Porous carbon material, preparation method thereof, silicon-carbon composite negative electrode material and application thereof

Abstract

The present disclosure relates to a kind of porous carbon material and its preparation method, silicon-carbon composite negative material and application.The preparation method includes the following steps: (1) organic matter precursor is dispersed in solvent, then mixed with alkali source and crosslinking agent, drying, obtain pre-treatment product;(2) pre-treatment product is activated and carbonized, to obtain the porous carbon material.In the preparation method provided in the present disclosure, by pre-treatment and subsequent activation and carbonization, on the one hand, the content of oxygen in the product can be controlled, on the other hand, the state of oxygen in the surface functional groups of the product can also be adjusted, so that a large number of uniform deposition layers can be formed during the deposition of elemental silicon on the surface of the porous carbon material;And the production of silicon oxide and silicon carbide can be effectively controlled, so as to improve the silicon-carbon composite negative material formed has initial coulomb efficiency, capacity, cycle performance stability.

Description

Technical Field

[0001] This disclosure relates to the field of lithium-ion battery technology, and in particular to a porous carbon material and its preparation method, a silicon-carbon composite anode material and its application. Background Technology

[0002] Currently, carbon-based materials that can be used for elemental silicon deposition in lithium battery anodes mainly include carbon black, graphite, and resin pyrolysis carbon.

[0003] For elemental silicon-deposited carbon black materials, the elemental silicon deposited on the surface is mostly attached to the carbon-based surface in the form of nanoparticles. During cycling, the elemental silicon is prone to detach from the carbon-based surface due to expansion and pulverization, resulting in poor cycle performance of lithium-ion batteries and low initial coulombic efficiency. The method of preparing lithium-ion battery anodes by depositing elemental silicon on graphite substrate has been under development for over twenty years (Journal of Applied Physics 77, 2363 (1995)). Early methods mainly formed discretely distributed elemental silicon particles on the surface of graphite particles. In recent years, by incorporating a certain amount of molecules such as ethylene into the silicon source gas (Nature Energy 6, 1164 (2021)), the deposition process has been controlled, achieving the formation of a continuous deposition layer of elemental silicon on the surface of graphite particles, effectively improving the problems of low initial coulombic efficiency and poor cycle performance. However, due to the configuration of graphite materials, it is difficult to deposit large amounts of silicon, thus the problem of low reversible capacity still exists. Porous carbon materials have high capacity and specific surface area, and are therefore currently used as a matrix material for silicon deposition (202111277420.0, 202111277556.1). The deposition of elemental silicon on them is mainly dispersed nucleation, with a high degree of dispersion. Therefore, although high capacity and first efficiency can be achieved, the capacity decays severely in the first twenty cycles, with only 42%-53% of the first reversible capacity.

[0004] Therefore, it is necessary to develop suitable carbon-based materials that allow elemental silicon to be uniformly and massively deposited on them in order to synthesize silicon-carbon materials with high initial coulombic efficiency, high capacity, and good cycle stability. Summary of the Invention

[0005] To address the aforementioned technical problems, this disclosure provides a porous carbon material and its preparation method, a silicon-carbon composite anode material, and its applications.

[0006] In a first aspect, this disclosure provides a method for preparing a porous carbon material, the method comprising the following steps:

[0007] (1) Disperse the organic precursor in a solvent, then mix it with an alkali source and a crosslinking agent, and dry it to obtain a pretreated product;

[0008] (2) The pretreated product is activated and carbonized to obtain the porous carbon material.

[0009] The preparation method provided in this disclosure can control the specific surface area and pore size distribution of porous carbon materials, and can also control the oxygen content and oxygen state on their surface. This allows the final porous carbon material to uniformly deposit elemental silicon, forming a large number of uniform deposition layers. Specifically:

[0010] In step (1) provided in this disclosure, the (soluble) polymer dispersed in a solvent (preferably water) is more likely to come into uniform and sufficient contact with the alkali, additives and crosslinking agent, thereby ensuring that after mixing and drying, a carbonized precursor with a certain molecular structure and composition can be obtained. In this precursor, the alkali source and crosslinking agent are uniformly distributed, and after carbonization, it is easy to have more porous structures (including open pores and closed pores).

[0011] The purpose of step (2) provided in this disclosure is to perform additional pore formation, pore enlargement and pore opening, so that the carbon material obtained in the end can have a large specific surface area.

