WO2024031667A1 - 硅碳复合材料、其制备方法及包含该硅碳复合材料的二次电池 - Google Patents

硅碳复合材料、其制备方法及包含该硅碳复合材料的二次电池 Download PDF

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WO2024031667A1
WO2024031667A1 PCT/CN2022/112206 CN2022112206W WO2024031667A1 WO 2024031667 A1 WO2024031667 A1 WO 2024031667A1 CN 2022112206 W CN2022112206 W CN 2022112206W WO 2024031667 A1 WO2024031667 A1 WO 2024031667A1
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silicon
composite material
carbon
carbon composite
matrix particles
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PCT/CN2022/112206
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English (en)
French (fr)
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吴凯
李圆
董晓斌
吕子建
刘良彬
覃玉维
王家政
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/112206 priority Critical patent/WO2024031667A1/zh
Priority to CN202280005715.9A priority patent/CN117882228A/zh
Publication of WO2024031667A1 publication Critical patent/WO2024031667A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids

Definitions

  • the present application relates to the field of batteries, and specifically to a silicon-carbon composite material, a preparation method thereof, and a secondary battery containing the silicon-carbon composite material.
  • Secondary batteries have the characteristics of high capacity and long life, so they are widely used in electronic equipment, such as mobile phones, laptop computers, battery cars, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and electric tools etc. As secondary batteries have made great progress, higher requirements have been placed on the performance of secondary batteries. In order to increase the energy density of secondary batteries, the industry is currently considering the use of silicon-based negative active materials. However, although silicon-based materials have a higher gram capacity, their own expansion is large, which seriously affects the cycle performance of the battery.
  • This application was made in view of the above issues, and its purpose is to provide a silicon-carbon composite material, a preparation method thereof, and a secondary battery containing the silicon-carbon composite material, so that the secondary battery can operate at a higher energy density. while taking into account better cycle performance.
  • a first aspect of the present application provides a silicon-carbon composite material, which includes carbon matrix particles including a three-dimensional network cross-linked pore structure; and silicon-based nanoparticles, at least a portion of which is provided in the three-dimensional network cross-linked pore structure.
  • the carbon matrix particles of the present application have a stable porous skeleton structure, strong supporting capacity, high stress capability, and excellent mechanical properties and electrical conductivity; the carbon matrix particles include a three-dimensional network cross-linked pore structure, which can There is more space for setting silicon-based nanoparticles, which can be used to store a large amount of silicon; when porous carbon matrix particles are combined with silicon-based nanoparticles, the silicon-based nanoparticles are not prone to agglomeration and can be evenly dispersed in the pores of the carbon matrix particles; After the carbon matrix particles and silicon-based nanoparticles are combined, the conductivity of the silicon-carbon composite material can be improved, while the volume effect of silicon in the process of deintercalation of lithium can be alleviated, and the stress changes of the silicon-based nanoparticles can be fully withstood, ensuring that the silicon-carbon
  • the structural stability of the composite material improves the cycle stability and lithium storage capacity of the silicon-carbon composite material, thereby improving the cycle performance and energy density of the secondary battery
  • At least a portion of the pores in the surface region of the carbon matrix particle have a pore size that is greater than the pore size in the interior region of the carbon matrix particle.
  • the three-dimensional network cross-linked pore structure exhibits a layered distribution in the carbon matrix particles.
  • the powder compaction density of the silicon-carbon composite material tested after one powder pressing under a force of 20,000N is recorded as P 11 g/cm 3 .
  • the compacted density tested after 20 times of powder compaction is recorded as P 21 g/cm 3 , then the silicon carbon composite material satisfies: 1.00 ⁇ P 21 /P 11 ⁇ 1.20; optionally, 1.02 ⁇ P 21 /P 11 ⁇ 1.10.
  • the silicon-carbon composite material of this application has a specific structure, and the powder compaction density under the above test conditions meets specific requirements, so that the silicon-carbon composite material has a higher gram capacity while also having better pressure resistance. , effectively ensuring the structural stability of the negative electrode film layer, so that secondary batteries containing this material can have better cycle performance while having higher energy density.
  • the powder compaction density of the silicon-carbon composite material under a force of 20,000N is recorded as P 11 g/cm 3 , then the silicon-carbon composite material satisfies: 1.10 ⁇ P 11 ⁇ 1.40; optional Ground, 1.12 ⁇ P 11 ⁇ 1.35.
  • the total pore volume of the pores in the carbon matrix particles with a pore diameter greater than 100 nm is recorded as V 1 cm 3 /g, and the pore diameter in the carbon matrix particles is less than or equal to 100 nm.
  • the total pore volume of the pores is recorded as V 2 cm 3 /g, then the carbon matrix particles satisfy: 1 ⁇ V 2 /V 1 ⁇ 30; optionally, 3 ⁇ V 2 /V 1 ⁇ 25.
  • this application can ensure that the pore size distribution of the carbon matrix particles is moderate, which is conducive to subsequent silicon-containing precursors entering the pores of the carbon matrix particles and reducing silicon deposition on the carbon matrix. Risks on the particle surface; and it is conducive to the carbon matrix particles tending to be fully deposited, so that the specific surface area of the silicon-carbon composite particles formed after silicon is deposited is moderate and its reversible capacity can be guaranteed.
  • the total pore volume of pores with a pore diameter greater than 100 nm in the carbon matrix particles is recorded as V 1 cm 3 /g, then V 1 ⁇ 0.01, optionally, 0.01 ⁇ V 1 ⁇ 0.5.
  • the total pore volume of the pores in the carbon matrix particles with a pore diameter of 100 nm or less is recorded as V 2 cm 3 /g, then V 2 ⁇ 0.05, optionally ,0.05 ⁇ V 2 ⁇ 1.1.
  • the porosity of the carbon matrix particles is denoted as W, 40% ⁇ W ⁇ 80%; optionally, 50% ⁇ W ⁇ 70%.
  • the pores occupy an appropriate volume of the skeleton, which can not only ensure the stability of the skeleton structure, but also meet the capacity of depositing silicon.
  • the silicon-based nanoparticles are attached to the pores, and the silicon-based nanoparticles are attached to the pores.
  • the particles and porous carbon matrix particles can work synergistically to increase the capacity and conductivity of silicon-carbon composites.
  • the powder compaction density of the carbon matrix particles under a force of 50,000N is recorded as P g/cm 3 , 0.4 ⁇ P ⁇ 1.1; optionally, 0.6 ⁇ P ⁇ 0.9.
  • this application can make the negative electrode film layer have a higher compaction density, thereby ensuring that the secondary battery has a higher energy density.
  • the true density of the carbon matrix particles is expressed as ⁇ g/cm 3 , 1.7 ⁇ 2.5; optionally, 1.9 ⁇ 2.2.
  • the present application can make the negative electrode film layer have a relatively high specific capacity, thereby improving the energy density of the secondary battery.
  • the carbon matrix particles include one or more of graphite, soft carbon, and hard carbon.
  • the silicon-based nanoparticles include one or more of silicon oxide compounds, pre-lithium silicon oxide compounds, amorphous silicon, crystalline silicon and silicon-carbon composites; optionally, the silicon-based nanoparticles Nanoparticles include amorphous silicon.
  • the mass ratio of the silicon-based nanoparticles in the silicon-carbon composite material is greater than or equal to 40%; optionally, it is 40%-60%.
  • the mass ratio of silicon-based nanoparticles in the silicon-carbon composite material is within the above range, the capacity of the silicon-carbon composite material is relatively high.
  • the volume distribution particle size Dv10 of the silicon-carbon composite material satisfies: Dv10 ⁇ 5 ⁇ m; optionally, 3 ⁇ m ⁇ Dv10 ⁇ 5 ⁇ m.
  • the volume distribution particle size Dv50 of the silicon-carbon composite material satisfies: Dv50 ⁇ 10 ⁇ m; optionally, 5 ⁇ m Dv50 ⁇ 8 ⁇ m.
  • the volume distribution particle size Dv90 of the silicon-carbon composite material satisfies: Dv90 ⁇ 20 ⁇ m; optionally, 8 ⁇ m ⁇ Dv90 ⁇ 18 ⁇ m.
  • the particle size distribution of the silicon-carbon composite material satisfies: (Dv90-Dv10)/Dv50 ⁇ 1.6; optionally, 1.4 ⁇ (Dv90-Dv10)/Dv50 ⁇ 1.6.
  • the particle size of the silicon-carbon composite material of the present application meets the above range, the structure of the silicon-carbon composite material is relatively stable and the dynamic properties are relatively good, which is beneficial to improving the first Coulombic efficiency of the silicon-carbon composite material.
  • the specific surface area SSA of the silicon-carbon composite material satisfies: 2m 2 /g ⁇ SSA ⁇ 10m 2 /g; optionally, 3m 2 /g ⁇ SSA ⁇ 7m 2 /g.
  • the specific surface area SSA of the silicon-carbon composite material of the present application meets the above range, the range of the specific surface area is relatively moderate, and the dynamic properties of the material are good, which is beneficial to the first Coulombic efficiency of the material.
  • the second aspect of the present application provides a method for preparing a silicon-carbon composite material, which includes the following steps: mixing a cross-linked resin, a porogen and a solvent to form a mixed system.
  • the mixed system is preheated to volatilize the solvent and solidify the cross-linked resin to form a solid resin.
  • the solid resin is broken down to form granular resin.
  • the particulate resin is carbonized to volatilize the porogen and etch the particulate resin to form carbon matrix particles having a three-dimensional network cross-linked structure.
  • silicon-based nanoparticles are generated from a gas containing a silicon precursor, at least a portion of the silicon-based nanoparticles being attached to the pores of the carbon matrix particles.
  • the mass content of the cross-linked resin added is recorded as a1; based on the total mass of the mixed system, the mass content of the solvent added is recorded as a2;
  • the mixed system satisfies: 0.1 ⁇ a1/a2 ⁇ 10; optionally, 0.5 ⁇ a1/a2 ⁇ 2.
  • this application when this application regulates the mass content of the cross-linked resin and the mass content of the solvent within the above range, it can ensure that the solvent fully dissolves the cross-linked resin and porogen, ensuring that the three form a uniform mixed system; and during the solvent evaporation process Pore channels with suitable pore diameters can be formed, and the solid resin formed has good mechanical strength.
  • the mass content of the cross-linked resin added based on the total mass of the mixed system is recorded as a1; the mass content of the porogen added based on the total mass of the mixed system is recorded as a1 a3; the mixed system satisfies: 0.1 ⁇ a1/a3 ⁇ 5; optionally, 0.5 ⁇ a1/a3 ⁇ 3.
  • this application regulates the mass content of the cross-linked resin and the mass content of the porogen within the above range, which is beneficial to the porogen absorbing water and promoting the curing of the cross-linked resin; and can ensure that the pore diameter formed during the carbonization process is relatively small. of holes.
  • the preheating temperature is 60°C to 120°C, optionally 60°C to 80°C.
  • the preheating time t1 ⁇ 10h can be selected from 15h to 20h.
  • the cross-linked resin can be ensured to be fully cured; and the solvent evaporates relatively slowly, which is conducive to the formation of a pore structure with suitable pore size, and can ensure that the solid resin structural stability.
  • the carbonization process includes a first carbonization process and a second carbonization process, the temperature of the first carbonization process is 500°C to 800°C, and the time of the first carbonization process is 2h to 3h; And/or, the temperature of the second carbonization process is 800°C to 1000°C, and the time of the second carbonization process is 3h to 5h.
  • the first carbonization process can be carried out under constant temperature conditions.
  • the porogen may undergo a slow gasification process.
  • the porogen etches the internal structure of the resin, thereby A pore channel with a relatively small pore diameter is formed, and the overall pore channel structure is relatively uniform, thus forming a preliminary carbon skeleton structure.
  • the temperature of the second carbonization is relatively high, and the porogen can be quickly vaporized, which is conducive to the rapid completion of the pore-making process. And through multiple carbonization processes, the stability of the skeleton structure and appropriate porosity of the porous carbon matrix particles can be ensured.
  • the addition amount of the silicon precursor is greater than or equal to 40%; optionally, it is 40% to 60%.
  • the added amount of silicon precursor meets the above range, silicon-based nanoparticles can be evenly dispersed in the pores of the carbon matrix particles, thereby ensuring the capacity of the silicon-carbon composite material.
  • the deposition temperature of the chemical vapor deposition is less than or equal to 600°C; optionally, it is 450°C to 550°C.
  • the above deposition temperature can ensure that the silicon precursor effectively generates silicon nanoparticles and deposits them in the carbon matrix particles.
  • a third aspect of the present application provides a secondary battery.
  • the secondary battery includes a negative electrode sheet.
  • the negative electrode sheet includes the silicon-carbon composite material according to any embodiment of the above-mentioned first aspect or includes the silicon-carbon composite material according to the above-mentioned first aspect.
  • the silicon-carbon composite material obtained by the method of any embodiment described in the second aspect.
  • a fourth aspect of the present application provides an electrical device, which includes the secondary battery of the third aspect of the present application.
  • FIG. 1 is a schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 2 is an exploded schematic view of the embodiment of the secondary battery of FIG. 1 .
  • FIG. 3 is a schematic diagram of an embodiment of the battery module of the present application.
  • FIG. 4 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an embodiment of a power consumption device including the secondary battery of the present application as a power source.
  • Figure 7 is a cross-sectional phase diagram of the porous carbon matrix particles shown in Example 1 of the present application.
  • FIG. 8 is a partial enlarged view of the porous carbon matrix particles shown in FIG. 7 .
  • FIG. 9 is a cross-sectional phase diagram of the porous carbon matrix particles shown in Comparative Example 1.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) can be added to the method in any order.
  • the method may include steps (a), (b) and (c), and may also include step (a). , (c) and (b), and may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • Anode active materials have a significant impact on secondary battery performance.
