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

Abstract

The invention discloses a porous carbon material, a silicon-carbon negative electrode material, a preparation method, application and a battery. The preparation method comprises the following steps: (1) heating and curing a mixture of thermosetting phenolic resin and zinc oxide, slowly heating in a reducing atmosphere to reduce zinc oxide and gradually volatilize, and cooling to obtain microporous carbon; (2) carrying out etching pore-forming and doping on the microporous carbon to obtain microporous / mesoporous porous carbon; and (3) calcining the microporous / mesoporous porous carbon and a sulfur-phosphorus doping agent to obtain the porous carbon material. The porous carbon material prepared by the invention can realize larger pore capacity and silicon loading capacity, and provides a carbon carrier for a high-capacity silicon-carbon negative electrode material; and the preparation method is high in etching efficiency and good in doping effect, and the production efficiency can be improved.

Description

Technical Field

[0001] This invention specifically relates to a porous carbon material, a silicon-carbon anode material, its preparation method, applications, and batteries. Background Technology

[0002] Lithium-ion batteries, as crucial energy storage devices, are widely used in electric vehicles, portable electronic devices, and other fields. With the ever-increasing market demand for high-energy-density, long-cycle-life lithium-ion batteries, more stringent requirements are being placed on the performance of battery electrode materials. Silicon-carbon anode materials, with their advantages of high theoretical specific capacity and low cost, have become a popular alternative to traditional graphite anode materials, potentially driving new breakthroughs in lithium-ion battery performance. However, silicon-carbon anode materials still face many challenges in practical applications. Among these, how to prepare high-performance porous carbon materials as silicon carriers to alleviate the volume expansion problem of silicon during charging and discharging, and to improve the conductivity and ion transport efficiency of the materials, has become a focus of attention for researchers and industry.

[0003] Currently, the main methods for preparing porous carbon materials include physical activation, chemical activation, and template methods. Physical activation typically uses water vapor or carbon dioxide as activators, reacting with the carbon material at high temperatures to form a porous structure through etching. Chemical activation utilizes chemical reagents such as potassium hydroxide or phosphoric acid to react with the carbon source at high temperatures, thereby forming a porous structure. However, due to the randomness of the reaction during activation, the etching agent can only gradually etch the carbon material surface, making it difficult to precisely control the size and distribution of pores. This results in an uneven pore structure in the prepared porous carbon material, affecting its overall performance. Template methods involve introducing a template agent to construct a specific structure within the carbon source, followed by template removal to obtain a porous carbon material with a specific pore structure. Template methods can precisely control the size, shape, and distribution of pores, producing high-performance porous structures. However, existing template agents often present challenges in removal, such as difficulty and residual impurities, which negatively impact the material's performance.

[0004] Furthermore, heteroatom doping is a key method for improving the electrochemical performance of porous carbon materials in functional modification. However, existing preparation processes generally suffer from the problem of dopants failing to effectively penetrate the porous carbon interior. On the one hand, pores formed by physical or chemical activation may have poor connectivity and an excessively high micropore ratio, making it difficult for low-toxicity and relatively safe sulfur and phosphorus dopants, which are usually solids, to diffuse and penetrate deep into the material. On the other hand, impurities remaining from template methods may block some pore channels, further hindering the uniform distribution of dopants. Ultimately, this results in low heteroatom doping levels and uneven distribution, failing to fully exert their regulatory effect on electronic structure and limiting the improvement of conductivity and interface stability of porous carbon supports. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the defects of existing porous carbon etching methods, such as uneven pore structure, low etching efficiency, and poor heteroatom doping effect. This invention provides a porous carbon material, a silicon-carbon anode material, a preparation method, applications, and batteries. The porous carbon material prepared by this invention can achieve greater pore capacity, silicon loading, conductivity, and cycle stability, providing a carbon support for high-capacity silicon-carbon anode materials. Furthermore, the preparation method is simple and has high etching efficiency, which can improve production efficiency.

