for high energy density, high first-cycle discharge efficiency and high rate performance; when the value of the performance factor h of the negative electrode plate 100 is less than 0.2, the negative electrode plate 100 cannot meet the requirements of the battery 20 for high energy density, high first-cycle discharge efficiency and high rate performance, and the comprehensive performance of the negative electrode plate 100 is poor.
  • the value of the performance factor h of the negative electrode plate 100 may be, but is not limited to, 0.2, 0.6, 0.75, 0.9, 1.2, 1.5, 1.6, 1.7, 1.8, etc.
  • the comprehensive performance of the negative electrode plate 100 is better, so that the battery 20 containing the negative electrode plate 100 not only has a higher energy density and a high first-cycle discharge efficiency, but also has higher cycle performance and safety performance.
  • the negative electrode plate 100 further includes a first binder and a first conductive agent.
  • the first binder is used to bond and maintain the negative electrode material layer 130, enhance the electronic contact between the negative electrode material layer 130 and the negative electrode current collector 110, and better stabilize the structure of the negative electrode plate 100.
  • the first binder includes one or more of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyacrylate, carboxymethyl cellulose (CMC), sodium alginate, etc.
  • SBR styrene-butadiene rubber
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PVA polyvinyl alcohol
  • PAN polyacrylonitrile
  • PAA polyacrylic acid
  • CMC carboxymethyl cellulose
  • sodium alginate etc.
  • the first conductive agent enables the negative electrode plate 100 to have good charge and discharge performance, reduces the contact resistance of the negative electrode plate 100, accelerates the movement rate of electrons, and thus improves the charge and discharge efficiency of the negative electrode plate 100.
  • the first conductive agent includes one or more of acetylene black, conductive carbon black, carbon nanotubes, carbon fibers, graphene, and the like.
  • the embodiment of the present application also provides a battery 20, which includes a positive electrode plate 200, an electrolyte 300, a negative electrode plate 100 described in the embodiment of the present application, and a separator 400.
  • the positive electrode plate 200 is at least partially immersed in the electrolyte 300;
  • the separator 400 is located on one side of the positive electrode plate 200 and is at least partially immersed in the electrolyte 300;
  • the negative electrode plate 100 is arranged on the side of the separator 400 away from the positive electrode plate 200 and is at least partially immersed in the electrolyte 300.
  • the positive electrode plate 200 includes a positive electrode current collector and a positive electrode material layer, wherein the positive electrode material layer is disposed on the surface of the positive electrode current collector, and the positive electrode material layer includes a positive electrode active material, a second binder, and a second conductive agent.
  • the positive electrode active material includes one or more of transition metal oxides, polyanionic compounds, organic polymers, and Prussian blue materials.
  • the second binder is used to bond and maintain the positive electrode material layer, enhance the electronic contact between the positive electrode material layer and the positive electrode current collector, and better stabilize the structure of the positive electrode plate 200.
  • the second binder includes one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polyacrylic acid (PAA), etc.
  • the second conductive agent enables the positive electrode plate 200 to have good charge and discharge performance, reduces the contact resistance of the positive electrode plate 200, accelerates the movement rate of electrons, and thus improves the charge and discharge efficiency of the positive electrode plate 200.
  • the second conductive agent includes one or more of acetylene black, conductive carbon black, carbon nanotubes, carbon fibers, graphene, and the like.
  • the electrolyte 300 includes an electrolyte salt (such as lithium hexafluorophosphate, sodium hexafluorophosphate, etc.) and an organic solvent, wherein the specific types and compositions of the electrolyte salt and the organic solvent are conventional choices in the field of battery 20 and can be selected according to actual needs.
  • an electrolyte salt such as lithium hexafluorophosphate, sodium hexafluorophosphate, etc.
  • organic solvent wherein the specific types and compositions of the electrolyte salt and the organic solvent are conventional choices in the field of battery 20 and can be selected according to actual needs.
  • the separator 400 is any separator 400 material in the existing battery 20 field, and the separator 400 includes one or more of polypropylene (PP), polyethylene (PE), and ceramic separator 400.
  • PP polypropylene
  • PE polyethylene
  • ceramic separator 400 includes one or more of ceramic separator 400.
  • the battery 20 includes the negative electrode plate 100 in the embodiment of the present application.
  • the negative electrode plate 100 improves its comprehensive performance by adjusting the overall structure of the negative electrode material layer 130, so that the battery 20 including the negative electrode plate 100 has high energy density and high first-cycle efficiency.
  • the primary particles are calcined at 1000°C to 1300°C in an inert gas (e.g., argon) atmosphere, and then a bonding asphalt is added and mixed, and secondary granulation is performed in a reactor to obtain secondary particles.
  • Coating asphalt is added to the secondary particles, stirred, and calcined and carbonized at a temperature less than 1000°C under the protection of an inert gas (e.g., argon) atmosphere to perform carbon coating, and then screening and demagnetization steps are performed to obtain carbon-coated secondary particles.
  • an inert gas e.g., argon
  • the hard carbon material, the first conductive agent (conductive carbon black), and the first binder (sodium hydroxymethyl cellulose + styrene butadiene rubber, CMC + SBR) are mixed in a mass ratio of 95.5:1.5:2, the mixed powder is placed in a vacuum mixer, deionized water is added and stirred to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the opposite side surfaces of the negative electrode collector 110 to form a negative electrode material layer 130, the negative electrode collector 110 coated with the negative electrode slurry is transferred to an oven for drying, and then rolled and cut to obtain the negative electrode sheet 100.
  • the positive electrode active material Na 3 V 2 (PO4) 3
  • the second conductive agent conductive carbon black
  • the second binder polyvinylidene fluoride, PVDF
  • NMP N-methylpyrrolidone
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed at a volume ratio of 1:1:1 to obtain a mixed solvent, and dry sodium salt NaPF 6 was added thereto to prepare an electrolyte solution 300 with a concentration of 1 mol/L.
  • the positive electrode sheet 200, negative electrode sheet 100 and polypropylene separator 400 prepared above are stacked in order so that the separator 400 is between the positive and negative electrode sheets 100, and then wound to obtain a bare battery cell, which is then placed in an aluminum-plastic film soft package, dried and injected with electrolyte 300, and the battery 20 is obtained after vacuum packaging, standing, forming, shaping and other processes.
  • the preparation of the negative electrode plate, the preparation of the positive electrode plate, the preparation of the electrolyte and the preparation of the battery in Comparative Examples 1 and 2 are the same as the corresponding steps in Examples 1 to 7.
  • the parameters of the hard carbon material and the parameters of the negative electrode material layer 130 of Comparative Examples 1 and 2 are set to be compared with Examples 1 to 7.
  • the specific information is shown in Table 1.
  • Preparation of secondary particles primary particles are calcined at 1000°C to 1300°C in an inert gas (e.g., argon) atmosphere, then bonding asphalt is added and mixed, and secondary granulation is performed in a reactor to obtain secondary particles, coating asphalt is added to the secondary particles, stirred, and calcined and carbonized at a temperature less than 1000°C under the protection of an inert gas (e.g., argon) atmosphere for carbon coating, and then sieving and demagnetizing to obtain carbon-coated secondary particles.
  • the hard carbon material in this comparative example includes only secondary particles, not primary particles.
  • the hard carbon material, the first conductive agent (conductive carbon black), and the first binder (sodium hydroxymethyl cellulose + styrene butadiene rubber, CMC + SBR) are mixed in a mass ratio of 95.5:1.5:2, the mixed powder is placed in a vacuum mixer, deionized water is added and stirred to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the opposite side surfaces of the negative electrode collector 110 to form a negative electrode material layer 130, the negative electrode collector 110 coated with the negative electrode slurry is transferred to an oven for drying, and then rolled and cut to obtain the negative electrode sheet 100.
  • the hard carbon material in this comparative example only includes primary particles and does not include secondary particles.
  • the hard carbon material, the first conductive agent (conductive carbon black), and the first binder (sodium hydroxymethyl cellulose + styrene butadiene rubber, CMC + SBR) are mixed in a mass ratio of 95.5:1.5:2, the mixed powder is placed in a vacuum mixer, deionized water is added and stirred to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the opposite side surfaces of the negative electrode collector 110 to form a negative electrode material layer 130, the negative electrode collector 110 coated with the negative electrode slurry is transferred to an oven for drying, and then rolled and cut to obtain the negative electrode sheet 100.
  • Defect value test Raman spectroscopy was used to measure the defect value G1 of the primary particles and the defect value G2 of the secondary particles in Examples 1 to 7 and the defect value G1 of the primary particles and the defect value G2 of the secondary particles in Comparative Examples 1 to 4, respectively.
  • Porosity test The pore size distribution and porosity of the solid material are determined by the mercury injection method and gas adsorption method according to GB/T 21650.1-2008/ISO 15901-1,2005.
  • the porosity of the negative electrode sheet 100 in Examples 1 to 7 and Comparative Examples 1 to 4 is calculated based on the pore size distribution and porosity of the material.
  • Part 1 Mercury injection data.
  • Table 1 Structural parameters of negative electrode sheets 100 of Examples 1 to 7 and Comparative Examples 1 to 4
  • the area of sodium precipitation on the surface of the negative electrode sheet 100 is less than 2%, it is considered that there is no sodium precipitation, if the area of sodium precipitation on the surface of the negative electrode sheet 100 is less than 5%, it is considered that there is slight sodium precipitation, if the area of sodium precipitation on the surface of the negative electrode is 5% to 40%, it is considered that there is moderate sodium precipitation, and if the area of sodium precipitation on the surface of the negative electrode is greater than 40%, it is considered that there is severe sodium precipitation.