  • Carbon and silicon, as common materials for anode active materials, have been extensively studied. The theoretical specific capacity of carbon particles is low, and the lithium insertion potential of carbon particles is low, which can easily cause lithium precipitation and cause safety issues.
  • Silicon can form a silicon-lithium alloy with lithium at room temperature, and its theoretical specific capacity is relatively high; and the lithium insertion potential of silicon is slightly higher than that of graphite, which can reduce the risk of lithium precipitation.
  • the volume change of micron-level silicon materials during the lithium deintercalation reaction may be greater than 300%, and the volume change is large.
  • the constantly changing volume of silicon particles can easily cause a Solid-Electrolyte Interphase (SEI) film on the surface of the active material.
  • SEI Solid-Electrolyte Interphase
  • the repeated growth of the SEI film will not only continuously consume lithium and electrolyte, but also limit the transmission of lithium ions, reduce the electrical contact of active materials, and increase impedance; and micron-level silicon materials will also have cracking and powdering phenomena.
  • the fresh silicon surface is constantly exposed, forming a new SEI film, increasing the thickness of the SEI film, causing the transmission path of lithium ions to be extended.
  • the inventor has improved the silicon-carbon composite material, forming silicon-based nanoparticles in the three-dimensional network cross-linked pore structure of the carbon matrix particles.
  • Two or more pores of the carbon matrix particles are staggered and connected to each other, which can It provides more space for silicon-based nanoparticles and is easy to store silicon in large quantities; and when carbon matrix particles and silicon-based nanoparticles are combined, the silicon-based nanoparticles are not prone to agglomeration and can be evenly dispersed in the pore structure; carbon matrix particles and silicon-based nanoparticles After the particles are compounded, the conductivity of the silicon-carbon composite material can be improved, while the volume effect of silicon in the process of deintercalating lithium can be alleviated, and it can fully withstand the stress changes of silicon-based nanoparticles, ensuring the structural stability of the silicon-carbon composite material and improving
  • the cycle stability and lithium storage capacity of silicon-carbon composite materials can improve the cycle performance and energy density of secondary batteries when silicon-carbon composite materials are used in secondary
  • the present application provides a silicon-carbon composite material.
  • the silicon-carbon composite material includes: carbon matrix particles, the carbon matrix particles include a three-dimensional network cross-linked pore structure; and silicon-based nanoparticles, at least part of which is provided in the three-dimensional network cross-linked pore structure.
  • the above-mentioned three-dimensional network cross-linked pore structure usually refers to a structure in which two or more pores are connected or staggered with each other and share the pore volume with each other in the pore structure formed by the carbon matrix particles.
  • the carbon matrix particles of the present application have a stable porous skeleton structure, strong supporting capacity, high stress capability, and excellent mechanical properties and electrical conductivity; the carbon matrix particles include a three-dimensional network cross-linked pore structure, which can There is more space for setting silicon-based nanoparticles, which can be used to store a large amount of silicon; when porous carbon matrix particles are combined with silicon-based nanoparticles, the silicon-based nanoparticles are not prone to agglomeration and can be evenly dispersed in the pores of the carbon matrix particles; After the carbon matrix particles and silicon-based nanoparticles are combined, the conductivity of the silicon-carbon composite material can be improved, while the volume effect of silicon in the process of deintercalation of lithium can be alleviated, and the stress changes of the silicon-based nanoparticles can be fully withstood, ensuring that the silicon-carbon
  • the structural stability of the composite material improves the cycle stability and lithium storage capacity of the silicon-carbon composite material, thereby improving the cycle performance and energy density of the secondary battery
  • the pore structure of silicon-carbon composite materials can be tested using equipment and methods known in the art. This can be done, for example, by using a scanning electron microscope (e.g. ZEISS Sigma 300). As an example, the following steps can be followed: first, cut the negative electrode sheet containing the silicon-carbon composite material into a sample to be tested of a certain size (for example, 6 mm ⁇ 6 mm), and use two electrically and thermally conductive sheets (such as copper foil) to Clamp the sample to be tested, stick and fix it with glue (such as double-sided tape) between the sample to be tested and the sheet, and press it with a flat iron block of a certain mass (such as about 400g) for a certain period of time (such as 1 hour) to make the sample to be tested and the sheet
  • glue such as double-sided tape
  • the sample stage into the sample rack and lock it, turn on the power of the argon ion cross-section polisher (for example, IB-19500CP) and evacuate (for example, 10Pa-4Pa), set the argon flow rate (for example, 0.15MPa) and voltage (for example, 8KV) ) and polishing time (for example, 2 hours), adjust the sample stage to rocking mode and start polishing.
  • the argon ion cross-section polisher for example, IB-19500CP
  • evacuate for example, 10Pa-4Pa
  • the argon flow rate for example, 0.15MPa
  • voltage for example, 8KV
  • polishing time for example, 2 hours
  • polishing use a scanning electron microscope (for example, ZEISS Sigma 300) to obtain the ion polished cross-sectional morphology (CP) picture of the sample to be tested.
  • CP ion polished cross-sectional morphology
  • the inventor of the present application has discovered through in-depth research that when the silicon-carbon composite material of the present application satisfies the above design and optionally meets one or more of the following parameters, the performance of the battery can be further improved.
  • At least a portion of the pores in the surface region of the carbon matrix particles have a pore size that is larger than the pore size in the interior region of the carbon matrix particles.
  • the surface region refers to a region extending from the surface of the carbon matrix particle to a depth of 500 nm to 800 nm into the particle; the internal region refers to the area in the carbon matrix particle other than the surface region.
  • the three-dimensional network cross-linked pore structure exhibits a layered distribution in the carbon matrix particles.
  • the powder compaction density of the silicon-carbon composite material when the silicon-carbon composite material is pressed for the first time under a force of 20,000N and held for 20 seconds is recorded as P 11 g/cm 3 ;
  • the silicon-carbon composite material The compacted density when the 20th press is carried out under the force of 20000N and the pressure is maintained for 20s is recorded as P 21 g/cm 3 .
  • the silicon carbon composite material satisfies: 1.00 ⁇ P 21 /P 11 ⁇ 1.20; optional Ground, 1.02 ⁇ P 21 /P 11 ⁇ 1.10.
  • P 21 /P 11 be recorded as M.
  • the size of M can be used to represent the change in stress and strain capacity during the compaction of silicon-carbon composite materials.
  • the silicon-carbon composite material has relatively strong pressure resistance, which can improve the pressure resistance of the silicon-carbon composite material when used as an anode active material, ensure the structural stability of the anode film layer, and further improve the battery. cycle performance.
  • P 21 /P 11 may be 1.00, 1.02, 1.10 or 1.20. When P 21 /P 11 is 1.00, it means that the silicon carbon composite material has good compression resistance and is not prone to compression deformation.
  • the powder compacted density of a material is a well-known meaning in the art and can be tested using methods known in the art.
  • an electronic pressure testing machine such as UTM7305
  • set different pressures in this application You can use 20000N or 50000N
  • maintain the pressure for 20s release the pressure
  • wait for 10s read the thickness H of the powder after compaction under the pressure on the equipment, and calculate the compaction density under the pressure.
  • the material is under this pressure.
  • the compacted density G/(H*S).
  • the silicon-carbon composite material of the present application has a specific structure, and controlling the powder compaction density of the silicon-carbon composite material under the above test conditions within a specific range can make the silicon-carbon composite material have a higher gram capacity while also It has good pressure resistance and effectively ensures the structural stability of the negative electrode film layer, so that secondary batteries containing this material can have better cycle performance while having higher energy density.
  • the total pore volume of the pores in the carbon matrix particles with a pore diameter greater than 100 nm is recorded as V 1 cm 3 /g, and the total pore volume of the pores in the carbon matrix particles with a pore diameter less than or equal to 100 nm is recorded as V 2 cm 3 /g; the carbon matrix particles satisfy: 1 ⁇ V 2 /V 1 ⁇ 30; optionally, 3 ⁇ V 2 /V 1 ⁇ 25.
  • V 2 /V 1 can be 1.5, 2.5, 2.8, 3.0, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 15, 20 or 25; or any two of the above values range of composition.
  • the pore size distribution of the carbon matrix particles can be ensured to be moderate, which is conducive to subsequent silicon-containing precursors entering the pores of the carbon matrix particles and reducing silicon deposition on the surface of the carbon matrix particles. risk; and it is conducive to the carbon matrix particles tending to be fully deposited, so that the specific surface area of the silicon-carbon composite particles formed after silicon is deposited is moderate and its reversible capacity can be guaranteed.
  • the above total pore volume can be measured using instruments and methods known in the art.
  • the test method can refer to GB/T 19587-2004, using the mesopore pore size distribution test BJH (Barret joyner Halenda), and using gas under the micro-mesoporous model.
  • BJH Barret joyner Halenda
  • the adsorption-desorption method is tested and the adsorption branch data is selected, and the total pore volume V 1 of pores with a pore diameter greater than 100 nm and the total pore volume V 2 of pores with a pore diameter less than or equal to 100 nm are measured and counted.
  • the total pore volume of the pores in the carbon matrix particles with a pore diameter greater than 100 nm is recorded as V 1 cm 3 /g, then V 1 ⁇ 0.01, optionally, 0.01 ⁇ V 1 ⁇ 0.5.
  • the total pore volume of the pores in the carbon matrix particles with a pore diameter of 100 nm or less is recorded as V 2 cm 3 /g, then V 2 ⁇ 0.05, optionally ,0.05 ⁇ V 2 ⁇ 1.1.
  • the porosity of the carbon matrix particles is denoted as W, 40% ⁇ W ⁇ 80%; optionally, 50% ⁇ W ⁇ 70%.
  • the pores occupy an appropriate volume of the skeleton, which can not only ensure the stability of the skeleton structure, but also meet the capacity of deposited silicon.
  • Silicon-based nanoparticles are attached to the pores, and silicon-based nanoparticles and porous Carbon matrix particles can work synergistically to increase the capacity and conductivity of silicon-carbon composites.
  • the porosity W% of the porous carbon matrix particles can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50 %, 55%, 60%, 65%, 70%, 75% or 80%; or a range consisting of any two of the above values.
  • the powder compaction density of the carbon matrix particles under a force of 50,000N is recorded as P g/cm 3 , 0.4 ⁇ P ⁇ 1.1; optionally, 0.6 ⁇ P ⁇ 0.9.
  • P can be tested according to the powder compaction density testing method of the materials provided above.
  • the negative electrode film layer can have a higher compaction density, thereby ensuring that the secondary battery has a higher energy density.
  • the negative electrode film layer can also have a strong ability to maintain the pore structure during the cycle, thereby making the electrolyte wettability of the negative electrode sheet better. Good, it can better improve the cycle performance of secondary batteries.
  • the powder compaction density P g/cm 3 of the carbon matrix particles under a force of 50000N can be 0.6g/cm 3 , 0.65g/cm 3 , 0.7g/cm 3 , 0.75g/cm 3 , 0.8 g/cm 3 , 0.85g/cm 3 , 0.9g/cm 3 , 1.0g/cm 3 or 1.1g/cm 3 ; or a range consisting of any two of the above values.
  • the true density of the carbon matrix particles is recorded as ⁇ g/cm 3 , 1.7 ⁇ 2.5; optionally, 1.9 ⁇ 2.3.
  • the negative electrode film layer can have a relatively high specific capacity, thereby improving the energy density of the secondary battery.
  • the true density ⁇ g/cm 3 of the carbon matrix particles may be 1.7g/cm 3 , 1.8g/ cm 3 , 1.9g/cm 3 , 2.0g/cm 3 , 2.1g/cm 3 , 2.2g/cm 3 , 2.3g/cm 3 , 2.4g/cm 3 or 2.5g/cm 3 ; or a range consisting of any two of the above values.
  • the true density of a material is a well-known meaning in the art, which refers to the actual mass of solid matter per unit volume of the material in an absolutely dense state, that is, the density after removing the internal voids of the material or the voids between particles; Testing can be performed using instruments and methods known in the art.
  • the test method can refer to GB/T24586-2009, and the test instrument can use a true density tester.
  • the carbon matrix particles include one or more of graphite, soft carbon, and hard carbon.
  • the silicon-based nanoparticles When the above materials are prepared into a porous structure, it is beneficial for the silicon-based nanoparticles to be placed in the pores of the porous structure; and its structural stability is relatively high.
  • the silicon-based nanoparticles include one or more of silicon oxide compounds, pre-lithium silicon oxide compounds, amorphous silicon, crystalline silicon and silicon-carbon composites; optionally, the silicon-based nanoparticles Nanoparticles include amorphous silicon.
  • Amorphous silicon can expand uniformly in all directions, thereby uniformly squeezing the porous carbon matrix particles.
  • the porous carbon matrix particles can effectively alleviate the volume expansion of amorphous silicon.
  • the structure of crystalline silicon is relatively more stable and is more conducive to giving full play to its capacity characteristics.
  • the silicon-carbon composite is formed in the pores of the porous carbon matrix particles after combining carbon and silicon into compounds in advance.
  • the volume expansion of the silicon-carbon composite is relatively small, which can reduce the stress on the porous carbon matrix particles.
  • the silicon-carbon composite may be silicon carbide.
  • the crystal structure of the negative active material can be tested using equipment and methods known in the art. As an example, you can follow the following steps: select a microgrid of a certain diameter (such as 3mm in diameter), use pointed tweezers to clamp the edge of the microgrid, and place the film side upward (observe the shiny side under light, That is, the membrane surface), gently place it flat on the white filter paper; take an appropriate amount of silicon particle sample (such as 1g) and add it to a beaker containing an appropriate amount of ethanol, and perform ultrasonic oscillation for 10min to 30min; use a glass capillary to absorb it, and then drop 2-3 drops
  • the sample to be tested is placed on the microgrid; after baking in the oven for 5 minutes, the microgrid with the sample to be tested is placed on the sample stage, and a transmission electron microscope (such as Hitachi HF-3300S Cs-corrected STEM) is used at a certain magnification By testing at a magnification (for example, 60,000 times), a transmission
  • the mass ratio of the silicon-based nanoparticles in the silicon-carbon composite material is greater than or equal to 40%; optionally, it is 40%-60%.
