WO2025189397A1 - 硅碳复合材料、二次电池及电子装置 - Google Patents

硅碳复合材料、二次电池及电子装置

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Publication number
WO2025189397A1
WO2025189397A1 PCT/CN2024/081460 CN2024081460W WO2025189397A1 WO 2025189397 A1 WO2025189397 A1 WO 2025189397A1 CN 2024081460 W CN2024081460 W CN 2024081460W WO 2025189397 A1 WO2025189397 A1 WO 2025189397A1
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WIPO (PCT)
Prior art keywords
silicon
carbon composite
composite material
region
carbon
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Pending
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PCT/CN2024/081460
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English (en)
French (fr)
Inventor
胡光武
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to PCT/CN2024/081460 priority Critical patent/WO2025189397A1/zh
Publication of WO2025189397A1 publication Critical patent/WO2025189397A1/zh
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

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

Definitions

  • the present application relates to the field of electrochemical energy storage, and in particular to a silicon-carbon composite material, a secondary battery using the silicon-carbon composite material, and an electronic device including the secondary battery.
  • Graphite is the most widely used anode material, offering advantages such as high efficiency and a stable charge-discharge platform. However, its low specific capacity hinders its further application. Compared to graphite, elemental silicon is considered an ideal anode material to replace graphite due to its higher theoretical specific capacity and suitable operating voltage.
  • silicon has low conductivity and undergoes huge volume expansion during the alloying/de-alloying process, which seriously restricts the large-scale application of elemental silicon in lithium-ion batteries.
  • the present application provides a silicon-carbon composite material, and also provides a secondary battery using the silicon-carbon composite material and an electronic device including the secondary battery.
  • the present application provides a silicon-carbon composite material.
  • a cross-section of the silicon-carbon composite material includes a first region and a second region.
  • the first region is a region 2 ⁇ m radially inward from the edge of the cross-section of the silicon-carbon composite material
  • the second region is a region 4 ⁇ m radially outward from the center of the silicon-carbon composite material.
  • the pore size in the first region is smaller than the pore size in the second region.
  • pores in both the first and second regions of the silicon-carbon composite material there are pores in both the first and second regions of the silicon-carbon composite material.
  • the pores can not only buffer the volume expansion of silicon and reduce the volume expansion of the silicon-carbon composite material, but also provide good electron and ion transmission channels, thereby improving the cycle performance, expansion performance and rate performance of the silicon-carbon composite material.
  • the pore size of the first region is smaller than the pore size of the second region, which can give full play to the capacity contribution of silicon in the silicon-carbon composite material to obtain a silicon-carbon composite material with a high specific capacity.
  • the pore size in the first region is smaller, which can reduce the solid electrolyte membrane (SEI membrane) formed by the electrolyte in the pores and improve the first coulomb efficiency and delithiation specific capacity of the silicon-carbon composite material.
  • SEI membrane solid electrolyte membrane
  • the pore size in the first region is a, 1nm ⁇ a ⁇ 6nm. This is beneficial to improving the kinetics of lithium insertion and extraction of the silicon-carbon composite material, thereby improving the specific capacity and first coulombic efficiency of the silicon-carbon composite material.
  • the pore size in the second region is b, 2nm ⁇ b ⁇ 8nm, which is beneficial to improving the specific capacity, first coulombic efficiency, and cycle performance of the silicon-carbon composite material.
  • the differential capacity curve of the silicon-carbon composite material for lithium delithiation has a characteristic peak between 600 mV and 750 mV. This characteristic peak indicates that the lithium delithiation reaction occurs in the silicon-carbon composite material and is formed by the precipitation of metallic lithium within the pores of the silicon-carbon composite material. The pores are conducive to the lithium delithiation of the silicon-carbon composite material, thereby facilitating the improvement of the rate performance of the silicon-carbon composite material.
  • the silicon-carbon composite material includes silicon-carbon composite particles having a pore size of 100 nm to 1 ⁇ m, and the silicon-carbon composite particles account for less than 5% of the total number of particles in the silicon-carbon composite material.
  • the low proportion of silicon-carbon composite particles having such a pore size facilitates increasing the compaction density of the silicon-carbon composite material, thereby increasing the energy density of the secondary battery.
  • the silicon-carbon composite material includes a porous carbon substrate, a silicon material dispersed on the porous carbon substrate, and a carbon coating formed on the porous carbon substrate.
  • the porous carbon substrate serves as the skeleton of the silicon-carbon composite material, giving the silicon-carbon composite material good electrical conductivity and cyclic stability.
  • the porous carbon substrate, as a matrix for depositing the silicon material, can suppress the volume expansion of the silicon material during lithium insertion, thereby reducing expansion stress.
  • the particle size of the silicon material is less than 1 nm, which is beneficial for buffering the deformation stress of the silicon material during charge and discharge, thereby improving the cycle performance, expansion performance, and rate performance of the silicon-carbon composite material.
  • the sphericity of the silicon-carbon composite material is not less than 0.6, which is beneficial for increasing the compaction density of the silicon-carbon composite material, thereby improving the energy density of the secondary battery.
  • the carbon content of the silicon-carbon composite material is 40% to 70%, which is beneficial to improving the conductivity of the silicon-carbon composite material and making the silicon-carbon composite material have good cycle stability.
  • the silicon content of the silicon-carbon composite material is 20% to 60%, which is beneficial to improving the specific capacity of the silicon-carbon composite material.
  • the mass proportion of oxygen is 1% to 5%.
  • Li 2 O generated during the lithium insertion process of the silicon-carbon composite material can serve as a buffer substance to buffer the The volume expansion of silicon is beneficial to improving the cycle performance, expansion performance and rate performance of secondary batteries.
  • the silicon-carbon composite material has a particle size D V 50 of 5 ⁇ m to 10 ⁇ m, and a particle size D V 99 of 15 ⁇ m to 25 ⁇ m. This can reduce the risks of increased electrolyte consumption and low material compaction density, as well as the risks of low ionic conductivity and reduced rate performance.
  • the specific surface area of the silicon-carbon composite material is 1 m 2 /g to 50 m 2 /g, which is beneficial for reducing side reactions between the silicon-carbon composite material and the electrolyte and improving the initial coulombic efficiency and cycle performance of the silicon-carbon composite material.
  • the compaction density of the silicon-carbon composite material under a pressure of 5 tons is 1.05 g/cm 3 to 1.15 g/cm 3 , which is beneficial for increasing the compaction density of the negative electrode sheet, thereby improving the energy density of the secondary battery.
  • the silicon-carbon composite material has an initial delithiation specific capacity of 500 mAh/g to 2500 mAh/g, which is beneficial for improving the cycle performance, expansion performance, and rate performance of the secondary battery.
  • a second aspect of the present application provides a secondary battery, comprising a positive electrode plate, a negative electrode plate, and an electrolyte, wherein the negative electrode plate comprises a stacked negative electrode current collector and a negative electrode active layer, wherein the negative electrode active layer comprises a silicon-carbon composite material.
  • the pore size within the first region of the silicon-carbon composite material is smaller than the pore size within the second region, which can fully utilize the capacity contribution of silicon in the silicon-carbon composite material, thereby improving the specific capacity of the negative electrode plate.
  • the pore size within the first region is smaller than that in the second region, and can also reduce the SEI film formed by the electrolyte in the pores, thereby reducing the resistance to the deintercalation and intercalation of active ions in the first region, thereby improving the coulombic efficiency and specific capacity of the negative electrode plate, and further improving the specific capacity and coulombic efficiency of the secondary battery.
  • a third aspect of the present application provides an electronic device including a secondary battery.
  • the electronic device of the present application has a negative electrode plate with excellent specific capacity and coulombic efficiency in a secondary battery, which can improve the specific capacity and coulombic efficiency of the electronic device, thereby further improving the service life of the electronic device.
  • FIG1 is a schematic diagram of the particle slice structure of the silicon-carbon composite material prepared in Example 1.
  • Figure 2 is a schematic diagram of the particle slice structure of the silicon-carbon composite material prepared in Comparative Example 1 picture.
  • FIG3 is a scanning transmission electron microscope image of the first region in a particle slice of the silicon-carbon composite material prepared in Example 1.
  • FIG4 is a scanning transmission electron microscope image of the second region in the particle slice of the silicon-carbon composite material prepared in Example 1.
  • FIG5 is a differential capacity curve of the silicon-carbon composite material prepared in Example 1 during delithiation.
  • FIG6 is a SEM image of a cross section of the silicon-carbon composite material prepared in Example 1 under backscattered mode.
  • the present application provides a silicon-carbon composite material, a secondary battery, and an electronic device.
  • One embodiment of the present application provides a secondary battery, which includes a housing, an electrode assembly, and an electrolyte.
  • the electrode assembly and the electrolyte are both located in the housing.
  • the outer shell can be a packaging bag encapsulated by an encapsulation film (such as an aluminum-plastic film), such as a soft-pack battery.
  • an encapsulation film such as an aluminum-plastic film
  • the secondary battery can also be a steel-shell battery, an aluminum-shell battery, etc.
  • the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator.
  • the electrode assembly can be a laminated structure, formed by alternating positive electrode sheets, separators, and negative electrode sheets. In other embodiments, the electrode assembly can also be a wound structure, formed by stacking and winding the positive electrode sheets, separators, and negative electrode sheets.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on the negative electrode current collector.
  • the negative electrode current collector can be at least one of copper foil, nickel foil, stainless steel foil, titanium foil, or a carbon-based current collector. It can also be any composite current collector disclosed in the prior art, such as, but not limited to, a current collector formed by combining the aforementioned conductive foil and a polymer substrate.
  • the negative electrode active layer contains a negative electrode active material, which includes a silicon-carbon composite material.
  • the cross-section of the silicon-carbon composite material has a first region and a second region.
  • the first region is 2 ⁇ m radially inward from the edge of the cross-section of the silicon-carbon composite material
  • the second region is 4 ⁇ m radially outward from the center of the silicon-carbon composite material.
  • the pore size in the first region is smaller than the pore size in the second region.
  • the first region and the second region of the silicon-carbon composite material provided by the present application both have pores, and the pores can not only buffer the volume expansion of silicon and reduce the volume expansion of the silicon-carbon composite material, but also provide good electron and ion transmission channels, thereby improving the cycle performance, expansion performance and rate performance of the silicon-carbon composite material.
  • the capacity contribution of silicon in the silicon-carbon composite material can be fully utilized to obtain a silicon-carbon composite material with a high specific capacity; at the same time, the pore size in the first region is smaller, which can reduce the solid electrolyte film (SEI film) formed by the electrolyte in the pores, thereby improving the first coulombic efficiency and lithium removal specific capacity of the silicon-carbon composite material.
  • SEI film solid electrolyte film
  • the pore size of the first region is larger than that of the second region, that is, the pore size of the region near the center of the cut surface is smaller than the pore size of the region near the edge of the cut surface, the contact between the pores in the first region and the electrolyte increases, thereby forming an SEI film in the first region, increasing the resistance to active ion deintercalation and delithiation, and reducing the Coulombic efficiency and lithium deintercalation specific capacity of the silicon-carbon composite material.
  • the silicon-carbon composite material more silicon will be deposited in the second region, reducing the pore size in the second region. This will reduce the active ions embedded in the second region, thereby reducing the specific capacity of the silicon-carbon composite material.
  • the pore sizes of the first region and the second region can be determined by observing the pores on a cross-section of the silicon-carbon composite material.
  • the pores can be interconnected, forming channels that facilitate the transmission of electrons and ions.
  • the pore sizes of the first region and the second region are both in the nanometer range. Nano-sized pores are beneficial for reducing the volume of the silicon-carbon composite material, thereby facilitating To reduce the volumetric energy density.