  • the values of the performance factor h of the negative electrode plate 100 in Examples 1 to 7 are 0.72, 0.94, 0.46, 1.26, 1.53, 0.23 and 0.26 respectively, satisfying 0.2 ⁇ h ⁇ 1.8.
  • the negative electrode plate 100 has good comprehensive performance, and the battery 20 containing the negative electrode plate 100 has high energy density and first-week discharge efficiency, and the cycle performance and power performance of the battery 20 are good.
  • the value of the performance factor h of the negative electrode plate 100 in Examples 1 to 4 satisfies 0.3 ⁇ h ⁇ 1.4.
  • the negative electrode plate 100 not only has good comprehensive performance, but also does not precipitate sodium during the test process, and has high safety performance.
  • the performance of the negative electrode plate 100 in Example 2 is the best, with the highest energy density and first-week discharge efficiency, and the highest capacity retention rate after 2000 cycles. It can be seen that when the performance factor h of the negative electrode plate 100 satisfies 0.2 ⁇ h ⁇ 1.8, the comprehensive performance of the corresponding negative electrode plate 100 first gradually improves and then gradually decreases.
  • the value of the performance factor h of the negative electrode plate 100 in Comparative Example 1, Comparative Example 3 and Comparative Example 4 is less than 0.2, and the comprehensive performance of the corresponding negative electrode plate 100 is poor, so that the energy density and the first-week discharge efficiency of the battery 20 containing the negative electrode plate 100 are low, and the cycle performance and safety performance of the battery 20 are poor.
  • the value of the performance factor h of the negative electrode plate 100 in Comparative Example 2 is greater than 1.8, and the comprehensive performance of the corresponding negative electrode plate 100 is also poor, so that the energy density and the first-week discharge efficiency of the battery 20 containing the negative electrode plate 100 are low, and the cycle performance and safety performance of the battery 20 are poor.
  • in Examples 1 to 4 all satisfy 0.04 ⁇
  • is less than 0.04.
  • the difference between the defect value of the primary particles and the defect value of the secondary particles is too small. It is difficult for the primary particles and the secondary particles to exert their respective advantages, resulting in poor overall performance of the negative electrode material layer 130.
  • the battery 20 corresponding to Example 7 has a lower energy density and first-week discharge efficiency.
  • the specific surface area values SSA of the hard carbon materials described in Example 2 and Example 6 are 4.2 and 1.2 respectively.
  • the value of the specific surface area SSA of the hard carbon material described in Example 2 is moderate, so that the hard carbon material has sufficient contact area with the electrolyte 300, but does not have too many side reactions with the electrolyte 300 to reduce the first-cycle discharge efficiency, so that the battery 20 corresponding to Example 2 has a higher energy density and a higher first-cycle discharge efficiency.
  • the value of the specific surface area SSA of the hard carbon material described in Example 6 is less than 1.3, the specific surface area of the hard carbon material is small, the surface active sites are reduced, and the charge and discharge performance of the battery 20 is slightly poor, which reduces the energy density of the battery 20, and there is a slight sodium precipitation phenomenon during the test process, which reduces the capacity retention rate and safety performance of the sodium ion battery 20 during the cycle process.
  • the values of the number content N of the primary particles in the negative electrode material layer 130 of Comparative Example 3, Example 6, Example 1, Example 5 and Comparative Example 4 are 0, 0.3, 0.5, 0.7 and 1 respectively.
  • the negative electrode material layer 130 of comparative example 3 is a single secondary particle, the defect value of the secondary particle is small, and the active sites are small, which reduces the storage sites of active ions, making the energy density of the battery 20 low.
  • the value of the number content N of the primary particles in the negative electrode material layer 130 in Example 6, Example 1 and Example 5 all satisfy 0.1 ⁇ N ⁇ 0.9, among which the negative electrode material layer corresponding to Example 1 has the best performance.
  • the primary particles in the negative electrode material layer can provide more active sites for the negative electrode material layer 130 and the side reactions with the electrolyte 300 are not too much to affect the performance of the negative electrode material layer, and the energy density of the battery is the highest.
  • the negative electrode material layer 130 in comparative example 4 is a single primary particle, and the defect value of the primary particle is large, resulting in a large defect value of the hard carbon material, so that the side reactions of the negative electrode plate 100 and the electrolyte 300 are too much, the consumption of active ions increases, and the first-week discharge efficiency is reduced, so the energy density of the battery in comparative example 4 is also very low.
  • the porosity P of the negative electrode material layer 130 in Example 5 and Example 2 is 0.27 and 0.36 respectively.
  • the porosity P of the negative electrode material layer 130 in Example 5 is less than 0.32, the wetting performance and liquid retention capacity of the electrolyte 300 in the negative electrode plate 100 are slightly poor, the transmission resistance of the active ions is increased, the charge and discharge performance of the battery 20 is slightly poor, and there is a slight sodium precipitation phenomenon during the test.
  • the porosity P of the negative electrode material layer 130 in Example 2 is moderate, which can improve the wetting performance and liquid retention capacity of the electrolyte 300 in the negative electrode plate 100, reduce the transmission resistance of the active ions, and make the negative electrode plate 100 have better kinetic performance, and make the negative electrode plate 100
  • the side reaction with the electrolyte 300 during the formation and circulation process is not too much to reduce the cycle life of the battery 20, so that the battery in Example 2 has high energy density, high first-cycle discharge efficiency and better cycle performance.
  • the present application also provides a battery pack 30.
  • the battery pack 30 includes a box 50 and batteries provided in the present application.
  • the multiple batteries are contained in the box 50.
  • the multiple batteries are connected in series or in parallel.
  • the battery pack 30 has the function of fixing and protecting the battery 20.
  • the battery pack 30 has a high energy density and a high first cycle efficiency, as well as high cycle performance and safety performance.
  • the embodiment of the present application further provides an electric device 1, the electric device 1 comprising: an electric device body 10, the electric device body 10 comprising a positive electrode and a negative electrode; and a battery 20 provided in the embodiment of the present application, the positive electrode plate 200 of the battery 20 is used to electrically connect the positive electrode of the electric device body, the negative electrode plate 100 of the battery 20 is used to electrically connect the negative electrode of the electric device body 10, and the battery 30 is used to supply power to the electric device body 10.
  • the battery 20 has high energy density and high first cycle efficiency, and has high cycle performance and safety performance, providing stable and safe electric energy for the electric device 1.
  • the electrical device 1 of the present application may be, but is not limited to, electronic devices such as mobile phones, tablet computers, laptop computers, desktop computers, smart bracelets, smart watches, and e-readers.
  • the electrical device described in this embodiment is only one form of electrical device used by the battery, and should not be understood as a limitation on the electrical device provided in this application, nor should it be understood as a limitation on the batteries provided in each embodiment of this application.

