WO2022174598A1 - 硅碳复合负极材料及其制备方法、锂离子电池 - Google Patents

硅碳复合负极材料及其制备方法、锂离子电池 Download PDF

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WO2022174598A1
WO2022174598A1 PCT/CN2021/123543 CN2021123543W WO2022174598A1 WO 2022174598 A1 WO2022174598 A1 WO 2022174598A1 CN 2021123543 W CN2021123543 W CN 2021123543W WO 2022174598 A1 WO2022174598 A1 WO 2022174598A1
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silicon
negative electrode
electrode material
active particles
based active
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PCT/CN2021/123543
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English (en)
French (fr)
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何鹏
肖称茂
郭锷明
任建国
贺雪琴
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贝特瑞新材料集团股份有限公司
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Priority to JP2023516632A priority Critical patent/JP2023541439A/ja
Priority to US18/247,929 priority patent/US20230378444A1/en
Priority to KR1020237008566A priority patent/KR20230051241A/ko
Priority to EP21926312.6A priority patent/EP4199145A1/en
Publication of WO2022174598A1 publication Critical patent/WO2022174598A1/zh

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    • 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
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    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
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    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of negative electrode materials, in particular, to a silicon-carbon composite negative electrode material, a preparation method thereof, and a lithium ion battery.
  • Lithium-ion batteries are widely used in electric vehicles and consumer electronic products due to their advantages of high energy density, high output power, long cycle life and low environmental pollution.
  • the research and development of silicon anode materials is becoming more and more mature.
  • the volume expansion of the silicon anode material is relatively large (>300%) during the lithium deintercalation process, and the silicon anode material will be pulverized and dropped from the current collector during the charging and discharging process, causing the active material and the current collector to lose electrical contact, resulting in The electrochemical performance deteriorates, the capacity decays, and the cycle stability decreases, making it difficult to obtain commercial applications.
  • nanometerization, porosity or carbon coating technology can be used to improve, among which, the modification of silicon material itself is one of the important directions.
  • the present application provides a silicon carbon composite negative electrode material, a preparation method thereof, and a lithium ion battery, which can effectively suppress the volume expansion of the negative electrode material and improve the battery cycle performance, and the preparation method can reduce the preparation cost.
  • the present application provides a silicon-carbon composite negative electrode material
  • the silicon-carbon composite negative electrode material includes silicon-based active particles, a conductive material and a carbon coating layer; the carbon coating layer is located between the silicon-based active particles and the carbon coating layer. / or the surface of the conductive material;
  • the half-width of the X-ray diffraction angle (2 ⁇ ) of the silicon-based active particles at the (111) plane is greater than or equal to 0.5 degrees.
  • the half-width of the X-ray diffraction angle (2 ⁇ ) of the silicon-based active particles at the (111) plane is greater than or equal to 0.5 degrees, which is beneficial to suppress the volume of silicon expansion, reduce the expansion rate of the negative electrode, improve the charge and discharge efficiency of the negative electrode, and improve the cycle performance of the battery.
  • the present application also provides a silicon-carbon composite negative electrode material.
  • the silicon-carbon composite negative electrode material has a core-shell structure and includes silicon-based active particles and a carbon coating covering at least part of the surface of the silicon-based active particles.
  • the half-width of the X-ray diffraction angle (2 ⁇ ) of the silicon-carbon composite negative electrode material at the (111) plane is greater than or equal to 0.5 degrees.
  • the silicon-carbon composite negative electrode material has a core-shell structure, the inner core includes the silicon-based active particles and the conductive material, and the conductive material is embedded between the silicon-based active particles , the outer shell includes the carbon cladding layer.
  • the silicon-carbon composite negative electrode material satisfies at least one of the following conditions a to f:
  • the silicon-based active particles include at least one of Si, SiO x and silicon alloys, wherein 0 ⁇ x ⁇ 2;
  • the median diameter of the silicon-based active particles is 5 nm to 120 nm;
  • the hardness of the silicon-based active particles measured by the nanoindentation method is 3Gpa ⁇ 20Gpa;
  • the mass percentage content of Si 4+ in the silicon-based active particles is 0.05% to 5%;
  • the conductive material includes at least one of graphite sheets, carbon nanotubes, carbon fibers and graphene;
  • the thickness of the carbon coating layer is 50 nm to 2500 nm.
  • the silicon-carbon composite negative electrode material satisfies at least one of the following conditions a to f:
  • the median particle size of the silicon-based composite negative electrode material is 5 ⁇ m to 30 ⁇ m;
  • the specific surface area of the silicon-based composite negative electrode material is 0.5m 2 /g ⁇ 10m 2 /g;
  • the powder compaction density of the silicon-based composite negative electrode material is 0.4g/cm 3 to 1.2g/cm 3 ;
  • the mass percentage content of carbon element in the silicon-based composite negative electrode material is 15% to 65%;
  • the mass percentage content of silicon-based active particles in the silicon-based composite negative electrode material is 15% to 70%;
  • the mass percentage content of the conductive material in the silicon-based composite negative electrode material is 5% to 70%.
  • an embodiment of the present application provides a method for preparing a silicon-carbon composite negative electrode material, the method comprising the following steps:
  • the silicon-based active particles are added to an organic solvent, and dispersed to obtain a precursor solution, wherein, when the silicon-based active particles are measured by X-ray diffraction using CuK ⁇ rays, the X-ray diffraction of the silicon-based active particles at the (111) plane is obtained.
  • the half-width of the ray diffraction angle (2 ⁇ ) is greater than or equal to 0.5 degrees;
  • the negative electrode material precursor is heat-treated to obtain a silicon-based composite negative electrode material
  • the silicon-carbon composite negative electrode material includes silicon-based active particles, a conductive material and a carbon coating layer
  • the carbon coating layer is formed on the silicon-based Active particles and/or the surface of the conductive material.
  • the half-width of the X-ray diffraction angle (2 ⁇ ) of the silicon-based active particles at the (111) plane is greater than or equal to 0.5 degrees.
  • Silicon-based active particles, conductive materials and carbon source precursors are mixed in a solvent, and then a negative electrode material can be obtained by heat treatment.
  • the prepared negative electrode material is beneficial to suppress the volume expansion of silicon, reduce the negative electrode expansion rate, and improve the negative electrode charge-discharge efficiency. , improve the battery cycle performance.
  • an embodiment of the present application provides a method for preparing a silicon-carbon composite negative electrode material, the method comprising the following steps:
  • the silicon-based active particles are added to an organic solvent, and dispersed to obtain a precursor solution, wherein, when the silicon-based active particles are measured by X-ray diffraction using CuK ⁇ rays, the X-ray diffraction of the silicon-based active particles at the (111) plane is obtained.
  • the half-width of the ray diffraction angle (2 ⁇ ) is greater than or equal to 0.5 degrees;
  • the negative electrode material precursor is heat-treated to obtain a silicon-based composite negative electrode material
  • the silicon-carbon composite negative electrode material includes silicon-based active particles and a carbon coating layer
  • the carbon coating layer is formed on the silicon-based active particles. at least part of the surface.
  • the half-width of the X-ray diffraction angle (2 ⁇ ) of the silicon-based active particles at the (111) plane is greater than or equal to 0.5 degrees.
  • the silicon-based active particles and the carbon source precursor are mixed in the solvent, and then the negative electrode material can be obtained by heat treatment.
  • the obtained negative electrode material is conducive to suppressing the volume expansion of silicon, reducing the negative electrode expansion rate, improving the charge and discharge efficiency of the negative electrode, and improving the battery. cycle performance.
  • the silicon-based composite negative electrode material satisfies at least one of the following conditions a to d:
  • the mass percentage content of Si 4+ in the silicon-based active particles is 0.05% to 5%;
  • the median diameter of the silicon-based active particles is 5 nm to 120 nm;
  • the hardness of the silicon-based active particles is 3Gpa ⁇ 20Gpa;
  • the silicon-based active particles include at least one of Si, SiO x and silicon alloys, wherein 0 ⁇ x ⁇ 2.
  • the silicon-based composite negative electrode material satisfies at least one of the following conditions a to e:
  • the median particle size of the silicon-based composite negative electrode material is 5 ⁇ m to 30 ⁇ m;
  • the specific surface area of the silicon-based composite negative electrode material is 0.5m 2 /g ⁇ 10m 2 /g;
  • the powder compaction density of the silicon-based composite negative electrode material is 0.4g/cm 3 to 1.2g/cm 3 ;
  • the mass percentage content of carbon element in the silicon-based composite negative electrode material is 15% to 65%;
  • the mass percentage content of silicon-based active particles in the silicon-based composite negative electrode material is 15% to 70%.
  • the mass percentage content of the conductive material in the silicon-based composite negative electrode material is 5% to 70%.
  • the method satisfies at least one of the following conditions a to c:
  • the mass ratio of the silicon-based active particles, the conductive material and the carbon source precursor is (10-70): (5-30): (15-40);
  • the conductive material includes at least one of graphite sheets, carbon nanotubes, carbon fibers and graphene;
  • the carbon source precursor includes at least one of sucrose, glucose, polyethylene, polyaniline, phenolic resin, polyvinyl chloride and asphalt.
  • the method satisfies at least one of the following conditions a to b:
  • the mass ratio of the silicon-based active particles to the carbon source precursor is (10-70): (15-40);
  • the carbon source precursor includes at least one of sucrose, glucose, polyethylene, polyaniline, phenolic resin, polyvinyl chloride and asphalt.
  • the method further includes:
  • the surfactant includes polyvinyl alcohol, n-octadecic acid, polyethylene glycol, lauric acid, polyacrylic acid, sodium dodecylbenzenesulfonate, n-eicosic acid , at least one of polyvinyl chloride and polyvinylpyrrolidone; and/or, the organic solvent includes methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol and pentanol at least one of alcohols.
  • the method satisfies at least one of the following conditions a to c:
  • the temperature of the heat treatment is 500°C ⁇ 1200°C;
  • the heat treatment time is 1h to 9h;
  • the heating rate of the heat treatment is 1°C/min ⁇ 15°C/min.
  • the present application provides a lithium ion battery, comprising a silicon-carbon composite negative electrode material or a negative electrode material prepared by the above-mentioned preparation method of a silicon-carbon composite negative electrode material.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon-based active particles at the (111) plane is greater than or equal to 0.5 degrees, and the silicon-based active particles have small crystal grains, which can effectively reduce the Silicon volume expands to improve cycle performance.
  • Other beneficial effects will be described in the detailed description.
  • Fig. 1 is the scanning electron microscope picture of the silicon-carbon composite negative electrode material that the embodiment of this application provides;
  • FIG. 3 is a high-resolution TEM picture of silicon-based active particles in the silicon-carbon composite negative electrode material provided by the embodiment of the application;
  • FIG. 4 is a schematic flowchart of a method for preparing a silicon-carbon composite negative electrode material according to an embodiment of the present application.
  • FIG. 5 is another schematic flowchart of the preparation method of the silicon-carbon composite negative electrode material provided by the embodiment of the present application.
  • the silicon-carbon composite negative electrode material provided by the present application includes silicon-based active particles, conductive materials and carbon coating layers.
  • the carbon coating is on the surface of the silicon-based active particles.
  • the carbon coating is on the surface of the conductive material.
  • the carbon coating is on both the silicon-based active particles and the surface of the conductive material.
  • the half-width of the X-ray diffraction angle (2 ⁇ ) of the silicon-based active particles at the (111) plane is greater than or equal to 0.5 degrees.
  • the silicon-based active particles in the negative electrode material of the present application are silicon-based active particles with smaller crystal grains, which can effectively reduce the volume expansion of silicon and improve the cycle performance.
  • the half-width of the X-ray diffraction angle (2 ⁇ ) of the silicon-based active particles at the (111) plane is lower than 0.5, the grain size of the silicon-based active particles is too large, and the volume expansion of the silicon-based active particles is large, which is not conducive to the performance of the negative electrode material. promote.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon-based active particles at the (111) plane is greater than or equal to 0.6 degrees.
  • the present application also provides a silicon-carbon composite negative electrode material.
  • the silicon-carbon composite negative electrode material has a core-shell structure and includes silicon-based active particles and a carbon coating layer covering at least part of the surfaces of the silicon-based active particles.
