Soft-hard carbon composite material and preparation method and application thereof

Abstract

The application belongs to the technical field of battery negative electrode materials, and discloses a soft and hard carbon composite material, a preparation method and application thereof. A regulating agent composed of octadecyl trimethyl ammonium chloride and SM3BL is used to regulate pitch, and then the regulated pitch is mixed with phenolic resin, and sequentially subjected to solidification, carbonization and activation treatment to obtain the soft and hard carbon composite material. Transmission electron microscope characterization shows that the soft carbon phase in the soft and hard carbon composite material has graphite-like lattice stripes. The soft and hard carbon composite material provided by the application has stable structure and simple and controllable preparation method. In addition, the application provides a silicon-carbon material, a battery negative electrode and a battery.

Description

Technical Field

[0001] This invention belongs to the field of battery anode material technology, specifically relating to soft and hard carbon composite materials, their preparation methods, and applications. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density, long cycle life, and no memory effect, have become core energy storage devices in portable electronic devices, electric vehicles, and large-scale energy storage systems. With the continuous increase in the penetration rate of new energy vehicles and the constant iteration of consumer electronics products, the market is placing higher demands on the energy density, power density, and cycle stability of lithium-ion batteries. As a key component of lithium-ion batteries, the performance of the anode material directly affects the overall electrochemical performance of the battery; therefore, the development of novel high-performance anode materials has become a current research hotspot in the battery field.

[0003] Currently, graphite is the primary anode material for commercial lithium-ion batteries. Graphite anodes offer advantages such as good conductivity, structural stability, and low cost; however, their lithium storage mechanism, based on the LiC6 intercalation reaction, results in a theoretical specific capacity of only 372 mAh·g. -1 This makes it difficult to meet the development requirements of high-energy-density batteries. Furthermore, the small interlayer spacing of graphite (approximately 0.335 nm) results in a low diffusion rate of lithium ions between layers, severely limiting the rate performance of the battery. Under fast charging conditions, it can also easily induce lithium dendrite growth, posing safety hazards. Meanwhile, although high-capacity anodes represented by silicon-based materials have extremely high theoretical capacities, their massive volume expansion during charge and discharge (approximately 300%) leads to electrode structure pulverization and rapid capacity decay, and the problem of poor cycle stability has long remained unresolved.

[0004] Against this backdrop, hard carbon materials have attracted widespread attention due to their unique microstructure. Hard carbon consists of graphite-like microcrystalline regions and open pores, with an interlayer spacing larger than graphite (typically 0.37-0.42 nm), providing abundant transport channels and lithium storage sites for the rapid insertion and extraction of lithium ions, thus exhibiting a high theoretical specific capacity (typically reaching 400-600 mAh·g). -1 Hard carbon materials possess excellent rate performance. However, they face a series of key challenges in practical applications. First, the initial coulombic efficiency of hard carbon is generally low, primarily due to electrolyte decomposition caused by its high specific surface area, irreversible lithium capture induced by its open porous structure, and side reactions of oxygen-containing functional groups on its surface. Second, hard carbon contains numerous highly active edge sites (such as defects, open pores, and oxygen functional groups), which easily trigger parasitic reactions, leading to uncontrolled growth of the solid electrolyte interphase (SEI) film during the initial charge and discharge process, further exacerbating irreversible capacity loss. Furthermore, the low intrinsic conductivity of hard carbon limits its performance under high-rate charge and discharge conditions.

[0005] Currently, research on soft and hard carbon composite anode materials has made some progress. For example, some studies have used hard carbon to coat soft carbon in a composite porous carbon-based structure (see CN113889593A); other studies have used road petroleum asphalt as raw material to prepare hard and soft carbon composite materials through crosslinking treatment and activation of light and heavy components (see CN118851174A); still other studies have used anthracite as raw material to prepare soft and hard carbon composite anode materials by high-temperature pyrolysis carbonization followed by grinding and mixing with hard carbon materials (see CN119797329A).

[0006] However, the aforementioned existing technologies still have several problems that urgently need to be solved. For example, most composite methods rely on complex precursor modification and multi-step preparation processes, which are cumbersome and costly, making them unsuitable for large-scale production; the interfacial bonding between hard carbon and soft carbon is insufficient, and interfacial peeling and structural damage are prone to occur during long-term cycling, affecting the cycle life of the battery. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the first objective of this invention is to provide a soft and hard carbon composite material and a method for preparing the same; the second objective is to provide a silicon-carbon composite material and a method for preparing the same; and the third objective is to provide a battery negative electrode and a battery using the same negative electrode.