[0012] As a preferred technical solution of this disclosure, step (1) further includes: after dispersing the organic precursor in a solvent, adding an additive, preferably the mass of the additive is 1%-10% of the mass of the organic precursor, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, etc., and preferably the solvent is water.

[0013] The additives provided in this disclosure can change the compositional characteristics of the inner and outer surfaces of the product carbon pores, and can make the final porous carbon material have better affinity with elemental silicon, thereby ensuring that elemental silicon can be uniformly deposited on the surface of the porous carbon material in the subsequent process.

[0014] As a preferred embodiment of this disclosure, the additive is selected from silicate compounds.

[0015] As a preferred embodiment of this disclosure, the organic precursor is selected from soluble phenolic polymers.

[0016] As a preferred technical solution of this disclosure, the alkali source is selected from any one or a combination of at least two of ammonia, urea or sodium carbonate.

[0017] As a preferred embodiment of this disclosure, the crosslinking agent is selected from hexamethylenetetramine and / or bisphenol crosslinking agents.

[0018] As a preferred technical solution of this disclosure, in step (1), the amount of alkali source added is such that the pH value of the mixed solution is 7.5-9, for example 7.6, 7.7, 7.8, 7.9, 8, 8.2, 8.5, 8.8, etc.

[0019] As a preferred embodiment of this disclosure, the mass ratio of the organic precursor to the crosslinking agent is 1:0.1-1, such as 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, etc.

[0020] As a preferred technical solution of this disclosure, step (2) includes:

[0021] The pretreated product is mixed with zinc chloride and activated at 300-450℃ (e.g., 320℃, 350℃, 380℃, 400℃, 420℃, etc.) for 1-1.5h (e.g., 1.1h, 1.2h, 1.3h, 1.4h, etc.). The temperature is then programmed to rise to 1200-1400℃ (e.g., 1250℃, 1300℃, 1350℃, etc.) for carbonization for 0.5-2h (e.g., 0.8h, 1h, 1.2h, 1.5h, 1.8h, etc.) to obtain the porous carbon material.

[0022] or:

[0023] The pretreated product is mixed with zinc chloride and carbonized at 1200-1400℃ (e.g., 1250℃, 1300℃, 1350℃, etc.) for 0.5-2h (e.g., 0.8h, 1h, 1.2h, 1.5h, 1.8h, etc.). Then it is mixed with hydroxide and activated at 700-900℃ (e.g., 750℃, 800℃, 850℃, etc.) for 0.5-2h (e.g., 0.8h, 1h, 1.2h, 1.5h, 1.8h, etc.) to obtain the porous carbon material.

[0024] or:

[0025] The pretreated product is mixed with zinc chloride and activated for the first time at 300-450℃ (e.g., 320℃, 350℃, 380℃, 400℃, 420℃, etc.) for 1-1.5h (e.g., 1.1h, 1.2h, 1.3h, 1.4h, etc.). The temperature is then increased to 1200-1400℃ (e.g., 1250℃, 1300℃, 1350℃, etc.) for carbonization for 0.5-2h (e.g., 0.8h, 1h, 1.2h, 1.5h, 1.8h, etc.). The product is then mixed with hydroxide and activated for the second time at 700-900℃ (e.g., 750℃, 800℃, 850℃, etc.) for 0.5-2h (e.g., 0.8h, 1h, 1.2h, 1.5h, 1.8h, etc.) to obtain the porous carbon material.

[0026] As a preferred technical solution of this disclosure, in step (2), both activation and carbonization are carried out under an inert atmosphere, preferably nitrogen or argon.

[0027] In this disclosure, activation can create pores in carbon materials, while carbonization can increase the carbon content of carbon materials. The two steps are combined, and zinc chloride, which can play a role in dehydration, cross-linking and regulating micropore distribution, and hydroxide, which can expand and create pores through etching, are also used, so that the final porous carbon material can well meet the application requirements.

[0028] As a preferred technical solution of this disclosure, the mass ratio of the pretreated product to zinc chloride is 1:2-6, for example 1:3, 1:4, 1:5, etc.

[0029] As a preferred embodiment of this disclosure, the mass ratio of the pretreated product to the hydroxide is 1:1-6, for example, 1:2, 1:3, 1:4, 1:5, etc.