  • the half-width of the X-ray diffraction angle (2 ⁇ ) of the silicon-carbon composite negative electrode material at the (111) plane is greater than or equal to 0.5 degrees.
  • the silicon-based active particles include at least one of Si, SiO x and silicon alloys, where 0 ⁇ x ⁇ 2; but not limited to the silicon-based active materials listed above, other silicon-based active materials commonly used in the art Active materials are also suitable, such as carbon-coated silicon oxides, silicon-doped semiconductors or other silicon-containing compounds.
  • the silicon-based active particles may be Si, SiO, SiO 2 , a silicon-lithium alloy, a silicon-magnesium alloy, and the like.
  • SiO x silicon oxide exists on the surface of the silicon-based active particles, which can effectively suppress the volume expansion of silicon and improve the efficiency and cycle life of the negative electrode including the negative electrode active material.
  • the mass percentage content of Si 4+ in the silicon-based active particles is 0.05% to 5%, specifically, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1 %, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc. It should be noted that, due to the presence of Si 4+ in the silicon-based active particles, it can be used as the second inactive phase in the process of silicon deintercalation and intercalation. When the second inactive phase containing Si 4+ is uniformly distributed with finely dispersed particles When used in silicon-based active particles, it will have a significant strengthening effect.
  • the second inactive phase plays a structural stabilizing role in the process of silicon volume expansion, which can effectively inhibit the volume expansion of silicon, reduce the expansion rate, and improve the cycle stability of the battery. sex.
  • the median particle size of the silicon-based active particles is 5 nm to 120 nm, specifically 5 nm, 10 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, or 120 nm, etc., but not limited to the above-mentioned ones.
  • the median particle size of the silicon-based active particles is 5 nm to 80 nm. It is understandable that the smaller the particle size of the silicon-based active particles, the better the material performance. Considering the preparation of silicon-based active particles with extremely small particle size The median diameter of the silicon-based active particles is more preferably 5 nm to 40 nm.
  • nano-scale silicon-based active particles have high surface energy, disordered surface atomic arrangement, good ductility and stability, and strong particle structure, which can inhibit the volume expansion of silicon.
  • agglomeration is likely to occur during the charging and discharging process. Therefore, in the composite negative electrode material provided in the present application, conductive materials are arranged between the silicon-based active particles, and carbon-coated The coating layer coats the silicon-based active particles and the conductive material, which can inhibit the occurrence of agglomeration and reduce the direct contact between the silicon-based active particles and the electrolyte.
  • Silicon-based active particles have a large specific surface area, and a passivation film is easily formed on the surface during the charging and discharging process, which consumes a large amount of lithium ions, reduces the concentration of lithium ions in the electrolyte, and reduces the reversible capacity of the battery. Then, the direct contact between the silicon-based active particles and the electrolyte can be reduced, the generation of passivation films can be reduced, and the reversible capacity of the battery can be improved. As shown in FIG. 3 , the silicon-based active particles may be monocrystalline silicon nanoparticles composed of one crystal grain, and/or polycrystalline silicon nanoparticles composed of multiple crystal grains.
  • the hardness of the silicon-based active particles measured by the nanoindentation method is 3Gpa ⁇ 20Gpa, specifically 3Gpa, 5Gpa, 8Gpa, 12Gpa, 15Gpa, 18Gpa or 20Gpa, etc., but It is not limited to the above-mentioned enumeration. It has been found through many tests that when the hardness of silicon-based active particles is within the above range, because of their strong rigidity and strong particle structure stability, they can resist a certain volume expansion stress, thereby reducing expansion and improving battery cycle stability.
  • the conductive material includes at least one of graphite flakes, carbon nanotubes, carbon fibers, and graphene. But it is not limited to the conductive materials listed above, and other conductive materials commonly used in the art, such as coke, carbon black, and carbon microspheres, are also applicable.
  • the graphite flakes can be natural flake graphite
  • the carbon fibers can be natural carbon fibers or synthetic carbon fibers.
  • the thickness of the carbon coating layer ranges from 50 nm to 2500 nm, specifically 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 1000 nm, 1200 nm, 1500 nm, 2000 nm, or 2500 nm, etc., but It is not limited to the above-mentioned enumeration.
  • the carbon coating layer coated on the silicon-based active particles and the conductive material can reduce the contact between the silicon-based active particles and the electrolyte, reduce the generation of passivation films, and improve the reversible capacity of the battery.
  • the thicker the carbon cladding layer the better the protection effect and the more stable the structure; however, if the carbon cladding layer is too thick, the carbon ratio is too large, and the capacity of the silicon-carbon composite material will be too low.
  • the thickness of the carbon coating layer is controlled at 100 nm to 1500 nm.
  • the silicon-based composite negative electrode material has a core-shell structure, the inner core includes silicon-based active particles and conductive materials, and the outer shell includes a carbon coating layer.
  • the particles of the silicon-based composite negative electrode material can also be spherical or spherical.
  • the conductive material is embedded between the silicon-based active particles.
  • the median particle size of the silicon-based composite negative electrode material is 5 ⁇ m to 30 ⁇ m, and the median particle size may specifically be 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, 18 ⁇ m, 20 ⁇ m, 23 ⁇ m, 25 ⁇ m, 28 ⁇ m or 30 ⁇ m, etc. etc., but not limited to the above list.
  • the median particle size of the silicon-based composite negative electrode material is 8 ⁇ m ⁇ 20 ⁇ m.
  • the specific surface area of the silicon-based composite negative electrode material ranges from 0.5m 2 /g to 10m 2 /g, and the specific surface area may specifically be 0.5m 2 /g, 1m 2 /g, 2m 2 /g, 3m 2 /g, 4m 2 /g, 5m 2 /g, 6m 2 /g, 7m 2 /g, 8m 2 /g, 9m 2 /g or 10m 2 /g, etc., but not limited to the above list.
  • the specific surface area of the silicon-based composite negative electrode material is 1 m 2 /g ⁇ 6 m 2 /g. It is understandable that the smaller the specific surface area, the better.
  • the specific surface area is controlled at 1m 2 /g ⁇ 6m 2 /g.
  • the powder compaction density of the silicon-based composite negative electrode material is 0.4g/cm 3 to 1.2g/cm 3
  • the powder compact density may specifically be 0.4g/cm 3 or 0.5g/cm 3 , 0.6g/cm 3 , 0.7g/cm 3 , 0.8g/cm 3 , 0.9g/cm 3 , 1.0g/cm 3 , 1.1g/cm 3 , or 1.2g/cm 3 , etc., but not limited to Listed above.
  • the powder compaction density of the silicon-based composite negative electrode material is 0.5 g/cm 3 to 0.9 g/cm 3 .
  • the mass percentage of carbon element in the silicon-based composite negative electrode material is 15% to 65%
  • the mass percentage of silicon-based active particles is 15% to 70%
  • the mass percentage of the conductive material is 5% to 70%.
  • the present application also provides a method for preparing a silicon-carbon composite negative electrode material, as shown in FIG. 4 , the method includes the following steps:
  • the silicon-carbon composite negative electrode material includes silicon-based active particles, a conductive material and a carbon coating layer, and the carbon coating layer is formed on the silicon-based active particles and/or conductive layers material surface.
  • the half-width of the X-ray diffraction angle (2 ⁇ ) of the silicon-based active particles at the (111) plane is greater than or equal to 0.5 degrees.
  • Silicon-based active particles, conductive materials and carbon source precursors are mixed in a solvent, and then heat-treated to coat the surface of silicon-based active particles and conductive materials with a carbon-containing coating layer, which can inhibit the occurrence of agglomeration and reduce silicon Direct contact of the base active particles with the electrolyte.
  • the finally prepared negative electrode material is beneficial to suppress the volume expansion of silicon, reduce the negative electrode expansion rate, improve the charge-discharge efficiency of the negative electrode, and improve the battery cycle performance.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the selected silicon-based active particles at the (111) plane is greater than or equal to 0.5 degrees, and the silicon-based active particles have smaller crystal grains, which can effectively reduce the volume expansion of silicon and improve the cycle performance.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon-based active particles at the (111) plane is lower than 0.5, the grain size of the silicon-based active particles is too large, and the volume expansion of the silicon-based active particles is large, which is not conducive to the improvement of the performance of the negative electrode material.
  • Step S10 adding silicon-based active particles into an organic solvent, and dispersing to obtain a precursor solution.
  • the silicon-based active particles include at least one of Si, SiOx , and silicon alloys, where 0 ⁇ x ⁇ 2.
  • the median particle size of the silicon-based active particles is 5 nm to 120 nm, specifically 5 nm, 10 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm or 120 nm, etc. Not limited to the above list.
  • the median diameter of the silicon-based active particles is 5 nm ⁇ 80 nm.
  • nano-scale silicon-based active particles have high surface energy, disordered surface atomic arrangement, good ductility and stability, and strong particle structure, which can inhibit the volume expansion of silicon. More preferably, the median diameter of the silicon-based active particles is 5 nm ⁇ 40 nm.
  • the half-width of the X-ray diffraction angle (2 ⁇ ) of the silicon-based active particles at the (111) plane may specifically be 0.52, 0.65, 0.71, 0.75, 0.81, 0.86, 0.98, etc., but not limited to the above enumerate. It should be noted that when X-rays are incident on a small crystal, its diffraction lines will become diffused and broadened. The smaller the crystal grains, the greater the broadening of the X-ray diffraction bands.
  • the half-width of the X-ray diffraction angle (2 ⁇ ) of the particles at the (111) plane is greater than or equal to 0.5 degrees, the crystal grains of the silicon-based active particles are small, which can effectively reduce the volume expansion of silicon and improve the cycle performance.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon-based active particles at the (111) plane is greater than or equal to 0.6 degrees.
  • the mass percentage content of Si 4+ in the silicon-based active particles may be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 1.5%, 2%, 2.5% , 3%, 3.5%, 4%, 4.5%, 5%, etc.
  • Si 4+ due to the presence of Si 4+ in the silicon-based active particles, it can be used as the second inactive phase in the process of silicon deintercalation and intercalation.
  • the second inactive phase containing Si 4+ is uniformly distributed with finely dispersed particles
  • the second inactive phase plays a structural stabilizing role in the process of silicon volume expansion, which can effectively inhibit the volume expansion of silicon, reduce the expansion rate, and improve the cycle stability of the battery. sex.
  • the hardness of the silicon-based active particles measured under a force of 6mN is 3Gpa ⁇ 20Gpa, specifically 3Gpa, 5Gpa, 8Gpa, 12Gpa, 15Gpa, 18Gpa or 20Gpa, etc., but It is not limited to the above-mentioned enumeration.
  • the hardness of the silicon-based active particle is within the above range, because of its strong rigidity and strong particle structure stability, it can resist a certain volume expansion stress, thereby reducing the expansion and improving the battery cycle stability.
  • the organic solvent includes at least one of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol, and amyl alcohol.
  • a surfactant needs to be added to the organic solvent, and the surfactant includes polyvinyl alcohol (PVA), n-octadecic acid, polyethylene glycol (PEG), lauric acid, polyvinyl alcohol At least one of acrylic acid (PAA), sodium dodecylbenzenesulfonate (SDBS), n-eicosic acid, polyvinyl chloride (PVC) and polyvinylpyrrolidone (PVP). It is understandable that adding a surfactant can accelerate the dispersion of the silicon-based active particles and avoid the agglomeration of the silicon-based active particles.
  • PVA polyvinyl alcohol
  • PEG polyethylene glycol
  • lauric acid polyvinyl alcohol
  • PAA acrylic acid
  • SDBS sodium dodecylbenzenesulfonate
  • PVC polyvinyl chloride
  • PVP polyvinylpyrrolidone
  • magnetic stirring, mechanical stirring, etc. can also be used, ultrasonic dispersion, grinding dispersion, etc., preferably grinding and dispersion, so that the silicon-based active particles can be dispersed, Agglomeration of the silicon-based active particles is avoided, and the silicon-based active particles can be dispersed into smaller single-crystal silicon nanoparticles.
  • the mass percentage content of Si 4+ can be increased by controlling the grinding time of the silicon particles. Generally speaking, the longer the grinding time, the higher the mass percentage content of Si 4+ .