  • the second region is a region 2 ⁇ m to 4 ⁇ m radially outward from the center of the silicon-carbon composite material, which enables the silicon-carbon composite material to have a better specific capacity while maintaining excellent cycle performance, expansion performance and rate performance.
  • the pore size in the first region is a, 1nm ⁇ a ⁇ 6nm.
  • the pores in the first region can promote the penetration of the electrolyte, shorten the diffusion distance of the active ions, and help improve the kinetics of lithium deintercalation of the silicon-carbon composite material, thereby helping to improve the specific capacity and first coulombic efficiency of the silicon-carbon composite material; at the same time, within the above pore size, it is also beneficial to appropriately increase the silicon content in the silicon-carbon composite material, thereby improving the specific capacity of the silicon-carbon composite material.
  • the pore size a in the first region can be 1nm, 1.5nm, 2nm, 2.5nm, 3nm, 3.5nm, 4nm, 4.5nm, 5nm, 5.5nm, 6nm or any value within the range formed by any two of the above values.
  • the pore size in the second region is b, 2nm ⁇ b ⁇ 8nm.
  • the pores in the second region are conducive to buffering the volume expansion of silicon, effectively improving the cycle performance and stability of the silicon-carbon composite material; at the same time, the pores in the second region can also serve as a spatial place for lithium precipitation, making it easier for the precipitated lithium to be delithiated, thereby improving the specific capacity and first coulombic efficiency of the silicon-carbon composite material. If the pore size b is large, the volume energy density of the silicon-carbon composite material will be reduced, and the structural stability of the silicon-carbon composite material will be reduced. If the pore size b is small, the specific capacity and first coulombic efficiency of the silicon-carbon composite material will be affected.
  • the pore size b in the second region can be 2nm, 2.5nm, 3nm, 3.5nm, 4nm, 4.5nm, 5nm, 5.5nm, 6nm, 6.5nm, 7nm, 7.5nm, 8nm or any value within the range formed by any two of the above values.
  • the differential capacity curve of the silicon-carbon composite material after delithiation has a characteristic peak at 600 mV to 750 mV.
  • the differential capacity-voltage curve of the delithiation of silicon-carbon composite materials can be understood as taking the charge-discharge specific capacity of the silicon-carbon composite material as the horizontal coordinate and the voltage as the vertical coordinate to obtain the charge-discharge curve of the silicon-carbon composite material, and then taking the first-order derivative of the delithiation specific capacity of the silicon-carbon composite material with respect to the voltage as the vertical coordinate and the voltage as the horizontal coordinate to obtain the differential capacity-voltage curve of the delithiation of the silicon-carbon composite material, as shown in Figure 5.
  • the differential capacity-voltage curve can reflect the capacity contained in the silicon-carbon composite material within the unit voltage range.
  • each characteristic peak represents an electrochemical reaction, and the peak height of each characteristic peak also indicates the effect of the reaction on the voltage. The contribution of electrochemical reaction to capacity.
  • the differential capacity curve of the silicon-carbon composite material for delithiation has a characteristic peak at 600mV to 750mV, indicating that the delithiation reaction of lithium precipitation in the silicon-carbon composite material is caused by the precipitation of metallic lithium in the pores in the silicon-carbon composite material.
  • the greater the characteristic peak height at 600mV to 750mV the greater the contribution of the lithium precipitation to the specific capacity of the silicon-carbon composite material, and the higher the content of the precipitated lithium.
  • the characteristic peak that appears at 600mV to 750mV illustrates that the precipitated lithium in the silicon-carbon composite material is precipitated from the pores, which can improve the rate performance of the silicon-carbon composite material, and on the other hand, it also illustrates that the silicon-carbon composite material contains nanopores. At the same time, the pores are beneficial to the delithiation of the silicon-carbon composite material, which can improve the specific capacity, cycle performance and rate performance of the silicon-carbon composite material.
  • the differential capacity curve of delithiation of silicon-carbon composite materials also has obvious characteristic peaks at 250mV to 300mV and 400mV to 450mV, respectively. It is generally believed that the characteristic peak from 250mV to 300mV represents the delithiation reaction of amorphous Li x Si, and the characteristic peak from 400mV to 450mV represents the delithiation reaction of crystalline Li 15 Si 4 in the silicon-carbon composite material.
  • the silicon-carbon composite material includes silicon-carbon composite particles having a pore size of 100 nm to 1 ⁇ m, and the number of silicon-carbon composite particles in the silicon-carbon composite material accounts for less than 5%, which is beneficial to increasing the compaction density of the silicon-carbon composite material, thereby facilitating increasing the energy density of the secondary battery. If the number of silicon-carbon composite particles in the silicon-carbon composite material accounts for more than 5%, the proportion of silicon-carbon composite particles is large, which reduces the compaction density in the silicon-carbon composite material and affects the energy density of the secondary battery.
  • the number of silicon-carbon composite particles in the silicon-carbon composite material can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or within the range of any of the above values.
  • the silicon-carbon composite material includes a porous carbon substrate, a silicon material dispersed on the porous carbon substrate, and a carbon coating formed on the porous carbon substrate.
  • the porous carbon substrate serves as the skeleton of the silicon-carbon composite material, which makes the silicon-carbon composite material have good electrical conductivity and cycle stability, and the porous carbon substrate serves as the matrix for the deposition of silicon material, which can inhibit the volume expansion of the silicon material during the lithium insertion process, thereby reducing the expansion stress.
  • the pore structure in the porous carbon substrate can also disperse the expansion stress of the silicon material, reduce the volume expansion rate of the silicon-carbon composite material, and further improve the cycle performance and expansion performance of the silicon-carbon composite material.
  • the first region closer to the edge of the cross section of the silicon-carbon composite material will form a silicon-rich region, and by controlling the distribution of the silicon material in the first region and the second region in the porous carbon substrate, the pore size in the first region and the second region can be regulated.
  • the carbon coating can reduce the silicon-carbon composite material.
  • the specific surface area of the material can be increased, the side reaction between the silicon-carbon composite material and the electrolyte can be reduced, and its first coulombic efficiency can be improved.
  • the conductivity of the silicon-carbon composite material can be further improved, which is conducive to further improving its rate performance.
  • the silicon material has a particle size of less than 1 nm, which helps buffer the deformation stress of the silicon material during charge and discharge, thereby improving the cycling performance, expansion performance, and rate performance of the silicon-carbon composite material.
  • the silicon material can have a particle size of 0.1 nm, 0.2 nm, 0.3 nm, 0.4 nm, 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1 nm, or any of the above values.
  • the sphericity of the silicon-carbon composite material is not less than 0.6, which is beneficial for increasing the compaction density of the silicon-carbon composite material, thereby improving the energy density of the secondary battery.
  • a smaller sphericity will affect the compaction density of the silicon-carbon composite material.
  • the sphericity of the silicon-carbon composite material can be 0.6, 0.7, 0.8, 0.9, 0.95, or any of the above values.
  • the carbon content of the silicon-carbon composite material is 40% to 70%, which is beneficial for improving the conductivity and specific capacity of the silicon-carbon composite material. However, if the carbon content is higher, the silicon content will be relatively reduced, which will reduce the specific capacity of the silicon-carbon composite material.
  • the silicon content of the silicon-carbon composite material is 20% to 60%, which is beneficial for improving the specific capacity of the silicon-carbon composite material. However, if the silicon content is higher, the carbon content will be relatively reduced, which will affect the cycling performance and expansion performance of the silicon-carbon composite material. By controlling the carbon content and silicon content within the above ranges, the specific capacity, cycling performance, and expansion performance of the silicon-carbon composite material can be further compatible.
  • the carbon content of the silicon-carbon composite material can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any range thereof.
  • the silicon content of the silicon-carbon composite material can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any range thereof.
  • the weight percentage of oxygen in the silicon-carbon composite material is 1% to 5% based on the weight of the silicon-carbon composite material.
  • Li2O generated during the lithium insertion process of the silicon-carbon composite material, can act as a buffer to mitigate the volume expansion of silicon, thereby improving the cycling performance, expansion performance, and rate performance of the secondary battery.
  • the weight percentage of oxygen in the silicon-carbon composite material can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any range thereof.
  • the particle size D V 50 of the silicon-carbon composite material is 5 ⁇ m to 10 ⁇ m, and the particle size D V 99 of the silicon-carbon composite material is 15 ⁇ m to 25 ⁇ m.
  • the silicon-carbon composite material can not only reduce the particle size of the silicon-carbon composite material, but also reduce the particle size of the silicon-carbon composite material.
  • the invention reduces the risks of larger specific surface area, increased electrolyte consumption, and low material compaction density caused by smaller particle size, and also prevents the problems of low ionic conductivity and poor rate performance caused by larger particle size.
  • the silicon-carbon composite material prepared from the silicon-carbon composite material can improve the uniform dispersion during the negative electrode slurry preparation process.
  • the particle size D V 50 of the silicon-carbon composite material can be 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, or any range thereof.
  • the particle size D V 99 of the silicon-carbon composite material can be 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m, 20 ⁇ m, 21 ⁇ m, 22 ⁇ m, 23 ⁇ m, 24 ⁇ m, 25 ⁇ m, or any range thereof.
  • DV50 also known as the "median particle size” represents the particle size at which the cumulative volume of the silicon-carbon composite particles, measured from the smallest particle size, reaches 50%, i.e., the volume of silicon-carbon composite particles smaller than this particle size accounts for 50% of the total volume of the silicon-carbon composite particles.
  • DV99 represents the particle size at which the cumulative volume of the silicon-carbon composite particles, measured from the smallest particle size, reaches 99%, in the volume-based particle size distribution.
  • the silicon-carbon composite material has a specific surface area of 1 m 2 /g to 50 m 2 /g, which is beneficial for reducing side reactions between the silicon-carbon composite material and the electrolyte and improving the initial coulombic efficiency and cycle performance of the silicon-carbon composite material.
  • the specific surface area of the silicon-carbon composite material can be 1 m 2 /g, 5 m 2 /g, 10 m 2 /g, 15 m 2 /g, 20 m 2 /g, 25 m 2 /g, 30 m 2 /g, 35 m 2 /g, 40 m 2 /g, 45 m 2 /g, 50 m 2 /g, or a range consisting of any two of the foregoing values.
  • the compaction density of the silicon-carbon composite material under a pressure of 5 tons is between 1.05 g/cm 3 and 1.15 g/cm 3 , which is beneficial for increasing the compaction density of the electrode sheet, thereby improving the energy density of the secondary battery.
  • the compaction density of the silicon-carbon composite material under a pressure of 5 tons can be 1.05 g/cm 3 , 1.06 g/cm 3 , 1.07 g/cm 3 , 1.08 g/cm 3 , 1.09 g/cm 3 , 1.10 g/cm 3 , 1.11 g/cm 3 , 1.12 g/cm 3 , 1.13 g/cm 3 , 1.14 g/cm 3 , 1.15 g/cm 3 , or a range consisting of any two of the foregoing values.
  • the first delithiation specific capacity of the silicon-carbon composite material is 500mAh/g to 2500mAh/g. Within the above range, it is beneficial to improve the cycle performance, expansion performance and rate performance of the secondary battery.
  • the first delithiation specific capacity of the silicon-carbon composite material can be 500mAh/g, 600mAh/g, 700mAh/g, 800mAh/g, 900mAh/g, 1000mAh/g, 1100mAh/g, 1200mAh/g, 1300mAh/g, 1400mAh/g, 1500mAh/g, 1600mAh/g, 1700mAh/g, 1800mAh/g, 1900mAh/g, 2000mAh/g, 2100mAh/g, 2200mAh/g, 2300mAh/g, 2400mAh/g, 2500mAh/g or a range consisting of any of the above values.
