A porous carbon material and silicon-carbon negative electrode material beneficial to silicon deposition, and a preparation method and application thereof

Abstract

The present application belongs to the field of lithium ion battery materials, and particularly relates to a porous carbon material beneficial to silicon deposition, a silicon-carbon negative electrode material, and a preparation method and application thereof. The porous carbon material has effective micro-mesoporous structure; the pore volume proportion of the effective micro-mesoporous structure in the porous carbon material is 90% or more; and the pore size of the effective micro-mesoporous structure is 0.35-10 nm. The key of the present application is to adopt a double activation method with addition of organic activator and inorganic activator, to precisely control the pore structure of the porous carbon material, to obtain the porous carbon material with high pore volume proportion (≥90%) of effective micro-mesoporous structure, to improve the deposition amount and electrochemical activity of nano-silicon in the silicon-carbon negative electrode material, so as to improve the reversible specific capacity and charge-discharge efficiency of the silicon-carbon negative electrode material, and to make the lithium ion battery have high energy density.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery materials, specifically relating to a porous carbon material and silicon-carbon anode material that facilitate silicon deposition, as well as their preparation methods and applications. Background Technology

[0002] Currently, one of the main power sources for electric or hybrid new energy vehicles is the on-board lithium-ion battery. The anode material for lithium-ion batteries is primarily artificial graphite, with an actual capacity of 300-350 mAh / g, close to its theoretical capacity of 372 mAh / g. This significantly limits the overall energy density of the battery and the potential for further improvements in the driving range of new energy vehicles. Furthermore, due to silicon's ultra-high theoretical lithium storage capacity of 4200 mAh / g, incorporating silicon into silicon-carbon composite materials for the anode of lithium-ion batteries represents a future trend in anode material technology. Some automakers have already begun using silicon-carbon anodes to produce cylindrical power batteries and have achieved vehicle delivery. It is expected that the penetration rate of silicon-carbon anode materials in consumer and power batteries will continue to increase, and demand is expected to continue to grow.

[0003] Current industry focus is on novel silicon-carbon material development strategies, including the deposition of nano-silicon through the vapor-phase pyrolysis of silane gas and the nanoscale composite of silicon and carbon. To achieve nanoscale silicon-carbon composites, it is necessary to develop corresponding porous carbon materials as precursors for silicon-carbon materials. This allows silane gas to be adsorbed and pyrolyzed through the porous structure of the carbon material to generate nano-silicon, thus preparing novel porous silicon-carbon anode materials. However, most porous carbon materials currently used in the industry are prepared by carbonization and activation of biomass raw materials. When using these as precursors to prepare silicon-carbon materials, the amount of silicon deposited is limited, and electrochemically active nano-silicon cannot be effectively formed. This results in a lack of significant improvement in the capacity performance of silicon-carbon anode materials in lithium-ion batteries, leading to low charge / discharge efficiency and energy density in lithium-ion batteries. Summary of the Invention

[0004] One of the objectives of this invention is to address the problems of low capacity and low charge / discharge efficiency of silicon-carbon anode materials prepared using existing porous carbon materials as precursors. This invention provides a porous carbon material that facilitates silicon deposition, and the silicon content ratio, reversible specific capacity, and charge / discharge efficiency of silicon-carbon anode materials prepared using this porous carbon material as a precursor are significantly improved.

[0005] The inventors of this invention, combining traditional gas-phase adsorption theory with repeated experiments, discovered that, besides specific surface area, the pore size of porous carbon materials is one of the parameters that significantly influences the physical adsorption process of gas molecules, including silanes. For example, the interaction between silane molecules and porous carbon undergoes the following three stages: As the partial pressure of silane gas gradually increases from zero, silane molecules first fill the micropores with a pore size distribution of less than 2 nm. Due to the interaction of the dense pore walls, the silane molecules filled in the micropores are in a non-liquid state. This stage of filling is an interaction between the micropore walls. The overlapping of potential energies leads to filling of micropores when the relative pressure is <0.01. As the partial pressure of silane gas continues to increase, within a certain mesopore size range of 2 nm or larger, silane molecules remain on the inner surface of the pores via monolayer adsorption. When the adsorption space accommodates more than one layer of molecules, not all silane molecules are in direct contact with the pore surface, resulting in multilayer adsorption. Subsequently, as the partial pressure of silane gas continues to increase, silane gas molecules can hardly remain on the pore surface anymore, leading to capillary condensation within the mesopore channels. In summary, for silane as a specific gas molecule, effective adsorption and filling in porous carbon materials can only occur within pore structures within a specific pore size range. That is, the higher the proportion of the pore volume within this specific pore size range in the total pore volume of the porous carbon material, the more likely silane gas molecules can be adsorbed within these pore structures and undergo thermal decomposition to deposit and form nano-silicon. Furthermore, through theoretical calculations and experiments, the inventors discovered that the pore size range of porous carbon materials also has a significant impact on the electrochemical activity of nano-silicon.

