A porous resin biomass carbon material, a preparation method and application thereof, and a silicon-carbon composite material, a preparation method and application thereof

Abstract

This invention provides a porous resin biomass carbon material, its preparation method, and its application, as well as a silicon-carbon composite material, its preparation method, and its application, relating to the field of porous carbon technology. This invention pre-carbonizes biomass raw materials, thoroughly mixes the resulting biomass carbon with resin using a hydrothermal method, then carbonizes the resulting resin-biomass carbon composite precursor to obtain resin biomass carbon, and finally gas-activates it to obtain a porous resin biomass carbon material. This invention also carbonizes mainstream biomass to obtain biomass carbon, then stabilizes and solidifies it with resin using a hydrothermal method, allowing the resin to fill and repair macroporous defects on the surface of the biomass carbon. Subsequent secondary carbonization and gas activation yield a porous resin biomass carbon material, providing new possibilities for the development of high-performance, cost-effective anode materials for high-energy-density lithium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of porous carbon technology, specifically to a porous resin biomass carbon material and its preparation method and application, and a silicon-carbon composite material and its preparation method and application. Background Technology

[0002] To meet the demands of electric vehicles and other applications requiring higher energy densities, extensive research has been conducted on lithium-ion battery electrode materials with high energy density, high power density, and long cycle life. Nano-silicon-carbon, as a lithium-ion battery anode material, possesses high lithium storage capacity (its theoretical room-temperature capacity reaches 3580 mAh / g, far exceeding graphite's 372 mAh / g), making it a promising candidate to replace graphite as the next-generation high-energy-density lithium-ion battery anode material. However, the practical application of silicon-based anodes also faces significant challenges. For example, the approximately 300% volume change during charge and discharge and the unstable solid-state electrolyte interface (SEI) severely reduce the cycle stability and lifespan of silicon-based materials.

[0003] Silicon-carbon anodes prepared using vapor deposition have become one of the mainstream solutions. Utilizing the uniform combination of a porous carbon framework and nano-silicon, they exhibit lower expansion, longer cycling life, and higher initial coulombic efficiency compared to other materials, which is beneficial for their commercial-scale production. Currently, mainstream porous carbon framework raw materials include universally applicable biomass-based materials, high-stability resins, and petrochemical byproducts, but biomass remains the primary choice due to cost considerations. However, biomass, being a natural product, inherently possesses significant pore defects. The nano-silicon deposited using the porous characteristics of biomass is unstable, leading to problems such as unstable expansion, cycling degradation, and batch stability in silicon-carbon anode materials prepared using biomass carbon as a substrate during practical applications.

[0004] To address the aforementioned issues, numerous scholars have proposed various solutions from different perspectives, including raw material selection and pore-forming processes. For example, a method for preparing a porous silicon-carbon anode material coated with a fast-ion conductor has been disclosed. This method involves pre-carbonizing resin under a nitrogen atmosphere to obtain a carbon precursor; crushing the carbon precursor and mixing it with an alkali in a solid-phase manner; then sequentially activating and acid-washing the mixture to obtain a porous carbon material; depositing nano-silicon onto the surface of the porous carbon material using silane compounds to obtain a nano-silicon deposited porous carbon substrate; chemical vapor deposition of the nano-silicon deposited porous carbon substrate under a protective atmosphere using a carbon source gas to obtain a silane deposited porous carbon composite material; and then sequentially refluxing and calcining the silane deposited porous carbon composite material, metal salt, phosphate solution, and alkaline precipitant to obtain the fast-ion conductor-coated porous silicon-carbon anode material. However, the pore uniformity of the porous carbon material prepared by the aforementioned prior art is insufficient, leading to uneven dispersion of the deposited nano-silicon and affecting its recyclability. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a porous resin biomass carbon material, its preparation method and application, and a silicon-carbon composite material, its preparation method and application. The preparation method provided by this invention solves the pore defects of pure biomass porous carbon, and while maintaining the advantage of low cost, simultaneously improves the pore defects of biomass-based materials and the uniformity and stability of subsequent vapor-deposited nano-silicon.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing porous resin biomass carbon materials, comprising the following steps:

[0008] Biomass carbon is mixed with liquid resin and hydrothermally compounded to obtain a resin-biomass carbon composite precursor.

[0009] The resin biomass carbon composite precursor is carbonized to obtain resin biomass carbon.

[0010] The resin biomass carbon is activated by gas to obtain porous resin biomass carbon material.

[0011] Preferably, the method for preparing biomass carbon includes the following steps: pre-carbonizing biomass raw materials to obtain biomass carbon;

[0012] The biomass raw materials include one or more of the following: coconut shells, camellia shells, wood, cellulose, straw, bamboo, walnut shells, sugar, and starch;

[0013] The particle size of the biomass raw material is 1~3mm;

[0014] The pre-carbonization temperature is 400~600℃, and the holding time is 1~3h.

[0015] Preferably, the liquid resin comprises one or more of water-soluble phenolic resin, water-soluble polyester resin, and water-soluble acrylic resin; the viscosity of the liquid resin is 0.2~0.9 Pa·s;

[0016] The mass ratio of biomass carbon to liquid resin is 2~10:1;

[0017] The hydrothermal composite process includes a heating and pressurization stage, a heat preservation and pressurization stage, and a cooling and pressurization stage. The heating and pressurization stage has a heating rate of 5~10℃ / min and a pressurization rate of 0.1~0.5MPa / min. The heat preservation and pressurization stage has a temperature of 120~180℃, a pressure of 3~5MPa, and a time of 2~10h. The cooling and pressurization stage lasts for 10~12h.