[0030] As a preferred embodiment of this disclosure, the hydroxide is selected from any one or a combination of at least two of potassium hydroxide, sodium hydroxide, or lithium hydroxide.

[0031] In this disclosure, step (1) can be route p1 or route p2:

[0032] Route p1: Disperse the organic precursor in water, then add the additive and mix for 1-6 hours. Then add the alkali source and cross-linking agent and mix thoroughly for 1-12 hours. Wash and dry for later use.

[0033] Route p2: Disperse the organic precursor in water, then add an alkali source and a cross-linking agent and mix thoroughly for 1-12 hours. Wash and dry for later use.

[0034] In step (1), it should be noted that, regardless of route p1 or route p2, the pH value of the mixed system needs to be maintained between 7.5 and 9 after all materials are mixed.

[0035] In this disclosure, step (2) can be route c1, route c2, or route c3:

[0036] Route c1: The pretreated product is mixed with zinc chloride at a mass ratio of 1:2-6, heated to 300-450℃ and held for 1-1.5h for activation, and then the temperature is programmed to rise to 1200-1400℃ and held for 0.5-2h.

[0037] Route c2: The pretreated product is heated to 1200-1400℃ and held for 0.5-2h, then mixed with potassium hydroxide at a mass ratio of 1:1-6, heated to 700-900℃ and held for 0.5-2h to activate it, thus obtaining the porous carbon material.

[0038] Route c3: The pretreated product is mixed with zinc chloride at a mass ratio of 1:2-6, heated to 300-450℃ and held for 1-1.5h for activation, then the temperature is increased to 1200-1400℃ and held for 0.5-2h, and then mixed with potassium hydroxide at a mass ratio of 1:1-6, heated to 700-900℃ and held for 0.5-2h for activation, to obtain the porous carbon material.

[0039] In steps (1) and (2), routes p1 and p2 can be used in any combination with routes c1, c2 and c3 to obtain the porous carbon material described in this disclosure.

[0040] Secondly, this disclosure provides porous carbon materials prepared by the preparation method described in the first aspect.

[0041] As a preferred embodiment of this disclosure, the porous carbon material has a specific surface area of ​​50-2500 m². 2 / g, the pore size of the surface is 0.7-100nm, the total oxygen content of the surface is ≤15wt%, such as 8%, 10%, 12%, 14%, etc., and the double bond oxygen content does not exceed 60% of the total oxygen content, such as 58%, 55%, 50%, 45%, 40%, 35%, 30%, etc.

[0042] The specific surface area mentioned in this disclosure refers to the distribution of specific surface area, and the pore size refers to the pore size distribution.

[0043] In the preparation method provided in this disclosure, through pretreatment and subsequent activation and carbonization, the oxygen content in the product can be controlled, and the oxygen state in the surface functional groups of the product can be adjusted. This enables the formation of a large number of uniform deposition layers of elemental silicon on the surface of porous carbon materials. Furthermore, it effectively controls the generation of silicon oxide and silicon carbide, thereby improving the initial coulombic efficiency, capacity, and cycle performance stability of the formed silicon-carbon composite anode material.

[0044] Thirdly, this disclosure provides a silicon-carbon composite anode material, the composition of which includes the porous carbon material described in the second aspect and elemental silicon deposited on the surface of the porous carbon material.

[0045] Fourthly, this disclosure provides a negative electrode sheet, characterized in that it comprises the porous carbon material described in the second aspect or the silicon-carbon composite negative electrode material described in the third aspect.

[0046] Fifthly, this disclosure provides an electrochemical device, characterized in that it comprises the porous carbon material described in the second aspect, the silicon-carbon composite negative electrode material described in the third aspect, or the negative electrode sheet described in the fourth aspect.

[0047] In a sixth aspect, this disclosure provides a vehicle characterized by comprising the negative electrode sheet described in the fourth aspect or the electrochemical device described in the fifth aspect.

[0048] The technical solution provided in this disclosure has the following advantages compared with the prior art:

[0049] (1) The preparation method provided in this disclosure is simple and easy to implement. Furthermore, the method provided in this disclosure can control the pore size distribution of porous carbon materials, and can also control the oxygen content and oxygen state in porous carbon materials, so that the final porous carbon materials have better application effects.

