High-performance biomass hard carbon and a method for preparing the same by biological enzyme pretreatment and application thereof

Abstract

The application discloses high-performance biomass hard carbon and a preparation method and application thereof, and belongs to the field of sodium ion batteries.The preparation method of the high-performance biomass hard carbon comprises the following steps: cutting and crushing biomass raw materials, and cleaning and purifying the biomass raw materials; adding the cleaned biomass powder into a solution containing a biological enzyme for enzymatic hydrolysis pretreatment; filtering and taking out the biomass powder after the enzymatic hydrolysis pretreatment, drying the biomass powder, and then placing the biomass powder in a large atmosphere furnace for high-temperature carbonization; and then performing acid pickling and drying on the carbonized powder, so that the high-performance biomass hard carbon is obtained.The application regulates the relative contents of cellulose, hemicellulose and lignin in the biomass raw materials through a green and efficient biological enzyme pretreatment process, influences the micro-process of carbonization, and prepares the biomass hard carbon material with stable structure, and the reversible capacity and the first circle coulombic efficiency of the biomass hard carbon material are greatly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion batteries, and particularly relates to a high-performance biomass hard carbon and a biological enzyme pretreatment preparation method and application thereof. BACKGROUND

[0002] With the accelerated promotion of global energy transformation and the vigorous development of electric vehicles, energy storage systems and other fields, the battery industry has ushered in an unprecedented period of rapid development. Among them, as the core component, the market demand of secondary batteries presents a high-speed growth trend. Under this background, although lithium ion batteries have long dominated the market due to their high energy density, long cycle life and other advantages, in recent years, under the dual pressure of resource constraints and environmental protection needs, sodium ion batteries, as a powerful supplement to lithium ion batteries, are gradually returning to people's vision and receiving widespread attention.

[0003] The history of sodium ion batteries can be traced back to the early 1980s, when it was initially explored as a potential energy storage technology. However, with the rapid iteration and continuous optimization of lithium ion battery technology, especially the significant progress made in energy density and cycle stability, the research and development of sodium ion batteries once fell into a state of stagnation. This situation fundamentally changed after 2010, with the explosive growth of the new energy vehicle industry, the demand for power battery market expanded rapidly, leading to the shortage of key raw materials such as lithium and cobalt for lithium ion batteries, and the cost rose, which rekindled the hope for the research of room temperature sodium ion batteries.

[0004] Although the commercialization process of sodium ion batteries started late, its unique advantages such as abundant resources, low cost and environmental friendliness make it an important option in the future energy storage field. However, the current commercial application of sodium ion batteries still faces many challenges, among which the high cost of negative electrode materials is one of the key factors restricting its development. At present, hard carbon is the preferred negative electrode material for sodium ion batteries, and the selection of its precursor is diverse, including biomass precursors, sugar precursors, synthetic resin precursors and pitch precursors, etc. Among these options, biomass materials such as coconut shells, straw, corn cobs and other agricultural and forestry waste are considered as the preferred materials for preparing high-performance hard carbon due to their high carbon content, wide raw material sources and low price.

[0005] However, due to the large differences in cellulose, hemicellulose and lignin content between different biomass raw materials, this leads to the lack of stability of the prepared biomass hard carbon products, and also greatly affects the stability and controllability of the industrial production process. Therefore, how to maintain the controllability and stability of the biomass hard carbon preparation process among different biomass precursor raw materials while improving the technical level of biomass hard carbon has become a hot and difficult point in the current research field of sodium ion batteries. Summary of the Invention

[0006] In view of the problems and shortcomings of the existing technology, the primary objective of this invention is to provide a method for preparing high-performance biomass hard carbon through bio-enzyme pretreatment, which aims to solve the problem of unstable performance of hard carbon products caused by differences in the content of cellulose, hemicellulose and lignin in different biomass raw materials.

[0007] To achieve the above objectives, this invention proposes a method for preparing high-performance biomass hard carbon through bio-enzyme pretreatment, which includes the following specific steps:

[0008] I: The biomass raw materials are cut, crushed, cleaned, and purified;

[0009] II: Add the cleaned biomass powder to a solution containing biological enzymes for enzymatic pretreatment;

[0010] III: The biomass powder after enzymatic hydrolysis pretreatment is filtered out, dried, and then carbonized at high temperature. The carbonized powder is then acid-washed and dried to obtain high-performance biomass hard carbon.