  • the mass ratio of silicon-based nanoparticles in the silicon-carbon composite material is within the above range, the capacity of the silicon-carbon composite material is relatively high.
  • the quality of silicon-based nanoparticles in the silicon-carbon composite material can be tested using methods and equipment known in the art.
  • the quality can be measured with reference to the EPA 6010D-2014 standard; specifically, ICP-OES (Elemental Analysis-Inductance) can be used.
  • Coupled plasma emission spectrometry) test first dissolve the solid to be measured into a liquid with strong acid, and then introduce the liquid into the ICP light source through atomization. After further ionization and excitation of the gaseous atoms to be measured in a strong magnetic field, the excited state Return to the ground state; energy is released during the above process and is recorded as different characteristic spectral lines for quantitative analysis of trace elements.
  • the quality of the carbon element in the silicon-carbon composite material can be tested using methods and equipment known in the art.
  • the TG (thermal weight loss) test can be used, and the silicon-carbon composite material is used as a sample and heat treated under oxygen-containing conditions (25 °C to 1000 °C), record the mass of the sample before and after heat treatment.
  • the difference in mass of the sample before and after is the mass of carbon ablated, from which the carbon content in the sample can be known.
  • the particle size of the silicon-based nanoparticles is recorded as D si nm, and D si ⁇ 100; optionally, 2 ⁇ D si ⁇ 80.
  • the particle size of silicon-based nanoparticles is relatively small, which can significantly alleviate the high pressure caused by silicon volume changes, help ensure the overall structural stability of silicon-carbon composite materials, and improve the cycle stability of secondary batteries; and can significantly shorten the life of lithium-ion batteries.
  • the transmission distance of ions is beneficial to improving the dynamic properties of silicon-carbon composite materials.
  • 10 ⁇ Dsi ⁇ 80 for example, the particle size of the silicon-based nanoparticles can be 2nm, 3nm, 5nm, 8nm, 10nm, 12nm, 15nm, 20nm, 25nm, 30nm, 40nm, 50nm, 60nm, 70nm or 80nm; or a range consisting of any two of the above values.
  • the particle size of silicon-based nanoparticles can be measured according to the XRD pattern of the sample according to the JIS/K0131-1996 test standard. According to the XRD pattern of the sample, the half-peak width ⁇ and diffraction angle of the Si (111) crystal plane diffraction peak are taken. ⁇ , substitute it into the Debye-Scherrer formula to calculate, and get the particle size of silicon nanoparticles.
  • the volume distribution particle diameter Dv10 of the silicon-carbon composite material satisfies: Dv10 ⁇ 5 ⁇ m; optionally, 3 ⁇ m ⁇ Dv10 ⁇ 5 ⁇ m; exemplarily, Dv10 can be 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m or 5 ⁇ m; or It is a range consisting of any two values mentioned above.
  • the volume distribution particle size Dv50 of the silicon-carbon composite material satisfies: Dv50 ⁇ 10 ⁇ m; optionally, 5 ⁇ m Dv50 ⁇ 8 ⁇ m; exemplarily, Dv50 can be 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m or 10 ⁇ m; or a range consisting of any two of the above values.
  • the volume distribution particle size Dv50 of the silicon-carbon composite material meets the above range, the structure of the silicon-carbon composite material is relatively stable and the dynamic properties are relatively good, which is beneficial to improving the first Coulombic efficiency of the silicon-carbon composite material.
  • the volume distribution particle size Dv90 of the silicon-carbon composite material satisfies: Dv90 ⁇ 20 ⁇ m; optionally, 8 ⁇ m Dv90 ⁇ 18 ⁇ m; exemplarily, Dv90 can be 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m or 18 ⁇ m; or a range consisting of any two of the above values.
  • the particle size distribution of the silicon-carbon composite material satisfies: (Dv90-Dv10)/Dv50 ⁇ 1.6.
  • (Dv90-Dv10)/Dv50 may be 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1, or 0.75.
  • the particle size distribution of the silicon-carbon composite material meets the above range, the overall average particle size of the silicon-carbon composite material is relatively moderate, and the particle size distribution is relatively average, which is beneficial to improving the uniformity of the overall performance of the silicon-carbon composite material.
  • the Dv10, Dv50 and Dv90 of a material are all meanings known in the art and can be tested using methods known in the art. For example, you can refer to the standard GB/T 19077.1-2016 and use a laser particle size analyzer (such as Malvern Master Size 3000) to measure.
  • a laser particle size analyzer such as Malvern Master Size 3000
  • Dv10, Dv50 and Dv90 are as follows:
  • Dv10 The particle size corresponding to when the cumulative volume distribution percentage of the material reaches 10%
  • Dv50 The particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%
  • Dv90 The particle size corresponding to when the cumulative volume distribution percentage of the material reaches 90%.
  • the specific surface area SSA of the silicon-carbon composite material satisfies: 2m 2 /g ⁇ SSA ⁇ 10 m 2 /g.
  • the specific surface area SSA of the silicon-carbon composite material meets the above range, the range of the specific surface area is relatively moderate, and the dynamic properties of the material are better, which is beneficial to the first Coulombic efficiency of the material.
  • the specific surface area SSA of the silicon-carbon composite material can be 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; or a range consisting of any two of the above values.
  • specific surface area SSA has a well-known meaning in the art.
  • the surface area is usually expressed in units of m 2 /g and can be tested using methods and instruments known in the art.
  • the nitrogen adsorption specific surface area analysis test can be done by Micromeritics of the United States. Tri-Star3020 specific surface area pore size analysis tester was used.
  • this application also provides a method for preparing silicon-carbon composite materials.
  • the methods include:
  • S500 generate silicon-based nanoparticles from a gas containing a silicon precursor through chemical vapor deposition, so that at least a part of the silicon-based nanoparticles are attached to the pores of the carbon matrix particles.
  • carbon matrix particles are prepared by cross-linking resin.
  • the carbon matrix particles have a pore structure with a three-dimensional network cross-linked structure.
  • the pore structure contains two or more interlaced pores, and the pores can be connected to each other; here And exclude the parallel arrangement between some holes.
  • Carbon matrix particles with a three-dimensional network cross-linked structure have good mechanical strength, strong support ability, high stress capability, and excellent mechanical properties and electrical conductivity.
  • the silicon precursor is deposited on the carbon matrix particles with a three-dimensional network cross-linked structure through chemical vapor deposition to form silicon-based nanoparticles, so that the carbon matrix particles and silicon-based nanoparticles are combined into a silicon-carbon composite material, and the carbon element and the silicon element can Functioning synergistically, on the basis of improving the conductivity and capacity of silicon-carbon composite materials, carbon matrix particles can alleviate the volume expansion of silicon-based nanoparticles during the process of deintercalating lithium to a certain extent, thereby improving the performance of silicon-carbon composite materials. Cycle stability and lithium storage capacity, thus improving the cycle performance and energy density of secondary batteries when silicon-carbon composite materials are used in secondary batteries.
  • the carbon matrix particles have a surface area and an inner area located within the surface area, and the pore size of at least a part of the pores in the surface area of the carbon matrix particles is larger than the pores in the inner area of the carbon matrix particles. size. Carbon and silicon can better synergize and improve the performance of secondary batteries.
  • step S100 the cross-linked resin, porogen and solvent are mixed into a mixed system.
  • the cross-linked resin may include one or more of novolac resin, soluble phenolic resin, epoxy resin, polyurethane, furan resin, and urea-formaldehyde resin; the above-mentioned cross-linked resin itself has a certain degree of cross-linking, Its structural stability is relatively good.
  • the solvent may include liquid alcohols, ethers, ketones, etc.
  • the liquid alcohols include methanol, ethanol, ethylene glycol, polyethylene glycol (low molecular weight), glycerin, and isopropyl alcohol. of one or more.
  • Liquid alcohol can dissolve cross-linked resin and porogen, mixing the three into a more uniform system. During the process of preheating the mixed system, a large amount of solvent evaporates. During the process of solvent evaporation, the cross-linked resin gradually solidifies, and a larger pore structure will be formed inside, initially forming a porous skeleton structure.
  • Ethers may include butyl ether, dimethyl ether, etc.
  • Ketones may include acetone and the like.
  • the mass content of the cross-linked resin is a1; based on the total mass of the mixed system, the mass content of the solvent is a2, and the mixed system satisfies: 0.1 ⁇ a1/a2 ⁇ 10.
  • a1/a2 can be 0.1, 0.2, 0.5, 0.8, 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 9 or 10 ; Or a range consisting of any two of the above values.
  • the porogen includes one or more of chloride, carbonate, and acetate.
  • the chloride salt may include one or more of sodium chloride, potassium chloride, and zinc chloride;
  • the carbonate may include one or more of sodium carbonate, amine carbonate, and potassium carbonate;
  • the acid salt may include one or more of zinc acetate, ammonium acetate, and sodium acetate.
  • the above-mentioned porogen can etch the structure of the granular resin to form pore channels with smaller pore diameters, which can connect the pore channels formed by solvent volatilization, thereby being more conducive to the formation of the specific pore structure of the present application; and Porogens can continue to expand the pore channels formed by solvent evaporation, thereby ensuring that the pore size of the porous structure is within an appropriate range.
  • the mass content of the cross-linked resin is a1; based on the total mass of the mixed system, the mass content of the porogen is a3, and the mixed system satisfies: 0.1 ⁇ a1/a3 ⁇ 5.
  • a1/a3 can be 0.1, 0.2, 0.3, 0.5, 0.6, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4 or 5; or It is a range consisting of any two values mentioned above.
  • step S100 the mixture is mixed under stirring to form a mixed system; the stirring speed is 100 r/min to 1500 r/min.
  • the stirring speed is 500r/min ⁇ 1000r/min.
  • the stirring speed can be 100r/min, 120r/min, 150r/min, 180r/min, 200r/min, 250r/min, 300r/min, 350r/min, 400r/min, 450r/min, 500r/ min, 550r/min, 600r/min, 650r/min, 700r/min, 750r/min, 800r/min, 900r/min, 1000r/min, 1100r/min, 1200r/min, 1300r/min, 1400r/min or 1500r/min; or the range consisting of any two of the above values.
  • step S200 the mixed system is heat treated, and the molecules in the cross-linked resin are continuously cross-linked to form macromolecules, and dehydration occurs during the cross-linking process.
  • the released water easily reacts with the porogen, that is, the porogen can absorb water. This further promotes the occurrence of the cross-linking process and increases the degree of cross-linking.
  • the preheating temperature is 60°C to 120°C, optionally 60°C to 80°C.
  • the preheating temperature When the preheating temperature is controlled within the above range, the cross-linked resin can be ensured to be fully cured; and the solvent evaporates relatively slowly, which is more conducive to the formation of the specific pore structure of this application, and can ensure the structural stability of the solid resin, thereby improving the Compressive properties of silicon-carbon composites subsequently formed from solid resin.
  • the preheating temperature may be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C; or It is a range consisting of any two values mentioned above.
  • step S300 the solid resin is crushed to form granular resin; in some embodiments, the solid resin can be reheated, and the reheating temperature is 100°C to 200°C.
  • the reheating process can promote further evaporation of the solvent and continue the formation of pore channels; it can also promote further dehydration and cross-linking of the resin, improve the mechanical strength of the granular resin, and improve the structural stability of the granular resin.
  • multiple crushing processes can be used, such as coarse crushing, fine crushing, etc., in order to obtain granular resin that meets the preset particle size as a carbon precursor.
  • the preset particle size range can be micron level.
  • the granular resin after crushing, can also be subjected to operations such as impurity removal, demagnetization, and particle size classification to ensure that the obtained granular resin meets process requirements.
  • Impurity removal, demagnetization and particle size classification can all be performed using techniques known in the art, which are not limited here.
  • step S400 the particulate resin is carbonized to form porous carbon matrix particles.
  • the carbonization temperature may range from 500°C to 1200°C.
  • the granular resin When the carbonization temperature is in the above range, the granular resin can be fully carbonized and a three-dimensional cross-linked pore structure can be formed inside the carbon matrix particles to facilitate the deposition of silicon-based nanoparticles, and the skeleton structure of the formed carbon matrix particles is It has high structural stability and good compression resistance.
  • the carbonization process may include a first carbonization process and a second carbonization process, wherein the temperature of the first carbonization process is 500°C to 800°C, and the time of the first carbonization process is 2h to 3h; The temperature may be 800°C to 1000°C, and the time of the second carbonization process is 3h to 5h; the temperature of the first carbonization process is lower than the temperature of the second carbonization process.
  • the heating rate of the first carbonization process is relatively low, for example, at a rate of 1 to 2°C/min, and after the first carbonization process is heated to a predetermined temperature, the constant temperature treatment can be maintained for a certain period of time, such as constant temperature treatment for 1 hour. During this process, The porogen may undergo a slow gasification process.
  • the porogen etches the internal structure of the resin to form pore channels with relatively small pore diameters.
  • the overall pore structure is relatively uniform, thus forming a preliminary carbon skeleton structure.
  • the temperature of the second carbonization is relatively high, which can quickly vaporize the porogen.
  • the porogen creates pores in the carbon matrix in the form of gas and opens up the gaps between the pores to form a three-dimensional cross-linked pore structure.
  • the continuous escape has a negative impact on the carbon.
  • the peripheral part of the matrix is gradually etched to expand the holes, so that the three-dimensional network cross-linked pore structure can be distributed in a layered manner in the carbon matrix particles. And through multiple carbonization processes, the stability of the skeleton structure and appropriate porosity of the porous carbon matrix particles can be ensured.
