Porous carbon material, method for preparing the same, silicon-carbon material, and electrochemical device

Abstract

The application discloses a kind of porous carbon material and its preparation method, silicon-carbon material and electrochemical device, porous carbon material includes carbon nanotube and carbon material particle, the particle elastic modulus of porous carbon material is Y1, Y1 satisfies: 0.9Gpa≤Y1≤5.0Gpa.The porous carbon material of the application has high particle elastic modulus and high powder conductivity.When the porous carbon material in the application is used as framework, silicon-carbon material is prepared and applied in electrochemical device, can make silicon-carbon material have higher particle elastic modulus and powder conductivity, improve the long cycle performance, rate performance and other electrochemical properties of electrochemical device.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a porous carbon material and its preparation method, a silicon-carbon material, and an electrochemical device. Background Technology

[0002] Porous materials are materials with a network structure consisting of interconnected or closed pores. They have strong adsorption properties and have been widely used in fields such as gas purification, gas separation, and wastewater treatment. They are also widely used in industrial production and people's daily lives.

[0003] Porous carbon materials, as a type of porous material, have been widely studied due to their advantages such as wide availability, low cost, and ease of preparation. However, the specific surface area and pore size structure of porous carbon materials applied in different fields often vary significantly, making it difficult to balance the specific surface area, pore volume characteristics, and particle elastic modulus properties of porous carbon materials. Summary of the Invention

[0004] This application provides a porous carbon material, its preparation method, and its uses. The porous carbon material has a significantly improved particle elastic modulus.

[0005] In a first aspect, this application provides a porous carbon material, comprising carbon nanotubes and carbon material particles, wherein the elastic modulus of the porous carbon material particles is Y1, and Y1 satisfies: 0.9 GPa≤Y1≤5.0 GPa.

[0006] In some exemplary embodiments, the diameter of the carbon nanotube is L1, where L1 satisfies: 0.005μm≤L1≤0.05μm.

[0007] In some exemplary embodiments, the carbon material particles satisfy at least one of the following conditions:

[0008] (1) The sphericity of the carbon material particles is D, and D satisfies: 0.4≤D≤0.99;

[0009] (2) The particle size Dv50 of the carbon material particles satisfies: 1μm≤Dv50≤20μm.

[0010] In some exemplary embodiments, the specific surface area of ​​the porous carbon material is ε, where ε satisfies: 1300 m² / s². 2 / g≤ε≤2800 m 2 / g.

[0011] In some exemplary embodiments, the total pore volume of the porous carbon material is P0cm. 3 / g, the pore volume of the porous carbon material with a pore size <2 nm is P1 cm. 3 / g, the pore volume of the porous carbon material with a pore size <1 nm is P2 cm.3 / g, wherein P0, P1, and P2 are pore volumes calculated at a single point; the porous carbon material satisfies at least one of the following conditions:

[0012] (1) 0.5 ≤ P0 ≤ 2.0;

[0013] (2) 0.7 ≤ P1 / P0 ≤ 0.99;

[0014] (3) 0.05≤P2 / P0≤0.5.

[0015] In some exemplary embodiments, the porous carbon material satisfies at least one of the following conditions:

[0016] (1) 0.4 ≤ P1 ≤ 1.3;

[0017] (2) 0.01≤P2≤0.6.

[0018] In some exemplary embodiments, the powder conductivity of the porous carbon material at a pressure of 130 MPa is ρ, where ρ satisfies: 3 S / cm ≤ ρ ≤ 30 S / cm.

[0019] In some exemplary embodiments, the number of pores in the cross-section of a single porous carbon material particle is m, where 0 ≤ m ≤ 3; the diameter of the pores in the cross-section of a single porous carbon material particle is H, where H satisfies: 100 nm < H < 2000 nm.

[0020] In some exemplary embodiments, when the porous carbon material is observed by scanning electron microscopy, the single carbon nanotube passes through no more than 4 carbon material particles in a 50 μm × 50 μm area, and the number of carbon nanotubes present in a single carbon material particle is 1 to 10.

[0021] Secondly, this application provides a method for preparing porous carbon materials, including,

[0022] Carbon nanotubes, carbon material precursors and curing agents are mixed evenly according to a preset mass ratio, and heated to the first reaction temperature T1 in a first protective atmosphere for programmed curing to obtain a mixed precursor.

[0023] The mixed precursor is carbonized at a second reaction temperature T2 and in a second protective atmosphere to obtain a carbonized pretreated product.

[0024] After the carbonized pretreatment material is crushed and sieved, it is activated at a third reaction temperature T3 and in a third protective atmosphere to obtain the porous carbon material.

[0025] The particle elastic modulus of the porous carbon material is Y1, which satisfies: 0.9 GPa≤Y1≤5.0 GPa.

[0026] In some exemplary embodiments, the preset mass ratio is: the mass percentage C of the carbon nanotubes in the mixed precursor, where C satisfies: 1% ≤ C ≤ 6%.

[0027] In some exemplary embodiments, the carbon material precursor includes one or more of epoxy resin, phenolic resin, melamine resin, polyaniline, polyacrylonitrile, polyvinylidene chloride, pitch, coal tar, bisphenol A, and hexamethylenetetramine.