[0008] First, the present invention provides a soft-hard carbon composite material, wherein hard carbon forms a continuous matrix and soft carbon phase is distributed in the matrix; when observed with a transmission electron microscope at an accelerating voltage of 200 kV, the soft carbon phase has graphite-like lattice stripes; the length of the graphite-like lattice stripes is 1-5 nm, the interlayer spacing is 0.35-0.42 nm, and the number of stacked layers is 2-10.

[0009] In this field, when observed using a transmission electron microscope (TEM) at an accelerating voltage of 200 kV, graphite stripes have the following characteristics: straight, continuous, long-range, typically with a stripe length greater than 20 nm, and usually stacked in 10 to hundreds of layers; amorphous carbon, on the other hand, shows almost no stripes.

[0010] The “graphite-like lattice stripes” described in this application refer to the microstructure of carbon materials that have layered stripe characteristics similar to graphite, but whose degree of order, continuity and orientation are between those of graphite and completely disordered carbon, as observed by transmission electron microscopy (TEM) at an accelerating voltage of 200 kV.

[0011] The "graphite-like lattice fringes" described in this application have the following main characteristics: 1. Shape: short-range straight or slightly curved, in the form of segments, arcs or wavy lines; 2. Continuity: discontinuous, with interruptions, dislocations or branches; 3. Fringe length: relatively short, 1-5 nm (graphite is tens to hundreds of nanometers); 4. Interlayer spacing: between 0.35-0.42 nm (greater than graphite's 0.335 nm); 5. Short-range stacking of 2-10 layers.

[0012] Furthermore, the soft and hard carbon composite material has a porous structure, wherein, based on the pore volume ratio, the proportion of pores with a diameter less than 0.7 nm is less than 30%, the proportion of pores with a diameter greater than 5 nm is less than 30%, and the proportion of pores with a diameter greater than 10 nm is <10%.

[0013] Furthermore, the pore volume of the soft and hard carbon composite material is 0.1~2 cm³. 3 / g.

[0014] Secondly, the present invention provides a method for preparing a soft and hard carbon composite material, comprising the following steps: 10-60 parts by weight of asphalt, 38-90 parts by weight of water, and 0.06-0.15 parts by weight of regulator are mixed at high speed to obtain an asphalt mixture solution; the regulator is composed of octadecyltrimethylammonium chloride and SM3BL (produced by Jiangxi Simo Biochemical), wherein the mass ratio of octadecyltrimethylammonium chloride to SM3BL is 2:1-4:1; The asphalt mixture is mixed evenly with phenolic resin and then cured. The solidified material is crushed and then subjected to carbonization and activation treatments in sequence to obtain a soft and hard carbon composite material.

[0015] Furthermore, the mass ratio of asphalt to phenolic resin in the asphalt mixture is N, where 0 < N ≤ 0.5.

[0016] Furthermore, the carbonization treatment is carried out at a temperature of 600-900℃, in a nitrogen atmosphere, for a time of 2-5 hours.

[0017] Furthermore, the activation treatment is performed at a temperature of 800-850°C, in a nitrogen atmosphere, for a time of 2-10 hours.

[0018] Based on a second aspect of the present invention, the present invention provides a silicon-carbon material obtained by depositing silicon on the aforementioned soft and hard carbon composite material by chemical vapor deposition.

[0019] Furthermore, the present invention provides a battery negative electrode using the aforementioned silicon-carbon material as the active material.

[0020] The present invention provides a battery comprising the above-described negative electrode.

[0021] Compared with the prior art, the above-described one or more technical solutions of the present invention can achieve at least one of the following beneficial effects: The soft and hard carbon composite materials prepared by this invention have stable structures and the preparation method is simple and controllable, which is conducive to large-scale production.

[0022] The soft and hard carbon composite material prepared by this invention is subjected to silicon deposition via chemical vapor deposition to obtain silicon-carbon material. When applied to lithium-ion batteries, silicon-carbon material can improve the battery's delithiation capacity, initial efficiency, and 1C rate capability. Attached Figure Description

[0023] Figure 1 This is a TEM image of the soft and hard carbon composite material obtained in Example 1.

[0024] Figure 2 The image shows a TEM image of the soft and hard carbon composite material obtained in Comparative Example 1.