[0006] Based on this, the inventors of this invention, through in-depth research, discovered that by employing a dual activation method involving the addition of both organic and inorganic activators to prepare porous carbon materials, the pore volume ratio of effective micro-mesopores with pore sizes ranging from 0.35 to 10 nm can be significantly increased. This allows for the effective improvement of silicon deposition and electrochemical activity when using this porous carbon material as a precursor to prepare silicon-carbon anode materials, thereby enhancing the reversible specific capacity and charge-discharge efficiency of the silicon-carbon anode materials. Based on this, this invention was completed.

[0007] Specifically, the porous carbon material has an effective micro-mesoporous structure; the effective micro-mesoporous pore volume ratio in the porous carbon material is more than 90%; the effective micro-mesoporous pores include mesoporous structures and microporous structures, and the pore size of the effective micro-mesoporous pores is 0.35 to 10 nm.

[0008] In a preferred embodiment, the porous carbon material has a specific surface area ≥1700 m². 2 / g, pore volume ≥0.8cm³ 3 / g.

[0009] In a preferred embodiment, the surface of the porous carbon material has a volcanic rock-like morphology.

[0010] In a preferred embodiment, the volcanic rock-like morphology includes mesoporous structures and contains a plurality of micropores within the mesoporous pores.

[0011] In a preferred embodiment, the pore size of the micropores is 0.35–2 nm, and the pore volume ratio is 67–75%.

[0012] In a preferred embodiment, the pore size of the mesopore is 2-10 nm, and the pore volume ratio is 20-30%.

[0013] The second objective of this invention is to provide a method for preparing the aforementioned porous carbon material that facilitates silicon deposition, the method comprising the following steps:

[0014] S1. The carbon source material is subjected to a first activation treatment in the presence of an organic activator to obtain a primary activation product;

[0015] S2. Carbonize the activated material to obtain carbonized products;

[0016] S3. The carbonization product is subjected to a second activation treatment in the presence of an inorganic activator to obtain a porous carbon material with an effective micro-mesoporous structure.

[0017] In a preferred embodiment, the mass ratio of the carbon source material to the organic activator is 100:(3-5).

[0018] In a preferred embodiment, the mass ratio of the carbonization product to the inorganic activator is 100:(100-300).

[0019] In a preferred embodiment, the conditions for the first activation treatment include a temperature of 100–150°C and a reaction time of 1–2 h.

[0020] In a preferred embodiment, the carbonization treatment conditions include a temperature of 500–600°C and a reaction time of 1–2 hours.

[0021] In a preferred embodiment, the conditions for the second activation treatment include a temperature of 700–900°C and a reaction time of 2–5 h.

[0022] In a preferred embodiment, the carbon source material is a resin-based polymer material that exists in liquid form under normal temperature and pressure conditions.

[0023] In a preferred embodiment, the resin-based polymer material is selected from at least one of phenolic resin, epoxy resin, and urea-formaldehyde resin.

[0024] In a preferred embodiment, the organic activator is a mixture of a low-boiling-point organic solvent and an acidic solvent.

[0025] In a preferred embodiment, the mass ratio of the low-boiling-point organic solvent to the acidic solvent is 1:(0.3 to 0.5).

[0026] In a preferred embodiment, the boiling point of the low-boiling organic solvent is 90–100°C.

[0027] In a preferred embodiment, the low-boiling-point organic solvent is selected from at least one of petroleum ether, dichloromethane, and chloroform.

[0028] In a preferred embodiment, the acidic solvent is selected from at least one of hydrochloric acid, phosphoric acid, sulfuric acid, and oxalic acid.

[0029] In a preferred embodiment, the inorganic activator is selected from at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, and ammonium hydroxide.

[0030] In a preferred embodiment, the method for preparing porous carbon materials that facilitate silicon deposition provided by the present invention further includes washing, drying, crushing and sieving the product obtained from the second activation treatment.

[0031] The third objective of this invention is to provide a silicon-carbon anode material, which is obtained by combining the above-mentioned porous carbon material with silicon material.

[0032] The fourth objective of this invention is to provide a method for preparing a silicon-carbon anode material, which includes: using the above-mentioned porous carbon material as a precursor, performing vapor-phase pyrolysis deposition of silane gas on the porous carbon material to generate nano-silicon, thereby obtaining the silicon-carbon anode material.

[0033] The fifth objective of this invention is to provide the application of the aforementioned porous carbon materials and / or silicon-carbon anode materials that facilitate silicon deposition in lithium-ion batteries.

