Bio-based silicon-carbon negative electrode porous carbon material, preparation method and application of bio-based silicon-carbon negative electrode porous carbon material

Abstract

The invention relates to a bio-based silicon-carbon negative electrode porous carbon material as well as a preparation method and application thereof, and belongs to the technical field of carbon material preparation. The method comprises the following steps: by taking forestry and agricultural residues as a bio-based raw material, carrying out pre-carbonization, crushing and other treatments to obtain a bio-based raw material A, then adding a dopant, mixing to polymerize a pyrrole monomer, carrying out surface modification on the bio-based raw material A, and mixing with polypyrrole and the like to obtain a precursor compound C; then carrying out primary activation and secondary activation treatment; and then carrying out acid pickling, drying, grinding and staged passivation to obtain the bio-based silicon-carbon negative electrode porous carbon material. The material surface area is greater than or equal to 2000m < 2 > / g, the micropore proportion is greater than or equal to 82%, the total pore volume is greater than or equal to 1cc / g, the oxygen content is less than or equal to 1.5%, and the The bio-based porous carbon material for the silicon-carbon negative electrode can be applied to a silicon-carbon composite negative electrode of a lithium battery, and can be used as a framework to load nano silicon particles through a chemical vapor deposition method, so that a silicon-carbon composite negative electrode material with good performance can be formed, and a new choice is provided for the development of the negative electrode material of the lithium battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of carbon material preparation, and relates to a bio-based silicon-carbon negative electrode porous carbon material, a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of new energy automobile and portable electronic equipment industry, the market demand for high energy density lithium batteries is increasingly urgent. The theoretical specific capacity of traditional graphite negative electrode is only 372 mAh / g, which is difficult to meet the demand of new generation high power equipment. Silicon-based materials are considered as ideal substitutes due to their high theoretical specific capacity of 4200 mAh / g, but they have a volume expansion of up to 300% during charging and discharging, which leads to electrode pulverization, continuous rupture and regeneration of SEI film, and causes rapid capacity decay. Although the existing technology can alleviate the expansion by nano-silicon particles or core-shell structure, it has problems such as complex process and high cost. Biomass porous carbon is concerned due to its natural abundant pore structure and low cost characteristics, but traditional biomass carbon has defects such as insufficient specific surface area and uncontrollable pore structure. The present application prepares a bio-based silicon-carbon negative electrode porous carbon material with high surface area and high micropore ratio through pre-carbonization of agricultural and forestry waste, polypyrrole doping and two-stage activation process. The three-dimensional interconnected pores can effectively buffer the volume change of silicon, and the low oxygen content surface reduces the electrolyte side reaction. The material as a silicon-carbon composite negative electrode framework can significantly improve the cycle stability of the battery, and provides a new solution for the development of high energy density lithium batteries. SUMMARY

[0003] The present application aims to provide a bio-based silicon-carbon negative electrode porous carbon material, a preparation method and application thereof, which has the characteristics of high specific surface area and high micropore ratio.

[0004] The purpose of the present application can be achieved by the following technical solutions:

[0005] A preparation method of a bio-based silicon-carbon negative electrode porous carbon material, the specific steps of the preparation method are as follows,

[0006] S1: precursor pretreatment

[0007] Select agricultural and forestry waste as bio-based raw material, pre-carbonize at 300-600 DEG C for 1-4h, crush the pre-carbonized bio-based raw material, wash and dry to obtain bio-based raw material A, the particle size of bio-based raw material A is 4-10 mesh;

[0008] S2: adding a dopant

[0009] Dissolve the pyrrole monomer in anhydrous ethanol to obtain a solution with a mass fraction of 5-10%, and then add ammonium persulfate to the solution under a nitrogen atmosphere, with the molar ratio of ammonium persulfate to pyrrole monomer being 1:1; stir the mixed solution at 0-5℃ for 6-12h, filter and wash after the reaction is completed, and dry in a vacuum drying oven at 60-80℃ for 4-6h to obtain the polypyrrole;