[0011] According to some embodiments of this application, the biomass raw material is at least one of various biomass raw materials with different contents of cellulose, hemicellulose and lignin, such as bamboo, beech, eucalyptus, straw, rice straw, and fruit shells.

[0012] According to some embodiments of this application, the biomass raw material needs to be ground and pulverized, and the particle size needs to be less than 50 mesh.

[0013] According to some embodiments of this application, the biomass raw material powder needs to be cleaned and purified, and the cleaning solution is at least one of water, ethanol, petroleum ether, and hydrochloric acid.

[0014] According to some embodiments of this application, the biological enzyme includes at least one of cellulase, hemicellulase, laccase, pectinase, catalase, and amylase.

[0015] According to some embodiments of this application, the biological enzyme is a combination of cellulase, hemicellulase and laccase. Specifically, cellulase, hemicellulase and laccase are used for enzymatic hydrolysis in sequence. The conditions for cellulase, hemicellulase and laccase treatment are all: enzymatic hydrolysis at 25℃-60℃ for 6h-72h.

[0016] According to some embodiments of this application, the bioenzyme needs to be dissolved in a corresponding solution, which is a sodium citrate buffer solution with a pH between 4 and 8, preferably with a pH of 5-7, more preferably with a pH of 5-6, and most preferably with a pH of 6.0.

[0017] According to some embodiments of the present application, the enzymatic hydrolysis temperature is 25-60 DEG C, preferably the enzymatic hydrolysis temperature is 45 DEG C.

[0018] According to some embodiments of the present application, the enzymatic hydrolysis time is 6-72 hours.

[0019] According to some embodiments of the present application, when the biological enzyme is cellulase, the enzymatic hydrolysis time is greater than 24 hours, preferably 24-48 hours; when the biological enzyme is hemicellulase, the enzymatic hydrolysis time is preferably greater than 12 hours; when the biological enzyme is laccase, the enzymatic hydrolysis time is preferably greater than 12 hours.

[0020] According to some embodiments of the present application, the enzymatic hydrolysis pretreatment environment requires control of the solid-liquid ratio, the solid-liquid ratio is 1:3-1:10 (g / mL), preferably the solid-liquid ratio is 1:5 (g / mL).

[0021] According to some embodiments of the present application, the high-temperature carbonization temperature is 1200-1500 DEG C, the carbonization time is 2-6 hours, and the carbonization atmosphere is one or more of nitrogen and argon; preferably the carbonization temperature is 1400 DEG C, and the carbonization time is 3 hours.

[0022] According to some embodiments of the present application, the pickling solution is 1 mol / L hydrochloric acid solution, and the pickling time is 6-12 hours.

[0023] Another object of the present application is to provide a high-performance biomass hard carbon prepared by the above method.

[0024] The high-performance biomass hard carbon has a first circle coulomb efficiency greater than 90%, and a reversible capacity of 300-380 mAh / g.

[0025] Still another object of the present application is to provide the use of the high-performance biomass hard carbon material as a negative electrode of a sodium ion battery.

[0026] According to some embodiments of the present application, the high-performance biomass hard carbon material, a conductive agent, and a binder (8:1:1) are used to prepare a negative electrode slurry, which is coated on a copper foil, dried, sliced, and assembled with other components to obtain a sodium ion battery.

[0027] Compared with the prior art, the present application has the following technical features and advantages:

[0028] As the raw material of hard carbon synthesis, the carbon source in the biomass precursor is mainly composed of cellulose, hemicellulose and lignin. The content of the three major elements in different biomass raw materials often has a large difference, which makes the biomass hard carbon materials prepared by carbonization of different biomass raw materials often have a large difference in structure and performance. The present application adopts a green, environmentally friendly and efficient enzyme pretreatment method, and the relative content of the three major elements in the biomass raw material is further controlled by selective etching of one or more of cellulose, hemicellulose and lignin components in the biomass raw material by cellulase, hemicellulase, laccase and other biological enzymes, and the carbonization process is controlled, and the enzyme hydrolysis efficiency and degree are greatly improved by optimizing the enzyme hydrolysis environment and changing the key parameters such as pH, so that the high-performance biomass hard carbon material is stably and controllably prepared. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly set forth the technical solutions adopted by the embodiments of the present application or the prior art, the drawings involved in the embodiment or prior art description will be briefly introduced below. It should be noted that these drawings only represent some embodiments of the present application, and those skilled in the art can deduce other related drawings without creative efforts.