[0034] The key to this invention lies in the use of a dual activation method involving the addition of both organic and inorganic activators to prepare porous carbon materials. This significantly increases the pore volume ratio of effective micro-mesopores with pore sizes ranging from 0.35 to 10 nm, achieving an effective micro-mesopore structure ratio of over 90%. This results in silicon-carbon anode materials prepared using this porous carbon material as a precursor through silane gas vapor-phase pyrolysis deposition to generate nano-silicon, exhibiting high reversible specific capacity and high charge-discharge efficiency. The dual-activation porous carbon preparation method provided by this invention first activates and carbonizes the carbonized product with an organic activator to obtain a carbonized product with a high specific surface area. Then, a secondary activation is performed by adding an inorganic activator to create micropores in the carbonized product. This allows for precise control of the pore structure of the porous carbon material, resulting in porous carbon materials with a high effective micro-mesopore volume ratio (≥90%). Because this porous carbon material has a high effective micro-mesopore volume ratio, it can adsorb silane gas molecules into the effective micro-mesopores to the maximum extent and cause them to decompose and deposit under heat to form nano-silicon, increasing the amount of silicon deposition. At the same time, the effective micro-mesopore structure can provide a certain space for nano-silicon to meet the volume expansion of nano-silicon during the electrochemical lithium storage process, that is, improve the electrochemical activity of nano-silicon. This improves the reversible specific capacity and charge-discharge efficiency of silicon-carbon anode materials, enabling lithium-ion batteries to have higher energy density. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the porous carbon material provided by the present invention.

[0036] Figure 2 This is a SEM image of the porous carbon material prepared in Example 1.

[0037] Figure 3 This is the adsorption-desorption isotherm diagram of the porous carbon material prepared in Example 1. Detailed Implementation

[0038] The porous carbon material for silicon deposition provided by this invention has an effective micro-mesoporous structure; the effective micro-mesoporous volume of the porous carbon material accounts for 90% or more, such as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100% or any value between them; the effective micro-mesoporous structure includes mesoporous structure and microporous structure and the pore size of the effective micro-mesoporous structure is 0.35 to 10 nm, such as 0.35 nm, 0.5 nm, 0.8 nm, 1 nm, 1.2 nm, 1.5 nm, 1.8 nm, 2 nm, 5 nm, 8 nm, 10 nm or any value between them.

[0039] In this invention, the term "effective micropore" refers to a pore structure with a pore size of 0.35–10 nm. Within this pore structure range, gaseous silane molecules can be effectively adsorbed and deposited to form electrochemically active nano-silicon. When the size of the effective micropore is less than 0.35 nm, the nano-silicon deposited in the pores does not have enough space to accommodate its volume expansion during the electrochemical lithium storage process; that is, the nano-silicon at this time does not possess electrochemical activity or has weak electrochemical activity. When the size of the effective micropore is greater than 10 nm, gaseous silane molecules are not easily adsorbed and retained in the pores, but rather more easily pass directly through the pores, which is not conducive to increasing the silicon deposition rate.

[0040] In this invention, the specific surface area of ​​the porous carbon material is preferably greater than or equal to 1700 m². 2 / g, which can be 1700m 2 / g、1800m 2 / g、1900m 2 / g、2000m 2 / g, etc.; pore volume preferably greater than or equal to 0.8cm³. 3 / g, for example. This is more conducive to silane gas molecules entering the effective micropores of porous carbon materials and depositing to form nano-silicon.

[0041] In this invention, the surface of the porous carbon material particles preferably has a volcanic rock-like morphology. The surface morphology of the porous carbon material particles can be obtained by scanning electron microscopy (SEM). SEM allows direct observation of the mesoporous structure on the surface of the porous carbon material particles, and micropore testing reveals that the porous carbon material possesses both micropores and mesopores. This indicates that the porous carbon material provided by this invention has a composite pore structure of micropores and mesopores.

[0042] In this invention, the volcanic rock-like morphology includes mesopores, with a plurality of micropores composited within the mesopore pores. Through micropore structure testing, the pore volume ratios of mesopores and micropores, as well as the total pore volume ratio, are obtained using different calculation models. The sum of the pore volumes of micropores and mesopores is greater than the total pore volume, proving that this composite structure (mesopore pores with a plurality of micropores composited within them) exists in the porous carbon material. The preferred pore size of the micropores is 0.35–2 nm, such as 0.35 nm, 0.5 nm, 0.8 nm, 1 nm, 1.2 nm, 1.5 nm, 1.8 nm, 2 nm, or any value between them; the preferred pore volume ratio is 67–75%, such as 67%, 69%, 70%, 72%, 74%, 75%, or any value between them. The pore size of the mesopore is preferably 2 to 10 nm, such as 2 nm, 5 nm, 8 nm, 10 nm or any value between them; the pore volume ratio is preferably 20 to 30%, such as 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% or any value between them.