[0018] The carbonization process includes a first carbonization and a second carbonization in sequence; the temperature of the first carbonization is 300~500℃ and the holding time is 1~3h; the temperature of the second carbonization is 800~1000℃ and the holding time is 2~4h.

[0019] Preferably, the activating gas used for gas activation includes one or more of nitrogen, carbon dioxide, water vapor, air, and oxygen;

[0020] The gas activation includes sequentially performing a first gas activation and a second gas activation;

[0021] The activation temperature of the first gas is 500~800℃, and the holding time is 3~6h;

[0022] The activation temperature of the second gas is 1000~1200℃, and the holding time is 5~8h.

[0023] The present invention also provides a porous resin biomass carbon material prepared by the preparation method described above, wherein the porous resin biomass carbon material has a specific surface area of ​​1500~3000 m². 2 / g, pore size 0.5~50nm, total pore volume 0.6~1.0cm³ 3 / g.

[0024] The present invention also provides the application of the porous resin biomass carbon material described in the above technical solution in the preparation of electrodes.

[0025] This invention also provides a method for preparing a silicon-carbon composite material, comprising the following steps:

[0026] The porous resin biomass carbon material described in the above technical solution is subjected to chemical vapor deposition of silicon to obtain silicon-carbon material;

[0027] The silicon-carbon material is obtained by carbon coating.

[0028] Preferably, the conditions for the vapor phase chemical deposition include: the reaction gas includes silane and / or silane, the dilution gas includes one or more of nitrogen, hydrogen, helium and argon, the preheating temperature is 300~400℃, the preheating time is 5~9h, the deposition temperature is 400~600℃, and the deposition time is 6~12h.

[0029] The carbon coating process involves applying a mixed gas to silicon-carbon materials; the mixed gas includes a carrier gas and a carbon source gas, the carrier gas includes nitrogen, and the carbon source gas includes one or more of methane, acetylene, propylene, and propane; the carbon coating temperature is 500~700℃, and the time is 4~10h.

[0030] The present invention also provides a silicon-carbon composite material prepared by the preparation method described in the above technical solution.

[0031] The present invention also provides the application of the silicon-carbon composite material described in the above technical solution as an electrode in a battery.

[0032] The present invention provides a method for preparing porous resin biomass carbon materials. This method involves carbonizing mainstream biomass to obtain biomass carbon, then stabilizing and curing it with resin using a hydrothermal method. The resin fills and repairs the large pore defects on the surface of the biomass carbon. Subsequent carbonization and gas activation improve the uniformity of the pores. The resulting pore sizes are suitable for subsequent deposition of nano-silicon in the porous resin biomass carbon materials. The porous resin biomass carbon materials exhibit high pore utilization, providing new possibilities for the development of cost-effective anode materials for high-energy-density lithium-ion batteries.

[0033] Due to the inherent macroporous structure defect of biomass carbon, silicon-carbon anodes obtained by vapor deposition using it are prone to poor deposition uniformity and structural stability. Compared with existing technologies, this invention utilizes resin to repair the inherent macroporous defects of biomass carbon. While maintaining the cost advantage of biomass compatibility, it improves the particle defects of pure biomass porous carbon. X-ray diffraction analysis shows that the degree of macroporous defects can be improved by adjusting the amount of resin. This invention utilizes this porous resin biomass carbon without excessively increasing costs, and simultaneously employs a lower-cost gas activation method with higher pore utilization to obtain porous resin biomass carbon materials. This improves the dispersion uniformity of nano-silicon deposited in the porous resin biomass carbon material, enhances the stability of the silicon-carbon composite material, and enables the silicon-carbon composite material prepared using it to not only improve the energy density of the battery but also improve cycle performance, providing strong technical support for the development of next-generation high-performance lithium-ion batteries.

[0034] Moreover, the preparation method provided by this invention has low production cost and can realize the mass production of porous resin biomass carbon materials. Attached Figure Description

[0035] Figure 1 XRD patterns of the porous resin coconut shell carbon material prepared in Example 1 and the porous coconut shell carbon material prepared in Comparative Example 1.

[0036] Figure 2 SEM images of the porous resin coconut shell carbon material prepared in Example 1 and the porous coconut shell carbon material prepared in Comparative Example 1.

[0037] Figure 3 Backscattered electron imaging images of the porous resin coconut shell carbon material prepared in Example 1 and the porous coconut shell carbon material prepared in Comparative Example 1.

[0038] Figure 4The first-cycle electrical performance curve of the silicon-carbon composite material obtained in Application Example 1 is shown. Detailed Implementation

[0039] This invention provides a method for preparing porous resin biomass carbon materials, comprising the following steps:

[0040] Biomass carbon is mixed with liquid resin and hydrothermally compounded to obtain a resin-biomass carbon composite precursor.

[0041] The resin biomass carbon composite precursor is carbonized to obtain resin biomass carbon.

[0042] The resin biomass carbon is activated by gas to obtain porous resin biomass carbon material.

[0043] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0044] This invention involves mixing biomass carbon with liquid resin and performing hydrothermal composite to obtain a resin-biomass carbon composite precursor.

[0045] In this invention, the method for preparing biomass carbon may include the following steps: pre-carbonizing biomass raw materials to obtain biomass carbon.