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Abstract

本发明提供了一种负极极片、电池、电池包及用电设备。所述负极极片包括：负极集流体以及负极材料层，所述负极材料层设置于所述负极集流体的表面，所述负极材料层包括硬碳材料，所述硬碳材料包括一次颗粒和二次颗粒，所述一次颗粒的缺陷值与所述二次颗粒的缺陷值不同。相较于只应用一种具有相同缺陷值的硬碳颗粒作为负极材料层的方案，本申请的负极极片包括缺陷值不同的两种硬碳颗粒，该负极极片综合了两种硬碳颗粒的优异性能，使得负极极片具有优异的性能，同时满足电池高能量密度、高首周放电效率及优异倍率性能等要求。

Description

负极极片、电池、电池包及用电设备 技术领域
本申请涉及电池技术领域，尤其涉及一种负极极片、电池及用电设备。
背景技术
硬碳材料是一类以高分子聚合物为前驱体经高温热解得到的碳材料，它具有较大的层间间距和丰富的无序结构，且其充放电循环寿命长，被认为是一种十分有前景的电池负极材料。但是，硬碳材料目前仍存在首周放电效率低、循环稳定性差和倍率特性不佳等问题，这些问题阻碍了硬碳材料作为电池负极材料的发展。
目前常采用在硬碳材料中掺杂其他原子、利用石墨化程度较高的软碳覆盖硬碳中的一些开孔及设计含有许多缺陷的硬碳材料等方法来改善硬碳材料作为电池负极材料的不足之处，但是这些方案难以同时满足电池对高能量密度和高首周放电效率等电化学性能的要求。
发明内容
鉴于此，本申请提供一种负极极片，所述负极极片包括缺陷值不同的两种硬碳颗粒，该负极极片综合了两种硬碳颗粒的优异性能，使得负极极片具有优异的性能，同时满足电池高能量密度、高首周放电效率及优异倍率性能等要求。
本申请提供了一种负极极片，其包括：负极集流体以及负极材料层，所述负极材料层设置于所述负极集流体的表面，所述负极材料层包括硬碳材料，所述硬碳材料包括一次颗粒和二次颗粒，所述一次颗粒的缺陷值与所述二次颗粒的缺陷值不同。
本申请的实施例的负极极片包括负极集流体及负极材料层，所述负极材料层包括硬碳材料，所述硬碳材料包括一次颗粒和二次颗粒，且所述一次颗粒的缺陷值与所述二次颗粒的缺陷值不同。缺陷值较大的硬碳颗粒具有较多的活性位点，增加了活性离子的储存位点，使电池具有较高的能量密度和倍率性能；缺陷值较小的硬碳颗粒具有较少的活性位点，可以降低负极极片与电解液的副反应，从而提高电池的首周放电效率。相较于单独应用一种缺陷值相同的硬碳颗粒作为负极材料层的方案，本申请的实施例提供的负极极片通过将缺陷值较大的硬碳颗粒与缺陷值较小的硬碳颗粒复配，改善了硬碳材料的性能，使得负极极片具有良好的性能，且能同时满足电池高能量密度和高首周放电效率等性能的要求，提高了电池的动力学性能和循环性能。
进一步地，所述一次颗粒的缺陷值为G1，所述二次颗粒的缺陷值为G2，且0.04≤|G1-G2|≤0.2。当所述一次颗粒的缺陷值G1与所述二次颗粒的缺陷值G2满足0.04≤|G1-G2|≤0.2时，所述一次颗粒与所述二次颗粒因缺陷值不同而具有不同的优势，缺陷值较大的硬碳颗粒可以提高电池的能量密度，缺陷值较小的硬碳颗粒可以提高电池的首周放电效率，有利于负极材料层整体结构的参数的调试，使得负极材料层具有较好的性能。
进一步地，所述一次颗粒的缺陷值G1的范围值为：0.5≤G1≤0.8；所述二次颗粒的缺陷值G2的范围值为：0.5≤G2≤0.8。将所述一次颗粒的缺陷值G1的值及所述二次颗粒的缺陷值G2的值调控在合理的范围内，可使所述负极极片具有适中的缺陷，进而使所述负极材料层具有较高的活性位点，且与电解液的副反应较少，在提高首周放电效率的同时提高电池的能量密度和循环稳定性。
进一步地，在所述负极材料层中一次颗粒的数量含量N的取值范围为：0.1≤N≤0.9。当所述负极材料层中一次颗粒的数量含量N满足0.1≤N≤0.9时，负极材料层中一次颗粒与二次颗粒的比值在一个合理的范围内，使得所述负极材料层中既具有足够多的缺陷值较大的硬碳颗粒，又具有足够的缺陷值较小的硬碳颗粒。缺陷值较大的颗粒能为所述负极材料层提供较多的活性位点，从而提高电池的能量密度，缺陷值较小的颗粒能减少所述负极材料层与电解液的副反应，提高电池的首周放电效率，从而使所述负极极片同时满足电池高能量密度和高首周放电效率的要求。
进一步地，所述硬碳材料的比表面积的数值SSA的取值范围为：1.3≤SSA≤6。当所述硬碳材料的比表面积的数值SSA满足1.3≤SSA≤6时，所述硬碳材料的比表面积的数值在一个合理的范围内，所述硬碳材料的比表面积的大小既能使得硬碳材料与电解液有足够的接触面积，有利于活性离子的传输，提高电池的倍率性能和能量密度；同时所述硬碳材料的比表面积的数值使得所述负极极片与电解液的副反应不至于过多而影响电池的首周放电效率，所述负极极片具有较好的性能，能同时满足电池对高首周效率、高能量密度和高倍率性能的要求。
进一步地，所述负极材料层的孔隙率P的取值范围为：0.32≤P≤0.4。当所述负极材料层的孔隙率P满足0.32≤P≤0.4时，所述负极材料层的孔隙率P在一个合理的范围内，提高了电解液在负极极片中的浸润性能和保液能力，降低了活性离子的传输阻力，有利于活性离子的传输，使得所述负极极片具有较高的倍率性能，延长了所述负极极片的循环寿命。
进一步地，所述负极极片的性能因子h满足关系式：h＝[N×G1+(1-N)×G2]×SSA×P；其中，0.2≤h≤1.8，N为所述负极材料层中一次颗粒的数量含量，G1为所述一次颗粒的缺陷值，G2为所述二次颗粒的缺陷值，SSA为所述硬碳材料的比表面积的数值，P为所述负极材料层的孔隙率。通过控制负极材料层整体的结构参数和负极极片的结构参数，可以进一步调控所述负极极片的性能因子h，使得所述一次颗粒与二次颗粒可以发挥各自的优势，从而平衡电池的循环性能和充放电性能，同时提升负极极片的能量密度及首周放电效率，最终使得该负极极片的综合性能较好，具有较高的能量密度和倍率性能，同时具备良好的循环性能和稳定性。
进一步地，所述一次颗粒D50的粒径R1的取值范围为：4μm≤R1≤12μm；所述二次颗粒的粒径R2的取值范围为：8μm≤R2≤18μm，其中，D50为颗粒的累积粒度分布百分数达到50％时所对应的粒径。通过合理调控所述一次颗粒的平均粒径与所述二次颗粒的粒径，使得所述二次颗粒有利于与一次颗粒实现较紧实的堆积，从而提升电池的能量密度；此外，调控所述一次颗粒的粒径与所述二次颗粒的粒径，有利于所述负极极片的孔隙率的调控，从而提高电解液对负极极片的浸润程度，提高活性离子的传输速度，最终提高电池的倍率性能和延长电池的循环寿命。
进一步地，所述一次颗粒的重量为M1，所述二次颗粒的重量为M2，则M1/M2满足0.03≤M1/M2≤15。当所述一次颗粒的重量M1与所述二次颗粒的重量M2的比值M1/M2满足0.03≤M1/M2≤15时，有利于控制所述负极材料层中一次颗粒的数量含量N的值，使之满足0.1≤N≤0.9，使得所述负极材料层中一次颗粒的数量含量在合理的范围内，使所述负极材料层既有较多的活性位点，又不至于与电解液有过多的副反应，使含有该负极极片的电池具有高能量密度及高首周放电效率。
本申请还提供了一种电池，其包括：电解液、正极极片、隔膜及本申请提供的负极极片，所述正极极片至少部分浸渍于所述电解液中；所述隔膜位于所述正极极片的一侧，且至少部分浸渍于所述电解液中；所述负极极片设置于所述隔膜背离所述正极极片的一侧且至少部分浸渍于所述电解液中。所述电池包括本申请实施例中的负极极片，所述负极极片通过对负极 材料层整体结构的调试提高了自身的综合性能，使得包括所述负极极片的电池同时具备高能量密度及高首周效率等。
本申请还提供了一种电池包，所述电池包包括：箱体以及本申请提供的电池，所述多个电池收容于所述箱体内，所述多个电池的连接方式包括串联、并联中的至少一种。所述电池包对电池具有固定和保护的作用，此外，所述电池包具有较高的能量密度及较高的首周效率，同时具有较高的循环性能和安全性能。
本申请还提供了一种用电设备，其包括：用电设备本体及本申请实施例提供的电池，所述用电设备本体包括设备正极及设备负极；所述电池的正极极片用于电连接用电设备本体的设备正极，电池的负极极片用于电连接所述用电设备本体的设备负极，所述电池用于为所述用电设备本体进行供电。所述电池具有高能量密度及高首周效率，且具有较高的循环性能和安全性能，为用电设备提供了稳定和安全的电能。
上述负极极片，包括负极集流体以及负极材料层，所述负极材料层为所述一次颗粒和二次颗粒混合制备得到的硬碳材料，且所述一次颗粒的缺陷值与所述二次颗粒的缺陷值不同。缺陷值较大的硬碳颗粒具有较多的活性位点，增加了活性离子的储存位点，使电池具有较高的能量密度和倍率性能；缺陷值较小的硬碳颗粒具有较少的活性位点，可以降低负极极片与电解液的副反应，从而提高电池的首周放电效率。相较于单独应用一种缺陷值相同的硬碳颗粒作为负极材料层的方案，本申请的实施例提供的负极极片通过将缺陷值较大的硬碳颗粒与缺陷值较小的硬碳颗粒复配，改善了硬碳材料的性能，使得负极极片具有良好的性能，且能同时满足电池高能量密度和高首周放电效率等性能的要求，提高了电池的动力学性能和循环性能。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对实施方式中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图是本申请一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为本申请一实施例的负极极片的结构实体图；