  • Step S20 adding a conductive material and a carbon source precursor to the precursor solution to obtain a negative electrode material precursor.
  • the mass ratio of the silicon-based active particles, the conductive material and the carbon source precursor is (10-70):(5-30):(15-40).
  • the mass ratio of the silicon-based active particles, the conductive material and the carbon source precursor may be 40:10:40, 60:10:30, 50:20:25, 70:5:25, 55:10:30, and the like. However, it is not limited to the above-mentioned enumeration.
  • the conductive material includes at least one of graphite flakes, carbon nanotubes, carbon fibers, and graphene. But it is not limited to the conductive materials listed above, and other conductive materials commonly used in the art, such as coke, carbon black, and carbon microspheres, are also applicable.
  • the graphite flakes can be natural flake graphite
  • the carbon fibers can be natural carbon fibers or synthetic carbon fibers.
  • the carbon source precursor includes sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyvinyl At least one of vinylidene fluoride, polyacrylonitrile, polyvinyl chloride and asphalt.
  • the median particle size of the carbon source precursor is 1 ⁇ m to 50 ⁇ m, and the median particle size may specifically be 1 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, 18 ⁇ m, 20 ⁇ m, 25 ⁇ m, 30 ⁇ m, 35 ⁇ m, 40 ⁇ m , 45 ⁇ m or 50 ⁇ m, etc., but not limited to the above listed.
  • the median particle size of the carbon source precursor is 1 ⁇ m ⁇ 20 ⁇ m.
  • a conductive material and a carbon source precursor are added to the precursor solution, and after stirring evenly, a separation treatment can be performed.
  • the solid material obtained by the separation treatment is dried to obtain a negative electrode material precursor;
  • the drying temperature is 25°C to 200°C, specifically, 25°C, 50°C, 75°C, 100°C, 125°C, 150°C, 175°C or 200°C, etc., but not limited to Listed above.
  • the drying time is 1 h to 15 h, specifically, 1 h, 2 h, 3 h, 4 h, 5 h, 7 h, 9 h, 10 h, 12 h or 15 h, etc., but is not limited to the above list.
  • the drying treatment method may specifically be oven drying, spray drying, vacuum drying, freeze drying, etc.
  • the drying treatment in this embodiment can remove the solvent in the precursor solution as much as possible.
  • the dried anode material precursor is silicon-based active particles and conductive materials coated by the carbon source precursor.
  • the dried anode material precursor can be sent to a high-temperature box furnace for heat treatment, so that the carbon source precursor is carbonized to form Carbon cladding.
  • step S30 heat treatment is performed on the negative electrode material precursor to obtain a silicon-based composite negative electrode material.
  • the manner of heat treatment may specifically be sintering treatment, hot pressing sintering, and vacuum sintering.
  • the temperature of the heat treatment is 500°C to 1200°C, specifically 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1200°C, 1200°C, and the like.
  • the temperature of the heat treatment is 800°C to 1200°C.
  • the heat treatment time is 1 h to 9 h, specifically 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, and the like.
  • the heating rate during the heat treatment ranges from 1°C/min to 15°C/min, specifically 1°C/min, 3°C/min, 5°C/min, 6°C/min, 7°C/min, 8°C/min, 9°C/min, 10°C/min, 12°C/min or 15°C/min, preferably, the heating rate during heat treatment is 5°C/min ⁇ 10°C/min.
  • a protective gas is passed through the heat treatment process, and the protective gas is at least one of nitrogen, helium, neon, argon or krypton.
  • the prepared silicon-based composite negative electrode material has a core-shell structure, the inner core is silicon-based active particles and conductive materials, and the outer shell is a carbon coating layer.
  • the particles of the silicon-based composite negative electrode material can also be spherical or quasi-spherical.
  • the median particle size of the silicon-based composite negative electrode material is 5 ⁇ m to 30 ⁇ m, and the median particle size can specifically be 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, 18 ⁇ m , 20 ⁇ m, 23 ⁇ m, 25 ⁇ m, 28 ⁇ m or 30 ⁇ m, etc., but not limited to the above-mentioned enumeration.
  • conductive materials are provided between silicon-based active particles, and the silicon-based active particles are provided with conductive materials.
  • the surface of the active particles and the conductive material is coated with a carbon-containing coating layer, which can inhibit the occurrence of agglomeration and reduce the direct contact between the silicon-based active particles and the electrolyte.
  • Silicon-based active particles have a large specific surface area, and a passivation film is easily formed on the surface during the charging and discharging process, which consumes a large amount of lithium ions, reduces the concentration of lithium ions in the electrolyte, and reduces the reversible capacity of the battery. Then, the direct contact between the silicon-based active particles and the electrolyte can be reduced, the generation of passivation films can be reduced, and the reversible capacity of the battery can be improved.
  • the median particle size of the silicon-based composite negative electrode material is 8 ⁇ m ⁇ 20 ⁇ m.
  • the carbon coating layer coated on the silicon-based active particles and the conductive material can reduce the contact between the silicon-based active particles and the electrolyte, reduce the generation of passivation films, and improve the reversible capacity of the battery.
  • the specific surface area of the silicon-based composite negative electrode material ranges from 0.5m 2 /g to 10m 2 /g, and the specific surface area may specifically be 0.5m 2 /g, 1m 2 /g, 2m 2 /g, 3m 2 /g, 4m 2 /g, 5m 2 /g, 6m 2 /g, 7m 2 /g, 8m 2 /g, 9m 2 /g or 10m 2 /g, etc., but not limited to the above list.
  • the specific surface area of the silicon-based composite negative electrode material is 1 m 2 /g ⁇ 6 m 2 /g.
  • the powder compaction density of the silicon-based composite negative electrode material is 0.4g/cm 3 to 1.2g/cm 3
  • the powder compact density may specifically be 0.4g/cm 3 or 0.5g/cm 3 , 0.6g/cm 3 , 0.7g/cm 3 , 0.8g/cm 3 , 0.9g/cm 3 , 1.0g/cm 3 , 1.1g/cm 3 , or 1.2g/cm 3 , etc., but not limited to Listed above.
  • the powder compaction density of the silicon-based composite negative electrode material is 0.5 g/cm 3 to 0.9 g/cm 3 .
  • the mass percentage of carbon element in the silicon-based composite negative electrode material is 15% to 65%
  • the mass percentage of silicon-based active particles is 15% to 70%
  • the mass percentage of the conductive material is 5% to 70%.
  • the silicon-carbon composite negative electrode material prepared by the above preparation method is coated with a carbon coating layer on the surface of the silicon-based active particles and the conductive material, which can suppress the expansion of the material during the cycle.
  • the half-width of the X-ray diffraction angle (2 ⁇ ) of the silicon-based active particles in the core structure at the (111) plane is greater than or equal to 0.5 degrees, and has smaller crystal grains, which can effectively reduce the volume expansion of silicon and improve the cycle performance.
  • nano-scale silicon-based active particles there may be SiO x oxides on the surface of silicon-based active particles, which can effectively inhibit the volume expansion of silicon and improve the efficiency and cycle life of the negative electrode including the negative electrode active material; further, silicon-based The mass percentage content of Si 4+ in the active particles is 0.05% to 5%, which can effectively inhibit the volume expansion of silicon, reduce the expansion rate, and improve the cycle.
  • the silicon-based active particles have high hardness and strong rigidity, which can effectively resist a certain volume expansion stress, which is conducive to maintaining the structural stability of the negative electrode material, thereby reducing the expansion rate and improving the battery cycle performance.
  • the present application also provides a method for preparing a silicon-carbon composite negative electrode material, as shown in FIG. 5 , the method includes the following steps:
  • the half-width of the X-ray diffraction angle (2 ⁇ ) of the silicon-based active particles at the (111) plane is greater than or equal to 0.5 degrees.
  • the silicon-based active particles and the carbon source precursor are mixed in a solvent, and then heat-treated to coat the surface of the silicon-based active particles with a carbon-containing coating layer, which can inhibit the occurrence of agglomeration and reduce the amount of silicon-based active particles and electrolyte. of direct contact.
  • the finally prepared negative electrode material is beneficial to suppress the volume expansion of silicon, reduce the negative electrode expansion rate, improve the charge-discharge efficiency of the negative electrode, and improve the battery cycle performance.
  • the mass ratio of the silicon-based active particles and the carbon source precursor is (10-70):(15-40).
  • the specific mass ratio of the silicon-based active particles to the carbon source precursor may be 40:40, 60:30, 50:25, 70:25, 55:30, and the like. However, it is not limited to the above-mentioned enumeration.
  • the present application also provides a lithium ion battery, the lithium ion battery includes a negative pole piece, a positive pole piece, a diaphragm and a non-aqueous electrolyte, the negative pole piece includes a current collector and is coated on the collector.
  • the lithium ion battery includes a negative pole piece, a positive pole piece, a diaphragm and a non-aqueous electrolyte
  • the negative pole piece includes a current collector and is coated on the collector.
  • Disperse silicon powder with a median particle size of 20nm in ethylene glycol solution add 1.5wt% PVP surfactant after ultrasonic dispersion for 10min, ultrasonically disperse for 20min to obtain a dispersion solution, and then place the dispersion solution in a ball mill for grinding Disperse for 4 hours to obtain a precursor solution.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon particles in the silicon powder at the (111) plane is greater than or equal to 0.98 degrees, the mass percentage content of Si 4+ in the silicon powder is 1.5%, and the silicon
  • the hardness of silicon particles in the powder is 18Gpa; the median particle size of the obtained silicon-carbon composite negative electrode material is about 6.2 ⁇ m, the specific surface area is 10m 2 /g, the mass percentage of carbon is 20%, and the thickness of the carbon coating layer is 300nm.
  • Disperse silicon powder with a median particle size of 30nm in n-butanol solution add 2.0wt% PEG surfactant after ultrasonic dispersion for 10min, ultrasonically disperse for 30min to obtain a dispersion solution, and then place the dispersion solution in a ball mill for grinding Disperse for 8 hours to obtain a precursor solution.
  • the dry material is added into a high-temperature box furnace, nitrogen is introduced, and after heat treatment at 800°C, it is pulverized and sieved through a 500-mesh sieve to obtain a silicon-carbon composite material.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon particles in the silicon powder at the (111) plane is greater than or equal to 0.81 degrees, the mass percentage content of Si 4+ in the silicon powder is 0.5%, and the silicon
  • the hardness of silicon particles in the powder is 15 Gpa; the median particle size of the obtained silicon-carbon composite negative electrode material is about 10 ⁇ m, the specific surface area is 9 m 2 /g, the mass percentage of carbon is 30%, and the thickness of the carbon coating layer is 100 nm.
  • Disperse silicon powder with a median particle size of 40nm in isopropanol solution add 3.0wt% PVA surfactant after ultrasonic dispersion for 10min, ultrasonically disperse for 30min to obtain a dispersion solution, and then place the dispersion solution in a ball mill for grinding Disperse for 8 hours to obtain a precursor solution.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon particles in the silicon powder at the (111) plane is greater than or equal to 0.71 degrees, the mass percentage content of Si 4+ in the silicon powder is 1.1%, and the silicon
  • the hardness of silicon particles in the powder is 10Gpa; the median particle size of the obtained silicon-carbon composite negative electrode material is about 24 ⁇ m, the specific surface area is 6m 2 /g, the mass percentage of carbon is 22%, and the thickness of the carbon coating layer is 200nm.
  • Disperse silicon powder with a median particle size of 80nm in ethylene glycol solution add 2.5wt% PEG surfactant after ultrasonic dispersion for 10min, ultrasonically disperse for 30min to obtain a dispersion solution, and then place the dispersion solution in a ball mill for grinding Disperse for 8 hours to obtain a precursor solution.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon particles in the silicon powder at the (111) plane is greater than or equal to 0.62 degrees, the mass percentage content of Si 4+ in the silicon powder is 0.2%, and the silicon
  • the hardness of silicon particles in the powder is 8Gpa; the median particle size of the obtained silicon-carbon composite negative electrode material is about 18 ⁇ m, the specific surface area is 6m 2 /g, the mass percentage of carbon is 18%, and the thickness of the carbon coating layer is 800nm.