[0010] Prepare a solution of silane coupling agent KH-560 and anhydrous ethanol in a volume ratio of 1:(4-5), and then immerse the bio-based raw material A in the silane coupling agent solution and stir at 70℃ for 3h, and then dry to obtain the surface-modified precursor B;

[0011] After the polypyrrole is filtered, washed, and dried, it is mixed and stirred with the surface-modified precursor B, ammonium dihydrogen phosphate, and aluminum oxide, with a stirring speed of 200r / min and a stirring time of 1-2h, to obtain the precursor composite C;

[0012] S3: primary activation treatment

[0013] Under a nitrogen atmosphere, activate the precursor composite C at a temperature of 700℃-900℃ for 1-3h to obtain the primary activated material D, and then crush the primary activated material D to a particle size of 20-50 mesh;

[0014] S4: secondary activation treatment

[0015] Activate the primary activated material D in a protective gas at a temperature of 800℃-1000℃ for 6-10h to obtain the secondary activated material E, with the activation gas temperature being 120-180℃ and the flow rate being 200-500kg / h;

[0016] S5: acid pickling and drying treatment

[0017] Mix the acid pickling agent with the secondary activated material E, and then perform acid pickling at a temperature of 60℃-80℃ for 1-3h; after the acid pickling is completed, wash until the pH is neutral, and then dry at 100℃-200℃ for 1-3h to obtain the solid product F;

[0018] S6: grinding and passivation treatment

[0019] Grind the solid product F by airflow milling to obtain the powder G, and then use a staged passivation method to first heat the powder G to 600-700℃ in a nitrogen atmosphere and maintain the temperature for 1-2h, and then switch to a reducing atmosphere and continue to heat to 800-950℃ for passivation, with the passivation time being 2-4h, to obtain the bio-based silicon-carbon negative electrode porous carbon material.

[0020] Further, the agricultural and forestry waste is one or more of bamboo, coconut shell, corn straw, and fruit shell.

[0021] Further, in S2, the surface modification precursor B is used as a base, the addition amount of ammonium dihydrogen phosphate is 8wt%, and the addition amount of aluminum oxide is 2wt%.

[0022] Further, in S3, the primary activator is water vapor, and the temperature is 120-140 DEG C.

[0023] Further, in S4, the flow rate of the protective gas nitrogen is 5-10 L / min, the secondary activator gas is one or more mixed gases selected from saturated water vapor, superheated water vapor, flue gas and oxygen, and the pressure is 15-30 KPa.

[0024] Further, in S5, the mass ratio of the pickling agent to the secondary activator E is 1:(10-13), the pickling agent is hydrochloric acid, and the concentration is 1-3 mol / L.

[0025] Further, in S6, the reducing atmosphere is H2 / He mixed gas, wherein the volume ratio of H2 to He is 1:9.

[0026] A bio-based silicon-carbon negative electrode porous carbon material, the material has a surface area of greater than or equal to 2000 m 2 / g, a micropore ratio of greater than or equal to 82%, a total pore volume of greater than or equal to 1 cc / g, and an oxygen content of less than or equal to 1.5%.

[0027] An application of a bio-based silicon-carbon negative electrode porous carbon material in a lithium battery silicon-carbon composite negative electrode, wherein the bio-based silicon-carbon negative electrode porous carbon material is used as a skeleton to load nano-silicon particles through a chemical vapor deposition method to form a silicon-carbon composite negative electrode material.

[0028] The bio-based silicon-carbon negative electrode porous carbon material preparation method has the advantages that through multi-stage process cooperative design and parameter optimization, the specific surface area, pore structure and performance of the material can be controlled and adjusted, and the electrochemical performance of the material as a lithium ion battery negative electrode is significantly improved. The core advantages are high specific surface area, high micropore content and adjustable performance, and these characteristics are derived from the systematic innovation of raw material selection, dopant design, activation strategy and passivation process.