  • the preparation method of the above-mentioned silicon-carbon composite material includes:
  • a porous carbon substrate is provided.
  • the porous carbon substrate can be selected from at least one of activated carbon, template porous carbon, carbon molecular sieve, carbon nanofiber, carbon nanotube, expanded graphite, etc.
  • the activated carbon is obtained by activating biochar, resin carbon, coke, etc.
  • Silicon source gas is introduced into the porous carbon substrate by vapor deposition to deposit elemental silicon in the porous carbon substrate.
  • the silicon source gas may include, but is not limited to, one or more of monosilane, disilane, trisilane, tetrasilane, chlorosilane, dichlorosilane, trichlorosilane, or tetrachlorosilane.
  • the silicon source gas and an inert gas are simultaneously introduced into the porous carbon substrate to dilute the silicon source gas and allow the silicon source gas to fully react with the porous carbon substrate.
  • the present application changes the pore sizes in the first region and the second region of the silicon-carbon composite material by regulating the flow rate, time and pyrolysis temperature of the silicon source gas during the silicon material deposition process.
  • the temperature of the pyrolysis of the silicon source gas is 460°C ⁇ 500°C
  • the flow rate of the silicon source gas is 1 ⁇ 5L/min
  • the time of the monosilane introduction is 5 ⁇ 10h.
  • the pore size in the first region and the second region of the silicon-carbon composite material is controlled.
  • the temperature of the pyrolysis of the silicon source gas can be 460°C, 470°C, 480°C, 490°C, 500°C or any value within the range of any of the above numerical values.
  • the flow rate of the silicon source gas can be 1L/min, 2L/min, 3L/min, 4L/min, 5L/min or any value within the range of any of the above numerical values.
  • the time of the monosilane introduction can be 5h, 6h, 7h, 8h, 9h, 10h or any value within the range of any of the above numerical values.
  • increasing the pyrolysis temperature of the silicon source gas increases the deposition rate of the silicon source gas, resulting in larger pore sizes in the second region and smaller pore sizes in the first region. This affects the deintercalation of active ions and is detrimental to controlling the pore sizes in the first and second regions.
  • Lowering the pyrolysis temperature of the silicon source gas decreases the deposition rate of the silicon source gas, hindering deposition.
  • the silicon source gas flow rate if the silicon source gas flow rate is increased, more silicon source gas enters and is deposited in the second region, significantly reducing the pore size in the second region, thereby deteriorating the specific capacity and initial coulombic efficiency of the silicon-carbon composite material. If the silicon source gas flow rate is decreased, more silicon source gas enters and is deposited in the first region, reducing the pore size in the first region, hindering the deintercalation of active ions and reducing the specific capacity of the silicon-carbon composite material.
  • a carbon source gas is introduced into the porous carbon substrate on which elemental silicon is deposited, so as to deposit a carbon material on the porous carbon substrate to form a carbon coating layer.
  • a carbon coating layer is formed on the porous carbon substrate by the deposition of carbon source gas.
  • the carbon coating layer can reduce the specific surface area of the silicon-carbon composite material, reduce the side reaction between the silicon-carbon composite material and the electrolyte, and improve its first coulombic efficiency. On the other hand, it can further improve the conductivity of the silicon-carbon composite material, which is conducive to further improving its rate performance.
  • the carbon source gas may include, but is not limited to, one or more of methane, acetylene, ethylene, ethane, propyne, propylene, propane, butyne, butene, or butane.
  • the negative electrode active layer also includes a binder to bind the negative electrode active material particles to facilitate film formation and improve the bonding strength between the negative electrode active layer and the negative electrode current collector.
  • the binder may include, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon.
  • the negative electrode active layer may further comprise a conductive material, including but not limited to carbon-based materials, metal-based materials, conductive polymers, or any combination thereof.
  • the carbon-based material may include, but is not limited to, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof.
  • the metal-based material may include, but is not limited to, metal powder or metal fiber, such as copper, nickel, aluminum, or silver.
  • the conductive polymer may be a polyphenylene derivative.
  • the negative electrode active layer can further include graphite. Because graphite has a certain degree of flexibility, its combination with the silicon-carbon composite material can mitigate the overall volume expansion of the negative electrode active layer. Furthermore, using both graphite and the silicon-carbon composite as negative electrode active materials can fully utilize the advantages of both the silicon-carbon composite and graphite to achieve better electrochemical performance.
  • the mass proportion of graphite in the negative electrode active layer is 35 wt.% to 95 wt.%, and the obtained negative electrode active layer meets at least one of the following conditions: (1) the particle size D V 50 of the negative electrode active layer is 5 ⁇ m to 15 ⁇ m, and the D V 99 is 15 ⁇ m to 40 ⁇ m; (2) the specific surface area of the negative electrode active layer is 1 m 2 /g to 10 m 2 /g; (3) the compaction density of the negative electrode active layer is 1.35 g/cm 3 to 1.8 g/cm 3 ; (4) the first delithiation specific capacity of the negative electrode active layer is 400 mAh/g to 1000 mAh/g.
  • the mass proportion of graphite is within the above range, which can further improve the cycle performance of the negative electrode active layer, thereby improving the cycle performance of the secondary battery.
  • Controlling the overall particle size, specific surface area, powder compaction density and first delithiation specific capacity of the negative electrode active layer within the above ranges can further improve the energy density, first coulombic efficiency, cycle performance and rate performance of the secondary battery.
  • the separator includes a porous membrane layer, and its material includes, but is not limited to, at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid.
  • the separator can be a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane.
  • the electrolyte may be in one or more of a gel state, a solid state, and a liquid state.
  • the liquid electrolyte comprises a lithium salt and an organic solvent.
  • the lithium salt may be selected from, but is not limited to, one or more of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium perchlorate (LiClO 4 ), lithium tetraphenylborate (LiB(C 6 H 5 ) 4 ), lithium methanesulfonate (LiCH 3 SO 3 ), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bis(trifluoromethylsulfonyl)imide
  • the lithium salt may be selected from LiPF 6
  • the organic solvent may be a carbonate compound, a carboxylate compound, an ether compound, a nitrile compound, another organic solvent, or a combination thereof.
  • carbonate compounds include, but are not limited to, diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC), butylene carbonate (BC), vinylethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluor
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer disposed on the positive electrode current collector.
  • the positive electrode current collector can be made of aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as, but not limited to, a current collector formed by combining the aforementioned conductive foil and a polymer substrate.
  • the positive electrode active layer contains a positive electrode active material, which includes a compound that reversibly intercalates and deintercalates lithium ions (i.e., a lithiated intercalation compound).
  • the positive electrode active material may include a lithium transition metal composite oxide.
  • the lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese, and nickel.
  • the positive electrode active material may include, but is not limited to, at least one of lithium cobalt oxide (LiCoO 2 ), lithium nickel manganese cobalt ternary material (NCM), lithium manganese oxide (LiMn 2 O 4 ), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O 4 ), or lithium iron phosphate (LiFePO 4 ).
  • LiCoO 2 lithium cobalt oxide
  • NCM lithium nickel manganese cobalt ternary material
  • LiMn 2 O 4 lithium manganese oxide
  • LiNi 0.5 Mn 1.5 O 4 lithium iron phosphate
  • LiFePO 4 lithium iron phosphate
  • the positive electrode active layer also includes a binder to bond the positive electrode active material particles to facilitate film formation and improve the bonding strength between the positive electrode active layer and the positive electrode current collector.
  • the binder may include, but is not limited to, at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon.
  • the positive electrode active layer may further comprise a conductive material, including but not limited to carbon-based materials, metal-based materials, conductive polymers, or any combination thereof.
  • the carbon-based material may include, but is not limited to, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof.
  • the metal-based material may include, but is not limited to, metal powder or metal fiber, such as copper, nickel, aluminum, or silver.
  • the conductive polymer may be a polyphenylene derivative.
  • the secondary battery is applied to an electronic device to power a load in the electronic device.
  • the silicon-carbon composite material in the secondary battery has excellent cycle performance, expansion performance and rate performance, which is beneficial to improving the service life of the electronic device.
  • the electronic device may include but is not limited to a laptop computer, a pen-input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD TV, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery and a lithium
  • a porous carbon substrate (the specific surface area of the porous carbon substrate is 2000 m 2 /g, The porous carbon substrate (with a pore volume of 0.9 cm 3 /g and a micropore ratio of 99%) was vacuum dried at 70°C. 1000 g of the dried porous carbon substrate was placed in a fluidized bed reaction vessel. The porous carbon material was heated to 480°C under a protective atmosphere of 99.999% pure nitrogen. Monosilane gas with a flow rate of 2 L/min and a concentration of 100% was introduced using 18 L/min of 99.999% pure nitrogen as a diluent. The reaction was continued for 6 hours, causing the monosilane to be adsorbed and deposited in the pores of the porous carbon substrate to form elemental silicon.
  • Example 2 The difference between Examples 2 to 6 and Comparative Examples 1 to 5 and Example 1 lies in the adjustment of the monosilane pyrolysis temperature, monosilane flow rate, and monosilane introduction time. Except for adjusting the relevant preparation parameters according to Table 1, the rest are the same as Example 1.
  • Micron silicon powder sieved through 400 meshes and pre-treated for demagnetization was mixed with graphite in a mass ratio of 45:55, and ground under an inert atmosphere to obtain a silicon-carbon composite material.
  • a schematic diagram of the particle slice structure of the silicon-carbon composite material prepared in Example 1 is shown in Figure 1.
  • the pore size of the first region (i.e., region I) in Figure 1 is smaller than the pore size of the second region (i.e., region II).
  • a schematic diagram of the particle slice structure of the silicon-carbon composite material prepared in Comparative Example 1 is shown in Figure 2.
  • the pore size of the second region (i.e., region II) in Figure 2 is smaller than the pore size of the first region (i.e., region I).
  • the silicon-carbon composite materials prepared in Examples 1 to 6 and Comparative Examples 1 to 6 were tested for silicon grain size, sphericity, carbon/silicon content, D V 50/D V 99, specific surface area, compacted density, and oxygen content.
  • the test data are recorded in Table 2.
  • the silicon-carbon composite material was sliced with the help of FIB (focused ion beam), and then tested using a field FEI Talos F200S high-resolution transmission electron microscope at a voltage of 200 kV and a current of 100 nA.
  • the silicon-carbon composite material was divided into a first area and a second area to measure the pore sizes in the first area and the second area, respectively.
  • K is the Scherrer constant
  • D is the size of the silicon crystallite
  • B is the measured sample.
  • the diffraction peak half-width, ⁇ is the Bragg diffraction angle, and ⁇ is the X-ray wavelength.
  • the silicon-carbon composite material to be tested was polished by an IB-09010CP/ion polisher (voltage of 6kV), and then the silicon-carbon composite material was tested using a JEOL-JSM-6700F scanning electron microscope at a voltage of 5kV and a current of 0.8nA in backscattered mode to obtain a scanning electron microscope image of the cross section of the silicon-carbon composite material in backscattered mode. It was measured using the British lattice code SHAPE industrial image analysis and processing software.
  • Sphericity is the ratio of the surface area of a sphere of the same volume as the object to the surface area of the object. It is a parameter that characterizes the morphology of the particle. The closer the particle is to a sphere in morphology, the closer its sphericity is to 1.
  • the calculation formula for the sphericity of any particle is:
  • Vp is the particle volume and Sp is the particle surface area.
  • the silicon-carbon composite material was first polished using an IB-09010CP/ion polisher (voltage of 6 kV) and then tested using a JEOL-JSM-6700F scanning electron microscope at a voltage of 5 kV and a current of 0.8 nA in backscattered mode.
