Method for preparing composite carbon material through biomass template method and application

Abstract

The invention relates to a method for preparing a composite carbon material through a biomass template method and application, and belongs to the technical field of composite carbon materials. The method comprises the following steps: stirring and fusing an aqueous solution of bacteria and formaldehyde, adding resorcinol, water and a catalyst, carrying out a stirring reaction, carrying out a hydrothermal reaction in a high-pressure reaction kettle, carrying out solid-liquid separation, and taking a solid to obtain a precursor of phenolic resin-based hard carbon; and drying the precursor of the phenolic resin-based hard carbon, and carrying out carbonization treatment in a protective atmosphere. In the aspect of electrochemical performance, the phenolic resin-based hard carbon generated by the invention shows better reversible specific capacity when being used as a negative electrode of a sodium-ion battery, the reversible specific capacity of first-circle discharge of the battery reaches 273mAh g <-1 > under the current density of 20mAg <-1 >, and the reversible capacity of 140mAh g <-1 > after circulation for 40 circles under the current density of 20mAg <-1 > is still achieved; and the material has excellent cycling stability and rate capability.

Description

Technical Field

[0001] The present invention relates to the technical field of composite carbon materials, and in particular to a method and application for preparing composite carbon materials by a biomass template method. Background Art

[0002] At present, the energy demands of countries around the world still mainly rely on fossil fuels with limited reserves such as oil and coal. However, under the promotion of the sustainable development strategy that countries increasingly attach importance to, new energy sources such as wind energy, hydrogen energy, and photovoltaic power generation have developed rapidly, which makes the importance of large-scale energy storage technology increasingly prominent. For a long time before, lithium-ion secondary batteries have been continuously researched, developed and widely used in the fields of consumer electronics and electric vehicles due to their outstanding performance such as high energy density, good rate performance, and long cycle life. However, this has made the already scarce lithium ore resources even more scarce, and the cost of lithium-ion batteries has extremely unstable factors. Therefore, developing new energy storage technologies is an irresistible trend.

[0003] Bacteria are a common biomass template. Bacteria have a unique microscopic organic structure, with small size and diverse shapes, including spherical, rod-shaped, spiral-shaped, etc., which is conducive to preparing biomass templates with different shapes and structures, thereby constructing biomaterials with specific functions. Bacteria have the ability of self-assembly and can spontaneously form ordered structures under specific conditions. This self-assembly characteristic makes bacterial templates have unique advantages in the preparation of nanomaterials and biomaterials. Bacteria have high biocompatibility and can combine with a variety of biomaterials, and can be used as templates for the preparation of biomaterials to construct structures with specific shapes and functions. By means of genetic engineering and other means, the growth and metabolic processes of bacteria can be regulated, thereby achieving precise control of bacterial templates. This makes bacterial templates have unique advantages in the preparation of complex structures and nanomaterials. The cultivation and reproduction of bacteria are relatively simple and the cost is low. Therefore, using bacteria as a biomass template for large-scale production has economic advantages. And the preparation process of bacterial templates usually does not involve toxic or harmful chemical substances, is green and environmentally friendly, and meets the requirements of sustainable development.

[0004] Phenolic resin has the advantages of cost-effectiveness and wide use. And most importantly, it can precisely control the structure of the produced hard carbon during the carbonization process. This control is undoubtedly the greatest advantage of phenolic resin-based hard carbon, because the microscopic structural characteristics of hard carbon directly affect the sodium ion storage mechanism and efficiency, and it alone accounts for one-fifth of the polymer precursors used for HC synthesis. The greatest advantages of these polymers are their high carbon yield (about 50%) and their solubility in different solvents, which enables them to be used in wet chemistry to obtain different carbon structures (fibers, spheres, etc.).