[0028] In some exemplary embodiments, the program solidification process includes:

[0029] The multi-step heating and curing process includes heating at a rate of 2 to 5°C / min to 80°C, heating at a rate of 1 to 3°C / min to 100°C, and holding at that temperature for a first holding time t. y Then, the temperature is increased to the first reaction temperature T1 at a rate of 1~3℃ / min, and held at that temperature for a first time t1.

[0030] In some exemplary embodiments, the first reaction temperature T1 satisfies: 100℃ ≤ T1 ≤ 200℃; the time for the programmed curing process is a first time t1, where t1 satisfies: 8h ≤ t1 ≤ 12h; and / or,

[0031] The second reaction temperature T2 satisfies: 900℃ ≤ T2 ≤ 1300℃; the carbonization time is the second time t2, which satisfies: 1h ≤ t2 ≤ 4h; and / or,

[0032] The third reaction temperature T3 satisfies: 900℃≤T3≤1000℃; the activation time is the third time t3, which satisfies: 10h≤t3≤14h.

[0033] In some exemplary embodiments, the first protective atmosphere is an oxygen / nitrogen mixture, wherein the oxygen content is 10-20%; and / or,

[0034] The second protective atmosphere is one of nitrogen and argon; and / or,

[0035] The third protective atmosphere is one of carbon dioxide, carbon dioxide / nitrogen, and water vapor / carbon dioxide, wherein carbon dioxide gas accounts for 50% to 100%.

[0036] Thirdly, this application provides a silicon-carbon material, which is a porous carbon material as described above; and / or includes any porous carbon material prepared by the preparation method described above.

[0037] Fourthly, this application provides an electrochemical device including a positive electrode, an electrolyte, a membrane, and a negative electrode, wherein the negative electrode includes a current collector and a negative electrode active material layer, and the negative electrode active material layer includes the silicon-carbon material as described above.

[0038] The porous carbon material, silicon carbide material, and electrochemical device based on the embodiments of this application have at least the following beneficial effects:

[0039] The porous carbon material prepared in this application has a high specific surface area, a uniform pore size distribution, and also has a high particle elastic modulus and high powder electrical conductivity.

[0040] Using the porous carbon material in this application as a framework, when silicon-carbon materials are prepared and applied to electrochemical devices, the silicon-carbon materials can have higher particle elastic modulus and powder conductivity, thereby improving the electrochemical performance of the electrochemical device, such as long-cycle performance and rate performance. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0042] Figure 1a Scanning electron microscope (SEM) images of the cross-sectional areas of the porous carbon materials prepared in Examples 1-8;

[0043] Figure 1b Scanning electron microscope (SEM) images of the cross-sectional areas of the porous carbon materials prepared in Examples 1-9;

[0044] Figure 2 X-ray diffraction patterns of the porous carbon materials prepared in Examples 1-8;

[0045] Figure 3 Nitrogen adsorption-desorption test curves for the porous carbon materials prepared in Examples 1-8;

[0046] Figure 4 Pore ​​size-cumulative pore volume distribution curves for the porous carbon materials prepared in Comparative Examples 1-8;

[0047] Figure 5 Nitrogen adsorption-desorption test curves for the porous carbon materials prepared in Examples 1-21;

[0048] Figure 6 Pore ​​size-cumulative pore volume distribution curves for the porous carbon materials prepared for comparative examples 1-21. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0050] This application provides a porous carbon material comprising carbon nanotubes and carbon material particles. The elastic modulus of the porous carbon material particles is Y1, where Y1 satisfies: 1.0 GPa ≤ Y1 ≤ 5.0 GPa. Preferably, Y1 satisfies: 0.5 GPa ≤ Y1 ≤ 2.0 GPa. In this porous carbon material, carbon nanotubes are mainly interwoven within the carbon material particles, forming a microscopic interpenetrating network structure, which helps to improve the elastic modulus of the porous carbon material particles.

[0051] The porous carbon material of this application embodiment has a small number of carbon nanotubes on the surface of the porous carbon material, and the carbon nanotubes and carbon material particles form an interpenetrating network structure. This makes it easy to select carbon material particles with suitable pore structures and carbon nanotubes for composite, thereby helping to obtain porous carbon materials with high toughness, no obvious large pores in the cross section and uniform pore size distribution, which are suitable for use in electrochemical devices to improve the energy storage of electrochemical devices.

[0052] In some exemplary embodiments, the powder conductivity of the porous carbon material at a pressure of 130 MPa is ρ, where ρ satisfies: 1 S / cm ≤ ρ ≤ 30 S / cm; preferably, ρ satisfies: 5 S / cm ≤ ρ ≤ 20 S / cm.

[0053] In some exemplary embodiments, the diameter of the carbon nanotubes is L1, where L1 satisfies: 0.005 μm ≤ L1 ≤ 0.05 μm. A carbon nanotube diameter within this range contributes to the uniform distribution of carbon nanotubes, enabling the porous carbon material to achieve a suitable specific surface area and pore volume, while simultaneously improving the powder conductivity and particle strength of the porous carbon material, thereby enhancing the powder conductivity and particle strength of the silicon-carbon material.