[0043] It should be noted that the calculation method for the effective micro-mesopore pore volume ratio is based on the Barrett-Joyner-Halenda (BJH) mesopore analysis model (hereinafter referred to as the BJH method) and the t-plot micropore analysis model (hereinafter referred to as the t-plot method) in adsorption theory. In this invention, the BJH method is used as the calculation model for the pore size distribution of mesopores (2-50 nm) and macropores (50-196 nm), and the t-plot method is used as the calculation model for the pore size distribution of micropores (0.35-2 nm). Therefore, the proportion ω of the effective micro-mesopore pore volume in the total pore volume can be calculated using the following formula:

[0044]

[0045] Where ω is the percentage of the effective micro-mesopore volume to the total pore volume, b is the intercept of the vt plot of adsorption in the t-plot model, and 0.0015468*b is the pore volume of the micropore portion in the effective micro-mesopores. This refers to the pore volume of the small mesopore portion (pore size 2–10 nm) within the effective micro-mesopore system. The pore volume of mesopores (pore size of 2-50 nm) The pore volume is for large pores (pore size greater than 50 nm).

[0046] In this invention, the method for preparing the porous carbon material favorable for silicon deposition includes the following steps: S1. Performing a first activation treatment on the carbon source material in the presence of an organic activator to obtain a primary activation product; S2. Performing a carbonization treatment on the primary activated material to obtain a carbonized product; S3. Performing a second activation treatment on the carbonized product in the presence of an inorganic activator; and optionally, S4. Washing, drying, crushing, and sieving the product obtained from the second activation treatment to obtain the porous carbon material. In step S3, the carbonized product and the inorganic activator can be mixed by grinding, or the carbonized product can be immersed in a solution containing the inorganic activator, or other methods can be used to obtain a mixture before performing the second activation treatment. In step S4, the purpose of washing is mainly to remove the inorganic activator remaining from the second activation treatment.

[0047] In one specific embodiment, the method for preparing the porous carbon can be as follows: S1'. Mixing the carbon source material with an organic activator, stirring at 200-500 rpm for 3-5 minutes to obtain a homogeneous mixture, and then subjecting the mixture to a first activation treatment to obtain a primary activation product; S2'. Crushing the primary activation product obtained in step S1', and then carbonizing it to obtain a carbonized product; S3'. Mixing the carbonized product obtained in step S2' with an inorganic activator by grinding or other methods until homogeneous, and then subjecting it to a second activation treatment under an inert atmosphere to obtain a secondary activation product; S4'. Then, after acid washing, water washing, crushing, and sieving, the porous carbon material is obtained. The acid concentration used for acid washing is 0.5-1.5 mol / L, such as 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, or any value between them.

[0048] In this invention, the conditions for the first activation treatment include a temperature preferably of 100–150°C, such as 100°C, 120°C, 130°C, 140°C, 150°C, or any value between them; and a reaction time preferably of 1–2 hours, such as 1 hour, 1.2 hours, 1.5 hours, 1.8 hours, 2 hours, or any value between them. The conditions for the carbonization treatment include a temperature preferably of 500–600°C, such as 500°C, 520°C, 550°C, 580°C, 600°C, or any value between them; and a reaction time preferably of 1–2 hours, such as 1 hour, 1.2 hours, 1.5 hours, 1.8 hours, 2 hours, or any value between them. The conditions for the second activation treatment include a temperature preferably of 700–900°C, such as 700°C, 750°C, 800°C, 850°C, 900°C or any value between them; and a reaction time preferably of 2–5 h, such as 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h or any value between them.

[0049] In this invention, the preferred mass ratio of the carbon source material to the organic activator is 100:(3-5). That is, based on 100 parts by weight of the carbon source material, the preferred mass of the organic activator is 3-5 parts by weight, such as 3, 3.5, 4, 4.5, 5 parts by weight, or any value between them. Controlling the mass ratio of the carbon source material to the organic activator within the above-mentioned preferred range is more conducive to forming a carbonized product with a large specific surface area after primary activation. If the amount of organic activator added is too small or too large, it is not conducive to the subsequent formation of porous carbon materials with a high effective micro-mesopore volume ratio and a suitable micropore and mesopore volume ratio.

[0050] The preferred mass ratio of the carbonized product to the inorganic activator is 100:(100-300). This ratio is more conducive to secondary pore formation of the carbonized product, increasing the effective micro-mesopore volume ratio (above 90%). Specifically, based on 100 parts by weight of the carbonized product, the preferred mass of the inorganic activator is 100-300 parts by weight, such as 100, 150, 200, 250, 300 parts by weight, or any value between them.

[0051] In this invention, the carbon source material is preferably a resin-based polymer material existing in liquid form under normal temperature and pressure conditions. The resin-based polymer material is preferably selected from at least one of phenolic resin, epoxy resin, and urea-formaldehyde resin. On the one hand, the liquid form makes it easier to mix the carbon source material evenly with the inorganic activator, which is more conducive to the activation reaction. On the other hand, the resin-based polymer material has a more stable structure and higher strength, which is more conducive to obtaining porous carbon materials with high batch-to-batch consistency and stable structure, and has greater prospects for industrial production applications.