[0029] The natural porous structure of the biomass raw material is the basis for constructing a high specific surface area. Agricultural and forestry wastes are rich in cellulose, hemicellulose and lignin, and the three-dimensional network structure thereof is partially decomposed through pyrolysis reaction in a pre-carbonization stage (300-600 DEG C), and the escape of volatile CO2, H2O and small molecular organic matters forms initial pores. The temperature control in this stage is crucial, the depolymerization reaction mainly occurs at <400 DEG C, a large number of micropores are generated, the ring-opening and condensation reactions occur at 400-600 DEG C, the pore wall gradually carbonizes and is shaped, and the pore closure caused by excessive shrinkage is avoided. After pre-carbonization, the raw material is broken to 4-10 mesh particle size, the macroscopic porosity of the raw material is retained, and a uniform reaction interface is provided for subsequent activation through particle size control.

[0030] The twice activation treatment is the key to the specific surface area improvement. The first activation (700-900℃) is carried out under nitrogen protection, the activation gas reacts with the carbon skeleton by oxidation, and the carbon surface is etched by gas-solid reaction, and micropores are preferentially formed at defect sites. The addition of ammonium dihydrogen phosphate further promotes the pore development: the phosphoric acid generated by its decomposition reacts with carbon at high temperature to form phosphate intermediates, which are then decomposed into PO43-and CO, which not only expands the interlayer spacing by intercalation, but also refines the pores by oxidation etching. The incorporation of alumina reduces the activation energy through catalytic effect, making the pore expansion more uniform. The second activation (800-1000℃) is carried out at a higher temperature, in which the coordinated control of activation gas flow (200-500 kg / h) and temperature (120-180℃) achieves the deep expansion of pores, and the high temperature strengthens the kinetic energy of gas molecules, making them more easily penetrate the microporous wall formed by the first activation, and more micropores are formed by continuous etching.

[0031] Micropores (<2 nm) are the main place for lithium ion storage, and their content directly affects the specific capacity of the material. In this invention, the nanoscale pores of the biomass raw material itself are partially preserved during the pre-carbonization stage, forming an initial microporous skeleton; further, the incorporation of polypyrrole provides a template for micropore generation. When polypyrrole is carbonized at high temperature in nitrogen, its conjugated π electron structure forms a strong interaction with the carbon matrix, and the nitrogen-doped sites left after decomposition, such as pyridine nitrogen and graphite nitrogen, not only enhance the electrical conductivity, but also inhibit the excessive graphitization of the carbon layer through steric hindrance effect, preserving a large number of nanoscale pores; the subsequent acid washing process is crucial for optimizing the amount of micropores: the reaction of hydrochloric acid with the residual metal oxides generates soluble salts, which are removed by washing, exposing the covered micropores; at the same time, the mild oxidation of the carbon surface by the acid further etches the surface, increasing the proportion of micropore openings. The airflow mill classification exposes the internal closed micropores by mechanical force, making them participate in the lithium storage reaction. The synergistic effect of these measures significantly increases the proportion of micropores in the material, while ensuring high specific surface area, and optimizing the lithium ion insertion / extraction kinetics.

[0032] The controllability of the material is due to the dual flexibility of process parameters and component design. From the component perspective, by diluting with ethanol, the coupling agent molecules are more easily and uniformly dispersed on the surface of the biomass, and the Si-O-C bond is formed to enhance the interfacial bonding between the carbon matrix and the silicon particles, and to inhibit the volume expansion during the cycle. The addition of ammonium dihydrogen phosphate and alumina balances the activation intensity and structural stability. The catalytic effect of alumina can reduce the activation temperature, realizing the pore regulation under mild conditions.