[0030] Figure 1 The sodium ion battery charge-discharge curve diagram of the present application example 4, the experimental results are all stable data repeated three times;

[0031] Figure 2 The sodium ion battery charge-discharge curve diagram of the present application example 8, the experimental results are all stable data repeated three times;

[0032] Figure 3 The sodium ion battery charge-discharge curve diagram of the present application example 13, the experimental results are all stable data repeated three times;

[0033] Figure 4 The sodium ion battery charge-discharge curve diagram of the present application example 16, the experimental results are all stable data repeated three times.

[0034] Figure 5 The sodium ion battery charge-discharge curve diagram of the present application comparative example 1, the experimental results are all stable data repeated three times.

[0035] The implementation, functional characteristics and advantages of the present application will be further described with reference to the drawings. DETAILED DESCRIPTION

[0036] For the purpose of clearly illustrating the objectives, technical solutions and advantages of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described in detail and accurately below. It should be noted that the following embodiments are only used to illustrate the present application, but not to limit it. Unless otherwise specified, all technical terms and scientific terms used in the present application follow the general definitions in the technical field, and the reagents mentioned reach the industrial pure or analytical pure standard. In addition, the provided drawings and descriptions are intended to help those skilled in the art to understand the present application in depth, but not to limit the subject matter covered by the claims.

[0037] As for the "range" mentioned in the present application, it is defined by setting a lower limit and an upper limit, which define the boundaries of a specific range. Such a range can or can not include its end value, and can be freely combined, i.e. any lower limit can be combined with any upper limit to form a new range.

[0038] Unless otherwise specified, all embodiments in the present application and their optional solutions can be combined with each other to create new technical solutions. Similarly, unless otherwise specified, all technical features in the present application and their optional features can also be combined with each other to form new technical solutions.

[0039] The present application will be described in detail below, which includes the following specific steps:

[0040] I: cutting and crushing the biomass raw material, and cleaning and purifying it;

[0041] II: adding the cleaned biomass powder into a solution containing biological enzymes for enzymatic pretreatment;

[0042] III: filtering out the biomass powder after enzymatic pretreatment, drying it and then placing it in a large atmosphere furnace for high-temperature carbonization, and then performing acid washing and drying on the carbonized powder to obtain high-performance biomass hard carbon.

[0043] Preferably, the biomass raw material in step I is Japanese zelkova, and the grinding particle size is less than 50 mesh.

[0044] Preferably, the biological enzyme used in step II is one or more of cellulase, hemicellulase and laccase, the enzymatic hydrolysis temperature is 45℃, the enzymatic hydrolysis time is 6-72h, and the enzymatic hydrolysis solution pH is 6.0.

[0045] Preferably, nitrogen is used as the carbonization atmosphere in step III, the carbonization temperature is 1400℃, and the carbonization time is 3h.

[0046] The present application will be described in further detail below in combination with the embodiments:

[0047] The biological enzymes used in the present application are purchased from Shanghai Yuan Ye Biological Co., Ltd. without any additional treatment.

[0048] Example 1

[0049] I: 500g of beech raw material was cut and crushed to a particle size of less than 50 mesh, and sequentially washed and purified with water and ethanol;

[0050] II: The washed beech powder was added to a solution containing cellulase (sodium citrate buffer with pH 6.0) at a solid-liquid ratio of 1:5 g / mL, and the solution was placed in a water bath at 45°C for heating and stirring. After 6h of enzymatic hydrolysis, the beech powder was filtered out.

[0051] III: The enzyme-hydrolyzed pretreated beech powder was dried and then placed in a large atmosphere furnace for high-temperature carbonization at 1400°C for 3h in a nitrogen atmosphere. Subsequently, the carbonized powder was acid washed with 1 mol / L hydrochloric acid solution, and then dried to obtain high-performance biomass hard carbon.

