WO2024065597A1 - 负极材料、二次电池和电子装置 - Google Patents

负极材料、二次电池和电子装置 Download PDF

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WO2024065597A1
WO2024065597A1 PCT/CN2022/123059 CN2022123059W WO2024065597A1 WO 2024065597 A1 WO2024065597 A1 WO 2024065597A1 CN 2022123059 W CN2022123059 W CN 2022123059W WO 2024065597 A1 WO2024065597 A1 WO 2024065597A1
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negative electrode
electrode material
cap
lithium
secondary battery
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French (fr)
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严怡
董佳丽
谢远森
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to CN202280058223.6A priority Critical patent/CN117916903A/zh
Priority to PCT/CN2022/123059 priority patent/WO2024065597A1/zh
Priority to EP22960225.5A priority patent/EP4579770A4/en
Publication of WO2024065597A1 publication Critical patent/WO2024065597A1/zh
Priority to US19/092,457 priority patent/US20250226413A1/en
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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
    • H01M4/36—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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • H—ELECTRICITY
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    • 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
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/74—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by peak-intensities or a ratio thereof only
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    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/78—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by stacking-plane distances or stacking sequences
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
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    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
    • C01P2002/82—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by IR- or Raman-data
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
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    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/16—Pore diameter
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • 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 energy storage, and in particular to a negative electrode material, a secondary battery and an electronic device.
  • the present application provides a negative electrode material and a secondary battery including the negative electrode material, so as to increase the capacity of the negative electrode material and further improve the energy density of the secondary battery including the negative electrode material.
  • the present application provides a negative electrode material, which includes a carbon-based material.
  • the negative electrode material satisfies: 0.004cm 3 /g ⁇ S ⁇ 0.030cm 3 /g, S is the adsorption volume of pores with a pore size of 3nm to 35nm in the negative electrode material, and a button battery with lithium as the negative electrode and the negative electrode material as the positive electrode is used for charge and discharge test.
  • the gram capacity of the negative electrode material is Cap.A
  • the gram capacity of the negative electrode material is Cap.B
  • 10mAh/g ⁇ Cap.A-Cap.B ⁇ 20mAh/g The adsorption volume of pores of 3nm to 35nm can characterize the number of mesopores in the structure of the negative electrode material. The larger the adsorption volume, the higher the proportion of mesopores, the more pores in the negative electrode material, and the adsorption of active ions and lithium insertion can be increased, thereby improving the capacity of the negative electrode material. However, too many pores will have an adverse effect on the first effect, cycle and other performances of the secondary battery.
  • the Cap.A-Cap.B value of the negative electrode material is related to the defective lithium insertion of the negative electrode material.
  • the present application can further improve the adsorption and defective lithium insertion capacity of the negative electrode material by controlling the adsorption volume of the pores of 3nm to 35nm of the negative electrode material and the Cap.A-Cap.B value within the above range, thereby improving the capacity of the secondary battery.
  • the negative electrode material satisfies: 0.2 ⁇ Id/Ig ⁇ 0.5, where Id is the intensity of the peak at 1350cm -1 in the Raman spectrum, and Ig is the intensity of the peak at 1580cm -1 in the Raman spectrum.
  • the Id/Ig ratio can characterize the defectivity of the negative electrode material, and the larger the value, the higher the defectivity. High defectivity can increase the deintercalation channel of active ions and increase the deintercalation speed of active ions, thereby improving the kinetic properties of the negative electrode material. However, too many defects will lead to reduced performance of the first effect, cycle, storage, etc. of the secondary battery. When the Id/Ig ratio is within the above range, the secondary battery can not only show good kinetics, but also its first effect cycle and other performance will not be significantly reduced. In some embodiments, 0.3 ⁇ Id/Ig ⁇ 0.5.
  • the average stacking thickness of the negative electrode material along the a-axis direction is La as tested by X-ray diffraction method, 100nm ⁇ La ⁇ 140nm.
  • La represents the average size of the negative electrode material crystals along the a-axis direction.
  • the larger the La value the higher the lithium insertion and storage capacity of the negative electrode material, and the higher its gram capacity accordingly.
  • the La value of the negative electrode material of the present application is within the above range, and the negative electrode material has a high gram capacity while the cycle performance will not be significantly reduced.
  • 110nm ⁇ La ⁇ 140nm is within the above range, and the negative electrode material has a high gram capacity while the cycle performance will not be significantly reduced.
  • the specific surface area of the negative electrode material is 2 cm 2 /g to 15 cm 2 /g.
  • the smaller the specific surface area of the negative electrode material the smaller the area in contact with the electrolyte, thereby reducing the active ions consumed by the secondary battery when the SEI film is first formed, and the first effect is increased.
  • the specific surface area is too small, electrolyte infiltration and active diffusion become difficult, thereby affecting the kinetic performance of the secondary battery.
  • the specific surface area of the negative electrode material of the present application is within the above range, the secondary battery has a high first effect and its kinetic performance will not be significantly reduced.
  • the specific surface area of the negative electrode material is 4 cm 2 /g to 10 cm 2 /g.
  • the 5t powder compaction density of the negative electrode material is 1.7g/cm 3 to 2.2g/cm 3.
  • the powder compaction density represents the degree to which the negative electrode material can be compressed during pressing. The larger the value, the more it can be compressed during pressing, and the higher the volume energy density of the corresponding secondary battery.
  • the powder compaction density of the negative electrode material of the present application is within the above range, and the secondary battery including the negative electrode material has a high energy density.
  • the 5t powder compaction density of the negative electrode material is 1.8g/cm 3 to 2.1g/cm 3 .
  • the Dv50 of the negative electrode material satisfies: 5 ⁇ m ⁇ Dv50 ⁇ 26 ⁇ m.
  • the Dv50 of the negative electrode material of the present application is within the above range, which can ensure that the negative electrode material has a higher gram capacity and that the kinetic performance is not significantly reduced. In some embodiments, 10 ⁇ m ⁇ Dv50 ⁇ 20 ⁇ m.
  • the ratio of the diffraction peak area C004 of the 004 crystal plane of the negative electrode material to the diffraction peak area C110 of the 110 crystal plane satisfies 1 ⁇ C004/C110 ⁇ 5 as tested by X-ray diffraction.
  • the ratio of C004/C110 is a parameter reflecting the crystal orientation of the negative electrode material. The larger the C004/C110 value, the higher the crystal orientation, and the more limited the surface of the active ion deintercalation in the negative electrode material. The smaller the C004/C110 value, the lower the crystal orientation, and the active ions can be deintercalated in multiple directions of the negative electrode material.
  • the C004/C110 of the negative electrode material of the present application is within the above range, and the active ions can be quickly deintercalated in the negative electrode material, thereby further improving the discharge rate performance of the secondary battery.
  • the method for preparing a carbon-based material comprises: preparing a graphite composite material, spheroidizing, coating and carbonizing one or more of natural graphite or artificial graphite.
  • the preparation process of the graphite composite material comprises dissolving one or more of natural graphite and artificial graphite and polymethyl methacrylate (PMMA) in N-N dimethylformamide (DMF) at the same time, stirring at a temperature of 50°C to 80°C for 10h to 14h, filtering and collecting the precipitate, washing with deionized water and ethanol 2 to 4 times, and completely drying at a temperature of 60°C to 90°C to obtain a graphite composite material precursor; heating the graphite composite material precursor to 1000°C to 1200°C in a tubular furnace at a heating rate of 8°C/min to 16°C/min, and then passing the graphite composite material precursor into the tubular furnace.
  • PMMA polymethyl methacrylate
  • DMF N-N dimethylformamide
  • a CH 4 /C 2 H 2 /H 2 mixed gas (ratios of 5-10:5-10:80-85, respectively) is maintained for 8 to 12 hours and then naturally cooled to room temperature, thereby obtaining a graphite composite material.
  • the spheroidization process includes: applying continuous impact force, compression force and shear force from a turntable, an inner wall and between particles to a mixture containing a graphite composite material and a dispersant solution, so that the graphite composite material is spheroidized.
  • the spheroidization time is 10 minutes to 20 minutes.
  • the spheroidization device by using a spheroidization device to apply impact force, compression force and shear force to the mixture, the mixture is collided, rubbed, sheared and bent and folded, thereby removing the edges and corners of the graphite composite material while achieving the effect of fixing the micropowder to the large particles.
  • the spheroidization device is a mixing granulator.
  • the rotation speed of the spheroidization device is 30Hz to 50Hz.
  • the dispersant solution is an aqueous solution of carboxymethyl cellulose (CMC).
  • CMC carboxymethyl cellulose
  • the mass content of carboxymethyl cellulose in the dispersant solution is 0.5% to 2%. In some embodiments, the mass content of the dispersant solution is 5% to 20% based on the mass of the graphite composite material.
  • the coating process includes: coating the spheroidized graphite composite material with asphalt.
  • the mass content of the asphalt is 2% to 15% based on the mass of the spheroidized graphite composite material.
  • the temperature of the carbonization treatment is 900°C to 1500°C.
  • the present application provides a secondary battery comprising a negative electrode, the negative electrode comprising a negative electrode collector and a negative electrode active material layer arranged on at least one surface of the negative electrode collector, wherein the negative electrode active material layer comprises the negative electrode material of the first aspect.
  • the negative electrode further includes a conductive coating between the negative electrode active material layer and the negative electrode current collector.
  • the conductive coating includes at least one of carbon fiber, Ketjen black, acetylene black, carbon nanotubes and graphene. The conductive coating can conduct electrons, and the charge transfer impedance is significantly reduced, thereby further improving the dynamic performance of the secondary battery.
  • the thickness of the conductive coating is 0.5 ⁇ m to 1.2 ⁇ m.
  • the present application provides an electronic device comprising the secondary battery of the second aspect.
  • FIG. 1 shows the capacity of the lithium-ion batteries of Example 6 and Comparative Example 1 of the present application.
  • any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, and any upper limit can be combined with any other upper limit to form an undefined range.
  • each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an undefined range.