[0033] In terms of process parameters, the combination of activation temperature and time provides the core means of performance adjustment. The matching of the first activation temperature (700-900℃) and time (1-3h) determines the basic amount of micropores: low-temperature and long-time activation focuses on the stable generation of micropores, and high-temperature and short-time accelerates the expansion of pores but may sacrifice part of the micropores. The linkage adjustment of the second activation temperature (800-1000℃) and gas flow (200-500kg / h) adjusts the micropore ratio: high-flow gas strengthens etching at high temperature to generate more micropores to improve the rate performance; low-flow gas retains more micropores to enhance the capacity. The staged design of passivation treatment (600-700℃ nitrogen preservation and then switching to 800-95℃ reducing atmosphere) further optimizes the material surface properties: the front-stage nitrogen passivation eliminates surface active sites through aromatic ring condensation to reduce electrolyte decomposition; the rear-stage reducing atmosphere promotes sp 2 The formation of hybrid carbon structure improves electronic conductivity.

[0034] The present application realizes the precise control of specific surface area, pore structure and electrochemical performance of porous carbon material through the innovative design of biomass raw material pretreatment, synergistic modification of dopant, staged activation and passivation treatment. BRIEF DESCRIPTION OF DRAWINGS

[0035] For the convenience of those skilled in the art, the present application will be further described below with reference to the accompanying drawings.

[0036] Figure 1 The electron microscope image of the bio-based silicon-carbon negative electrode porous carbon material of Example 1 of the present application;

[0037] Figure 2 The pore volume distribution graph of the bio-based silicon-carbon negative electrode porous carbon material of Example 1 of the present application;

[0038] Figure 3 The isotherm graph of the bio-based silicon-carbon negative electrode porous carbon material of Example 1 of the present application;

[0039] Figure 4 The pore volume distribution graph of the bio-based silicon-carbon negative electrode porous carbon material of Example 2 of the present application;

[0040] Figure 5 The isotherm graph of the bio-based silicon-carbon negative electrode porous carbon material of Example 2 of the present application;

[0041] Figure 6 The pore volume distribution graph of the bio-based silicon-carbon negative electrode porous carbon material of Example 3 of the present application;

[0042] Figure 7 The isotherm graph of the bio-based silicon-carbon negative electrode porous carbon material of Example 3 of the present application. DETAILED DESCRIPTION

[0043] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined object of the present application, the specific embodiments, structures, features and effects thereof according to the present application are described in detail below in combination with the drawings and preferred embodiments.

[0044] Example 1

[0045] S1: precursor pretreatment

[0046] The green coconut shell is selected as a bio-based raw material, and is pre-carbonized at 400 DEG C for 2h. The pre-carbonized bio-based raw material is crushed, washed with water and dried to obtain a bio-based raw material A. The particle size of the bio-based raw material A is 4-10 mesh.

[0047] S2: adding a dopant mixture

[0048] The pyrrole monomer is dissolved in anhydrous ethanol to prepare a solution with a mass fraction of 7%. Under a nitrogen atmosphere, ammonium persulfate is added to the solution, and the molar ratio of ammonium persulfate to pyrrole monomer is 1:1. The mixed solution is stirred at 0 DEG C for 6h. After the reaction is completed, it is filtered and washed, and then dried in a vacuum drying oven at 80 DEG C for 4h to obtain a polypyrrole.

[0049] The silane coupling agent KH-560 is prepared into a solution with anhydrous ethanol in a volume ratio of 1:4. The bio-based raw material A is immersed in the silane coupling agent solution and stirred at 70 DEG C for 3h. After drying, a surface-modified precursor B is obtained.

[0050] After the polypyrrole is filtered, washed and dried, it is mixed and stirred with the surface-modified precursor B, ammonium dihydrogen phosphate and aluminum oxide. The surface-modified precursor B is used as the matrix, the addition amount of ammonium dihydrogen phosphate is 8wt%, the addition amount of aluminum oxide is 2wt%, the stirring speed is 200r / min, and the stirring time is 2h to obtain a precursor composite C.

[0051] S3: primary activation treatment

[0052] Under a nitrogen atmosphere, the precursor composite C is activated at a temperature of 750 DEG C for 1.5h. The primary activation agent is water vapor, and the temperature is 120 DEG C. A primary activated material D is obtained, and is crushed to a particle size of 20-50 mesh.