  • 0.02 g of the powder sample of the silicon-carbon composite material in each embodiment and comparative example was added to a 50 ml clean beaker, 20 ml of deionized water was added, and a surfactant was added dropwise to completely disperse the powder sample in the water.
  • the sample was ultrasonically cleaned in a 120 W ultrasonic cleaner for 5 min.
  • the silicon-carbon composite material was tested using a MasterSizer 2000 device at a detection angle of 0° to 135°.
  • the particle size distribution was measured according to the particle size distribution laser diffraction method GB/T19077-2016 to obtain the D V 50 and D V 99 values of the silicon-carbon composite material.
  • the BET specific surface area of silicon-carbon composite materials was tested using TriStarII3020 equipment. The test was carried out in accordance with the national standard GB/T 19587-2017 "Determination of Specific Surface Area of Solid Substances by Gas Adsorption BET Method". Specifically, the silicon-carbon composite material was taken as a sample, and the sample tube was immersed in liquid nitrogen at -196°C. The adsorption amount of nitrogen on the solid surface at different pressures was measured at a relative pressure of 0.05 to 0.30. Based on the BET multilayer adsorption theory, the adsorption amount of nitrogen on the solid surface was measured. The monolayer adsorption capacity of the sample is obtained by the theory and formula, and the specific surface area of the solid is calculated.
  • the oxygen content of silicon-carbon composite materials was tested using a German Elementar element analyzer.
  • the compaction density of silicon-carbon composite materials was tested using the Sansi Zongheng UTM7305 battery powder compaction density instrument under a pressure of 5 tons.
  • the differential capacity curve of the silicon-carbon composite material prepared in Example 1 during lithium removal is shown in Figure 5. As can be seen from Figure 5, the differential capacity curve has obvious characteristic peaks at 250mV to 300mV, 400mV to 450mV, and 600mV to 750mV.
  • the preparation process of button half-cell includes:
  • Preparation process of negative electrode The silicon-carbon composite material, acetylene black and sodium alginate binder prepared in the above embodiment are added to deionized water in a mass ratio of 80:10:10, and stirred thoroughly to form a slurry. A coating with a thickness of 100 ⁇ m is applied using a scraper. After drying in a vacuum drying oven at 85°C for 12 hours, the coating is cut into discs with a diameter of 1 cm using a punch in a dry environment to obtain negative electrode.
  • Electrolyte and separator In an argon-filled glove box (moisture ⁇ 10ppm, oxygen ⁇ 1ppm), ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed in a 1:1 volume ratio to obtain a mixed solution. 1 mol/L LiPF6 and 5 vol.% fluoroethylene carbonate (FEC) were added to the mixed solution and stirred to obtain the electrolyte. Celgard 2400 separator was used as the separator.
  • the above-mentioned negative electrode sheet is used as a counter electrode with a lithium sheet as the counter electrode.
  • a button half-cell is assembled in a glove box with the lithium sheet as the counter electrode.
  • buttons assembled with the silicon-carbon composite materials prepared in Examples 1 to 6 and Comparative Examples 1 to 6 were tested for the initial delithiation specific capacity, initial coulombic efficiency, capacity retention, rate performance, and expansion rate.
  • the specific test methods are as follows:
  • test methods for the first delithiation specific capacity and the first coulombic efficiency include:
  • the assembled button-type half-cells were subjected to charge and discharge tests on a LAND CT2001A battery test system.
  • the half-cell tests employed an operating voltage range of 0.01V to 2.0V.
  • the cells were discharged at a constant current of 0.1C to 0.01V, allowed to rest for 5 minutes, then discharged at a constant current of 50 ⁇ A to 0.01V, allowed to rest for 5 minutes, and then charged at a constant current of 0.1C to 2.0V, allowed to rest for 5 minutes.
  • the initial discharge and charge capacities of the button-type half-cells were recorded as the initial lithium insertion and removal specific capacities, respectively.
  • First coulombic efficiency (%) (first lithium removal capacity/first lithium insertion capacity) ⁇ 100%.
  • the first-order derivative of the delithiation specific capacity of the silicon-carbon composite material with respect to the voltage is taken as the ordinate and the voltage is taken as the abscissa, so as to obtain the differential capacity-voltage curve of the silicon-carbon composite material when delithiation occurs.
  • the test method for the capacity retention rate (%) after 50 cycles of half-battery includes:
  • the assembled button half-cell was discharged at 0.5C constant current to 0.01V at 25°C, allowed to rest for 5 minutes, then discharged at 50 ⁇ A constant current to 0.01V, allowed to rest for 5 minutes, and then charged at 0.5C constant current to 2.0V, allowed to rest for 5 minutes.
  • the discharge capacity of the first cycle was recorded.
  • the same charge and discharge procedure was then repeated for 50 cycles, and the discharge capacity at the 50th cycle was recorded.
  • Capacity retention rate of half-cell after 50 cycles (%) (discharge capacity at the 50th cycle/discharge capacity at the first cycle) ⁇ 100%.
  • test methods for the rate performance of half-cells include:
  • the button half-cell assembled above was subjected to rate testing on a LAND CT2001A battery test system.
  • the test used an operating voltage range of 0.01V to 2V, discharged at a constant current of 0.5C to 0.01V, allowed to stand for 5 minutes, and then charged at a constant current of 0.5C to 2.0V, allowed to stand for 5 minutes.
  • the charging capacity of the button half-cell was recorded as the delithiation capacity at 0.5C.
  • tests were performed at 1.0C, 2.0C, and 5.0C according to the above process, and the delithiation capacity of the half-cell at 1.0C, 2.0C, and 5.0C was obtained respectively.
  • the rate performance of the silicon-carbon composite material can be judged.
  • the test methods for the thickness expansion rate of the negative electrode include:
  • the button-type half-cells assembled above were disassembled before and after 50 cycles, and the negative electrode sheets were obtained.
  • the pore size a of the first region in the silicon-carbon composite materials of Examples 1 to 6 is smaller than the pore size b of the second region. Therefore, when the silicon-carbon composite materials have excellent specific capacity, they can also take into account good first coulombic efficiency, cycle performance, rate performance and expansion performance.
  • the silane pyrolysis temperature, the silane flow rate, and the silane introduction time are relatively changed so that the pore size of the first region in the silicon-carbon composite material is smaller than the pore size of the second region.
  • Comparative Examples 1 to 2 by increasing the silane pyrolysis temperature and the silane flow rate, more silicon enters the second region and is deposited and formed in the second region, reducing the pore size in the second region, so that the pore size of the first region is larger than the pore size in the second region, more silicon is located in the second region, reducing the contact with the electrolyte, and is not conducive to the contribution of silicon in the second region of the silicon-carbon composite material.
  • the silane pyrolysis temperature and the silane flow rate are increased relative to Examples 1 to 2, but the silane introduction time is reduced.
  • the pore size of the first region is larger than the pore size in the second region, its specific capacity decreases, and the first coulombic efficiency, cycle performance, rate performance, and expansion performance of its silicon-carbon composite material are all reduced.
  • the silane pyrolysis temperature, the silane flow rate, and the silane introduction time were adjusted to obtain a pore size in the second region of the silicon-carbon composite material that is less than or equal to the pore size in the first region.
  • the pore sizes in the first and second regions of the silicon-carbon composite material are approximately the same, and compared with the embodiment, the first delithiation specific capacity and the first coulombic efficiency are reduced. This may be because the pores in the first region are relatively large, and the electrolyte forms more SEI films in the pores, consuming more lithium ions, thereby reducing the first coulombic efficiency and specific capacity of the silicon-carbon composite material.
  • Comparative Examples 4 and 5 compared with Examples 1 and 2, although the flow rate of monosilane is increased, the temperature of monosilane is reduced, the silicon deposition rate is reduced, and more silicon is deposited in the second region, so that the pore size of the second region is smaller than that of the first region.
  • the specific capacity and first coulombic efficiency of the silicon-carbon composite material have decreased, which may be due to the larger pores in the first region and the more SEI films formed, resulting in a lower specific capacity and first coulombic efficiency of the silicon-carbon composite material.
  • the differential capacity curve of the silicon-carbon composite material prepared in Comparative Example 6 for lithium removal does not show a characteristic peak at 600mV to 750mV, and the silicon-carbon composite material prepared in Comparative Example 6 does not contain nanopores.
  • the silicon-carbon composite material prepared in Comparative Example 6 has a good specific capacity, but its first coulombic efficiency, cycle performance, rate capability and expansion performance are all reduced. This also shows that in the silicon-carbon composite material, the presence of nanopores can buffer the volume expansion of silicon, thereby improving the cycle performance, expansion performance and rate performance of the silicon-carbon composite material.
  • the silicon-carbon composite material when the pore size in the first region is smaller than the pore size in the second region, the silicon-carbon composite material also has excellent specific capacity and first coulombic efficiency.
  • the proportion of silicon-carbon composite particles in Examples 1 to 6 is within a suitable range, and the proportion of silicon-carbon composite particles with a pore size of 100nm to 1 ⁇ m is small, which is beneficial to increase the compaction density of the silicon-carbon composite material, thereby facilitating the improvement of the energy density of the secondary battery.
  • the sphericity of the silicon-carbon composite materials in Examples 1 to 6 is greater than 0.6, and the compaction density of the silicon-carbon composite materials is improved.
  • the carbon, silicon, and oxygen content, specific surface area, and compaction density of the silicon-carbon composite materials in Examples 1 to 6 are all within appropriate ranges, which is conducive to improving the cycle performance, rate performance, and expansion performance of the silicon-carbon composite materials.
  • the silicon grain size in the silicon-carbon composite materials in Comparative Examples 1 and 2 was greater than 1 nm. Compared with the examples, the initial delithiation specific capacity, initial coulombic efficiency, capacity retention rate, and rate performance of Comparative Examples 1 and 2 decreased, while the expansion rate increased slightly. This indicates that the silicon grain size in the silicon-carbon composite material is less than 1 nm, which is beneficial for improving the cycle performance, rate performance, and expansion performance of the silicon-carbon composite material.