  • a list of items connected by the terms “at least one of,” “at least one of,” “at least one of,” or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase “at least one of A and B” means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase “at least one of A, B, and C” means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.
  • Item A may contain a single component or multiple components.
  • Item B may contain a single component or multiple components.
  • Item C may contain a single component or multiple components.
  • the negative electrode material provided in the present application includes a carbon-based material.
  • the negative electrode material satisfies: 0.004cm 3 /g ⁇ S ⁇ 0.030cm 3 /g, S is the adsorption volume of pores with a pore size of 3nm to 35nm in the negative electrode material, and a button battery with lithium as the negative electrode and the negative electrode material as the positive electrode is used for charge and discharge test.
  • the button battery is discharged to -5mV
  • the gram capacity of the negative electrode material is Cap.A
  • the button battery is discharged to 5mV
  • the gram capacity of the negative electrode material is Cap.B, wherein 10mAh/g ⁇ Cap.A-Cap.B ⁇ 20mAh/g.
  • the adsorption volume of pores of 3nm to 35nm can characterize the number of mesopores in the structure of the negative electrode material.
  • too many pores will have an adverse effect on the first effect, cycle and other performances of the secondary battery.
  • the Cap.A-Cap.B value of the negative electrode material is related to the defective lithium insertion of the negative electrode material.
  • the present application can further improve the adsorption and defective lithium insertion capacity of the negative electrode material and improve the capacity of the secondary battery by controlling the adsorption volume of 3nm to 35nm pores of the negative electrode material and the Cap.A-Cap.B value within the above range.
  • S is 0.005 cm 3 /g, 0.008 cm 3 /g, 0.01 cm 3 /g, 0.011 cm 3 /g, 0.012 cm 3 /g, 0.013 cm 3 /g, 0.014 cm 3 /g, 0.015 cm 3 /g, 0.016 cm 3 /g, 0.017 cm 3 /g, 0.018 cm 3 /g, 0.019 cm 3 / g, 0.02 cm 3 /g, 0.021 cm 3 /g, 0.022 cm 3 /g, 0.023 cm 3 /g, 0.024 cm 3 /g, 0.025 cm 3 /g, 0.026 cm 3 /g, 0.027 cm 3 /g, 0.028 cm 3 /g, 0.029 cm 3 /g, 3 or a range consisting of any two of these values.
  • Cap.A-Cap.B is 10.5mAh/g, 11mAh/g, 11.5mAh/g, 12mAh/g, 12.5mAh/g, 13mAh/g, 13.5mAh/g, 14.5mAh/g, 15mAh/g, 15.5mAh/g, 16mAh/g, 16.5mAh/g, 17mAh/g, 17.5mAh/g, 18.5mAh/g, 19mAh/g, 19.5mAh/g, or a range consisting of any two of these values. In some embodiments, 14mAh/g ⁇ Cap.A-Cap.B ⁇ 18mAh/g.
  • the button cell used in this application is composed as follows:
  • Negative electrode Lithium sheet is used as negative electrode.
  • Positive electrode 97wt% graphite, 1.5wt% sodium carboxymethyl cellulose (CMC) and 1.5wt% styrene butadiene rubber (SBR) as the positive electrode active material layer, and copper foil as the current collector.
  • CMC carboxymethyl cellulose
  • SBR styrene butadiene rubber
  • Electrolyte 12.5 wt% LiPF 6
  • solvent is ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) in a mass ratio of 1:3:3:3, and 2 wt% fluoroethylene carbonate and 2 wt% 1,3-propane sultone are added.
  • the button cell was placed on a blue battery tester for testing.
  • the test process was to discharge to -5mv at 0.05C, stand for 5 minutes, discharge to -5mv at 0.05mA, discharge to -5mv at 0.01mA, and charge to 2.0V at 0.1C to get the charge capacity. Finally, divide it by the weight of the active material to get the gram capacity Cap.A of the negative electrode material. The ratio of the charge capacity to the discharge capacity gives the first efficiency.
  • the button cell was placed on a blue battery tester for testing.
  • the test process was to discharge to 5mv at 0.05C, stand for 5min, discharge to 5mv at 0.05mA, discharge to 5mv at 0.01mA, and charge to 2.0V at 0.1C to get the charge capacity. Finally, divide it by the weight of the active material to get the gram capacity Cap.B of the negative electrode material. The ratio of the charge capacity to the discharge capacity gives the first efficiency.
  • the negative electrode material satisfies: 0.2 ⁇ Id/Ig ⁇ 0.5, where Id is the intensity of the peak at 1350cm -1 in the Raman spectrum, and Ig is the intensity of the peak at 1580cm -1 in the Raman spectrum.
  • the Id/Ig ratio can characterize the defectivity of the negative electrode material, and the larger its value, the higher the defectivity. High defectivity can increase the deintercalation channel of active ions and increase the deintercalation speed of active ions, thereby improving the kinetic properties of the negative electrode material. However, too many defects will lead to reduced performance of the first effect, cycle, storage, etc. of the secondary battery.
  • Id/Ig is 0.23, 0.25, 0.27, 0.29, 0.33, 0.35, 0.37, 0.4, 0.43, 0.45, 0.47 or a range consisting of any two of these values. In some embodiments, 0.3 ⁇ Id/Ig ⁇ 0.5.
  • the average stacking thickness of the negative electrode material along the a-axis direction is La as tested by X-ray diffraction method, and 100nm ⁇ La ⁇ 140nm.
  • La represents the average size of the negative electrode material crystal along the a-axis direction.
  • the larger the La value the higher the lithium insertion and storage capacity of the negative electrode material, and the higher its gram capacity accordingly.
  • the La value is too high, although the gram capacity of the negative electrode material becomes larger, its cycle performance will decrease.
  • the La value of the negative electrode material of the present application is within the above range, and the negative electrode material has a high gram capacity while the cycle performance will not be significantly reduced.
  • La is 100nm, 103nm, 105nm, 107nm, 110nm, 113nm, 115nm, 117nm, 120nm, 123nm, 125nm, 127nm, 130nm, 133nm, 135nm, 137nm or a range consisting of any two of these values.
  • the specific surface area of the negative electrode material is 2cm2 /g to 15cm2 /g.
  • the smaller the specific surface area of the negative electrode material the smaller the area in contact with the electrolyte, so that the active ions consumed by the secondary battery when the SEI film is first formed are reduced, and the first effect is increased.
  • the specific surface area is too small, electrolyte infiltration and active diffusion become difficult, thereby affecting the kinetic performance of the secondary battery.
  • the specific surface area of the negative electrode material of the present application is within the above range, and the secondary battery has both a high first effect and its kinetic performance will not be significantly reduced.
  • the specific surface area of the negative electrode material is 3cm2 /g, 4.5cm2 /g, 5cm2 /g, 5.5cm2 /g, 6cm2 / g, 6.5cm2/ g , 7cm2 /g, 7.5cm2 /g, 8cm2 /g, 8.5cm2 /g, 9cm2 /g, 9.5cm2 /g or a range consisting of any two of these values.
  • the specific surface area of the negative electrode material is 4 cm 2 /g to 10 cm 2 /g.
  • the 5t powder compaction density of the negative electrode material is 1.7 g/cm 3 to 2.2 g/cm 3.
  • the powder compaction density represents the degree to which the negative electrode material can be compressed during pressing. The larger the value, the more it can be compressed during pressing, and the higher the volume energy density of the corresponding secondary battery.
  • the powder compaction density of the negative electrode material of the present application is within the above range, and the secondary battery including the negative electrode material has a high energy density.
  • the 5t powder compaction density of the negative electrode material is 1.72g/ cm3 , 1.74g/ cm3 , 1.76g/ cm3 , 1.78g/cm3, 1.82g/ cm3 , 1.84g/ cm3 , 1.86g/ cm3 , 1.88g/ cm3 , 1.9g/ cm3 , 1.92g/ cm3 , 1.94g/cm3, 1.96g/ cm3 , 1.98g/ cm3 , 2.0g/ cm3 , 2.02g/ cm3 , 2.04g/ cm3 , 2.06g/ cm3 , 2.08g/cm3, 2.12g/ cm3 , 2.14g/ cm3 , 2.16g/ cm3 , 2.18g/ cm3 3 or a range consisting of any two of these values.
  • the 5t powder compaction density of the negative electrode material is 1.8 g/cm 3 to 2.1 g/cm 3 .
  • the Dv50 of the negative electrode material satisfies: 5 ⁇ m ⁇ Dv50 ⁇ 26 ⁇ m.
  • Dv50 is 6 ⁇ m, 8 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m, 21 ⁇ m, 22 ⁇ m, 23 ⁇ m, 24 ⁇ m, 25 ⁇ m, or a range consisting of any two of these values.
  • the Dv50 of the negative electrode material of the present application is within the above range, which can ensure that the negative electrode material has a higher gram capacity and that the kinetic performance is not significantly reduced. In some embodiments, 10 ⁇ m ⁇ Dv50 ⁇ 20 ⁇ m. In the present application, Dv50 means that in the volume-based particle size distribution of the negative electrode material, 50% of the particle size is less than this value.
  • the ratio of the diffraction peak area C004 of the 004 crystal plane of the negative electrode material to the diffraction peak area C110 of the 110 crystal plane satisfies 1 ⁇ C004/C110 ⁇ 5 as tested by X-ray diffraction.
  • the ratio of C004/C110 is a parameter reflecting the crystal orientation of the negative electrode material. The larger the C004/C110 value, the higher the crystal orientation, and the more limited the surface of the active ion deintercalation in the negative electrode material. The smaller the C004/C110 value, the lower the crystal orientation, and the active ions can be deintercalated in multiple directions of the negative electrode material.
  • C004/C110 of the negative electrode material of the present application is within the above range, the active ions can be quickly deintercalated in the negative electrode material, thereby further improving the discharge rate performance of the secondary battery.