[0006] In the preparation of porous carbon materials, this invention first constructs a connected microporous structure within the carbon source using a zinc oxide template agent. Then, through further etching to create pores and sulfur-phosphorus co-doping, it achieves multi-level pore structure control and synergistic heteroatom doping, improving pore-forming and doping effects. During the heating reduction process, zinc oxide undergoes a reduction reaction, and the generated zinc fully volatilizes at high temperatures, leaving uniformly distributed micropores within the carbon material, forming a connected microporous structure. By constructing a connected microporous structure within the carbon material before etching to create pores, the etchant can penetrate deep into the material, improving porosity, pore uniformity, and etching efficiency. Finally, sulfur-phosphorus doping is used to dope the porous carbon with interconnected micropores / mesopores, making it easier for the dopant to penetrate deep into the pores for efficient doping. Further pore-forming reactions occur during the doping process, ultimately enabling the silicon-carbon anode prepared based on the porous carbon of this invention to achieve high capacity, high rate capability, and high stability.

[0007] The present invention solves the above-mentioned technical problems through the following technical solutions:

[0008] This invention provides a method for preparing porous carbon materials, which includes the following steps:

[0009] (1) The mixture of thermosetting phenolic resin and zinc oxide is first heated and cured, and then the temperature is slowly increased in a reducing atmosphere to reduce the zinc oxide and gradually volatilize it. After cooling, microporous carbon is obtained.

[0010] (2) The microporous carbon is etched to create pores, thereby obtaining microporous mesoporous porous carbon;

[0011] (3) The microporous mesoporous carbon and sulfur-phosphorus dopants are calcined to obtain the porous carbon material.

[0012] In step (1), the thermosetting phenolic resin can be conventional in the art, preferably with a solid content ≥80%.

[0013] In step (1), the zinc oxide is preferably zinc oxide whiskers and / or zinc oxide nanowires.

[0014] In some specific embodiments, the zinc oxide is a tetraneedle-shaped zinc oxide whisker with a length of 10-50 μm and a diameter of 0.3-5 μm, or a zinc oxide nanowire with a diameter of 30-50 nm and a length of 5-20 μm.

[0015] When zinc oxide uses tetraneedle-shaped zinc oxide whiskers, the structure of the zinc oxide whiskers is a centrally symmetrical four-armed needle-like structure. The four-arm structure can directly form a natural three-dimensional spatial network, which can guide the matrix material to be uniformly coated or filled, avoiding the structural unevenness problem caused by the easy agglomeration of traditional granular templates. The surface of ZnO whiskers naturally has active groups such as hydroxyl (-OH), which can chemically react with phenolic resin to form a stable interface bond. Furthermore, the mechanical strength of zinc oxide itself enhances the stability of carbon precursors and reduces the degree of structural collapse and particle breakage during heating and other treatment processes.

[0016] In step (1), the mass ratio of the thermosetting phenolic resin to the zinc oxide can be 100:(1-20), preferably 100:(1-10), for example 100:3, 100:4, 100:5 or 100:8.

[0017] In step (1), the heat curing generally refers to curing the raw material under heating. The heat curing is generally carried out in an air atmosphere. The heat curing is generally carried out in a muffle furnace, sintering furnace, or tube furnace. The heat curing temperature can be 120℃-180℃, for example 125℃, 130℃, 135℃, or 140℃; the heat curing time can be 0.5h-4h, for example 1h or 2h.

[0018] In step (1), preferably no cooling treatment is required after the heating and curing. The temperature is directly increased from the heating and curing temperature to reduce the zinc oxide and gradually volatilize it.

[0019] In step (1), the reducing atmosphere is generally hydrogen. According to conventional practice, during the slow heating process that reduces and gradually volatilizes zinc oxide, an inert gas can be simultaneously introduced in addition to the reducing atmosphere, i.e., the process is carried out in a mixed atmosphere of reducing and inert gases. The flow rate ratio of the reducing atmosphere to the inert atmosphere can be 1:(5-15), for example, 1:10. The flow rate of the reducing atmosphere can be 50-200 sccm, for example, 80 sccm, 100 sccm, or 120 sccm.

[0020] In step (1), preferably, the temperature is slowly raised to 550-700°C (e.g., 600°C or 650°C) in the reducing atmosphere to reduce zinc oxide and gradually volatilize it; more preferably, after slowly raising the temperature to 550-700°C in the reducing atmosphere, the temperature is immediately lowered without holding the temperature. The cooling rate can be conventional in the art, such as natural cooling to room temperature.