图2为本申请一实施例的负极极片沿图1中A-A方向的剖视结构示意图；
图3为本申请一实施例的电池的结构示意图；
图4为本申请一实施例的电池的透视示意图；
图5为本申请一实施例的电池包的结构示意图；
图6为本申请一实施例的用电设备的结构示意图。
附图标记说明：
1-用电设备，10-用电设备本体，30-电池包，20-电池，100-负极极片，110-负极集流体，130-负极材料层，200-正极极片，300-电解液，400-隔膜，50-箱体。
具体实施方式
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付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。
本申请的说明书和权利要求书及上述附图中的术语“第一”、“第二”等是用于区别不同对 象，而不是用于描述特定顺序。此外，术语“包括”和“具有”以及它们任何变形，意图在于覆盖不排他的包含。例如包含了一系列步骤或单元的过程、方法、系统、产品或设备没有限定于已列出的步骤或单元，而是可选地还包括没有列出的步骤或单元，或可选地还包括对于这些过程、方法、产品或设备固有的其他步骤或单元。
在本文中提及“实施例”或“实施方式”意味着，结合实施例或实施方式描述的特定特征、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。
硬碳材料具有较大的层间间距和丰富的无序结构，且其充放电循环寿命长，是一种十分有前景的电池负极材料。但是，硬碳材料目前仍存在首周放电效率低、循环稳定性差和倍率特性不佳等问题，这些问题阻碍了硬碳材料作为电池负极材料的发展。
可以采用以下方法来改进硬碳材料作为电池负极材料的不足之处。其一，利用石墨化程度较高的软碳覆盖硬碳中的一些开孔，该方法能减少负极极片与电解液的副反应，提高首周放电效率，但同时减少了硬碳材料的比表面积，减少了活性位点，降低了电池的能量密度。其二，采用在硬碳材料中掺杂其他原子的方法来增大硬碳材料的层间距离，该方法提高了电池的能量密度和倍率性能，但与此同时，负极极片与电解液的副反应增多，降低了电池的首周放电效率。其三，设计含有较多缺陷的硬碳材料，此方法虽能增加储存活性离子的活性位点，提高电池的能量密度和倍率性能，但也会导致负极极片与电解液的副反应增多，降低电池的首周放电效率。以上这些方案，虽能改善硬碳材料作为电池负极材料的不足之处，但是这些方案难以同时满足电池对高能量密度和高首周放电效率等性能的要求。
鉴于此，本申请实施例提供了一种负极极片100，其可以作为电池20的负极极片100，所述负极极片100具有优异的性能，同时满足电池20高能量密度、高首周放电效率等性能的要求。
请参见图1和图2，本申请实施例提供了一种负极极片100，其包括：负极集流体110以及负极材料层130，所述负极材料层130设置于所述负极集流体110的表面，所述负极材料层130包括硬碳材料，所述硬碳材料包括一次颗粒和二次颗粒，所述一次颗粒的缺陷值与所述二次颗粒的缺陷值不同。
可选地，所述负极集流体110包括铜箔、不锈钢箔、铜合金箔、涂炭铜箔、铝箔、涂碳铝箔中的至少一种。
可以理解地，所述负极材料层130设置于所述负极集流体110的表面可以为，所述负极材料层130设置于所述负极集流体110的一个表面的整个表面或一个表面的部分表面，还可以为，所述负极材料层130设置于所述负极集流体110的两个表面的整个表面或两个表面上的部分表面。
所述负极材料层130包括硬碳材料，所述硬碳材料包括一次颗粒和二次颗粒。在本申请实施例中，二次颗粒指的是由一次颗粒为骨料经二次造粒制备得到的硬碳材料，所述二次颗粒各向同性好，保液能力好，能为活性离子提供多个通道，降低了电池20的内阻，能进一步提高电池20的动力学性能，提高电池20的首周放电效率和倍率性能。
可以理解地，所述一次颗粒的缺陷值与所述二次颗粒的缺陷值不同，可以为，所述一次颗粒的缺陷值大于所述二次颗粒的缺陷值，还可以为，所述一次颗粒的缺陷值小于所述二次颗粒的缺陷值。所述二次颗粒是由一次颗粒为骨料经二次造粒制备得到的硬碳材料，当所述一次颗粒的缺陷值大于所述二次颗粒的缺陷值不同，即由二次造粒制备得到的二次颗粒的缺 陷值比一次颗粒的缺陷值更小，此方案相较于二次造粒出缺陷值更大的二次颗粒，更加易于控制工艺过程，且能降低生产的难度，进而降低生产的成本。
缺陷值较大的硬碳颗粒具有较多的活性位点，增加了活性离子的储存位点，使电池20具有较高的能量密度和倍率性能；但相对地，硬碳颗粒的缺陷较多，则所述硬碳材料与电解液300的副反应增多，导致生成的SEI膜(Solid Electrolyte Interface,固体电解质界面膜)不稳定，降低了电池20的首周放电效率。而缺陷值较小的硬碳颗粒具有较少的活性位点和较小的比表面积，使得电池20能量密度和倍率性能偏低，但相对地，硬碳颗粒的缺陷值越小，所述硬碳材料与电解液300的副反应较少，有利于在负极极片100与电解液300的固液相界面生成稳定的SEI膜，提高电池20的首周放电效率。因此，通过设置具有不同缺陷值的硬碳颗粒，可以综合两种硬碳颗粒的优点，提高所述负极极片100的性能，从而提高电池20的性能。
本申请的实施例的负极极片100包括负极集流体110及负极材料层130，所述负极材料层130包括硬碳材料，所述硬碳材料包括一次颗粒和二次颗粒，且所述一次颗粒的缺陷值与所述二次颗粒的缺陷值不同。相较于单独应用一种缺陷值相同的硬碳颗粒作为负极材料层130的方案，本申请的实施例提供的负极极片100通过将缺陷值较大的硬碳颗粒与缺陷值较小的硬碳颗粒复配，改善了硬碳材料的性能，使得负极极片100具有良好的性能，且能同时满足电池20高能量密度和高首周放电效率等性能的要求，提高了电池20的动力学性能和循环性能。
在一些实施例中，所述二次颗粒包括本体部及包覆层，所述包覆层包裹于所述本体部的表面。二次颗粒的包覆层有利于减少硬碳颗粒的缺陷值，使得所述负极材料层130与电解液300之间的副反应减少，有利于在负极极片100与电解液300的界面生成稳定的SEI膜，提高电池20的首周放电效率；此外，在电池充放电过程中，包覆层可以耐受硬碳材料的膨胀，提高了负极极片100的安全性能，有利于提高电池20的循环性能。
在一些实施例中，所述一次颗粒的缺陷值为G1，所述二次颗粒的缺陷值为G2，且0.04≤|G1-G2|≤0.2。
可选地，所述一次颗粒的缺陷值为G1，G1可以通过拉曼光谱中的D峰的强度ID1与G峰的强度IG1进行计算。所述一次颗粒的缺陷值G1为G1＝ID1/(ID1+IG1)，其中，D峰为波长为1350cm -1处的峰，D峰代表的是碳原子晶格的缺陷；G峰为波长为1585cm -1处的峰，G峰代表的是碳原子sp 2杂化的面内伸缩振动。当一次颗粒的缺陷较大时，则所述一次颗粒的拉曼光谱中D峰的强度ID1较大，则一次颗粒的缺陷值G1较大。
可选地，所述二次颗粒的缺陷值为G2，G2可以通过拉曼光谱中的D峰的强度ID2与G峰的强度IG2进行计算。所述二次颗粒的缺陷值G2为G2＝ID2/(ID2+IG2)，其中，D峰为波长为1350cm -1处的峰，D峰代表的是碳原子晶格的缺陷；G峰为波长为1585cm -1处的峰，G峰代表的是碳原子sp 2杂化的面内伸缩振动。当二次颗粒的缺陷较大时，则所述二次颗粒的拉曼光谱中D峰的强度ID2较大，则二次颗粒的缺陷值G2较大。
当所述一次颗粒的缺陷值G1与所述二次颗粒的缺陷值G2满足0.04≤|G1-G2|≤0.2时，所述一次颗粒与所述二次颗粒因缺陷值不同而具有不同的优势，缺陷值较大的硬碳颗粒可以提高电池20的能量密度，缺陷值较小的硬碳颗粒可以提高电池20的首周放电效率，通过控制一次颗粒的缺陷值与二次颗粒的缺陷值的差值，有利于负极材料层130整体结构的参数的调试，使得负极材料层130具有较好的性能。若|G1-G2|＞0.2，则所述一次颗粒的缺陷值与所述二次颗粒的缺陷值的差值太大，不利于负极材料层130整体结构的参数的调试，会影响调试数据的精确性和准确性；若|G1-G2|＜0.04，则所述一次颗粒的缺陷值与所述二次颗粒的缺陷 值的差值太小，所述一次颗粒与二次颗粒难以发挥各自的优势，使得所述负极材料层130的整体性能不佳，不能达到同时满足电池20高能量密度和高首周效率的要求。
具体地，所述一次颗粒的缺陷值G1与所述二次颗粒的缺陷值G2的差值，即|G1-G2|的值可以为但不限于为0.04、0.06、0.10、0.13、0.16、0.18、0.19及0.2等。
在一些实施例中，所述一次颗粒的缺陷值G1的范围值为：0.5≤G1≤0.8。