[0054] In some exemplary embodiments, the diameter of the porous carbon material is L2, where L2 is statistically represented by the particle size Dv50 of the carbon material particles, wherein the particle size Dv50 satisfies: 1μm ≤ Dv50 ≤ 20μm. When the particle size Dv50 of the carbon material particles is within this range, it helps to shorten the silicon deposition path. When silicon-carbon materials prepared from porous carbon materials are applied in electrochemical devices, they can improve the uniformity of dispersion during the negative electrode slurry preparation process, improve the uniformity of silicon deposition, reduce the volume expansion of silicon-carbon materials, and enhance the rate performance of the electrochemical device.

[0055] In some exemplary embodiments, the sphericity of the carbon material particles is D, where D satisfies: 0.4 ≤ D ≤ 0.99. When porous carbon materials are closer to a spherical shape, they facilitate gas adsorption. When porous carbon materials are used to prepare silicon-carbon materials and applied to electrochemical devices, they can improve the uniform deposition of silicon. The spherical structure is also more conducive to releasing stress during the charging and discharging process of the electrochemical device, thereby improving the long-cycle performance of the electrochemical device.

[0056] In some exemplary embodiments, the specific surface area of ​​the porous carbon material is ε, where ε satisfies: 1300 m² / s². 2 / g≤ε≤2800 m 2 / g. Within this range, the specific surface area of ​​porous carbon materials can be further improved, which can enhance the powder conductivity and particle strength of porous carbon materials and help obtain silicon-carbon materials with high silicon deposition.

[0057] In some exemplary embodiments, the total pore volume of the porous carbon material calculated at a single point is P0cm. 3 / g, P0 satisfies: 0.5≤P0≤2.0. A total pore volume within this range helps porous carbon materials achieve high powder conductivity and particle strength, facilitates the production of silicon-carbon materials with high silicon deposition, and simultaneously mitigates volume expansion during the charging and discharging process of silicon-carbon electrochemical devices.

[0058] In some exemplary embodiments, the porous carbon material includes a first pore with a pore size of S1, where S1 < 2 nm. The pore volume of the first pore, calculated at a single point, is P1 cm³. 3 / g, P0 and P1 satisfy: 0.7≤P1 / P0≤0.99. Further, 0.4≤P1≤1.3. A P1 value within this range for porous carbon materials helps improve particle toughness and strength, and mitigates volume expansion of silicon-carbon materials during the charging and discharging process of electrochemical devices.

[0059] In some exemplary embodiments, the first hole includes a second hole with a diameter of S2, where S2 < 1 nm. The pore volume of the second hole, calculated at a single point, is P2 cm. 3 / g, P0 and P2 satisfy: 0.05≤P2 / P0≤0.5. Further, 0.01≤P2≤0.6. A P2 value within this range for porous carbon materials helps improve silicon deposition in silicon-carbon materials, thereby enhancing the electrochemical performance of silicon-carbon materials for lithium storage.

[0060] In some exemplary embodiments, the number of pores in the cross-section of a single composite particle of porous carbon material is 0, which can further improve the particle strength and powder conductivity.

[0061] In some exemplary embodiments, the number of pores in the cross-section of a single composite particle of porous carbon material is m, where 0 < m ≤ 3; the diameter of the pores in the cross-section of a single composite particle of porous carbon material is H, where H satisfies: 100 nm < H < 2000 nm. This can further ensure the particle strength and powder conductivity, and can also further alleviate the volume expansion of silicon-carbon materials during the charging and discharging process of electrochemical devices.

[0062] Scanning electron microscopy (SEM) images of porous carbon materials show that within a 50 μm × 50 μm region, the number of carbon particles through which a single carbon nanotube passes is denoted as A, where A ≤ 4. This means the end of the carbon nanotube is on the surface of the carbon particle, including cases where the end of the carbon nanotube extends to or beyond the surface of the carbon particle (e.g., one end of the carbon nanotube is on the surface of the carbon particle); or, the carbon nanotube penetrates the entire carbon particle, meaning both ends of the carbon nanotube are on the surface of the carbon particle. The number of carbon nanotubes simultaneously present in a single carbon particle is denoted as B, where B ≤ 1 ≤ B ≤ 10. This includes cases where the carbon nanotube is completely encapsulated by the single carbon particle; or, one end of the single carbon nanotube is encapsulated by the single carbon particle, and the other end is on the surface of the carbon particle; or, the middle portion of the single carbon nanotube is encapsulated by the single carbon particle, and both ends are on the surface of the carbon particle.

[0063] This application also provides a method for preparing porous carbon materials, including:

[0064] Step S201: Mix carbon nanotubes, carbon material precursor and curing agent evenly according to a preset mass ratio, and heat to the first reaction temperature T1 in a first protective atmosphere to carry out programmed curing treatment to obtain mixed precursor.

[0065] Step S202: The mixed precursor is carbonized at the second reaction temperature T2 and in the second protective atmosphere to obtain the carbonized pretreated product.