[0025] Figure 3 The image shows a TEM image of the soft and hard carbon composite material obtained in Comparative Example 2.

[0026] Figure 4 The image shows a TEM image of the soft and hard carbon composite material obtained in Comparative Example 3.

[0027] Figure 5 The image shows a TEM image of the soft and hard carbon composite material obtained in Comparative Example 4.

[0028] Figure 6 The image shows a TEM image of the soft and hard carbon composite material obtained in Comparative Example 5.

[0029] Figure 7 This is a TEM image of the soft and hard carbon composite material obtained in Example 2.

[0030] Figure 8 This is a TEM image of the soft and hard carbon composite material obtained in Example 3.

[0031] Figure 9 This is a TEM image of the soft and hard carbon composite material obtained in Example 4.

[0032] Figure 10 This is a TEM image of the soft and hard carbon composite material obtained in Example 5.

[0033] In the figure, the area marked by the box represents the soft carbon phase. Detailed Implementation

[0034] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0035] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0037] Example 1 10 parts by weight of asphalt, 38 parts by weight of water, and 0.08 parts by weight of regulator (octadecyltrimethylammonium chloride and SM3BL in a mass ratio of 3:1) were mixed at high speed to obtain an asphalt mixture solution. The asphalt mixture was mixed evenly with 33.33 parts by weight of phenolic resin and then cured. The solidified material was crushed and carbonized at 800°C in an inert gas atmosphere for 3 hours, and then activated at 820°C in a nitrogen atmosphere for 6 hours to obtain a soft and hard carbon composite material.

[0038] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that no regulator was added to the asphalt mixture.

[0039] 10 parts by weight of asphalt and 38 parts by weight of water are mixed at high speed to obtain an asphalt mixture solution; The asphalt mixture was mixed evenly with 33.33 parts by weight of phenolic resin and then cured. The solidified material was crushed and carbonized at 800°C in an inert gas atmosphere for 3 hours, and then activated at 820°C in a nitrogen atmosphere for 6 hours to obtain a soft and hard carbon composite material.

[0040] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the timing of the addition of the regulator is different.

[0041] 10 parts by weight of asphalt and 38 parts by weight of water are mixed at high speed to obtain an asphalt mixture solution; After mixing the asphalt mixture with 33.33 parts by weight of phenolic resin until homogeneous, add 0.08 parts by weight of regulator and continue mixing until homogeneous, then cure. The solidified material was crushed and carbonized at 800°C in an inert gas atmosphere for 3 hours, and then activated at 820°C in a nitrogen atmosphere for 6 hours to obtain a soft and hard carbon composite material.

[0042] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the timing of the addition of the regulator is different.

[0043] 10 parts by weight of asphalt and 38 parts by weight of water are mixed at high speed to obtain an asphalt mixture solution; After thoroughly mixing the asphalt mixture, 33.33 parts by weight of phenolic resin, and 0.08 parts by weight of regulator, the mixture is cured. The solidified material was crushed and carbonized at 800°C in an inert gas atmosphere for 3 hours, and then activated at 820°C in a nitrogen atmosphere for 6 hours to obtain a soft and hard carbon composite material.

[0044] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the amount of regulator added is different.

[0045] 10 parts by weight of asphalt, 38 parts by weight of water, and 0.05 parts by weight of regulator are mixed at high speed to obtain an asphalt mixture solution; The asphalt mixture was mixed evenly with 33.33 parts by weight of phenolic resin and then cured. The solidified material was crushed and carbonized at 800°C in an inert gas atmosphere for 3 hours, and then activated at 820°C in a nitrogen atmosphere for 6 hours to obtain a soft and hard carbon composite material.

[0046] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the amount of regulator added is different.

[0047] 10 parts by weight of asphalt, 38 parts by weight of water, and 0.16 parts by weight of regulator were mixed at high speed to obtain an asphalt mixture solution; The asphalt mixture was mixed evenly with 33.33 parts by weight of phenolic resin and then cured. The solidified material was crushed and carbonized at 800°C in an inert gas atmosphere for 3 hours, and then activated at 820°C in a nitrogen atmosphere for 6 hours to obtain a soft and hard carbon composite material.

[0048] Comparative Example 6 The only difference between Comparative Example 6 and Example 1 is that the mass ratio of octadecyltrimethylammonium chloride and SM3BL in the regulator is 1:1.