[0050] (2) The porous carbon material provided in this disclosure enables the formation of a large number of uniform deposition layers when elemental silicon is deposited on its surface. At the same time, the porous carbon material provided in this disclosure can effectively control the generation of silicon oxide and silicon oxide, thereby making the final silicon-carbon composite anode material have excellent first coulombic efficiency and capacity, and high cycle stability. Detailed Implementation

[0051] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0052] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0053] Preparation Example 1

[0054] This preparation example provides a porous carbon material and its preparation method.

[0055] (1) 20g of water-soluble phenolic resin and 18g of hexamethylenetetramine were dispersed in 5g of ammonia water. Deionized water was continuously added and stirred thoroughly to dissolve the resin. The final homogeneous system was then pH=8.0. 0.5g of tetraethyl orthosilicate was added and stirred for 2h. After separating the precipitate, it was aged at 110℃ for 12h to obtain the precursor.

[0056] (2) The precursor and zinc chloride were uniformly mixed at a mass ratio of 1:2, and then heated to 350℃ and held for 2 hours under Ar atmosphere, followed by heating to 1400℃ and holding for 2 hours to obtain product 1. Product 1 was mixed with KOH at a mass ratio of 1:4, and heated to 850℃ and held for 1 hour under Ar atmosphere. After removing the alkali from the activated product by washing with water, the final product, porous carbon material, was obtained.

[0057] Preparation Example 2

[0058] This preparation example provides a porous carbon material and its preparation method.

[0059] (1) 20g of water-soluble phenolic resin and 18g of bisphenol-A were dispersed in a urea aqueous solution. Deionized water was continuously added and stirred thoroughly to dissolve the resin. The final homogeneous system was then pH=7.5. 0.5g of trimethylsiloxysilicate was added and stirred for 2h. After separating the precipitate, it was aged at 145℃ for 12h to obtain the precursor.

[0060] (2) After uniformly mixing the precursor and zinc chloride at a mass ratio of 1:2, the temperature was raised to 350℃ and held for 2 hours under Ar atmosphere, and then raised to 1400℃ and held for 2 hours to obtain the final product, porous carbon material.

[0061] Preparation Example 3

[0062] This preparation example provides a porous carbon material and its preparation method.

[0063] (1) 20g of water-soluble phenolic resin and 12g of hexamethylenetetramine were dispersed in a urea aqueous solution. Deionized water was continuously added and stirred thoroughly to dissolve the resin. The final homogeneous system was then pH=8.0. 0.5g of tetraethyl orthosilicate was added and stirred for 2 hours. The precipitate was separated and then aged at 110℃ for 12 hours to obtain the precursor.

[0064] (2) The precursor and zinc chloride were uniformly mixed at a mass ratio of 1:2, and then heated to 350℃ and held for 2 hours under an Ar atmosphere. The temperature was then increased to 1400℃ and held for 2 hours to obtain product 2. Product 2 was mixed with KOH at a mass ratio of 1:2, and heated to 850℃ and held for 1 hour under an Ar atmosphere. After removing the alkali from the activated product, the final product, porous carbon material, was obtained.

[0065] Preparation Example 4

[0066] This preparation example provides a porous carbon material and its preparation method.

[0067] (1) 20g of water-soluble melamine resin, 18g of hexamethylenetetramine, 5g of ammonia water, and 10g of deionized water were added to form a homogeneous system with pH=8.8. The mixture was thoroughly ground and impregnated, and then aged at 110℃ for 12h to obtain the precursor.

[0068] (2) The precursor and zinc chloride were uniformly mixed at a mass ratio of 1:2, and then heated to 350℃ and held for 2 hours under Ar atmosphere, followed by heating to 1400℃ and holding for 2 hours to obtain product 1. Product 1 was mixed with KOH at a mass ratio of 1:4, and heated to 850℃ and held for 1 hour under Ar atmosphere. After removing the alkali from the activated product, the final product, porous carbon material, was obtained.

[0069] Preparation Example 5

[0070] This preparation example provides a porous carbon material and its preparation method.

[0071] (1) 20g of water-soluble phenolic resin and 15g of bisphenol-S were dispersed in ammonia water. Deionized water was continuously added and stirred thoroughly to dissolve the resin. The final homogeneous system was then pH=8.0. 0.5g of tetraethyl orthosilicate was added and stirred for 2 hours. After separating the precipitate, it was aged at 110℃ for 12 hours to obtain the precursor.