  • porous carbon matrix particles can be further screened to obtain particles that meet the particle size requirements.
  • the screening method can be carried out by means known in the art, and is not limited here.
  • step S500 at least part of the silicon-based nanoparticles are attached to the pores of the carbon matrix particles.
  • the addition amount of the silicon precursor is greater than or equal to 40%; optionally, it is 40% to 60%.
  • silicon-based nanoparticles can be evenly dispersed in the pores of the carbon matrix particles, thereby ensuring the capacity of the silicon-carbon composite material.
  • the silicon precursor may include one or more of silicon oxide, prelithium silicon oxy, crystalline silicon, amorphous silicon, and silicon carbon composite.
  • the above-mentioned silicon precursor can form nano-scale silicon-based particles in the pores of the carbon matrix particles, which is beneficial to even dispersion in the pore channels.
  • the silicon-carbon composite may be silicon carbide.
  • the deposition temperature of the chemical vapor deposition is less than or equal to 600°C; optionally, it is 450°C to 550°C.
  • the above deposition temperature can ensure that the silicon precursor effectively generates silicon nanoparticles and deposits them in the carbon matrix particles.
  • the carbon matrix particles can be placed in a heating chamber of a vapor deposition furnace in advance, and a vacuum pump is used to evacuate the heating chamber.
  • a vacuum pump is used to evacuate the heating chamber.
  • Pour protective gas into the heating chamber After the protective gas fills the heating chamber, pass the gas containing the silicon precursor into the heating chamber and maintain the heating chamber at a certain pressure.
  • an inert gas can be used as a protective gas, and the protective gas and the gas containing the silicon precursor are jointly input onto the porous carbon matrix particles.
  • the inert gas may include one or more of nitrogen, argon, and helium.
  • the cross-linked resin, porogen and solvent are blended in situ into a uniform system.
  • the solvent and porogen jointly create pores, and the solvent and porogen can escape from the inside of the cross-linked resin.
  • the cross-linked resin is eventually converted into carbon material to form a porous carbon skeleton structure with cross-linked pores.
  • This porous carbon skeleton has a balanced stress structure and exhibits good stress capability. When used as an anode active material in secondary batteries, it can Improving the structural stability of the negative active material can improve the cycle performance of secondary batteries.
  • this application also provides a secondary battery.
  • a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode film layer includes a negative electrode active material.
  • the negative active material may include the silicon-carbon composite material of any embodiment of the first aspect of the application or the silicon-carbon composite material prepared by the method of any embodiment of the second aspect of the application.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, other silicon-based materials, tin-based materials, lithium titanate, and the like.
  • Other silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode film layer optionally further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • a solvent such as deionized water
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the cathode active material may be a cathode active material known in the art for batteries.
  • the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (can also be abbreviated to NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (can also be abbreviated to NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (can also be abbreviated to NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as Li Li
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon. At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • composites of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate and carbon.
  • At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode sheet can be prepared by dispersing the components of the positive electrode sheet, such as the positive active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone ), the positive electrode slurry is formed; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N-methylpyrrolidone
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is an electrolyte solution.
  • the electrolyte solution includes electrolyte salts and solvents.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.
  • the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte optionally further includes additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. As shown in FIG. 1 , a square-structured secondary battery 5 is shown as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 is used to cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and can be adjusted according to needs.
  • the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte may be assembled to form a secondary battery.
  • the positive electrode sheet, isolation film, and negative electrode sheet can be formed into an electrode assembly through a winding process or a lamination process.
  • the electrode assembly is placed in an outer package, dried, and then injected with electrolyte. After vacuum packaging, standing, and Through processes such as formation and shaping, secondary batteries are obtained.
  • the secondary batteries according to the present application can be assembled into a battery module.
  • the number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 3 is a schematic diagram of the battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 arranged in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 is used to cover the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application provides an electrical device.
  • the electrical device includes at least one of a secondary battery, a battery module and a battery pack of the present application.
  • Secondary batteries, battery modules and battery packs can be used as power sources for power-consuming devices, and can also be used as energy storage units for power-consuming devices.
  • Electric devices can be, but are not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf balls). vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the electrical device can select secondary batteries, battery modules or battery packs according to its usage requirements.
  • FIG. 6 is a schematic diagram of an electrical device as an example.
  • the electric device 6 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like.
  • a battery pack 1 or a battery module can be used.
  • the power-consuming device may be a mobile phone, a tablet computer, a laptop computer, etc.
  • the electrical device is usually required to be light and thin, and secondary batteries can be used as power sources.
  • a two-step carbonization treatment on the powder, as follows: pre-carbonize by raising the temperature to 500°C for 1 hour, continue to heat to 1000°C for carbonization for 2 hours, and perform impurity removal and screening to obtain a porous carbon matrix, where , the porous carbon matrix has a three-dimensional network pore structure, and the pore size of at least some of the pores in the surface area of the carbon matrix particles is larger than the pore size in the internal area of the carbon matrix particles.