[0052] In this invention, the organic activator is preferably a mixture of a low-boiling-point organic solvent and an acidic solvent. The organic activator serves to initially create pores, which is beneficial for further pore creation during subsequent inorganic activation, promoting the formation of effective micropores and mesopores. The mass ratio of the low-boiling-point organic solvent to the acidic solvent is preferably 1:(0.3-0.5), such as 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, or any value between them. By controlling the mass ratio of the low-boiling-point organic solvent to the acidic solvent within the above-mentioned preferred range, the organic activator can better perform initial pore creation on the carbon source material, thereby initially obtaining a carbonized product with a higher specific surface area. This is more conducive to further pore creation using the inorganic activator, increasing the effective micropore and mesopore volume ratio, and enabling the micropore volume ratio to reach 67-75% and the mesopore volume ratio to reach 20-30%.

[0053] The present invention will be described in detail below through specific embodiments.

[0054] In the following examples and comparative examples, all parts refer to parts by weight.

[0055] Example 1

[0056] S1. Add 4 parts of a mixture of petroleum ether and concentrated hydrochloric acid (mass ratio of petroleum ether to concentrated hydrochloric acid is 1:0.3) to 100 parts of phenolic resin, stir at 300 rpm for 4 min until the liquid is slightly heated, transfer the well mixed liquid to a container preheated at 120℃, and place it in a box furnace at 120℃ for activation treatment for 1 h to obtain the primary activation product A1.

[0057] S2. Transfer the primary activation product A1 from step S1 to a wall-breaking machine and crush for 20 minutes. Then transfer it to a box furnace and carbonize it at 500°C for 1 hour to obtain carbonized product B1.

[0058] S3. Take 100g of carbonized product B1 and grind and mix with 300g of flake potassium hydroxide. Then transfer the mixture to a tube furnace and purge with nitrogen to maintain an inert gas atmosphere. Heat the tube furnace to 800℃ at a rate of 5℃ / min, hold for 2h, and cool to room temperature to obtain secondary activation product C1.

[0059] S4. The secondary activation product C1 is soaked in 1 mol / L hydrochloric acid solution, filtered, and washed with a large amount of water until the pH of the filtrate is neutral. After drying, it is crushed and sieved to obtain porous carbon material.

[0060] Example 2

[0061] S1. Add 4 parts of a mixture of petroleum ether and concentrated hydrochloric acid (mass ratio of petroleum ether to concentrated hydrochloric acid is 1:0.5) to 100 parts of phenolic resin, stir at 300 rpm for 4 min until the liquid is slightly heated, transfer the well mixed liquid to a container preheated at 120°C, and place it in a box furnace at 120°C for activation treatment for 1 h to obtain the primary activation product A2.

[0062] S2. Transfer the primary activation product A2 from step S1 to a wall-breaking machine and crush for 20 minutes. Then transfer it to a box furnace and carbonize it at 500°C for 1 hour to obtain carbonized product B2.

[0063] S3. Take 100g of carbonized product B2 and grind and mix it with 300g of flake potassium hydroxide. Then transfer the mixture to a tube furnace and purge it with nitrogen to maintain an inert gas atmosphere. Heat the tube furnace to 900℃ at a rate of 5℃ / min, hold it at that temperature for 2h, and cool it to room temperature to obtain the secondary activation product C2.

[0064] S4. The secondary activation product C2 is soaked in 1 mol / L hydrochloric acid solution, filtered, and washed with a large amount of water until the pH of the filtrate is neutral. After drying, it is crushed and sieved to obtain porous carbon material.

[0065] Example 3

[0066] S1. Add 3 parts of a mixture of petroleum ether and sulfuric acid (mass ratio of petroleum ether to concentrated hydrochloric acid is 1:0.3) to 100 parts of epoxy resin, stir at 300 rpm for 3 min until the liquid is slightly heated, transfer the well mixed liquid to a container preheated to 100℃, place it in a box furnace at 100℃ for activation treatment for 2 h, and obtain the primary activation product A3.

[0067] S2. Transfer the primary activation product A3 from step S1 to a wall-breaking machine and crush for 20 minutes. Then transfer it to a box furnace and carbonize it at 500°C for 2 hours to obtain carbonized product B3.

[0068] S3. Take 100g of carbonized product B3 and 100g of flake sodium hydroxide, grind and mix them, then transfer the mixture to a tube furnace, and purge with nitrogen to maintain an inert gas atmosphere. Heat the tube furnace to 900℃ at a rate of 5℃ / min, hold for 3.5h, and cool to room temperature to obtain secondary activation product C3.

[0069] S4. The secondary activation product C3 is soaked in 1 mol / L hydrochloric acid solution, filtered, and washed with a large amount of water until the pH of the filtrate is neutral. After drying, it is crushed and sieved to obtain porous carbon material.