[0021] In step (1), preferably, the zinc oxide is slowly heated in the reducing atmosphere at a heating rate of 1-20℃ / min to reduce and gradually volatilize, for example, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 8℃ / min or 10℃ / min, more preferably 1-5℃ / min.

[0022] In some specific implementations, the temperature is slowly increased to 550-700°C in a reducing atmosphere at a heating rate of 1-10°C / min to reduce zinc oxide and gradually volatilize it.

[0023] In some specific embodiments, the temperature is slowly increased to 550-700°C in a reducing atmosphere at a heating rate of 1-10°C / min, based on the temperature at which the heating and curing are performed, so that the zinc oxide is reduced and gradually volatilized.

[0024] In some preferred embodiments, the temperature is slowly increased to 550-700°C in a reducing atmosphere at a heating rate of 1-10°C / min, and then immediately cooled down without holding the temperature.

[0025] In some preferred embodiments, the temperature is slowly increased to 550-700°C in a reducing atmosphere at a heating rate of 1-5°C / min, and then immediately cooled down without holding the temperature.

[0026] In one specific implementation scheme, the temperature is slowly increased to 600°C in a reducing atmosphere at a heating rate of 3°C / min, and then immediately cooled down without holding the temperature.

[0027] In one specific implementation, the temperature is slowly increased to 600°C in a reducing atmosphere at a heating rate of 3°C / min based on the heating and curing temperature, and then immediately cooled down without heat preservation.

[0028] In step (2), the microporous carbon preferably needs to be mechanically crushed before the etching and hole-forming process, generally crushed to a particle size of about 1 mm.

[0029] In step (2), the etching method for creating holes can be one or more of the following: alkaline etching, water vapor etching, and carbon dioxide etching.

[0030] The alkaline etching method generally refers to etching the microporous carbon with an alkali to create pores, and preferably includes the following process: heating the mixture of the microporous carbon and the alkali under an inert atmosphere.

[0031] The alkali may be one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, potassium carbonate, and potassium bicarbonate. The mass ratio of the microporous carbon to the alkali may be (0.5-3):1, preferably (0.5-2):1, for example 0.8:1, 1:1, or 2:1.

[0032] The inert gas generally refers to a gas that does not react with the reactants, such as nitrogen, argon, or helium. The rate of heating to the temperature for the heat treatment can be 1-5°C / min. The temperature for the heat treatment can be 500-1200°C, for example, 600°C, 650°C, 700°C, or 850°C. The duration of the heat treatment can be 1-12 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or 8 hours.

[0033] According to conventional practice in the art, washing and drying are generally required after the heat treatment. The solvent used for washing can be conventional in the art, such as deionized water. After washing, the pH of the filtrate should generally be below 8. The drying operation and conditions can be conventional in the art; the drying temperature can be 80-120°C, for example 100°C; the drying time can be 4-12 hours, for example 6 hours or 8 hours.

[0034] The water vapor etching method generally refers to using water vapor to etch and create pores in the microporous carbon, and preferably includes the following process: heating the microporous carbon in a water vapor atmosphere.

[0035] The inert gas generally refers to a gas that does not react with the reactants, such as nitrogen, argon, or helium. The flow rate of the water vapor can be 20-100 mL / min, for example, 30 mL / min, 40 mL / min, 50 mL / min, or 60 mL / min. Preferably, in the heat treatment process, in addition to water vapor, an inert gas can also be introduced simultaneously, that is, the microporous carbon is heated in a mixture of water vapor and inert gas. The flow rate ratio of the inert gas to water vapor is (1-10):1, for example, 3:1, 5:1, or 6:1.

[0036] The temperature of the heat treatment can be 800-1100℃, for example 900℃, 950℃ or 1000℃; the time of the heat treatment can be 0.5-3h, for example 1h or 2h; the rate of heating to the temperature of the heat treatment can be 1-5℃ / min.

[0037] The carbon dioxide etching method generally refers to using carbon dioxide to etch and create pores in the microporous carbon, and preferably includes the following process: heating the microporous carbon in a carbon dioxide atmosphere.