  • C004/C110 is 1.2, 1.4, 1.6, 1.8, 2.3, 2.5, 2.7, 3.0, 3.3, 3.5, 3.7, 4.0, 4.3, 4.5, 4.7, or a range consisting of any two of these values. In some embodiments, 1 ⁇ C004/C110 ⁇ 3.
  • the method for preparing a carbon-based material comprises: preparing a graphite composite material, spheroidizing, coating and carbonizing one or more of natural graphite and artificial graphite.
  • the preparation process of the graphite composite material includes dissolving one or more of natural graphite and artificial graphite and polymethyl methacrylate (PMMA) in NN dimethylformamide (DMF) at the same time, stirring at a temperature of 50°C to 80°C for 10h to 14h, filtering and collecting the precipitate, washing with deionized water and ethanol 2 to 4 times, and completely drying at a temperature of 60°C to 90°C to obtain a graphite composite material precursor; heating the graphite composite material precursor to 1000°C to 1200°C in a tube furnace at a heating rate of 8°C/min to 16°C/min, then introducing a CH4 / C2H2 / H2 mixed gas (in ratios of 5-10:5-10:80-85 , respectively) into the tube furnace, maintaining for 8h to 12h and then naturally cooling to room temperature to obtain the graphite composite material.
  • PMMA polymethyl methacrylate
  • DMF dimethylformamide
  • the spheroidization process includes: applying continuous impact force, compression force and shear force from a turntable, an inner wall and between particles to a mixture containing a graphite composite material and a dispersant solution, so that the graphite composite material is spheroidized.
  • the spheroidization time is 10min to 20min, for example, 12min, 14min, 16min or 18min.
  • the spheroidization device by using a spheroidization device to apply impact force, compression force and shear force to the mixture, the mixture is collided, rubbed, sheared and bent and folded, thereby removing the edges and corners of the graphite composite material while achieving the effect of fixing the micropowder to the large particles.
  • the spheroidization device is a mixing granulator.
  • the rotation speed of the spheroidization device is 30Hz to 50Hz, for example, 35Hz, 40Hz or 45Hz.
  • the dispersant solution is an aqueous solution of carboxymethyl cellulose (CMC).
  • CMC carboxymethyl cellulose
  • the mass content of carboxymethyl cellulose in the dispersant solution is 0.5% to 2%, for example, 0.7%, 1.0%, 1.3%, 1.5% or 1.7%.
  • the mass content of the dispersant solution is 5% to 20%, for example, 7%, 10%, 13%, 15%, 17% or 19%, based on the mass of the graphite composite material.
  • the coating process includes: coating the spheroidized graphite composite material with asphalt.
  • the mass content of asphalt is 2% to 15%, for example, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13% or 14%.
  • the temperature of the carbonization treatment is 900°C to 1500°C, for example, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C or 1450°C.
  • the carbonization time is 3h to 10h, for example, 4h, 5h, 6h, 7h, 8h or 9h.
  • the secondary battery provided in the present application includes a negative electrode, wherein the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes the negative electrode material of the first aspect.
  • the negative electrode further includes a conductive coating between the negative electrode active material layer and the negative electrode current collector.
  • the conductive coating includes at least one of carbon fiber, Ketjen black, acetylene black, carbon nanotubes and graphene.
  • the conductive coating can play the role of conducting electrons, and the charge transfer impedance is significantly reduced, thereby further improving the kinetic performance of the secondary battery.
  • the thickness of the conductive coating is 0.5 ⁇ m to 1.2 ⁇ m. In some embodiments, the thickness of the conductive coating is 0.6 ⁇ m, 0.7 ⁇ m, 0.8 ⁇ m, 0.9 ⁇ m, 1.0 ⁇ m, 1.1 ⁇ m or a range consisting of any two of these values.
  • the negative electrode current collector includes: copper foil, aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or any combination thereof.
  • the negative electrode active material layer further comprises a binder and a conductive agent.
  • the binder includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (ester) styrene-butadiene rubber, epoxy resin or nylon, etc.
  • the conductive agent includes, but is not limited to: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof.
  • the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof.
  • the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver.
  • the conductive polymer is a polyphenylene derivative.
  • the secondary battery of the present application further includes a positive electrode, the positive electrode includes a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode active material, a binder and a conductive agent.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • aluminum foil may be used.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer substrate.
  • the positive electrode active material includes at least one of lithium cobaltate, lithium nickel manganese cobaltate, lithium nickel manganese aluminum, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel lithium manganese oxide, spinel nickel manganese oxide and lithium titanate.
  • the binder includes a binder polymer, such as polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, modified polyvinylidene fluoride, modified SBR rubber or polyurethane.
  • the polyolefin binder includes at least one of polyethylene, polypropylene, polyolefin ester, polyolefin alcohol or polyacrylic acid.
  • the conductive agent includes a carbon-based material, such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black or carbon fiber; a metal-based material, such as metal powder or metal fiber of copper, nickel, aluminum, silver, etc.; a conductive polymer, such as a polyphenylene derivative; or a mixture thereof.
  • a carbon-based material such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black or carbon fiber
  • a metal-based material such as metal powder or metal fiber of copper, nickel, aluminum, silver, etc.
  • a conductive polymer such as a polyphenylene derivative
  • the secondary battery of the present application also includes a separator.
  • the material and shape of the separator used in the secondary battery of the present application are not particularly limited, and it can be any technology disclosed in the prior art.
  • the separator includes a polymer or inorganic substance formed of a material that is stable to the electrolyte of the present application.
  • the isolation film may include a substrate layer and a surface treatment layer.
  • the substrate layer is a non-woven fabric, a film or a composite film having a porous structure
  • the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide.
  • a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film may be selected.
  • a surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic substance.
  • the inorganic layer includes inorganic particles and a binder, and the inorganic particles are selected from at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate.
  • the binder is selected from at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acid salt, polyvinylpyrrolidone, polyethylene alkoxy, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
  • the polymer layer contains a polymer, and the material of the polymer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylic acid salt, polyvinylpyrrolidone, polyethylene alkoxy, polyvinylidene fluoride and poly (vinylidene fluoride-hexafluoropropylene).
  • the secondary of the present application also includes an electrolyte.
  • the electrolyte that can be used in the present application can be an electrolyte known in the prior art.
  • the electrolyte includes an organic solvent, a lithium salt and an optional additive.
  • the organic solvent in the electrolyte of the present application may be any organic solvent known in the prior art that can be used as a solvent for the electrolyte.
  • the electrolyte used in the electrolyte according to the present application is not limited, and it can be any electrolyte known in the prior art.
  • the additive of the electrolyte according to the present application may be any additive known in the prior art that can be used as an electrolyte additive.
  • the organic solvent includes, but is not limited to: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate or ethyl propionate.
  • the organic solvent includes an ether solvent, for example, including at least one of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME).
  • the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt.
  • the lithium salt includes, but is not limited to, lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium difluorophosphate (LiPO 2 F 2 ), lithium bis(trifluoromethanesulfonyl)imide LiN(CF 3 SO 2 ) 2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO 2 F) 2 )(LiFSI), lithium bis(oxalatoborate) LiB(C 2 O 4 ) 2 (LiBOB), or lithium di(oxalatoborate) LiBF 2 (C 2 O 4 )(LiDFOB).
  • the additive includes at least one of fluoroethylene carbonate and adiponitrile.
  • the secondary battery of the present application includes, but is not limited to: a lithium ion battery or a sodium ion battery. In some embodiments, the secondary battery includes a lithium ion battery.
  • the present application further provides an electronic device, which includes the secondary battery according to the second aspect of the present application.
  • the electronic equipment or device of the present application is not particularly limited.
  • the electronic equipment of the present application includes but is not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • the above-mentioned negative electrode material, binder styrene butadiene rubber (abbreviated as SBR), and thickener sodium carboxymethyl cellulose (abbreviated as CMC) are mixed in a weight ratio of 97:1.5:1.5, and then fully stirred and mixed in an appropriate amount of deionized water solvent to form a uniform negative electrode slurry; the slurry is coated on a current collector Cu foil with a conductive coating thickness of 1 ⁇ m, dried, and cold pressed to obtain a negative electrode sheet.
  • SBR binder styrene butadiene rubber
  • CMC thickener sodium carboxymethyl cellulose
  • Lithium cobalt oxide (chemical formula: LiCoO 2 ) is selected as the positive electrode active material, and is fully stirred and mixed with a conductive agent, acetylene black, and a binder, polyvinylidene fluoride (abbreviated as PVDF), in a proper amount of N-methylpyrrolidone (abbreviated as NMP) solvent at a weight ratio of 96.3:2.2:1.5 to form a uniform positive electrode slurry; the slurry is coated on a current collector Al foil, dried, and cold pressed to obtain a positive electrode sheet.
  • PVDF polyvinylidene fluoride
  • NMP N-methylpyrrolidone
  • the mass percentage of LiPF 6 was 12.5%
  • the mass percentage of fluoroethylene carbonate was 2%
  • the mass percentage of 1,3-propane sultone was 2%
  • the mass percentage of each substance was calculated based on the mass of the electrolyte.
  • the positive electrode, the separator (polyethylene porous polymer film), and the negative electrode are stacked in order so that the separator is between the positive electrode and the negative electrode to play an isolating role, and then wound to obtain an electrode assembly; after welding the pole ears, the electrode assembly is placed in an outer packaging foil aluminum-plastic film, and the prepared electrolyte is injected into the dried electrode assembly. After vacuum packaging, standing, formation, shaping, capacity testing and other processes, a soft-pack lithium-ion battery is obtained.
  • the preparation process of the negative electrode material is similar to that of Example 1, except that the corresponding negative electrode material is prepared by adjusting the ratio of the carbon-based material to PMMA, the rotation speed of the spheroidizing equipment, the carbonization temperature and the holding time in the preparation process.
  • the specific preparation parameters are shown in Table a:
  • the preparation process of the negative electrode material is similar to that of Example 6, except that the Id/Ig value of the negative electrode material is adjusted by adjusting the residual carbon ratio of the coated asphalt.