[0066] Step S203: After crushing and sieving the carbonized pretreated material, it is activated at the third reaction temperature T3 and in the third protective atmosphere to obtain porous carbon material. The porous carbon material is electrically conductive, and the particle elastic modulus of the porous carbon material is Y1, where Y1 satisfies: 0.9 GPa ≤ Y1 ≤ 5.0 GPa.

[0067] The porous carbon material preparation method of this application embodiment involves uniformly mixing raw materials containing carbon nanotube precursors, and controlling the curing and activation processes to obtain porous carbon materials with high powder conductivity, high toughness, and no obvious large pores in the cross-section. This results in a smaller number of carbon nanotubes on the surface of the porous carbon material, and the carbon nanotubes and carbon material particles form an interpenetrating network structure. This facilitates the selection of carbon nanotubes with suitable pore structures for composite with carbon material particles, thereby helping to obtain porous carbon materials with high toughness, no obvious large pores in the cross-section, and uniform pore size distribution. These materials are suitable for gas storage and for application in electrochemical devices to improve the energy storage capacity of electrochemical devices.

[0068] In step S201, the first reaction temperature T1 satisfies: 100℃≤T1≤200℃; the time for the programmed curing process is the first time t1, which satisfies: 8h≤t1≤12h. When the first reaction temperature and the first reaction time are within the above ranges, it ensures complete curing of the mixed precursor, prevents the generation of obvious bubbles during curing, and results in high strength of the cured mixed precursor, which helps to obtain porous carbon materials with high particle strength.

[0069] In step S202, the second reaction temperature T2 satisfies: 900℃≤T2≤1300℃; the carbonization time is the second time t2, which satisfies: 1h≤t2≤4h. ... With the second reaction temperature and the second reaction time within the above ranges, sufficient carbonization of the mixed precursor can be ensured, resulting in porous carbon materials with high powder conductivity.

[0070] In step S203, the third reaction temperature T3 satisfies: 900℃≤T3≤1000℃; the activation time is the third time t3, which satisfies: 10h≤t3≤14h. The fact that the third reaction temperature and third reaction time are within the above ranges helps to obtain porous carbon materials with high specific surface area and pore volume while ensuring that the porous carbon materials have high particle strength and powder conductivity, thereby obtaining silicon-carbon materials with high capacity and low expansion.

[0071] The curing process includes a multi-step temperature increase curing process, which involves increasing the temperature from 2℃ / min to 5℃ / min to 80℃, then increasing it from 1℃ / min to 3℃ / min to 100℃, followed by a first holding time t. y The temperature is then increased from 1℃ / min to 3℃ / min to the first reaction temperature T1, and held at this temperature for a first time t1. Where t... y Satisfy: 60 min ≤ t y ≤180 min. By adopting a gradual heating method, the uniformity of the pore size of the prepared porous carbon material can be improved.

[0072] The first protective atmosphere, the second protective atmosphere, and the third protective atmosphere may each be independently at least one of an inert gas and nitrogen.

[0073] In some exemplary embodiments, the preset mass ratio is: the mass percentage C of carbon nanotubes to the mass of the mixed precursor, where C satisfies: 1%≤C≤6%. This helps to improve the particle elastic modulus and conductivity of the prepared porous carbon material.

[0074] Carbon material precursors include one or more of the following: epoxy resin, phenolic resin, melamine resin, polyaniline, polyacrylonitrile, polyvinylidene chloride, pitch, coal tar, bisphenol A, and hexamethylenetetramine.

[0075] The curing agent includes one or more of HMT, urea, and melamine.

[0076] The porous carbon material prepared in this application has a high specific surface area, a uniform pore size distribution, and also has a high particle elastic modulus and high powder electrical conductivity.

[0077] Using the porous carbon material in this application as a framework, when silicon-carbon materials are prepared and applied to electrochemical devices, the silicon-carbon materials can have higher particle elastic modulus and powder conductivity, thereby improving the electrochemical performance of the electrochemical device, such as improving the long-cycle performance and rate performance of the electrochemical device.

[0078] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0079] I. The performance testing methods for porous carbon materials are as follows:

[0080] 1. Test of the elastic modulus of porous carbon materials

[0081] The hardness and elastic modulus of individual particles of porous carbon material were tested using a nanoindenter (Hysitron TI 950), according to the JB / T 12721-2016 standard. Before testing, the powder was dispersed in epoxy resin and cured. The cured resin was then cut using ion polishing. A nanoindenter was used to apply pressure to individual particles of the porous carbon material, and the indentation depth on the particle surface was monitored. The strength of each individual particle was then calculated. The elastic modulus of five particles from the same sample were tested in parallel, and the average value was taken.

[0082] 2. Electrical conductivity testing of porous carbon materials

[0083] The conductivity of porous carbon material solid powder was tested using a powder conductivity meter (model FT-8100) based on the four-probe testing principle, referring to standard GB / T1552-1995. A known amount of porous carbon material solid powder was used, and its volume was compressed to a set pressure value or intensity under hydraulic power. The resistance, resistivity, and conductivity of the porous carbon material solid powder were measured online, and the data were recorded.

[0084] 3. Particle size testing of porous carbon materials and carbon material particles.