[0005] Prior art involves obtaining negative electrode hard carbon from various biomass precursors such as corncobs, lotus flowers, various nut shells, pine trees, and different trees; using biopolymers of plants such as sucrose, cellulose, glucose, and lignin for synthesizing hard carbon. And various synthetic polymers have been used to synthesize HC materials such as pitch, polyvinyl chloride, polyacrylonitrile, and phenolic resin. Such synthetic polymers have the advantages of being cost-effective, widely used, and capable of precisely controlling the structure of the generated hard carbon during the carbonization process. Controlling the microstructure characteristics of hard carbon in this way directly affects the sodium ion storage mechanism and efficiency.

[0006] However, in prior art, the first irreversible capacity loss of biomass hard carbon is relatively high, resulting in a relatively low first charge-discharge efficiency. The true density and bulk density of biomass hard carbon are not high, which may affect its energy density and endurance in the battery. Summary of the Invention

[0007] The storage capacity of traditional phenolic resin-based hard carbon is usually low, making it difficult to achieve the high capacity required for commercialization, and their shape and pore structure also cannot meet the requirements of sodium ion batteries. To address this problem, the present invention provides a method and application for preparing a composite carbon material by a biomass template method. By coating Escherichia coli with phenolic resin, the structure and specific surface area of phenolic resin-based hard carbon can be effectively improved, and its conductivity can be increased, thereby enhancing the electrochemical properties such as the capacity, cycle performance, and rate performance of sodium ion batteries.

[0008] The present invention applies bacterial coating on phenolic resin to manufacture a hard carbon negative electrode material for sodium ion batteries with excellent performance. Phenolic resin is well-known for its thermal stability and mechanical strength and is used in a wide range of industrial applications. The present invention integrates biotechnology innovation with energy storage systems, especially by coating bacteria (Escherichia coli) with phenolic resin and then sintering and carbonizing. The potential improvement of electrode performance due to the unique interaction between bacterial cells and the carbon matrix focuses on the optimization of pore size distribution and specific surface area and the resulting electrochemical properties.

[0009] The present invention is achieved through the following technical solutions:

[0010] The first object of the present invention is to provide a method for preparing a composite carbon material by a biomass template method, including the following steps:

[0011] Stir and fuse an aqueous solution of bacteria with formaldehyde, add resorcinol, water, and a catalyst, stir and react, conduct hydrothermal reaction in a high-pressure reaction kettle, take the solid after solid-liquid separation to obtain a precursor of phenolic resin-based hard carbon;

[0012] Dry the obtained precursor of phenolic resin-based hard carbon and conduct carbonization treatment under a protective atmosphere.

[0013] In one embodiment of the present invention, the bacteria include Escherichia coli, Staphylococcus aureus, Bacillus subtilis, etc.

[0014] In one embodiment of the present invention, when the mass ratio of Escherichia coli to phenolic resin is 1:1, the addition concentration of the bacteria is 1.2×10 7 cfu / mL, with a total of 10 mL.

[0015] In one embodiment of the present invention, the molar ratio of resorcinol to formaldehyde is 1:1 - 1:3; specifically 1:1, 1:2, 1:3, etc., and preferably 1:2.

[0016] And / or, the concentration of formaldehyde is 30 wt% - 40 wt%.

[0017] In one embodiment of the present invention, the time of the stirring reaction is 15 h - 25 h.

[0018] In one embodiment of the present invention, the conditions of the hydrothermal reaction are: hydrothermal reaction at 80°C - 150°C for 20 h - 35 h.

[0019] In one embodiment of the present invention, the conditions of the drying are: maintaining at 60°C - 80°C for 12 h - 24 h.

[0020] In one embodiment of the present invention, the conditions of the carbonization are: carbonization at 1100°C - 1300°C for 2 h - 3.5 h;

[0021] And / or, the heating rate of the carbonization is 5°C / min;

[0022] And / or, the protective atmosphere is one or more of argon, helium, neon, and nitrogen.

[0023] The second object of the present invention is to provide a composite carbon material prepared by the above method, with bacteria coated on the surface of phenolic resin.

