Porous carbon material prepared by magnetic field oriented epitaxial induction and method and application thereof

Abstract

The invention belongs to the technical field of battery materials, and mainly relates to a porous carbon material prepared through magnetic field oriented epitaxial induction and a method and application thereof. The method comprises the following steps: pretreating a biomass material, degrading lignin, and activating cellulose to obtain hydroxylated cellulose; the hydroxylated cellulose and a magnetic metal solution are mixed for a coordination reaction, and magnetic metal coordinated cellulose is obtained; mixing and self-assembling the magnetic metal coordination cellulose and a carboxyl-containing organic matter solution, and applying a directional magnetic field to obtain a directional arrangement cellulose material; calcining the directionally arranged cellulose material for the first time under the condition of mixed gas; and calcining for the second time under an inert condition, and pickling to obtain the porous carbon material. Biomass cellulose is activated, coordinated with metal ions and then self-assembled with organic matter, a directional magnetic field is applied to enable metal active sites to be directionally arranged, and the bionic caterpillar-shaped porous carbon material with high mechanical strength and large specific surface area is obtained through sintering.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and mainly relates to a porous carbon material prepared by magnetic field-directed epitaxial induction, its preparation method and application. Background Art

[0002] With the development of new energy technologies, the requirements for battery materials are getting higher and higher. Among traditional battery anode materials, graphite anodes have advantages such as good electrical conductivity and stable cycling performance. However, their theoretical capacity (372 mAh / g) cannot meet the market demand for high energy density. Another material, elemental silicon, has a relatively high theoretical capacity (4200 mAh / g) and is considered to be the best candidate material for the next-generation lithium-ion battery anodes. However, elemental silicon undergoes a huge volume expansion during charge and discharge, leading to the formation of an unstable solid electrolyte interface (SEI) film, which increases the difficulty of its commercialization.

[0003] The mechanical strength, specific surface area, and electrical conductivity of porous carbon materials are considered to be the key factors for improving the electrochemical performance of silicon-carbon anodes. Among them, the mechanical strength of porous carbon materials ensures the integrity of the electrode structure, the specific surface area affects the loading amount of nanosilicon, and the electrical conductivity affects the electron transfer efficiency. Spherical porous carbon has a developed pore structure and a relatively high specific surface area. However, when spherical porous carbon is subjected to external forces such as impact, it cannot effectively absorb and disperse energy and is prone to fragmentation. Currently, the main preparation methods for spherical porous carbon are as follows: the template method and the spray drying method. The currently disclosed template method for preparing spherical porous carbon mainly uses the mesoporous SiO2 hard template method. The removal of the SiO2 hard template usually requires the introduction of strong bases, resulting in the fragmentation of the spherical porous carbon structure and a decrease in the specific surface area. The currently disclosed spray drying method for preparing spherical porous carbon mainly obtains it by spray drying a carbonaceous precursor and a surfactant. The spray drying method for preparing spherical porous carbon is difficult to precisely control its morphology and size, and problems such as irregular morphology, non-uniform size, and adhesion are likely to occur, resulting in a decrease in the specific surface area and electrical conductivity. In addition, the preparation of spherical porous materials by combining spray drying with the sacrificial template method, although solving some of the above problems, results in a relatively low specific surface area of the prepared spherical porous carbon material.

[0004] Therefore, there is an urgent need to develop a method for preparing carbon materials with high mechanical strength, large specific surface area, and good electrical conductivity. Summary of the Invention

[0005] To overcome the problems in the prior art, the present invention provides a method for preparing porous carbon materials by magnetic field-directed epitaxial induction. The obtained porous carbon materials are biomass-derived bionic caterpillar-like porous carbon materials with high mechanical strength, large specific surface area, and strong conductivity. After activating biomass cellulose and coordinating it with metal ions, self-assembling it with organic substances, and applying a directional magnetic field to align the metal active sites, a bionic caterpillar-like porous carbon material is finally obtained through sintering and pickling, ensuring the mechanical strength and specific surface area of the material.