  • the residual carbon ratio of the coated asphalt is distributed as 14%, 12.5%, 3.5%, 6.5%, 9.5%, 11%, 5%, 8%, 15%, and 2%.
  • the preparation process of the negative electrode material is similar to that of Example 12, except that the La value of the negative electrode material is adjusted by adjusting the heating rate of the carbonization process.
  • the heating rates of the carbonization process are distributed as 9°C/min, 9.5°C/min, 4.5°C/min, 6.5°C/min, 8°C/min, 2.5°C/min, 10°C/min, 5°C/min, 8.5°C/min, and 1.5°C/min.
  • the preparation process of the negative electrode material is similar to that of Example 26, except that the specific surface area of the negative electrode material is adjusted by adjusting the asphalt coking value, the C004/C110 value of the negative electrode material is adjusted by adjusting the solid content of the CMC solution, and the compaction density of the negative electrode material is adjusted by adjusting the spheroidization time.
  • the preparation of the positive electrode, electrolyte and lithium-ion battery is the same as that in Example 26.
  • the obtained N2 adsorption-desorption curve is extracted according to the BJH model to obtain the BJH cumulative pore size volume distribution curve.
  • the adsorption volume corresponding to the pores in different pore size ranges can be obtained by calculation.
  • test standard for powder compaction density refers to GB/T 24533-2009 "Graphite Anode Materials for Lithium-ion Batteries”.
  • the specific test method is:
  • the test equipment is Sansi Zongheng UTM7305 with test tonnages of 0.3t, 0.5t, 0.75t, 1.0t, 1.5t, 2.0t, 2.5t, 3.0t, 4.0t, and 5.0t.
  • the pressure increase rate is 10mm/min
  • the pressure increase holding time is 30s
  • the pressure relief rate is 30mm/min
  • the pressure relief holding time is 10s.
  • the compacted density of powder is the compacted density measured at a test tonnage of 5t.
  • the particle size test method refers to GB/T 19077-2016.
  • the specific process is to weigh 1g of the negative electrode material sample and mix it with 20mL of deionized water and a trace amount of dispersant. After placing it in an ultrasonic device for 5 minutes, the solution is poured into the sampling system Hydro2000SM for testing.
  • the test equipment used is the Mastersizer 3000 produced by Malvern. During the test, when the laser beam passes through the dispersed particle sample, the particle size measurement is completed by measuring the intensity of the scattered light. The data is then used to analyze and calculate the particle size distribution that forms the scattering spectrum.
  • the particle size that starts from the small particle size side and reaches 50% of the volume accumulation is the Dv50 of the negative electrode material.
  • the refractive index of the particles used in the test is 1.8. One sample is tested three times, and the particle size is finally taken as the average of the three tests.
  • the negative electrode material was scanned using a laser microscopic confocal Raman spectrometer (Raman, HR Evolution, HORIBA Scientific Instrument Division) to obtain the g peak and g peak of all particles within the area.
  • the data was processed using LabSpec software to obtain the peak intensities of the d peak and g peak of each particle, which are Id and Ig, respectively.
  • the frequency of Id/Ig was counted with a step size of 0.02 to obtain a normal distribution diagram.
  • the (Id/Ig)max and (Id/Ig)min of these particles were counted, and the average Id/Ig was calculated, which is the Id/Ig value of the negative electrode active material.
  • the laser wavelength of the Raman spectrometer can be in the range of 532nm to 785nm.
  • d peak generally around 1350 cm -1 , caused by the radial breathing mode of the symmetric stretching vibration of the sp2 carbon atoms in the aromatic ring (structural defects);
  • g peak appears near 1580cm -1 , caused by the stretching vibration between sp2 carbon atoms, which corresponds to the vibration of E2g optical phonon in the center of the Brillouin zone (in-plane vibration of carbon atoms).
  • the negative electrode material was tested by X-ray powder diffractometer (XRD, instrument model: Bruker D8 ADVANCE) to obtain the XRD test curve, wherein the target material was Cu K ⁇ , the voltage/current was 40KV/40mA, the scanning angle range was 5° to 80°, the scanning step was 0.00836°, and the duration of each step was 0.3s.
  • XRD X-ray powder diffractometer
  • the diffraction peak of the (004) plane (the 004 peak in the XRD spectrum of the negative electrode material) is located at a diffraction angle 2 ⁇ range of 52°-57°
  • the diffraction peak of the (110) plane (the 110 peak in the XRD spectrum of the negative electrode material) is located at a diffraction angle 2 ⁇ range of 75°-80°.
  • the peak area value of the 004 peak calculated by integration is recorded as C004
  • the peak area value of the 110 peak calculated by integration is recorded as C110
  • the ratio of C004/C110 of the negative electrode material is calculated by this.
  • button cells The negative electrode, lithium sheet, separator, electrolyte, steel sheet, nickel foam and button cell shell prepared in the above embodiment were assembled together to obtain a button cell, which was left to stand for 6 h before testing.
  • test temperature is 25°C;
  • Table 1 shows the influence of the cumulative pore volume of the negative electrode material from 3nm to 35nm, the difference between the gram capacity Cap.A of the negative electrode material when it is discharged to -5mV and the gram capacity Cap.B when it is discharged to 5mV, Cap.A-Cap.B, on the performance of lithium-ion batteries.
  • the Id/Ig of the examples and comparative examples in Table 1 is 0.354
  • La is 114.1nm
  • BET is 12.4m2 /g
  • C004/C110 is 3.4.
  • Table 2 further studies the effect of the Id/Ig value of the negative electrode material on the performance of the lithium-ion battery based on Example 6.
  • Examples 11 to 20 all exhibit higher lithium-ion battery capacities. It is speculated that this is because the negative electrode material Id/Ig value is within a suitable range, its surface has more defects, more lithium ion embedding sites, and a larger lithium embedding capacity, so the active material capacity is high, which in turn enables the lithium-ion battery to exert good capacity performance.
  • Table 3 further studies the effect of the La value of the negative electrode material on the performance of lithium-ion batteries based on Example 12.
  • Table 4 further studies the effects of negative electrode material C004/C110, 5t compaction density, BET and Dv50 on the performance of lithium-ion batteries based on Example 26.
  • Examples 31-32 meet the range of 4 to 10 m2 /g for the BET of the negative electrode active material. It can be seen that compared with Example 26, its first effect is improved and the capacity of the lithium-ion battery is also improved.
  • the compaction density of the 5T pressure relief powder of Examples 33-34 meets the range of 1.8 to 2.1 g/cc. It can be seen that compared with Example 26, the higher the compaction density, the higher the capacity of the lithium-ion battery.
  • Examples 35-36 are negative electrode active material materials whose Dv50 meets the range of 10 to 20 ⁇ m.
  • Example 26 It can be seen that within this range, the gram capacity is improved compared with Example 26, and at the same time, the lithium-ion battery capacity is also improved.
  • the negative electrode active material C004/C110 of Examples 37-38 is in the range of 1 to 3. It can be seen that the capacity of the lithium-ion battery is improved to a certain extent compared with Example 26.
  • Examples 39-44 are negative electrode active material materials that simultaneously meet BET, 5T pressure relief powder, Dv50 and C004/C110 ratio. It can be found that the capacity of the lithium-ion battery is significantly improved, which indicates that the above-mentioned limiting conditions for the active material can further improve the performance of the battery.