[0024] In one embodiment of the present invention, the mass ratio of the bacteria to phenolic resin is 1 - 3:1.

[0025] The third object of the present invention is to provide the application of the composite carbon material in the energy storage field.

[0026] The fourth object of the present invention is to provide a sodium-ion battery using the composite carbon material as the negative electrode material.

[0027] The above technical solutions of the present invention have the following advantages compared with the prior art:

[0028] (1) The present invention provides a method and application for preparing composite carbon materials by a biomass template method. The phenolic resin-based hard carbon generated by the present invention has a smaller particle size and a smaller specific surface area, has a large number of micropores and a more abundant mesoporous structure in terms of pore size, and the impedance is also much lower than that of ordinary phenolic resin hard carbon.

[0029] (2) In terms of electrochemical performance, when used as the negative electrode of a sodium-ion battery, it exhibits a better reversible specific capacity. At a current density of 20 mA g -1 , the reversible specific capacity of the first-cycle discharge of the battery reaches 273 mAh g -1 , and after 40 cycles at a current density of 20 mA g -1 , there is still a reversible capacity of 140 mAh g -1 , showing excellent cycle stability and rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to make the content of the present invention easier to be clearly understood, the following further describes the present invention in detail according to the specific embodiments of the present invention in conjunction with the drawings, wherein,

[0031] Figure 1 is the SEM image of the phenolic resin-based hard carbon of the present invention;

[0032] Figure 2 is the SEM image of the pure phenolic resin hard carbon in Comparative Example 1 of the present invention;

[0033] Figure 3 is the SEM image of the pure phenolic resin hard carbon with iron and cobalt salts added in the control group of the present invention;

[0034] Figure 4 is the charge-discharge curve of the battery assembled with the phenolic resin-based hard carbon of the present invention at a rate of 0.1C;

[0035] Figure 5 is the cycle performance of the battery assembled with the phenolic resin-based hard carbon of the present invention at a rate of 0.1C;

[0036] Figure 6 is the charge-discharge curve of the battery assembled with the pure phenolic resin hard carbon in Comparative Example 1 of the present invention at a rate of 0.1C;

[0037] Figure 7 is the charge-discharge curve of the battery assembled with the salt-added pure phenolic resin-based hard carbon in Comparative Example 2 of the present invention at a rate of 0.1C. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The following further describes the present invention in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present invention and can implement it, but the embodiments cited do not limit the present invention.

[0039] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods. The materials, reagents, etc. used can be obtained from commercial sources unless otherwise specified.

[0040] The present invention provides a hard carbon material prepared by coating phenolic resin with bacteria as a template. The material is prepared by the following method:

[0041] Example 1

[0042] This example provides a method for preparing a composite carbon material of bacteria-coated phenolic resin by a biomass template method. Among them, the mass ratio of Escherichia coli to phenolic resin is 1:1, that is, Escherichia coli: phenolic resin = 100 wt% hard carbon synthesis, specifically as follows:

[0043] Take two tubes of Escherichia coli (concentration of 1.2×10 7 cfu / mL, a total of 10 mL) that have been washed with pure water and alcohol, add 50 mL of pure water to it and stir evenly, then pour it into a 250 mL beaker. Then, 2.05 g of formaldehyde (37 wt%) is dropped into it while continuously stirring until completely fused. Subsequently, 1.4 g of resorcinol (the molar ratio of resorcinol to formaldehyde is 1:2) is added to it, and 100 mL of pure water and 1 mL of ammonia water are added as a catalyst at the final stage to promote the polymerization process of the reactants. The magnetic stirrer is used to continuously stir for 20 h. After the reaction is completed, the former is transferred to a high-pressure reactor (less than 1.27 Atm) and hydrothermally treated at 100 °C for 30 h to prepare a precursor of phenolic resin-based hard carbon. After hydrothermal treatment, the mixed solution is precipitated by a centrifuge, and then the phenolic resin in it is washed three times with pure water and ethanol. Next, the collected precipitate is placed in a constant temperature blast dryer and kept at an ambient temperature of 80 °C for 12 h to obtain a red-brown phenolic resin powder containing a bacterial structure. Then, these phenolic resin powders are carbonized at a high temperature of 1100 °C for 3 h at 1100 °C, while introducing Ar as a protective gas and setting a slow heating rate (5 °C / min) to obtain a composite carbon material of bacteria-coated phenolic resin.