当所述一次颗粒的缺陷值G1的范围为：0.5≤G1≤0.8时，一次颗粒具有足够多的活性位点，有利于活性离子的储存，使电池20具有较高的能量密度和倍率性能；并且一次颗粒的缺陷值不至于过多而导致电池20的首周放电效率大大降低，因此，当0.5≤G1≤0.8时，所述一次颗粒的缺陷值有利于平衡所述负极材料层130的动力学性能和循环性能，使得负极极片100同时满足电池20对高能量密度和高首周效率的要求。当所述一次颗粒的缺陷值G1的值大于0.8时，将大大增多所述负极材料层130与电解液300的副反应，使得在负极极片100与电解液300的界面生成的SEI膜不稳定，降低了电池20的首周放电效率。当所述一次颗粒的缺陷值G1的值小于0.5时，所述一次颗粒的缺陷值较小，其活性位点较少，降低了活性离子的储存位点，将降低所述电池20的能量密度和倍率性能。
具体地，所述一次颗粒的缺陷值G1的值可以为但不限于为0.51、0.54、0.60、0.65、0.76或0.8等。
优选地，当0.55≤G1≤0.75时，所述一次颗粒具有适量的活性位点，既能满足活性离子的储存，又能降低所述负极材料层130与电解液300的副反应，使得负极材料层130具有较好的性能，在提高电池20的能量密度和倍率性能的同时提高电池20的首周放电效率。
在一些实施例中，所述二次颗粒的缺陷值G2的范围值为：0.5≤G2≤00.8。
当所述二次颗粒的缺陷值G2的范围值为：0.5≤G2≤0.8，二次颗粒具有足够多的活性位点，有利于活性离子的储存，使电池20具有较高的能量密度和倍率性能；并且二次颗粒的缺陷值不至于过多而导致电池20的首周放电效率大大降低，因此，当0.5≤G2≤0.8时，所述二次颗粒的缺陷值有利于平衡所述硬碳材料的动力学性能和循环性能，使得负极极片100同时满足电池20对高能量密度和高首周效率的要求。当所述二次颗粒的缺陷值G2的值大于0.8时，将大大增多所述硬碳材料与电解液300的副反应，使得在负极极片100与电解液300的界面生成的SEI膜不稳定，降低了电池20的首周放电效率。当所述二次颗粒的缺陷值G2的值小于0.5时，所述二次颗粒的缺陷值较小，其活性位点较少，降低了活性离子的储存，将降低所述电池20的能量密度和倍率性能。
具体地，所述二次颗粒的缺陷值G2的值可以为但不限于为0.5、0.51、0.54、0.60、0.65、0.76或0.79等。
优选地，当0.55≤G2≤0.75时，所述二次颗粒具有适量的活性位点，既能满足活性离子的储存，又能降低所述负极材料层130与电解液300的副反应，使得负极材料层130具有较好的性能，在提高电池20的能量密度和倍率性能的同时提高电池20的首周放电效率。
在一些实施例中，所述负极材料层130中一次颗粒的数量含量N的取值范围为：0.1≤N≤0.9。
需要说明的是，所述负极材料层130中一次颗粒的数量含量为N指负极材料层130中所述一次颗粒的数量n1与所述一次颗粒的数量n1和所述二次颗粒的数量n2的比值，即所述一次颗粒的数量含量N＝n1/(n1+n2)。可以理解地，所述二次颗粒的数量含量为(1-N)。通过控制所述一次颗粒的数量含量N，可以调控硬碳材料混合体系中一次颗粒的数量，进而实现对所述负极极片100性能的调控。在本申请一实施例中，所述一次颗粒的数量含量N的测试 方法为：在所述硬碳材料的扫描电镜图中，统计所述一次颗粒的数量n1及所述二次颗粒的数量n2，通过关系式N＝n1/(n1+n2)得出所述负极材料层130中一次颗粒的数量含量。
当所述负极材料层130中一次颗粒的数量含量N满足0.1≤N≤0.9时，负极材料层130中一次颗粒与二次颗粒的比值在一个合理的范围内，使得所述负极材料层130中既具有足够多的缺陷值较大的硬碳颗粒，又具有足够多的缺陷值较小的硬碳颗粒。缺陷值较大的颗粒能为所述负极材料层130提供较多的活性位点，从而提高电池20的能量密度，缺陷值较小的颗粒能减少所述负极材料层130与电解液300的副反应，提高电池20的首周放电效率，从而使所述负极极片100同时满足电池20高能量密度和高首周放电效率的要求。当所述负极材料层130中一次颗粒的数量含量N的值大于0.9时，所述负极材料层130中一次颗粒的数量n1的值远远大于二次颗粒的数量n2，若所述一次颗粒的缺陷值大于所述二次颗粒的缺陷值，则所述硬碳材料与电解液300的副反应增多，导致负极极片100与电解液300的界面生成的SEI膜不稳定，降低电池20的首周放电效率；若所述一次颗粒的缺陷值小于所述二次颗粒的缺陷值，则所述硬碳材料的活性位点较少，减少了活性离子的储存位点，从而降低了含有该负极极片100的电池20的能量密度。当所述负极材料层130中一次颗粒的数量含量N的值小于0.1时，所述负极材料层130中一次颗粒的数量n1的值远远小于二次颗粒的数量n2，若所述一次颗粒的缺陷值大于所述二次颗粒的缺陷值，则所述硬碳材料的活性位点较少，减少了活性离子的储存位点，从而降低了含有该负极极片100的电池20的能量密度。若所述一次颗粒的缺陷值小于所述二次颗粒的缺陷值，则所述硬碳材料与电解液300的副反应增多，导致负极极片100与电解液300的界面生成的SEI膜不稳定，降低电池20的首周放电效率；
具体地，所述负极材料层130中一次颗粒的数量含量N的值可以为但不限于为0.1、0.2、0.4、0.55、0.6、0.7、0.8、0.9等。
在一些实施例中，所述硬碳材料的比表面积的数值SSA的取值范围为：1.3≤SSA≤6。
可以理解地，所述硬碳材料的比表面积的数值SSA，可以为，所述一次颗粒和二次颗粒混合后的硬碳材料的比表面积的数值为SSA。通过合理调控所述硬碳材料的比表面积的数值SSA，使得所述硬碳材料与电解液300充分接触，提高活性离子的传输速率，同时使得所述硬碳材料与电解液300的副反应较少，继而使得电池20具有较好的倍率性能和较高的首周放电效率。在本申请一实施例中，所述硬碳材料的比表面积的数值SSA是通过比表面积分析仪测试得到的。
当所述硬碳材料的比表面积的数值SSA满足1.3≤SSA≤6时，所述硬碳材料的比表面积的数值在一个合理的范围内，所述硬碳材料的比表面积的数值既能使得硬碳材料与电解液300有足够的接触面积，有利于活性离子的传输，提高电池20的倍率性能和能量密度；同时所述硬碳材料的比表面积的数值又能使得负极极片100与电解液300的副反应不至于过多而影响电池20的首周放电效率，所述负极极片100具有较好的性能，能同时满足电池20对高首周效率、高能量密度和高倍率性能的要求。当所述硬碳材料的比表面积的数值SSA大于6时，所述硬碳材料与电解液300的接触面积过大，容易引起硬碳材料与电解液300的副反应增多，导致负极极片100与电解液300的界面生成的SEI膜不稳定，降低电池20的首周放电效率；同时，所述硬碳材料的比表面积的数值过大，不利于所述负极极片100的加工及制作，增加了生产的成本。当所述硬碳材料的比表面积的数值SSA小于1.3时，所述硬碳材料与电解液300的接触面积过小，降低了活性离子的传输速率，使得电池20的倍率性能和能量密度降低。
具体地，所述硬碳材料的比表面积的数值SSA的值可以为但不限于为1.3、2.3、3.2、4.5、5、5.6及6等。
在一些实施例中，所述负极材料层130的孔隙率P的取值范围为：0.32≤P≤0.4。
通过合理调控所述负极材料层130的孔隙率P，有利于提升电解液300在负极极片100中的浸润效果，降低活性离子的传输阻力，从而提高电池20的循环性能和动力学性能。在本申请一实施例中，所述负极材料层130的孔隙率P通过压泵法(又称“水银压入法”)测试得到。其中，由于所述一次颗粒的平均粒径与所述二次颗粒的平均粒径大小不一，在负极极片100的制备过程中，可通过辊压压力来调控所述负极材料层130的孔隙率P。
当所述负极材料层130的孔隙率P满足0.32≤P≤0.4时，所述负极材料层130的孔隙率P在一个合理的范围内，提高了电解液300在负极极片100中的浸润性能和保液能力，降低了活性离子的传输阻力，有利于活性离子的传输，使得所述负极极片100具有较高的倍率性能，延长了所述负极极片100的循环寿命。当所述负极材料层130的孔隙率P的值大于0.4时，所述负极材料层130与电解液300发生的副反应加剧，降低了电池20的首周放电效率且降低了电池20的循环性能。当所述负极材料层130的孔隙率P的值小于0.32时，电解液300在所述负极极片100中的浸润性能和保液能力较差，增加了活性离子的传输阻力，使得所述负极极片100的倍率性能较低，且降低了电池20的循环寿命。
具体地，所述负极材料层130的孔隙率P的值可以为但不限于为0.32、0.35、0.36、0.37、0.39及0.4等。
在一些实施例中，所述一次颗粒D50的粒径R1的取值范围为：4μm≤R1≤12μm，其中，D50为颗粒的累积粒度分布百分数达到50％时所对应的粒径。
颗粒群体通常由大量大小不同的颗粒组成，按颗粒的粒径大小分为若干级数，表示出每一个级数颗粒的相对含量，称为微分分布；表现出小于某一级数颗粒的总含量，称为累积分布。
可以理解地，所述一次颗粒D50的粒径R1即为在粒度分布曲线中累积分布为50％时的一次颗粒的等效直径。换言之，在所述负极材料层130中，粒径大于R1的一次颗粒的数量占所有一次颗粒的数量的比例为50％，粒径小于R1的一次颗粒的数量占所有一次颗粒的数量的比例为50％。