[0052] Example 2

[0053] Example 2 and Example 1 are basically the same in the preparation process, except that the enzyme hydrolysis time in step II of preparing high-performance biomass hard carbon is extended to 12h.

[0054] Example 3

[0055] Example 3 and Example 1 are basically the same in the preparation process, except that the enzyme hydrolysis time in step II of preparing high-performance biomass hard carbon is extended to 24h.

[0056] Example 4

[0057] Example 4 and Example 1 are basically the same in the preparation process, except that the enzyme hydrolysis time in step II of preparing high-performance biomass hard carbon is extended to 48h.

[0058] Example 5

[0059] Example 5 and Example 1 are basically the same in the preparation process, except that the enzyme hydrolysis time in step II of preparing high-performance biomass hard carbon is extended to 72h.

[0060] Example 6

[0061] I: 500g of beech raw material was cut and crushed to a particle size of less than 50 mesh, and sequentially washed and purified with water and ethanol;

[0062] II: The washed beech powder was added to a solution containing hemicellulase (sodium citrate buffer with pH 6.0) at a solid-liquid ratio of 1:5 g / mL, and the solution was placed in a water bath at 45°C for heating and stirring. After 6h of enzymatic hydrolysis, the beech powder was filtered out.

[0063] III: The enzyme pretreated beech powder is dried and then carbonized at 1400°C for 3h in a large atmosphere furnace, with nitrogen as the carbonization atmosphere. The carbonized powder is then washed with 1 mol / L hydrochloric acid solution and dried, to obtain the high-performance biomass hard carbon.

[0064] Example 7

[0065] Example 7 is basically the same as the preparation process of Example 6, except that the enzyme hydrolysis time in step II of preparing the high-performance biomass hard carbon is extended to 12h.

[0066] Example 8

[0067] Example 8 is basically the same as the preparation process of Example 6, except that the enzyme hydrolysis time in step II of preparing the high-performance biomass hard carbon is extended to 24h.

[0068] Example 9

[0069] Example 9 is basically the same as the preparation process of Example 6, except that the enzyme hydrolysis time in step II of preparing the high-performance biomass hard carbon is extended to 48h.

[0070] Example 10

[0071] Example 10 is basically the same as the preparation process of Example 6, except that the enzyme hydrolysis time in step II of preparing the high-performance biomass hard carbon is extended to 72h.

[0072] Example 11

[0073] I: 500g of beech raw material is cut and crushed to a particle size of less than 50 mesh, and then washed and purified with water and ethanol in sequence;

[0074] II: The washed beech powder is added to a solution containing laccase (sodium citrate buffer with pH 6.0) at a solid-liquid ratio of 1:5 g / mL, and the solution is heated and stirred in a water bath at 45°C. After 6h of enzyme hydrolysis, the beech powder is filtered out.

[0075] III: The enzyme pretreated beech powder is dried and then carbonized at 1400°C for 3h in a large atmosphere furnace, with nitrogen as the carbonization atmosphere. The carbonized powder is then washed with 1 mol / L hydrochloric acid solution and dried, to obtain the high-performance biomass hard carbon.

[0076] Example 12

[0077] Example 12 is basically the same as the preparation process of Example 11, except that the enzyme hydrolysis time in step II of preparing the high-performance biomass hard carbon is extended to 12h.

[0078] Example 13

[0079] Example 13 is substantially the same as the preparation process of Example 11, except that the enzymolysis time in Step II of preparing the high-performance biomass hard carbon is extended to 24 h.

[0080] Example 14

[0081] Example 14 is substantially the same as the preparation process of Example 11, except that the enzymolysis time in Step II of preparing the high-performance biomass hard carbon is extended to 48 h.

[0082] Example 15

[0083] Example 15 is substantially the same as the preparation process of Example 11, except that the enzymolysis time in Step II of preparing the high-performance biomass hard carbon is extended to 72 h.