[0044] Example 2

[0045] This example provides a method for preparing a composite carbon material of bacteria-coated phenolic resin by a biomass template method. Among them, the mass ratio of Escherichia coli to phenolic resin is 1:2, that is, Escherichia coli: phenolic resin = 50 wt% hard carbon synthesis, specifically as follows:

[0046] Take two tubes of Escherichia coli that have been washed with pure water and alcohol. Add 30 mL of pure water to them, stir well, and pour the mixture into a 150 mL beaker. Then, drop 1.025 g of formaldehyde (37 wt%) into it while continuously stirring until it is completely fused. Subsequently, add 0.7 g of resorcinol (the ratio of resorcinol to formaldehyde is 1:2), and at the final stage, add 45 mL of pure water and 1 mL of ammonia water as a catalyst to promote the polymerization process of the reactants. Continuously stir for 20 h using a magnetic stirrer. After the reaction is completed, transfer the former to a high-pressure reactor and hydrothermally treat it at 100 °C for 30 h to prepare a precursor of phenolic resin-based hard carbon. After hydrothermal treatment, centrifuge the mixed solution for precipitation, and then wash the phenolic resin in it three times with pure water and ethanol. Next, place the collected precipitate in a constant-temperature blast dryer and keep it at an environmental temperature of 80 °C for 12 h to obtain a red-brown phenolic resin powder containing bacterial structures. Then, carbonize these phenolic resin powders at a high temperature of 1100 °C, introduce Ar gas as a protective gas at the same time, and set a slow heating rate (5 °C / min) to obtain a composite carbon material of bacterial-coated phenolic resin, phenolic resin-based hard carbon.

[0047] The SEM image of the phenolic resin-based hard carbon described in this example is as Figure 1 shown. It can be seen from the figure that the obtained material is different from the sample with the smooth surface of Escherichia coli but retains its structure, indicating that the carbon material has been successfully coated on the surface of the carbon material.

[0048] Example 3

[0049] This example provides a method for preparing a composite carbon material of bacterial-coated phenolic resin by a biomass template method. Among them, the mass ratio of Escherichia coli to phenolic resin is 1:3, that is, Escherichia coli:phenolic resin = 33 wt% hard carbon synthesis, specifically as follows:

[0050] Take two tubes of bacteria that have been washed with pure water and alcohol. Add 30 mL of pure water to them, stir well, and pour the mixture into a 100-mL beaker. Then, add 0.68 g of formaldehyde (37 wt%) dropwise while continuously stirring until completely fused. Subsequently, add 0.47 g of resorcinol (the ratio of resorcinol to formaldehyde is 1:2), and in the final stage, add 20 mL of pure water and 1 mL of ammonia water as a catalyst to promote the polymerization process of the reactants. Continuously stir for 20 h using a magnetic stirrer. After the reaction is completed, transfer the former to a high-pressure reactor and hydrothermally treat it at 100 °C for 30 h to prepare a precursor of phenolic resin-based hard carbon. After hydrothermal treatment, the mixed solution was precipitated by a centrifuge, and then the phenolic resin in it was washed three times with pure water and ethanol. Next, the collected precipitate was placed in a constant-temperature blast dryer and kept at an ambient temperature of 80 °C for 12 h to obtain a red-brown phenolic resin powder containing a bacterial structure. Then, the phenolic resin powder was carbonized at a high temperature of 1100 °C, while introducing Ar gas as a protective gas and setting a slow heating rate (5 °C / min) to obtain a composite carbon material with bacteria-coated phenolic resin.