[0006] In an embodiment of the present invention, a method for preparing porous carbon materials by magnetic field-directed epitaxial induction is provided, and the method includes the following steps:

[0007] S1. After pretreating the biomass material, lignin degradation and cellulose activation treatment are carried out to obtain hydroxylated cellulose;

[0008] S2. Mix the hydroxylated cellulose with a magnetic metal solution for a coordination reaction to obtain magnetic metal-coordinated cellulose;

[0009] S3. After mixing and self-assembling the magnetic metal-coordinated cellulose with a carboxyl-containing organic substance solution, apply a directional magnetic field to epitaxially induce the metal active sites to obtain a directionally arranged cellulose material;

[0010] S4. Calcinate the directionally arranged cellulose material for the first time under a mixed gas of inert gas and hydrocarbon compound; carry out the second calcination under an inert condition, and pickle it to obtain a bionic caterpillar-like porous carbon material.

[0011] As an alternative embodiment, the magnetic metal solution in step S2 is any one of soluble iron, cobalt, and nickel salt solutions, and the concentration of the magnetic metal solution is 0.1 - 0.5 mol / L.

[0012] As an alternative embodiment, during the coordination reaction in step S2, the temperature of the reaction system is 60 - 80 °C, the stirring rate is 100 - 200 rpm, and the reaction time is 1 - 4 h.

[0013] As an alternative embodiment, the carboxyl-containing organic substance in step S3 is any one of alkylated gelatin, alkylated rice bran protein, and spider silk protein, and the mass ratio of the magnetic metal-coordinated cellulose to the carboxyl-containing organic substance is 1:4 - 1:8; the temperature of the self-assembly process is 60 - 80 °C, the stirring rate is 100 - 200 rpm, and the self-assembly time is 1 - 3 h.

[0014] As an alternative embodiment, the directional magnetic field strength is 0.1 - 0.5 T, and the treatment time is 1 - 3 h.

[0015] As an alternative embodiment, in step S4, the volume ratio of the inert gas to the hydrocarbon compound in the mixed gas is 1:3 to 1:5. The inert gas is any one of helium, neon or argon, and the hydrocarbon compound is any one of acetylene or methane. The temperature of the first calcination process is 500 to 700 °C, the heating rate is 5 to 8 °C / min, and the heat preservation time is 1 to 3 h.

[0016] As an alternative embodiment, in the second calcination process of step S4, the calcination temperature is 700 to 900 °C under an inert atmosphere condition, the heating rate is 5 to 8 °C, and the heat preservation time is 2 to 4 h.

[0017] The pickling in step S4 is carried out in a hydrochloric acid solution. The concentration of the hydrochloric acid solution is 1 - 3 mol / L, and the pickling time is 1 - 3 h.

[0018] As an alternative embodiment, the pretreatment process in step S1 includes crushing, sieving, washing and drying. The lignin degradation and cellulose activation processes are treated with an alkaline solvent.

[0019] Based on the same inventive concept, an embodiment of the present invention also provides a porous carbon material prepared by the above method. The porous carbon material is in the shape of a bionic caterpillar, and the specific surface area is ≥2500 m 2 / g, the mechanical strength is ≥230 MPa, and the conductivity is ≥3.7 S / mm.

[0020] Based on the same inventive concept, an embodiment of the present invention also provides a lithium / sodium ion battery. The electrode precursor of the battery includes the above porous carbon material.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) The present invention combines magnetic field directional induction and self-assembly method to construct a bionic caterpillar porous carbon material. Under the action of the directional magnetic field, the magnetic metal exhibits an epitaxial induction mechanism, optimizing the distribution of the magnetic metal on the material surface, which is beneficial to the growth of the subsequent tentacle structure. The tentacle structure induced directionally has a uniform distribution and a large density, increasing the elastic modulus of the roughened area and improving the mechanical properties of the material. The tentacle structure significantly increases the specific surface area of the material, provides more active sites, reduces the potential barrier of electron transmission, and effectively improves the conductivity of the material. Reacting a carboxyl group-containing organic substance with cellulose in the reaction system and self-assembling does not require an additional template material, reducing the step of removing the template with strong alkali and avoiding damage to the tentacle structure caused by removing the template. Organic substances such as alkylated gelatin will undergo thermal decomposition at high temperatures, releasing small molecule gases, and the escape of these gases will form micropores inside the material, further increasing the specific surface area of the material.