[0072] (2) The precursor was heated to 800℃ and held for 1 h in Ar atmosphere, and then heated to 1400℃ and held for 2 h to obtain product 3. Product 3 was mixed with KOH at a mass ratio of 1:2 and heated to 850℃ and held for 1 h in Ar atmosphere. After removing the alkali from the activated product, the final product porous carbon material was obtained.

[0073] Preparation Example 6

[0074] This preparation example provides a porous carbon material and its preparation method.

[0075] (1) 20g of water-soluble phenolic resin and 15g of bisphenol-S were dispersed in ammonia water. Deionized water was continuously added and stirred thoroughly to dissolve the resin. The final homogeneous system was stirred for 2 hours. After separating the precipitate, it was aged at 110°C for 12 hours to obtain the precursor.

[0076] (2) The precursor was heated to 800℃ and held for 1 h in Ar atmosphere, and then heated to 1400℃ and held for 2 h to obtain product 3. Product 3 was mixed with KOH at a mass ratio of 1:2 and heated to 850℃ and held for 1 h in Ar atmosphere. After removing the alkali from the activated product, the final product porous carbon material was obtained.

[0077] Preparation Example 7

[0078] This preparation example provides a porous carbon material and its preparation method.

[0079] (1) 20g of water-soluble phenolic resin and 18g of hexamethylenetetramine were dispersed in ammonia water, and deionized water was continuously added. The mixture was stirred and dissolved until the final homogeneous system pH=8.0 was reached. After stirring for 2 hours, the precipitate was separated and aged at 110℃ for 12 hours to obtain the precursor.

[0080] (2) After uniformly mixing the precursor and zinc chloride at a mass ratio of 1:2, the temperature was raised to 350℃ and held for 2 hours under Ar atmosphere, then raised to 800℃ and held for 1 hour, and then raised to 1400℃ and held for 2 hours to obtain the final product, porous carbon material.

[0081] Comparative Preparation Example 1

[0082] This comparative preparation example provides a porous carbon material and its preparation method.

[0083] The difference from Preparation Example 1 is that in this preparation example, step (2) is replaced by: uniformly mixing the precursor and zinc chloride at a mass ratio of 1:2, and then heating to 1400℃ and holding for 4 hours under an Ar atmosphere to obtain porous carbon material.

[0084] Examples 1-7

[0085] This embodiment provides a method for preparing silicon-carbon composite materials using the porous carbon materials provided in Preparation Examples 1-7.

[0086] 5g of the prepared porous carbon material was placed in a stainless steel high-sealing muffle furnace, and the vacuum was evacuated to <10Pa and maintained for 10min. High-purity argon (99.999%) was used as the carrier gas flow at a flow rate of 60mL / min, and high-purity silane (99.9999%) was used as the silicon source at a flow rate of 50mL / min. The two were introduced into the furnace cavity together, and the deposition reaction was carried out at 475℃.

[0087] The reaction times for Examples 1-7 were 80 min, 80 min, 60 min, 100 min, 80 min, 60 min, and 60 min, respectively. After the reaction was completed, the flow of high-purity silane was stopped, while the flow of high-purity argon was maintained until the furnace temperature dropped to room temperature, at which point the sample could be removed.

[0088] Comparative Example 1

[0089] This comparative example provides a method for preparing silicon-carbon composite materials.

[0090] The difference from Example 1 is that, in this comparative example, the porous carbon material used in the example is replaced with the porous carbon material provided in Comparative Example 1.

[0091] Performance Test 1

[0092] The silicon-carbon composite materials provided in the examples and comparative examples were used to prepare lithium-ion half-cells, and their performance was tested as follows:

[0093] (1) The material mass ratio for making silicon-carbon electrodes is active material / conductive agent (acetylene black) / binder (CMC) = 8 / 1 / 1, and 0.1% single-walled carbon nanotubes are added. After grinding and mixing for 30 minutes, a uniform slurry is formed. Then, it is uniformly coated onto copper foil using a 200μm preparation device. After drying the solvent in a vacuum oven at 120℃ for 12 hours, it is repeatedly rolled and compacted using a roller press and cut into 12mm electrode discs using a slicer for later use.

[0094] (2) Lithium-ion half-cell assembly: The electrode sheets were weighed one by one and transferred to a glove box protected by inert gas for battery assembly. The button cell used was CR2032, the electrolyte was 1M LiPF6 dissolved in DEC, EC and FEC (v / v / v = 1:1:0.05), and the separator was polypropylene Celgard 2500.