[0051] Comparative Example 1

[0052] This comparative example provides a method for preparing a phenolic resin composite carbon material, which is similar to Example 2, except that: Escherichia coli is not added.

[0053] The SEM image of the obtained material is as Figure 2 shown. It can be seen from Figure 2 that without adding bacteria, the phenolic resin presents a spherical shape, and the resulting hard carbon material has fewer closed pores and relatively poor sodium storage capacity.

[0054] Comparative Example 2

[0055] This comparative example provides a method for preparing a composite carbon material, which is as follows:

[0056] Take two tubes of bacteria that have been washed with pure water and alcohol, add 30 mL of pure water to them, stir well, and pour the mixture into a 100 mL beaker. Then, add 1.025 g of formaldehyde (37 wt%) dropwise while continuously stirring until completely fused. Subsequently, add 0.7 g of resorcinol (the ratio of resorcinol to formaldehyde is 1:2), 1 g of iron nitrate, and 1 g of cobalt nitrate. At the final stage, add 20 mL of pure water and 1 mL of ammonia water as a catalyst to promote the polymerization process of the reactants, and continuously stir for 20 h using a magnetic stirrer. After the reaction is completed, transfer the former to a high-pressure reactor and hydrothermally treat it at 100 °C for 30 h to prepare a precursor of phenolic resin-based hard carbon. After hydrothermal treatment, the mixed solution was precipitated by a centrifuge, and then the phenolic resin in it was washed three times with pure water and ethanol. Next, the collected precipitate was placed in a constant-temperature blast dryer and kept at an ambient temperature of 80 °C for 12 h to obtain a red-brown phenolic resin powder containing bacterial structures. Then, the phenolic resin powders were carbonized at a high temperature of 1100 °C, introducing Ar gas as a protective gas and setting a slow heating rate (5 °C / min) to obtain a composite carbon material with bacteria-coated phenolic resin. Its SEM image is as shown in Figure 3 shown. It can be seen from Figure 3 that its morphology is similar to that of Example 2, but its morphology size is not as close as that of Example 2, nor is it as evenly distributed as that of Example 2.

[0057] Performance Test

[0058] The electrode sheet was prepared by the coating method. The preparation process is as follows: First, mix the composite carbon materials (80 wt%), conductive agent SuperP (5 wt%), and polyvinylidene fluoride (PVDF, 10 wt%) prepared in Example 1, Example 2, or Comparative Example 1-2, and then mix them with N-methylpyrrolidone. Then, put the mixture into a small rubber tube, add 10 ball-milling beads with a diameter of 3 mm, and ball-mill the mixture 3 times for 1 min each time. Finally, coat the uniform slurry obtained after ball-milling on the surface of a clean and flat copper foil (matte surface) with a 100 μm scraper, and ensure that the electrode slurry is flat. Subsequently, transfer it to a vacuum oven and dry it at 80 °C for 12 h. After the drying step, a smooth electrode sheet with a smooth surface, no cracks, and no pores was obtained. Then, cut this electrode sheet into a circular sheet with a diameter of 13 mm for use.

[0059] The R2025 button cell was used as the battery model. The prepared positive electrode sheet had a diameter of 13 mm and a thickness of 0.45 mm, and its appearance was a bright and unoxidized sodium metal disc. The negative electrode was a sodium metal disc with a diameter of 13 mm and a thickness of 0.45 mm. The separator was made of glass fiber (model Whatman GF / A). The electrolyte was a mixture of ethylene carbonate (EC) and propylene carbonate (PC) in a ratio of 1:1. NaClO4 was used as the solute to prepare a 1 M concentration solution. The battery assembly was carried out in a glove box filled with inert gas argon, and it was ensured that the contents of water and oxygen in the glove box were both controlled below 0.5 ppm. After the battery assembly was completed, it was left standing at room temperature for 24 h.