[0038] The flow rate of carbon dioxide can be 50-300 mL / min, for example 80 mL / min, 100 mL / min, 150 mL / min, or 200 mL / min. Preferably, in the process of heating treatment, in addition to carbon dioxide, an inert gas can also be introduced simultaneously, that is, the microporous carbon is heated in a mixture of carbon dioxide and inert gas. The flow rate ratio of the inert gas to carbon dioxide is (1-5):1, for example 2:1 or 3:1.

[0039] The temperature of the heat treatment can be 850-1200℃, for example 900℃, 1000℃ or 1050℃; the time of the heat treatment can be 2-12h, for example 3h or 6h; the rate of heating to the temperature of the heat treatment can be 1-5℃ / min.

[0040] In step (3), the sulfur-phosphorus dopant generally refers to a compound containing both sulfur and phosphorus, or a mixture of elemental phosphorus and elemental sulfur, preferably one or more of phosphorus pentasulfide, phosphorus trisulfide, phosphorus heptasulfide, phosphorus pentasulfide and "a mixture of red phosphorus and elemental sulfur".

[0041] In step (3), the mass ratio of the microporous mesoporous carbon to the sulfur-phosphorus dopant can be (3-10):1, for example 4:1, 5:1, 6:1, 8:1 or 9:1.

[0042] In step (3), the microporous mesoporous carbon and the sulfur-phosphorus dopant are generally mixed evenly before calcination. The calcination is generally carried out in an inert gas atmosphere, such as a nitrogen or argon atmosphere. The calcination temperature can be 600-1000℃, for example 700℃, 750℃, 800℃, 850℃ or 900℃; the calcination time can be 0.5-3h, for example 1h or 2h; the rate of heating to the calcination temperature can be 1-5℃ / min.

[0043] In step (3), sieving is generally required after calcination. After sieving, the particle size D of the porous carbon... 50 The optimal range is 30-50 μm.

[0044] In this invention, the particle size D of the porous carbon material 50 It can be 30-50μm.

[0045] The present invention also provides a porous carbon material prepared by the preparation method described above.

[0046] This invention also provides a method for preparing a silicon-carbon composite material, which includes the following steps:

[0047] Silicon-carbon composite materials were obtained by silane deposition of the porous carbon material as described above.

[0048] In this invention, the porous carbon material is preferably subjected to vacuum degassing and heating activation before the silane deposition.

[0049] The vacuum degassing process typically requires evacuation to a level below 5 × 10⁻³ Pa.

[0050] The heating activation is typically performed in a tube furnace. The heating activation is generally carried out under an inert atmosphere, such as argon. The heating activation temperature can be 300-500℃, for example, 400℃. The heating activation time can be 0.5-4 hours, for example, 1 hour or 2 hours. According to conventional practice, when the heating activation temperature is not higher than the silane deposition temperature, the temperature can generally be directly raised to the silane deposition temperature for silane deposition without cooling after heating activation; when the heating activation temperature is higher than the silane deposition temperature, the temperature is generally directly lowered to the silane deposition temperature for silane deposition after heating activation.

[0051] In this invention, the temperature for silane deposition can be 300-700℃, for example 350℃, 400℃ or 500℃. The deposition time can be 1-8h, for example 2h or 3h.

[0052] In this invention, the silane deposition is preferably carried out in a mixture of silane and an inert gas. The inert gas is, for example, argon. The flow rate of the silane is preferably 10-50 sccm, for example, 20 sccm, 25 sccm, or 30 sccm. The flow rate of the inert gas is preferably 50-200 sccm, for example, 80 sccm, 100 sccm, 120 sccm, or 150 sccm.

[0053] The total pressure of the mixed gas can be 100-2000 Pa, for example 200 Pa or 500 Pa.

[0054] In one specific implementation, during the silane deposition process, the silane flow rate is 20 sccm and the argon flow rate is 100 sccm.

[0055] The present invention also provides a silicon-carbon composite material prepared by the preparation method described above.

[0056] The present invention also provides an application of porous carbon materials or silicon-carbon composite materials as described above in battery materials.

[0057] The present invention also provides a battery comprising the porous carbon material or silicon-carbon composite material as described above.