[0070] Example 4

[0071] S1. Add 5 parts of a mixture of petroleum ether and phosphoric acid (mass ratio of petroleum ether to concentrated hydrochloric acid is 1:0.3) to 100 parts of urea-formaldehyde resin, stir at 300 rpm for 5 min until the liquid is slightly heated, transfer the well mixed liquid to a container preheated at 150°C, and place it in a box furnace at 150°C for activation treatment for 1 h to obtain the primary activation product A4.

[0072] S2. Transfer the primary activation product A4 from step S1 to a wall-breaking machine and crush for 20 minutes. Then transfer it to a box furnace and carbonize it at 600°C for 1 hour to obtain carbonized product B4.

[0073] S3. Take 100g of carbonized product B4 and 200g of flake ammonium hydroxide, grind and mix them, then transfer the mixture to a tube furnace, and purge with nitrogen to maintain an inert gas atmosphere. Heat the tube furnace to 700℃ at a rate of 5℃ / min, hold for 5h, and cool to room temperature to obtain secondary activated product C4.

[0074] S4. The secondary activation product C4 is soaked in 1 mol / L hydrochloric acid solution, filtered, and washed with a large amount of water until the pH of the filtrate is neutral. After drying, it is crushed and sieved to obtain porous carbon material.

[0075] Example 5

[0076] Porous carbon materials were prepared according to the method of Example 1, except that in step S1, the mass ratio of petroleum ether to concentrated hydrochloric acid in the mixture was 1:0.1, and the other conditions were the same as in Example 1, thus obtaining porous carbon materials.

[0077] Example 6

[0078] Porous carbon materials were prepared according to the method of Example 1, except that in step S1, the mass ratio of petroleum ether to concentrated hydrochloric acid in the mixture was 1:0.7, and the other conditions were the same as in Example 1, thus obtaining porous carbon materials.

[0079] Example 7

[0080] Porous carbon materials were prepared according to the method of Example 1, except that in step S1, the amount of the mixture of petroleum ether and concentrated hydrochloric acid was 1 part, and the other conditions were the same as in Example 1, and porous carbon materials were obtained.

[0081] Example 8

[0082] Porous carbon materials were prepared according to the method of Example 1, except that in step S1, the amount of the mixture of petroleum ether and concentrated hydrochloric acid used was 7 parts, and the other conditions were the same as in Example 1, and porous carbon materials were obtained.

[0083] Comparative Example 1

[0084] Porous carbon materials were prepared according to the method in Example 1, except that 80g of flake potassium hydroxide was used instead of 300g of flake potassium hydroxide, while all other conditions remained the same, and a reference porous carbon material was prepared.

[0085] Comparative Example 2

[0086] Porous carbon materials were prepared according to the method in Example 1, except that 400g of flake potassium hydroxide was used instead of 300g of flake potassium hydroxide, while all other conditions remained the same, and a reference porous carbon material was prepared.

[0087] Comparative Example 3

[0088] S1. Add 4 parts of a mixture of petroleum ether and concentrated hydrochloric acid to 100 parts of phenolic resin, stir at 300 rpm for 4 minutes until the liquid is slightly heated, transfer the well mixed liquid to a container preheated at 120°C, and place it in a box furnace at 120°C for activation treatment for 1 hour to obtain the primary activation product DA3.

[0089] S2. Transfer the primary activation product DA3 from step S1 to a wall-breaking machine and crush for 20 minutes. Then transfer it to a box furnace and carbonize it at 500°C for 1 hour to obtain the carbonized product DB3.

[0090] S3. The carbonization product DB2 is soaked in a 1 mol / L hydrochloric acid solution, filtered, and washed with a large amount of water until the pH of the filtrate is neutral. After drying, it is crushed and sieved to obtain the reference porous carbon material.

[0091] Comparative Example 4

[0092] S1. 100 parts of phenolic resin were directly heated, cured and crushed, and then transferred to a box furnace for carbonization at 500°C for 1 hour to obtain carbonized product DB4.

[0093] S2. Take 100g of carbonized product DB3 and 300g of flake potassium hydroxide, grind and mix them, then transfer the mixture to a tube furnace, and purge with nitrogen to maintain an inert gas atmosphere. Heat the tube furnace to 800℃ at a rate of 5℃ / min, hold for 2h, and cool to room temperature to obtain the secondary activation product DC4.

[0094] S3. The secondary activation product DC3 was soaked in 1 mol / L hydrochloric acid solution, filtered, and washed with a large amount of water until the pH of the filtrate was neutral. After drying, it was crushed and sieved to obtain the reference porous carbon material.

[0095] Comparative Example 5

[0096] Commercially available resin-based porous carbon.

[0097] Comparative Example 6

[0098] Commercially available coal-based porous carbon.

[0099] Test case

[0100] The porous carbon materials prepared in the above examples and comparative examples were tested for pore structure, silicon deposition content, charge-discharge efficiency, and reversible specific capacity using the following methods. The results are shown in Tables 1 and 2.