  • Disperse silicon powder with a median particle size of 20nm in ethylene glycol solution add 1.5wt% PVP surfactant after ultrasonic dispersion for 10min, ultrasonically disperse for 20min to obtain a dispersion solution, and then place the dispersion solution in a ball mill for grinding Disperse for 4 hours to obtain a precursor solution.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon particles in the silicon powder at the (111) plane is greater than or equal to 0.98 degrees
  • the mass percentage content of Si 4+ in the silicon powder is 0.01%
  • the silicon The hardness of silicon particles in the powder is 18Gpa
  • the median particle size of the obtained silicon-carbon composite negative electrode material is about 6.6 ⁇ m
  • the specific surface area is 9.8m 2 /g
  • the mass percentage of carbon is 21%
  • the thickness of the carbon coating layer is 300nm .
  • Disperse silicon powder with a median particle size of 20nm in ethylene glycol solution add 1.5wt% PVP surfactant after ultrasonic dispersion for 10min, ultrasonically disperse for 20min to obtain a dispersion solution, and then place the dispersion solution in a ball mill for grinding Disperse for 4 hours to obtain a precursor solution.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon particles in the silicon powder at the (111) plane is greater than or equal to 0.98 degrees
  • the mass percentage content of Si 4+ in the silicon powder is 1.5%
  • the silicon The hardness of silicon particles in the powder is 2Gpa
  • the median particle size of the obtained silicon-carbon composite negative electrode material is about 6.6 ⁇ m
  • the specific surface area is 9.8 m 2 /g
  • the mass percentage content of carbon is 21%
  • the thickness of the carbon coating layer is 300 nm. .
  • the nano-silicon-based composite negative electrode material was prepared according to basically the same method as in Example 1, except that it was placed in a ball mill to grind and disperse for 8 hours.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon particles in the silicon powder at the (111) plane is greater than or equal to 0.98 degrees, the mass percentage content of Si 4+ in the silicon powder is 8.5%, and the silicon
  • the hardness of silicon particles in the powder is 14Gpa; the median particle size of the obtained silicon-carbon composite negative electrode material is about 6.6 ⁇ m, the specific surface area is 7.9m 2 /g, the mass percentage of carbon is 21%, and the thickness of the carbon coating layer is 300nm. .
  • the nano-silicon-based composite negative electrode material was prepared according to basically the same method as in Example 1, except that it was placed in a ball mill to grind and disperse for 8 hours.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon particles in the silicon powder at the (111) plane is greater than or equal to 0.98 degrees
  • the mass percentage content of Si 4+ in the silicon powder is 3.5%
  • the silicon The hardness of silicon particles in the powder is 28Gpa
  • the median particle size of the obtained silicon-carbon composite negative electrode material is about 6.5 ⁇ m
  • the specific surface area is 8.8m 2 /g
  • the mass percentage of carbon content is 20%
  • the thickness of the carbon coating layer is 300nm .
  • the nano-silicon-based composite negative electrode material was prepared according to basically the same method as in Example 1, except that it was placed in a ball mill to grind and disperse for 2 hours.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon particles in the silicon powder at the (111) plane is greater than or equal to 0.98 degrees, the mass percentage content of Si 4+ in the silicon powder is 0.8%, and the silicon
  • the hardness of silicon particles in the powder is 18Gpa; the median particle size of the obtained silicon-carbon composite negative electrode material is about 5.8 ⁇ m, the specific surface area is 10m 2 /g, the mass percentage of carbon is 20%, and the thickness of the carbon coating layer is 300nm.
  • Disperse silicon powder with a median particle size of 20nm in ethylene glycol solution add 1.5wt% PVP surfactant after ultrasonic dispersion for 10min, ultrasonically disperse for 20min to obtain a dispersion solution, and then place the dispersion solution in a ball mill for grinding Disperse for 4 hours to obtain a precursor solution.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon particles in the silicon powder at the (111) plane is greater than or equal to 0.80 degrees, the mass percentage content of Si 4+ in the silicon powder is 0.8%, and the silicon
  • the hardness of silicon particles in the powder is 18Gpa; the median particle size of the obtained silicon-carbon composite negative electrode material is about 6.3 ⁇ m, the specific surface area is 12m 2 /g, the mass percentage of carbon is 25%, and the thickness of the carbon coating layer is 350nm.
  • the nano-silicon-based composite negative electrode material was prepared according to basically the same method as in Example 1, except that silicon powder with a thickness of 180 nm was used to obtain a silicon-carbon composite material.
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon particles in the silicon powder at the (111) plane is greater than or equal to 0.32 degrees
  • the mass percentage content of Si 4+ in the silicon powder is 0.01%
  • the silicon The hardness of silicon particles in the powder is 2.5Gpa
  • the median particle size of the obtained silicon-carbon composite negative electrode material is about 15 ⁇ m
  • the specific surface area is 6m 2 /g
  • the mass percentage of carbon is 18%
  • the thickness of the carbon coating layer is 300nm.
  • nano-silicon-based composite negative electrode material was prepared in the same manner as in Example 1, except that:
  • the half width of the X-ray diffraction angle (2 ⁇ ) of the silicon particles in the silicon powder at the (111) plane is greater than or equal to 0.35 degrees, the mass percentage content of Si 4+ in the silicon powder is 4.5%, and the silicon
  • the hardness of silicon particles in the powder is 2.5Gpa; the median particle size of the obtained silicon-carbon composite anode material is about 22 ⁇ m, the specific surface area is 9m 2 /g, the mass percentage of carbon is 36%, and the thickness of the carbon coating layer is 800nm.
  • the electrochemical cycle performance was tested by the following method: the prepared silicon-carbon composite anode material, conductive agent and binder were dissolved in a solvent at a mass percentage of 94:1:5, and the solid content was controlled at 50%.
  • the charge-discharge test of the cylindrical battery was carried out on the LAND battery test system of Wuhan Jinnuo Electronics Co., Ltd. under normal temperature conditions, 0.2C constant current charge and discharge, and the charge-discharge voltage was limited to 2.75-4.2V.
  • the charge-discharge test was carried out to obtain the first reversible capacity, The first lap charge capacity and the first lap discharge capacity.
  • Coulombic efficiency for the first time discharge capacity in the first cycle/charge capacity in the first cycle.
  • the X-ray diffraction method was used to measure the half-width of the X-ray diffraction angle (2 ⁇ ) of the silicon particles in the silicon powder at the (111) plane.
  • the indentation hardness test is carried out through the nano-indentation test with a load of 0.6N and a controlled indentation depth of 0.5um.
  • Si 4+ content test X-ray electron spectrum analyzer was used to measure the Si 4+ content in the silicon powder.
  • Example 5 As shown in Table 1, the difference between Example 5 and Example 1 is that the mass percentage content of Si 4+ in the silicon-based active particles used is 0.01%. During the charging and discharging process of the silicon particles, the The expansion ratio, cycle life and first efficiency are all lower than those of Example 1.
  • Example 6 The difference between Example 6 and Example 1 is that the hardness of the silicon-based active particles used is only 2 Gpa, which is less than the hardness of the silicon particles in Example 1.
  • the structural stability of the silicon particles is poor, and it is difficult to resist the volume expansion stress during the charging and discharging process. , the battery cycle stability is reduced.
  • Example 7 The difference between Example 7 and Example 1 is that the mass percentage content of Si 4+ in the silicon-based active particles used is 8.5%. If the mass percentage content of Si 4+ is too high, the capacity and initial efficiency of the negative electrode material will be reduced.
  • Example 8 The difference between Example 8 and Example 1 is that the hardness of the silicon-based active particles in the silicon powder is 28 Gpa, which is too high, and the chemical bond energy between the particle surfaces is very large. high, which leads to the difficulty of lithium ion intercalation, which is not conducive to the improvement of the cycle performance of the negative electrode material.
  • Example 9 The difference between Example 9 and Example 1 is that the dispersion solution in step (1) is placed in a ball mill to grind and disperse for 2 hours, and the grinding time is too short, while the silicon particle grinding time of Example 1 is 6 hours. It can be found that by controlling The grinding time of silicon particles can increase the mass percentage content of Si 4+ . Generally speaking, the longer the grinding time is, the higher the mass percentage content of Si 4+ .
  • Example 10 The difference between Example 10 and Example 1 is that no conductive material is added during the preparation process, resulting in a decrease in the first Coulomb efficiency and the first reversible capacity of the battery compared to Example 1.
  • the silicon-based active particles (111) used in Comparative Examples 1 to 2 have a half width of less than 0.5, and the hardness is lower than 3Gpa.
  • Examples 1-6 prepared negative electrode materials.
  • the half-width of the X-ray diffraction angle (2 ⁇ ) of the silicon-based active particles at the (111) plane is greater than or equal to 0.5 degrees, and the The mass percentage of Si 4+ is 0.05% to 5%, and the hardness of the silicon-based active particles is controlled at 3Gpa to 20Gpa, which is beneficial to suppress the volume expansion of silicon, improve the efficiency and cycle life of the negative electrode, and can effectively resist a certain volume expansion. stress, thereby reducing the expansion rate and improving the battery cycle performance.