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Abstract

一种硅碳复合材料、二次电池及电子装置，硅碳复合材料的切面具有第一区域和第二区域，第一区域为硅碳复合材料的切面边缘沿径向方向向内2μm的区域，第二区域为以硅碳复合材料材料的中心沿径向方向向外4μm的区域；第一区域内的孔隙尺寸小于第二区域内的孔隙尺寸。硅碳复合材料在具有较高比容量时，还具有良好的首次库伦效率、循环性能、倍率性能和膨胀性能。

Description

硅碳复合材料、二次电池及电子装置 技术领域
本申请涉及电化学储能领域，尤其是涉及一种硅碳复合材料、应用所述硅碳复合材料的二次电池以及包含二次电池的电子装置。
背景技术
石墨是应用最广泛的负极材料，其具有效率高，充放电平台稳定等优势，然而，较低的克容量阻碍了石墨的进一步应用。和石墨相比，单质硅由于较高的理论比容量和合适的工作电压等特点，被认为是可以替代石墨的理想负极材料。
然而，硅作为一种半导体材料，较低的导电性以及在合金化/去合金化过程中会发生巨大的体积膨胀，严重制约了单质硅在锂离子电池中的大规模应用。
发明内容
因此，本申请提供一种硅碳复合材料，还提供一种应用硅碳复合材料的二次电池以及包含二次电池的电子装置。
本申请第一方面提供一种硅碳复合材料，硅碳复合材料的切面具有第一区域和第二区域，第一区域为硅碳复合材料的切面边缘沿径向方向向内2μm的区域，第二区域为以硅碳复合材料材料的中心沿径向方向向外4μm的区域。第一区域内的孔隙尺寸小于第二区域内的孔隙尺寸。
本申请中，硅碳复合材料中的第一区域和第二区域均存在孔隙，孔隙不仅可以缓冲硅的体积膨胀，降低硅碳复合材料的体积膨胀，且还可以提供良好的电子和离子传输通道，改善硅碳复合材料的循环性能、膨胀性能和倍率性能。且第一区域的孔隙尺寸小于第二区域的孔隙尺寸，能够充分发挥硅碳复合材料中硅的容量贡献，以得到具有高比容量的硅碳复合材料。同时，第一区域内的孔隙尺寸更小，可以减少电解液在孔隙中形成的固体电解质膜(SEI膜)，提高硅碳复合材料的首次库伦效率和脱锂比容量。
基于第一方面，在一些可能的实施方式中，第一区域内的孔隙尺寸为a，1nm≤a≤6nm。利于提高硅碳复合材料的脱嵌锂的动力学，从而利于提高硅碳复合材料的比容量和首次库伦效率。第二区域内的孔隙尺寸为b，2nm≤b≤8nm，利于提高硅碳复合材料的比容量、首次库伦效率以及循环性能。
基于第一方面，在一些可能的实施方式中，硅碳复合材料脱锂的差分容量曲线在600mV至750mV具有特征峰。此特征峰表示硅碳复合材料中发生的脱锂反应，是由金属锂在硅碳复合材料中的孔隙内析出形成的，孔隙利于硅碳复合材料脱锂，从而有利于提高硅碳复合材料的倍率性能。
基于第一方面，在一些可能的实施方式中，硅碳复合材料包括具有孔径为100nm至1μm的硅碳复合颗粒，硅碳复合颗粒在硅碳复合材料中的颗粒数量占比小于5％。具有上述孔径的硅碳复合颗粒占比少，利于提高硅碳复合材料的压实密度，从而提高二次电池的能量密度。
基于第一方面，在一些可能的实施方式中，硅碳复合材料包括多孔碳基材、分散于多孔碳基材上的硅材料、以及形成于多孔碳基材上的碳包覆层。多孔碳基材作为硅碳复合材料的骨架，使得硅碳复合材料具有良好的导电性和循环稳定性，且多孔碳基材作为硅材料沉积的基体，可以抑制硅材料在嵌锂过程中的体积膨胀，从而减少膨胀应力。
基于第一方面，在一些可能的实施方式中，硅材料的粒径小于1nm。有利于缓冲充放电过程中硅材料的形变应力，从而提升硅碳复合材料的循环性能、膨胀性能和倍率性能。
基于第一方面，在一些可能的实施方式中，硅碳复合材料的球形度不低于0.6。有利于提高硅碳复合材料的压实密度，从而提升二次电池的能量密度。
基于第一方面，在一些可能的实施方式中，基于硅碳复合材料的质量，硅碳复合材料中碳元素的含量为40％至70％，利于提高硅碳复合材料的导电性，使得硅碳复合材料具有良好的循环稳定性。硅碳复合材料中硅元素的含量为20％至60％，有利于提升硅碳复合材料的比容量。
基于第一方面，在一些可能的实施方式中，基于硅碳复合材料的质量，氧元素的质量占比为1％至5％。可以在硅碳复合材料的嵌锂过程中生成的Li2O，Li2O可以作为缓冲物质，能够缓冲 硅的体积膨胀，有利于提高二次电池的循环性能、膨胀性能和倍率性能。
基于第一方面，在一些可能的实施方式中，硅碳复合材料的粒径DV50为5μm至10μm，粒径DV99为15μm至25μ。可以减少电解液消耗量增多以及材料压实密度低的风险，而且还可以减少离子电导率低、倍率性能降低的风险。
基于第一方面，在一些可能的实施方式中，硅碳复合材料的比表面积为1m2/g至50m2/g。有利于降低硅碳复合材料与电解液发生的副反应，改善硅碳复合材料的首次库伦效率和循环性能。
基于第一方面，在一些可能的实施方式中，硅碳复合材料在5吨压力下的压实密度为1.05g/cm3至1.15g/cm3。有利于提高负极极片的压实密度，从而提升二次电池的能量密度。
基于第一方面，在一些可能的实施方式中，硅碳复合材料的首次脱锂比容量500mAh/g至2500mAh/g。有利于提高二次电池的循环性能、膨胀性能和倍率性能。
本申请第二方面提供一种二次电池，二次电池包括正极极片、负极极片和电解液，负极极片包括层叠设置的负极集流体以及负极活性层，负极活性层包括硅碳复合材料。本申请的负极极片，硅碳复合材料中的第一区域内的孔隙尺寸小于第二区域内的孔隙尺寸，能够充分发挥硅碳复合材料中硅的容量贡献，从而提高负极极片的比容量，且相较于第二区域，第一区域内的孔隙尺寸更小，还可以减少电解液在孔内形成的S EI膜，从而减小活性离子在第一区域内脱嵌的阻力，从而提高负极极片的库伦效率和比容量，进而可以提高二次电池的比容量和库伦效率。
本申请第三方面提供一种电子装置，包括二次电池。
本申请的电子装置，在二次电池中具有比容量和库伦效率优异的负极极片，可以提高电子装置的比容量和库伦效率，以进一步提高电子装置的使用寿命。
附图说明
本申请的上述和/或附加的方面和优点从结合下面附图对实施例的描述中将变得明显和容易理解，其中：
图1为实施例1制备的硅碳复合材料的颗粒切片结构示意图。
图2为对比例1制备的硅碳复合材料的颗粒切片结构示意 图。
图3为实施例1制备的硅碳复合材料的颗粒切片中第一区域的扫描透射电子显微镜图。
图4为实施例1制备的硅碳复合材料的颗粒切片中第二区域的扫描透射电子显微镜图。
图5为实施例1制备的硅碳复合材料脱锂时的差分容量曲线图。
图6为实施例1制备的硅碳复合材料的横切面在背散模式下的SEM图。
具体实施方式
下面对本申请实施例中的技术方案进行清楚、详细地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。在本申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请。
相关技术中，为了缓冲单质硅的体积膨胀，可采用硅纳米化、多孔硅以及引入过渡金属氧化物等方法，但是硅纳米化、多孔硅的高比表面积、低振实密度限制了它们的大规模应用，过渡金属氧化物的引入虽然也可以降低硅的体积膨胀，但是由于金属氧化物的机械性能和化学稳定性并不突出，因而也不是良好的缓冲介质。碳材料作为负极材料虽然比容量小，但由于价格低廉、导电性好、化学和热稳定性突出等优点，可作为硅基材料良好的导电介质和缓冲基体。因此，通过将硅基材料和碳材料结合制备低体积膨胀的硅碳复合材料，但是硅碳复合材料的循环性能、膨胀性能和倍率性能还有待提升。
鉴于以上问题，本申请中提供了一种硅碳复合材料、二次电池以及电子装置。
本申请一实施方式提供一种二次电池，其包括外壳、电极组件和电解液。电极组件和电解液均位于外壳内。
外壳可以是采用封装膜(如铝塑膜)封装得到的包装袋，如二次电池为软包电池。在另一些实施例中，二次电池也可以是钢壳电池、铝壳电池等。
电极组件包括正极极片、负极极片和隔离膜，隔离膜设于正 极极片和负极极片之间。电极组件可以是叠片式结构，其由正极极片、隔离膜和负极极片交替层叠形成。在另一些实施例中，电极组件还可以是卷绕结构，其由正极极片、隔离膜和负极极片层叠后卷绕形成。
负极极片
负极极片包括负极集流体和设于负极集流体上的负极活性层。负极集流体可以使用铜箔、镍箔、不锈钢箔、钛箔或碳基集流体等中的至少一种，也可为任何现有技术中公开的复合集流体，例如但不仅限于前述导电箔和聚合物基底结合形成的集流体。负极活性层包含负极活性材料，负极活性材料包括硅碳复合材料。
硅碳复合材料的切面具有第一区域和第二区域，第一区域为硅碳复合材料的切面边缘沿径向方向向内2μm的区域，第二区域为以硅碳复合材料材料的中心沿径向方向向外4μm的区域。第一区域内的孔隙尺寸小于第二区域内的孔隙尺寸。
本申请提供的硅碳复合材料中的第一区域和第二区域均存在孔隙，孔隙不仅可以缓冲硅的体积膨胀，降低硅碳复合材料的体积膨胀，且还可以提供良好的电子和离子传输通道，改善硅碳复合材料的循环性能、膨胀性能和倍率性能。当第一区域内的孔隙尺寸小于第二区域内的孔隙尺寸时，能够充分发挥硅碳复合材料中硅的容量贡献，以得到具有高比容量的硅碳复合材料；同时，第一区域内的孔隙尺寸更小，可以减少电解液在孔隙中形成的固体电解质膜(SEI膜)，提高硅碳复合材料的首次库伦效率和脱锂比容量。
若第一区域的孔隙尺寸大于第二区域的孔隙尺寸，也即切面上靠近中心的区域的孔隙尺寸小于靠近切面边缘的区域的孔隙尺寸，增加了第一区域内孔隙与电解液接触以在第一区域内形成的SEI膜，增加了活性离子脱嵌的阻力，降低了硅碳复合材料的库伦效率和脱锂比容量。在硅碳复合材料中更多的硅会沉积于第二区域内，减小第二区域内的孔隙尺寸，如此，会减少嵌入第二区域内的活性离子，从而降低硅碳复合材料的比容量。
其中，第一区域和第二区域的孔隙尺寸，具体可以通过观察硅碳复合材料切面上的孔隙。硅碳复合材料中，孔隙之间可以是相互连通的，形成了利于电子和离子传输的通道。
在一些实施例中，第一区域和第二区域的孔隙尺寸均在纳米范围内。纳米尺寸的孔隙利于减小硅碳复合材料的体积，从而利 于减小体积能量密度的降低。
在一些实施例中，第二区域为以硅碳复合材料材料的中心沿径向方向向外2μm至4μm的区域，可使得硅碳复合材料具有较好比容量的同时，还保持优异的循环性能、膨胀性能和倍率性能。
在一些实施例中，第一区域内的孔隙尺寸为a，1nm≤a≤6nm。第一区域内的孔隙可促进电解液的渗透，缩短活性离子的扩散距离，利于提高硅碳复合材料的脱嵌锂的动力学，从而利于提高硅碳复合材料的比容量和首次库伦效率；同时，在上述孔隙尺寸内，还利于适当增加硅碳复合材料中硅的含量，从而提高硅碳复合材料的比容量。若孔隙尺寸a较大，会增加与电解液的接触面积，不利于提高硅碳复合材料的比容量；若孔隙尺寸a较小，则会影响活性离子的脱嵌。例如，第一区域内的孔隙尺寸a可以为1nm、1.5nm、2nm、2.5nm、3nm、3.5nm、4nm、4.5nm、5nm、5.5nm、6nm或在上述任意两个数值所组成的范围内的任一值。