[0053] S4: secondary activation treatment

[0054] The primary activated material D is activated at a temperature of 900 DEG C for 8h in a protective gas. The flow rate of the protective gas nitrogen is 10L / min. The activation agent is saturated water vapor, the activation gas temperature is 120 DEG C, the flow rate is 350kg / h, and the gas pressure is 20KPa. A secondary activated material E is obtained.

[0055] S5: acid washing and drying treatment

[0056] The pickling agent is mixed with the secondary activation material E to perform pickling, the mass ratio of the pickling agent to the secondary activation material E is 1:10, the pickling agent is hydrochloric acid, the concentration is 3 mol / L, the temperature is 70°C, and the time is 2 h, after the pickling is completed, washing is performed until the pH is neutral, and drying is performed at 150°C for 1 h to obtain a solid product F;

[0057] S6: Grinding and passivation treatment

[0058] The solid product F is classified by using an air flow mill to obtain a powder G, and a staged passivation manner is adopted, the powder G is first heated to 700°C and kept for 1 h in a nitrogen atmosphere, and then the temperature is continuously increased to 950°C in a reducing atmosphere to perform passivation, the reducing atmosphere is H2 / He mixed gas, the volume ratio of H2 to He is 1:9, and the passivation time is 2 h, thereby obtaining the bio-based silicon-carbon negative electrode porous carbon material.

[0059] The bio-based silicon-carbon negative electrode porous carbon material prepared in this embodiment has a specific surface area of 2016 m 2 / g, a pore volume of 1.022 cc / g, a T-Plot micropore ratio of 84.58%, a single-point average pore diameter of 2.02 nm, and an oxygen content of 1.48%.

[0060] Example 2

[0061] S1: Pre-treatment of the precursor

[0062] Raw coconut shells are selected as bio-based raw materials, pre-carbonization is performed at 500°C for 2.5 h, the pre-carbonized bio-based raw materials are crushed, and after washing and drying, a bio-based raw material A is obtained, the particle size of the bio-based raw material A is 4-10 mesh;

[0063] S2: Mixing of the dopant

[0064] Pyrrole monomers are dissolved in anhydrous ethanol to prepare a solution with a mass fraction of 10%, under a nitrogen atmosphere, ammonium persulfate is added to the solution, the amount-of-substance ratio of ammonium persulfate to pyrrole monomers is 1:1, the mixed solution is stirred at 5°C for 6 h, after the reaction is completed, filtration and washing are performed, and drying is performed in a vacuum drying box at 60°C for 6 h, thereby obtaining polypyrrole;

[0065] Silane coupling agent KH-560 is prepared into a solution in a volume ratio of 1:5 with anhydrous ethanol, the bio-based raw material A is immersed in the silane coupling agent solution, stirring is performed at 70°C for 3 h, and after drying, a surface-modified precursor B is obtained;

[0066] After the polypyrrole is filtered, washed, and dried, the polypyrrole is mixed and stirred with the surface-modified precursor B, ammonium dihydrogen phosphate, and aluminum oxide, the surface-modified precursor B is used as a matrix, the addition amount of ammonium dihydrogen phosphate is 8 wt%, the addition amount of aluminum oxide is 2 wt%, the stirring speed is 200 r / min, and the stirring time is 1 h, thereby obtaining a precursor composite C.

[0067] S3: primary activation treatment

[0068] The precursor composite C is activated at a temperature of 850℃ for 2h under a nitrogen atmosphere, a primary activator is flue gas, the temperature is 140℃, to obtain a primary activated material D, and the primary activated material D is crushed to a particle size of 20-50 mesh;

[0069] S4: secondary activation treatment

[0070] The primary activated material D is activated at a temperature of 950℃ for 6h under a protective gas to obtain a secondary activated material E, the flow rate of the protective gas nitrogen is 10L / min, the activator is water vapor, the temperature of the activation gas is 135℃, the flow rate is 300kg / h, and the gas pressure is 25KPa;