Abstract

本申请涉及负极材料领域，提供硅碳复合负极材料及其制备方法、锂离子电池，其中，硅碳复合负极材料包括硅基活性粒子、导电材料及碳包覆层；所述碳包覆层位于所述硅基活性粒子和/或所述导电材料表面；当使用CuKα射线对硅基活性粒子作X射线衍射测量时，硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度。本申请提供的硅碳复合负极材料及其制备方法、负极极片、锂离子电池，能够有效抑制负极材料体积膨胀，提升电池循环性能。

Description

硅碳复合负极材料及其制备方法、锂离子电池
本申请要求于2021年02月20日提交中国专利局，申请号为202110193665.9、申请名称为“硅碳复合负极材料及其制备方法、锂离子电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及负极材料技术领域，具体地讲，涉及硅碳复合负极材料及其制备方法、锂离子电池。
背景技术
锂离子电池由于具备能量密度大、输出功率高、循环寿命长和环境污染小等优点而被广泛应用于电动汽车以及消费类电子产品中。为了提高电池能量密度，硅负极材料的研究和开发日趋成熟。但是硅负极材料脱嵌锂过程中体积膨胀较大(>300％)，硅负极材料在充放电过程中会粉化从集流体上掉落，使得活性物质与集流体之间失掉电触摸，导致电化学性能变差，容量衰减、循环稳定性下降，难以得到商业应用。为了提高硅负极材料的导电性和循环稳定性，可以采用纳米化、多孔化或者碳包覆技术方式来改善，其中，对硅材料自身改性是其中一个重要方向。
基于此，亟需开发一种硅碳复合负极材料，以抑制负极材料的体积膨胀，提高材料的循环稳定性。
申请内容
鉴于此，本申请提供硅碳复合负极材料及其制备方法、锂离子电池，能够有效抑制负极材料体积膨胀，提升电池循环性能，该制备方法可降低制备成本。
第一方面，本申请提供一种硅碳复合负极材料，所述硅碳复合负极材料包括硅基活性粒子、导电材料及碳包覆层；所述碳包覆层位于所述硅基活性粒子和/或所述导电材料表面；
当使用CuKα射线对所述硅基活性粒子作X射线衍射测量时，所述硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度。
在上述方案中，通过控制硅基活性粒子自身的性能参数，使得硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度，有利于抑制硅的体积膨胀，降低负极膨胀率，改善负极的充放电效率，提升电池循环性能。
第二方面，本申请还提供一种硅碳复合负极材料，所述硅碳复合负极材料为核壳结构，包括硅基活性粒子及包覆于所述硅基活性粒子至少部分表面的碳包覆层；
当使用CuKα射线对所述硅碳复合负极材料作X射线衍射测量时，所述硅碳复合负极材料在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度。
在一种可行的实施方式中，所述硅碳复合负极材料为核壳结构，内核包括 所述硅基活性粒子及所述导电材料，所述导电材料嵌设于所述硅基活性粒子之间，外壳包括所述碳包覆层。
在一种可行的实施方式中，所述硅碳复合负极材料满足以下条件a～f的至少一者：
a.所述硅基活性粒子包括Si、SiO x及硅合金中的至少一种，其中0<x≤2；
b.所述硅基活性粒子的中值粒径为5nm～120nm；
c.所述硅基活性粒子用纳米压痕法测定的硬度为3Gpa～20Gpa；
d.所述硅基活性粒子中的Si 4+的质量百分比含量为0.05％～5％；
e.所述导电材料包括石墨片、碳纳米管、碳纤维和石墨烯中的至少一种；
f.所述碳包覆层的厚度为50nm～2500nm。
在一种可行的实施方式中，所述硅碳复合负极材料满足以下条件a～f的至少一者：
a.所述硅基复合负极材料的中值粒径为5μm～30μm；
b.所述硅基复合负极材料的比表面积为0.5m 2/g～10m 2/g；
c.所述硅基复合负极材料的粉体压实密度为0.4g/cm 3～1.2g/cm 3；
d.所述硅基复合负极材料中的碳元素的质量百分比含量为15％～65％；
e.所述硅基复合负极材料中的硅基活性粒子的质量百分比含量为15％～70％；
f.所述硅基复合负极材料中的导电材料的质量百分比含量为5％～70％。
第三方面，本申请实施例提供一种硅碳复合负极材料的制备方法，所述方法包括以下步骤：
将硅基活性粒子加入有机溶剂中，分散得到前驱体溶液，其中，当使用CuKα射线对所述硅基活性粒子作X射线衍射测量时，所述硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度；
往所述前驱体溶液中加入导电材料及碳源前驱体，得到负极材料前驱体；及
对所述负极材料前驱体进行热处理，得到硅基复合负极材料，所述硅碳复合负极材料包括硅基活性粒子、导电材料及碳包覆层，所述碳包覆层形成于所述硅基活性粒子和/或所述导电材料表面。
在上述方案中，通过控制硅基活性粒子自身的性能参数，使得硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度，在制备过程中，将硅基活性粒子、导电材料以及碳源前驱体混合于溶剂内，再通过热处理即可得到负极材料，制得的负极材料有利于抑制硅的体积膨胀，降低负极膨胀率，改善负极的充放电效率，提升电池循环性能。
第四方面，本申请实施例提供一种硅碳复合负极材料的制备方法，所述方法包括以下步骤：
将硅基活性粒子加入有机溶剂中，分散得到前驱体溶液，其中，当使用CuKα射线对所述硅基活性粒子作X射线衍射测量时，所述硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度；
往所述前驱体溶液中加入碳源前驱体，得到负极材料前驱体；及
对所述负极材料前驱体进行热处理，得到硅基复合负极材料，所述硅碳复合负极材料包括硅基活性粒子及碳包覆层，所述碳包覆层形成于所述硅基活性粒子的至少部分表面。
在上述方案中，通过控制硅基活性粒子自身的性能参数，使得硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度，在制备过程中，将硅基活性粒子以及碳源前驱体混合于溶剂内，再通过热处理即可得到负极材料，制得的负极材料有利于抑制硅的体积膨胀，降低负极膨胀率，改善负极的充放电效率，提升电池循环性能。
在一种可行的实施方式中，所述硅基复合负极材料满足以下条件a～d的至少一者：
a.所述硅基活性粒子中的Si 4+的质量百分比含量为0.05％～5％；
b.所述硅基活性粒子的中值粒径为5nm～120nm；
c.所述硅基活性粒子的硬度为3Gpa～20Gpa；
d.所述硅基活性粒子包括Si、SiO x及硅合金中的至少一种，其中0<x≤2。
在一种可行的实施方式中，所述硅基复合负极材料满足以下条件a～e的至少一者：
a.所述硅基复合负极材料的中值粒径为5μm～30μm；
b.所述硅基复合负极材料的比表面积为0.5m 2/g～10m 2/g；
c.所述硅基复合负极材料的粉体压实密度为0.4g/cm 3～1.2g/cm 3；
d.所述硅基复合负极材料中的碳元素的质量百分比含量为15％～65％；
e.所述硅基复合负极材料中的硅基活性粒子的质量百分比含量为15％～70％。
在一种可行的实施方式中，所述硅基复合负极材料中的导电材料的质量百分比含量为5％～70％。
在一种可行的实施方式中，所述方法满足以下条件a～c的至少一者：
a.所述硅基活性粒子、所述导电材料和所述碳源前驱体的质量比为(10～70)：(5～30)：(15～40)；
b.所述导电材料包括石墨片、碳纳米管、碳纤维和石墨烯中的至少一种；
c.所述碳源前驱体包括蔗糖、葡萄糖、聚乙烯、聚苯胺、酚醛树脂、聚氯乙烯和沥青中的至少一种。
在一种可行的实施方式中，所述方法满足以下条件a～b的至少一者：
a.所述硅基活性粒子和所述碳源前驱体的质量比为(10～70)：(15～40)；
b.所述碳源前驱体包括蔗糖、葡萄糖、聚乙烯、聚苯胺、酚醛树脂、聚氯乙烯和沥青中的至少一种。
在一种可行的实施方式中，在将硅基活性粒子分散在有机溶剂中后，所述方法还包括：
往所述有机溶剂中加入表面活性剂，所述表面活性剂包括聚乙烯醇、正十八酸、聚乙二醇、月桂酸、聚丙烯酸、十二烷基苯磺酸钠、正二十酸、聚氯乙 烯和聚乙烯吡咯烷酮中的至少一种；和/或，所述有机溶剂包括甲醇、乙醇、乙二醇、丙醇、异丙醇、丙三醇、正丁醇、异丁醇和戊醇中的至少一种。
在一种可行的实施方式中，所述方法满足以下条件a～c的至少一者：
a.所述热处理的温度为500℃～1200℃；
b.所述热处理的时间1h～9h；
c.所述热处理的升温速率为1℃/min～15℃/min。
第五方面，本申请提供一种锂离子电池，包括硅碳复合负极材料或上述硅碳复合负极材料的制备方法制备的负极材料。
本申请的技术方案至少具有以下有益的效果：
本申请提供的硅碳复合负极材料中，硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度，硅基活性粒子晶粒较小，能有效降低硅体积膨胀，提升循环性能。其他的有益效果会在具体实施方式中说明。
附图说明
图1为本申请实施例提供的硅碳复合负极材料的扫描电镜图片；
图2为本申请实施例提供的硅碳复合负极材料的另一扫描电镜图片；
图3为本申请实施例提供的硅碳复合负极材料中的硅基活性粒子的透射电镜高分辨图片；
图4为本申请实施例提供的硅碳复合负极材料的制备方法的流程示意图。
图5为本申请实施例提供的硅碳复合负极材料的制备方法的又一流程示意图。
具体实施方式
以下所述是本申请实施例的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本申请实施例原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也视为本申请实施例的保护范围。
现有的锂离子电池由于具备能量密度大、输出功率高、循环寿命长和环境污染小等优点而被广泛应用于电动汽车以及消费类电子产品中。为了提高电池能量密度，硅负极材料的研究和开发日趋成熟。但是硅负极材料脱嵌锂过程中体积膨胀较大(>300％)，硅负极材料在充放电过程中会粉化从集流体上掉落，使得活性物质与集流体之间失去接触，导致电化学性能变差，容量衰减、循环稳定性下降，难以得到商业应用。为了提高硅负极材料的导电性和循环稳定性，可以对硅材料自身改性，来提高硅负极材料的导电性和循环稳定性。
第一方面，从硅材料自身改性方向出发，本申请提供的硅碳复合负极材料，硅碳复合负极材料包括硅基活性粒子、导电材料及碳包覆层。
在一些实施方式中，碳包覆层位于硅基活性粒子表面。
在一些实施方式中，碳包覆层位于导电材料表面。
在一些实施方式中，碳包覆层同时位于硅基活性粒子和导电材料表面。
当使用CuKα射线对硅基活性粒子作X射线衍射测量时，硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度。
可以理解地，当X射线入射到小晶体时，其衍射线条将变得弥散而宽化，晶体的晶粒越小，X射线衍射谱带的宽化程度就越大。因此，本申请负极材料中的硅基活性粒子是晶粒较小的硅基活性粒子，能有效降低硅体积膨胀，提升循环性能。当硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度低于0.5时，硅基活性粒子的晶粒过大，硅活性粒子体积膨胀较大，不利于负极材料性能提升。优选地，硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.6度。
第二方面，本申请还提供一种硅碳复合负极材料，硅碳复合负极材料为核壳结构，包括硅基活性粒子及包覆于所述硅基活性粒子至少部分表面的碳包覆层。
当使用CuKα射线对所述硅碳复合负极材料作X射线衍射测量时，所述硅碳复合负极材料在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度。
在一些实施方式中，硅基活性粒子包括Si、SiO x及硅合金中的至少一种，其中0<x≤2；但并不限于上述列举的硅基活性物质，其他本领域常用的硅基活性物质也适用，比如，碳包覆的硅氧化物、硅掺杂半导体或其他含硅化合物。示例性地，硅基活性粒子可以是Si、SiO、SiO 2、硅锂合金、硅镁合金等等。在一些优选地实施方式中，硅基活性粒子的表面存在SiO x硅氧化物，可以有效抑制硅的体积膨胀，改善包括该负极活性材料的负极的效率和循环寿命。