[0049] Comparative Example 7 The only difference between Comparative Example 7 and Example 1 is that the mass ratio of octadecyltrimethylammonium chloride and SM3BL in the regulator is 5:1.

[0050] Comparative Example 8 The only difference between Comparative Example 8 and Example 1 is that the phenolic resin is replaced with furfural resin.

[0051] Comparative Example 9 The only difference between Comparative Example 9 and Example 1 is that the phenolic resin is replaced with urea-formaldehyde resin.

[0052] The microstructure of the materials obtained in Example 1 and the comparative example was characterized by transmission electron microscopy (TEM). The instrument used was a Talos F200S field emission transmission electron microscope with an accelerating voltage of 200 kV and a magnification of 1.05 M times (i.e., 1,050,000 times).

[0053] Figure 1 The image shows a TEM image of the soft and hard carbon composite material obtained in Example 1. As can be seen from the image, the soft carbon exhibits graphite-like stripes after carbonization, with short-range order and long-range disorder, distributed in the hard carbon.

[0054] Figure 2 The TEM image of the soft and hard carbon composite material obtained in Comparative Example 1 shows that no graphite-like streaks were observed.

[0055] Figure 3 The TEM image of the soft and hard carbon composite material obtained in Comparative Example 2 shows that no graphite-like streaks were observed.

[0056] Figure 4 The TEM image of the soft and hard carbon composite material obtained in Comparative Example 3 shows that no graphite-like streaks were observed.

[0057] Figure 5 The TEM image of the soft and hard carbon composite material obtained in Comparative Example 4 shows that no graphite-like streaks were observed.

[0058] Figure 6 The TEM image of the soft and hard carbon composite material obtained in Comparative Example 5 shows that no graphite-like streaks were observed.

[0059] Example 2 30 parts by weight of asphalt, 60 parts by weight of water, and 0.10 parts by weight of regulator (octadecyltrimethylammonium chloride and SM3BL in a mass ratio of 2:1) were mixed at high speed to obtain an asphalt mixture solution. The asphalt mixture is mixed evenly with 150 parts by weight of phenolic resin and then cured. The solidified material was crushed and carbonized at 700°C in an inert gas atmosphere for 4 hours, and then activated at 800°C in a nitrogen atmosphere for 6 hours to obtain a soft and hard carbon composite material.

[0060] Example 3 45 parts by weight of asphalt, 80 parts by weight of water, and 0.06 parts by weight of regulator (octadecyltrimethylammonium chloride and SM3BL in a mass ratio of 4:1) were mixed at high speed to obtain an asphalt mixture solution. The asphalt mixture was mixed evenly with 112 parts by weight of phenolic resin and then cured. The solidified material was crushed and carbonized at 900℃ in an inert gas atmosphere for 2 hours, and then activated at 850℃ in a nitrogen atmosphere for 5 hours to obtain a soft and hard carbon composite material.

[0061] Example 4 60 parts by weight of asphalt, 90 parts by weight of water, and 0.15 parts by weight of regulator (octadecyltrimethylammonium chloride and SM3BL in a mass ratio of 2:1) were mixed at high speed to obtain an asphalt mixture solution. The asphalt mixture is mixed evenly with 600 parts by weight of phenolic resin and then cured. The solidified material was crushed and carbonized at 600°C in an inert gas atmosphere for 5 hours, and then activated at 850°C in a nitrogen atmosphere for 6 hours to obtain a soft and hard carbon composite material.

[0062] Example 5 60 parts by weight of asphalt, 80 parts by weight of water, and 0.1 parts by weight of regulator (octadecyltrimethylammonium chloride and SM3BL in a mass ratio of 3:1) were mixed at high speed to obtain an asphalt mixture solution; The asphalt mixture is mixed evenly with 120 parts by weight of phenolic resin and then cured. The solidified material was crushed and carbonized at 800°C in an inert gas atmosphere for 5 hours, and then activated at 850°C in a nitrogen atmosphere for 5 hours to obtain a soft and hard carbon composite material.

[0063] Similarly, the materials obtained in Examples 2-5 were characterized by microstructure using transmission electron microscopy (TEM). The instrument used was a Talos F200S field emission transmission electron microscope with an accelerating voltage of 200 kV and a magnification of 1.05 M times (i.e., 1,050,000 times).

[0064] Figures 7-10 The images show TEM images of the soft and hard carbon composite materials obtained in Examples 2-5. As can be seen from the images, the soft carbon exhibits graphite-like stripes after carbonization, with short-range order and long-range disorder, distributed in the hard carbon.