[0058] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0059] The reagents and raw materials used in this invention are all commercially available.

[0060] The positive and progressive effects of this invention are as follows:

[0061] The porous carbon material prepared by this invention can achieve a larger pore capacity and silicon loading, providing a carbon support for high-capacity silicon-carbon anode materials; and the preparation method has high etching efficiency, which can improve production efficiency. Attached Figure Description

[0062] Figure 1 The image shows a SEM image of the porous carbon material prepared in Example 1. Detailed Implementation

[0063] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0064] The thermosetting phenolic resin used in Examples 1-8 and Comparative Examples 1-2 was PF2123 with a solid content ≥98%, purchased from Tianyu New Materials; the tetraneedle-shaped zinc oxide nanowhiskers were FF-JY510 with a length of 10-50μm, a purity ≥99.5%, and a diameter of 0.3-5μm, purchased from Hangzhou Jiayou New Materials; the sintering furnace was manufactured by Bangshida, model BSDS-1200.

[0065] Example 1

[0066] Step (1): Mix 100 parts by mass of thermosetting phenolic resin and 5 parts by mass of zinc oxide nanocrystals evenly, then put the sample into a crucible and place it in a sintering furnace. First, heat the temperature to 130℃ in an air atmosphere and hold it for 1 hour to cure the phenolic resin. Then, in a mixed atmosphere of nitrogen and hydrogen (nitrogen flow rate of 1000 sccm and hydrogen flow rate of 100 sccm), slowly heat the temperature to 600℃ from 130℃ at a heating rate of 3℃ / min. Then, immediately cool down without holding the temperature and let it cool naturally to room temperature. Zinc oxide will be reduced and gradually volatilize. After the reaction is complete, microporous carbon is obtained.

[0067] Step (2): After mechanically pulverizing the microporous carbon to a particle size of approximately 1 mm, mix it evenly with potassium hydroxide (granular, purity ≥85%) at a mass ratio of 1:1. Place the mixture in a sintering furnace and heat it to 650 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, and hold it at this temperature for 2 hours under a nitrogen atmosphere. After the reaction is complete, cool it to room temperature and remove the sample.

[0068] Step (3): Immerse the sample obtained in step (2) in deionized water and wash it three times with a magnetic stirrer at 500 rpm until the pH of the filtrate is below 8. Then, filter the sample using a vacuum filter to collect the porous carbon solid. Dry the porous carbon solid in an oven at 100°C for 6 hours, then mix it with P2S5 at a mass ratio of 5:1. Place the mixture in a sintering furnace and heat it to 850°C at a heating rate of 5°C / min under a nitrogen atmosphere and hold it at that temperature for 1 hour. After the reaction is complete, cool it to room temperature and remove the sample. Finally, use a sieve separator for vibration classification to obtain the particle size D. 50 It is a porous carbon material with a diameter of 30-50 μm.

[0069] Example 2

[0070] Step (1): Same as in Example 1;

[0071] Step (2): After mechanically crushing the microporous carbon, place it in a sintering furnace. First, under the protection of nitrogen (flow rate 300 mL / min), heat it to 950°C at a heating rate of 5°C / min. Then, while nitrogen is continuously introduced, water vapor with a flow rate of 50 mL / min is introduced in addition. The activation reaction is carried out at this temperature for 1 hour. After the reaction is completed, it is naturally cooled to room temperature and the sample is taken out.

[0072] The process of introducing water vapor is as follows: Deionized water is delivered to the vaporizer, the temperature is set to 200℃ to ensure that the liquid water can be vaporized instantly, nitrogen is continuously introduced at a flow rate of 300mL / min, and the vaporizer is heated to the target temperature at a rate of 5℃ / min. The water flow rate is set to 50mL / min through the liquid mass flow controller.

[0073] Step (3): Mix the sample obtained in step (2) with P2S5 at a mass ratio of 5:1. Place the mixture in a sintering furnace and heat it to 850°C at a heating rate of 5°C / min under a nitrogen atmosphere, holding it at that temperature for 1 hour. After the reaction is complete, cool it to room temperature and remove the sample. Finally, use a sieve separator for vibration classification to obtain the particle size D. 50 It is a porous carbon material with a diameter of 30-50 μm.