在一些实施方式中，硅基活性粒子中的Si 4+的质量百分比含量为0.05％～5％，具体的，可以为0.05％、0.1％、0.2％、0.3％、0.4％、0.5％、1％、1.5％、2％、2.5％、3％、3.5％、4％、4.5％、5％等等。需要说明的是，由于硅基活性粒子中存在Si 4+，在硅脱嵌锂过程中，可以作为第二非活性相，当含有Si 4+的第二非活性相以细小弥散的微粒均匀分布于硅基活性粒子中时，将会产生显著的强化作用，第二非活性相在硅体积膨胀过程中起着结构稳定作用，可以有效抑制硅的体积膨胀，降低膨胀率，提升电池的循环稳定性。研究发现，当硅基活性粒子中的Si 4+的质量百分比含量超过5％时，负极材料的容量和首次效率会降低。
在一些实施方式中，如图1～图2所示，硅基活性粒子的中值粒径为5nm～120nm，具体可以是5nm、10nm、20nm、25nm、30nm、35nm、40nm、50nm、60nm、70nm、80nm、90nm、100nm、110nm或120nm等，但并不限于上述列举。优选地，硅基活性粒子的中值粒径为5nm～80nm，可以理解地，硅基活性粒子粒径的尺寸越小，材料性能会越好，综合考虑制备极小粒径的硅基活性粒子的工艺成本，硅基活性粒子的中值粒径更优选为5nm～40nm。
通过多次试验发现，纳米级的硅基活性粒子，其表面能高，表面原子排列混乱，具有较好的延展性与稳定性，粒子的结构性强，可以抑制硅体积膨胀。但由于纳米级硅基活性粒子有较大的表面能，在充放电过程中容易发生团聚， 因此，在本申请提供的复合负极材料中，硅基活性粒子之间设有导电材料，且碳包覆层包覆硅基活性粒子及导电材料，可以抑制团聚现象发生，并减少硅基活性粒子与电解液的直接接触。硅基活性粒子具有较大的比表面积，在充放电过程中表面容易生成钝化膜，大量消耗锂离子，减少电解液中锂离子浓度，降低电池可逆电容量，因此在包覆碳包覆层后，能够减少硅基活性粒子与电解液的直接接触，减少钝化膜生成，提升电池可逆电容量。如图3所示，硅基活性粒子可以是由一个晶粒组成的单晶硅纳米颗粒，和/或，由多个晶粒组成的多晶硅纳米颗粒。
在一些实施方式中，采用纳米压痕仪测试方法，硅基活性粒子用纳米压痕法测定的硬度为3Gpa～20Gpa，具体可以是3Gpa、5Gpa、8Gpa、12Gpa、15Gpa、18Gpa或20Gpa等，但并不限于上述列举。通过多次试验发现，硅基活性粒子硬度在上述范围内时，因为其具有较强的刚性，粒子结构稳定性强，可以抵御一定的体积膨胀应力，从而降低膨胀，提升电池循环稳定性。当硬度高于20Gpa时，颗粒表面之间的化学键能非常大，锂离子嵌入与脱出需要打开键合的能垒更高，导致锂离子嵌入困难，不利于负极材料性能改善。
在一些实施方式中，导电材料包括石墨片、碳纳米管、碳纤维和石墨烯中的至少一种。但并不限于上述列举的导电材料，其他本领域常用的导电材料比如焦炭、炭黑、碳微球也适用。石墨片具体可以是天然鳞片石墨，碳纤维可以是天然碳纤维或合成碳纤维。
在一些实施方式中，碳包覆层的厚度为50nm～2500nm，具体可以是50nm、100nm、200nm、300nm、400nm、500nm、600nm、700nm、800nm、1000nm、1200nm、1500nm、2000nm或2500nm等，但并不限于上述列举。包覆在硅基活性粒子及导电材料外的碳包覆层能够减少硅基活性粒子与电解液接触，减少钝化膜生成，提升电池可逆电容量。碳包覆层的厚度越厚，保护作用也好，确保结构更加稳定性；但是碳包覆层过厚，碳占比过大，硅碳复合材料的容量会过低，优选地，可以考虑将碳包覆层的厚度控制在100nm～1500nm。
在一些实施方式中，硅基复合负极材料具有核壳结构，内核包括硅基活性粒子及导电材料，外壳包括碳包覆层。硅基复合负极材料的粒子也可以呈球型或类球型。其中，所述导电材料嵌设于所述硅基活性粒子之间。
在一些实施方式中，硅基复合负极材料的中值粒径为5μm～30μm，其中值粒径具体可以是5μm、8μm、10μm、12μm、15μm、18μm、20μm、23μm、25μm、28μm或30μm等等，但并不限于上述列举。优选地，硅基复合负极材料的中值粒径为8μm～20μm。
在一些实施方式中，硅基复合负极材料的比表面积为0.5m 2/g～10m 2/g，其比表面积具体可以是0.5m 2/g、1m 2/g、2m 2/g、3m 2/g、4m 2/g、5m 2/g、6m 2/g、7m 2/g、8m 2/g、9m 2/g或10m 2/g等等，但并不限于上述列举。优选地，硅基复合负极材料的比表面积为1m 2/g～6m 2/g。可以理解地，比表面积越小越好，过大的比表面积容易导致SEI膜形成，消耗不可逆锂盐过多，降低电池的首次效率低，综合考虑制备工艺的成本，将比表面积控制在1m 2/g～6m 2/g。
在一些实施方式中，硅基复合负极材料的粉体压实密度为0.4g/cm 3～1.2g/cm 3，其粉体压实密度具体可以是0.4g/cm 3、0.5g/cm 3、0.6g/cm 3、0.7g/cm 3、0.8g/cm 3、0.9g/cm 3、1.0g/cm 3、1.1g/cm 3、或1.2g/cm 3等等，但并不限于上述列举。优选地，硅基复合负极材料的粉体压实密度为0.5g/cm 3～0.9g/cm 3。
在一些实施方式中，硅基复合负极材料中的碳元素的质量百分比为15％～65％，硅基活性粒子的质量百分比为15％～70％；导电材料的质量百分比为5％～70％。
第三方面，本申请还提供一种硅碳复合负极材料的制备方法，如图4所示，方法包括以下步骤：
S10，将硅基活性粒子加入有机溶剂中，分散得到前驱体溶液，其中，当使用CuKα射线对硅基活性粒子作X射线衍射测量时，硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度；
S20，往前驱体溶液中加入导电材料及碳源前驱体，得到负极材料前驱体；
S30，对负极材料前驱体进行热处理，得到硅基复合负极材料，硅碳复合负极材料包括硅基活性粒子、导电材料及碳包覆层，碳包覆层形成于硅基活性粒子和/或导电材料表面。
在上述方案中，通过控制硅基活性粒子自身的性能参数，使得硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度，在制备过程中，将硅基活性粒子、导电材料以及碳源前驱体混合于溶剂内，再通过热处理，在硅基活性粒子及导电材料的表面包覆一层含碳包覆层，可以抑制团聚现象发生，并减少硅基活性粒子与电解液的直接接触。最终制得的负极材料有利于抑制硅的体积膨胀，降低负极膨胀率，改善负极的充放电效率，提升电池循环性能。
选用的硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度，硅基活性粒子晶粒较小，能有效降低硅体积膨胀，提升循环性能。当硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度低于0.5，硅活性粒子的晶粒过大，硅活性粒子体积膨胀较大，不利于负极材料性能提升。
以下结合实施例详细介绍本方案：
步骤S10，将硅基活性粒子加入有机溶剂中，分散得到前驱体溶液。
在一些实施方式中，硅基活性粒子包括Si、SiO x及硅合金中的至少一种，其中0<x≤2。硅基活性粒子的中值粒径为5nm～120nm，具体可以是5nm、10nm、20nm、25nm、30nm、35nm、40nm、50nm、60nm、70nm、80nm、90nm、100nm、110nm或120nm等，但并不限于上述列举。优选地，硅基活性粒子的中值粒径为5nm～80nm。通过多次试验发现，纳米级的硅基活性粒子，其表面能高，表面原子排列混乱，具有较好的延展性与稳定性，粒子的结构性强，可以抑制硅体积膨胀。更优选地，硅基活性粒子的中值粒径为5nm～40nm。
在一些实施方式中，硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度具体可以为0.52、0.65、0.71、0.75、0.81、0.86、0.98等，但并不限于上述列举。需要说明的是，当X射线入射到小晶体时，其衍射线条将变得弥散而 宽化，晶体的晶粒越小，X射线衍射谱带的宽化程度就越大，因此，硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度时，硅基活性粒子的晶粒较小，能有效降低硅体积膨胀，提升循环性能。优选地，硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.6度。
在一些实施方式中，硅基活性粒子中的Si 4+的质量百分比含量可以为0.05％、0.1％、0.2％、0.3％、0.4％、0.5％、1％、1.5％、2％、2.5％、3％、3.5％、4％、4.5％、5％等等。需要说明的是，由于硅基活性粒子中存在Si 4+，在硅脱嵌锂过程中，可以作为第二非活性相，当含有Si 4+的第二非活性相以细小弥散的微粒均匀分布于硅基活性粒子中时，将会产生显著的强化作用，第二非活性相在硅体积膨胀过程中起着结构稳定作用，可以有效抑制硅的体积膨胀，降低膨胀率，提升电池的循环稳定性。
在一些实施方式中，采用纳米压痕仪测试方法，硅基活性粒子在6mN力度下测得的硬度为3Gpa～20Gpa，具体可以是3Gpa、5Gpa、8Gpa、12Gpa、15Gpa、18Gpa或20Gpa等，但并不限于上述列举。硅基活性粒子硬度在上述范围内时，因为其具有较强的刚性，粒子结构稳定性强，可以抵御一定的体积膨胀应力，从而降低膨胀，提升电池循环稳定性。
在一些实施方式中，有机溶剂包括甲醇、乙醇、乙二醇、丙醇、异丙醇、丙三醇、正丁醇、异丁醇和戊醇中的至少一种。
在一些实施方式中，在步骤S10中，还需要往有机溶剂中加入表面活性剂，表面活性剂包括聚乙烯醇(PVA)、正十八酸、聚乙二醇(PEG)、月桂酸、聚丙烯酸(PAA)、十二烷基苯磺酸钠(SDBS)、正二十酸、聚氯乙烯(PVC)和聚乙烯吡咯烷酮(PVP)中的至少一种。可以理解地，加入表面活性剂，可以加速硅基活性粒子的分散，避免硅基活性粒子团聚。
在一些实施方式中，在进行分散得到前驱体溶液过程中，可以采用磁力搅拌、机械搅拌等，也可以采用超声分散、研磨分散等，优选为研磨分散，从而使得硅基活性粒子能够分散开，避免硅基活性粒子团聚在一起，并且可以使得硅基活性粒子分散为较小的单晶硅纳米颗粒。需要说明的是，在制备硅基活性粒子过程中，可以通过控制硅粒子的研磨时间来增加Si 4+的质量百分比含量，一般来说，研磨时间越长，Si 4+的质量百分比含量越高。
步骤S20，往前驱体溶液中加入导电材料及碳源前驱体，得到负极材料前驱体。
在一些实施方式中，硅基活性粒子、导电材料和碳源前驱体的质量比为(10～70)：(5～30)：(15～40)。具体硅基活性粒子、导电材料和碳源前驱体的质量比可以为40:10:40、60:10:30、50:20:25、70:5:25、55:10:30等等。但并不限于上述列举。
在一些实施方式中，导电材料包括石墨片、碳纳米管、碳纤维和石墨烯中的至少一种。但并不限于上述列举的导电材料，其他本领域常用的导电材料比如焦炭、炭黑、碳微球也适用。石墨片具体可以是天然鳞片石墨，碳纤维可以是天然碳纤维或合成碳纤维。
在一些实施方式中，碳源前驱体包括蔗糖、葡萄糖、聚乙烯、聚乙烯醇、聚乙二醇、聚苯胺、环氧树脂、酚醛树脂、糠醛树脂、丙烯酸树脂、聚环氧乙烷、聚偏氟乙烯、聚丙烯腈、聚氯乙烯和沥青中的至少一种。
在一些实施方式中，碳源前驱体的中值粒径为1μm～50μm，其中值粒径具体可以是1μm、5μm、8μm、10μm、12μm、15μm、18μm、20μm、25μm、30μm、35μm、40μm、45μm或50μm等等，但并不限于上述列举。优选地，碳源前驱体的中值粒径为1μm～20μm。
在一些实施方式中，往前驱体溶液中加入导电材料及碳源前驱体，搅拌均匀后，还可以进行分离处理，分离处理方式具体可以是常压过滤、减压过滤、离心过滤等方式，分离处理得到的固体材料经过干燥处理得到负极材料前驱体；
在一些实施方式中，干燥处理的温度为25℃～200℃，具体可以是25℃、50℃、75℃、100℃、125℃、150℃、175℃或200℃等等，但并不限于上述列举。
在一些实施方式中，干燥处理的时间为1h～15h，具体可以是1h、2h、3h、4h、5h、7h、9h、10h、12h或15h等等，但并不限于上述列举。
在一些实施方式中，干燥处理方式具体可以是炉内烘干、喷雾干燥、真空干燥、冷冻干燥等，本实施例中的干燥处理可以尽可能地将前驱体溶液中的溶剂去除。干燥后的负极材料前驱体是由碳源前驱体包覆后的硅基活性粒子及导电材料，干燥后的负极材料前驱体可以送入高温箱式炉内进行热处理，使得碳源前驱体碳化形成碳包覆层。
步骤S30，对负极材料前驱体进行热处理，得到硅基复合负极材料。
在一些实施方式中，热处理的方式具体可以是烧结处理、热压烧结、真空烧结。热处理的温度为500℃～1200℃，具体可以是500℃、600℃、700℃、800℃、900℃、1000℃、1200℃、1200℃等。优选地，热处理的温度为800℃～1200℃。