[0071] S5: acid washing and drying treatment

[0072] The secondary activated material E is mixed with an acid washing agent, the mass ratio of the acid washing agent to the secondary activated material E is 1:11.5, the acid washing agent is hydrochloric acid with a concentration of 2mol / L, the temperature is 75℃, and the time is 1.5h, after the acid washing is completed, the secondary activated material E is washed to a neutral pH, and then dried at 175℃ for 2h to obtain a solid product F;

[0073] S6: grinding and passivation treatment

[0074] The solid product F is classified by an air flow mill to obtain a powder G, and the powder G is passivated in a staged manner, first heated to 600℃ in a nitrogen atmosphere and kept for 2h, and then switched to a reducing atmosphere to continue heating to 800℃ for passivation, the reducing atmosphere is a H2 / He mixed gas, the volume ratio of H2 to He is 1:9, and the passivation time is 4h, to obtain the bio-based silicon-carbon negative electrode porous carbon material.

[0075] The bio-based silicon-carbon negative electrode porous carbon material prepared in this embodiment has a specific surface area of 2066m 2 / g, a pore volume of 1.046cc / g, a T-Plot micropore ratio of 83.42%, a single-point average pore diameter of 2.02nm, and an oxygen content of 1.3%.

[0076] Example 3

[0077] S1: precursor pretreatment

[0078] Raw coconut shells are selected as bio-based raw materials, and are pre-carbonized at 600℃ for 3h, the pre-carbonized bio-based raw materials are crushed, washed with water and dried to obtain bio-based raw materials A, and the particle size of the bio-based raw materials A is 4-10 mesh;

[0079] S2: adding a dopant and mixing

[0080] The pyrrole monomer is dissolved in anhydrous ethanol to prepare a solution with a mass fraction of 5%, and ammonium persulfate is added to the solution under a nitrogen atmosphere, with a molar ratio of ammonium persulfate to pyrrole monomer of 1:1. The mixed solution is stirred at 0°C for 12 hours, filtered and washed after the reaction is completed, and dried in a vacuum drying box at 80°C for 6 hours to obtain the polypyrrole;

[0081] The silane coupling agent KH-560 is prepared into a solution with anhydrous ethanol at a volume ratio of 1:5, and the bio-based raw material A is immersed in the silane coupling agent solution and stirred at 70°C for 3 hours. After drying, the surface-modified precursor B is obtained.

[0082] After the polypyrrole is filtered, washed and dried, it is mixed and stirred with the surface-modified precursor B, ammonium dihydrogen phosphate and aluminum oxide. The surface-modified precursor B is used as the matrix, the addition amount of ammonium dihydrogen phosphate is 8wt%, the addition amount of aluminum oxide is 2wt%, the stirring speed is 200r / min, and the stirring time is 2h to obtain the precursor composite C.

[0083] S3: One-time activation treatment

[0084] Under a nitrogen atmosphere, the precursor composite C is activated at a temperature of 950°C for 2.5h, and the one-time activation agent is water vapor at a temperature of 140°C to obtain the one-time activated material D, which is crushed to a particle size of 20-50 mesh.

[0085] S4: Secondary activation treatment

[0086] The one-time activated material D is activated at a temperature of 950°C for 6h in a protective gas to obtain the secondary activated material E. The flow rate of the protective gas nitrogen is 10L / min, the activation agent is oxygen, the activation gas temperature is 150°C, the flow rate is 450kg / h, and the gas pressure is 30KPa.

[0087] S5: Acid pickling and drying treatment

[0088] The acid pickling agent is mixed with the secondary activated material E for acid pickling. The mass ratio of the acid pickling agent to the secondary activated material E is 1:13, the acid pickling agent is hydrochloric acid with a concentration of 1mol / L, the temperature is 80°C, and the time is 3h. After acid pickling, the material is washed to neutral pH and dried at 180°C for 2h to obtain the solid product F.