[0074] Example 3

[0075] Step (1): Same as in Example 1;

[0076] Step (2): After mechanically crushing the microporous carbon, place it in a sintering furnace. First, under the protection of nitrogen (flow rate 300 mL / min), heat it to 1050℃ at a heating rate of 5℃ / min. Then, while nitrogen is continuously introduced, additional carbon dioxide at a flow rate of 150 mL / min is introduced. The activation reaction is carried out at this temperature for 3 hours. After the reaction is completed, cool it to room temperature and take out the sample.

[0077] Step (3): Mix the sample obtained in step (2) with P2S5 at a mass ratio of 5:1. Place the mixture in a sintering furnace and heat it to 850°C at a heating rate of 5°C / min under a nitrogen atmosphere, and hold it at this temperature for 1 hour under a nitrogen atmosphere. After the reaction is complete, cool it to room temperature and remove the sample. Finally, use a sieve separator for vibration classification to obtain the particle size D. 50 It is a porous carbon material with a diameter of 30-50 μm.

[0078] Example 4

[0079] Compared with Example 1, except that the 5 parts by mass of zinc oxide nanocrystals in step (1) are replaced with 3 parts by mass of zinc oxide nanocrystals, all other operations and conditions are the same as in Example 1.

[0080] Example 5

[0081] Compared with Example 1, except that the heating rate in step (1) under a mixed atmosphere of nitrogen and hydrogen was adjusted from 3°C / min to 5°C / min, all other operations and conditions were the same as in Example 1.

[0082] Example 6

[0083] Compared with Example 1, except that the heating rate in step (1) under a mixed atmosphere of nitrogen and hydrogen was adjusted from 3°C / min to 10°C / min, all other operations and conditions were the same as in Example 1.

[0084] Example 7

[0085] Compared with Example 1, except that the heating reaction time in step (2) is changed from 2h to 4h, all other operations and conditions are the same as in Example 1.

[0086] Example 8

[0087] Compared with Example 1, except that the heating reaction time in step (2) is changed from 2h to 6h, all other operations and conditions are the same as in Example 1.

[0088] Comparative Example 1

[0089] Compared with Example 1, except that zinc oxide nanocrystals are not added in step (1), all other operations and conditions are the same as in Example 1.

[0090] Comparative Example 2

[0091] Step (1): 100 parts by weight of thermosetting phenolic resin are placed into a crucible and placed in a sintering furnace. The temperature is raised to 130°C in an air atmosphere and held for 1 hour to cure the phenolic resin.

[0092] Step (2): Same as in Example 1.

[0093] Step (3): Same as in Example 1.

[0094] Comparative Example 3

[0095] Step (1): Compared with Example 1, except that zinc oxide nanocrystals were not added, all other operations and conditions were the same as in Example 1;

[0096] Step (2): Same as in Example 1;

[0097] Step (3): The sample obtained in step (2) is subjected to vibration classification using a sieve to obtain the particle size D. 50 It is a porous carbon material with a diameter of 30-50 μm.

[0098] Effect Example

[0099] (1) Characterization of material properties

[0100] Figure 1 The image shows a SEM image of the porous carbon prepared in Example 1. The porous carbon materials prepared in Examples 1 to 8 and Comparative Examples 1-3 were subjected to BET tests using an ASAP2020 surface area and pore size analyzer. The test results are shown in Table 1.

[0101] (2) Electrochemical performance testing

[0102] Silicon-carbon composite materials were prepared by silane deposition using the porous carbon materials obtained in Examples 1-8 and Comparative Examples 1-3, respectively. The preparation method was as follows: the porous carbon materials were placed in a tube furnace for vacuum degassing, the vacuum was evacuated to 5×10-3 Pa, argon gas was introduced (flow rate 50 sccm), and the temperature was raised to 400℃ and held for 1 hour; then silane deposition was carried out in a mixed gas of silane and argon, the deposition temperature was 500℃, the silane flow rate was 20 sccm, the argon flow rate was 100 sccm, the total pressure was 200 Pa, and the deposition time was 120 minutes. After deposition, the materials were sealed and stored in a glove box.