[0046] In this invention, the biomass raw material may include one or more of coconut shells, camellia shells, wood, cellulose, straw, bamboo, walnut shells, sugar, and starch, specifically coconut shells. In this invention, the biomass raw material may be crushed before use, and the crushing may be carried out using one or more of a jaw crusher, roller crusher, and air jet mill; the particle size of the crushed biomass raw material may be 1-3 mm, specifically 1 mm, 1.5 mm, 2 mm, 2.5 mm, or 3 mm.

[0047] In this invention, the pre-carbonization temperature can be 400~600℃, specifically 400℃, 450℃, 500℃, 550℃, or 600℃; the pre-carbonization holding time can be 1~3h, specifically 1h, 1.5h, 2h, 2.5h, or 3h; the pre-carbonization can be carried out in a high-temperature reactor, including a pusher kiln, roller kiln, box furnace, or tube furnace. Under the above conditions, the first carbonization in this invention is beneficial for removing intrinsic non-carbon components of biomass and constructing the carbon structure characteristics of biomass to facilitate subsequent resin modification and bonding.

[0048] In this invention, the particle size of the biomass carbon is 1-3 mm, specifically 1 mm, 1.5 mm, 2 mm, 2.5 mm, or 3 mm; the specific surface area of ​​the biomass carbon can be <300 m². 2 / g, and can also be <150m 2 / g; the pore volume of the biomass carbon can be <0.3cm. 3 / g.

[0049] In this invention, the liquid resin may include one or more of water-soluble phenolic resin, water-soluble polyester resin, and water-soluble acrylic resin; the solid content of the liquid resin may be 65-80%, specifically 65%, 70%, 75%, or 80%; the solvent in the resin may be one or more of water, methanol, ethanol, ethylene glycol, and n-butanol, specifically water; the viscosity of the liquid resin may be 0.2-0.9 Pa·s, specifically 0.2 Pa·s, 0.3 Pa·s, 0.4 Pa·s, 0.5 Pa·s, 0.6 Pa·s, 0.7 Pa·s, 0.8 Pa·s, or 0.9 Pa·s.

[0050] In this invention, the mass ratio of biomass carbon to liquid resin can be 2 to 10:1, specifically 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, or 9:1. By controlling the mass ratio of biomass carbon to liquid resin within the above range, this invention facilitates the acquisition of the most stable and highest-performing resin-biomass composite porous carbon, thereby providing a stable and high-quality porous carbon carrier for novel silicon-based anode materials.

[0051] In this invention, the mixing device can be a solid-liquid dispersion device or a liquid phase reactor, specifically a batch reactor, a tubular reactor, or a liquid phase reactor.

[0052] In this invention, the hydrothermal composite process may include a heating and pressurization stage, a heat preservation and pressurization stage, and a cooling and pressurization stage. In this invention, the heating rate in the heating and pressurization stage can be 5~10℃ / min, specifically 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, or 10℃ / min; the pressurization rate in the heating and pressurization stage is 0.1~0.5MPa / min, specifically 0.1MPa / min, 0.2MPa / min, 0.3MPa / min, 0.4MPa / min, or 0.5MPa / min. In this invention, the temperature during the heat preservation and pressure holding stage can be 120~180℃, specifically 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, or 180℃; the pressure during the heat preservation and pressure holding stage is 3~5MPa, specifically 3MPa, 3.5MPa / min, 4MPa / min, 4.5MPa / min, or 5MPa / min; the heat preservation time during the heat preservation and pressure holding stage can be 2~10h, specifically 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, or 10h. In this invention, the time during the cooling and pressure reduction stage can be 10~12h, specifically 10h, 10.5h, 11h, 11.5h, or 12h; the cooling method during the cooling and pressure reduction stage can be natural cooling; the cooling and pressure reduction stage stops when the temperature drops to room temperature and the pressure drops to atmospheric pressure. In this invention, the hydrothermal compounding is carried out under stirring conditions. The stirring speed can be 500~800 r / min, specifically 500 r / min, 600 r / min, 700 r / min, or 800 r / min. Compared with high-speed stirring, the above-mentioned heating and pressurizing hydrothermal compounding method adopted in this invention is beneficial to improving the interfacial bonding stability between biomass carbon and resin, compensating for the core defects of simple physical high-speed dispersion, and increasing technical feasibility and stability.

[0053] After completing the hydrothermal composite process, the present invention may further include drying the product obtained from the hydrothermal composite to obtain a resin-biomass carbon composite precursor. In this invention, the drying method may include one or more of spray drying, centrifugal drying, and vacuum drying, specifically centrifugal drying followed by vacuum drying in sequence. In this invention, the centrifugal drying speed may be 3000~5000 r / min, specifically 3000 r / min, 3500 r / min, 4000 r / min, 4500 r / min, or 5000 r / min; the centrifugal drying time may be 5~20 min, specifically 5 min, 10 min, 15 min, or 20 min; the centrifugal drying may be carried out in a centrifuge. In this invention, the vacuum drying temperature can be 60~100℃, specifically 60℃, 70℃, 80℃, 90℃ or 100℃; the vacuum drying pressure can be 5~30kPa, specifically 5kPa, 10kPa, 15kPa, 20kPa, 25kPa or 30kPa; the vacuum drying time can be 12~24h, specifically 12h, 14h, 16h, 18h, 20h, 22h or 24h; the vacuum drying can be carried out in a vacuum drying device.

[0054] The resin-biomass carbon composite precursor prepared by this invention has the characteristics of uniformity and stable binding.

[0055] After obtaining the resin biomass carbon composite precursor, the present invention carbonizes the resin biomass carbon composite precursor to obtain resin biomass carbon.