[0101] (1) Pore structure performance test of porous carbon materials: Using a specific surface area and pore size analyzer, based on the nitrogen adsorption method, the pore size distribution is determined by measuring the adsorption and desorption curves. The specific surface area, total pore volume, micropore volume and its proportion, and mesopore volume and its proportion of porous carbon materials are calculated by using the BET equation, BJH method and t-plot method. The effective micro- and mesopore volume proportion that is conducive to silicon deposition is obtained by summing the micropore volume and the mesopore volume.

[0102] (2) Silicon deposition content: Using porous carbon material as a precursor, silicon-carbon anode material is obtained through the same vapor deposition process. The content of C, Si, N and H elements in silicon-carbon anode material is obtained by elemental analysis. Assuming that the material contains C, Si, N and H elements, the deposition silicon content (%) = 100% - C% - N% - H.

[0103] (3) Charge-discharge efficiency and reversible specific capacity: The button cell prepared with the silicon-carbon anode material obtained in (2) was tested. The specific steps are as follows:

[0104] 3-1. Material weighing: Weigh 0.96g of silicon-carbon anode active material, and weigh the corresponding proportion of slurry material according to the slurry mixing ratio of active material: SBR: CMC: SP = 80:5:5:10. Mix with deionized water to obtain a slurry with a solid content of 25% of silicon-carbon anode active material and put it into a degassing tank.

[0105] 3-2. Mixing: Degas the above slurry 4 times in a degassing machine. The degassing mode for each time is: degas at 850 rpm for 1 min and then degas at 2000 rpm for 12 min to obtain a uniformly mixed slurry.

[0106] 3-3. Coating: The above-mentioned uniformly mixed slurry is coated on an 8μm double-sided copper foil using a 75μm doctor blade, and the coating machine speed is fixed.

[0107] 3-4. Electrode drying and cutting: Place the coated electrode in an 80℃ oven to dry for 2 hours, then place it in a vacuum oven to dry for 12 hours. Cut the dried electrode into pieces, weigh and record the weight.

[0108] 3-5. Battery assembly: Place the dried electrode sheets into the glove box to assemble the battery.

[0109] 3-6. Electrical Performance Testing: The assembled button cell was tested on a battery testing system with a test voltage range of 0.005V-1.5V. It was then discharged at a constant current of 0.1C to 0.01V, followed by a deep discharge at a constant current of 0.01C to 0.005V. The discharge capacity was divided by the mass of the active material (silicon-carbon anode material) to obtain the specific discharge capacity of the anode material. The cell was then charged at a constant current of 0.1C to 1.5V. The charging capacity was divided by the mass of the active material (silicon-carbon anode material) to obtain the specific charging capacity (reversible specific capacity) of the anode material. The percentage of the specific discharge capacity to the specific charging capacity is the charge / discharge efficiency.

[0110] Table 1

[0111]

[0112]

[0113] Table 2

[0114] project Charge / discharge efficiency (%) Reversible capacity (mAh / g) Example 1 91.69 2354.17 Example 2 90.54 1839.84 Example 3 90.01 1885.50 Example 4 90.23 2046.42 Example 5 89.98 1803.48 Example 6 89.87 1815.92 Example 7 89.62 1793.84 Example 8 89.70 1790.42 Comparative Example 1 80.24 1503.41 Comparative Example 2 79.15 1428.16 Comparative Example 3 71.63 1208.43 Comparative Example 4 75.14 1349.71 Comparative Example 5 89.42 1782.35 Comparative Example 6 89.01 1750.38

[0115] By comparing Example 1 with Comparative Examples 1 and 2, it can be found that when the amount of inorganic activator is not properly selected, the specific surface area, total pore volume, effective micro-mesopore pore volume ratio, and deposited silicon content of the porous carbon materials in Comparative Examples 1 and 2 are significantly lower than those of the porous carbon material in Example 1. This indicates that an appropriate amount of inorganic activator can promote the formation of effective micro-mesopores with a high pore volume ratio in porous carbon materials.

[0116] A comparison of Example 1 with Comparative Examples 3 and 4 reveals that the porous carbon material without the second inorganic activation treatment (Comparative Example 3) and the porous carbon material without the first organic activation treatment (Comparative Example 4) have lower specific surface area, total pore volume, effective micro-mesopore volume ratio, and deposited silicon content than the porous carbon material in Example 1. This indicates that both the first organic activation treatment and the second inorganic activation treatment are indispensable: firstly, relying solely on either the first organic activation treatment or the second inorganic activation treatment results in a lower specific surface area and total pore volume, insufficient to form enough effective micro-mesopores; secondly, the first organic activation treatment facilitates the formation of micropores and their evolution into mesopores during the second inorganic activation treatment. In other words, the synergistic effect of dual activation treatments promotes the formation of effective micro-mesopores, thereby constructing a composite micro-mesoporous structure with a more developed pore structure than traditional porous carbon.