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Abstract

提供一种负极材料，其包括碳基材料，其中，通过氮气吸附脱附测试，该负极材料满足：0.004cm3/g≤S≤0.030cm3/g，S为负极材料中孔径为3nm至35nm的孔的吸附体积，且使用以锂作为负极、以该负极材料作为正极的扣式电池进行充放电测试，扣式电池放电至-5mV时，负极材料的克容量为Cap.A，扣式电池放电至5mV时，负极材料的克容量为Cap.B，其中，10mAh/g≤Cap.A-Cap.B≤20mAh/g。本申请的负极材料的具有高的克容量，进而能够有效提升包括该负极材料的二次电池的能量密度。

Description

负极材料、二次电池和电子装置 技术领域
本申请涉及储能领域，具体涉及一种负极材料、二次电池和电子装置。
背景技术
随着电化学装置如锂离子电池成为广泛应用的能源系统，其快速充放电应用已成为一个重要的研究方向。因此，开发具有优越充放电性能的能源系统对其在交通工具、电网、风能和太阳能系统中的大规模应用至关重要。
但快速充放电会带来一些问题。如在大倍率充放电时，由于电池本身内阻的存在，导致在充放电过程中温度快速上升，对其循环和安全性能带来巨大的损害。现有技术改善电池阻抗主要是通过降低极片的涂布厚度及减小负极活性材料的粒度，但这种方式会明显的降低电池的能量密度，降低电芯的续航能力，且成本高。因此，开发内阻低且能量密度高的负极材料十分必要。
发明内容
鉴于现有技术存在的上述问题，本申请提供一种负极材料及包括该负极材料的二次电池，以提高负极材料的容量，进而提升包括该负极材料的二次电池的能量密度。
在第一方面，本申请提供一种负极材料，其包括碳基材料，通过氮气吸附脱附测试，该负极材料满足：0.004cm 3/g≤S≤0.030cm 3/g，S为负极材料中孔径为3nm至35nm的孔的吸附体积，且使用以锂作为负极、以负极材料作为正极的扣式电池进行充放电测试，扣式电池放电至-5mV时，该负极材料的克容量为Cap.A，扣式电池放电至5mV时，该负极材料的克容量为Cap.B，其中，10mAh/g≤Cap.A-Cap.B≤20mAh/g。3nm至35nm的孔的吸附体积可以表征负极材料结构中介孔的数量的多少。吸附体积越大，表明其介孔比例越高，负极材料中孔隙越多，进而可以增加活性离子的吸附嵌锂，提升负极材料的容量。但过多的孔隙会对二次电池的首效、循环等性能产生不利影响。负极材料在Cap.A-Cap.B值与负极材料的缺陷嵌锂相关，本申请通过将负极材料的3nm至35nm的孔的吸附体积与Cap.A-Cap.B值控制在上述范围内，能够进一步提升负极材料的吸附嵌锂和缺陷嵌锂容量， 提高二次电池的容量。在一些实施方式中，0.006cm 3/g≤S≤0.025cm 3/g。在一些实施方式中，14mAh/g≤Cap.A-Cap.B≤18mAh/g。
在一些实施方式中，通过拉曼测试，负极材料满足：0.2≤Id/Ig≤0.5，其中，Id为拉曼光谱中1350cm -1峰的强度，Ig为拉曼光谱中1580cm -1处峰的强度。Id/Ig比值可以表征负极材料的缺陷度，其值越大，表明缺陷度越高。高的缺陷度可以增加活性离子的脱嵌通道，提高活性离子的脱嵌速度，从而提高负极材料的动力学性能。但过多的缺陷会导致二次电池的首效、循环、储存等性能降低。Id/Ig比值在上述范围内时，二次电池既能表现出良好的动力学，其首效循环等性能也不会明显降低。在一些实施方式中，0.3≤Id/Ig≤0.5。
在一些实施方式中，通过X射线衍射法测试，负极材料沿a轴方向的平均堆积厚度为La，100nm≤La≤140nm。La表示负极材料晶体沿a轴方向的平均大小。La值越大，负极材料的嵌锂和储锂量就越高，相应地其克容量越高。但La值过高时，虽然负极材料的克容量变大，但其循环性能会降低。本申请负极材料的La值在上述范围内，负极材料具有高克容量的同时循环性能不会明显降低。在一些实施方式中，110nm≤La≤140nm。
在一些实施方式中，负极材料的比表面积为2cm 2/g至15cm 2/g。负极材料的比表面积越小，其与电解液接触的面积也越小，从而使得二次电池在首次形成SEI膜时所消耗的活性离子减少，首效增高。但比表面积过小时，电解液浸润和活性扩散变得困难，从而影响二次电池的动力学性能。本申请的负极材料的比表面积在上述范围内，二次电池既具有高的首效，其动力学性能也不会明显降低。在一些实施方式中，负极材料的比表面积为4cm 2/g至10cm 2/g。
在一些实施方式中，负极材料的5t粉末压实密度为1.7g/cm 3至2.2g/cm 3。粉末压实密度代表负极材料在压制时可以被压缩的程度，该值越大，代表压制时可以压缩的更多，相应的二次电池的体积能量密度就越高。本申请负极材料的粉末压实密度在上述范围内，包括该负极材料的二次电池具有高的能量密度。在一些实施方式中，负极材料的5t粉末压实密度为1.8g/cm 3至2.1g/cm 3。
在一些实施方式中，负极材料的Dv50满足：5μm≤Dv50≤26μm。负极材料的Dv50越大，相应的克容量越大，但过大会影响其动力学性能。本申请负极材料的Dv50在上述范围内，既能保证负极材料具有较高的克容量，又能保证动力学性能不显著降低。在一些实施方式中，10μm≤Dv50≤20μm。
在一些实施方式中，通过X射线衍射法测试，负极材料的004晶面衍射峰面积C004 与110晶面衍射峰面积C110的比值满足1≤C004/C110≤5。C004/C110的比值是反映负极材料晶体取向度的一个参数，C004/C110值越大，晶体取向度越高，活性离子在负极材料中脱嵌的面就越局限，C004/C110越小，晶体取向度越低，活性离子可以在负极材料的多个方向进行脱嵌。本申请负极材料的C004/C110在上述范围内，活性离子可以快速在负极材料中脱嵌，从而进一步改善二次电池的放电倍率性能。在一些实施方式中，1≤C004/C110≤3。
在一些实施方式中，碳基材料的制备方法包括：将天然石墨或人造石墨中的一种或多种进行石墨复合材料制备、球化处理、包覆处理和碳化处理。
在一些实施方式中，石墨复合材料的制备过程包括将天然石墨和人造石墨中的一种或多种与聚甲基丙烯酸甲酯(PMMA)同时溶解在N-N二甲基甲酰胺(DMF)中，在50℃至80℃温度下搅拌10h至14h，过滤收集沉淀物，用去离子水和乙醇洗涤2至4次，60℃至90℃温度下完全干燥得到石墨复合材料前驱体；将石墨复合材料前驱体在管式炉中以8℃/min至16℃/min的升温速率加热至1000℃至1200℃，接着在管式炉中通入
CH 4/C 2H 2/H 2混合气(比例分别为5～10:5～10:80～85)，保持8h至12h后自然冷却至室温，从而得到石墨复合材料。
在一些实施方式中，球形化处理过程包括：对包含石墨复合材料与分散剂溶液的混合物施加来自转盘、内壁以及颗粒之间连续的冲击力、压缩力和剪断力，使得石墨复合材料球形化。在一些实施方式中，球化的时间为10min至20min。在一些实施方式中，通过使用球形化装置对混合物施加冲击力、压缩力和剪断力，从而进行混合物的碰撞、摩擦、剪切和弯曲折叠，由此，去除石墨复合材料棱角同时达到微粉固定到大颗粒上的效果。在一些实施方式中，球形化装置为混合造粒机。在一些实施方式中，球形化装置的转速为30Hz至50Hz。
在一些实施方式中，分散剂溶液为羧甲基纤维素(CMC)的水溶液。在一些实施方式中，分散剂溶液中羧甲基纤维素的质量含量为0.5％至2％。在一些实施方式中，基于石墨复合材料的质量，分散剂溶液的质量含量为5％至20％。
在一些实施方式中，包覆处理过程包括：采用沥青对球化后的石墨复合材料进行包覆处理。在一些实施方式中，基于球化后的石墨复合材料的质量，沥青的质量含量为2％至15％。在一些实施方式中，碳化处理的温度为900℃至1500℃。
在第二方面，本申请提供了一种二次电池，其包括负极，负极包括负极集流体和设置 在负极集流体的至少一个表面上的负极活性材料层，其中，负极活性材料层包括第一方面的负极材料。
在一些实施方式中，负极还包括位于负极活性材料层和负极集流体之间的导电涂层。在一些实施方式中，导电涂层包括碳纤维、科琴黑、乙炔黑、碳纳米管和石墨烯中的至少一种。导电涂层能够起到传导电子的作用，电荷转移阻抗显著降低，进而能够进一步提升二次电池的动力学性能。在一些实施方式中，导电涂层的厚度为0.5μm至1.2μm。
在第三方面，本申请提供了一种电子装置，其包括第二方面的二次电池。
附图说明
图1示出了本申请实施例6和对比例1的锂离子电池的容量。
具体实施方式
为了简明，本申请仅具体地公开了一些数值范围。然而，任意下限可以与任何上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，每个单独公开的点或单个数值自身可以作为下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
在本申请的描述中，除非另有说明，“以上”、“以下”包含本数。
除非另有说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。除非另有说明，本申请中提到的各参数的数值可以用本领域常用的各种测量方法进行测量(例如，可以按照在本申请的实施例中给出的方法进行测试)。
术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个组分或多个组分。项目B可包含单个组分或多个组分。项目C可包含单个组分或多个组分。
下面结合具体实施方式，进一步阐述本申请。应理解，这些具体实施方式仅用于说明本申请而不用于限制本申请的范围。
一、负极材料