[0023] (2) By varying the types of magnetic metal salts and constructing different coordination structures, the present invention can achieve the regulation of microporous structures. For example, the coordination modes of hydroxycellulose with Co2+ are monodentate coordination and multidentate coordination. Monodentate coordination means that one hydroxyl group coordinates with one Co2+, which is conducive to the formation of a uniform pore structure, while multidentate coordination means that multiple hydroxyl groups coordinate with one Co2+, which is conducive to the formation of multiple interconnected channels and is beneficial to electrolyte penetration. By taking advantage of the different magnetic permeabilities of different magnetic metals, the tentacle structure can be regulated.

[0024] (3) The porous carbon material prepared by magnetic field-directed epitaxial induction in the present invention is a biomass-derived bionic caterpillar-like porous carbon material, with a specific surface area of up to 3652 m 2 / g, a maximum mechanical strength of up to 342 MPa, and a conductivity of up to 3.25 S / cm. When used as a precursor for vapor deposition of silane / acetylene to prepare a silicon-carbon composite material for the negative electrode of a lithium-ion battery, at a current density of 0.1 A / g, the first reversible capacity of the lithium-ion half-cell is 2478 mAh / g. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 SEM image of the bionic caterpillar-like porous carbon material prepared in Example 1 of the present invention;

[0027] Figure 2 BET image of the bionic caterpillar-like porous carbon material prepared in Example 1 of the present invention;

[0028] Figure 3 Reversible capacity graph of the BCPC-Co-800 / Si / C negative electrode prepared in Example 1 of the present invention at 0.1 A / g;

[0029] Figure 4 SEM image of the bionic caterpillar-like porous carbon material prepared in Example 4 of the present invention. Detailed Description of the Embodiments

[0030] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively and meticulously in conjunction with the accompanying drawings of the specification and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0031] Unless otherwise defined, all technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of the present invention.

[0032] Unless otherwise specified, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0033] A method for preparing porous carbon materials by magnetic field-directed epitaxial induction provided by the present invention includes the following steps:

[0034] S1. After the biomass material is pretreated, lignin degradation and cellulose activation treatment are carried out to obtain hydroxylated cellulose. The biomass material includes one or more of moso bamboo, rice husk, or straw. In this process, the pretreatment process includes crushing, sieving, washing, and drying. The biomass material is ball-milled in a ball mill at a rotation speed of 400 - 600 rpm for 2 - 6 h, then sieved with a 300 - 500 mesh sieve to obtain biomass particles with a particle size range of 10 - 50 μm, then washed with hydrochloric acid with a concentration of 1 - 3 mol / L and deionized water, and finally dried in an oven. More preferably, the rotation speed during the ball-milling process is 500 rpm, the ball-milling time is 4 h; the sieving is carried out with a 500 mesh sieve to screen out biomass particles with a particle size of 20 - 30 μm, and the washing process uses hydrochloric acid with a concentration of 2 mol / L for washing for 2 h to remove technical impurities and surface dust in the biomass material.

[0035] The pretreated biomass material is placed in an alkaline solution for lignin dissolution and cellulose activation, and vacuum dried to obtain hydroxylated cellulose. The alkaline solution is any one of NaOH, KOH, and Na2CO3 with a concentration of 5 - 8 mol / L, the dissolution temperature is 20 - 40 °C, the stirring rate is 100 - 200 rpm, and the dissolution time is 1 - 3 h. More preferably, 6 mol / L NaOH is used as the dissolution reagent, and it is stirred and dissolved at a temperature of 30 °C and a stirring rate of 150 rpm for 2 h. The hydroxylated cellulose obtained in this process contains hydroxyl functional groups, and the hydroxyl groups can act as coordination sites to undergo coordination reactions with metal ions.

[0036] S2. Mix the hydroxylated cellulose with a magnetic metal solution for a coordination reaction to obtain magnetic metal coordinated cellulose. In this process, the magnetic metal solution is any one of soluble iron, cobalt, and nickel salt solutions, and its concentration is 0.1 - 0.5 mol / L. During this coordination reaction process, the system temperature is maintained at 60 - 80 °C, the stirring rate is 100 - 200 rpm, and the treatment time is 1 - 4 h. More preferably, the magnetic metal solution is a cobalt salt solution with a concentration of 0.2 mol / L, and it is treated for 2 h at a stirring rate of 150 rpm at 60 °C. The type and concentration of the magnetic metal solution will affect the formation of the subsequent tentacle structure. In the present invention, by changing the type of the magnetic metal solution, different metal coordination bonds are constructed to realize the regulation of the microporous structure and the tentacle structure.