[0103] The electrochemical testing method is as follows: Silicon-carbon composite material prepared according to the above method, conductive carbon black, and sodium carboxymethyl cellulose are mixed at a mass ratio of 80:10:10. Deionized water is added to form a slurry, which is then coated onto a 10 μm thick copper foil. After vacuum drying at 120℃ for 12 hours, the mixture is punched into a 12 mm diameter electrode sheet. The areal density of the active material on the electrode sheet is 3.0 mg / cm³. 2The negative electrode was lithium metal, and a 1 mol / L LiPF6 electrolyte was used (solvents were EC, DMC, and FEC, EC:DMC = 1:1 (volume ratio), and FEC accounted for 5% of the total solvent volume). CR2032 button cells were assembled in an argon glove box, and constant current charge / discharge tests were performed on a LAND CT2001A battery testing system, with a test voltage range of 0.01-1.5V (vs. Li / Li). + The current density was 0.1C (1C = 2000mA / g), and the test results are shown in Table 1.

[0104] Table 1

[0105]

[0106]

[0107] Based on the above experimental results, it can be seen that the porous carbon prepared by this invention has a large pore volume and a large specific surface area, and the prepared silicon-carbon composite material has better discharge specific capacity and cycle capacity retention. In Comparative Example 1, due to the absence of zinc oxide template agent, it is difficult to achieve sufficient pore formation through etching alone, making it difficult for sulfur phosphide to enter the carbon source, resulting in a decrease in specific surface area, pore capacity, and poor doping effect, and the prepared silicon-carbon composite material has poor specific capacity. In Comparative Example 2, due to the absence of zinc oxide template agent and the lack of pre-carbonization of phenolic resin before alkaline etching, the porous carbon has poor specific surface area, pore capacity, and pore structure uniformity, resulting in poor doping effect and reduced specific capacity and cycle life of the silicon-carbon anode material. In Comparative Example 3, the absence of zinc oxide and sulfur-phosphorus doping leads to poor pore formation effect of the porous carbon and poor electrochemical performance when applied to silicon-carbon anode materials.

[0108] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A method for preparing porous carbon materials, characterized in that, Includes the following steps: (1) The mixture of thermosetting phenolic resin and zinc oxide is first heated and cured, and then the temperature is slowly increased in a reducing atmosphere to reduce the zinc oxide and gradually volatilize it. After cooling, microporous carbon is obtained. (2) The microporous carbon is etched to create pores, thereby obtaining microporous mesoporous porous carbon; (3) The microporous mesoporous carbon and sulfur-phosphorus dopants are calcined to obtain the porous carbon material.

2. The method for preparing porous carbon materials as described in claim 1, characterized in that, Step (1) satisfies one or more of the following conditions: (1) The zinc oxide is tetraneedle-shaped zinc oxide whiskers and / or zinc oxide nanowires; (2) The mass ratio of the thermosetting phenolic resin to the zinc oxide is 100:(1-20), preferably 100:(1-10), for example 100:3, 100:4, 100:5 or 100:8; (3) The heating and curing is carried out in an air atmosphere; (4) The temperature for heat curing is 120℃-180℃, for example 125℃, 130℃, 135℃ or 140℃; (5) The heating and curing time is 0.5h-4h, for example 1h or 2h; (6) No cooling treatment is required after the heating and curing. The temperature is directly increased from the heating and curing temperature to reduce the zinc oxide and gradually volatilize it. (7) The reducing atmosphere is hydrogen; (8) The flow rate of the reducing atmosphere is 50-200 sccm, for example 80 sccm, 100 sccm or 120 sccm; (9) In the reducing atmosphere, the temperature is slowly raised to 550-700°C, for example, 600°C or 650°C, so that zinc oxide is reduced and gradually volatilized; preferably, after the temperature is slowly raised to 550-700°C in the reducing atmosphere, the temperature is immediately lowered without heat preservation. (10) The zinc oxide is slowly heated in the reducing atmosphere at a heating rate of 1-20℃ / min to reduce and gradually volatilize, for example, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 8℃ / min or 10℃ / min, preferably 1-5℃ / min.