  • the carbonization treatment adopts segmented carbonization, that is, the first carbonization process and the second carbonization process. The temperature of the first carbonization process is lower than the temperature of the second carbonization process.
  • Figures 7 and 8 show cross-sectional views of the porous carbon matrix, which has a pore structure showing a three-dimensional network cross-linking, and Figure 8 can also be seen that the three-dimensional network cross-linking pore structure presents a layered distribution in the carbon matrix particles. .
  • the positive electrode sheet Preparation of the positive electrode sheet: Mix the positive active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM 811 ), the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black in a mass ratio of 97%:1.5%:1.5 % is dissolved in the solvent N-methylpyrrolidone (NMP), stir thoroughly and mix evenly to prepare a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and then dried, cold pressed, and cut. Get the positive electrode piece.
  • NMP N-methylpyrrolidone
  • the secondary battery preparation process of Comparative Example 1 is basically the same as that of Example 1. The difference is that Comparative Example 1 uses different silicon-carbon composite materials.
  • the preparation method of the silicon-carbon composite material of Comparative Example 1 is as follows:
  • Figure 9 shows the cross-sectional morphology of the porous carbon matrix particles of Comparative Example 1, and it can be seen that the pore structure is honeycomb-shaped.
  • Examples 2-6 adopt a method similar to Example 1 to prepare secondary batteries. The difference from Example 1 is that
  • the secondary batteries prepared in each Example and Comparative Example were charged at 25°C with a constant current at a rate of 0.5C to a charge cut-off voltage of 4.25V, and then charged at a constant voltage to a current ⁇ 0.05C, left to stand for 5 minutes, and then charged at a rate of 0.33C Discharge at a constant current rate to the discharge cut-off voltage of 2V, and let it sit for 5 minutes. This is a charge-discharge cycle.
  • the test method for the gram capacity of the negative active material is as follows: Take the negative electrode piece prepared in each of the above examples and comparative examples, punch it into a 1.8cm 2 ⁇ 1.8cm 2 small disc sample, weigh the small disc sample and record it as M1, weigh the weight of the current collector in the small disc sample and record it as M2; use the metal lithium sheet as the counter electrode, use polyethylene (PE) film as the isolation film, and mix ethylene carbonate (EC) and ethyl methyl carbonate.
  • PE polyethylene
  • EC ethylene carbonate
  • EMC electrolyte
  • DEC diethyl carbonate
  • EMC diethyl carbonate
  • EMC diethyl carbonate
  • Gram capacity of negative active material C/(M1-M2).
  • Example 1 prepares carbon matrix particles with a three-dimensional network cross-linked pore structure, which can provide more space for silicon and can be used to store a large amount of silicon, thereby improving the gram capacity of the silicon-carbon composite material;
  • silicon can be evenly dispersed in the pores and is not easy to agglomerate. It can alleviate the volume effect of silicon in the process of deintercalating lithium, and can fully withstand the stress changes generated by silicon, thereby ensuring that silicon carbon Structural stability of composite materials, thereby improving the cycle stability of silicon-carbon composite materials.
  • the pore structure of the carbon matrix particles in Comparative Example 1 is a honeycomb pore structure. This structure is not conducive to providing sufficient space for the deposition of silicon, resulting in a relatively low deposition amount of silicon.
  • the gram capacity of the composite material of silicon and carbon is relatively low. is smaller; and the overall structural stability of the composite material of silicon and carbon is poor, resulting in a relatively low cycle life when used in secondary batteries.

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Abstract

本申请提供了一种硅碳复合材料、其制备方法及包含该硅碳复合材料的二次电池；所述硅碳复合材料包括多孔碳基体颗粒和硅基纳米颗粒；所述碳基体颗粒包括三维网络交联的孔结构；以及硅基纳米颗粒的至少一部分设置于所述三维网络交联的孔结构中。本申请能够兼顾改善二次电池的循环性能和能量密度。

Description

硅碳复合材料、其制备方法及包含该硅碳复合材料的二次电池 技术领域
本申请涉及电池领域，具体涉及一种硅碳复合材料、其制备方法及包含该硅碳复合材料的二次电池。
背景技术
二次电池具有容量高、寿命长等特性，因此广泛应用于电子设备，例如手机、笔记本电脑、电瓶车、电动汽车、电动飞机、电动轮船、电动玩具汽车、电动玩具轮船、电动玩具飞机和电动工具等等。由于二次电池取得了极大的进展，因此对二次电池的性能提出了更高的要求。为了提高二次电池的能量密度，行业内目前考虑采用硅基负极活性材料，但是硅基材料虽然克容量较高，但是其自身的膨胀较大，严重影响电池的循环性能。
因此，如何使电池在具有较高能量密度的前提下同时兼顾较好的循环性能，仍是本领域亟待解决的问题。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种硅碳复合材料、其制备方法及包含该硅碳复合材料的二次电池，使得该二次电池可以在较高能量密度的前提下同时兼顾较好的循环性能。
本申请的第一方面提供了一种硅碳复合材料，所述硅碳复合材料包括碳基体颗粒，所述碳基体颗粒包括三维网络交联的孔结构；以及硅基纳米颗粒，其至少一部分设置于所述三维网络交联的孔结构中。
本申请的碳基体颗粒具有稳定的多孔骨架结构，其支撑能力较强，表现为应力能力较高，且具有优异的机械性能和导电性；其碳基体颗粒包括三维网络交联的孔结构，可供设置硅基纳米颗粒的空间较多，可以用于大量储硅；在多孔碳基体颗粒与硅基纳米颗粒复合时，硅基纳米颗粒不易发生团聚，能够均匀分散于碳基体颗粒的孔中；在碳基体颗粒与硅基纳米颗粒复合后，可以提高硅碳复合材料的导电性，同时缓解硅在脱嵌锂过程中的体积效应，且能够充分承受硅基纳米颗粒的应力变化，保证硅碳复合材料的结构稳定性，提高硅碳复合材料的循环稳定性和储锂能力，由此在硅碳复合材料应用于二次电池时，提高二次电池的循环性能和能量密度。
在任意实施方式中，所述碳基体颗粒的表层区域中至少一部分孔的孔尺寸大于 所述碳基体颗粒的内部区域的孔尺寸。
在任意实施方式中，所述三维网络交联的孔结构在所述碳基体颗粒中呈现层状分布。
在任意实施方式中，所述硅碳复合材料在20000N作用力下经过1次粉压后测试的粉体压实密度记为P 11g/cm 3，所述硅碳复合材料在20000N作用力下经过20次粉压后测试的压实密度记为P 21g/cm 3，则所述硅碳复合材料满足：1.00＜P 21/P 11≤1.20；可选地，1.02≤P 21/P 11≤1.10。
本申请的硅碳复合材料具有特定的结构，且在上述测试条件下的粉体压实密度符合特定的要求，使得硅碳复合材料在具有较高克容量的同时还具有较好的抗压性，有效保证了负极膜层的结构稳定性，从而使得含有该材料的二次电池在具有较高能量密度的前提下同时兼顾较好的循环性能。
在任意实施方式中，所述硅碳复合材料在20000N作用力下的粉体压实密度记为P 11g/cm 3，则所述硅碳复合材料满足：1.10≤P 11≤1.40；可选地，1.12≤P 11≤1.35。
在任意实施方式中，在采用气体吸脱附方法测试时，所述碳基体颗粒中孔径大于100nm的孔的总孔容积记为V 1cm 3/g，所述碳基体颗粒中孔径小于等于100nm的孔的总孔容积记为V 2cm 3/g，则所述碳基体颗粒满足：1＜V 2/V 1≤30；可选地，3≤V 2/V 1≤25。
本申请通过调控多孔碳基体颗粒中特定尺寸的孔的总孔容积比例，能够保证碳基体颗粒的孔径分布适中，有利于后续含硅前驱体进入碳基体颗粒的孔中，降低硅沉积于碳基体颗粒表面的风险；且有利于碳基体颗粒趋近于沉积饱满，从而使得沉积硅后所形成的硅碳复合颗粒的比表面积适中，能够保证其可逆容量。
在任意实施方式中，在采用气体吸脱附方法测试时，所述碳基体颗粒中孔径大于100nm的孔的总孔容积记为V 1cm 3/g，则V 1≥0.01，可选地，0.01≤V 1≤0.5。
在任意实施方式中，在采用气体吸脱附方法测试时，所述碳基体颗粒中孔径小于等于100nm的孔的总孔容积记为V 2cm 3/g，则V 2≥0.05，可选地，0.05≤V 2≤1.1。
在任意实施方式中，所述碳基体颗粒的孔隙率记为W，40％≤W≤80％；可选地，50％≤W≤70％。
本申请中碳基体颗粒的孔隙率满足上述范围时，孔占据骨架的体积适当，既能够保证骨架结构的稳定性，又能够满足沉积硅的容量，硅基纳米颗粒附着于孔中，硅基纳米颗粒和多孔碳基体颗粒可以协同发挥作用，从而提高硅碳复合材料的容量和导电性。
在任意实施方式中，所述碳基体颗粒在50000N作用力下的粉体压实密度记为P g/cm 3，0.4≤P≤1.1；可选地，0.6≤P≤0.9。
本申请通过调节碳基体颗粒的粉体压实密度在合适的范围内，能使负极膜层具有较高的压实密度，进而保证二次电池具有较高的能量密度。
在任意实施方式中，所述碳基体颗粒的真密度记为ρg/cm 3，1.7≤ρ≤2.5；可选地，1.9≤ρ≤2.2。
本申请通过调节碳基体颗粒的真密度在合适的范围内，能够使得负极膜层具有相对较高的比容量，从而能够提高二次电池的能量密度。
在任意实施方式中，所述碳基体颗粒包括石墨、软碳和硬碳中的一种或几种。
在任意实施方式中，所述硅基纳米颗粒包括硅氧化合物、预锂硅氧化合物、非晶硅、晶体硅和硅碳复合物中的一种或几种；可选地，所述硅基纳米颗粒包括非晶硅。
在任意实施方式中，所述硅基纳米颗粒在所述硅碳复合材料中的质量比大于等于40％；可选为40％-60％。
本申请中硅基纳米颗粒在硅碳复合材料中的质量比在上述范围时，硅碳复合材料的容量相对较高。
在任意实施方式中，所述硅碳复合材料的体积分布粒径Dv10满足：Dv10≤5μm；可选地，3μm≤Dv10≤5μm。
在任意实施方式中，所述硅碳复合材料的体积分布粒径Dv50满足：Dv50≤10μm；可选地，5μm Dv50≤8μm。
在任意实施方式中，所述硅碳复合材料的体积分布粒径Dv90满足：Dv90≤20μm；可选地，8μm≤Dv90≤18μm。
在任意实施方式中，所述硅碳复合材料的粒度分布满足：(Dv90-Dv10)/Dv50≤1.6；可选地，1.4≤(Dv90-Dv10)/Dv50≤1.6。
本申请的硅碳复合材料的粒度满足上述范围时，硅碳复合材料的结构相对稳定，动力学性能相对较好，有利于提高硅碳复合材料的首次库伦效率。
在任意实施方式中，所述硅碳复合材料的比表面积SSA满足：2m 2/g≤SSA≤10m 2/g；可选地，3m 2/g≤SSA≤7m 2/g。
本申请的硅碳复合材料的比表面积SSA满足上述范围时，比表面积的范围较为适中，材料的动力学性能较好，有利于材料的首次库伦效率。