[0084] Example 16

[0085] I: 500 g of beech raw material is cut and crushed to a particle size of less than 50 mesh, and then washed and purified with water and ethanol in sequence;

[0086] II: The washed beech powder is added to a solution containing cellulase (sodium citrate buffer with pH 6.0) at a solid-liquid ratio of 1:5 g / mL, and the solution is placed in a water bath at 45°C for heating and stirring. After 48 h of enzymolysis, the beech powder is filtered out. Then the cellulase and hemicellulase pretreated beech powder is added to a solution containing laccase (sodium citrate buffer with pH 6.0) at a solid-liquid ratio of 1:5 g / mL, and the solution is placed in a water bath at 45°C for heating and stirring. After 24 h of enzymolysis, the cellulase and hemicellulase pretreated beech powder is added to a solution containing laccase (sodium citrate buffer with pH 6.0) at a solid-liquid ratio of 1:5 g / mL, and the solution is placed in a water bath at 45°C for heating and stirring. After 24 h of enzymolysis, the cellulase and hemicellulase pretreated beech powder is added to a solution containing laccase (sodium citrate buffer with pH 6.0) at a solid-liquid ratio of 1:5 g / mL, and the solution is placed in a water bath at 45°C for heating and stirring.

[0087] III: The enzymolysis pretreated beech powder is dried and placed in a large atmosphere furnace for high-temperature carbonization at 1400°C for 3 h in a nitrogen atmosphere. Then the carbonized powder is acid washed and dried with 1 mol / L hydrochloric acid solution to obtain the high-performance biomass hard carbon.

[0088] Comparative Example 1

[0089] I: 500 g of beech raw material is cut and crushed to a particle size of less than 50 mesh, and then washed and purified with water and ethanol in sequence;

[0090] II: The washed beech powder is dried and then placed in a large atmosphere furnace for high-temperature carbonization at 1400°C for 3h, with nitrogen as the carbonization atmosphere, and then the carbonized powder is washed with 1 mol / L hydrochloric acid solution and dried, to obtain high-performance biomass hard carbon.

[0091] Comparative Example 2

[0092] I: 500g of beech raw material is cut and crushed to a particle size of less than 50 mesh, and then washed and purified;

[0093] II: The washed beech powder is added to a solution containing cellulase (sodium citrate buffer with pH 4.0) at a solid-liquid ratio of 1:5 g / mL, and the solution is heated and stirred in a water bath at 45°C. After 48h of enzymatic hydrolysis, the beech powder is filtered out.

[0094] III: The enzyme-hydrolysis pretreated beech powder is dried and then placed in a large atmosphere furnace for high-temperature carbonization at 1400°C for 3h, with nitrogen as the carbonization atmosphere, and then the carbonized powder is washed with 1 mol / L hydrochloric acid solution and dried, to obtain high-performance biomass hard carbon.

[0095] Comparative Example 3

[0096] Comparative Example 3 and Comparative Example 2 have basically the same preparation process, except that the pH of the enzymatic hydrolysis environment in step II of preparing high-performance biomass hard carbon is 7.0.

[0097] Comparative Example 4

[0098] Comparative Example 3 and Comparative Example 2 have basically the same preparation process, except that the pH of the enzymatic hydrolysis environment in step II of preparing high-performance biomass hard carbon is 8.0.

[0099] Comparative Example 5

[0100] I: 500g of beech raw material is cut and crushed to a particle size of less than 50 mesh, and then washed and purified;

[0101] II: The washed beech powder is added to a solution containing hemicellulase (sodium citrate buffer with pH 4.0) at a solid-liquid ratio of 1:5 g / mL, and the solution is heated and stirred in a water bath at 45°C. After 24h of enzymatic hydrolysis, the beech powder is filtered out.

[0102] III: The enzyme-hydrolysis pretreated beech powder is dried and then placed in a large atmosphere furnace for high-temperature carbonization at 1400°C for 3h, with nitrogen as the carbonization atmosphere, and then the carbonized powder is washed with 1 mol / L hydrochloric acid solution and dried, to obtain high-performance biomass hard carbon.

[0103] Comparative Example 6

[0104] Preparation process of Comparative Example 6 is basically the same as that of Comparative Example 5, except that the pH of the enzymatic environment in step II of preparing high-performance biomass hard carbon is 7.0.