[0060] The assembled button cell was controlled at room temperature and subjected to charge-discharge tests at a rate of 0.1C.

[0061] The charge-discharge curve of the battery prepared with the phenolic resin-based hard carbon obtained in Example 2 at a rate of 0.1C is as Figure 4 shown, where 1st, 2nd, 5th, 10th, and 50th refer to the specific capacities of the battery corresponding to the 1st, 2nd, 5th, 10th, and 50th charge-discharge cycles. It can be Figure 4 seen that during the continuous charging and discharging process of the battery at 0.1C, at a current density of 20 mA g -1 the first-cycle discharge reversible specific capacity of the battery reached 273 mAh g -1 , and after 40 cycles at a current density of 20 mA g -1 there was still a reversible capacity of 140 mAh g -1 , showing good long-cycle ability and good battery capacity.

[0062] The cycle performance of the phenolic resin-based hard carbon at a rate of 0.1C is as Figure 5 shown. It can be Figure 5 seen that the battery has good capacity retention ability, with an initial efficiency of up to 82%, and good ICE.

[0063] The charge-discharge specific capacity of the battery prepared with the phenolic resin-based hard carbon obtained in Example 1 at a rate of 0.1C was 220 mAh g -1 .

[0064] The battery prepared with the phenolic resin-based hard carbon obtained in Comparative Example 1 is as Figure 6 shown. Its charge-discharge curve is similar to that of Example 2, but the charge-discharge specific capacities are both lower, approximately 195 mAh g -1 .

[0065] The battery prepared with the composite material obtained in Comparative Example 2 is as Figure 7 shown. It can be Figure 7 seen that its specific capacity is 200 mAh g-1 。

[0066] In summary, the specific capacities of the composite carbon materials prepared from bacteria-coated phenolic resins obtained in the embodiments of the present invention are much higher than those of Comparative Example 1 and Comparative Example 2, and have good capacity retention and good ICE.

[0067] Obviously, the above embodiments are merely examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. The obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing composite carbon materials using a biomass template method, characterized in that: The following steps are involved: The aqueous solution of bacteria is stirred and mixed with formaldehyde, and resorcinol, water and a catalyst are added, stirred for reaction, and a hydrothermal reaction is carried out in a high-pressure reactor. After solid-liquid separation, the solid is collected to obtain a precursor of phenolic resin-based hard carbon; The obtained phenolic resin-based hard carbon precursor is dried and carbonized under a protective atmosphere.

2. The method according to claim 1, characterized in that The bacteria are selected from one or more of Escherichia coli, Staphylococcus aureus and Bacillus subtilis.

3. The method according to claim 1, characterized in that The molar ratio of resorcinol to formaldehyde is 1:1-1:3; And / or, the concentration of formaldehyde is 30wt%-40wt%; And / or, the stirring reaction time is 15h-25h.

4. The method according to claim 1, characterized in that: The conditions of the hydrothermal reaction are: 80° C.-150° C. for 20 h-35 h.

5. The method according to claim 1, characterized in that The drying conditions are: 60°C-80°C for 12h-24h.

6. The method according to claim 1, characterized in that The carbonization conditions are: carbonization at 1100°C-1300°C for 2h-3.5h; And / or, the protective atmosphere is one or more of argon, helium, neon and nitrogen.

7. The composite carbon material prepared by the method according to any one of claims 1 to 6, characterized in that: The bacteria are coated on the surface of the phenolic resin.

8. The composite carbon material according to claim 7, characterized in that: The mass ratio of the bacteria to the phenolic resin is 1-3:

1.

9. Use of the composite carbon material according to claim 7 or 8 in the field of energy storage.

10. A sodium ion battery, characterized in that: The composite carbon material according to claim 7 or 8 is used as the negative electrode material.

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