本申请提供的负极材料包括碳基材料，通过氮气吸附脱附测试，该负极材料满足：0.004cm 3/g≤S≤0.030cm 3/g，S为负极材料中孔径为3nm至35nm的孔的吸附体积，且使用以锂作为负极、以负极材料作为正极的扣式电池进行充放电测试，扣式电池放电至-5mV时，该负极材料的克容量为Cap.A，扣式电池放电至5mV时，该负极材料的克容量为Cap.B，其中，10mAh/g≤Cap.A-Cap.B≤20mAh/g。3nm至35nm的孔的吸附体积可以表征负极材料结构中介孔的数量的多少。吸附体积越大，表明其介孔比例越高，负极材料中孔隙越多，进而可以增加活性离子的吸附嵌锂，提升负极材料的容量。但过多的孔隙会对二次电池的首效、循环等性能产生不利影响。负极材料在Cap.A-Cap.B值与负极材料的缺陷嵌锂相关，本申请通过将负极材料的3nm至35nm的孔的吸附体积与Cap.A-Cap.B值控制在上述范围内，能够进一步提升负极材料的吸附嵌锂和缺陷嵌锂容量，提高二次电池的容量。在一些实施方式中，S为0.005cm 3/g、0.008cm 3/g、0.01cm 3/g、0.011cm 3/g、0.012cm 3/g、0.013cm 3/g、0.014cm 3/g、0.015cm 3/g、0.016cm 3/g、0.017cm 3/g、0.018cm 3/g、0.019cm 3/g、0.02cm 3/g、0.021cm 3/g、0.022cm 3/g、0.023cm 3/g、0.024cm 3/g、0.025cm 3/g、0.026cm 3/g、0.027cm 3/g、0.028cm 3/g、0.029cm 3或这些值中任意两者组成的范围。在一些实施方式中，0.006cm 3/g≤S≤0.025cm 3/g。
在一些实施方式中，Cap.A-Cap.B为10.5mAh/g、11mAh/g、11.5mAh/g、12mAh/g、12.5mAh/g、13mAh/g、13.5mAh/g、14.5mAh/g、15mAh/g、15.5mAh/g、16mAh/g、16.5mAh/g、17mAh/g、17.5mAh/g、18.5mAh/g、19mAh/g、19.5mAh/g或这些值中任意两者组成的范围。在一些实施方式中，14mAh/g≤Cap.A-Cap.B≤18mAh/g。
本申请所采用的扣式电池的组成如下：
负极：锂片作为负极。
正极：97wt％石墨、1.5wt％羧甲基纤维素钠(CMC)和1.5wt％丁苯橡胶(SBR)作为正极活性材料层，铜箔作为集流体。
电解液：12.5wt％LiPF 6，溶剂为质量比为1:3:3:3的碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸甲乙酯(EMC)和碳酸二乙酯(DEC)并加入2wt％氟代碳酸乙烯酯和2wt％1,3-丙烷磺内酯。
本申请使用的扣式电池进行充放电测试流程如下：
将扣式电池置于蓝电测试仪上进行测试，测试流程为在0.05C下放电至-5mv，静置5min，在0.05mA下放电至-5mv，在0.01mA下放电至-5mv，在0.1C下充电至2.0V即 可得充电容量，最后除以活性物质重量即可得负极材料的克容量Cap.A。充电容量比上放电容量可得首次效率。
将扣式电池置于蓝电测试仪上进行测试，测试流程为在0.05C下放电至5mv，静置5min，在0.05mA下放电至5mv，在0.01mA下放电至5mv，在0.1C下充电至2.0V即可得充电容量，最后除以活性物质重量即可得负极材料的克容量Cap.B。充电容量比上放电容量可得首次效率。
在一些实施方式中，通过拉曼测试，负极材料满足：0.2≤Id/Ig≤0.5，其中，Id为拉曼光谱中1350cm -1峰的强度，Ig为拉曼光谱中1580cm -1处峰的强度。Id/Ig比值可以表征负极材料的缺陷度，其值越大，表明缺陷度越高。高的缺陷度可以增加活性离子的脱嵌通道，提高活性离子的脱嵌速度，从而提高负极材料的动力学性能。但过多的缺陷会导致二次电池的首效、循环、储存等性能降低。Id/Ig比值在上述范围内时，二次电池既能表现出良好的动力学，其首效循环等性能也不会明显降低。在一些实施方式中，Id/Ig为0.23、0.25、0.27、0.29、0.33、0.35、0.37、0.4、0.43、0.45、0.47或这些值中任意两者组成的范围。在一些实施方式中，0.3≤Id/Ig≤0.5。
在一些实施方式中，通过X射线衍射法测试，负极材料沿a轴方向的平均堆积厚度为La，100nm≤La≤140nm。La表示负极材料晶体沿a轴方向的平均大小。La值越大，负极材料的嵌锂和储锂量就越高，相应地其克容量越高。但La值过高时，虽然负极材料的克容量变大，但其循环性能会降低。本申请负极材料的La值在上述范围内，负极材料具有高克容量的同时循环性能不会明显降低。在一些实施方式中，La为100nm、103nm、105nm、107nm、110nm、113nm、115nm、117nm、120nm、123nm、125nm、127nm、130nm、133nm、135nm、137nm或这些值中任意两者组成的范围。在一些实施方式中，110nm≤La≤140nm。
在一些实施方式中，负极材料的比表面积为2cm 2/g至15cm 2/g。负极材料的比表面积越小，其与电解液接触的面积也越小，从而使得二次电池在首次形成SEI膜时所消耗的活性离子减少，首效增高。但比表面积过小时，电解液浸润和活性扩散变得困难，从而影响二次电池的动力学性能。本申请的负极材料的比表面积在上述范围内，二次电池既具有高的首效，其动力学性能也不会明显降低。在一些实施方式中，负极材料的比表面积为3cm 2/g、4.5cm 2/g、5cm 2/g、5.5cm 2/g、6cm 2/g、6.5cm 2/g、7cm 2/g、7.5cm 2/g、8cm 2/g、8.5cm 2/g、9cm 2/g、9.5cm 2/g或这些值中任意两者组成的范围。在一些实施方式中，负极材料的比表面积为4cm 2/g至10cm 2/g。
在一些实施方式中，负极材料的5t粉末压实密度为1.7g/cm 3至2.2g/cm 3。粉末压实密度代表负极材料在压制时可以被压缩的程度，该值越大，代表压制时可以压缩的更多，相应的二次电池的体积能量密度就越高。本申请负极材料的粉末压实密度在上述范围内，包括该负极材料的二次电池具有高的能量密度。在一些实施方式中，负极材料的5t粉末压实密度为1.72g/cm 3、1.74g/cm 3、1.76g/cm 3、1.78g/cm 3、1.82g/cm 3、1.84g/cm 3、1.86g/cm 3、1.88g/cm 3、1.9g/cm 3、1.92g/cm 3、1.94g/cm 3、1.96g/cm 3、1.98g/cm 3、2.0g/cm 3、2.02g/cm 3、2.04g/cm 3、2.06g/cm 3、2.08g/cm 3、2.12g/cm 3、2.14g/cm 3、2.16g/cm 3、2.18g/cm 3或这些值中任意两者组成的范围。在一些实施方式中，负极材料的5t粉末压实密度为1.8g/cm 3至2.1g/cm 3。
在一些实施方式中，负极材料的Dv50满足：5μm≤Dv50≤26μm。负极材料的Dv50越大，相应的克容量越大，但过大会影响其动力学性能。在一些实施方式中，Dv50为6μm、8μm、11μm、12μm、13μm、14μm、15μm、16μm、17μm、18μm、19μm、21μm、22μm、23μm、24μm、25μm或这些值中任意两者组成的范围。本申请负极材料的Dv50在上述范围内，既能保证负极材料具有较高的克容量，又能保证动力学性能不显著降低。在一些实施方式中，10μm≤Dv50≤20μm。本申请中，Dv50表示负极材料在体积基准的粒度分布中，50％的颗粒粒径小于该值。
在一些实施方式中，通过X射线衍射法测试，负极材料的004晶面衍射峰面积C004与110晶面衍射峰面积C110的比值满足1≤C004/C110≤5。C004/C110的比值是反映负极材料晶体取向度的一个参数，C004/C110值越大，晶体取向度越高，活性离子在负极材料中脱嵌的面就越局限，C004/C110越小，晶体取向度越低，活性离子可以在负极材料的多个方向进行脱嵌。本申请负极材料的C004/C110在上述范围内，活性离子可以快速在负极材料中脱嵌，从而进一步改善二次电池的放电倍率性能。在一些实施方式中，C004/C110为1.2、1.4、1.6、1.8、2.3、2.5、2.7、3.0、3.3、3.5、3.7、4.0、4.3、4.5、4.7、或这些值中任意两者组成的范围。在一些实施方式中，1≤C004/C110≤3。
在一些实施方式中，碳基材料的制备方法包括：将天然石墨和人造石墨中的一种或多种进行石墨复合材料制备、球形化处理、包覆处理和碳化处理。
在一些实施方式中，石墨复合材料的制备过程包括将天然石墨和人造石墨中的一种或多种与聚甲基丙烯酸甲酯(PMMA)同时溶解在N-N二甲基甲酰胺(DMF)中，在50℃至80℃温度下搅拌10h至14h，过滤收集沉淀物，用去离子水和乙醇洗涤2至4次，60℃至90℃温度下完全干燥得到石墨复合材料前驱体；将石墨复合材料前驱体在管式炉中以8℃ /min至16℃/min的升温速率加热至1000℃至1200℃，接着在管式炉中通入CH 4/C 2H 2/H 2混合气(比例分别为5～10:5～10:80～85)，保持8h至12h后自然冷却至室温，从而得到石墨复合材料。
在一些实施方式中，球形化处理过程包括：对包含石墨复合材料与分散剂溶液的混合物施加来自转盘、内壁以及颗粒之间连续的冲击力、压缩力和剪断力，使得石墨复合材料球形化。在一些实施方式中，球化的时间为10min至20min，例如为12min、14min、16min或18min。在一些实施方式中，通过使用球形化装置对混合物施加冲击力、压缩力和剪断力，从而进行混合物的碰撞、摩擦、剪切和弯曲折叠，由此，去除石墨复合材料棱角同时达到微粉固定到大颗粒上的效果。在一些实施方式中，球形化装置为混合造粒机。在一些实施方式中，球形化装置的转速为30Hz至50Hz，例如为35Hz、40Hz或45Hz。
在一些实施方式中，分散剂溶液为羧甲基纤维素(CMC)的水溶液。在一些实施方式中，分散剂溶液中羧甲基纤维素的质量含量为0.5％至2％，例如为0.7％、1.0％、1.3％、1.5％或1.7％。在一些实施方式中，基于石墨复合材料的质量，分散剂溶液的质量含量为5％至20％，例如为7％、10％、13％、15％、17％或19％。
在一些实施方式中，包覆处理过程包括：采用沥青对球化后的石墨复合材料进行包覆处理。在一些实施方式中，基于球化后的石墨复合材料的质量，沥青的质量含量为2％至15％，例如为3％、4％、5％、6％、7％、8％、9％、10％、11％、12％、13％或14％。在一些实施方式中，碳化处理的温度为900℃至1500℃，例如为950℃、1000℃、1050℃、1100℃、1150℃、1200℃、1250℃、1300℃、1350℃、1400℃或1450℃。在一些实施方式中，碳化的时间为3h至10h，例如为4h、5h、6h、7h、8h或9h。
二、二次电池
本申请提供的二次电池包括负极，负极包括负极集流体和设置在负极集流体的至少一个表面上的负极活性材料层，其中，负极活性材料层包括第一方面的负极材料。