[0105] Comparative Example 7

[0106] Preparation process of Comparative Example 7 is basically the same as that of Comparative Example 5, except that the pH of the enzymatic environment in step II of preparing high-performance biomass hard carbon is 8.0.

[0107] Comparative Example 8

[0108] I: 500g of beech raw material was cut and crushed to a particle size of less than 50 mesh, and washed and purified;

[0109] II: The washed beech powder was added to a solution containing laccase (pH 4.0 sodium citrate buffer) at a solid-liquid ratio of 1:5 g / mL, and the solution was placed in a 45°C water bath for heating and stirring. After 24h of enzymatic hydrolysis, the beech powder was filtered out.

[0110] III: The enzyme-hydrolyzed pretreated beech powder was dried and placed in a large atmosphere furnace for high-temperature carbonization at 1400°C for 3h, with nitrogen as the carbonization atmosphere. Subsequently, the carbonized powder was acid washed with 1 mol / L hydrochloric acid solution and dried to obtain high-performance biomass hard carbon.

[0111] Comparative Example 9

[0112] Preparation process of Comparative Example 9 is basically the same as that of Comparative Example 8, except that the pH of the enzymatic environment in step II of preparing high-performance biomass hard carbon is 7.0.

[0113] Comparative Example 10

[0114] Preparation process of Comparative Example 10 is basically the same as that of Comparative Example 8, except that the pH of the enzymatic environment in step II of preparing high-performance biomass hard carbon is 8.0.

[0115] Further, the biomass hard carbon materials prepared in the above examples and comparative examples were configured into negative electrode slurry according to a mass ratio of hard carbon: conductive agent: binder (8:1:1), and coated on a current collector (copper foil). Subsequently, the slurry was dried and sliced, and a C2032 button cell was assembled in a glove box, and after standing for 12h, it was placed in a new battery test channel for related sodium storage performance testing.

[0116] From the first charge-discharge curve of Figure 1 It can be seen from the first charge-discharge curve of that the high-performance biomass hard carbon material prepared by cellulase enzymatic hydrolysis for 48h in Example 4 has a first coulomb efficiency of 92% and a first charge specific capacity of 366mAh / g at a current density of 20mA / g;

[0117] From the first charge-discharge curves of Figure 2 It can be seen from the first charge-discharge curves of

[0118] From the first charge-discharge curves of Figure 3 It can be seen from the first charge-discharge curves of

[0119] From the first charge-discharge curves of Figure 4 It can be seen from the first charge-discharge curves of

[0120] The test results of the examples and the comparative examples are summarized in the following table:

[0121]

[0122]

[0123] From Examples 1-15 and Comparative Example 1, it can be seen that the high-performance biomass hard carbon obtained in Examples 4, 8, and 13 has a significant improvement in both reversible charge capacity and first-cycle coulombic efficiency compared to Comparative Example 1 without biomass enzyme pretreatment. Among them, Example 4 as the optimal example of cellulase pretreatment has a reversible capacity of 366 mAh / g and a first-cycle coulombic efficiency of 92%; Example 8 as the optimal example of hemicellulase pretreatment has a reversible capacity of 351 mAh / g and a first-cycle coulombic efficiency of 95%; and Example 13 as the optimal example of laccase pretreatment has a reversible capacity of 356 mAh / g and a first-cycle coulombic efficiency of 93%. Further, the present application combines the optimal treatment and regulation of three biomass enzymes, and adjusts the cellulose, hemicellulose, and lignin content of the biomass raw material in turn, and prepares the final Example 16. The high-performance biomass hard carbon material prepared after the adjustment and optimization of the three components has a reversible capacity of 383 mAh / g and a first-cycle coulombic efficiency of 90%, which is greatly improved compared to Comparative Example 1, which directly indicates that the three major element contents in the biomass precursor are closely related to the performance of the prepared biomass-based hard carbon material. By integrating the biomass enzyme pretreatment process, the relative content between the three major elements can be adjusted to prepare a biomass-based hard carbon material with excellent performance.