[0037] S3. After mixing and self - assembling the magnetic metal coordinated cellulose with a carboxyl - containing organic solution, apply a directional magnetic field to induce the epitaxy of metal active sites to obtain an oriented arrangement of cellulose materials. In this process, the carboxyl - containing organic is any one of alkylated gelatin, alkylated rice bran protein, and silk fibroin. The mass ratio of the magnetic metal coordinated cellulose to the carboxyl - containing organic is 1:4 - 1:8, and the solid - liquid ratio of the magnetic metal coordinated cellulose to the organic solution is 1 - 5 g:100 ml. The temperature of the self - assembly reaction is 60 - 80 °C, the stirring rate is 100 - 200 rpm, and the time is 1 - 3 h. More preferably, the mass ratio of the magnetic metal coordinated cellulose to alkylated gelatin is 1:6, and they are mixed according to a solid - liquid ratio of 3 g:100 ml, and self - assembled for 2 h at a temperature of 80 °C and a stirring rate of 100 rpm. The intensity of the applied magnetic field is 0.1 - 0.5 T, and the treatment time is 1 - 3 h. Preferably, the directional magnetic field intensity is 0.3 T, and the treatment time is 2 h.

[0038] During the above self - assembly and magnetic field induction processes, the carboxyl group (-COOH) on the alkylated gelatin molecular chain will undergo an esterification reaction with the hydroxyl group (-OH) of the hydroxylated cellulose. By introducing an alkyl chain, the hydrophobicity and intermolecular interaction of alkylated gelatin are changed. The introduction of the alkyl chain will enhance the hydrophobic interaction between gelatin and cellulose, thereby promoting the self - assembly process to form spherical cellulose - based aggregates. Under the action of the directional magnetic field, the magnetic moment of the magnetic metal will tend to align with the external magnetic field direction. This alignment of the magnetic moment can guide the magnetic metal to align along a specific direction, thus realizing directional epitaxy. In addition, during the epitaxial growth process, the magnetic interaction between magnetic metals enhances the magnetic anisotropy of the magnetic metals, avoids the aggregation of magnetic metals, and makes the magnetic metals more inclined to be oriented along the magnetic field direction.

[0039] S4. The aligned cellulose material is calcined for the first time under a mixed gas of an inert gas and a hydrocarbon compound; then it is calcined for the second time under an inert condition to obtain a bionic caterpillar-shaped porous carbon material. During the first calcination, the volume ratio of the inert gas to the hydrocarbon compound in the mixed gas is 1:3 to 1:5. The inert gas is any one of helium, neon or argon, and the hydrocarbon compound is any one of acetylene or methane; the temperature during the first calcination process is 500 - 700 °C, the heating rate is 5 - 8 °C / min, and the heat preservation time is 1 - 3 h. More preferably, the carbon-containing gas used in the first calcination is acetylene gas, the mixed gas is an inert protective gas and acetylene configured in a ratio of 1:4, the temperature is 600 °C, the heating rate is 5 °C / min, and the heat preservation time is 1 h. During the second calcination process, the calcination temperature is 700 - 900 °C under an inert atmosphere condition, the heating rate is 5 - 8 °C, and the heat preservation time is 2 - 4 h. More preferably, the second calcination temperature is 800 °C, the heating rate is 5 °C / min, and the heat preservation time is 2 h. The pickling is carried out in a hydrochloric acid solution, the concentration of the hydrochloric acid solution is 1 - 3 mol / L, and the pickling time is 1 - 3 h. More preferably, the concentration of the hydrochloric acid solution is 2 mol / L, and the pickling time is 2 h.

[0040] In the first calcination, the epitaxial magnetic metal precursor on the composite is reduced to metal nanoparticles by the carbon-containing gas in the mixed gas. The metal nanoparticles act as catalysts, which can adsorb the carbon source and decompose it to generate active carbon atoms. These carbon atoms then migrate and rearrange on the surface of the catalyst serving as the crystal nucleus to form a tentacle structure, and grow uniformly on the material surface according to the orientation arrangement under the influence of the magnetic field.