当所述一次颗粒D50的粒径R1足4μm≤R1≤12μm时，所述一次颗粒有利于与二次颗粒实现较紧实的堆积，从而提升电池20的能量密度；此外，也有利于所述负极极片100的孔隙率的调控，从而提高电解液300对负极极片100的浸润程度，提高活性离子的传输速度，最终提高电池20的倍率性能和延长电池20的循环寿命。当所述一次颗粒D50的粒径R1的值大于12μm时，所述一次颗粒的粒径过大，难以与二次颗粒实现紧实的堆积，从而降低了电池20的能量密度；再者，在负极极片100的孔隙率的调控过程中，粒径太大的一次颗粒难以填充二次颗粒之间的空隙，使得负极极片100的孔隙率过大，所述负极材料层130与电解液300发生的副反应加剧，降低了电池20的首周放电效率且降低了电池20的循环性能。当所述一次颗粒D50的粒径R1的值小于3μm时，所述一次颗粒的粒径过小，容易填满二次颗粒之间的粒径，从而使得所述负极极片100的孔隙率过小，导致电解液300在所述负极极片100中的浸润性能和保液能力较差，增加了活性离子传输阻力，使得所述负极极片100的倍率性能较低，且降低了电池20的循环寿命。
具体地，所述一次颗粒D50的粒径R1的值可以为但不限于为4μm、4.1μm、4.3μm、5μm、7μm、8μm、10μm及12μm等。
在一些实施例中，所述二次颗粒D50的粒径R2的取值范围为：8μm≤R2≤18μm，其中，D50为颗粒的累积粒度分布百分数达到50％时所对应的粒径。
可以理解地，所述二次颗粒D50的粒径R2即为在粒度分布曲线中累积分布为50％时的二次颗粒的等效直径。换言之，在所述负极材料层130中，粒径大于R2的二次颗粒的数量占所有二次颗粒的数量的比例为50％，粒径小于R2的二次颗粒的数量占所有二次颗粒的数量的比例为50％。
当所述二次颗粒D50的粒径满足8μm≤R2≤18μm时，所述二次颗粒有利于与一次颗粒实现较紧实的堆积，从而提升电池20的能量密度；此外，也有利于所述负极极片100的孔隙率的调控，从而提高电解液300对负极极片100的浸润程度，提高活性离子的传输速度，最终提高电池20的倍率性能和延长电池20的循环寿命。当所述二次颗粒D50的粒径R2的值大于18μm时，所述二次颗粒的粒径过大，难以与一次颗粒实现紧实的堆积，从而降低了电池20的能量密度；再者，在负极极片100的孔隙率的调控过程中，二次颗粒的粒径太大，一次颗粒难以填充二次颗粒之间的空隙，使得负极极片100的孔隙率过大，所述负极材料层130与电解液300发生的副反应加剧，降低了电池20的首周放电效率且降低了电池20的循环性能。当所述二次颗粒D50的粒径R2的值小于8μm时，所述二次颗粒的粒径过小，与一次颗粒的粒径的大小差值太小，难以与一次颗粒实现紧实的堆积，从而降低了电池20的能量密度。
具体地，所述二次颗粒D50的粒径R2的值可以为但不限于为8μm、10.5μm、13μm、14μm、15μm、17μm及18μm等。
在一些实施例中，所述一次颗粒的重量为M1，所述二次颗粒的重量为M2，则M1/M2满足0.03≤M1/M2≤15。
调控所述一次颗粒的重量M1与所述二次颗粒的重量M2的比值M1/M2可以实现调控所述负极材料层130中一次颗粒的数量含量N的取值。需要说明的是，所述一次颗粒的平均粒径R1的取值与所述二次颗粒的平均粒径R2的取值也会对M1/M2的取值有影响。换言之，若取同一个N值，则M1/M2的值会因为所述一次颗粒的平均粒径R1与所述二次颗粒的平均粒径R2的不同而有所不同。
当所述一次颗粒的重量M1与所述二次颗粒的重量M2的比值M1/M2满足0.03≤M1/M2≤15时，有利于控制所述负极材料层130中一次颗粒的数量含量N的值，使之满足0.1≤N≤0.9，使得所述负极材料层130中一次颗粒与二次颗粒的比值及一次颗粒的粒径与二次颗粒的粒径在一个合理的范围内，使所述负极材料层130既有较多的活性位点，又不至于与电解液300有过多的副反应，使含有该负极极片100的电池20具有高能量密度及高首周放电效率。当所述一次颗粒的重量M1与所述二次颗粒的重量M2的比值M1/M2大于15时，所述一次颗粒的重量M1太大，则会导致所述负极材料层130中一次颗粒的数量含量N的值过大，使得负极材料层130中一次颗粒的数量太多，二次颗粒的数量太少，所述负极材料层130无法结合两种粒径大小不同、缺陷值不同的颗粒的优点，所述负极极片100的性能较差，无法同时满足电池20高能量密度和高首周放电效率等性能的要求。当所述一次颗粒的重量M1与所述二次颗粒的重量M2的比值M1/M2小于0.03时，所述一次颗粒的质量M1太小，则会导致所述负极材料层130中一次颗粒的数量含量N的值过小，使得负极材料层130中一次颗粒的数量太少，二次颗粒的数量太多，最终使负极极片100无法同时满足电池20高能量密度和高首周放电效率的要求。
具体地，所述一次颗粒的重量M1与所述二次颗粒的重量M2的比值可以为但不限于为0.03、0.1、0.5、1、2.6、3.98、5.00、8.29、10.50、13.60及15等。
在一些实施例中，所述负极极片100的性能因子h满足关系式：h＝[N×G1+(1-N)×G2]×SSA×P；其中，0.2≤h≤1.8；其中，N为所述负极材料层130中一次颗粒 的数量含量，G1为所述一次颗粒的缺陷值，G2为所述二次颗粒的缺陷值，SSA为所述硬碳材料的比表面积的数值，P为所述负极材料层130的孔隙率。
可以理解地，所述负极极片100的性能因子h代表该负极极片100的综合性能，例如能量密度、首周放电效率、倍率性能等动力学性能和循环性能。
可以理解地，所述负极极片100的性能因子h满足关系式：h＝[N×G1+(1-N)×G2]×SSA×P，可以为，通过调控所述负极材料层130中一次颗粒的数量含量N、所述一次颗粒的缺陷值G1、所述二次颗粒的缺陷值G2及所述硬碳材料的比表面积的数值SSA及所述负极材料层130的孔隙率P，可以综合所述一次颗粒与所述二次颗粒的优异性能，即所述一次颗粒能为所述负极材料层130提供更多的活性位点，从而提高电池20的能量密度，而所述二次颗粒能减少所述负极材料层130与电解质的副反应，提高电池20的首周放电效率。通过控制负极材料层130整体的结构参数和负极极片100的结构参数，可以进一步调控所述负极极片100的性能因子h，使得所述一次颗粒与二次颗粒可以发挥各自的优势，从而平衡电池20的循环性能和充放电性能，同时提升负极极片100的综合性能较好，使得含有该负极极片100的电池20具有较高的能量密度和倍率性能，同时具备良好的循环性能和稳定性。
当所述负极极片100的性能因子h的值满足0.2≤h≤1.8时，含有该负极极片100的电池20的能量密度和首周放电效率较高，且电池20的循环性能和动力性能都较好。当所述负极极片100的性能因子h的值大于1.8时，所述负极极片100的综合性能较差，所述负极极片100不能同时满足电池20对高能量密度、高首周放电效率及高倍率性能等的要求；当所述负极极片100的性能因子h的值小于0.2时，所述负极极片100也无法达到电池20对高能量密度、高首周放电效率及高倍率性能等的要求，所述负极极片100的综合性能较差。
具体地，所述负极极片100的性能因子h的值可以为但不限于为0.2、0.6、0.75、0.9、1.2、1.5、1.6、1.7及1.8等。
优选地，当0.3g≤h≤1.4时，所述负极极片100的综合性能较优，使得含有该负极极片100的电池20不仅具有较高的能量密度和高首周放电效率，同时具备较高的循环性能和安全性能。
在一些申请实施例中，所述负极极片100还包括第一粘结剂及第一导电剂。
所述第一粘结剂用于粘结和保持负极材料层130，增强负极材料层130与负极集流体110的电子接触，更好地稳定负极极片100的结构。其中，所述第一粘结剂包括丁苯橡胶(SBR)、聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚乙烯醇(PVA)、聚丙烯腈(PAN)、聚丙烯酸(PAA)、聚丙烯酸酯、羧甲基纤维素(CMC)、海藻酸钠等的一种或多种。
所述第一导电剂使得负极极片100具有良好的充放电性能，减小负极极片100的接触电阻，加速电子的移动速率，从而提高负极极片100的充放电效率。其中，所述第一导电剂包括乙炔黑、导电炭黑、碳纳米管、碳纤维、石墨烯等中的一种或多种。
请参见图3和图4，本申请实施例还提供了一种电池20，所述电池20包括正极极片200、电解液300、本申请实施例中所述的负极极片100以及隔膜400，所述正极极片200至少部分浸渍于所述电解液300中；所述隔膜400位于所述正极极片200的一侧，且至少部分浸渍于所述电解液300中；所述负极极片100设置于所述隔膜400背离所述正极极片200的一侧且至少部分浸渍于所述电解液300中。
可选地，所述正极极片200包括正极集流体及正极材料层，所述正极材料层设置于所述正极集流体的表面，所述正极材料层包括正极活性材料、第二粘结剂及第二导电剂。
所述正极活性材料包括过渡金属氧化物、聚阴离子型化合物、有机聚合物、普鲁士蓝类 材料中的一种或多种。
所述第二粘结剂用于粘结和保持正极材料层，增强正极材料层与正极集流体的电子接触，更好地稳定正极极片200的结构。其中，所述第二粘结剂包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚丙烯腈(PAN)、聚丙烯酸(PAA)等的一种或多种。
所述第二导电剂使得正极极片200具有良好的充放电性能，减小正极极片200的接触电阻，加速电子的移动速率，从而提高正极极片200的充放电效率。其中，所述第二导电剂包括乙炔黑、导电炭黑、碳纳米管、碳纤维、石墨烯等中的一种或多种。