[0085] The particle size of porous carbon material powder was tested using a Malvern particle size analyzer: the powder material was dispersed in ethanol dispersant, sonicated for 30 minutes, and then the sample was added into the Malvern particle size analyzer to test the Dv50 of the powder material.

[0086] 4. Test of particle sphericity of porous carbon materials

[0087] The sphericity of porous carbon material solid powder was analyzed using a laser particle size analyzer (model BT-2900) based on the analytical method of GB / T38887-2020. Electromagnetic vibration injection and free-fall dispersion techniques were employed to disperse the porous carbon material solid powder. The particle sphericity was then output using a high-speed CCD camera and image processing software with multi-threading and edge recognition technology.

[0088] 5. Carbon nanotube inner diameter test

[0089] The inner diameter of carbon nanotubes was analyzed using a transmission electron microscope (FEI Tecnai F20): porous carbon material solid powder was dispersed in ethanol dispersant, sonicated for 30 minutes, and a small amount of dispersion was taken with a pipette and dropped onto a grating. The grating was then placed into the transmission electron microscope to test the average inner diameter of the carbon nanotubes in the porous carbon material.

[0090] 6. Specific surface area and pore volume test

[0091] Solid powder of porous carbon material was placed in a sample tube and degassed under vacuum at 100℃ for 12 hours. The adsorption capacity of the porous carbon material for nitrogen under different pressures was measured using an ASAP1460 physical adsorption analyzer, and adsorption and desorption isotherms were plotted. The pore shape was determined based on the shape of the hysteresis loop, and the pore size distribution curve of the micropores was fitted using a DFT model. The specific surface area, pore volume, and pore size distribution of the porous carbon material were then calculated.

[0092] Example 1-1

[0093] The preparation method of porous carbon materials is as follows:

[0094] Linear phenolic resin, hexamethylenetetramine (HMT), and carbon nanotubes (CNTs) in a mass ratio of 94:6:2 were placed in a ball mill jar and ball-milled until completely dispersed to obtain the precursor material. The precursor material was then placed in a programmed curing oven under a first protective atmosphere (an oxygen / nitrogen mixture, with oxygen comprising 10%) for programmed curing treatment. The temperature was increased to 80℃ at 5℃ / min, then increased to 100℃ at 2℃ / min, and held at this temperature for a first holding time t. y1 (t) y1 =1h), then the temperature was increased to the first reaction temperature T1 (T1=130℃) at 1℃ / min, and the reaction was carried out at the first reaction temperature for a first time t1 (t1=10h). After cooling, the mixture was broken down to obtain the mixed precursor. The diameter of the carbon nanotubes L1 is 0.01μm.

[0095] The mixed precursors were placed in a box furnace under a second protective atmosphere (nitrogen) and heated to a second reaction temperature T2 (T2=900℃) at a heating rate of 5℃ / min. The mixture was then subjected to carbonization treatment for a second time t2 (t2=2h) at the second reaction temperature T2. After cooling, the carbonized pretreated product was obtained.

[0096] The carbonized pretreated material is crushed to obtain powder, which is then sieved and classified according to particle size. The particle size D of the powder is determined. v The particle size was controlled at 18 μm. The graded powder was then transferred to a rotary kiln under nitrogen atmosphere protection and heated to the third reaction temperature T3 (T3=900℃) at a heating rate of 5℃ / min. The gas atmosphere was then changed to the third protective atmosphere (carbon dioxide). After activation time t3 (t3=10h), the carbon dioxide was removed and replaced with nitrogen. After cooling to room temperature (25℃), a porous carbon material was obtained. The sphericity D of the porous carbon material was 0.4, and the diameter L2 of the porous carbon material was 18 μm.

[0097] Examples 1-1 to Examples 1-6

[0098] Except for adjusting the preparation parameters of the porous carbon material according to Table a, the rest is the same as in Example 1-1.

[0099] Table a

[0100]

[0101] Examples 1-7 to Examples 1-12

[0102] Except for adjusting the preparation parameters of the porous carbon material according to Table b, the rest is the same as in Examples 1-4.

[0103] Table b

[0104]

[0105] Examples 1-13

[0106] The preparation method of porous carbon materials is as follows:

[0107] Bisphenol A, hexamethylenetetramine (HMT), and carbon nanotubes (CNTs) in a mass ratio of 90:10:4 were placed in a ball mill jar and ball-milled until completely dispersed to obtain the precursor material. The precursor material was then placed in a programmed curing oven under a first protective atmosphere (nitrogen) for programmed curing treatment. The temperature was increased to 80℃ at 5℃ / min, then increased to 100℃ at 2℃ / min, and held at this temperature for a first holding time t. y1 (t) y1 =1h), the temperature is increased to the first reaction temperature T1 (T1=180℃) at a heating rate of 1℃ / min, and reacted at the first reaction temperature for a first time t1 (t1=10h) for programmed solidification. After cooling, the mixture is broken down to obtain the mixed precursor. The diameter of the carbon nanotubes L1 is 0.01μm.

[0108] The mixed precursors were placed in a box furnace under a second protective atmosphere (nitrogen) and heated to a second reaction temperature T2 (T2=900℃) at a heating rate of 5℃ / min. The mixture was then subjected to carbonization treatment for a second time t2 (t2=2h) at the second reaction temperature T2. After cooling, the carbonized pretreated product was obtained.