[0124] Meanwhile, by comparing the enzymatic environment of Comparative Example 2-10, it can be seen that the effect of enzymatic pretreatment is significantly different after changing the pH, wherein when the pH of the enzymatic pretreatment solution is changed to a stronger acidic environment (pH = 4.0) and when the pH of the enzymatic pretreatment solution is changed to an alkaline environment (pH = 8.0), the performance of Comparative Example 2, Example 5, Example 8 and Comparative Example 4, Example 7, Example 10 is significantly lower than that of optimal Example 4, Example 8, Example 13, indicating that in a stronger acidic environment and an alkaline environment, the biological enzyme pretreatment is obviously inactivated and cannot achieve the regulating effect on the cellulose, hemicellulose and lignin components in the biomass raw material. When the pH of the enzymatic pretreatment solution is changed to a neutral environment (pH = 7.0), the performance of Comparative Example 2, Example 5, Example 8 and Comparative Example 3, Example 6, Example 9 is lower than that of optimal Example 4, Example 8, Example 13, but is obviously improved compared with Example 1, Example 6, Example 10, indicating that the biological enzyme pretreatment can play a role in a neutral environment, but the efficiency is low, and the time cost of the biomass pretreatment is great, so the optimal biological enzyme pretreatment environment is determined to be a weak acidic environment with pH of 6.0.

[0125] The above experimental results prove that the biological enzyme pretreatment method adopted in the present application can efficiently and stably regulate the relative content of cellulose, hemicellulose and lignin components in the biomass precursor, so that the three components maintain a balance in the carbonization process, thereby preparing high-performance biomass hard carbon with suitable structure and excellent performance. The method of the present application not only has the characteristics of green and efficient process and low environmental toxicity, but also can greatly improve the reversible capacity and first-cycle coulomb efficiency of the prepared biomass hard carbon.

[0126] The above examples are only used to help understand the method of the present application and its core idea. It should be noted that any changes, modifications, substitutions, combinations and simplifications made by those skilled in the art without departing from the spirit and principles of the present application are equivalent replacement methods and are included in the protection scope of the present application.

Claims

1. A method for preparing high-performance biomass hard carbon by biological enzyme pretreatment, characterized in that, The method comprises the following steps: I: cutting and crushing the biomass raw material, and cleaning and purifying the same; II: adding the cleaned biomass powder into a solution containing biological enzymes for enzymatic pretreatment; the biological enzymes need to be dissolved in a corresponding culture solution, and the solution is a sodium citrate buffer solution with a pH of 5.0-6.0; the enzymatic pretreatment is carried out by using cellulase, hemicellulase and laccase in sequence, and the enzymatic conditions of the cellulase, hemicellulase and laccase are as follows: enzymolysis at 25-60 ℃ for 6-72 h; the solid-liquid ratio needs to be controlled in the enzymatic pretreatment environment, and the solid-liquid ratio is 1:3-1:10 g / mL; III: filtering out the biomass powder after the enzymatic pretreatment, drying the same, and then carrying out high-temperature carbonization, and then carrying out acid pickling on the carbonized powder, and then drying the same to obtain high-performance biomass hard carbon.

2. The method of claim 1, wherein the biomass is pretreated with a biocatalyst to produce a high-performance hard carbon. In step I, the biomass raw material is at least one of bamboo, Japanese beech, eucalyptus, straw, rice straw and fruit shell.

3. The method of claim 1, wherein the biomass is pretreated with a combination of enzymes and chemicals. The enzymolysis temperature is 45 ℃.

4. The method of claim 1, wherein the biomass is pretreated with a combination of enzymes and chemicals. In step II, the solid-liquid ratio is 1:5 g / mL.

5. The method of claim 1, wherein the biomass is pretreated with a combination of enzymes and chemicals. In step III, the high-temperature carbonization temperature is 1200-1500 ℃, the carbonization time is 2-6 h, and the carbonization atmosphere is one or more of nitrogen and argon.

6. The method of claim 5, wherein the biomass is pretreated with a combination of enzymes and chemicals. The high-temperature carbonization temperature is 1400 ℃, and the carbonization time is 3 h.

7. A high performance biomass hard carbon, characterized by, The high-performance biomass hard carbon is prepared by the biological enzyme pretreatment method according to any one of claims 1-6.

8. The use of the high-performance biomass hard carbon according to claim 7, characterized in that, The high-performance biomass hard carbon material is used as a negative electrode of a sodium ion battery.

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