可选地，所述电解液300包括电解质盐(如六氟磷酸锂、六氟磷酸钠等)及有机溶剂，其中电解质盐和有机溶剂的具体种类及组成均是电池20领域的常规选择，可根据实际需求进行选择。
所述隔膜400是现有电池20领域中的任何隔膜400材料，所述隔膜400包括聚丙烯(PP)、聚乙烯(PE)、陶瓷隔膜400中的一种或多种。
所述电池20包括本申请实施例中的负极极片100，所述负极极片100通过对负极材料层130整体结构的调试提高了自身的综合性能，使得包括所述负极极片100的电池20同时具备高能量密度及高首周效率等。
下面分多个实施例对本申请技术方案进行进一步的说明。
实施例1至实施例7
1.负极极片100的制备
(1)二次颗粒的制备：将一次颗粒在惰性气体(例如：氩气)保护中经过1000℃～1300℃焙烧，之后加入粘结沥青混合并在反应釜中进行二次造粒得到二次颗粒，向二次颗粒添加包覆沥青搅拌并在惰性气体(例如：氩气)保护下且温度小于1000℃焙烧碳化进行碳包覆，然后经过筛分、除磁工序后得到碳包覆的二次颗粒。
(2)硬碳材料的制备：将一次颗粒、包覆有碳包覆层的二次颗粒混合得到硬碳材料。
(3)负极极片100的制备：将硬碳材料、第一导电剂(导电炭黑)、第一粘结剂(羟甲基纤维素钠+丁苯橡胶，CMC+SBR)按照95.5:1.5:2的质量比混合，将混合后的粉料置于真空搅拌机中，加入去离子水搅拌，得到负极浆料；将该负极浆料均匀涂覆在负极集流体110的相对两侧表面上形成负极材料层130，将涂有负极浆料的负极集流体110转移至烘箱内干燥，然后经过辊压、分切后得到负极极片100。
2.正极极片200的制备
将正极活性材料(Na 3V 2(PO4) 3)、第二导电剂(导电炭黑)、第二粘结剂(聚偏氟乙烯，PVDF)按照95:2.5:2.5的质量比混合，将混合后的粉料置于真空搅拌机中，加入N-甲基吡咯烷酮(NMP)，搅拌均匀得到正极浆料；将正极浆料均匀涂覆于正极集流体的相对两侧表面上，将涂有正极浆料的正极集流体转移至烘箱内干燥，然后经过辊压、分切后得到正极极片200。
3.电解液300的制备
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按体积比1:1:1混合得到混合溶剂，再向其中加入干燥的钠盐NaPF 6，配成浓度为1mol/L的电解液300。
4.电池20的制备
将上述制备的正极极片200、负极极片100和聚丙烯隔膜400按顺序叠好，使隔膜400处于正负极极片100之间，然后卷绕得到裸电芯，将裸电芯装入铝塑膜软包中，干燥后注入电解液300，经过真空封装、静置、化成、整形等工序后得到电池20。
实施例1至实施例7中硬碳材料的参数及负极材料层的参数各不相同，具体信息如表1所示。
为突出本申请的有益效果，设置以下对比例。
对比例1及对比例2
对比例1及对比例2中负极极片的制备、正极极片的制备、电解液的制备以及电池的制备与实施例1至实施例7中的对应步骤相同，设置对比例1及对比例2的硬碳材料的参数及负极材料层130的参数，与实施例1至实施例7形成对比，具体信息如表1所示。
对比例3
1.负极极片100的制备
(1)二次颗粒的制备：将一次颗粒在惰性气体(例如：氩气)保护中经过1000℃～1300℃焙烧，之后加入粘结沥青混合并在反应釜中进行二次造粒得到二次颗粒，向二次颗粒添加包覆沥青搅拌并在惰性气体(例如：氩气)保护下且温度小于1000℃焙烧碳化进行碳包覆，然后经过筛分、除磁工序后得到碳包覆的二次颗粒。本对比例中的硬碳材料仅包括二次颗粒，不包括一次颗粒。
(2)负极极片100的制备：将硬碳材料、第一导电剂(导电炭黑)、第一粘结剂(羟甲基纤维素钠+丁苯橡胶，CMC+SBR)按照95.5:1.5:2的质量比混合，将混合后的粉料置于真空搅拌机中，加入去离子水搅拌，得到负极浆料；将该负极浆料均匀涂覆在负极集流体110的相对两侧表面上形成负极材料层130，将涂有负极浆料的负极集流体110转移至烘箱内干燥，然后经过辊压、分切后得到负极极片100。
2.正极极片200的制备：同实施例1至实施例7中正极极片200的制备。
3.电解液300的制备：同实施例1至实施例7中电解液300的制备。
4.电池20的制备：同实施例1至实施例7中电池20的制备。
设置对比例3的硬碳材料的参数及负极材料层的参数，与实施例1至实施例7形成对比，具体信息如表1所示。
对比例4
1.负极极片100的制备
(1)硬碳材料的制备：本对比例中的硬碳材料仅包括一次颗粒，不包括二次颗粒。
(2)负极极片100的制备：将硬碳材料、第一导电剂(导电炭黑)、第一粘结剂(羟甲基纤维素钠+丁苯橡胶，CMC+SBR)按照95.5:1.5:2的质量比混合，将混合后的粉料置于真空搅拌机中，加入去离子水搅拌，得到负极浆料；将该负极浆料均匀涂覆在负极集流体110的相对两侧表面上形成负极材料层130，将涂有负极浆料的负极集流体110转移至烘箱内干燥，然后经过辊压、分切后得到负极极片100。
2.正极极片200的制备：同实施例1至实施例7中正极极片200的制备。
3.电解液300的制备：同实施例1至实施例7中电解液300的制备。
4.电池20的制备：同实施例1至实施例7中电池20的制备。
设置对比例4的硬碳材料的参数及负极材料层的参数，与实施例1至实施例7形成对比，具体信息如表1所示。
性能测试
1.缺陷值测试：采用拉曼光谱法分别测定实施例1至实施例7中一次颗粒的缺陷值G1和二次颗粒的缺陷值G2以及对比例1至对比例4中一次颗粒的缺陷值G1和二次颗粒的缺陷值G2。
2.数量含量测试：测试实施例1至实施例7以及对比例1至对比例4中制得的负极极片的断面的扫描电镜，根据扫描电镜图计算所述一次颗粒的数量n1及所述二次颗粒的数量n2，通过关系式N＝n1/(n1+n2)得出实施例1至实施例7以及对比例1至对比例4中的负极材料层130中的一次颗粒的数量含量N。
3.比表面积测试：根据GB/T 19587-2017/ISO 9277：2010采用气体吸附BET法测定固态物质比表面积，得到实施例1至实施例7以及对比例1至对比例4中的硬碳材料的比表面积数值SSA。
4.孔隙率测试：根据GB/T 21650.1-2008/ISO 15901-1,2005压汞法和气体吸附法测定固体材料孔径分布和孔隙度，根据材料的孔径分布和孔隙度计算得到实施例1至实施例7以及对比例1至对比例4中的负极极片100的孔隙率，具体可参阅第1部分：压汞法数。
5.根据公式h＝[N×G1+(1-N)×G2]×SSA×P计算实施例1至实施例7以及对比例1至对比例4中负极极片的性能因子h。
上述性能测试中得到的实施例1至实施例7、对比例1至对比例4的负极极片100的结构参数如表1所示。
表1：实施例1至实施例7、对比例1至对比例4的负极极片100的结构参数表
Figure PCTCN2022143192-appb-000001
Figure PCTCN2022143192-appb-000002
6.电池20性能测试
6.1能量密度测试：在25℃下，使用电子天平对各钠离子电池20进行称重；在25℃下，将制得的各钠离子电池20以1C倍率充电和放电，记录此时的实际放电能量；钠离子电池20的实际放电能量与钠离子电池20重量的比值即为钠离子电池20的实际能量密度。
6.2循环性能测试：将各钠离子电池20分别以3C倍率充电及1C倍率放电，进行满充满放循环测试，记录循环2000圈后的容量保持率。
6.3动力学性能测试：在25℃下，将各钠离子电池20以4C满充、以1C满放，重复10次充放电循环后，再将该电池20以4C倍率充电至满电态，然后拆解出负极极片100，并观察负极极片100表面析钠情况。其中，负极极片100表面析钠区域面积小于2％认为是不析钠，负极极片100表面析钠区域面积小于5％认为是轻微析钠，负极表面析钠区域为5％～40％，则认为是中度析钠，负极表面析钠区域面积大于40％，则视为严重析钠。
上述电池20性能测试中得到的实施例1至实施例7、对比例1至对比例4的电池20的电化学性能如下表2所示。
表2实施例1至实施例7、对比例1至对比例4的电池20的电化学性能表
Figure PCTCN2022143192-appb-000003
Figure PCTCN2022143192-appb-000004
由表1及表2可知，实施例1至实施例7中负极极片100的性能因子h的取值分别为0.72、0.94、0.46、1.26、1.53、0.23及0.26，满足0.2≤h≤1.8，所述负极极片100具有较好的综合性能，含有该负极极片100的电池20的能量密度和首周放电效率较高，且电池20的循环性能和动力性能都较好。其中，实施例1至实施例4中负极极片100的性能因子h的取值满足0.3≤h≤1.4，所述负极极片100不仅具有很好的综合性能，且在测试过程中不析钠，具有较高的安全性能。实施例2中负极极片100的性能最优，具有最高的能量密度和首周放电效率，且循环2000圈容量保持率最高。由此可知，当负极极片100的性能因子h满足0.2≤h≤1.8，所对应的负极极片100的综合性能先逐渐提升，后逐渐下降。对比例1、对比例3及对比例4中负极极片100的性能因子h的值小于0.2，其所对应的负极极片100的综合性能较差，使得含有该负极极片100的电池20能量密度和首周放电效率偏低，且电池20的循环性能和安全性能都较差。对比例2中负极极片100的性能因子h的值大于1.8，其对应的负极极片100的综合性能也较差，使得含有该负极极片100的电池20能量密度和首周放电效率偏低，且电池20的循环性能和安全性能都较差。