[0109] The carbonized pretreated material is crushed to obtain powder, which is then sieved and classified according to particle size. The particle size D of the powder is determined. v The particle size was controlled at 15 μm. The graded powder was then transferred to a rotary kiln under nitrogen atmosphere protection and heated to the third reaction temperature T3 (T3=950℃) at a heating rate of 5℃ / min. The gas atmosphere was then changed to the third protective atmosphere (carbon dioxide). After activation time t3 (t3=10h), the carbon dioxide was removed and replaced with nitrogen. After cooling to room temperature (25℃), porous carbon material was obtained. The sphericity D of the porous carbon material was 0.6, and the diameter L2 of the carbon material particles was 15 μm.

[0110] Examples 1-14 to Examples 1-23

[0111] Except for adjusting the preparation parameters of the porous carbon material according to Table c, T1=150℃ in the preparation process of Examples 1-22 and T1=120℃ in the preparation process of Examples 1-23, the rest are the same as in Examples 1-13.

[0112] Table c

[0113]

[0114] Comparative Example 1-1

[0115] Examples 1-1 include: the mixed precursor does not include carbon nanotubes (CNTs).

[0116] Comparative Examples 1-2

[0117] Except for using coconut shells instead of the precursor material used in Example 1-1 to prepare porous carbon materials, the rest is the same as in Example 1-1.

[0118] Comparative Examples 1-3

[0119] Except for replacing the precursor material used in Example 1-1 with asphalt to prepare porous carbon materials, the rest is the same as in Example 1-1.

[0120] Examples 2-1 to 2-5

[0121] Except for adjusting the diameter L2 (Dv50) and sphericity D of the porous carbon material particles, the rest is the same as in Examples 1-5.

[0122] The test data for each embodiment and comparative example are shown in Tables 1-4.

[0123] Table 1

[0124]

[0125] Referring to Table 1, it can be seen from Examples 1-1 to 1-3, Comparative Example 1, and Comparative Example 2 that the introduction of CNTs helps to improve the elastic modulus of the particles and the electrical conductivity of the particle powder. It can be seen from Examples 1-2, 1-4 to 1-6, Comparative Example 1, and Comparative Example 2 that the ratio of the first carbon material, the curing agent, and CNTs has a significant impact on the structure of the porous carbon material, manifested in changes in specific surface area, pore volume, powder electrical conductivity, and particle elastic modulus.

[0126] In this process, the curing agent reacts chemically with the carbon material precursor to form a stable cross-linked polymer. This significantly improves the residual carbon content and skeletal strength of porous carbon materials. The curing agent also acts as a pore-forming agent, optimizing the pore structure and improving the specific surface area and pore volume of porous carbon materials. Increasing the amount of curing agent helps to increase the specific surface area ε and pore volume of porous carbon materials, with the pore volume improvement mainly reflected in 1nm~2nm pores and mesopores (pores with a diameter greater than 2nm). Furthermore, using a resin system in combination with the curing agent can control the proportion of micropores (pores with a diameter less than 2nm) in porous carbon materials to be greater than 80%, with a narrow pore size distribution and most being micropores, far exceeding the performance of porous carbon materials prepared solely from pitch or bio-based materials.

[0127] The introduction of CNTs also changes the curing process and affects the pore structure. As can be seen from Examples 1-1 to 1-3 and Comparative Example 1, when the mass percentage of carbon nanotubes in the mixed precursor C satisfies 1%≤C≤6%, the powder conductivity ρ and particle elastic modulus Y1 of the porous carbon material are greatly improved.

[0128] Table 2

[0129]

[0130] Referring to Table 2, it can be seen from Examples 1-7 to 1-12 that the second reaction temperature T2, the third reaction temperature T3, and the third reaction time t3 have a significant impact on the specific surface area ε, pore volume, powder conductivity, and particle elastic modulus of the porous carbon material. When the second reaction temperature T2 increases, the particle elastic modulus Y1 and powder conductivity ρ of the porous carbon material increase significantly, mainly due to the increased pyrolysis and graphitization degree of the porous carbon material. When the third reaction temperature T3 increases, the specific surface area ε and pore volume of the porous carbon material increase, primarily due to the increased pore volume of the mesopores (pores with a diameter greater than 2 nm). When the third reaction time t3 is prolonged, the specific surface area ε and pore volume of the porous carbon material increase, mainly due to the increased pore volume of 1 nm to 2 nm pores and mesopores (pores with a diameter greater than 2 nm).

[0131] Table 3

[0132]

[0133] Referring to Table 3, from Examples 1-13 to 1-23, it can be seen that changing the mixed precursor has a significant impact on the structure of the porous carbon material, and the suitable first reaction temperature T1 also varies for different mixed precursors. When the precursor contains materials such as polyacrylonitrile, polyvinylidene chloride, and pitch, the sphericity D of the porous carbon material increases significantly after heat treatment, becoming closer to a sphere. The proportion of micropores (pores with a diameter of less than or equal to 2 nm, i.e., the first pore) in the porous carbon material is all above 80%. Among these, the closer the porous carbon material is to a sphere, and the increased proportion of micropores can help with gas adsorption and uniform silicon deposition. The spherical structure is also more conducive to releasing stress during the charging and discharging process of the electrochemical device.