[0065] The pore volumes of the soft and hard carbon composite materials obtained in Examples 1-5 and Comparative Examples 1-9 were tested in the following manner: Reference standard: GB / T 19587-2017 Determination of specific surface area of ​​solid substances by gas adsorption BET method.

[0066] Testing instrument: BSD-PS type BSD specific surface area tester.

[0067] Specific steps: Sample pretreatment: Pass the porous carbon powder through a 200-mesh sieve, weigh about 100-200 mg of sample and place it in a sample tube, and degas it under vacuum at 300℃ for 6-12 h to remove moisture and impurity gases adsorbed on the sample surface.

[0068] Test Procedure: The treated sample tubes were installed in the analysis station, and the nitrogen adsorption-desorption isotherm was measured at liquid nitrogen temperature (77K). The relative pressure (P / P0) was measured in the range of 0.005 to 0.995. The pore size distribution and pore volume were analyzed using a DFT model; the total pore volume was calculated from the adsorption amount at a relative pressure P / P0≈0.99. The test results are shown in Table 1.

[0069] Table 1 As shown in Table 1, when asphalt is treated with a regulator and then cured, carbonized, and activated together with phenolic resin, the resulting soft and hard carbon composite material has a small proportion of both micropores and larger pores, and graphite-like streaks can be observed in the TEM image. However, when no regulator is added during the preparation process, the timing of the regulator addition varies, the mass ratio of octadecyltrimethylammonium chloride and SM3BL in the regulator is too high or too low, or other resins are used instead of phenolic resin, the proportion of micropores with a pore size <0.7 nm is very large, and the proportion of pores with a pore size >10 nm is relatively high. In these cases, graphite-like streaks cannot be observed in the TEM image of the soft and hard carbon composite material.

[0070] The soft and hard carbon composite materials obtained in Examples 1-5 and Comparative Examples 1-9 were deposited with silicon to obtain silicon-carbon materials as follows: The soft and hard carbon composite materials were placed in a tube furnace and heated from room temperature to 450°C at a rate of 5°C / min under a N2 atmosphere; then a 25% SiH4-N2 mixed gas was introduced, and the temperature was held at 500°C for 18 h. Afterwards, the temperature was switched to a 25% SiH4-N2 mixed gas, while simultaneously introducing 25% C2H4-N2 gas through another channel, and co-deposited at 500°C for 15 h in the mixed atmosphere. Next, only a 25% C2H4-N2 mixed gas was introduced, and the temperature was held at 550°C for 8 h. Finally, the temperature was switched to an N2 atmosphere and allowed to cool naturally.

[0071] The silicon-carbon materials obtained above were used to assemble batteries and their electrochemical performance was tested. Half-cell assembly: The obtained silicon-carbon material was used to prepare the negative electrode sheet: N-methylpyrrolidone (NMP) was added according to the mass ratio of silicon-carbon material: conductive agent SP: binder PVDF = 92:3:5, and the mixture was stirred at high speed to form a slurry. The slurry was coated onto copper foil, vacuum dried at 80℃ for 4 hours, and then rolled (compacted density 1.5 g / cm³) and cut into sheets (diameter 12 mm) to obtain the negative electrode sheet. A CR2032 coin cell was assembled in a glove box, using a lithium metal sheet as the counter electrode, a polypropylene microporous membrane as the separator, and LiPF6 dissolved in a mixture of ethyl carbonate (EC) and diethyl carbonate (DEC) (volume ratio EC:DEC = 1:1), with a LiPF6 concentration of 1 mol / L.

[0072] The battery was tested for charge and discharge using the LAND battery testing system.

[0073] Cyclic specific capacity and initial efficiency tests: After the CR2032 coin cell was left to stand for 6 hours, it was discharged at 0.1C to 0.005V, and the specific capacity was recorded as Q1; then it was discharged at a constant voltage of 0.005V until the current cutoff was 0.01C, and the specific capacity was recorded as Q2; after standing for 5 minutes, it was charged at a constant current of 0.1C to 0.8V, and the specific capacity was recorded as Q3; after standing for 5 minutes, it was charged at a constant current of 0.1C to 1.5V, and the specific capacity was recorded as Q4; after standing for 5 minutes, it was discharged at a constant current of 1.0C to 0.005V, and the specific capacity was recorded as Q5. The initial lithium delithiation specific capacity is the specific capacity (or mass specific capacity) of the electrode material, and the ratio of the initial lithium delithiation capacity to the initial lithium insertion capacity is the initial coulombic efficiency of the battery.