具体地，请参见表1及表2中实施例1至实施例4，实施例7中所述一次颗粒的缺陷值G1与所述二次颗粒的缺陷值G2的差值的绝对值，即|G1-G2|的值，以及所对应的电池20的电化学性能。其中实施例1至实施例4中|G1-G2|的值都满足0.04≤|G1-G2|≤0.2，使得所述一次颗粒的缺陷值G1与二次颗粒的缺陷值G2存在一定差距，使得所述一次颗粒与所述二次颗粒因缺陷值不同而具有不同的优势，缺陷值较大的硬碳颗粒可以提高电池20的能量密度，缺陷值较小的硬碳颗粒可以提高电池20的首周放电效率，有利于负极材料层130整体结构的参数的调试，使得负极材料层130具有较好的性能。其中，实施例7中所述一次颗粒的缺陷值G1与所述二次颗粒的缺陷值G2的差值的绝对值，即|G1-G2|的值小于0.04，所述一次颗粒的缺陷值与所述二次颗粒的缺陷值的差值太小，所述一次颗粒与二次颗粒难以发挥各自的优势，使得所述负极材料层130的整体性能不佳，实施例7所对应的电池20具有较低的能量密度和首周放电效率。
具体地，请参见表1及表2中实施例2及实施例6所述硬碳材料的比表面积的数值SSA以及所对应的电池20的电化学性能。其中，实施例2及实施例6中所述硬碳材料的比表面积的数值SSA的值分别为4.2及1.2。
实施例2中所述硬碳材料的比表面积的数值SSA的值适中，使得硬碳材料与电解液300既有足够的接触面积，又不至于与电解液300发生过多的副反应而降低首周放电效率，使得实施例2所对应的电池20具有较高的能量密度和较高的首周放电效率。实施例6中所述硬碳材料的比表面积的数值SSA小于1.3，所述硬碳材料的比表面积较小，表面活性位点降低，电池20的充放电性能稍差，使得电池20的能量密度降低，且在测试过程中有轻微析钠现象，降低了钠离子电池20在循环过程中的容量保持率及安全性能。
具体地，请参见表1及表2中对比例3、实施例6、实施例1、实施例5及对比例4的所述负极材料层130中一次颗粒的数量含量N的值以及所对应的电池20的电化学性能。其中， 对比例3、实施例6、实施例1、实施例5及对比例4的所述负极材料层130中一次颗粒的数量含量N的值分别为0、0.3、0.5、0.7及1。
对比例3的负极材料层130为单一的二次颗粒，所述二次颗粒的缺陷值较小，其活性位点较少，降低了活性离子的储存位点，使得电池20的能量密度偏低。实施例6、实施例1及实施例5中所述负极材料层130中一次颗粒的数量含量N的值都满足0.1≤N≤0.9，其中实施例1所对应的负极材料层性能最优，负极材料层中的一次颗粒能为所述负极材料层130提供较多的活性位点且与电解液300的副反应不至于过多而影响负极材料层的性能，其电池的能量密度最高。而对比例4中的负极材料层130为单一的一次颗粒，一次颗粒的缺陷值较多，导致所述硬碳材料的缺陷值较多，使得负极极片100与电解液300的副反应太多，活性离子消耗增多，降低首周放电效率，故对比例4中的电池能量密度也很低。
具体地，请参见表1及表2中实施例5及实施例2中所述负极材料层130的孔隙率P以及所对应的电池20的电化学性能。其中，实施例5及实施例2中所述负极材料层130的孔隙率P的值分别为0.27及0.36。
实施例5中所述负极材料层130的孔隙率P的值小于0.32，电解液300在所述负极极片100中的浸润性能和保液能力稍差，增加了活性离子的传输阻力，电池20的充放电性能稍差，在测试过程中有轻微析钠现象。实施例2中所述负极材料层130的孔隙率P的值适中，既能提高电解液300在负极极片100中的浸润性能和保液能力，降低活性离子的传输阻力，使得所述负极极片100具有较好的动力学性能，又使得所述负极极片100在化成及循环过程中与电解液300的副反应不至于过多而降低电池20的循环寿命，使实施例2中的电池同时具备高能量密度、高首周放电效率及较优的循环性能。
请参见图5，本申请实施例还提供了一种电池包30，所述电池包30包括：箱体50以及本申请实施例提供的电池，所述多个电池收容于所述箱体50内，所述多个电池的连接方式包括串联、并联中的至少一种。所述电池包30对电池20具有固定和保护的作用，此外，所述电池包30具有较高的能量密度及较高的首周效率，同时具有较高的循环性能和安全性能。
请参见图6，本申请实施例还提供了一种用电设备1，所述用电设备1包括：用电设备本体10，所述用电设备本体10包括设备正极及设备负极；以及本申请实施例提供的电池20，所述电池20的正极极片200用于电连接用电设备本体的设备正极，电池20的负极极片100用于电连接所述用电设备本体10的设备负极，所述电池30用于为所述用电设备本体10进行供电。所述电池20具有高能量密度及高首周效率，且具有较高的循环性能和安全性能，为用电设备1提供了稳定和安全的电能。
本申请的用电设备1可以为但不限于为手机、平板电脑、笔记本电脑、台式电脑、智能手环、智能手表、电子阅读器等电子设备。
可以理解地，本实施方式中所述的用电设备仅仅为所述电池所应用的用电设备的一种形态，不应当理解为对本申请提供的用电设备的限定，也不应当理解为对本申请各个实施方式提供的电池的限定。
在本申请中提及“实施例”“实施方式”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所述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，本申请所描述的实施例可以与其它实施例相结合。此外，还应该理解的是，本申请各实施例所描述的特征、结构或特性，在相互之间不存在矛盾的情况下，可以任意组合，形成又一未脱离本申请技术方案的精神和范围的实施例。
最后应说明的是，以上实施方式仅用以说明本申请的技术方案而非限制，尽管参照以上较佳实施方式对本申请进行了详细说明，本领域的普通技术人员应当理解，可以对本申请的技术方案进行修改或等同替换都不应脱离本申请技术方案的精神和范围。

Claims (12)

  1. 一种负极极片，其特征在于，包括：
    负极集流体；以及
    负极材料层，所述负极材料层设置于所述负极集流体的表面，所述负极材料层包括硬碳材料，所述硬碳材料包括一次颗粒和二次颗粒，所述一次颗粒的缺陷值与所述二次颗粒的缺陷值不同。
  2. 根据权利要求1所述的负极极片，其特征在于，所述一次颗粒的缺陷值为G1，所述二次颗粒的缺陷值为G2，且0.04≤|G1-G2|≤0.2。
  3. 根据权利要求2所述的负极极片，其特征在于，所述一次颗粒的缺陷值G1的范围值为：0.5≤G1≤0.8；所述二次颗粒的缺陷值G2的范围值为：0.5≤G2≤0.8。
  4. 根据权利要求1所述的负极极片，其特征在于，所述负极材料层中一次颗粒的数量含量N的取值范围为：0.1≤N≤0.9。
  5. 根据权利要求1所述的负极极片，其特征在于，所述硬碳材料的比表面积的数值SSA的取值范围为：1.3≤SSA≤6。
  6. 根据权利要求1所述的负极极片，其特征在于，所述负极材料层的孔隙率P的取值范围为：0.32≤P≤0.4。
  7. 根据权利要求1至6任一项所述的负极极片，其特征在于，所述负极极片的性能因子h满足关系式：h＝[N×G1+(1-N)×G2]×SSA×P；
    其中，0.2≤h≤1.8；
    其中，N为所述负极材料层中一次颗粒的数量含量，G1为所述一次颗粒的缺陷值，G2为所述二次颗粒的缺陷值，SSA为所述硬碳材料的比表面积的数值，P为所述负极材料层的孔隙率。
  8. 根据权利要求1所述的负极极片，其特征在于，所述一次颗粒D50的粒径R1的取值范围为：4μm≤R1≤12μm；所述二次颗粒D50的粒径R2的取值范围为：8μm≤R2≤18μm，其中，D50为颗粒的累积粒度分布百分数达到50％时所对应的粒径。
  9. 根据权利要求1至6、权利要求8任一项所述的负极极片，其特征在于，所述一次颗粒的重量为M1，所述二次颗粒的重量为M2，则M1/M2满足0.03≤M1/M2≤15。
  10. 一种电池，其特征在于，所述电池包括：
    电解液；
    正极极片，所述正极极片至少部分浸渍于所述电解液中；
    隔膜，位于所述正极极片的一侧，且至少部分浸渍于所述电解液中，以及
    权利要求1至9任一项所述的负极极片，所述负极极片设置于所述隔膜背离所述正极极片的一侧且至少部分浸渍于所述电解液中。
  11. 一种电池包，其特征在于，包括：
    箱体；以及
    多个权利要求10所述的电池，所述多个电池收容于所述箱体内，所述多个电池的连接方式包括串联、并联中的至少一种。
  12. 一种用电设备，其特征在于，包括：
    用电设备本体，所述用电设备本体包括设备正极及设备负极；以及
    权利要求10所述的电池，所述电池的正极极片用于电连接用电设备本体的设备正极，电池的负极极片用于电连接所述用电设备本体的设备负极，所述电池包用于为所述用电设备本体进行供电。
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