[0134] Table 4

[0135]

[0136] Referring to Table 4, it can be seen from Examples 1-4 and Examples 2-1 to 2-2 that controlling the sphericity D of the porous carbon material particles to be the same, and reducing the particle diameter L2 (statistically based on Dv50), will increase the particle elastic modulus Y1, increase the interparticle gaps, and increase the specific surface area ε. However, the powder conductivity ρ of the particles will decrease. Preferably, 9μm≤L2≤12μm. From Examples 1-4 and Examples 2-3 to 2-5, it can be seen that controlling the particle diameter L2 of the porous carbon material to be the same, and adjusting the particle sphericity D, it can be seen that as the particle sphericity D increases, the specific surface area ε of the particles becomes similar. However, because spherical shape can better relieve stress, the contact between particles is tighter, and the particle strength Y1 and powder conductivity ρ increase. Preferably, 0.7≤D≤0.9.

[0137] In summary, the porous carbon material provided in this application contains carbon nanotubes (CNTs) in its porous framework, exhibiting a stable framework structure and higher conductivity. When the particle size, sphericity, specific surface area, and pore volume of the porous carbon material are within the range of this application, the particle elastic modulus and powder conductivity of the porous carbon material can be further improved, and the pore size distribution can be more uniform (the larger the P1 / P0 value, the more uniform the pore size distribution of the porous carbon material). When silicon-carbon materials including the porous carbon material of this application are applied in electrochemical devices, the negative electrode active material will have higher specific capacity and lower volume expansion.

[0138] Figure 1a The following are scanning electron microscope (SEM) images of the cross-sectional areas of the porous carbon materials prepared in Examples 1-8. Figure 1a The structure at point A represents the through-holes in the cross-section of the particles formed by CNTs. The diameter of these through-holes is between 0.005 μm and 0.05 μm, and the number of through-holes is no more than 10. There are no openings in the cross-section of the particles with a diameter greater than 100 nm, indicating that CNTs are dispersed inside the porous carbon material and can enhance the framework of the porous carbon material. Figure 1b The following are scanning electron microscope (SEM) images of the cross-sectional areas of the porous carbon materials prepared in Examples 1-9. Figure 1b The pores at point B are larger than 100 nm in diameter. The number of pores larger than 100 nm in diameter on the particle surface is no more than 3, which helps to further improve the particle strength of porous carbon. Figure 2 The XRD (X-ray diffraction) patterns of the porous carbon materials prepared in Examples 1-8 are shown, as follows: Figure 3 As shown, the peak near 26° is the characteristic peak corresponding to carbon nanotubes, and the broad peaks near 23~26° and 43° are the characteristic peaks corresponding to carbon material particles.

[0139] Figure 3The isothermal adsorption-desorption curves of the porous carbon materials prepared in Examples 1-8 are shown. It can be seen that the material exhibits significant gas adsorption in the low-pressure region with relatively low pressure, indicating that the material is predominantly composed of micropores (pores with a diameter less than or equal to 2 nm, i.e., the first pore). The adsorption-desorption curves do not show obvious hysteresis loops, indicating that there is no obvious mesopore distribution (pores with a diameter greater than 2 nm) within the material. The specific surface area of ​​the porous carbon material, fitted by the adsorption-desorption test curves, is 1780 m². 2 / g, the total pore volume calculated at a single point is 0.72 cm³. 3 / g.

[0140] Figure 4 The pore size-cumulative pore volume curves of the porous carbon materials prepared in Examples 1-8 are shown. It can be seen that, corresponding to the nitrogen adsorption-desorption curves, the pore size distribution of the porous carbon materials is mainly concentrated in the micropore region, with the pore volume of pores smaller than 2 nm being 0.68 cm³. 3 / g, accounting for 94% of the total pore volume, with pores smaller than 1nm having a pore volume of 0.31cm³. 3 / g, accounting for 42% of the total pore volume.

[0141] Figure 5 The isothermal adsorption-desorption curves of the porous carbon materials prepared in Examples 1-21 are shown. It can be seen that significant gas adsorption exists in the low-pressure region, indicating that the porous carbon materials are predominantly micropores. In the adsorption-desorption curves, no gas adsorption occurs at relative pressures greater than 0.2, indicating that mesopores (pores with a diameter greater than 2 nm) are almost non-existent in the porous carbon materials. The specific surface area of ​​the material, fitted by the adsorption-desorption test curves, is 2219 m². 2 / g, the pore volume calculated at a single point is 1.14 cm³. 3 / g.

[0142] Figure 6 The pore size-cumulative pore volume curves of the porous carbon materials prepared in Examples 1-21 are shown. It can be seen that, corresponding to the nitrogen adsorption-desorption curves, the pore size distribution of the porous carbon materials is mainly concentrated in the micropore region, with the pore volume of pores smaller than 2 nm being 1.13 cm³. 3 / g, accounting for 99% of the total pore volume, with pores smaller than 1nm having a pore volume of 1.03 cm³. 3 / g, accounting for 90% of the total pore volume.