本申请的第二方面提供一种硅碳复合材料的制备方法，包括如下步骤：将交联树脂、致孔剂和溶剂混合形成混合体系。预加热所述混合体系，以使所述溶剂挥发并使得所述交联树脂固化形成固态树脂。破碎所述固态树脂形成颗粒状树脂。碳化所述颗粒状树脂，以使所述致孔剂挥发并刻蚀所述颗粒状树脂形成具有三维网状交联结构的碳基体颗粒。通过化学气相沉积，由包含硅前驱体的气体生成硅基纳米颗粒，所述硅基纳米颗粒中的至少一部分附着于所述碳基体颗粒的孔中。
在任意实施方式中，基于所述混合体系的总质量计，加入所述交联树脂的质量含量记为a1；基于所述混合体系的总质量计，加入所述溶剂的质量含量为记a2；所述混合体系满足：0.1≤a1/a2≤10；可选地，0.5≤a1/a2≤2。
由此，本申请调控交联树脂的质量含量与溶剂的质量含量在上述范围时，可以保证溶剂充分溶解交联树脂和致孔剂，保证三者形成均一的混合体系；且在溶剂蒸发过程中能够形成孔径合适的孔道，且所形成的固态树脂具有良好的机械强度。
在任意实施方式中，基于所述混合体系的总质量计，加入所述交联树脂的质量 含量记为a1；基于所述混合体系的总质量计，加入所述致孔剂的质量含量记为a3；所述混合体系满足：0.1≤a1/a3≤5；可选地，0.5≤a1/a3≤3。
由此，本申请调控交联树脂的质量含量与致孔剂的质量含量在上述范围时，有利于致孔剂吸水促进交联树脂固化的进行；并且能够保证在碳化过程中形成孔径相对较小的孔道。
在任意实施方式中，所述预加热的温度为60℃～120℃，可选为60℃～80℃。
在任意实施方式中，所述预加热的时间t1≥10h，可选为15h～20h。
由此，本申请调控预加热的温度和/或时间控制在上述范围时，可以保证交联树脂充分固化；并且溶剂挥发速度相对较慢，有利于形成孔径适合的孔道结构，且能够保证固态树脂的结构稳定性。
在任意实施方式中，所述碳化过程包括第一碳化过程和第二碳化过程，所述第一碳化过程的温度为500℃～800℃，且所述第一碳化过程的时间为2h～3h；和/或，所述第二碳化过程的温度为800℃～1000℃，且所述第二碳化过程的时间为3h～5h。
由此，第一碳化过程可以在恒温条件下进行，在此过程中，致孔剂可能发生缓慢气化过程，在致孔剂气化挥发的过程中，致孔剂刻蚀树脂内部结构，从而形成孔径相对较小的孔道，整体孔道结构形式较为均匀，由此构成初步的碳骨架结构。第二碳化的温度相对较高，致孔剂可以快速气化，有利于造孔过程的快速完成。并且通过多次碳化过程，可以保证多孔碳基体颗粒的骨架结构的稳定性以及合适的孔隙率。
在任意实施方式中，基于碳基体颗粒的质量，所述硅前驱体的加入量大于等于40％；可选为40％～60％。硅前驱体的加入量满足上述范围时，能够使得碳基体颗粒的孔中均匀分散有硅基纳米颗粒，以此保证硅碳复合材料的容量。
在任意实施方式中，所述化学气相沉积的沉积温度小于等于600℃；可选为450℃～550℃。上述沉积温度能够保证硅前驱体有效生成硅纳米颗粒并沉积于碳基体颗粒内。
本申请的第三方面提供一种二次电池，所述二次电池包括负极极片，所述负极极片包括根据上述第一方面所述的任一实施方式的硅碳复合材料或包括根据上述第二方面所述的任一实施方式的方法得到的硅碳复合材料。
本申请第四方面提供一种用电装置，其包括本申请第三方面的二次电池。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请的二次电池的一实施方式的示意图。
图2是图1的二次电池的实施方式的分解示意图。
图3是本申请的电池模块的一实施方式的示意图。
图4是本申请的电池包的一实施方式的示意图。
图5是图4所示的电池包的实施方式的分解示意图。
图6是包含本申请的二次电池作为电源的用电装置的一实施方式的示意图。
图7是本申请实施例1所示的多孔碳基体颗粒的截面相貌图；
图8是图7所示的多孔碳基体颗粒的局部放大图。
图9是对比例1所示的多孔碳基体颗粒的截面相貌图。
附图未必按照实际的比例绘制。
附图标记说明如下：
1、电池包；2、上箱体；3、下箱体；4、电池模块；
5、二次电池；51、壳体；52、电极组件；
53、盖板；
6、用电装置。
具体实施方式
以下，详细说明具体公开了本申请的硅碳复合材料及制备方法、二次电池和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，方法包括步骤(a)和(b)，表示方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，提到方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到方法，例如，方法可以包括步骤(a)、(b)和(c)，也可包括步骤 (a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
随着二次电池应用范围的推广，对二次电池性能例如能量密度的要求逐步提升。负极活性材料对二次电池性能具有显著影响，碳和硅作为负极活性材料的常用材料，得到了广泛的研究。碳颗粒的理论比容量较低，且碳颗粒的嵌锂电位较低，容易造成锂析出，引发安全问题。硅在常温下能够和锂形成硅锂合金，其理论比容量相对较高；且硅的嵌锂电位略高于石墨，能够降低锂析出的风险。但是微米级的硅材料在脱嵌锂反应过程中体积变化可能大于300％，体积变化较大，体积不断发生变化的硅颗粒容易造成活性材料表面的固体电解质界面膜(Solid-Electrolyte Interphase，SEI膜)破裂再生，SEI膜反复生长，不仅会不断消耗锂和电解液，还会限制锂离子的传输，降低活性材料的电接触，增加阻抗；并且微米级的硅材料还会存在破裂粉化现象，破裂粉化后不断露出新鲜的硅表面，形成新的SEI膜，增加SEI膜的厚度，导致锂离子的传输路径延长。
鉴于碳颗粒和硅颗粒存在的优势和劣势，发明人考虑将碳颗粒和硅颗粒进行复合，但经过发明人深入研究发现，简单的复合操作并不能有效地改善负极活性材料的结构稳定性，且不能兼顾改善二次电池的循环寿命和能量密度。
针对上述问题，发明人对硅碳复合材料进行了改进，在碳基体颗粒的三维网络交联的孔结构中形成硅基纳米颗粒，碳基体颗粒的两个以上的孔交错设置且彼此连通，可以提供硅基纳米颗粒的空间较多，易于大量储硅；并且碳基体颗粒与硅基纳米颗粒复合时，硅基纳米颗粒不易发生团聚，能够均匀分散于孔结构中；碳基体颗粒和硅基纳米颗粒复合后，可以提高硅碳复合材料的导电性，同时缓解硅在脱嵌锂过程中的体积效应，且能够充分承受硅基纳米颗粒的应力变化，保证硅碳复合材料的结构稳定性，提高硅碳复合材料的循环稳定性和储锂能力，由此在硅碳复合材料应用于二次电池时，提高二次电池的循环性能和能量密度。接下来对硅碳复合材料的技术方案进行详细说明。
硅碳复合材料
第一方面，本申请提供一种硅碳复合材料，所述硅碳复合材料包括：碳基体颗粒，所述碳基体颗粒包括三维网络交联的孔结构；以及硅基纳米颗粒，其至少一部分设置于所述三维网络交联的孔结构中。
上述三维网络交联的孔结构通常是指在碳基体颗粒形成的孔结构中，存在两个或者多个孔相互联通或交错且相互共用孔容积的结构。
本申请的碳基体颗粒具有稳定的多孔骨架结构，其支撑能力较强，表现为应力能力较高，且具有优异的机械性能和导电性；其碳基体颗粒包括三维网络交联的孔结构，可供设置硅基纳米颗粒的空间较多，可以用于大量储硅；在多孔碳基体颗粒与硅基纳米颗粒复合时，硅基纳米颗粒不易发生团聚，能够均匀分散于碳基体颗粒的孔中；在碳基体颗粒与硅基纳米颗粒复合后，可以提高硅碳复合材料的导电性，同时缓解硅在脱嵌锂过程中的体积效应，且能够充分承受硅基纳米颗粒的应力变化，保证硅碳复合材料的结构稳定性，提高硅碳复合材料的循环稳定性和储锂能力，由此在硅碳复合材料应用于二次电池时，提高二次电池的循环性能和能量密度。
硅碳复合材料的孔结构可以采用本领域已知的设备和方法进行测试。例如，可以通过使用扫描电子显微镜(例如ZEISS Sigma 300)进行测试。作为示例，可以按照如下步骤操作：首先将包含所述硅碳复合材料的负极极片裁成一定尺寸的待测样品(例如6mm×6mm)，用两片导电导热的薄片(如铜箔)将待测样品夹住，将待测样品与薄片之间用胶(如双面胶)粘住固定，用一定质量(如400g左右)平整铁块压一定时间(如1h)，使待测样品与铜箔间缝隙越小越好，然后用剪刀将边缘剪齐，粘在具有导电胶的样品台上，样品略突出样品台边缘即可。然后将样品台装进样品架上锁好固定，打开氩离子截面抛光仪(例如IB-19500CP)电源并抽真空(例如10Pa-4Pa)，设置氩气流量(例如0.15MPa)和电压(例如8KV)以及抛光时间(例如2小时)，调整样品台为摇摆模式开始抛光，抛光结束后，使用扫描电子显微镜(例如ZEISS Sigma 300)得到待测样品的离子抛光断面形貌(CP)图片。
本申请的发明人经深入研究发现，当本申请的硅碳复合材料在满足上述设计的基础上，如果还可选地满足下述参数中的一个或几个时，可以进一步改善电池的性能。
在一些实施例中，所述碳基体颗粒的表层区域中至少一部分孔的孔尺寸大于所述碳基体颗粒的内部区域的孔尺寸。
表层区域是指从碳基体颗粒的表面向颗粒内部延伸500nm-800nm的深度构成的区域；内部区域是指碳基体颗粒中除了表层区域以外的区域。
在一些实施例中，所述三维网络交联的孔结构在所述碳基体颗粒中呈现层状分布。
在一些实施例中，所述硅碳复合材料在20000N的作用力下进行第1次压下并保压20s时的粉体压实密度记为P 11g/cm 3；所述硅碳复合材料在20000N的作用力下进行第20次压下并保压20s时的压实密度记为P 21g/cm 3，所述硅碳复合材料满足：1.00＜P 21/P 11≤1.20；可选地，1.02≤P 21/P 11≤1.10。
在一些实施例中，1.10≤P 11≤1.40；可选地，1.12≤P 11≤1.35。
将P 21/P 11记作M，M的大小可以用来表示在压实硅碳复合材料过程中的应力应变能力变化。M值在上述范围时，硅碳复合材料的抗压能力相对较强，从而能够提高硅碳复合材料在作为负极活性材料时的抗压性能，保证负极膜层的结构稳定性，从而进一步改善电池的循环性能。示例性地，P 21/P 11可以为1.00、1.02、1.10或1.20。 P 21/P 11为1.00时，表示硅碳复合材料的抗压能力较好，不易发生压缩变形。
材料的粉体压实密度为本领域公知的含义，可采用本领域已知的方法测试。例如可参照GB/T 24533-2009，使用电子压力试验机(如UTM7305)测试：将一定质量G的待测粉末样品放于压实专用模具上(底面积S)，设置不同压力(本申请中可采用20000N或50000N)，保压20s，卸除压力，等待10s，在设备上读出该压力下粉末压实后的厚度H，计算可得该压力下的压实密度，材料在该压力下的压实密度＝G/(H*S)。
本申请的硅碳复合材料具有特定的结构，且将硅碳复合材料在上述测试条件下的粉体压实密度控制在特定范围内，可以使得硅碳复合材料在具有较高克容量的同时还具有较好的抗压性，有效保证了负极膜层的结构稳定性，从而使得含有该材料的二次电池在具有较高能量密度的前提下同时兼顾较好的循环性能。
在一些实施例中，所述碳基体颗粒中孔径大于100nm的孔的孔容积总和记为V 1cm 3/g，所述碳基体颗粒中孔径小于等于100nm的孔的孔容积总和记为V 2cm 3/g；所述碳基体颗粒满足：1＜V 2/V 1≤30；可选地，3≤V 2/V 1≤25。示例性地，V 2/V 1可以为1.5、2.5、2.8、3.0、3.5、4、4.5、5、6、7、8、9、10、15、20或25；或者是上述任意两个数值组成的范围。例如，1.5≤V 2/V 1≤6，2.5≤V 2/V 1≤10，3≤V 2/V 1≤8，2.8≤V 2/V 1≤6，3≤V 2/V 1≤10。
通过调控多孔碳基体颗粒中特定尺寸的孔的总孔容积比例，能够保证碳基体颗粒的孔径分布适中，有利于后续含硅前驱体进入碳基体颗粒的孔中，降低硅沉积于碳基体颗粒表面的风险；且有利于碳基体颗粒趋近于沉积饱满，从而使得沉积硅后所形成的硅碳复合颗粒的比表面积适中，能够保证其可逆容量。
上述孔容积总和可以采用本领域公知的仪器和方法测定，例如，测试方法可以参考GB/T 19587-2004，采用介孔孔径分布测试BJH(Barret joyner Halenda)，在微-介孔模型下采用气体吸脱附方法测试并选取吸附支数据，分别测定并统计孔径大于100nm的孔体积总和V 1和孔径小于等于100nm的孔的孔容积总和V 2。
在一些实施例中，采用气体吸脱附方法测试时，所述碳基体颗粒中孔径大于100nm的孔的总孔容积记为V 1cm 3/g，则V 1≥0.01，可选地，0.01≤V 1≤0.5。
在一些实施例中，在采用气体吸脱附方法测试时，所述碳基体颗粒中孔径小于等于100nm的孔的总孔容积记为V 2cm 3/g，则V 2≥0.05，可选地，0.05≤V 2≤1.1。
在一些实施例中，所述碳基体颗粒的孔隙率记为W，40％≤W≤80％；可选地，50％≤W≤70％。
碳基体颗粒的孔隙率满足上述范围时，孔占据骨架的体积适当，既能够保证骨架结构的稳定性，又能够满足沉积硅的容量，硅基纳米颗粒附着于孔中，硅基纳米颗粒和多孔碳基体颗粒可以协同发挥作用，从而提高硅碳复合材料的容量和导电性。可选地，40≤W≤80；示例性地，多孔碳基体颗粒的孔隙率W％可以为10％、15％、20％、25％、30％、35％、40％、45％、50％、55％、60％、65％、70％、75％或80％；或者是上述任意两个数值组成的范围。
在本申请中，孔隙率是指颗粒内孔体积占据碳基体颗粒总体积的比率。孔隙率可以按照GB/T24586，采用气体置换法测量。孔隙率W＝(L1-L2)/L1*100％，其中L1是样品的表观体积，L2是样品的真实体积。)
在一些实施例中，所述碳基体颗粒在50000N作用力下的粉体压实密度记为P g/cm 3，0.4≤P≤1.1；可选地，0.6≤P≤0.9。其中，P可以按照上述提供的材料的粉体压实密度测试方法进行测试。
通过调节碳基体颗粒的粉体压实密度在合适的范围内，能使负极膜层具有较高的压实密度，进而保证二次电池具有较高的能量密度。此外，通过调节碳基体颗粒的粉体压实密度在合适的范围内，还能使负极膜层在循环过程中具有较强的维持孔道结构的能力，由此负极极片的电解液浸润性更好，能更好地提升二次电池的循环性能。示例性地，碳基体颗粒在50000N作用力下的粉体压实密度P g/cm 3可以为0.6g/cm 3、0.65g/cm 3、0.7g/cm 3、0.75g/cm 3、0.8g/cm 3、0.85g/cm 3、0.9g/cm 3、1.0g/cm 3或1.1g/cm 3；或者是上述任意两个数值组成的范围。
在一些实施例中，所述碳基体颗粒的真密度记为ρg/cm 3，1.7≤ρ≤2.5；可选地，1.9≤ρ≤2.3。
通过调节碳基体颗粒的真密度在合适的范围内，能够使得负极膜层具有相对较高的比容量，从而能够提高二次电池的能量密度。示例性地，碳基体颗粒的真密度ρg/cm 3可以为1.7g/cm 3、1.8g/cm 3、1.9g/cm 3、2.0g/cm 3、2.1g/cm 3、2.2g/cm 3、2.3g/cm 3、2.4g/cm 3或2.5g/cm 3；或者是上述任意两个数值组成的范围。
在本申请中，材料的真密度为本领域公知的含义，其是指材料在绝对密实的状态下单位体积的固态物质的实际质量，即去除材料内部空隙或者颗粒间的空隙后的密度；其可以采用本领域已知的仪器及方法进行测试。例如，测试方法可以参考GB/T24586-2009，测试仪器可以采用真密度测试仪。作为示例，可以按照如下步骤操作：取洁净干燥的样品杯放置在天平，清零，将一定量粉末样品加入到样品杯中(例如，样品可以占样品杯体积的1/2)，记录所取样品的质量，将装有样品的样品杯置于真密度测试仪密闭测试，通入氦气，检测样品室和膨胀室中的气体的压力，再根据玻尔定律来计算真实体积，进而计算真密度。
在一些实施例中，所述碳基体颗粒包括石墨、软碳和硬碳中的一种或几种。上述材料在制备成多孔结构时，有利于硅基纳米颗粒设置于多孔结构的孔中；且其结构稳定性相对较高。
在一些实施例中，所述硅基纳米颗粒包括硅氧化合物、预锂硅氧化合物、非晶硅、晶体硅和硅碳复合物中的一种或几种；可选地，所述硅基纳米颗粒包括非晶硅。
非晶硅在各个方向可以均匀膨胀，从而对多孔碳基体颗粒造成均匀挤压，多孔碳基体颗粒可以有效地缓解非晶硅的体积膨胀。晶体硅的结构相对更稳定，更有利于充分发挥其容量特性。硅碳复合物预先将碳和硅复合为化合物后，形成于多孔碳基体颗粒的孔中，硅碳复合物的体积膨胀相对较小，从而能够减轻对多孔碳基体颗粒造成的应力。示例性地，硅碳复合物可以为碳化硅。
负极活性材料的晶体结构可以采用本领域已知的设备和方法进行测试。作为示例，可以按照如下步骤操作：选择一定直径的微栅网(如直径3mm)，用尖头镊子夹住微栅网边缘，将其膜面朝上(在灯光下观察显示有光泽的面，即膜面)，轻轻平放在白色滤纸上；取适量硅颗粒样品(如1g)加入盛有适量乙醇的烧杯中，进行超声振荡10min～30min；用玻璃毛细管吸取，然后滴2-3滴该待测样品到微栅网上；烘箱烘烤5min后，将滴有待测样品的微栅网放置到样品台上，用透射电子显微镜(如，日立HF-3300S Cs-corrected STEM)在一定放大倍率(例如60000倍)下进行测试，即可得到待测样品的透射电子显微镜(TEM)图。若有明显的晶格条纹(例如，条纹间距约等于0.331nm)，即为晶体硅；若未观察到晶格条纹，即为非晶硅。
在一些实施例中，所述硅基纳米颗粒在所述硅碳复合材料中的质量比大于等于40％；可选为40％-60％。