在一些实施例中，第二区域内的孔隙尺寸为b，2nm≤b≤8nm。第二区域内的孔隙利于缓冲硅的体积膨胀，有效地提高硅碳复合材料的循环性能和稳定性；同时，第二区域内的孔隙也可以作为锂析出的空间场所，析出锂更易脱锂，提高硅碳复合材料的比容量和首次库伦效率。若孔隙尺寸b较大，会减小硅碳复合材料的体积能量密度，降低硅碳复合材料的结构稳定性。若孔隙尺寸b较小，会影响硅碳复合材料的比容量和首次库伦效率。例如，第二区域内的孔隙尺寸b可以为2nm、2.5nm、3nm、3.5nm、4nm、4.5nm、5nm、5.5nm、6nm、6.5nm、7nm、7.5nm、8nm或在上述任意两个数值所组成的范围内的任一值。
在一些实施例中，硅碳复合材料脱锂的差分容量曲线在600mV至750mV具有特征峰。
硅碳复合材料脱锂的差分容量-电压曲线可以理解为，其以硅碳复合材料的充放电比容量为横坐标，电压为纵坐标，可得到硅碳复合材料的充放电曲线，然后以硅碳复合材料的脱锂比容量对电压求一阶导作为纵坐标，电压为横坐标，即可得到硅碳复合材料脱锂的差分容量-电压曲线，见图5。差分容量-电压曲线可以反应硅碳复合材料在单位电压范围内所含有的容量。若在某个电压平台处的容量较高，这意味着在很小的电压波动范围内就会贡献非常多的容量，在曲线上就会表现出一个特征峰，每一个特征峰就代表一个电化学反应，同时各个特征峰的峰高也表示了对 应电化学反应对容量贡献的大小。
本申请中，硅碳复合材料脱锂的差分容量曲线在600mV至750mV具有特征峰，表示硅碳复合材料中锂析出的脱锂反应，是由金属锂在硅碳复合材料中的孔隙内析出造成的。其中，在600mV至750mV具有特征峰高越大，表明硅碳复合材料中析出锂对比容量的贡献越大，析出锂的含量越高。在600mV至750mV出现的特征峰，一方面说明硅碳复合材料中的析出锂从孔隙中析出，可以提高硅碳复合材料的倍率性能，另一方面也说明了硅碳复合材料中含有纳米孔隙。同时，孔隙利于硅碳复合材料脱锂，能够提高硅碳复合材料的比容量、循环性能和倍率性能。
同时，硅碳复合材料脱锂的差分容量曲线分别在250mV至300mV和400mV至450mV也具有明显的特征峰，一般认为250mV至300mV的特征峰代表无定型LixSi的脱锂反应，400mV至450mV的特征峰代表硅碳复合材料中结晶型Li15Si4的脱锂反应。
在一些实施例中，硅碳复合材料包括具有100nm至1μm孔径的硅碳复合颗粒，硅碳复合颗粒在硅碳复合材料中的颗粒数量占比小于5％，利于提高硅碳复合材料的压实密度，从而利于提高二次电池的能量密度。若硅碳复合颗粒在硅碳复合材料中的颗粒数量占比大于5％，硅碳复合颗粒占比较大，降低了硅碳复合材料中的压实密度，影响二次电池的能量密度。例如，硅碳复合颗粒在硅碳复合材料中的颗粒数量占比可以为0.5％、1％、1.5％、2％、2.5％、3％、3.5％、4％、4.5％、5％或上述任意数值所组成的范围内。
在一些实施例中，硅碳复合材料包括多孔碳基材、分散于所述多孔碳基材上的硅材料、以及形成于所述多孔碳基材上的碳包覆层。多孔碳基材作为硅碳复合材料的骨架，使得硅碳复合材料具有良好的导电性和循环稳定性，且多孔碳基材作为硅材料沉积的基体，可以抑制硅材料在嵌锂过程中的体积膨胀，从而减少膨胀应力。同时，多孔碳基材中的孔结构还可以分散硅材料的膨胀应力，降低硅碳复合材料的体积膨胀率，进一步改善硅碳复合材料的循环性能和膨胀性能。相较于第二区域，更靠近硅碳复合材料切面边缘处的第一区域会形成富硅区，且通过控制硅材料于多孔碳基材中第一区域和第二区域的分布，从而可以调控第一区域和第二区域内的孔隙尺寸。碳包覆层一方面可以降低硅碳复合材 料的比表面积，减少硅碳复合材料与电解液的副反应，改善其首次库伦效率，另一方面还可以进一步提高硅碳复合材料的导电性，有利于进一步改善其倍率性能。
在一些实施例中，硅材料的粒径小于1nm，有利于缓冲充放电过程中硅材料的形变应力，从而提升硅碳复合材料的循环性能、膨胀性能和倍率性能。例如，硅材料的粒径可以为0.1nm、0.2nm、0.3nm、0.4nm、0.5nm、0.6nm、0.7nm、0.8nm、0.9nm、1nm或上述任意数值所组成的范围内。
在一些实施例中，硅碳复合材料的球形度不低于0.6，有利于提高硅碳复合材料的压实密度，从而提升二次电池的能量密度。较小的球形度会影响硅碳复合材料的压实密度。例如，硅碳复合材料的球形度可以为0.6、0.7、0.8、0.9、0.95或上述任意数值所组成的范围内。
在一些实施例中，基于硅碳复合材料的质量，硅碳复合材料中的碳元素的含量为40％至70％，有利于提高硅碳复合材料的导电性，有利于提升硅碳复合材料的比容量。但是若碳元素较高，相对地会减少硅材料的含量，会降低硅碳复合材料的比容量。硅碳复合材料中硅材料的含量为20％至60％，在此范围内有利于提升硅碳复合材料的比容量。但是若硅材料含量较高，相对地会减小碳材料的含量，会影响硅碳复合材料的循环性能和膨胀性能。通过将碳元素和硅材料控制在上述范围内，可以进一步兼容硅碳复合材料的比容量、循环性能和膨胀性能。例如，硅碳复合材料中的碳元素的含量可以为40％、45％、50％、55％、60％、65％、70％或上述任意数值所组成的范围内。硅碳复合材料中硅材料的含量为20％、25％、30％、35％、40％、45％、50％、55％、60％或上述任意数值所组成的范围内。
在一些实施例中，基于硅碳复合材料的质量，氧元素的质量占比为1％至5％，在硅碳复合材料的嵌锂过程中会生成的Li2O，Li2O可以作为缓冲物质，能够缓冲硅的体积膨胀，有利于提高二次电池的循环性能和膨胀性能和倍率性能。例如硅碳复合材料中氧元素的质量占比可以为1％、1.5％、2％、2.5％、3％、3.5％、4％、4.5％、5％或为上述任意数值组成的范围。
在一些实施例中，硅碳复合材料的粒径DV50为5μm至10μm，硅碳复合材料的粒径DV99为15μm至25μ。硅碳复合材料的在上述粒径范围内，一方面，不仅可以减小硅碳复合材料的颗粒粒 径较小所带来的比表面积较大、电解液消耗量增多以及材料压实密度低的风险，而且还可以防止颗粒粒径较大所引起的离子电导率低、倍率性能差的问题；另一方面，还有利于缩短硅的沉积路径，还能改善硅沉积的均匀性，从而减小硅碳复合材料的嵌锂时的体积膨胀，特别的，当由硅碳复合材料制备的硅碳复合材料应用在负极极片时，可提高负极浆料配制过程中的均匀分散度。例如，硅碳复合材料的粒径DV50可以为5μm、6μm、7μm、8μm、9μm、10μm或为上述任意数值组成的范围。硅碳复合材料的粒径DV99可以为15μ、16μm、17μm、18μm、19μm、20μm、21μm、22μm、23μm、24μm、25μm或为上述任意数值组成的范围。
其中，DV50也称为“中值粒径”，表示硅碳复合材料颗粒在体积基准的粒度分布中，从小粒径测起达到体积累计50％的粒径，即，小于此粒径的硅碳复合材料颗粒的体积占硅碳复合材料颗粒总体积的50％。DV99表示硅碳复合材料颗粒在体积基准的粒度分布中，从小粒径测起达到体积累积99％的粒径。
在一些实施例中，硅碳复合材料的比表面积为1m2/g至50m2/g，有利于降低硅碳复合材料与电解液发生的副反应，改善硅碳复合材料的首次库伦效率和循环性能。硅碳复合材料的比表面积可以为1m2/g、5m2/g、10m2/g、15m2/g、20m2/g、25m2/g、30m2/g、35m2/g、40m2/g、45m2/g、50m2/g或为上述任意两个数值组成的范围。
在一些实施例中，硅碳复合材料在5吨压力下的压实密度为1.05g/cm3至1.15g/cm3，有利于提高极片的压实密度，从而提升二次电池的能量密度。例如，硅碳复合材料在5吨压力下的压实密度可以为1.05g/cm3、1.06g/cm3、1.07g/cm3、1.08g/cm3、1.09g/cm3、1.10g/cm3、1.11g/cm3、1.12g/cm3、1.13g/cm3、1.14g/cm3、1.15g/cm3或为上述任意两个数值组成的范围。
在一些实施例中，硅碳复合材料的首次脱锂比容量500mAh/g至2500mAh/g，在上述范围下，有利于提高二次电池的循环性能、膨胀性能和倍率性能。例如，硅碳复合材料的首次脱锂克容量可以为500mAh/g、600mAh/g、700mAh/g、800mAh/g、900mAh/g、1000mAh/g、1100mAh/g、1200mAh/g、1300mAh/g、1400mAh/g、1500mAh/g、1600mAh/g、1700mAh/g、1800mAh/g、1900mAh/g、2000mAh/g、2100mAh/g、2200mAh/g、2300mAh/g、2400mAh/g、2500mAh/g或上述任意数值组成的范围。
本申请中，上述硅碳复合材料的制备方法包括：
(1)提供多孔碳基材。
多孔碳基材可以选用活性炭、模板多孔碳、炭分子筛、炭纳米纤维、碳纳米管等和膨胀石墨等中的至少一种。优选地，所述活性炭是由生物碳、树脂碳、焦炭等进行活化所获得的。
(2)采用气相沉积向多孔碳基材内通入硅源气体，以在多孔碳基材内沉积单质硅。
硅源气体可以包括但不限于甲硅烷、乙硅烷、丙硅烷、四硅烷、氯硅烷、二氯硅烷、三氯硅烷或四氯硅烷中的一种或多种。在反应时，硅源气体和惰性气体同时通入多孔碳基材内，以稀释硅源气体，使得硅源气体和多孔碳基材充分反应。
本申请通过调控硅材料沉积过程中硅源气通入的流速、时间以及热解的温度，改变硅碳复合材料中第一区域和第二区域内的孔隙尺寸。
其中，硅源气体热解的温度为460℃～500℃，硅源气体通入的流速为1～5L/min，甲硅烷通入的时间为5～10h。在上述条件下，以控制硅碳复合材料中第一区域和第二区域内的孔隙尺寸大小。在一些实施例中，硅源气体热解的温度可以为460℃、470℃、480℃、490℃、500℃或上述任意数值组成的范围内的任一值。硅源气体通入的流速可以为1L/min、2L/min、3L/min、4L/min、5L/min或上述任意数值组成的范围内的任一值。甲硅烷通入的时间可以为5h、6h、7h、8h、9h、10h或上述任意数值组成的范围内的任一值。在上述硅源气体热解的温度下，若提高硅源气体热解的温度，硅源气体的沉积速率增加，第二区域内的孔隙尺寸更大，第一区域内的孔隙尺寸更小，会影响活性离子的脱嵌，且也不利于控制第一区域和第二区域内的孔隙尺寸。若降低硅源气体热解的温度，硅源气体的沉积速率降低，不利于沉积。
在上述硅源气体通入的流速下，若提高硅源气体通入的流速，更多的硅源气体进入第二区域并沉积于第二区域内，会明显降低第二区域内的孔隙尺寸，从而恶化硅碳复合材料的比容量和首次库伦效率。若降低硅源气体通入的流速，更多的硅源气体进入第一区域并沉积于第一区域内，会降低第一区域内的孔隙尺寸，不利于活性离子的脱嵌，降低硅碳复合材料的比容量。
在上述硅源气体通入的时间下，若提高硅源气体通入的时间，第一区域和第二区域内的孔隙尺寸均会下降。
(3)向沉积有单质硅的多孔碳基材内通入碳源气体，以在多孔碳基材上沉积碳材料形成碳包覆层。
通过碳源气体的沉积，在多孔碳基材上形成碳包覆层，碳包覆层一方面可以降低硅碳复合材料的比表面积，减少硅碳复合材料与电解液的副反应，改善其首次库伦效率，另一方面还可以进一步提高硅碳复合材料的导电性，有利于进一步改善其倍率性能。