在一些实施方式中，负极还包括位于负极活性材料层和负极集流体之间的导电涂层。在一些实施方式中，导电涂层包括碳纤维、科琴黑、乙炔黑、碳纳米管和石墨烯中的至少一种。导电涂层能够起到传导电子的作用，电荷转移阻抗显著降低，进而能够进一步提升二次电池的动力学性能。在一些实施方式中，导电涂层的厚度为0.5μm至1.2μm。在一些实施方式中，导电涂层的厚度为0.6μm、0.7μm、0.8μm、0.9μm、1.0μm、1.1μm或这些值中任意两者组成的范围。
在一些实施方式中，负极集流体包括：铜箔、铝箔、镍箔、不锈钢箔、钛箔、泡沫镍、 泡沫铜、覆有导电金属的聚合物基底或其任意组合。
在一些实施方式中，负极活性材料层还包括粘结剂和导电剂。在一些实施方式中，粘结剂包括，但不限于：聚乙烯醇、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1，1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂或尼龙等。
在一些实施方式中，导电剂包括，但不限于：基于碳的材料、基于金属的材料、导电聚合物和它们的混合物。在一些实施例中，基于碳的材料选自天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维或其任意组合。在一些实施例中，基于金属的材料选自金属粉、金属纤维、铜、镍、铝或银。在一些实施例中，导电聚合物为聚亚苯基衍生物。
本申请的二次电池还包括正极，正极包括正极集流体和正极活性材料层，正极活性材料层包括正极活性材料、粘结剂和导电剂。
根据本申请的一些实施方式，正极集流体可以采用金属箔片或复合集流体。例如，可以使用铝箔。复合集流体可以通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子基材上而形成。
根据本申请的一些实施方式，正极活性材料包括钴酸锂、镍锰钴酸锂、镍锰铝酸锂、磷酸铁锂、磷酸钒锂、磷酸钴锂、磷酸锰锂、磷酸锰铁锂、硅酸铁锂、硅酸钒锂、硅酸钴锂、硅酸锰锂、尖晶石型锰酸锂、尖晶石型镍锰酸锂和钛酸锂中的至少一种。在一些实施例中，粘结剂包括粘合剂聚合物，例如聚偏氟乙烯、聚四氟乙烯、聚烯烃类、羧甲基纤维素钠、羧甲基纤维素锂、改性聚偏氟乙烯、改性SBR橡胶或聚氨酯中的至少一种。在一些实施例中，聚烯烃类粘结剂包括聚乙烯、聚丙烯、聚烯酯、聚烯醇或聚丙烯酸中的至少一种。在一些实施例中，导电剂包括碳基材料，例如天然石墨、人造石墨、炭黑、乙炔黑、科琴黑或碳纤维；金属基材料，例如铜、镍、铝、银等的金属粉或金属纤维；导电聚合物，例如聚亚苯基衍生物；或它们的混合物。
本申请的二次还包括隔离膜，本申请的二次电池中使用的隔离膜的材料和形状没有特别限制，其可为任何现有技术中公开的技术。在一些实施例中，隔离膜包括由对本申请的电解液稳定的材料形成的聚合物或无机物等。
例如隔离膜可包括基材层和表面处理层。基材层为具有多孔结构的无纺布、膜或复合膜，基材层的材料选自聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯和聚酰亚胺中的至少一种。具体的，可选用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯- 聚乙烯-聚丙烯多孔复合膜。
基材层的至少一个表面上设置有表面处理层，表面处理层可以是聚合物层或无机物层，也可以是混合聚合物与无机物所形成的层。无机物层包括无机颗粒和粘结剂，无机颗粒选自氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙和硫酸钡中的至少一种。粘结剂选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯烷氧、聚甲基丙烯酸甲酯、聚四氟乙烯和聚六氟丙烯中的至少一种。聚合物层中包含聚合物，聚合物的材料选自聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯烷氧、聚偏氟乙烯、聚(偏氟乙烯-六氟丙烯)中的至少一种。
本申请的二次还包括电解液。可用于本申请的电解液可以为现有技术中已知的电解液。
根据本申请的一些实施方式，电解液包括有机溶剂、锂盐和可选的添加剂。本申请的电解液中的有机溶剂可为现有技术中已知的任何可作为电解液的溶剂的有机溶剂。根据本申请的电解液中使用的电解质没有限制，其可为现有技术中已知的任何电解质。根据本申请的电解液的添加剂可为现有技术中已知的任何可作为电解液添加剂的添加剂。在一些实施例中，有机溶剂包括，但不限于：碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸二甲酯(DMC)、碳酸亚丙酯或丙酸乙酯。在一些实施例中，有机溶剂包括醚类溶剂，例如包括1，3-二氧五环(DOL)和乙二醇二甲醚(DME)中的至少一种。在一些实施例中，锂盐包括有机锂盐或无机锂盐中的至少一种。在一些实施例中，锂盐包括，但不限于：六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、二氟磷酸锂(LiPO 2F 2)、双三氟甲烷磺酰亚胺锂LiN(CF 3SO 2) 2(LiTFSI)、双(氟磺酰)亚胺锂Li(N(SO 2F) 2)(LiFSI)、双草酸硼酸锂LiB(C 2O 4) 2(LiBOB)或二氟草酸硼酸锂LiBF 2(C 2O 4)(LiDFOB)。在一些实施例中，添加剂包括氟代碳酸乙烯酯和己二腈中的至少一种。
根据本申请的一些实施方式，本申请的二次电池包括，但不限于：锂离子电池或钠离子电池。在一些实施例中，二次电池包括锂离子电池。
三、电子装置
本申请进一步提供了一种电子装置，其包括本申请第二方面的二次电池。
本申请的电子设备或装置没有特别限定。在一些实施例中，本申请的电子设备包括但 不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
在下述实施例及对比例中，所使用到的试剂、材料以及仪器如没有特殊的说明，均可商购获得。
实施例及对比例
实施例1
负极材料制备
选取95g人造石墨，与5g的聚甲基丙烯酸甲酯(PMMA)溶解在100mL N-N二甲基甲酰胺(DMF)，在70℃下搅拌12h。过滤以收集沉淀物，将沉淀物用去离子水和乙醇洗涤2次，80℃完全干燥得到石墨复合材料前驱体；在管式炉中以10℃/min的升温速率加热至1100℃，然后在管式炉中通入CH 4/C 2H 2/H 2混合气(比例分别为5:10:85)，保持10h后自然冷却至室温，从而得到最终的石墨复合材料，将石墨复合材料与10％比例的固含量为1％的CMC水溶液混合，在球形化设备转速为40Hz下球化15分钟，球化后采用5％的沥青进行包覆处理，最后将包覆混合物以5℃/min的速率加热到1000℃，保温5h，保温后自然冷却到室温，即可得到碳基材料，即负极材料。
负极的制备
将上述负极材料、粘结剂丁苯橡胶(简写为SBR)、增稠剂羧甲基纤维素钠(简写为CMC)按照重量比97∶1.5∶1.5配比，再用适量的去离子水溶剂中充分搅拌混合，使其形成均匀的负极浆料；将此浆料涂覆于导电涂层厚度为1μm的集流体Cu箔上，烘干、冷压，即可得到负极极片。
正极的制备
选取钴酸锂(化学式：LiCoO 2)为正极活性材料，将其与导电剂乙炔黑、粘结剂聚偏二氟乙烯(简写为PVDF)按重量比96.3∶2.2∶1.5在适量的N-甲基吡咯烷酮(简写为NMP)溶剂中充分搅拌混合，使其形成均匀的正极浆料；将此浆料涂覆于集流体Al箔上，烘干、冷压，得到正极极片。
电解液的制备
在干燥的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照质量比为EC:EMC:DEC＝1:3:3:3进行混合，接着加入氟代碳酸乙烯酯和1,3-丙烷磺内酯，溶解并充分搅拌后加入锂盐LiPF 6，混合均匀后得到电解液。其中，LiPF 6的质量百分含量为12.5％，氟代碳酸乙烯酯的质量百分含量为2％，1,3-丙烷磺内酯的质量百分含量为2％，各物质的质量百分含量为基于电解液的质量计算得到。
锂离子电池的制备
将正极、隔离膜(聚乙烯多孔聚合物薄膜)、负极按顺序叠好，使隔离膜处于正极和负极之间起到隔离的作用，然后卷绕得到电极组件；焊接极耳后将电极组件置于外包装箔铝塑膜中，将上述制备好的电解液注入到干燥后的电极组件中，经过真空封装、静置、化成、整形、容量测试等工序，获得软包锂离子电池。
实施例2至实施例10、对比例1至对比例3
负极材料制备
负极材料的制备过程与实施例1类似，不同之处在于通过调整制备过程中的碳基材料与PMMA比例、球化设备转速、碳化温度和保温时间等参数来制备相应的负极材料。具体制备参数如表a所示：
表a
Figure PCTCN2022123059-appb-000001
正极、电解液以及锂离子电池的制备同实施例1。
实施例11至实施例20
负极材料制备
负极材料的制备过程与实施例6类似，不同之处在于通过调整包覆沥青残碳比例来调整负极材料的Id/Ig值。实施例11至实施例20的制备过程中，包覆沥青残碳比例分布为14％、12.5％、3.5％、6.5％、9.5％、11％、5％、8％、15％、2％。
正极、电解液以及锂离子电池的制备同实施例6。
实施例21至实施例30
负极材料制备
负极材料的制备过程与实施例12类似，不同之处在于通过调整碳化过程的升温速率来调整负极材料的La值。实施例21-30的制备过程中，碳化过程的升温速率分布为9℃/min、9.5℃/min、4.5℃/min、6.5℃/min、8℃/min、2.5℃/min、10℃/min、5℃/min、8.5℃/min、1.5℃/min。
正极、电解液以及锂离子电池的制备同实施例12。
实施例31至实施例44
负极材料的制备过程与实施例26类似，不同之处在于通过调整沥青结焦值来调整负极材料的比表面积，通过调整CMC溶液的固含量来调整负极材料的C004/C110值，通过调整球形化时间来调整负极材料的压实密度。
正极、电解液以及锂离子电池的制备同实施例26。
测试方法
1、负极材料孔径分布测试
1)称取20至30g负极材料样品进行压片，压片后称取1.5至3.5g装入测试样品管中；
2)将样品在200℃条件脱气处理2h；
3)然后通入高纯氮气，使样品在液氮温度环境吸附氮气直至吸附饱和；
4)将所得N 2吸脱附曲线按照BJH模型提取数据，得BJH累积孔径体积分布曲线，通过计算可得不同孔径范围内的孔对应的吸附体积。
2、负极材料粉末压实密度测试
粉末压实密度的测试标准参照GB/T 24533-2009《锂离子电池石墨类负极材料》。具体测试方法为：