在一些实施方式中，热处理的时间1h～9h，具体可以是1h、2h、3h、4h、5h、6h、7h、8h、9h等。
在一些实施方式中，热处理时的升温速率为1℃/min～15℃/min，具体可以是1℃/min、3℃/min、5℃/min、6℃/min、7℃/min、8℃/min、9℃/min、10℃/min、12℃/min或15℃/min，优选地，热处理时的升温速率为5℃/min～10℃/min。
在一些实施方式中，热处理过程通有保护气，保护气为氮气、氦气、氖气、氩气或氪气中的至少一种。
在一些实施方式中，制备得到的硅基复合负极材料具有核壳结构，内核为硅基活性粒子及导电材料，外壳为碳包覆层。硅基复合负极材料的粒子也可以呈球型或类球型，硅基复合负极材料的中值粒径为5μm～30μm，其中值粒径具体可以是5μm、8μm、10μm、12μm、15μm、18μm、20μm、23μm、25μm、28μm或30μm等等，但并不限于上述列举。
由于纳米级硅基活性粒子有较大的表面能，在充放电过程中容易发生团聚，因此，在本申请提供的复合负极材料中，硅基活性粒子之间设有导电材料，且在硅基活性粒子及导电材料的表面包覆一层含碳包覆层，可以抑制团聚现象发 生，并减少硅基活性粒子与电解液的直接接触。硅基活性粒子具有较大的比表面积，在充放电过程中表面容易生成钝化膜，大量消耗锂离子，减少电解液中锂离子浓度，降低电池可逆电容量，因此在包覆碳包覆层后，能够减少硅基活性粒子与电解液的直接接触，减少钝化膜生成，提升电池可逆电容量。
在一些实施方式中，硅基复合负极材料的中值粒径为8μm～20μm。包覆在硅基活性粒子及导电材料外的碳包覆层能够减少硅基活性粒子与电解液接触，减少钝化膜生成，提升电池可逆电容量。
在一些实施方式中，硅基复合负极材料的比表面积为0.5m 2/g～10m 2/g，其比表面积具体可以是0.5m 2/g、1m 2/g、2m 2/g、3m 2/g、4m 2/g、5m 2/g、6m 2/g、7m 2/g、8m 2/g、9m 2/g或10m 2/g等等，但并不限于上述列举。优选地，硅基复合负极材料的比表面积为1m 2/g～6m 2/g。
在一些实施方式中，硅基复合负极材料的粉体压实密度为0.4g/cm 3～1.2g/cm 3，其粉体压实密度具体可以是0.4g/cm 3、0.5g/cm 3、0.6g/cm 3、0.7g/cm 3、0.8g/cm 3、0.9g/cm 3、1.0g/cm 3、1.1g/cm 3、或1.2g/cm 3等等，但并不限于上述列举。优选地，硅基复合负极材料的粉体压实密度为0.5g/cm 3～0.9g/cm 3。
在一些实施方式中，硅基复合负极材料中的碳元素的质量百分比为15％～65％，硅基活性粒子的质量百分比为15％～70％；导电材料的质量百分比为5％～70％。
在本方案中，采用上述制备方法制得的硅碳复合负极材料，在硅基活性粒子及导电材料表面包覆碳包覆层，可以抑制材料在循环过程中的膨胀。其核结构中的硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度，具有较小的晶粒，能有效降低硅体积膨胀，提升循环性能。其次，纳米级的硅基活性粒子，硅基活性粒子的表面可能存在SiO x氧化物，可以有效抑制硅的体积膨胀，改善包括该负极活性材料的负极的效率和循环寿命；进一步地，硅基活性粒子中的Si 4+质量百分比含量为0.05％～5％，可以有效抑制硅的体积膨胀，降低膨胀率，提升循环。最后，硅基活性粒子硬度较大，具有较强的刚性，可以有效抵御一定的体积膨胀的应力，有利于保持负极材料结构稳定性，从而降低膨胀率，提升电池循环性能。
第四方面，本申请还提供一种硅碳复合负极材料的制备方法，如图5所示，方法包括以下步骤：
S10’，将硅基活性粒子加入有机溶剂中，分散得到前驱体溶液，其中，当使用CuKα射线对硅基活性粒子作X射线衍射测量时，硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度；
S20’，往前驱体溶液中加入碳源前驱体，得到负极材料前驱体；及
S30’，对负极材料前驱体进行热处理，得到硅基复合负极材料，硅碳复合负极材料包括硅基活性粒子及碳包覆层，所述碳包覆层形成于所述硅基活性粒子的至少部分表面。
在上述方案中，通过控制硅基活性粒子自身的性能参数，使得硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度，在制备过程中， 将硅基活性粒子以及碳源前驱体混合于溶剂内，再通过热处理，在硅基活性粒子的表面包覆一层含碳包覆层，可以抑制团聚现象发生，并减少硅基活性粒子与电解液的直接接触。最终制得的负极材料有利于抑制硅的体积膨胀，降低负极膨胀率，改善负极的充放电效率，提升电池循环性能。
与第三方面所述的制备方法不同的是，本实施方式中，前驱体溶液中不需要加入导电材料，其他制备工艺与第二方面所述的方法相同，在此不再赘述。在一些实施方式中，步骤S20’中，硅基活性粒子和碳源前驱体的质量比为(10～70)：(15～40)。具体硅基活性粒子和碳源前驱体的质量比可以为40:40、60:30、50:25、70:25、55:30等等。但并不限于上述列举。
第五方面，本申请还提供一种锂离子电池，所述锂离子电池包括负极极片、正极极片、隔膜及非水电解液，所述负极极片包括集流体和涂覆在所述集流体上的如上述的硅碳复合负极材料或根据上述硅碳复合负极材料的制备方法制备的负极材料。
下面分多个实施例对本申请实施例进行进一步的说明。其中，本申请实施例不限定于以下的具体实施例。在不变主权利的范围内，可以适当的进行变更实施。
实施例1
(1)将中值粒径为20nm的硅粉分散在乙二醇溶液中，超声分散10min后加入1.5wt％PVP表面活性剂，超声分散20min得到分散溶液，再将分散溶液置于球磨机中研磨分散4小时，得到前驱体溶液。
(2)往前驱体溶液中加入长径比500的单壁碳纳米管和沥青，硅粉：单壁碳纳米管：沥青的质量比为60：10：30，搅拌、分散均匀后进行干燥处理，得到干燥物料；
(3)将干燥物料置于高温箱式炉中，通入氮气，在1000℃条件下热处理后，进行粉碎、通过500目筛过筛，制得硅碳复合材料。
本实施例中，硅粉中的硅粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.98度，硅粉中的Si 4+的质量百分比含量为1.5％，硅粉中的硅粒子硬度18Gpa；所得的硅碳复合负极材料的中值粒径约为6.2μm，比表面积为10m 2/g，碳的质量百分比含量为20％，碳包覆层厚度为300nm。
实施例2
(1)将中值粒径为30nm的硅粉分散在正丁醇溶液中，超声分散10min后加入2.0wt％PEG表面活性剂，超声分散30min得到分散溶液，再将分散溶液置于球磨机中研磨分散8小时，得到前驱体溶液。
(2)往前驱体溶液中加入长径比100的单壁碳纳米管和沥青，硅粉：单壁碳纳米管：沥青的质量比为60：10：30，搅拌、分散均匀后进行干燥处理，得到干燥物料；
(3)将干燥物料加入到高温箱式炉中，通入氮气，在800℃条件下热处理 后，进行粉碎、通过500目筛过筛，制得硅碳复合材料。
本实施例中，硅粉中的硅粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.81度，硅粉中的Si 4+的质量百分比含量为0.5％，硅粉中的硅粒子硬度15Gpa；所得的硅碳复合负极材料的中值粒径约为10μm，比表面积为9m 2/g，碳的质量百分比含量为30％，碳包覆层厚度为100nm。
实施例3
(1)将中值粒径为40nm的硅粉分散在异丙醇溶液中，超声分散10min后加入3.0wt％PVA表面活性剂，超声分散30min得到分散溶液，再将分散溶液置于球磨机中研磨分散8小时，得到前驱体溶液。
(2)往前驱体溶液中加入石墨烯和葡萄糖，硅粉：石墨烯：葡萄糖的质量比为70：5：25，搅拌、分散均匀后进行干燥处理，得到干燥物料；
(3)将干燥物料加入到高温箱式炉中，通入氮气，在900℃条件下热处理后，进行粉碎、通过500目筛过筛，制得硅碳复合材料。
本实施例中，硅粉中的硅粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.71度，硅粉中的Si 4+的质量百分比含量为1.1％，硅粉中的硅粒子硬度10Gpa；所得的硅碳复合负极材料的中值粒径约为24μm，比表面积为6m 2/g，碳的质量百分比含量为22％，碳包覆层厚度为200nm。
实施例4
(1)将中值粒径为80nm的硅粉分散在乙二醇溶液中，超声分散10min后加入2.5wt％PEG表面活性剂，超声分散30min得到分散溶液，再将分散溶液置于球磨机中研磨分散8小时，得到前驱体溶液。
(2)往前驱体溶液中加入中值粒径为9μm的石墨片和蔗糖，硅粉：石墨片：蔗糖的质量比50:20：25，搅拌、分散均匀后进行干燥处理，得到干燥物料；
(3)将干燥物料加入到高温箱式炉中，通入氮气，在900℃条件下热处理后，进行粉碎、通过500目筛过筛，制得硅碳复合材料。
本实施例中，硅粉中的硅粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.62度，硅粉中的Si 4+的质量百分比含量为0.2％，硅粉中的硅粒子硬度8Gpa；所得的硅碳复合负极材料的中值粒径约为18μm，比表面积为6m 2/g，碳的质量百分比含量为18％，碳包覆层厚度为800nm。
实施例5
(1)将中值粒径为20nm的硅粉分散在乙二醇溶液中，超声分散10min后加入1.5wt％PVP表面活性剂，超声分散20min得到分散溶液，再将分散溶液置于球磨机中研磨分散4小时，得到前驱体溶液。
(2)往前驱体溶液中加入长径比500的单壁碳纳米管和沥青，硅粉：单壁 碳纳米管：沥青的质量比为60：10：30，搅拌、分散均匀后进行干燥处理，得到干燥物料；
(3)将干燥物料置于高温箱式炉中，通入氮气，在1000℃条件下热处理后，进行粉碎、通过500目筛过筛，制得硅碳复合材料。
本实施例中，硅粉中的硅粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.98度，硅粉中的Si 4+的质量百分比含量为0.01％，硅粉中的硅粒子硬度18Gpa；所得的硅碳复合负极材料的中值粒径约为6.6μm，比表面积为9.8m 2/g，碳的质量百分比含量为21％，碳包覆层厚度为300nm。
实施例6
(1)将中值粒径为20nm的硅粉分散在乙二醇溶液中，超声分散10min后加入1.5wt％PVP表面活性剂，超声分散20min得到分散溶液，再将分散溶液置于球磨机中研磨分散4小时，得到前驱体溶液。
(2)往前驱体溶液中加入长径比500的单壁碳纳米管和沥青，硅粉：单壁碳纳米管：沥青的质量比为60：10：30，搅拌、分散均匀后进行干燥处理，得到干燥物料；
(3)将干燥物料置于高温箱式炉中，通入氮气，在1000℃条件下热处理后，进行粉碎、通过500目筛过筛，制得硅碳复合材料。
本实施例中，硅粉中的硅粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.98度，硅粉中的Si 4+的质量百分比含量为1.5％，硅粉中的硅粒子硬度2Gpa；所得的硅碳复合负极材料的中值粒径约为6.6μm，比表面积为9.8m 2/g，碳的质量百分比含量为21％，碳包覆层厚度为300nm。
实施例7
按照与实施例1基本相同的方法制备纳米硅基复合负极材料，区别在于：置于球磨机中研磨分散8小时。
本实施例中，硅粉中的硅粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.98度，硅粉中的Si 4+的质量百分比含量为8.5％，硅粉中的硅粒子硬度14Gpa；所得的硅碳复合负极材料的中值粒径约为6.6μm，比表面积为7.9m 2/g，碳的质量百分比含量为21％，碳包覆层厚度为300nm。
实施例8
按照与实施例1基本相同的方法制备纳米硅基复合负极材料，区别在于：置于球磨机中研磨分散8小时。
本实施例中，硅粉中的硅粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.98度，硅粉中的Si 4+的质量百分比含量为3.5％，硅粉中的硅粒子硬度28Gpa；所得的硅碳复合负极材料的中值粒径约为6.5μm，比表面积为8.8m 2/g，碳的质量百分比含量为20％，碳包覆层厚度为300nm。
实施例9
按照与实施例1基本相同的方法制备纳米硅基复合负极材料，区别在于：置于球磨机中研磨分散2小时。