[0143] In the description of this application, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.

[0144] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A porous carbon material, characterized in that, It includes carbon nanotubes and carbon material particles, wherein the porous carbon material is in the form of particles, and the elastic modulus of the porous carbon material particles is Y1, wherein Y1 satisfies: 2.9 GPa≤Y1≤5.0 GPa, and the carbon nanotubes and the carbon material particles form an interpenetrating network structure; The total pore volume of the porous carbon material is P0 cm 3 / g, and the pore volume of pores with a pore diameter < 2 nm in the porous carbon material is P1 cm 3 / g. Among them, both P0 and P1 are pore volumes calculated at a single point, 0.53 ≤ P1 ≤ 1.3, 0.80 < P1 / P0 ≤ 0.

99. The powder conductivity of the porous carbon material under a pressure of 130 Mpa is ρ, and ρ satisfies: 3 S / cm ≤ ρ ≤ 30 S / cm.

2. The porous carbon material according to claim 1, characterized in that, The diameter of the carbon nanotube is L1, and L1 satisfies: 0.005μm≤L1≤0.05μm.

3. The porous carbon material according to claim 1, characterized in that, The carbon material particles satisfy at least one of the following conditions: (1) The sphericity of the carbon material particles is D, and D satisfies: 0.4≤D≤0.99; (2) The particle size Dv50 of the carbon material particles satisfies: 1μm≤Dv50≤20μm.

4. The porous carbon material according to claim 1, characterized in that, The specific surface area of ​​the porous carbon material is ε, and ε satisfies: 1300 m² 2 / g≤ε≤2800 m 2 / g.

5. The porous carbon material according to claim 1, characterized in that, The pore volume of the porous carbon material with a pore size <1 nm is P² cm⁻¹. 3 / g, where P2 is the pore volume calculated at a single point; the porous carbon material satisfies at least one of the following conditions: （1）0.71≤P0≤1.52； (2) 0.05≤P2 / P0≤0.

5.

6. The porous carbon material according to claim 5, characterized in that, 0.01≤P2≤0.6。 7. The porous carbon material according to claim 1, characterized in that, The number of pores in the cross-section of a single porous carbon material particle is m, where 0 < m ≤ 3; the diameter of the pores in the cross-section of a single porous carbon material particle is H, where H satisfies: 100 nm < H < 2000 nm.

8. The porous carbon material according to claim 1, characterized in that, The porous carbon material was observed by scanning electron microscopy. Within a 50 μm × 50 μm region, a single carbon nanotube passed through no more than four carbon material particles, and the number of carbon nanotubes present in a single carbon material particle was 1 to 10.

9. A silicon-carbon material comprising a silicon material and a porous carbon material as described in any one of claims 1 to 8.

10. An electrochemical device comprising a positive electrode, an electrolyte, a membrane, and a negative electrode, wherein the negative electrode comprises a negative electrode active material layer, the negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material comprises the silicon-carbon material as described in claim 9.

11. A method for preparing a porous carbon material as described in any one of claims 1 to 8, characterized in that, include, Carbon nanotubes, a carbon material precursor, and a curing agent are mixed uniformly according to a preset mass ratio, and then heated to a first reaction temperature T1 in a first protective atmosphere for programmed curing to obtain a mixed precursor. The preset mass ratio is: the mass percentage C of the carbon nanotubes in the mixed precursor is 1% ≤ C ≤ 6%. The programmed curing process includes a multi-step heating and curing process, comprising heating at 2~5℃ / min to 80℃, heating at 1~3℃ / min to 100℃, and holding at that temperature for a first holding time t. y 60 min≤t y ≤180 min, then increase the temperature at 1~3℃ / min to the first reaction temperature T1, 100℃≤T1≤200℃, hold for the first time t1, 8h≤t1≤12h; The mixed precursor is carbonized at a second reaction temperature T2 and in a second protective atmosphere to obtain a carbonized pretreated product; wherein, 900℃≤T2≤1300℃; the carbonization time is a second time t2, 1h≤t2≤4h; After the carbonized pretreated material is crushed and sieved, it is activated at a third reaction temperature T3 and in a third protective atmosphere to obtain the porous carbon material; wherein, 900℃≤T3≤1000℃; the activation time is the third time t3, 10h≤t3≤14h; The particle elastic modulus of the porous carbon material is Y1, which satisfies: 2.9 GPa≤Y1≤5.0 GPa.

12. The method for preparing porous carbon material according to claim 11, characterized in that, The carbon material precursor includes one or more of the following: epoxy resin, phenolic resin, melamine resin, polyaniline, polyacrylonitrile, polyvinylidene chloride, asphalt, coal tar, bisphenol A, and hexamethylenetetramine.

13. The method for preparing porous carbon material according to claim 11, characterized in that, The first protective atmosphere is an oxygen / nitrogen mixture, wherein the oxygen content is 10-20%; and / or, The second protective atmosphere is one of nitrogen and argon; and / or, The third protective atmosphere is one of carbon dioxide, carbon dioxide / nitrogen, and water vapor / carbon dioxide, wherein carbon dioxide gas accounts for 50% to 100%.

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