称量1.0000±0.0500g的负极材料样品置于测试模具(CARVER#3619(13mm)中，然后将样品置于测试设备中，测试设备为三思纵横UTM7305测试吨位0.3t、0.5t、0.75t、1.0t、1.5t、2.0t、2.5t、3.0t、4.0t、5.0t，升压速率为10mm/min，升压保持时间为30s，泄压速率为30mm/min，泄压保持时间为10s。
本申请中，粉末压实密度均为测试吨位为5t测得的压实密度。压实密度的计算公式为：压实密度＝材料质量/(材料受力面积×样品的厚度)。
3、负极材料颗粒粒度测试
颗粒粒度测试方法参照GB/T 19077-2016。具体流程为称量负极材料样品1g与20mL去离子水和微量分散剂混合均匀，置于超声设备中超声5min后将溶液倒入进样系统Hydro2000SM中进行测试，所用测试设备为马尔文公司生产的Mastersizer 3000。测试过程中当激光束穿过分散的颗粒样品时，通过测量散射光的强度来完成粒度测量。然后数据用于分析计算形成该散射光谱图的颗粒粒度分布，在负极材料在体积基准的粒度分布中，从小粒径侧起、达到体积累积50％的粒径即为负极材料的Dv50。测试所用颗粒折射率为1.8，一个样品测试三次，颗粒粒度最终取三次测试的平均值。
4、负极材料拉曼测试
利用激光显微共聚焦拉曼光谱仪(Raman，HR Evolution，HORIBA科学仪器事业部)扫描负极材料，得到该面积范围内所有颗粒的g峰和g峰，采用LabSpec软件对数据进行处理得到每一个颗粒的d峰和g峰的峰强，分别为Id和Ig，Id/Ig以0.02为步长统计Id/Ig的频次得到正态分布图，统计这些颗粒的(Id/Ig)max、(Id/Ig)min，计算Id/Ig平均值，即为负极活性材料的Id/Ig值。拉曼光谱仪的激光波长可处于532nm至785nm的范围内。
d峰：一般在1350cm -1附近，由芳香环中sp2碳原子的对称伸缩振动径向呼吸模式引起(结构缺陷)；
g峰：出现在1580cm -1附近，由sp2碳原子间的拉伸振动引起，它对应布里渊区中心的E2g光学声子的振动(碳原子面内振动)。
5、负极材料XRD测试
采用X射线粉末衍射仪(XRD，仪器型号:Bruker D8 ADVANCE)测试负极材料得到XRD测试曲线，其中，靶材为Cu Kα，电压/电流为40KV/40mA，扫描角度范围为5°至80°，扫描步长为0.00836°，每步长时间为0.3s。
其中，(004)面的衍射峰(负极材料的XRD图谱中004峰)位于衍射角2θ的范围为52°-57°处，(110)面的衍射峰(负极材料的XRD图谱中110峰)位于衍射角2θ的范围为 75°-80°处。积分计算004峰的峰面积值记为C004，积分计算110峰的峰面积值记为C110，以此计算负极材料的C004/C110的比值。
6、克容量和首效测试
(1)扣式电池的制备：使用上述实施例中制备的负极，锂片，隔离膜，电解液，钢片，泡沫镍以及扣式电池壳组装在一起得到扣式电池，测试前静置6h。
(2)将扣式电池置于蓝电测试仪上进行测试，测试流程为在0.05C下放电至5mV或-5mV，静置5min，在0.05mA下放电至5mv或-5mV，在0.01mA下放电至5mv或-5mV，在0.1C下充电至2.0V即可得充电容量，最后除以活性物质重量即可得负极材料的克容量。充电容量比上放电容量可得首次效率。
7、锂离子电池容量测试
1)测试温度为25℃；
2)Rest 5min；
3)0.2C DC to 3V；
4)Rest 5min；
5)0.5C CC to 4.48V,CV to 0.025C；
6)Rest 5min；
7)0.2C DC to3V；
8)Rest 5min；
9)第5步到第8步循环2次；
10)调节炉温至45℃；
11)Rest 60min；
12)0.5C CC to4.48V,CV to 0.025C；
13)Rest 5min；
14)0.2C DC to 3.0V；
15)Rest 5min；
16)第12步到第15步循环2次；
测试结果
表1示出了负极材料的负极材料的3nm至35nm累计孔隙体积、负极材料的扣电放电到-5mV的克容量Cap.A与放电到5mV的克容量Cap.B的差值Cap.A-Cap.B的值对锂离子电池性能的影响。其中，表1中的实施例和对比例的Id/Ig为0.354，La为114.1nm， BET为12.4m 2/g，C004/C110为3.4。
表1
Figure PCTCN2022123059-appb-000002
从表1的数据可以看出，当锂离子电池负极材料满足在3nm至35nm的孔径范围内，其累计孔隙体积为4×10 -3cm 3/g至30×10 -3cm 3/g，同时其扣电放电到-5mV的克容量Cap.A与放电到5mV的克容量Cap.B的差值Cap.A-Cap.B的值为10mAh/g至20mAh/g时，电池表现出较高的锂离子电池容量。推测是因为具有该特征的石墨负极材料其可嵌锂位点显著增加，从而在放电过程中能够放出更多的容量，使得锂离子电池的能量密度提升。
表2在实施例6的基础上进一步研究了负极材料的Id/Ig值对锂离子电池性能的影响。
表2
Figure PCTCN2022123059-appb-000003
从表2的数据可以看出，实施例11至实施例20均表现出更高的锂离子电池容量。推测是因为负极材料Id/Ig值在合适的范围，其表面具有更多的缺陷，锂离子嵌入位点更多，嵌锂容量更大，因此活性物质容量高，进而使得锂离电池发挥出良好的容量性能。
表3在实施例12的基础上进一步研究了负极材料的La值对锂离子电池性能的影响。
表3
Figure PCTCN2022123059-appb-000004
从表3的数据可以看出，负极材料的La在110nm至140nm范围时，负极材料克容量Cap≥355mAh/g，同时锂离子电池放电容量能够进一步提升。
表4在实施例26的基础上进一步研究了负极材料的C004/C110、5t压实密度，BET以及Dv50对锂离子电池性能的影响。
表4
Figure PCTCN2022123059-appb-000005
Figure PCTCN2022123059-appb-000006
如表4所示，可以发现实施例36和39的锂离子电池容量是优于实施例26的。实施例31-32满足负极活性物BET的范围为4～10m 2/g，可以看到相比实施例26，其首效提高，锂离子电池容量也有所提升。实施例33-34的5T泄压粉末压实密度满足1.8～2.1g/cc范围，可以看到与实施例26相比，压实密度越高，锂离子电池容量越高。实施例35-36是负极活性物质材料的Dv50满足10至20μm范围，可以看到Dv50在此范围内，克容量相比实施例26提高，与此同时锂离子电池容量也提高。实施例37-38的负极活性物质材料C004/C110在1至3范围内，可以看到锂离子电池容量相比实施例26有一定程度提升。实施例39-44是BET，5T泄压粉末，Dv50和C004/C110比值同时满足的负极活性物质材料，可以发现，锂离子电池容量明显提高，这表明上述对活性材料的限定条件可以进一步改善电池的性能。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。

Claims (10)

  1. 一种负极材料，其包括碳基材料，其中，通过氮气吸附脱附测试，所述负极材料满足：0.004cm 3/g≤S≤0.030cm 3/g，S为所述负极材料中孔径为3nm至35nm的孔的吸附体积；
    且使用以锂作为负极、以所述负极材料作为正极的扣式电池进行充放电测试，所述扣式电池放电至-5mV时，所述负极材料的克容量为Cap.A，所述扣式电池放电至5mV时，所述负极材料的克容量为Cap.B，其中，10mAh/g≤Cap.A-Cap.B≤20mAh/g。
  2. 根据权利要求1所述的负极材料，其中，0.006cm 3/g≤S≤0.025cm 3/g；和/或
    14mAh/g≤Cap.A-Cap.B≤18mAh/g。
  3. 根据权利要求1所述的负极材料，其中，通过拉曼测试，所述负极材料满足：0.2≤Id/Ig≤0.5，其中，Id为拉曼光谱中1350cm -1峰的强度，Ig为拉曼光谱中1580cm -1处峰的强度；和/或
    通过X射线衍射法测试，负极材料沿a轴方向的平均堆积厚度为La，100nm≤La≤140nm。
  4. 根据权利要求3所述的负极材料，其中，0.3≤Id/Ig≤0.5；和/或110nm≤La≤140nm。
  5. 根据权利要求1所述的负极材料，其中，所述负极材料满足如下条件(i)至(iv)中的至少一者：
    (i)所述负极材料的比表面积为2cm 2/g至15cm 2/g；
    (ii)所述负极材料的5t粉末压实密度为1.7g/cm 3至2.2g/cm 3；
    (iii)所述负极材料的Dv50满足：5μm≤Dv50≤26μm；
    (iv)通过X射线衍射法测试，所述负极材料的004晶面衍射峰面积C004与110晶面衍射峰面积C110的比值满足1≤C004/C110≤5。
  6. 根据权利要求5所述的负极材料，其中，所述负极材料满足如下条件(v)至(viii)中的至少一者：
    (v)所述负极材料的比表面积为4cm 2/g至10cm 2/g；
    (vi)所述负极材料的5t粉末压实密度为1.8g/cm至2.1g/cm 3；
    (vii)10μm≤Dv50≤20μm；
    (viii)1≤C004/C110≤3。
  7. 根据权利要求1所述的负极材料，其中，所述碳基材料的制备原材料包括天然石墨和/或人造石墨。
  8. 根据权利要求1所述的负极材料，其中，所述碳基材料的制备方法包括：将石墨材料进行石墨复合材料制备、球形化处理、包覆处理和碳化处理，其中，制备所述石墨材料的原料选自天然石墨或人造石墨材料中的至少一种。
  9. 一种二次电池，其包括负极，所述负极包括负极集流体和设置在所述负极集流体的至少一个表面上的负极活性材料层，其中所述负极活性材料层包括权利要求1-8中任一项所述的负极材料。
  10. 一种电子装置，包括权利要求9所述的二次电池。
PCT/CN2022/123059 2022-09-30 2022-09-30 负极材料、二次电池和电子装置 Ceased WO2024065597A1 (zh)

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