[0056] In this invention, the carbonization may include sequentially performing a first carbonization and a second carbonization. In this invention, the temperature of the first carbonization can be 500~800℃, specifically 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, or 800℃; the holding time of the first carbonization can be 3~6 hours, specifically 3 hours, 3.5 hours, 4 hours, 4.5 hours, 6 hours, 5.5 hours, or 6 hours. In this invention, the temperature of the second carbonization can be 1000~1200℃, specifically 1000℃, 1050℃, 1100℃, 1150℃, or 1200℃; the holding time of the second carbonization can be 5~8h, specifically 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, or 8h; the temperature rise rate from the temperature of the first carbonization to the temperature of the second carbonization can be 3~10℃ / min, specifically 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, or 10℃ / min. In this invention, the carbonization can be carried out in a high-temperature reactor, including a pusher kiln, roller kiln, box furnace, or tube furnace, and the first and second carbonizations can be carried out under the same equipment conditions. This invention, by carrying out the first and second carbonizations under the same equipment conditions, facilitates the formation of resin-modified biomass porous carbon, which is conducive to the deposition of nano-silicon to form novel silicon-based anode materials.

[0057] After obtaining resin biomass carbon, the present invention performs gas activation on the resin biomass carbon to obtain porous resin biomass carbon material.

[0058] In this invention, the activating gas used for gas activation may include one or more of nitrogen, carbon dioxide, water vapor, air and oxygen, and may specifically be nitrogen.

[0059] In this invention, the gas activation may include sequentially performing a first gas activation and a second gas activation. In this invention, the temperature for the first gas activation can be 500~800℃, specifically 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, or 800℃; the holding time for the first gas activation can be 3~6h, specifically 3h, 3.5h, 4h, 4.5h, 6h, 5.5h, or 6h; the heating rate from room temperature to the temperature of the first gas activation can be 3~10℃ / min, specifically 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, or 10℃ / min. In this invention, the temperature for the second gas activation can be 1000~1200℃, specifically 1000℃, 1050℃, 1100℃, 1150℃, or 1200℃; the holding time for the second gas activation can be 5~8h, specifically 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, or 8h; the heating rate from the temperature of the first gas activation to the temperature of the second gas activation can be 3~10℃ / min, specifically 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, or 10℃ / min. In this invention, the gas activation can be carried out in a high-temperature reactor, including a pusher kiln, roller kiln, box furnace, or tube furnace. This invention, employing a gas activation method, can effectively improve problems such as poor uniformity, insufficient deposition amount, and poor stability of the deposition state in nano-silicon deposition. Compared with chemical activation methods (such as acid activation and alkali activation), the present invention uses a gas activation method, which can be reused, has low cost and high pore uniformity.

[0060] After the gas activation is completed, the present invention may further include crushing the obtained gas-activated product to a particle size of 3-30 μm to obtain porous resin biomass carbon material. In the present invention, the crushing can be carried out using one or more of a jaw crusher, a roller crusher, and an air jet mill. In the present invention, the particle size of the porous resin biomass carbon material is 3-30 μm, specifically 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, or 30 μm.

[0061] The present invention also provides a porous resin biomass carbon material prepared by the preparation method described above, wherein the porous resin biomass carbon material has a specific surface area of ​​1500~3000 m². 2 / g, and can also be 2100~2400m 2 / g, which can be specifically 2113m 2 / g、2171m 2 / g、2193m 2 / g、2213m 2 / g、2213m 2 / g、2295m 2 / g、2339m 2 / g, or 2347m 2 / g; the pore size of the porous resin biomass carbon material is 0.5~50nm, and can also be 1~10nm, specifically 2.5nm; the total pore volume of the porous resin biomass carbon material is 0.6~1.0cm³. 3 / g, and can also be 0.9~0.92cm 3 / g, which can be specifically 0.901cm 3 / g, 0.903cm 3 / g, 0.906cm 3 / g, 0.908cm 3 / g, 0.909cm 3 / g, 0.91cm 3 / g, 0.912cm 3 / g or 0.92cm 3 / g; the proportion of pores with a size <0.6nm in the porous resin biomass carbon material can be 32~40%, specifically 32.1%, 35.1%, 36.1%, 36.7%, 37.3%, 37.5%, 38.8% or 39.5%.

[0062] In this invention, the X-ray diffraction (Cu-Kα) characteristic diffraction peaks of the porous resin biomass carbon material include 16~27° and 40~48°, specifically 21.5° and 44.0°; the peak intensity of 2θ=21.5° can be 500~900 au, the ratio of the peak intensity of 2θ=21.5° to that of 2θ=44.0° is 2.20~2.60, and the half-width at half-maximum of 2θ=21.5° can be 3.8~5.3°.

[0063] The present invention also provides the application of the porous resin biomass carbon material described in the above technical solution in the preparation of electrodes.

[0064] This invention provides a method for preparing a silicon-carbon composite material, comprising the following steps:

[0065] The porous resin biomass carbon material described in the above technical solution is subjected to chemical vapor deposition of silicon to obtain silicon-carbon material;

[0066] The silicon-carbon material is obtained by carbon coating.