碳源气体可以包括但不限于甲烷、乙炔、乙烯、乙烷、丙炔、丙烯、丙烷、丁炔、丁烯或丁烷中的一种或多种。
负极活性层还包含粘结剂，用以粘结负极活性材料颗粒从而便于形成膜层，同时还能够提高负极活性层与负极集流体之间的结合力。在一些实施例中，粘结剂可包括但不仅限于聚乙烯醇、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1,1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂或尼龙等。
负极活性层还可包括导电材料，导电材料包括但不限于基于碳的材料、基于金属的材料、导电聚合物或其任意组合。在一些实施例中，基于碳的材料可包括但不仅限于自天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维或其任意组合。在一些实施例中，基于金属的材料可包括但不仅限于金属粉或金属纤维，例如铜、镍、铝或银。在一些实施例中，导电聚合物可为聚亚苯基衍生物。
负极活性层还可进一步地包含石墨，由于石墨具有一定的柔韧性，其与硅碳复合材料配合能够缓解负极活性层整体的体积膨胀。同时，石墨与硅碳复合材料同时作为负极活性材料还能够充分利用硅碳复合材料和石墨两者的优势以达到较好的电化学性能。
本申请中，负极活性层中石墨的质量占比为35wt.％到95wt.％，得到的负极活性层满足如下条件中的至少一者：(1)负极活性层的粒径DV50为5μm至15μm，DV99为15μm至40μm；(2)负极活性层的比表面积为1m2/g至10m2/g；(3)负极活性层的压实密度为1.35g/cm3至1.8g/cm3；(4)负极活性层的首次脱锂比容量为400mAh/g至1000mAh/g。
负极活性层中，石墨的质量占比在上述范围内，可以进一步地改善负极活性层的循环性能，从而提高二次电池的循环性能。
负极活性层整体的粒径、比表面积、粉末压实密度以及首次脱锂比容量控制在上述范围内，可以进一步改善二次电池的能量密度、首次库伦效率、循环性能以及倍率性能。
隔离膜
隔离膜包括具有多孔结构的膜层，其材质包括但不仅限于聚乙烯、聚丙烯、聚偏氟乙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺或芳纶中的至少一种。例如，隔离膜可为聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜等。
电解液
电解液的状态可以是凝胶态、固态和液态中的一种或多种。在一些实施例中，液态电解液包括锂盐和有机溶剂。锂盐可选自但不仅限于六氟磷酸锂(LiPF6)、四氟硼酸锂(LiBF4)、六氟砷酸锂(LiAsF6)、高氯酸锂(LiClO4)、四苯硼酸锂(LiB(C6H5)4)、甲磺酸锂(LiCH3SO3)、双氟磺酰亚胺锂(LiFSI)、双三氟甲烷磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiCF3SO3)、双(三氟甲基磺酰)亚胺锂(LiN(SO2CF3)2、三(三氟甲基磺酰)甲基锂(LiC(SO2CF3)3)、二草酸硼酸锂(LiBOB)和二氟磷酸锂(LiPO2F2)中的一种或多种。例如，锂盐选用LiPF6，因为它可以给出高的离子导电率并改善循环特性。有机溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物、腈化合物、其它有机溶剂或它们的组合。碳酸酯化合物的实例包括但不仅限于碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸甲乙酯(MEC)、碳酸亚乙酯(EC)、碳酸亚丁酯(BC)、碳酸乙烯基亚乙酯(VEC)、碳酸氟代亚乙酯(FEC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯、碳酸三氟甲基亚乙酯或其组合。
正极极片
正极极片包括正极集流体和设于正极集流体上的正极活性层。正极集流体可以使用铝箔或镍箔等，也可为任何现有技术中公开的复合集流体，例如但不仅限于前述导电箔和聚合物基底结合形成的集流体。正极活性层包含正极活性材料，正极活性材料包括可逆地嵌入和脱嵌锂离子的化合物(即，锂化插层化合物)。 在一些实施例中，正极活性材料可以包括锂过渡金属复合氧化物。该锂过渡金属复合氧化物含有锂以及从钴、锰和镍中选择的至少一种元素。在一些实施例中，正极活性材料可包括但不仅限于钴酸锂(LiCoO2)、锂镍锰钴三元材料(NCM)、锰酸锂(LiMn2O4)、镍锰酸锂(LiNi0.5Mn1.5O4)或磷酸铁锂(LiFePO4)中的至少一种。
正极活性层还包含粘合剂，用以粘结正极活性材料颗粒从而便于形成膜层，同时还能够提高正极活性层与正极集流体之间的结合力。在一些实施例中，粘合剂可包括但不仅限于聚乙烯醇、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1,1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂或尼龙等中的至少一种。
正极活性层还可包含导电材料，导电材料包括但不限于基于碳的材料、基于金属的材料、导电聚合物或其任意组合。在一些实施例中，基于碳的材料可包括但不仅限于自天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维或其任意组合。在一些实施例中，基于金属的材料可包括但不仅限于金属粉或金属纤维，例如铜、镍、铝或银。在一些实施例中，导电聚合物可为聚亚苯基衍生物。
将上述二次电池应用于电子装置中，以为电子装置中的负载进行供电。而且，上述二次电池中的硅碳复合材料具有优异的循环性能、膨胀性能和倍率性能，有利于提高电子装置的使用寿命。其中，电子装置可包括但不仅限于笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
以下通过具体实施例和对比例对本申请进行说明。本领域技术人员应理解，本申请中描述的制备方法仅是实施例，其他任何合适的制备方法均在本申请的范围内。
实施例1
(1)将多孔碳基材(多孔碳基材的比表面积为2000m2/g， 孔容为0.9cm3/g，微孔占比为99％)在70℃下进行真空烘干处理，取1000g烘干后的多孔碳基材置于流化床反应容器内，在纯度为99.999％的氮气保护气氛下加热多孔碳材料至480℃，以18L/min的纯度为99.999％的氮气为稀释气，通入流速为2L/min、100％浓度的甲硅烷气体，持续反应6h，使甲硅烷在多孔碳基材孔内发生吸附并沉积形成单质硅。
(2)在纯度为99.999％的氮气保护气氛下，加热沉积有单质硅的多孔碳基材至520℃，以6L/min的纯度为99.999％的氮气为稀释气，通入流速为6L/min、100％浓度的乙炔气体，持续反应4h，使得乙炔气体在沉积有单质硅的多孔碳材料外表面和部分孔内发生沉积，并形成无定形碳的碳包覆层，得到硅碳复合材料。
实施例2至实施例6以及对比例1至对比例5
实施例2至实施例6以及对比例1至对比例5与实施例1的不同之处，在于调整了甲硅烷热解温度、甲硅烷流速以及甲硅烷通入时间。按照表1调整相关制备参数以外，其余与实施例1相同。
对比例6
将经过400目过筛和除磁前处理的微米硅粉与石墨以45:55的质量比例混合，并在惰性气氛下研磨，得到硅碳复合材料。
实施例1制备的硅碳复合材料的颗粒切片结构示意图，如图1所示，图1中第一区域(即区域I)的孔隙尺寸小于第二区域(即区域II)的孔隙尺寸。对比例1制备的硅碳复合材料的颗粒切片结构示意图，如图2所示，图2中第二区域(即区域II)的孔隙尺寸小于第一区域(即区域I)的孔隙尺寸。
实施例1制备的硅碳复合材料的颗粒切片中第一区域和第二区域的扫描透射电子显微镜图(STEM图)，如图3和图4。在图3中箭头示意位置(相对于其他位置颜色较深处)，可以看出第一区域内存在纳米孔隙。在图4中箭头示意位置(相对于其他位置颜色较深处)，可以看出第二区域内存在纳米孔隙。图3和图4中，第一区域和第二区域在相同的标尺20nm下，明显看出图3所示的第一区域的孔隙尺寸小于图4所示的第二区域的孔隙尺寸。
其中，各实施例和对比例的制备条件记载于表1中。
表1
对实施例1至6以及对比例1至对比例6制备的硅碳复合材料进行硅晶粒尺寸、球形度、碳/硅含量、DV50/DV99、比表面积、压实密度以及氧元素含量测试。测试数据记载于表2。
测试方法
(1)STEM测试：
借助FIB(聚焦离子束)对硅碳复合材料进行切片，然后采用场FEI Talos F200S型发射高分辨率透射电子显微镜，在200kV的电压和100nA的电流下，对硅碳复合材料进行测试，并划分第一区域和第二区域，以分别测量第一区域和第二区域内的孔隙尺寸。
(2)XRD测试和硅碳复合材料中硅微晶尺寸的计算方法：
采用D8 Advance设备，以Cu靶为靶材，在60kV的电压下，从2θ为10°到80°的角度范围进行测试。得到硅碳复合材料的XRD图谱后，在2θ＝28.4°上运用德拜-谢乐公式：D＝Kλ/βcosθ，可计算出硅碳复合材料中硅微晶的尺寸大小。其中，K为Scherrer常数，D为硅微晶尺寸大小，B为实测样品 衍射峰半高宽，θ为布拉格衍射角，γ为X射线波长。
(3)硅碳复合材料中硅元素和碳元素含量的表征方法：
借助ICP(电感耦合等离子光谱发生仪)技术对硅碳复合材料中硅元素、碳元素的含量进行表征。
(4)硅碳复合材料球形度的测试：
首先通过IB-09010CP/离子抛光仪(电压为6kV)对待测硅碳复合材料进行抛光，随后采用JEOL-JSM-6700F型扫描电镜，在5kV的电压和0.8nA的电流下，并在背散模式下对硅碳复合材料进行测试，得到硅碳复合材料横切面在背散模式下的扫描电镜图。通过英国晶格码SHAPE工业图像分析与处理软件测得。球形度是与物体相同体积球体的表面积和物体表面积的比，是表征颗粒形貌的参数，形貌上越接近球的颗粒，其球形度越接近于1。任意颗粒球形度的计算公式：
其中，Vp为颗粒体积，Sp为颗粒表面积。
(5)SEM测试：
首先通过IB-09010CP/离子抛光仪(电压为6kV)对硅碳复合材料进行抛光，随后采用JEOL-JSM-6700F型扫描电镜，在5kV的电压和0.8nA的电流下，并在背散模式下对硅碳复合材料进行测试。
(6)硅碳复合材料DV50/DV99的测试：
在50ml洁净烧杯中加入0.02g各实施例和对比例中的硅碳复合材料的粉末样品，加入20ml去离子水，再滴加表面活性剂，使粉末样品完全分散于水中，在120W超声清洗机中超声5min，采用MasterSizer 2000设备，从0°到135°的检测角对硅碳复合材料进行测试，依据粒度分布激光衍射法GB/T19077-2016，测量出粒径分布，得到硅碳复合材料的DV50和DV99值。
(7)硅碳复合材料比表面积的测试：
采用TriStarⅡ3020设备，对硅碳复合材料的BET比表面积进行测试，测试依据国家标准GB/T 19587-2017《气体吸附BET法测定固态物质比表面积》进行。具体如：取硅碳复合材料作为样品，样品管浸没在-196℃液氮中，在0.05～0.30相对压力下测定不同压力下氮气在固体表面的吸附量，基于BET多层吸附理 论及其公式求得试样单分子层吸附量，从而计算出固体的比表面积。