[0117] By comparing Examples 1-8 with Comparative Examples 5 and 6, it can be found that the specific surface area, total pore volume, and effective micro-mesopore volume ratio of the porous carbon materials obtained in Examples 1-8 can reach the same level as existing commercial porous carbon materials or even slightly better than existing commercial materials. The charge-discharge efficiency and reversible specific capacity of the silicon-carbon anode materials prepared with the porous carbon materials of Examples 1-8 are also at the same level as the prior art.

[0118] As can be seen from the results in Tables 1 and 2, compared with the porous carbon materials of Comparative Examples 1-6, the porous carbon materials provided in Examples 1-8 of this invention possess a mesoporous-microporous composite structure, exhibiting a higher specific surface area and total pore volume. The effective micro-mesopore pore volume ratio can reach over 90%, and the deposited silicon content is greater than 52.92%. Furthermore, the silicon-carbon anode material prepared using the porous carbon material provided by this invention achieves a charge-discharge efficiency of over 89.62% and a reversible specific capacity of over 1790 mAh / g. This indicates that the porous carbon material provided by this invention possesses a high effective micro-mesopore pore volume ratio and a composite pore structure conducive to silicon deposition, thereby improving the deposited silicon content, reversible specific capacity, and charge-discharge efficiency of the silicon-carbon anode material.

[0119] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for preparing porous carbon materials that facilitate silicon deposition, characterized in that, The porous carbon material has an effective micro-mesoporous structure; the effective micro-mesoporous volume accounts for more than 90% of the porous carbon material; the effective micro-mesoporous structure includes mesoporous structure and microporous structure, and the pore size of the effective micro-mesoporous structure is 0.35~10nm; the preparation method of the porous carbon material includes the following steps: S1. Performing a first activation treatment on the carbon source material in the presence of an organic activator to obtain a primary activation product; S2. Performing a carbonization treatment on the primary activation material to obtain a carbonization product; S3. Performing a second activation treatment on the carbonization product in the presence of an inorganic activator to obtain a porous carbon material with an effective micro-mesoporous structure; the organic activator is a mixture of a low-boiling-point organic solvent and an acidic solvent.

2. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The specific surface area of ​​the porous carbon material is ≥1700 m². 2 / g, pore volume ≥0.8cm³ 3 / g.

3. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The surface of the porous carbon material has a volcanic rock-like morphology.

4. The method for preparing porous carbon materials favorable for silicon deposition according to claim 3, characterized in that, The volcanic rock-like morphology includes mesopores, and several micropores are combined within the mesopore pores.

5. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The pore size of the micropores is 0.35~2nm, and the pore volume ratio is 67~75%.

6. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The mesopores have a pore size of 2~10nm and a pore volume ratio of 20~30%.

7. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The mass ratio of the carbon source material to the organic activator is 100:(3~5).

8. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The mass ratio of the carbonization product to the inorganic activator is 100:(100~300).

9. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The conditions for the first activation treatment include a temperature of 100~150℃ and a reaction time of 1~2h.

10. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The carbonization treatment conditions include a temperature of 500~600℃ and a reaction time of 1~2h.

11. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The conditions for the second activation treatment include a temperature of 700~900℃ and a reaction time of 2~5h.

12. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The carbon source material is a resin-based polymer material that exists in liquid form under normal temperature and pressure conditions.

13. The method for preparing porous carbon materials favorable for silicon deposition according to claim 12, characterized in that, The resin-based polymer material is selected from at least one of phenolic resin, epoxy resin, and urea-formaldehyde resin.

14. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The mass ratio of the low-boiling-point organic solvent to the acidic solvent is 1:(0.3~0.5).

15. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The boiling point of the low-boiling-point organic solvent is 90~100℃.

16. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The low-boiling-point organic solvent is selected from at least one of petroleum ether, dichloromethane, and chloroform.

17. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The acidic solvent is selected from at least one of hydrochloric acid, phosphoric acid, sulfuric acid, and oxalic acid.

18. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The inorganic activator is selected from at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, and ammonium hydroxide.

19. The method for preparing porous carbon materials favorable for silicon deposition according to claim 1, characterized in that, The method also includes washing, drying, crushing and sieving the product obtained from the second activation treatment.

20. A porous carbon material favorable for silicon deposition prepared by the method according to any one of claims 1 to 19.

21. A silicon-carbon anode material, characterized in that, The silicon-carbon anode material is obtained by combining the porous carbon material and silicon material as described in claim 20.

22. A method for preparing a silicon-carbon anode material, characterized in that, The preparation method includes: using the porous carbon material described in claim 20 as a precursor, and generating nano-silicon by vapor-phase pyrolysis deposition of silane gas on the porous carbon material, thereby obtaining a silicon-carbon anode material.

23. The application of the porous carbon material for silicon deposition as described in claim 20 and / or the silicon-carbon anode material as described in claim 21 in lithium-ion batteries.

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