[0067] This invention utilizes chemical vapor deposition (CVD) to deposit silicon into the porous resin biomass carbon material described in the above-mentioned technical solution, thereby obtaining silicon-carbon material. In this invention, the preferred conditions for the CVD include: the reaction gas may include silane and / or disilane; the dilution gas may include one or more of nitrogen, hydrogen, helium, and argon; the flow rate ratio of the reaction gas to the dilution gas may be 1:5~20, specifically 1:5, 1:8, 1:10, 1:12, 1:15, 1:18, or 1:20; the flow rate of the reaction gas may be 3~15 L / min, specifically 3 L / min, 5 L / min, 8 L / min, 10 L / min, 12 L / min, etc. The flow rate can be L / min or 15 L / min; the preheating temperature can be 300~400℃, specifically 300℃, 320℃, 340℃, 360℃, 380℃ or 400℃; the preheating time can be 5~9h, specifically 5h, 6h, 7h, 8h or 9h; the deposition temperature can be 400~600℃, specifically 400℃, 450℃, 500℃, 550℃ or 600℃; the deposition time can be 6~12h, specifically 6h, 7h, 8h, 9h, 10h, 11h or 12h. This invention performs vapor phase deposition on porous resin biomass carbon materials, which helps improve the high uniformity and surface stability of silicon-carbon materials, thereby reducing the expansion rate and electrolyte consumption rate during battery cell applications, and improving the electrochemical performance and stability of the battery.

[0068] After obtaining the silicon-carbon material, this invention performs carbon coating on the silicon-carbon to obtain a silicon-carbon composite material. In this invention, the carbon coating includes carbon coating the silicon-carbon material in a mixed gas. In this invention, the mixed gas may include a carrier gas and a carbon source gas; the carrier gas may include nitrogen; the carbon source gas may include one or more of methane, acetylene, propylene, and propane. In this invention, the carbon coating temperature can be 500~700℃, specifically 500℃, 550℃, 600℃, 650℃, or 700℃; the carbon coating time can be 4~10h, specifically 4h, 5h, 6h, 7h, 8h, 9h, or 10h. In this invention, the carbon coating can be carried out in a high-temperature reactor, including a pusher kiln, roller kiln, box furnace, or tube furnace.

[0069] This invention involves vapor-phase deposition of nano-silicon onto the porous resin biomass carbon material, which can effectively improve the energy density of lithium-ion batteries while also achieving low cost, high uniformity, and high stability, thus facilitating the commercialization of novel anode materials.

[0070] The present invention also provides a silicon-carbon composite material prepared by the preparation method described in the above technical solution.

[0071] This invention also provides the application of the silicon-carbon composite material described above as an electrode in a battery. In this invention, the battery can be a lithium-ion battery.

[0072] To further illustrate the present invention, the porous resin biomass carbon materials, their preparation methods and applications, and silicon-carbon composite materials, their preparation methods and applications provided by the present invention are described in detail below with reference to embodiments. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0073] The phenolic resin used in the following examples and comparative examples is the same, and the solvent in the 70% solids content water-soluble phenolic resin is water.

[0074] Example 1

[0075] (1) The coconut shell is crushed to 1~3mm by a combination of jaw crusher and roller crusher, and then put into a tube furnace for carbonization treatment at 600℃ for 3h to obtain coconut shell carbon.

[0076] (2) Coconut shell carbon and water-soluble phenolic resin with 70% solid content were added to a batch reactor at a mass ratio of 2:1 and dispersed at 600 r / min for 2 h. The resulting suspension was placed in a liquid phase reactor for hydrothermal composite (heated to 150°C at a heating rate of 8°C / min, pressurized to 3 MPa at a pressurization rate of 0.1 MPa / min, then kept at the temperature and pressure for 2 h, and then cooled and depressurized naturally for 12 h). The mixture was then transferred to a centrifuge and centrifuged at 3000 r / min for 20 min. Finally, it was vacuum dried at 80°C and 10 kPa for 12 h to obtain the resin-coconut shell carbon composite precursor.

[0077] (3) The resin coconut shell carbon composite precursor was put into a high temperature carbonization furnace, heated to 500℃ and carbonized for 3 hours, and then heated to 900℃ at a rate of 5℃ / min and carbonized for 4 hours to obtain resin coconut shell carbon.

[0078] (4) The resin coconut shell carbon is transferred to a pyrolysis rotary furnace, heated to 800°C at a rate of 10°C / min under N2 atmosphere and kept at the temperature for 6h, then heated to 1200°C at a rate of 5°C / min and kept at the temperature for 8h to obtain porous resin coconut shell carbon blocks, and then crushed to a particle size of 3~30μm using an air jet mill to obtain porous resin coconut shell carbon material.

[0079] Example 2

[0080] Porous resin coconut shell carbon material was prepared according to Example 1, the only difference from Example 1 being that the mass ratio of coconut shell carbon to liquid phenolic resin was 3:1.

[0081] Example 3

[0082] Porous resin coconut shell carbon material was prepared according to Example 1, the only difference from Example 1 being that the mass ratio of coconut shell carbon to liquid phenolic resin was 4:1.

[0083] Example 4

[0084] Porous resin coconut shell carbon material was prepared according to Example 1, the only difference from Example 1 being that the mass ratio of coconut shell carbon to liquid phenolic resin was 5:1.

[0085] Example 5

[0086] Porous resin coconut shell carbon material was prepared according to Example 1, the only difference from Example 1 being that the mass ratio of coconut shell carbon to liquid phenolic resin was 6:1.

[0087] Example 6

[0088] Porous resin coconut shell carbon material was prepared according to Example 1, the only difference from Example 1 being that the mass ratio of coconut shell carbon to liquid phenolic resin was 7:1.