[0089] S6: Grinding and passivation treatment

[0090] The solid product F is classified by air jet milling to obtain the powder G. The powder G is heated to 700°C in a nitrogen atmosphere for 2h, and then switched to a reducing atmosphere of H2 / He mixed gas with a volume ratio of H2 to He of 1:9 for passivation at 950°C for 4h to obtain the bio-based silicon-carbon negative electrode porous carbon material.

[0091] The specific surface area of the bio-based silicon-carbon negative electrode porous carbon material prepared in the embodiment is 2034 m 2 / g, the pore volume is 1.059 cc / g, the T-Plot micropore ratio is 82.12%, the single-point average pore diameter is 2.08 nm, and the oxygen content is 1.15%.

[0092] Comparative Example 1

[0093] In the comparative example, the step of adding a dopant mixture is not performed, and the remaining steps are consistent with those of Example 1.

[0094] The specific surface area of the bio-based silicon-carbon negative electrode porous carbon material prepared in the comparative example is 1200 m 2 / g, the pore volume is 0.650 cc / g, the T-Plot micropore ratio is 75.20%, the single-point average pore diameter is 2.50 nm, and the oxygen content is 2.10%.

[0095] Comparative Example 2

[0096] In the comparative example, the step of performing a first activation treatment is not performed, and the remaining steps are consistent with those of Example 1.

[0097] The specific surface area of the bio-based silicon-carbon negative electrode porous carbon material prepared in the comparative example is 1500 m 2 / g, the pore volume is 0.780 cc / g, the T-Plot micropore ratio is 78.30%, the single-point average pore diameter is 2.30 nm, and the oxygen content is 1.90%.

[0098] Comparative Example 3

[0099] In the comparative example, the step of performing a second activation treatment is not performed, and the remaining steps are consistent with those of Example 1.

[0100] The specific surface area of the bio-based silicon-carbon negative electrode porous carbon material prepared in the comparative example is 1700 m 2 / g, the pore volume is 0.850 cc / g, the T-Plot micropore ratio is 80.10%, the single-point average pore diameter is 2.20 nm, and the oxygen content is 1.75%.

[0101] According to the experimental data, the bio-based silicon-carbon negative electrode porous carbon materials prepared in Examples 1-3 are superior to those prepared in Comparative Examples 1-3 in terms of various performance indicators. Through the complete steps of adding a dopant mixture, performing a first and a second activation treatment, etc., the specific surface area of the material reaches more than 2000 m 2 / g, the pore volume is more than 1.020 cc / g, the micropore ratio is high, and the oxygen content is low, and the material has high specific surface area, high pore volume, and low oxygen content. Figure 1It can also be observed that the bio-based carbon material prepared in Example 1 has excellent pore size distribution. In Comparative Example 1, no additive-doping mixture is added, and the specific surface area, pore volume, and micropore proportion of the material are greatly reduced, and the oxygen content is increased; in Comparative Examples 2 and 3, no primary or secondary activation treatment is performed, and the specific surface area and pore volume of the material are also reduced, and the micropore proportion and oxygen content also appear adverse changes. This is because the complete process flow can make the material form a more developed pore structure, increase the specific surface area and pore volume, and effectively control the oxygen content, thereby improving the overall performance of the material.

[0102] The above merely describes the preferred embodiments of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiments, it is not intended to limit the present application, and any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, as long as the changes or modifications do not deviate from the technical solution of the present application. Any modification, equivalent change and modification of the above embodiments made according to the technical essence of the present application still fall within the scope of the technical solution of the present application.

Claims

1. A method for preparing a bio-based silicon-carbon anode porous carbon material, characterized in that, The specific steps of the preparation method are as follows: S1: Precursor Pretreatment Agricultural and forestry waste was selected as bio-based raw material and pre-carbonized at 300-600℃ for 1-4 hours. The pre-carbonized bio-based raw material was crushed, washed and dried to obtain bio-based raw material A. The particle size of bio-based raw material A was 4-10 mesh. S2: Adding dopants and mixing Pyrrole monomer was dissolved in anhydrous ethanol to prepare a solution with a mass fraction of 5-10%. Under a nitrogen atmosphere, ammonium persulfate was added to the solution, with a molar ratio of ammonium persulfate to pyrrole monomer of 1:

1. The mixed solution was stirred at 0-5°C for 6-12 hours. After the reaction was completed, the mixture was filtered and washed, and then dried in a vacuum drying oven at 60-80°C for 4-6 hours to obtain polypyrrole. A solution was prepared by mixing silane coupling agent KH-560 with anhydrous ethanol at a volume ratio of 1:(4-5). Bio-based raw material A was immersed in the silane coupling agent solution and stirred at 70°C for 3 hours. After drying, surface-modified precursor B was obtained. After filtering, washing, and drying, polypyrrole was mixed with surface-modified precursor B, ammonium dihydrogen phosphate, and alumina at a stirring speed of 200 r / min for 1–2 h to obtain precursor complex C. S3: Primary activation treatment Under a nitrogen atmosphere, the precursor complex C is activated at 700℃~900℃ for 1~3h to obtain the primary activated material D, which is then crushed to a particle size of 20~50 mesh. S4: Secondary activation treatment The primary activated material D is activated in a protective gas at a temperature of 800℃~1000℃ for 6~10h to obtain the secondary activated material E. The temperature of the activation gas is 120~180℃ and the flow rate is 200~500kg / h. S5: Pickling and Drying Treatment The pickling agent is mixed with the secondary activator E and then pickled at a temperature of 60℃~80℃ for 1~3h. After pickling, the mixture is washed until the pH is neutral and then dried at 100℃~200℃ for 1~3h to obtain solid product F. S6: Grinding and passivation treatment Solid product F was graded by air jet milling to obtain powder G. A staged passivation method was adopted. First, powder G was heated to 600-700℃ in a nitrogen atmosphere and held for 1-2 hours. Then, it was switched to a reducing atmosphere and heated to 800-950℃ for passivation for 2-4 hours to obtain the bio-based silicon-carbon anode porous carbon material.

2. The method for preparing a bio-based silicon-carbon anode porous carbon material according to claim 1, characterized in that, The agricultural and forestry waste includes one or more of bamboo, coconut shells, corn stalks, and fruit shells.

3. The method for preparing a bio-based silicon-carbon anode porous carbon material according to claim 1, characterized in that, In S2, surface-modified precursor B is used as the matrix, and the amount of ammonium dihydrogen phosphate added is 8wt%, and the amount of alumina added is 2wt%.

4. The method for preparing a bio-based silicon-carbon anode porous carbon material according to claim 1, characterized in that, The primary activator in S3 is water vapor, and the temperature is 120-140℃.

5. The method for preparing a bio-based silicon-carbon anode porous carbon material according to claim 1, characterized in that, The flow rate of the protective nitrogen gas in S4 is 5-10 L / min, and the secondary activator gas is one or more of the following mixed gases: saturated water vapor, superheated water vapor, flue gas, and oxygen, with a pressure of 15-30 kPa.

6. The method for preparing a bio-based silicon-carbon anode porous carbon material according to claim 1, characterized in that, The mass ratio of pickling agent to secondary activation material E in S5 is 1:(10-13), and the pickling agent is hydrochloric acid with a concentration of 1-3 mol / L.

7. The method for preparing a bio-based silicon-carbon anode porous carbon material according to claim 1, characterized in that, The reducing atmosphere in S6 is an H2 / He mixture, wherein the volume ratio of H2 to He is 1:

9.

8. The bio-based silicon-carbon anode porous carbon material prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The surface area of ​​the material is ≥2000m² 2 / g, micropore ratio ≥82%, total pore volume ≥1cc / g, oxygen content ≤1.5%.

9. The application of the bio-based silicon-carbon anode porous carbon material as described in claim 8 in the silicon-carbon composite anode of lithium batteries, characterized in that, The bio-based silicon-carbon anode porous carbon material is used as a framework to load nano-silicon particles through chemical vapor deposition to form a silicon-carbon composite anode material.

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