硅基纳米颗粒在硅碳复合材料中的质量比在上述范围时，硅碳复合材料的容量相对较高。
硅基纳米颗粒在所述硅碳复合材料中的质量可以采用本领域已知的方法和设备测试，例如可参考EPA 6010D-2014标准进行测定；具体地，可以采用ICP-OES(元素分析-电感耦合等离子体发射光谱法)测试，先将待测固体用强酸溶解为液体，随后通过雾化的方式将液体引入ICP光源，进一步待测气态原子在强磁场中发生电离和激发后，由激发态恢复到基态；在上述过程中释放能量并被记录为不同的特征谱线，进行痕量元素定量分析。
碳元素在所述硅碳复合材料中的质量可以采用本领域已知的方法和设备测试，例如可以采用TG(热失重)测试，将硅碳复合材料作为样品在含氧条件下进行热处理(25℃升温至1000℃)，记录热处理前后的样品质量，前后样品质量的差值即碳被烧蚀的质量，由此可知样品中碳含量。
在一些实施方式中，硅基纳米颗粒的粒径记为D si nm，D si≤100；可选地，2≤D si≤80。
硅基纳米颗粒的粒径相对较小，可以显著缓解硅体积变化造成的较高压力，有利于保证硅碳复合材料整体的结构稳定性，提升二次电池的循环稳定性；且能够显著缩短锂离子的传输距离，有利于改善硅碳复合材料的动力学性能。可选地，10≤D si≤80；示例性地，硅基纳米颗粒的粒径可以为2nm、3nm、5nm、8nm、10nm、12nm、15nm、20nm、25nm、30nm、40nm、50nm、60nm、70nm或80nm；或者是上述任意两个数值组成的范围。
在本申请中，硅基纳米颗粒的粒径可以依据JIS/K0131-1996测试标准测试样品的XRD图，根据样品的XRD图，取Si(111)晶面衍射峰的半高峰宽β和衍射角θ，代入Debye-Scherrer公式计算，得纳米硅颗粒粒径。Debye-Scherrer公式如下：Dhkl＝kλ/(βcosθ)，式中，Dhkl表示纳米硅颗粒的粒径，单位nm；k表示Scherrer常数，0.89；λ表示入射X射线波长，0.15406nm；β表示衍射峰的半高峰宽，单位rad；θ表示衍射角，单位度。
在一些实施方式中，硅碳复合材料的体积分布粒径Dv10满足：Dv10≤5μm；可选地，3μm≤Dv10≤5μm；示例性地，Dv10可以为1μm、2μm、3μm、4μm或5μm；或者是上述任意两个数值组成的范围。
在一些实施方式中，硅碳复合材料的体积分布粒径Dv50满足：Dv50≤10μm；可选地，5μm Dv50≤8μm；示例性地，Dv50可以为1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm或10μm；或者是上述任意两个数值组成的范围。
硅碳复合材料的体积分布粒径Dv50满足上述范围时，硅碳复合材料的结构相对稳定，动力学性能相对较好，有利于提高硅碳复合材料的首次库伦效率。
在一些实施方式中，硅碳复合材料的体积分布粒径Dv90满足：Dv90≤20μm；可选地，8μm Dv90≤18μm；示例性地，Dv90可以为1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm、10μm、11μm、12μm、13μm、14μm、15μm、16μm、17μm或18μm；或者是上述任意两个数值组成的范围。
在一些实施方式中，硅碳复合材料的粒度分布满足：(Dv90-Dv10)/Dv50≤1.6。示例性地，(Dv90-Dv10)/Dv50可以为1.6、1.5、1.4、1.3、1.2、1.1、1或0.75。可选地，1.4≤(Dv90-Dv10)/Dv50≤1.6。
硅碳复合材料的粒度分布满足上述范围时，硅碳复合材料的整体平均粒径较为适中，且粒度分布较为平均，有利于提高硅碳复合材料整体的性能的均一性。
材料的Dv10、Dv50、Dv90均为本领域公知的含义，可以采用本领域已知的方法测试。例如可以参照标准GB/T 19077.1-2016，使用激光粒度分析仪(如Malvern Master Size 3000)测定。
其中，Dv10、Dv50、Dv90的物理定义如下：
Dv10：所述材料累计体积分布百分数达到10％时所对应的粒径；
Dv50：所述材料累计体积分布百分数达到50％时所对应的粒径；
Dv90：所述材料累计体积分布百分数达到90％时所对应的粒径。
在一些实施方式中，硅碳复合材料的比表面积SSA满足：2m 2/g≤SSA≤10m 2/g。
硅碳复合材料的比表面积SSA满足上述范围时，比表面积的范围较为适中，材料的动力学性能较好，有利于材料的首次库伦效率。可选地，3m 2/g≤SSA≤7m 2/g。示例性地，硅碳复合材料的比表面积SSA可以为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；或者是上述任意两个数值组成的范围。
在本申请中，比表面积SSA为本领域公知的含义，通常表面积以m 2/g的单位表示，可采用本领域已知的方法和仪器测试。例如可参照GB/T 19587-2017，采用惰性气体(例如氮气)吸附比表面积分析测试方法测试，并用BET(Brunauer Emmett Teller)法计算得出，其中氮气吸附比表面积分析测试可以通过美国Micromeritics公司的Tri-Star3020型比表面积孔径分析测试仪进行。
制备硅碳复合材料的方法
第二方面，本申请还提供了一种制备硅碳复合材料的方法。
所述方法包括：
S100，将交联树脂、致孔剂和溶剂混合形成混合体系；
S200，预加热混合体系，以使溶剂挥发并使得交联树脂固化形成固态树脂；
S300，破碎固态树脂形成颗粒状树脂；
S400，碳化颗粒状树脂，以使致孔剂挥发并刻蚀颗粒状树脂形成具有三维网状交联结构的碳基体颗粒；
S500，通过化学气相沉积，将包含硅前驱体的气体生成硅基纳米颗粒，使得硅基纳米颗粒中的至少一部分附着于碳基体颗粒的孔中。
本申请通过交联树脂制备得到碳基体颗粒，碳基体颗粒具有三维网状交联结构的孔结构，该孔结构包含两个以上相互交错的孔，且孔与孔之间可以彼此连通；在此并排除部分孔之间平行设置。具有三维网状交联结构的碳基体颗粒的机械强度较好，其支撑能力较强，表现为应力能力较高，且具有优异的机械性能和导电性。硅前驱体通过化学气相沉积沉积于具有三维网状交联结构的碳基体颗粒上形成硅基纳米颗粒，从而使得碳基体颗粒和硅基纳米颗粒复合为硅碳复合材料，碳元素和硅元素能够协同发挥作用，在提高硅碳复合材料的导电性和容量的基础上，碳基体颗粒可以在一定程度上缓解硅基纳米颗粒在脱嵌锂过程中的体积膨胀，从而能够提高硅碳复合材料的循环稳定性和储锂能力，由此在硅碳复合材料应用于二次电池时，提高二次电池的循环性能和能量密度。
尤其是硅碳复合材料满足以下要求时：碳基体颗粒具有表层区域和位于表层区域内的内部区域，碳基体颗粒的表层区域中至少一部分孔的孔尺寸大于所述碳基体颗粒的内部区域的孔尺寸。碳元素和硅元素能够更好地发挥协同作用，提高二次电池的性能。
在步骤S100中，将交联树脂、致孔剂和溶剂混合为混合体系。
在一些实施方式中，交联树脂可以包括线性酚醛树脂、可溶性酚醛树脂、环氧树脂和聚氨酯、呋喃树脂、脲醛树脂中的一种或多种；上述交联树脂自身具有一定的交联度，其结构稳定性相对较好。
在一些实施方式中，溶剂可以包括液态醇、醚类、酮类等，示例性地，液态醇包括甲醇、乙醇、乙二醇、聚乙二醇(低分子量)、丙三醇和异丙醇中的一种或多种。液态醇能够溶解交联树脂和致孔剂，将三者混合为较为均一的体系。预加热混合体系的过程中，溶剂大量蒸发，在溶剂蒸发的过程中，交联树脂逐步固化，且其内部会形成较大的孔道结构，初步形成多孔骨架结构。醚类可以包括丁醚和二甲醚等。酮类可以包括丙酮等。
进一步地，基于混合体系的总质量计，交联树脂的质量含量为a1；基于混合体系的总质量计，溶剂的质量含量为a2，混合体系满足：0.1≤a1/a2≤10。
交联树脂的质量含量与溶剂的质量含量在上述范围时，可以保证溶剂充分溶解交联树脂和致孔剂，保证三者形成均一的混合体系；更有利于形成本申请特定的孔结 构，且所形成的固态树脂具有良好的机械强度。可选地，0.5≤a1/a2≤2；示例性地，a1/a2可以为0.1、0.2、0.5、0.8、1、1.5、2、3、4、5、6、7、8、9或10；或者是上述任意两个数值组成的范围。
在一些实施方式中，致孔剂包括氯化盐、碳酸盐、醋酸盐中的一种或多种。示例性地，氯化盐可以包括氯化钠、氯化钾和氯化锌中的一种或多种；碳酸盐可以包括碳酸钠、碳酸胺和碳酸钾中的一种或多种；醋酸盐可以包括醋酸锌、醋酸铵和醋酸钠中的一种或多种。上述致孔剂在碳化过程中，能够刻蚀颗粒状树脂的结构，以形成孔径较小的孔道，该孔道能够连通溶剂挥发所形成的孔道，从而更有利于形成本申请特定的孔结构；并且致孔剂能够继续扩大溶剂挥发所形成的孔道，从而保证多孔结构的孔径在合适的范围内。
进一步地，基于混合体系的总质量计，交联树脂的质量含量为a1；基于混合体系的总质量计，致孔剂的质量含量为a3，混合体系满足：0.1≤a1/a3≤5。
交联树脂的质量含量与致孔剂的质量含量在上述范围时，有利于致孔剂吸水促进交联树脂固化的进行；并且能够保证在碳化过程中形成孔径相对较小的孔道。可选地，0.5≤a1/a3≤3；示例性地，a1/a3可以为0.1、0.2、0.3、0.5、0.6、0.8、1、1.5、2、2.5、3、3.5、4或5；或者是上述任意两个数值组成的范围。
在一些实施方式中，步骤S100中，在搅拌状态下混合为混合体系；搅拌转速为100r/min～1500r/min。
在上述搅拌状态下搅拌混合体系，有利于交联树脂、致孔剂和溶剂的均匀混合。可选地，搅拌转速为500r/min～1000r/min。示例性地，搅拌转速可以为100r/min、120r/min、150r/min、180r/min、200r/min、250r/min、300r/min、350r/min、400r/min、450r/min、500r/min、550r/min、600r/min、650r/min、700r/min、750r/min、800r/min、900r/min、1000r/min、1100r/min、1200r/min、1300r/min、1400r/min或1500r/min；或者是上述任意两个数值组成的范围。
在步骤S200中，热处理混合体系，交联树脂中的分子不断交联形成大分子，并且在交联过程中会发生脱水现象，脱出的水容易和致孔剂反应，即致孔剂能够吸水，从而进一步促进交联过程的发生，提高交联程度。
在一些实施方式中，预加热的温度为60℃～120℃，可选为60℃～80℃。
预加热的温度控制在上述范围时，可以保证交联树脂充分固化；并且溶剂挥发速度相对较慢，更有利于形成本申请特定的孔道结构，且能够保证固态树脂的结构稳定性，从而能够改善固态树脂后续形成的硅碳复合材料的抗压性能。示例性地，预加热的温度可以为60℃、65℃、70℃、75℃、80℃、85℃、90℃、95℃、100℃、105℃、110℃、115℃或120℃；或者是上述任意两个数值组成的范围。
步骤S300中，破碎固态树脂形成颗粒状树脂；在一些实施方式中，可以对固态树脂进行再加热，再加热的温度为为100℃～200℃。
再加热的过程可以促使溶剂的进一步挥发，继续进行孔道的形成；并且能够促进树脂的进一步脱水和交联，提高颗粒状树脂的机械强度，提高颗粒状树脂的结构稳 定性。
在一些实施方式中，可以采用多次破碎的过程，例如粗破、细破等，以期获取满足预设粒径的颗粒状树脂，作为碳前驱体。预设粒径范围可以为微米级。
在一些实施方式中，破碎之后还可以对颗粒状树脂进行除杂、除磁和粒度分级等操作，以保证获得的颗粒状树脂满足工艺要求。除杂、除磁和粒度分级均可以采用本领域公知的技术进行操作，在此并不对其进行限定。
步骤S400中，碳化颗粒状树脂，以形成多孔碳基体颗粒。
在一些实施方式中，碳化温度可以为500℃～1200℃。
碳化温度在上述范围时，可以保证颗粒状树脂充分碳化，并能够在碳基体颗粒的内部形成三维交联孔结构，以利于硅基纳米颗粒的沉积，且所形成的碳基体颗粒的骨架结构的结构稳定性较高，具有良好的抗压性能。
进一步地，碳化过程可以包括第一碳化过程和第二碳化过程，其中第一碳化过程的温度为500℃～800℃，且所述第一碳化过程的时间为2h～3h；第二碳化过程的温度可以为800℃～1000℃，且所述第二碳化过程的时间为3h～5h；第一碳化过程的温度小于第二碳化过程的温度。第一碳化过程的升温速率相对较低例如以1～2℃/min的速率升温，且第一碳化过程在升温至预定温度后，可以保持恒温处理一定时间例如恒温处理1h，在此过程中，致孔剂可能发生缓慢气化过程，在致孔剂气化挥发的过程中，致孔剂刻蚀树脂内部结构，从而形成孔径相对较小的孔道，整体孔道结构形式较为均匀，由此构成初步的碳骨架结构。第二碳化的温度相对较高，可以使致孔剂快速气化，致孔剂以气体的形式对碳基体造孔并打通孔之间间隔形成三维交联孔结构，同时持续的逸散对碳基体外围部分逐步蚀刻扩孔，可以使三维网络交联的孔结构在所述碳基体颗粒中呈现层状分布。并且通过多次碳化过程，可以保证多孔碳基体颗粒的骨架结构的稳定性以及合适的孔隙率。
进一步地，可以对多孔碳基体颗粒进一步筛分处理，以获取符合粒度要求的颗粒。筛分方法可采用本领域公知的手段进行，在此不对其进行限定。
步骤S500中，硅基纳米颗粒中的至少一部分附着于所述碳基体颗粒的孔中。
在一些实施方式中，基于碳基体颗粒的质量，所述硅前驱体的加入量大于等于40％；可选为40％～60％。
硅前驱体的加入量满足上述范围时，能够使得碳基体颗粒的孔中均匀分散有硅基纳米颗粒，以此保证硅碳复合材料的容量。
在一些实施方式中，硅前驱体可以包括硅氧化合物、预锂硅氧化合物、晶体硅、非晶体硅和硅碳复合物中的一种或多种。上述硅前驱体能够在碳基体颗粒的孔中形成纳米级的硅基颗粒，有利于均匀分散于孔道中。示例性地，硅碳复合物可以为碳化硅。
在一些实施方式中，所述化学气相沉积的沉积温度小于等于600℃；可选为450℃～550℃。上述沉积温度能够保证硅前驱体有效生成硅纳米颗粒并沉积于碳基体颗粒内。
在一些实施方式中，可以预先将碳基体颗粒置于气相沉积炉的加热室中，利用真空泵将加热室抽真空。向加热室内通入保护气，待保护气充满加热室后，将包含硅前驱体的气体通入加热室中，并维持加热室以一定的压力。
在本申请中，可以采用惰性气体作为保护气，将保护气和包含硅前驱体的气体共同输入至多孔碳基体颗粒上。示例性地，惰性气体可以包括氮气、氩气和氦气中的一种或几种。
交联树脂、致孔剂和溶剂原位调和为均一体系，在热处理过程中，溶剂和致孔剂共同造孔，且溶剂和致孔剂能够从交联树脂的内部向外逸散。交联树脂最终转化为碳材料，形成具有交联通孔的多孔碳骨架结构，该多孔碳骨架具有兼顾的应力架构，表现为良好的应力能力，在作为负极活性材料应用于二次电池时，能够改善负极活性材料的结构稳定性，能够改善二次电池的循环性能。
二次电池
第三方面，本申请还提供了一种二次电池。
二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，负极膜层包括负极活性材料。
在一些实施方式中，负极活性材料可以包括本申请第一方面任一实施方式的硅碳复合材料或本申请第二方面任一实施方式的方法制备得到的硅碳复合材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、其它硅基材料、锡基材料和钛酸锂等。其它硅基材料可选自单质硅、硅氧化合物、硅氮复合物以及硅合金中的至少一种。锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺 制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图1是作为一个示例的方形结构的二次电池5。
在一些实施例中，如图1和图2所示，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53用于盖设开口，以封闭容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于容纳腔。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，可根据需求来调节。
本申请的二次电池的制备方法是公知的。在一些实施例中，可将正极极片、隔离膜、负极极片和电解液组装形成二次电池。作为示例，可将正极极片、隔离膜、负极极片经卷绕工艺或叠片工艺形成电极组件，将电极组件置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
在本申请的一些实施例中，根据本申请的二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图3是作为一个示例的电池模块4的示意图。如图3所示，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施例中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图4和图5是作为一个示例的电池包1的示意图。如图4和图5所示，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2用于盖设下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