3. The method for preparing porous carbon materials as described in claim 1, characterized in that, The preparation method satisfies one or more of the following conditions: (1) In step (2), the etching method for creating holes is one or more of the following: alkaline etching, water vapor etching, and carbon dioxide etching. (2) In step (3), the sulfur-phosphorus dopant is one or more of phosphorus pentasulfide, phosphorus trisulfide, phosphorus heptasulfide, phosphorus pentasulfide and "a mixture of red phosphorus and elemental sulfur"; (3) In step (3), the mass ratio of the microporous mesoporous carbon to the sulfur-phosphorus dopant is (3-10):1, for example 4:1, 5:1, 6:1, 8:1 or 9:1; (4) In step (3), the calcination temperature is 600-1000℃, for example 700℃, 750℃, 800℃, 850℃ or 900℃; (5) In step (3), the calcination time is 0.5-3h, for example 1h or 2h.

4. The method for preparing porous carbon materials as described in claim 3, characterized in that, The etching process satisfies one or more of the following conditions: (1) The alkaline etching method includes the following process: heating the mixture of microporous carbon and alkali under an inert atmosphere; The alkali is preferably one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, potassium carbonate, and potassium bicarbonate; the mass ratio of the microporous carbon to the alkali is preferably (0.5-3):1, more preferably (0.5-2):1, for example 0.8:1, 1:1, or 2:1; the temperature of the heat treatment is preferably 500-1200℃, for example 600℃, 650℃, 700℃, or 850℃; the time of the heat treatment is preferably 1-12h, for example 2h, 3h, 4h, 5h, 6h, or 8h; preferably, washing, drying, and sieving are also required after the heat treatment. (2) The water vapor etching method includes the following process: heating the microporous carbon in a water vapor atmosphere; The flow rate of the water vapor is preferably 20-100 mL / min, for example 30 mL / min, 40 mL / min, 50 mL / min, or 60 mL / min; preferably, the microporous carbon is heated in a mixture of water vapor and inert gas; the flow rate ratio of the inert gas to water vapor is preferably (1-10):1, for example 3:1, 5:1, or 6:1; the heating temperature is preferably 800-1100℃, for example 900℃, 950℃, or 1000℃; the heating time is preferably 0.5-3 h, for example 1 h or 2 h; preferably, sieving is performed after the heating treatment; (3) The carbon dioxide etching method includes the following process: heating the microporous carbon in a carbon dioxide atmosphere; The flow rate of the carbon dioxide is preferably 50-300 mL / min, for example 80 mL / min, 100 mL / min, 150 mL / min or 200 mL / min; preferably, the microporous carbon is heated in a mixture of carbon dioxide and an inert gas; the flow rates of the inert gas and carbon dioxide are preferably (1-5):1, for example 2:1 or 3:1; the heating temperature is preferably 850-1200℃, for example 900℃, 1000℃ or 1050℃; the heating time is preferably 2-12 h, for example 3 h or 6 h; preferably, the carbon is sieved after the heating treatment.

5. A porous carbon material prepared by a method according to any one of claims 1-4.

6. A method for preparing a silicon-carbon composite material, characterized in that, Includes the following steps: The porous carbon material as described in claim 5 is subjected to silane deposition to obtain a silicon-carbon composite material.

7. The method for preparing the silicon-carbon composite material as described in claim 6, characterized in that, The silane deposition satisfies one or more of the following conditions: (1) The temperature of the silane deposition is 300-700℃, for example 350℃, 400℃ or 500℃; (2) The silane deposition time is 1-8 hours, for example 2 hours or 3 hours; (3) The silane deposition is carried out in a mixture of silane and inert gas; The flow rate of the silane is preferably 10-50 sccm, for example 20 sccm, 25 sccm or 30 sccm; The flow rate of the inert gas is preferably 50-200 sccm, for example 80 sccm, 100 sccm, 120 sccm or 150 sccm.

8. A silicon-carbon composite material prepared by the method for preparing the silicon-carbon composite material as described in claim 6 or 7.

9. The application of a porous carbon material as described in claim 5 or a silicon-carbon composite material as described in claim 8 in battery materials.

10. A battery comprising the porous carbon material as claimed in claim 5 or the silicon-carbon composite material as claimed in claim 8.

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