(8)硅碳复合材料氧元素含量的测试：
采用德国Elementar元素分析仪对硅碳复合材料的氧元素含量进行测试。
(9)硅碳复合材料压实密度的测试：
采用三思纵横UTM7305型电池粉末压实密度仪，在5吨压力下，对硅碳复合材料的压实密度进行测试。
表2
实施例1制备的硅碳复合材料脱锂时的差分容量曲线图，如图5。从图5中可知，差分容量曲线在250mV至300mV、400mV至450mV、600mV至750mV具有明显的特征峰。
实施例1制备的硅碳复合材料的横切面在背散模式下的SEM图，如图6。在图6中，硅碳复合材料的切面密实，箭头所 指位置存在孔隙，硅碳复合材料中切面呈现孔隙的颗粒较少。
扣式半电池的制备过程包括：
(1)负极极片的制备过程：将上述实施例制备得到的硅碳复合材料、乙炔黑与海藻酸钠粘结剂按照质量比80：10：10加入去离子水，充分搅拌后形成浆料，利用刮刀涂布100um厚度的涂层，85℃经过12小时真空干燥箱烘干后，在干燥环境中利用冲压机切成直径为1cm的圆片，得到负极极片。
电解液以及隔离膜：在充满氩气的手套箱(水分<10ppm，氧分<1ppm)中，将碳酸乙烯酯(EC)和碳酸二甲酯(DMC)以1:1的体积比混合均匀，以得到混合溶液，在混合溶液中加入1mol/L的LiPF6和5vol.％的氟代碳酸乙烯酯(FEC)，搅拌均匀得到电解液。采用Celgard 2400隔膜作为隔离膜。
(2)扣式半电池的组装：
将上述负极极片以锂片作为对电极，按照负极极片、隔离膜、锂片的顺序，以锂片作为对电极在手套箱中组装成扣式半电池。
对实施例1至6以及对比例1至对比例6制备的硅碳复合材料组装的扣式电池进行首次脱锂比容量、首次库伦效率、容量保持率、倍率性能以及膨胀率进行测试，具体的测试方法如下：
首次脱锂比容量和首次库伦效率的测试方法包括：
在蓝电电池测试系统(LAND CT2001A)上，对上述组装的扣式半电池进行充放电测试。半电池测试采用0.01V～2.0V的工作电压区间，以0.1C恒流放电至0.01V，静置5min，再以50μA恒流放电至0.01V，静置5min，以0.1C恒流充电至2.0V，静置5min，记录扣式半电池的首次放电容量和充电容量分别为首次嵌锂容量和首次脱锂比容量。
首次库伦效率(％)＝(首次脱锂容量/首次嵌锂容量)×100％。
然后以硅碳复合材料的脱锂比容量对电压求一阶导作为纵坐标，电压为横坐标，即可得到硅碳复合材料脱锂时的差分容量-电压曲线。
半电池循环50圈后的容量保持率(％)的测试方法包括：
将上述组装的扣式半电池在25℃条件下，以0.5C恒流放电至0.01V，静置5min，再以50μA恒流放电至0.01V，静置5min，以0.5C恒流充电至2.0V，静置5min，记录首圈循环的放电容量。然后以相同的步骤进行50圈充电和放电循环，记录第50圈的放电容量。
半电池50圈循环容量保持率(％)＝(第50圈循环的放电容量/首圈循环的放电容量)×100％。
半电池的倍率性能的测试方法包括：
在蓝电电池测试系统(LAND CT2001A)上，对上述组装得到的扣式半电池进行倍率测试。测试采用0.01V～2V的工作电压区间，以0.5C恒流放电至0.01V，静置5min，再以0.5C恒流充电至2.0V，静置5min，记录扣式半电池的充电容量即为在0.5C下的脱锂容量。同样的，以1.0C、2.0C和5.0C分别按照上述流程进行测试，分别得到半电池在1.0C、2.0C和5.0C下的脱锂容量。通过对比在5.0C下的脱锂容量大小，即可判断硅碳复合材料的倍率性能优劣。
负极极片的厚度膨胀率的测试方法包括：
将上述组装得到的循环50圈前后的扣式半电池进行拆解，分别取得负极极片。用游标卡尺量取12次极片的厚度并取平均值，若铜箔厚度为l，循环50圈前的极片厚度为m，循环50圈后的极片厚度n，则负极极片在循环50圈后的厚度膨胀率k为：k＝(n-m)/(m-l)×100％。
表3

结合上述表1至表3，相对于对比例1至5，实施例1至6的硅碳复合材料中第一区域的孔隙尺寸a小于第二区域的孔隙尺寸b，因此在硅碳复合材料具有优异的比容量时，还能够兼顾良好的首次库伦效率、循环性能、倍率性能和膨胀性能。
具体地，相对于对比例1至5，实施例1至6中在制备硅碳复合材料时，相对地改变甲硅烷热解温度、甲硅烷流速以及甲硅烷通入时间，以使得硅碳复合材料中第一区域的孔隙尺寸小于第二区域的孔隙尺寸。在对比例1至2中，通过提高甲硅烷热解温度、甲硅烷流速，更多的硅进入第二区域内，并沉积形成于第二区域内，减小了第二区域内的孔隙大小，从而使得第一区域的孔隙尺寸大于第二区域内的孔隙尺寸，更多的硅位于第二区域内，减小了与电解液的接触，不利于发挥硅碳复合材料中第二区域内硅的贡献。在对比例1至2中，相对实施例1至2提高了甲硅烷热解温度和甲硅烷流速，但是减小了甲硅烷通入时间，第一区域的孔隙尺寸大于第二区域内的孔隙尺寸，其比容量下降，且其硅碳复合材料的首次库伦效率、循环性能、倍率性能以及膨胀性能均有所下降。
在对比例3至5中，甲硅烷热解温度、甲硅烷流速以及甲硅烷通入时间均有调整，得到硅碳复合材料中的第二区域的孔隙尺寸小于或等于第一区域的孔隙尺寸。在对比例3中，硅碳复合材料中的第一区域和第二区域内的孔隙尺寸大致相同，其相较于实施例，首次脱锂比容量和首次库伦效率下降。这可能是由于第一区域内孔隙相对较大，电解液在孔隙中形成的SEI膜较多，消耗了更多的锂离子，从而降低了硅碳复合材料的首次库伦效率和比容量。
对比例4和对比例5中，相较于实施例1和实施例2，虽然甲硅烷流速有所提高，但是降低了甲硅烷的温度，硅沉积速率降低，更多的硅沉积于第二区域，从而得到第二区域的孔隙尺寸小于第一区域的孔隙尺寸。相较于实施例，对比例4和对比例5中 的硅碳复合材料的比容量和首次库伦效率均有下降，这可能是与第一区域内的孔隙较大，形成的SEI膜较多，从而得到的硅碳复合材料在降低了比容量和首次库伦效率。
对比例6中制备的硅碳复合材料脱锂的差分容量曲线在600mV至750mV并未出现特征峰，对比例6中制备的硅碳复合材料中并未含有纳米孔隙。相较于实施例，对比例6制备的硅碳复合材料，虽然具有较好的比容量，但是其首次库伦效率、循环性能、倍率性以及膨胀性能均下降。这也表明在硅碳复合材料中，纳米孔隙的存在可以缓冲硅的体积膨胀，从而改善硅碳复合材料的循环性能、膨胀性能和倍率性能。同时本申请实施例中，在第一区域的孔隙尺寸小于第二区域的孔隙尺寸时，硅碳复合材料还具有优异的比容量和首次库伦效率。相较于对比例6，实施例1至6中硅碳复合颗粒的占比在合适范围内，具有100nm至1μm孔径的硅碳复合颗粒的占比较少，有利于提高硅碳复合材料的压实密度，从而利于提高二次电池的能量密度。相较于对比例6，实施例1至6中硅碳复合材料的球形度均大于0.6，硅碳复合材料的压实密度均有提升。同时，相较于对比例6，实施例1至6中，硅碳复合材料中碳元素、硅元素、氧元素的含量以及比表面积、压实密度均在合适的范围内，这有利于提高硅碳复合材料的循环性能、倍率性能以及膨胀性能。
对比例1至2中硅碳复合材料中硅的晶粒尺寸均大于1nm，相较于实施例，对比例1至2的首次脱锂比容量、首次库伦效率、容量保持率、倍率性能均有下降，膨胀率略有所上升。这说明硅碳复合材料中硅的晶粒尺寸小于1nm，利于提高硅碳复合材料的循环性能、倍率性能以及膨胀性能。
以上所揭露的仅为本申请较佳实施方式而已，当然不能以此来限定本申请，因此依本申请所作的等同变化，仍属本申请所涵盖的范围。

Claims (10)

  1. 一种硅碳复合材料，其中，所述硅碳复合材料的切面具有第一区域和第二区域，所述第一区域为所述硅碳复合材料的切面边缘沿径向方向向内2μm的区域，所述第二区域为以所述硅碳复合材料材料的中心沿径向方向向外4μm的区域；所述第一区域内的孔隙尺寸小于所述第二区域内的孔隙尺寸。
  2. 如权利要求1所述的硅碳复合材料，其中，所述第一区域内的孔隙尺寸为a，1nm≤a≤6nm；所述第二区域内的孔隙尺寸为b，2nm≤b≤8nm。
  3. 如权利要求1或2所述的硅碳复合材料，其中，所述硅碳复合材料脱锂的差分容量曲线在600mV至750mV具有特征峰。
  4. 如权利要求1至3中任一项所述的硅碳复合材料，其中，所述硅碳复合材料包括具有孔径为100nm至1μm的硅碳复合颗粒，所述硅碳复合颗粒在所述硅碳复合材料中的颗粒数量占比小于5％。
  5. 如权利要求1至4中任一项所述的硅碳复合材料，其中，所述硅碳复合材料包括多孔碳基材、分散于所述多孔碳基材上的硅材料、以及形成于所述多孔碳基材上的碳包覆层。
  6. 如权利要求5所述的硅碳复合材料，其中，所述硅材料的粒径小于1nm。
  7. 如权利要求5或6所述的硅碳复合材料，其中，所述硅碳复合材料满足以下条件中的至少一者：
    (1)基于所述硅碳复合材料的质量，所述硅碳复合材料中碳元素的含量为40％至70％，所述硅碳复合材料中硅元素的含量为20％至60％；
    (2)基于所述硅碳复合材料的质量，氧元素的质量占比为1％至5％；
    (3)所述硅碳复合材料的粒径DV50为5μm至10μm，粒径DV99为15μm至25μ；
    (4)所述硅碳复合材料的比表面积为1m2/g至50m2/g；
    (5)所述硅碳复合材料在5吨压力下的压实密度为1.05g/cm3至1.15g/cm3；
    (6)所述硅碳复合材料的首次脱锂比容量500mAh/g至2500mAh/g。
  8. 如权利要求1至7中任一项所述的硅碳复合材料，其中，所述硅碳复合材料的球形度不低于0.6。
  9. 一种二次电池，其中，包括正极极片、负极极片和电解液，所述负极极片包括层叠设置的负极集流体以及负极活性层，所述负极活性层包括如权利要求1至8中任一项所述的硅碳复合材料。
  10. 一种电子装置，其中，包括如权利要求9所述的二次电池。
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CN116525776A (zh) * 2022-01-31 2023-08-01 兰溪致德新能源材料有限公司 纳米硅氧碳复合材料及其制备方法和应用
CN115312780A (zh) * 2022-10-10 2022-11-08 宁德新能源科技有限公司 负极材料、二次电池和电子装置
CN116730322A (zh) * 2023-05-12 2023-09-12 浙江锂宸新材料科技有限公司 一种锂离子电池用沥青基硅碳负极材料的制备方法及其产品
CN116895729A (zh) * 2023-08-04 2023-10-17 宁德新能源科技有限公司 一种负极材料及其制备方法、二次电池以及电子装置
CN117096330A (zh) * 2023-10-20 2023-11-21 宁德时代新能源科技股份有限公司 硅碳复合材料及其制备方法、二次电池和用电装置

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