[0089] Example 7

[0090] Porous resin coconut shell carbon material was prepared according to Example 1, the only difference from Example 1 being that the mass ratio of coconut shell carbon to liquid phenolic resin was 8:1.

[0091] Example 8

[0092] Porous resin coconut shell carbon material was prepared according to Example 1, the only difference from Example 1 being that the mass ratio of coconut shell carbon to liquid phenolic resin was 9:1.

[0093] Example 9

[0094] Porous resin coconut shell carbon material was prepared according to Example 1, the only difference from Example 1 being that the mass ratio of coconut shell carbon to liquid phenolic resin was 10:1.

[0095] Comparative Example 1

[0096] No liquid phenolic resin added

[0097] (1) After crushing the coconut shell to 1~3mm using a combination of jaw crusher and roller crusher, it is put into a tube furnace and carbonized at 600℃ for 3h. Then it is put into a high temperature carbonization furnace, first heated to 300℃ and then pre-carbonized for 3h, and then heated to 900℃ at a rate of 5℃ / min and then carbonized for 4h to obtain coconut shell carbon blocks.

[0098] (3) Transfer the coconut shell carbon block to a pyrolysis rotary furnace, heat it to 800℃ at a rate of 10℃ / min under N2 atmosphere and hold it for 6h, then heat it to 1200℃ at a rate of 5℃ / min and hold it for 8h to obtain porous coconut shell carbon block, and then use an air jet mill to crush it to a particle size of 3~30μm to obtain porous coconut shell carbon material.

[0099] Comparative Example 2

[0100] No coconut shell charcoal added

[0101] (1) Pure water-soluble phenolic resin with a solid content of 70% was pressurized and cured at 175℃ and 50MPa for 4h, then crushed to a particle size of 1~3mm, and then put into a tube furnace for pre-carbonization at 600℃ for 3h. Then it was put into a high-temperature carbonization furnace, heated to 300℃ and carbonized for 3h, and then heated to 900℃ at a rate of 5℃ / min and carbonized for 4h to obtain resin carbon.

[0102] (2) The resin carbon is processed according to step (2) of Comparative Example 1 to obtain porous resin carbon material.

[0103] Comparative Example 3

[0104] No liquid phenolic resin is added; activation is performed using chemical methods.

[0105] (1) Coconut shell carbon blocks prepared according to step (1) of Comparative Example 1.

[0106] (2) Mix coconut shell carbon blocks with potassium hydroxide solution (concentration 30wt%) at a dry weight ratio of 1:3, put them into a tube furnace, heat them to 1200℃ at a rate of 5℃ / min and then carbonize them for 4h to obtain porous coconut shell carbon blocks. Then, use an air jet mill to crush them to a particle size of 3~30μm to obtain porous coconut shell carbon material.

[0107] Comparative Example 4

[0108] Phenolic resin was dissolved in methanol, and coconut shell (particle size 1-3 mm) and pore-forming agent (ammonium bicarbonate) were added. After stirring for 12 h, the mixture was dried at 150 °C for 12 h, then ground to obtain a solid. The solid was placed in a tube furnace and heated to 1000 °C at a rate of 5 °C / min for 2 h under a flowing inert atmosphere of 150 mL / min. Then it was naturally cooled to room temperature to obtain porous carbon material. The volume ratio of dry weight of phenolic resin to methanol was 1 g: 30 mL; the mass ratio of dry weight of phenolic resin to coconut shell carbon to pore-forming agent was 1:4.3:1.2. The amount of coconut shell added was calculated according to step (1) of Example 1.

[0109] Test Example 1

[0110] The specific surface area, micropore size, and pore volume of the porous carbon materials prepared in the test examples and comparative examples were measured using an N2 adsorption-desorption surface area analyzer. The results are shown in Table 1.

[0111] Table 1. Pore structure parameters of porous carbon materials prepared in the examples and comparative examples.

[0112]

[0113] As shown in Table 1, the porous resin coconut shell carbon material prepared by this invention can maintain similar levels (specific surface area, pore volume, etc.) to porous carbon prepared by different single raw materials and different activation processes.

[0114] Compared with Comparative Example 3, the gas activation process used in this invention can significantly reduce the proportion of channels below 0.6 nm. Given that the lattice constant of the subsequently deposited nano-silicon is approximately 0.6 nm, it can be concluded that the channels of porous carbon below 0.6 nm can be considered as ineffective channels and cannot effectively disperse nano-silicon. In contrast, the porous carbon produced by Comparative Example 4 using ammonium bicarbonate has a low pore volume, a high proportion of micropores, a low specific surface area, and a high number of macropores. The resulting non-uniform channels are not conducive to the deposition of nano-Si. This indicates that the selection strategy of raw materials and preparation methods for the porous resin coconut shell carbon material in this invention can meet the application requirements of low cost, high efficiency, uniform dispersion, and high cost-effectiveness.

[0115] Application Example 1

[0116] Preparation of silicon-carbon composite materials

[0117] The porous carbon materials prepared in Examples 1-9 and Comparative Examples 1-3 were respectively fed into a vertical fluidized bed. While continuously introducing N2 atmosphere at a flow rate of 60 L / min, silane gas was continuously introduced at a flow rate of 7 L / min. The temperature was raised to 300°C at a rate of 5°C / min and held for 9 hours to allow the mixed gas to diffuse uniformly into the pores of the porous carbon material. The temperature was then raised to 500°C and chemical vapor deposition was performed for 12 hours to obtain silicon-carbon material with a silicon content of 50 wt%. After the deposition was completed and the temperature was cooled to 30°C, the silicon-carbon material was transferred to a carbon-coating rotary furnace. Under the atmosphere of acetylene and N2 mixed gas (acetylene flow rate 2 L / min, N2 flow rate 3 L / min), the furnace temperature was raised to 700°C and the silicon-carbon material was carbon-coated for 4 hours to obtain a silicon-carbon composite material.