用电装置
第四方面，本申请提供一种用电装置，用电装置包括本申请的二次电池、电池模块和电池包中的至少一种。二次电池、电池模块和电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动 力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
用电装置可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置的示意图。该用电装置6为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对高功率和高能量密度的需求，可以采用电池包1或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
1、负极极片的制备
1.1硅碳复合材料的制备
(1)分别称取固含量为80％的酚醛树脂500g和无水乙醇500g，搅拌均匀后再称取250g氯化锌加入到上述树脂溶液，满足a1/a2＝1且a1/a3＝2的条件，过程转速为1000r/min持续3h，得到均一树脂溶液。
(2)将溶液转移到受热模具内，置于鼓风烘箱中在60℃的温度下预加热10h，将液态树脂转变为固态；
(3)在空气气氛下，180℃条件下热处理10h，脱除溶剂并加强复合树脂的分子交联程度，形成三维网络结构的碳前驱体；
(4)将上述所得固体破碎为细粉，使得具有如下颗粒参数：Dv50＝7.5um，Dv90＝15um；
(5)进一步对粉末做两步碳化处理，具体如下：室温升温到500℃恒温1h进行预碳化，继续升温到1000℃下进行碳化处理2h，并进行除杂及筛分得到多孔碳基体，其中，多孔碳基体具有呈现三维网状的孔结构，且碳基体颗粒表面区域中至少有部分孔的孔尺寸大于所述碳基体颗粒内部区域的孔尺寸。在本步骤中碳化处理采用分段碳化，即第一碳化过程和第二碳化过程，第一碳化过程的温度小于第二碳化过程的温度。
(6)通过化学气相沉积法将纳米硅沉积于多孔碳基体的孔中，得到硅碳复合材料。其中，制备的硅碳复合材料满足：D V50＝8.2um，D V90＝15.7um，(D V90-D V10)/D V50＝1.56，SSA＝3.1m 2/g，粉体压实密度＝1.1g/cm 3，振实密度＝0.45g/cm 3。
图7和图8示出了多孔碳基体的截面图，其具有呈现三维网络交联的孔结构，且图8还可以看出，三维网络交联的孔结构在碳基体颗粒中呈现层状分布。
1.2负极极片的制备
将负极活性材料(25％上述制备的硅碳复合材料+75％人造石墨)、导电炭黑、增稠剂羧甲基纤维素钠(CMC-Na)、粘结剂丁苯橡胶乳液(SBR)按96.5：1.0：1.0：1.5重量比在适量的去离子水中充分搅拌混合，使其形成均匀的负极浆料；将负极浆料涂覆于负极集流体上，经烘干等工序后，得到负极极片。
1.3正极极片的制备：将正极活性材料LiNi 0.8Co 0.1Mn 0.1O 2(NCM 811)、粘结剂聚偏氟乙烯(PVDF)、导电剂乙炔黑按照质量比为97％:1.5％:1.5％溶于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后制备成正极浆料；将正极浆料均匀涂覆在正极集流体铝箔上，之后经过烘干、冷压、分切，得到正极极片。
1.4隔离膜：采用聚丙烯膜。
1.5电解液的制备：将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按体积比1:1:1混合，然后将LiPF 6均匀溶解在上述溶液中，得到电解液。该电解液中，LiPF 6的浓度为1mol/L。
1.6二次电池的制备：将上述正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件放入外包装中，加入上述制备的电解液，经封装、静置、化成、老化等工序后，得到二次电池。
对比例1
对比例1的二次电池制备工艺与实施例1基本一致，不同点在于，对比例1采用了不同的硅碳复合材料，对比例1的硅碳复合材料制备方法如下：
(1)称取酚醛树脂50g，无水乙醇50g混合成均匀的树脂溶液；
(2)称取TEOS(原硅酸乙酯)溶液15ml，倒入上述树脂溶液，继续搅拌均匀，待TEOS聚合成二氧化硅球体；
(3)称取3ml氨水(25wt％)倒入上述溶液，并将该溶液置于温度调节为40℃的恒温水浴锅中，持续搅拌至乙醇溶液挥发完毕，将所得凝胶真空130℃固化10h得到碳化树脂前驱体；
(4)将所得固体粉末，置于管式炉中800℃热解2h，将粉末用1M HF除杂和清洗后烘干，即得到硅碳复合材料。
图9示出了对比例1的多孔碳基体颗粒的截面形貌图，可以看出其孔结构呈现蜂窝状。
实施例1-5以及对比例的参数如表1所示：
表1
Figure PCTCN2022112206-appb-000001
实施例2-6
实施例2-6采用与实施例1相似的方法制备二次电池，与实施例1不同的是，
实施例2-6调整了硅碳复合材料的制备工艺参数，具体详见表2。
表2
Figure PCTCN2022112206-appb-000002
表3
Figure PCTCN2022112206-appb-000003
测试部分
1电池循环性能
循环次数测试：
将25℃下，将各实施例和对比例制备得到的二次电池以0.5C倍率恒流充电至充电截止电压4.25V，之后恒压充电至电流≤0.05C，静置5min，再以0.33C倍率恒流放电至放电截止电压2V，静置5min，此为一个充放电循环。按照此方法对电池进行循环充放电测试，直至电池容量衰减至80％。此时的循环圈数即为电池在25℃下的循环寿命。
2负极活性材料的克容量
负极活性材料的克容量测试方法如下：取上述各实施例和对比例制备的负极极片，冲切成为1.8cm 2×1.8cm 2的小圆片样品，称量小圆片样品的重量记为M1，称量小圆片样品中集流体的重量记为M2；以金属锂片为对电极，采用聚乙烯(PE)薄膜做为隔离膜，将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)体积比1:1:1混合，然后将LiPF6均匀溶解在上述溶液中得到电解液，其中LiPF 6的浓度为1mol/L，在氩气保护的手套箱中将上述各部分组装成扣式半电池；将所得扣式电池静置12小时后，以0.05C的电流进行恒流放电至0.005V，静置10分钟，以50μA的电 流再进行恒流放电至0.005V；然后以0.1C的电流进行恒流充电值2V，记录充电容量C。负极活性材料的克容量＝C/(M1-M2)。
由表1可知，实施例1通过制备得到具有三维网络交联的孔结构的碳基体颗粒，能够为硅提供的空间较多，可以用于大量储硅，从而改善硅碳复合材料的克容量；另外，由于该种孔结构类型，使得硅能够均匀分散于孔中，不易团聚，且能够缓解硅在脱嵌锂过程中的体积效应，并能够充分承受硅所产生的应力变化，从而保证硅碳复合材料的结构稳定性，由此提高硅碳复合材料的循环稳定性。
而对比例1的碳基体颗粒的孔结构为蜂窝状孔结构，该结构不利于为硅的沉积提供充足的空间，导致硅的沉积量相对较低，硅和碳复合后的材料的克容量相对较小；且硅和碳复合后的材料的整体结构稳定性较差，导致其应用于二次电池时的循环寿命相对较低。
由表2-3可知，实施例1至实施例6通过调节硅碳复合材料的制备工艺参数，可以调节碳基体颗粒的三维网络结构的具体构造，从而能够调节其机械性能和储硅空间；并能够改善硅碳复合材料的抗压性能，从而能够进一步保证包含负极活性材料的负极膜层结构稳定性，进一步改善二次电池的循环性能。
虽然已经参考优选实施例对本申请进行了描述，但在不脱离本申请的范围的情况下，可以对其进行各种改进并且可以用等效物替换其中的部件。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (20)

  1. 一种硅碳复合材料，包括：
    碳基体颗粒，所述碳基体颗粒包括三维网络交联的孔结构；以及
    硅基纳米颗粒，其至少一部分设置于所述三维网络交联的孔结构中。
  2. 根据权利要求1所述的硅碳复合材料，其中，所述碳基体颗粒的表层区域中至少一部分孔的孔尺寸大于所述碳基体颗粒的内部区域的孔尺寸。
  3. 根据权利要求1或2所述的硅碳复合材料，其中，所述三维网络交联的孔结构在所述碳基体颗粒中呈现层状分布。
  4. 根据权利要求1至3中任一项所述的硅碳复合材料，其中，所述硅碳复合材料在20000N作用力下经过1次粉压后测试的粉体压实密度记为P 11g/cm 3，所述硅碳复合材料在20000N作用力下经过20次粉压后测试的压实密度记为P 21g/cm 3，则所述硅碳复合材料满足：1.00＜P 21/P 11≤1.20；可选地，1.02≤P 21/P 11≤1.10。
  5. 根据权利要求1至4中任一项所述的硅碳复合材料，其中，所述硅碳复合材料在20000N作用力下的粉体压实密度记为P 11g/cm 3，则所述硅碳复合材料满足：1.10≤P 11≤1.40；可选地，1.12≤P 11≤1.35。
  6. 根据权利要求1至5中任一项所述的硅碳复合材料，其中，在采用气体吸脱附方法测试时，所述碳基体颗粒中孔径大于100nm的孔的总孔容积记为V 1cm 3/g，所述碳基体颗粒中孔径小于等于100nm的孔的总孔容积记为V 2cm 3/g，则所述碳基体颗粒满足：1＜V 2/V 1≤30；可选地，3≤V 2/V 1≤25。
  7. 根据权利要求1至6中任一项所述的硅碳复合材料，其中，在采用气体吸脱附方法测试时，所述碳基体颗粒中孔径大于100nm的孔的总孔容积记为V 1cm 3/g，则V 1≥0.01，可选地，0.01≤V 1≤0.5；和/或，
    在采用气体吸脱附方法测试时，所述碳基体颗粒中孔径小于等于100nm的孔的总孔容积记为V 2cm 3/g，则V 2≥0.05，可选地，0.05≤V 2≤1.1。
  8. 根据权利要求1至7中任一项所述的硅碳复合材料，其中，所述碳基体颗粒满足条件(1)至条件(4)中的至少一者：
    (1)所述碳基体颗粒的孔隙率记为W，40％≤W≤80％；可选地，50％≤W≤70％；
    (2)所述碳基体颗粒在50000N作用力下的粉体压实密度记为Pg/cm 3， 0.4≤P≤1.1，可选地，0.6≤P≤0.9；
    (3)所述碳基体颗粒的真密度记为ρg/cm 3，1.7≤ρ≤2.5；可选地，1.9≤ρ≤2.3；
    (4)所述碳基体颗粒包括石墨、软碳和硬碳中的一种或几种。
  9. 根据权利要求1至8中任一项所述的硅碳复合材料，其中，
    所述硅基纳米颗粒包括硅氧化合物、预锂硅氧化合物、非晶硅、晶体硅和硅碳复合物中的一种或几种；可选地，所述硅基纳米颗粒包括非晶硅。
  10. 根据权利要求1至9中任一项所述的硅碳复合材料，其中，所述硅基纳米颗粒在所述硅碳复合材料中的质量比大于等于40％；可选为40％～60％。
  11. 根据权利要求1至10中任一项所述的硅碳复合材料，其中，所述硅碳复合材料满足条件(I)至条件(V)中的至少一者：
    (I)所述硅碳复合材料的体积分布粒径Dv10满足：Dv10≤5μm；可选地，3μm≤Dv10≤5μm；
    (II)所述硅碳复合材料的体积分布粒径Dv50满足：Dv50≤10μm；可选地，5μmDv50≤8μm；
    (III)所述硅碳复合材料的体积分布粒径Dv90满足：Dv90≤20μm；可选地，8μm≤Dv90≤18μm；
    (IV)所述硅碳复合材料的粒度分布满足：(Dv90-Dv10)/Dv50≤1.6；可选地，1.4≤(Dv90-Dv10)/Dv50≤1.6；
    (V)所述硅碳复合材料的比表面积SSA满足：2m 2/g≤SSA≤10m 2/g；可选地，3m 2/g≤SSA≤7m 2/g。
  12. 一种如权利要求1-11中任一项所述的硅碳复合材料的制备方法，包括：
    将交联树脂、致孔剂和溶剂混合形成混合体系；
    预加热所述混合体系，以使所述溶剂挥发并使得所述交联树脂固化形成固态树脂；
    破碎所述固态树脂形成颗粒状树脂；
    碳化所述颗粒状树脂，以使所述致孔剂挥发并刻蚀所述颗粒状树脂形成具有三维网状交联结构的碳基体颗粒；
    通过化学气相沉积，将包含硅前驱体的气体生成硅基纳米颗粒，使得所述硅基纳米颗粒中的至少一部分附着于所述碳基体颗粒的孔中。
  13. 根据权利要求12所述的制备方法，其中，
    基于所述混合体系的总质量计，加入所述交联树脂的质量含量记为a1；
    基于所述混合体系的总质量计，加入所述溶剂的质量含量为记a2；
    所述混合体系满足：0.1≤a1/a2≤10；可选地，0.5≤a1/a2≤2。
  14. 根据权利要求12或13所述的制备方法，其中，
    基于所述混合体系的总质量计，加入所述交联树脂的质量含量记为a1；
    基于所述混合体系的总质量计，加入所述致孔剂的质量含量记为a3；
    所述混合体系满足：0.1≤a1/a3≤5；可选地，0.5≤a1/a3≤3。
  15. 根据权利要求12至14中任一项所述的方法，其中，
    所述预加热的温度为60℃～120℃，可选为60℃～80℃；和/或，
    所述预加热的时间为t1≥10h，可选为15h～20h。
  16. 根据权利要求12至15中任一项所述的方法，其中，
    所述碳化过程包括第一碳化过程和第二碳化过程，所述第一碳化过程的温度为500℃～800℃，且所述第一碳化过程的时间为2h～3h；和/或，
    所述第二碳化过程的温度为800℃～1000℃，且所述第二碳化过程的时间为3h～5h。
  17. 根据权利要求12至16中任一项所述的方法，其中，基于所述碳基体颗粒的质量，所述硅前驱体的加入量大于等于40％；可选为40％～60％。
  18. 根据权利要求12至17中任一项所述的方法，其中，所述化学气相沉积的沉积温度小于等于600℃；可选为450℃～550℃。
  19. 一种二次电池，包括负极极片，所述负极极片包括如权利要求1至11中任一项所述的硅碳复合材料或包括如权利要求12至18中任一项所述的制备方法得到的硅碳复合材料。
  20. 一种用电装置，包括如权利要求19所述的二次电池。
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN118032593A (zh) * 2024-04-10 2024-05-14 瑞浦兰钧能源股份有限公司 一种颗粒辊压粘结强度的评估方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103311523A (zh) * 2013-06-04 2013-09-18 清华大学深圳研究生院 具有纳米微孔隙的硅碳复合材料及其制备方法与用途
CN106207108A (zh) * 2016-07-09 2016-12-07 太原理工大学 基于高分子发泡微球的硅碳复合材料及其制备方法与应用
CN107069010A (zh) * 2017-04-24 2017-08-18 广东烛光新能源科技有限公司 一种硅碳负极材料及其制备方法
CN107134567A (zh) * 2017-04-24 2017-09-05 广东烛光新能源科技有限公司 硅碳负极材料及其制备方法
US20200358081A1 (en) * 2019-05-06 2020-11-12 Nanotek Instruments, Inc. Protected anode active material particles for rechargeable lithium batteries

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103311523A (zh) * 2013-06-04 2013-09-18 清华大学深圳研究生院 具有纳米微孔隙的硅碳复合材料及其制备方法与用途
CN106207108A (zh) * 2016-07-09 2016-12-07 太原理工大学 基于高分子发泡微球的硅碳复合材料及其制备方法与应用
CN107069010A (zh) * 2017-04-24 2017-08-18 广东烛光新能源科技有限公司 一种硅碳负极材料及其制备方法
CN107134567A (zh) * 2017-04-24 2017-09-05 广东烛光新能源科技有限公司 硅碳负极材料及其制备方法
US20200358081A1 (en) * 2019-05-06 2020-11-12 Nanotek Instruments, Inc. Protected anode active material particles for rechargeable lithium batteries

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN118032593A (zh) * 2024-04-10 2024-05-14 瑞浦兰钧能源股份有限公司 一种颗粒辊压粘结强度的评估方法

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