[0074] 0.8V first efficiency = Q3 / (Q1+Q2)×100%; 1.5V initial efficiency = (Q3+Q4) / (Q1+Q2)×100%; 1C rate discharge retention rate = Q5 / (Q3+Q4)×100%.

[0075] Expansion ratio test: After testing the cycle capacity and initial efficiency, the battery was left to stand for 2 hours. Then, the negative electrode thickness was measured sequentially, and the average value was recorded as h1. Another coated and dried electrode was taken, and the negative electrode thickness at 5 points was measured, and the average value was recorded as h2.

[0076] Lithium intercalation expansion ratio = (h1-h2) / h2 × 100%. Capacity retention test: After the cell is left to rest for 5 minutes, it is discharged at 0.1C constant current and constant voltage to 0.005V, left to rest for 5 minutes, discharged at 0.02C to 0.005V, and charged at 0.1C constant current and constant voltage to 1.5V; after leaving to rest for 5 minutes, it is discharged at 0.25C to 0.005V; after leaving to rest for 5 minutes, it is charged at 0.25C constant current to 1.5V, and cycled 50 times at a rate of 0.25C. The specific capacity of the charge on the 50th cycle / the charge capacity on the 1st cycle × 100% is used to calculate the specific capacity retention rate.

[0077] The test results are shown in Table 2.

[0078] Table 2 The data in Table 2 show that the soft and hard carbon composite material provided by the present invention or the soft and hard carbon composite material provided by the preparation method of the present invention, after being treated with vapor phase silicon deposition, is used as the negative electrode of lithium-ion battery, and the overall electrical performance of lithium-ion battery is significantly improved, and the lithium intercalation expansion ratio of the electrode sheet decreases.

[0079] 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 soft and hard carbon composite material, characterized in that, In the aforementioned soft and hard carbon composite material, hard carbon forms a continuous matrix, and the soft carbon phase is distributed within the matrix. When observed using a transmission electron microscope at an accelerating voltage of 200 kV, the soft carbon phase exhibits graphite-like lattice fringes. The length of the graphite-like lattice fringes is 1-5 nm, the interlayer spacing is 0.35-0.42 nm, and the number of stacked layers is 2-10.

2. The soft and hard carbon composite material according to claim 1, characterized in that, Based on pore volume ratio, the proportion of pores with a diameter less than 0.7 nm is less than 30%, the proportion of pores with a diameter greater than 5 nm is less than 30%, and the proportion of pores with a diameter greater than 10 nm is less than 10%.

3. The soft and hard carbon composite material according to claim 1 or 2, characterized in that, The pore volume is 0.1~2cm. 3 / g.

4. A method for preparing a soft and hard carbon composite material as described in any one of claims 1-3, characterized in that, Includes the following steps: 10-60 parts by weight of asphalt, 38-90 parts by weight of water, and 0.06-0.15 parts by weight of regulator are mixed at high speed to obtain an asphalt mixture solution; the regulator is composed of octadecyltrimethylammonium chloride and SM3BL, wherein the mass ratio of octadecyltrimethylammonium chloride to SM3BL is 2:1-4:1; The asphalt mixture is mixed evenly with phenolic resin and then cured. The solidified material is crushed and then subjected to carbonization and activation treatments in sequence to obtain a soft and hard carbon composite material.

5. The preparation method according to claim 4, characterized in that, The mass ratio of asphalt to phenolic resin in the asphalt mixture is N, where 0 < N ≤ 0.

5.

6. The preparation method according to claim 4, characterized in that, The carbonization process is carried out at a temperature of 600-900℃, in an inert gas atmosphere, for a time of 2-5 hours.

7. The preparation method according to claim 4, characterized in that, The activation treatment is performed at a temperature of 800-850℃, in a nitrogen atmosphere, for 2-10 hours.

8. A silicon-carbon material, characterized in that, Silicon is obtained by depositing silicon in the pores of the soft and hard carbon composite material according to any one of claims 1-3 by chemical vapor deposition.

9. A battery negative electrode, characterized in that, Including the silicon-carbon material as described in claim 8.

10. A battery, characterized in that, Includes the battery negative electrode as described in claim 9.

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