[0118] Test Example 2

[0119] The silicon-carbon composite material prepared in Example 1 was used as the negative electrode to assemble lithium batteries. The battery assembly was carried out in a glove box with a water oxygen content of less than 0.1 ppm. Taking the CR2032 coin cell as an example:

[0120] Using the silicon-carbon composite materials prepared in Application Example 1 as active materials, conductive carbon black (Superp) and single-walled carbon nanotubes (SWCNTs) as conductive agents, and polyacrylic acid (PAA) as a binder, all raw materials were mixed evenly with deionized water as a solvent to obtain a slurry with a solid content of 40%. The slurry was coated onto a copper foil current collector to form the negative electrode, a lithium sheet was used as the counter electrode, Celgard 2500 was used as the separator, and a 1 mol / L LiPF6 solution (volume ratio EC:DMC:DEC=1:1:1, additionally containing 5 v / v% FEC) was used as the electrolyte to assemble a lithium-ion battery. The mass ratio of Superp, SWCNTs, and PAA was 1:0.1:3.

[0121] Electrochemical performance tests were conducted at a constant temperature of 25℃, with a test voltage range of 0.005~1.5V, and a constant rate charge-discharge test at 0.1C. The results are shown in Table 2.

[0122] Table 2. Test results of negative electrode performance in the examples and comparative examples.

[0123]

[0124] Table 2 shows that the coconut shell-based silicon-carbon material obtained by directly depositing nano-silicon onto porous coconut shell carbon prepared in Comparative Example 1 exhibits poor electrochemical cycling stability. This is due to the presence of numerous unstable macroporous defects in the prepared porous coconut shell carbon, which are detrimental to nano-silicon deposition and the cycling stability of the resulting material. The silicon-carbon anode obtained by depositing nano-silicon onto pure resin porous carbon in Comparative Example 2 does not exhibit the instability caused by biomass macroporous defects, and its cycling stability is strong. However, using pure phenolic resin as a raw material results in high costs. Comparative Example 3 is a silicon-carbon deposition material prepared from coconut shell porous carbon obtained by chemically activating the coconut shell carbon block prepared in Comparative Example 1. The silicon-carbon composite material prepared using the porous resin coconut shell carbon material of this invention exhibits superior electrochemical performance.

[0125] The specific capacity at 0.1C and cycling data at 1C in the table above indicate that this invention mainly solves the problem of improving the defects of porous carbon in coconut shells without increasing the cost basis. Furthermore, the process technology used can effectively improve the pore utilization rate of porous carbon (as seen in Comparative Examples 3 and 4, the material capacity is significantly lower when the same amount of nano-silicon deposition is designed, and some nano-silicon cannot enter the pores and cannot be deposited in the pores). This greatly reduces the impact of ineffective pores on electrolyte consumption (Comparative Example 3 has a low initial expansion due to the low amount of nano-silicon that can be loaded, but due to the high proportion of 0.6nm pores, the active lithium ion consumption rate is too fast, which deteriorates the cycle; while Comparative Example 4 has a high electrolyte consumption rate due to the combined effects of uneven pore size distribution and a high proportion of micropores, which leads to severe accelerated cycle decay). Therefore, the porous resin coconut shell carbon material prepared by this invention can effectively improve the problems of poor uniformity of nano-silicon deposition, insufficient deposition amount, and poor stability of deposition state. Under similar nano-silicon content, the capacity performance and cycling ability are effectively comparable to Comparative Example 2.

[0126] Test Example 3

[0127] Structural composition characterization

[0128] This invention utilizes the aforementioned porous resin to produce biocarbon while maintaining low cost. At the same time, an appropriate amount of resin can effectively modify the inherent macroporous defects of biomass porous carbon. In X-ray diffraction, there is a substantial difference in peak intensity between 16~27° and 40~48°, which reflects the relative proportion of macropores. Figure 1 The XRD patterns are of the porous resin coconut shell carbon material prepared in Example 1 and the porous coconut shell carbon material prepared in Comparative Example 1. As can be seen from the figures, the peak intensity at 2θ=21.5° in Comparative Example 1 reaches 966 au, the ratio of the peak intensity at 2θ=21.5° to that at 2θ=44.0° is 2.17, and the half-maximum width at 2θ=21.5° is 6.30°, indicating significant macroporous defects. In Example 1, after resin repair treatment of the same coconut shell carbon, the peak intensity decreased to 635 au, and the peak bulging degree between 16 and 27° was significantly reduced. The ratio of the peak intensity at 2θ=21.5° to that at 2θ=44.0° in Example 1 was 2.46, and the half-maximum width at 2θ=21.5° was 4.48°. This indicates that the macroporous characteristics of the coconut shell carbon body were significantly reduced, and the structure transitioned from a relatively balanced distribution of micropores, mesopores, and macropores to a more homogeneous porous carbon with micropores and mesopores as the main components and macropores as the secondary components. This greatly improved the uniformity of nano-silicon deposition. Therefore, under similar silicon content, Example 1 exhibited a relatively higher capacity at 0.1C room temperature and a lower expansion rate, which is also due to the benefits brought by the improved stability of the carbon skeleton.