本实施例中，硅粉中的硅粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.98度，硅粉中的Si 4+的质量百分比含量为0.8％，硅粉中的硅粒子硬度18Gpa；所得的硅碳复合负极材料的中值粒径约为5.8μm，比表面积为10m 2/g，碳的质量百分比含量为20％，碳包覆层厚度为300nm。
实施例10
(1)将中值粒径为20nm的硅粉分散在乙二醇溶液中，超声分散10min后加入1.5wt％PVP表面活性剂，超声分散20min得到分散溶液，再将分散溶液置于球磨机中研磨分散4小时，得到前驱体溶液。
(2)往前驱体溶液中加入沥青，硅粉：沥青的质量比为60：30，搅拌、分散均匀后进行干燥处理，得到干燥物料；
(3)将干燥物料置于高温箱式炉中，通入氮气，在1000℃条件下热处理后，进行粉碎、通过500目筛过筛，制得硅碳复合材料。
本实施例中，硅粉中的硅粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.80度，硅粉中的Si 4+的质量百分比含量为0.8％，硅粉中的硅粒子硬度18Gpa；所得的硅碳复合负极材料的中值粒径约为6.3μm，比表面积为12m 2/g，碳的质量百分比含量为25％，碳包覆层厚度为350nm。
对比例1
按照与实施例1基本相同的方法制备纳米硅基复合负极材料，区别在于：采用180nm的硅粉，制得硅碳复合材料。
本对比例中，硅粉中的硅粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.32度，硅粉中的Si 4+的质量百分比含量为0.01％，硅粉中的硅粒子硬度2.5Gpa；所得的硅碳复合负极材料的中值粒径约为15μm，比表面积为6m 2/g，碳的质量百分比含量为18％，碳包覆层厚度为300nm。
对比例2
按照与实施例1基本相同的方法制备纳米硅基复合负极材料，区别在于：
本对比例中，硅粉中的硅粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.35度，硅粉中的Si 4+的质量百分比含量为4.5％，硅粉中的硅粒子硬度2.5Gpa；所得的硅碳复合负极材料的中值粒径约为22μm，比表面积为9m 2/g，碳的质量百分比含量为36％，碳包覆层厚度为800nm。
测试方法
采用以下方法测试电化学循环性能：将制得的硅碳复合负极材料、导电剂和粘结剂按质量百分比94：1：5将他们溶解在溶剂中混合，控制固含量在50％，涂覆于铜箔集流体上，真空烘干、制得负极极片；然后将传统成熟工艺制备的三元正极极片、1mol/L的LiPF6/(碳酸亚乙酯)EC+(碳酸二甲酯)DMC+(碳酸甲乙酯)EMC(v/v＝1:1:1)电解液、Celgard2400隔膜、外壳采用常规生产工艺装配18650圆柱单体电池。圆柱电池的充放电测试在武汉金诺电子有限公司LAND电池测试***上，在常温条件，0.2C恒流充放电，充放电电压限制在2.75～4.2V，进行充放电测试，得到首次可逆容量、首圈充电容量和首圈放电容量。首次库伦效率＝首圈放电容量/首圈充电容量。
重复循环50周，利用千分尺测量锂离子电池此时极片的厚度为H1，循环50圈后极片膨胀率＝(H1-H0)/H0×100％。
重复100周循环，记录放电容量，作为锂离子电池的剩余容量；容量保持率＝剩余容量/初始容量*100％。
采用X射线衍射法测试硅粉中硅粒子在(111)面处的X射线衍射角(2θ)的半宽度。
硬度测试：通过纳米压痕仪测试，采用载荷0.6N，控制压痕深度0.5um，进行压痕硬度测试。
Si 4+含量测试：采用X射线电子能谱分析仪来测定硅粉中Si 4+的含量。
上述性能测试的结果如下：
表1.性能比对结果表
Figure PCTCN2021123543-appb-000001
Figure PCTCN2021123543-appb-000002
如表1所示，实施例5与实施例1不同的是采用的硅基活性粒子中的Si 4+的质量百分比含量为0.01％，硅粒子在充放电过程中，负极材料制造的电极板的膨胀率、循环寿命和首次效率均低于实施例1。
实施例6与实施例1不同的是采用的硅基活性粒子的硬度仅为2Gpa，小于实施例1中硅粒子的硬度，硅粒子结构稳定性较差，在充放电过程中难以抵御体积膨胀应力，电池循环稳定性降低。
实施例7与实施例1不同的是采用的硅基活性粒子中的Si 4+的质量百分比含量为8.5％，Si 4+的质量百分比含量过高，负极材料的容量和首次效率会降低。
实施例8与实施例1不同的是采用硅粉中的硅基活性粒子硬度为28Gpa，硬度过大，颗粒表面之间的化学键能非常大，锂离子嵌入与脱出需要打开键合的能垒更高，导致锂离子嵌入困难，不利于负极材料循环性能改善。
实施例9与实施例1不同的是在步骤(1)中的分散溶液置于球磨机中研磨分散2小时，研磨时间过短，而实施例1的硅粒子研磨时间为6h，可以发现，通过控制硅粒子的研磨时间可以增加Si 4+的质量百分比含量，一般来说，研磨时间越长，Si 4+的质量百分比含量越高。
实施例10与实施例1不同的是在制备过程中未加入导电材料，导致电池的首次库伦效率及首次可逆容量相比于实施例1有所下降。
对比例1～2采用的硅基活性粒子(111)面半宽度<0.5，且硬度低于3Gpa，该硅基活性粒子制成的负极材料电极板的膨胀率、循环寿命和首次效率均差于实施例1～6制得负极材料。
综上所述，通过控制硅基活性粒子自身的性能参数，使得硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度，硅基活性粒子中的Si 4+的质量百分比含量为0.05％～5％，硅基活性粒子的硬度控制在3Gpa～20Gpa，有利于抑制硅的体积膨胀，改善负极的效率和循环寿命，并且可以有效抵御一定的体积膨胀的应力，从而降低膨胀率，提升电池循环性能。
本申请虽然以较佳实施例公开如上，但并不是用来限定权利要求，任何本领域技术人员在不脱离本申请构思的前提下，都可以做出若干可能的变动和修改，因此本申请的保护范围应当以本申请权利要求所界定的范围为准。

Claims (14)

  1. 一种硅碳复合负极材料，其特征在于，所述硅碳复合负极材料包括硅基活性粒子、导电材料及碳包覆层；所述碳包覆层位于所述硅基活性粒子和/或所述导电材料表面；
    当使用CuKα射线对所述硅基活性粒子作X射线衍射测量时，所述硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度。
  2. 一种硅碳复合负极材料，其特征在于，所述硅碳复合负极材料为核壳结构，包括硅基活性粒子及包覆于所述硅基活性粒子至少部分表面的碳包覆层；
    当使用CuKα射线对所述硅碳复合负极材料作X射线衍射测量时，所述硅碳复合负极材料在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度。
  3. 根据权利要求1所述的硅碳复合负极材料，其特征在于，所述硅碳复合负极材料为核壳结构，内核包括所述硅基活性粒子及所述导电材料，所述导电材料嵌设于所述硅基活性粒子之间，外壳包括所述碳包覆层。
  4. 根据权利要求1～3任一项所述的硅碳复合负极材料，其特征在于，所述硅碳复合负极材料满足以下条件a～f的至少一者：
    a.所述硅基活性粒子包括Si、SiO x及硅合金中的至少一种，其中0<x≤2；
    b.所述硅基活性粒子的中值粒径为5nm～120nm；
    c.所述硅基活性粒子用纳米压痕法测定的硬度为3Gpa～20Gpa；
    d.所述硅基活性粒子中的Si 4+的质量百分比含量为0.05％～5％；
    e.所述导电材料包括石墨片、碳纳米管、碳纤维和石墨烯中的至少一种；
    f.所述碳包覆层的厚度为50nm～2500nm。
  5. 根据权利要求1或2所述的硅碳复合负极材料，其特征在于，所述硅碳复合负极材料满足以下条件a～f的至少一者：
    a.所述硅基复合负极材料的中值粒径为5μm～30μm；
    b.所述硅基复合负极材料的比表面积为0.5m 2/g～10m 2/g；
    c.所述硅基复合负极材料的粉体压实密度为0.4g/cm 3～1.2g/cm 3；
    d.所述硅基复合负极材料中的碳元素的质量百分比含量为15％～65％；
    e.所述硅基复合负极材料中的硅基活性粒子的质量百分比含量为15％～70％；
    f.所述硅基复合负极材料中的导电材料的质量百分比含量为5％～70％。
  6. 一种硅碳复合负极材料的制备方法，其特征在于，包括以下步骤：
    将硅基活性粒子加入有机溶剂中，分散得到前驱体溶液，其中，当使用CuKα射线对所述硅基活性粒子作X射线衍射测量时，所述硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度；
    往所述前驱体溶液中加入导电材料及碳源前驱体，得到负极材料前驱体；及
    对所述负极材料前驱体进行热处理，得到硅基复合负极材料，所述硅碳复 合负极材料包括硅基活性粒子、导电材料及碳包覆层，所述碳包覆层形成于所述硅基活性粒子和/或所述导电材料表面。
  7. 一种硅碳复合负极材料的制备方法，其特征在于，包括以下步骤：
    将硅基活性粒子加入有机溶剂中，分散得到前驱体溶液，其中，当使用CuKα射线对所述硅基活性粒子作X射线衍射测量时，所述硅基活性粒子在(111)面处的X射线衍射角(2θ)的半宽度大于或等于0.5度；
    往所述前驱体溶液中加入碳源前驱体，得到负极材料前驱体；及
    对所述负极材料前驱体进行热处理，得到硅基复合负极材料，所述硅碳复合负极材料包括硅基活性粒子及碳包覆层，所述碳包覆层形成于所述硅基活性粒子的至少部分表面。
  8. 根据权利要求6或7所述的制备方法，其特征在于，所述硅基复合负极材料满足以下条件a～d的至少一者：
    a.所述硅基活性粒子中的Si 4+的质量百分比含量为0.05％～5％；
    b.所述硅基活性粒子的中值粒径为5nm～120nm；
    c.所述硅基活性粒子的硬度为3Gpa～20Gpa；
    d.所述硅基活性粒子包括Si、SiO x及硅合金中的至少一种，其中0<x≤2。
  9. 根据权利要求6或7所述的制备方法，其特征在于，所述硅基复合负极材料满足以下条件a～e的至少一者：
    a.所述硅基复合负极材料的中值粒径为5μm～30μm；
    b.所述硅基复合负极材料的比表面积为0.5m 2/g～10m 2/g；
    c.所述硅基复合负极材料的粉体压实密度为0.4g/cm 3～1.2g/cm 3；
    d.所述硅基复合负极材料中的碳元素的质量百分比含量为15％～65％；
    e.所述硅基复合负极材料中的硅基活性粒子的质量百分比含量为15％～70％。
  10. 根据权利要求6、8或9任一项所述的制备方法，其特征在于，所述方法满足以下条件a～d的至少一者：
    a.所述硅基活性粒子、所述导电材料和所述碳源前驱体的质量比为(10～70)：(5～30)：(15～40)；
    b.所述导电材料包括石墨片、碳纳米管、碳纤维和石墨烯中的至少一种；
    c.所述碳源前驱体包括蔗糖、葡萄糖、聚乙烯、聚苯胺、酚醛树脂、聚氯乙烯和沥青中的至少一种；
    d所述硅基复合负极材料中的导电材料的质量百分比含量为5％～70％。
  11. 根据权利要求7、8或9任一项所述的制备方法，其特征在于，所述方法满足以下条件a～b的至少一者：
    a.所述硅基活性粒子和所述碳源前驱体的质量比为(10～70)：(15～40)；
    b.所述碳源前驱体包括蔗糖、葡萄糖、聚乙烯、聚苯胺、酚醛树脂、聚氯乙烯和沥青中的至少一种。
  12. 根据权利要求6或7所述的制备方法，其特征在于，在将硅基活性粒子分散在有机溶剂中后，所述方法还包括：
    往所述有机溶剂中加入表面活性剂，所述表面活性剂包括聚乙烯醇、正十八酸、聚乙二醇、月桂酸、聚丙烯酸、十二烷基苯磺酸钠、正二十酸、聚氯乙烯和聚乙烯吡咯烷酮中的至少一种；和/或，所述有机溶剂包括甲醇、乙醇、乙二醇、丙醇、异丙醇、丙三醇、正丁醇、异丁醇和戊醇中的至少一种。
  13. 根据权利要求6或7所述的制备方法，其特征在于，所述方法满足以下条件a～c的至少一者：
    a.所述热处理的温度为500℃～1200℃；
    b.所述热处理的时间1h～9h；
    c.所述热处理的升温速率为1℃/min～15℃/min。
  14. 一种锂离子电池，其特征在于，包括如权利要求1～5任一项所述的硅碳复合负极材料或根据权利要求6～13任一项所述硅碳复合负极材料的制备方法制备的负极材料。
PCT/CN2021/123543 2021-02-20 2021-10-13 硅碳复合负极材料及其制备方法、锂离子电池 WO2022174598A1 (zh)

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