[0095] Electrochemical performance testing: The assembled battery was subjected to constant current charge-discharge experiments in a Blue & Newway tester, and the specific capacity and cycle stability of the material were tested under 0.1C conditions.

[0096] The test results are shown in Table 1. The charge / discharge capacity is expressed in mAh / g.

[0097] Table 1

[0098]

[0099] Note: The oxygen content of double bonds (%) refers to the proportion of oxygen content in double bonds to the total oxygen content (%).

[0100] As can be seen from the examples and performance tests, the porous carbon material provided in this disclosure can effectively control the generation of silicon oxide and silicon oxide, thereby enabling the final silicon-carbon composite anode material to have excellent initial coulombic efficiency and capacity, and high cycle stability. After 20 cycles, the capacity retention rate can still reach more than 50%, and after 100 cycles, the optimal capacity retention rate can still reach more than 45%.

[0101] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0102] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a porous carbon material, characterized in that, The preparation method includes the following steps: (1) After dispersing the organic precursor in a solvent, an additive is added, and then the mixture is mixed with an alkali source and a crosslinking agent and dried to obtain a pretreated product; the additive is selected from silicate compounds; the organic precursor is selected from soluble phenolic polymers; (2) The pretreated product is activated and carbonized to obtain the porous carbon material; Step (2) includes: The pretreated product is mixed with zinc chloride and activated at 300-450℃ for 1-1.5 h, then carbonized at 1200-1400℃ for 0.5-2 h to obtain the porous carbon material. or: The pretreated product is mixed with zinc chloride and carbonized at 1200-1400℃ for 0.5-2 h, and then mixed with hydroxide and activated at 700-900℃ for 0.5-2 h to obtain the porous carbon material. or: The pretreated product is mixed with zinc chloride and activated for the first time at 300-450℃ for 1-1.5 h. The temperature is then increased to 1200-1400℃ for carbonization for 0.5-2 h. The product is then mixed with hydroxide and activated for the second time at 700-900℃ for 0.5-2 h to obtain the porous carbon material.

2. The preparation method according to claim 1, characterized in that, The additive is added at a mass of 1%-10% of the organic precursor, and the solvent is water.

3. The preparation method according to claim 1 or 2, characterized in that, The alkaline source is selected from any one or a combination of at least two of ammonia, urea, or sodium carbonate. And / or, the crosslinking agent is selected from hexamethylenetetramine and / or bisphenol crosslinking agents.

4. The preparation method according to claim 1 or 2, characterized in that, In step (1), the amount of alkali source added is such that the pH value of the mixed solution is 7.5-9; And / or, the mass ratio of the organic precursor to the crosslinking agent is 1:0.1-1.

5. The preparation method according to claim 1 or 2, characterized in that, In step (2), both activation and carbonization are carried out under an inert atmosphere.

6. The preparation method according to claim 5, characterized in that, The mass ratio of the pretreated product to the zinc chloride is 1:2-6; And / or, the mass ratio of the pretreated product to the hydroxide is 1:1-6; And / or, the hydroxide is selected from any one or a combination of at least two of potassium hydroxide, sodium hydroxide, or lithium hydroxide.

7. The porous carbon material prepared by the preparation method according to any one of claims 1-6.

8. The porous carbon material according to claim 7, characterized in that, The specific surface area of ​​the porous carbon material is 50-2500 m². 2 / g, the surface has pores with a diameter of 0.7-100 nm, the total oxygen content on the surface is ≤15 wt%, and the double bond oxygen content does not exceed 60% of the total oxygen content.

9. A silicon-carbon composite anode material, characterized in that, The silicon-carbon composite anode material comprises the porous carbon material as described in claim 7 or 8 and elemental silicon deposited on the surface of the porous carbon material.

10. A negative electrode sheet, characterized in that, It includes the porous carbon material as described in claim 7 or 8 or the silicon-carbon composite anode material as described in claim 9.

11. An electrochemical device, characterized in that, It includes the porous carbon material of claim 7 or 8, the silicon-carbon composite anode material of claim 9, or the anode sheet of claim 10.

12. A vehicle, characterized in that, It includes the negative electrode sheet of claim 10 or the electrochemical device of claim 11.

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