[0129] Figure 2SEM images of the porous resin coconut shell carbon material prepared in Example 1 and the porous coconut shell carbon material prepared in Comparative Example 1 are shown. As can be seen from the images, Comparative Example 1 exhibits a significant macroporous structure under different magnification windows. The preparation method of this invention can effectively improve the macroporous structure, which is clearly evident in the different SEM images of Example 1. The silicon-carbon material obtained by vapor deposition using the porous carbon from Example 1 exhibits high uniformity and surface stability, thereby reducing the expansion rate and electrolyte consumption rate during battery cell application, and improving the electrochemical performance and stability of the battery.

[0130] Figure 3 The images show backscattered electron imaging (PRE) images of the porous resin coconut shell carbon material prepared in Example 1 and the porous coconut shell carbon material prepared in Comparative Example 1. As can be seen from the images, the porous coconut shell carbon material in Comparative Example 1, due to its numerous macropores, has a higher content of fine powder after air jet milling, resulting in poor uniformity of its vapor deposition. In contrast, Example 1, after modification with liquid phenolic resin, shows a reduction in macropores and a significant decrease in fine powder after the same air jet milling process. Simultaneously, the deposition uniformity is significantly improved, and the number of dark particles at the same 1.00K magnification is significantly reduced, indicating that the vast majority of the porous resin coconut shell carbon material particles are deposited with nano-silicon, consistent with the measured results of Example 1, such as improved capacity and relatively lower expansion rate.

[0131] Figure 4 The first-cycle electrical performance curve of the silicon-carbon composite material obtained in Application Example 1, together with Table 2, shows that the alkaline activation pore-forming method easily generates micropores, but the pore uniformity of the pore-forming agent is insufficient (high proportion of micropores, low pore volume). Therefore, the capacity performance after using it as a carbon substrate to deposit nano-Si is significantly low. This directly illustrates that the pore-forming method used in this invention has a positive effect on the utilization rate of pores and the carrying and adsorption of Si, thereby achieving the high capacity performance requirement.

[0132] In summary, the preparation method provided by this invention can effectively improve the monomeric structural defects of biomass coconut shell carbon by using an appropriate amount of resin modification without excessively increasing costs, thereby improving the uniformity of nano-silicon deposition by vapor deposition, reducing material expansion rate and improving cycle stability.

[0133] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a porous resin biomass carbon material, characterized by, Includes the following steps: Biomass char and liquid resin are mixed and hydrothermally composited to obtain a resin-biomass char composite precursor; the mass ratio of biomass char to liquid resin is 2~10:1; the hydrothermal composite includes a heating and pressurizing stage, a heat preservation and pressurizing stage, and a cooling and depressurizing stage; the heating and pressurizing stage has a heating rate of 5~10℃ / min and a pressurizing rate of 0.1~0.5MPa / min; the heat preservation and pressurizing stage has a temperature of 120~180℃, a pressure of 3~5MPa, and a time of 2~10h; the cooling and depressurizing stage lasts for 10~12h. The resin biomass carbon composite precursor is carbonized to obtain resin biomass carbon; the carbonization includes sequentially performing a first carbonization and a second carbonization; the temperature of the first carbonization is 300~500℃ and the holding time is 1~3h; the temperature of the second carbonization is 800~1000℃ and the holding time is 2~4h. The resin biomass carbon is subjected to gas activation to obtain porous resin biomass carbon material; the gas activation includes sequentially performing a first gas activation and a second gas activation; the temperature of the first gas activation is 500~800℃, and the holding time is 3~6h; the temperature of the second gas activation is 1000~1200℃, and the holding time is 5~8h.

2. The production method according to claim 1, characterized by, The method for preparing biomass carbon includes the following steps: pre-carbonizing biomass raw materials to obtain biomass carbon; The biomass raw materials include one or more of the following: coconut shells, camellia shells, wood, cellulose, straw, bamboo, walnut shells, sugar, and starch. The particle size of the biomass raw material is 1~3mm; The pre-carbonization temperature is 400~600℃, and the holding time is 1~3h.

3. The preparation method according to claim 1, characterized in that, The liquid resin includes one or more of water-soluble phenolic resin, water-soluble polyester resin, and water-soluble acrylic resin; the viscosity of the liquid resin is 0.2~0.9 Pa·s.

4. The production method according to claim 1, characterized by, The activating gas used in the gas activation includes one or more of carbon dioxide, water vapor, air, and oxygen.

5. A method for producing a silicon-carbon composite material, characterized by, Includes the following steps: Porous resin biomass carbon materials are prepared according to the preparation method described in any one of claims 1 to 4; Silicon was deposited onto the porous resin biomass carbon material via chemical vapor deposition to obtain silicon-carbon material. The silicon-carbon material is carbon-coated to obtain a silicon-carbon composite material.

6. The production method according to claim 5, wherein The conditions for chemical vapor deposition include: the reaction gas includes silane and / or silane, the dilution gas includes one or more of nitrogen, hydrogen, helium and argon, the preheating temperature is 300~400℃, the preheating time is 5~9h, the deposition temperature is 400~600℃, and the deposition time is 6~12h. The carbon coating process involves coating silicon-carbon materials with a mixed gas. The mixed gas includes a carrier gas and a carbon source gas. The carrier gas includes nitrogen, and the carbon source gas includes one or more of methane, acetylene, propylene, and propane. The carbon coating temperature is 500-700°C, and the time is 4-10 hours.

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