[0041] A porous carbon material is prepared according to the above preparation method. The porous carbon material is in the shape of a bionic caterpillar, with a specific surface area ≥ 2700 m 2 / g, a mechanical strength ≥ 230 MPa, and a conductivity ≥ 2.7 S / cm. This material can be used to prepare the negative electrode material of a lithium-ion or sodium-ion battery.

[0042] The following is further illustrated with specific examples.

[0043] Example 1

[0044] This example provides a preparation method for preparing a bionic caterpillar-shaped porous carbon material by magnetic field-directed epitaxial induction:

[0045] S1. Grind the moso bamboo material at a rotational speed of 500 rpm for 4 h, classify it through a 500-mesh sieve to make the particle size range of the moso bamboo 20 - 30 μm; wash the surface dust with deionized water, then stir and wash with 2 mol / L hydrochloric acid for 2 h to remove the metal impurities in the moso bamboo material, filter and place it in an incubator for drying; add the above pretreated biomass material into 6 mol / L sodium hydroxide solution, stir at 150 rpm at 30 °C for 2 h, then wash and dry to obtain hydroxylated cellulose.

[0046] S2. Add the above hydroxylated cellulose into 0.2 mol / L cobalt chloride solution, the temperature of the metal coordination reaction system is 60 °C, the stirring rate is 150 rpm, and the treatment time is 2 h. Wash and dry to obtain magnetic metal coordination cellulose.

[0047] S3. Mix magnetic metal coordination cellulose and alkylated gelatin solution with a mass ratio of 1:6 at a liquid-solid ratio of 3 g:100 ml, stir at 100 rpm at 80 °C for 2 h to obtain spherical cellulose-based aggregates; apply a directional magnetic field of 0.3 T to the solution and directionally induce for 2 h to obtain spherical cellulose-based aggregates with magnetic metal epitaxial directional arrangement.

[0048] S4. The obtained product is first calcined at a calcination temperature of 600 °C and a heating rate of 5 °C / min in an atmosphere with a ratio of Ar to acetylene of 1:4 for 1 h to induce the formation of tentacle structures; the above product is secondarily calcined under Ar at a calcination temperature of 800 °C, a heating rate of 5 °C / min, and a holding time of 2 h, and pickled in 2 mol / L hydrochloric acid solution for 2 h to prepare biomimetic caterpillar-like porous carbon (BCPC-Co-800-0.3).

[0049] Example 2

[0050] This example provides a preparation method for preparing biomimetic caterpillar-like porous carbon materials by magnetic field-directed epitaxial induction:

[0051] S1. Grind the moso bamboo material at a rotational speed of 500 rpm for 4 h, classify it through a 500-mesh sieve to make the particle size range of the moso bamboo 20 - 30 μm; wash the surface dust with deionized water, then stir and wash with 2 mol / L hydrochloric acid for 2 h to remove the metal impurities in the moso bamboo material, filter and place it in an incubator for drying; add the above pretreated biomass material into 6 mol / L sodium hydroxide solution, stir at 150 rpm at 30 °C for 2 h, then wash and dry to obtain hydroxylated cellulose;

[0052] S2. Add the above hydroxylated cellulose into 0.2 mol / L ferric chloride solution, the temperature of the metal coordination reaction system is 60 °C, the stirring rate is 150 rpm, and the treatment time is 2 h. Wash and dry to obtain magnetic metal coordination cellulose.

[0053] S3. Mix magnetic metal-coordinated cellulose with an alkylated gelatin at a mass ratio of 1:6 at a liquid-solid ratio of 3 g:100 ml, stir at 100 rpm for 2 h at 80 °C to obtain spherical cellulose-based aggregates; apply a directional magnetic field of 0.3 T to the solution and directionally induce for 2 h to obtain spherical cellulose-based aggregates with directionally arranged magnetic metal epitaxy;

[0054] S4. The obtained product is first calcined at a calcination temperature of 600 °C and a heating rate of 5 °C / min in an atmosphere with an Ar to acetylene ratio of 1:4 for 1 h to induce the formation of tentacle structures; the above product is secondarily calcined at a calcination temperature of 800 °C, a heating rate of 5 °C / min, and a holding time of 2 h under Ar, and pickled in a 2 mol / L hydrochloric acid solution for 2 h to prepare a biomimetic caterpillar-shaped porous carbon (BCPC-Fe-800-0.3).

[0055] Example 3

[0056] This example provides a preparation method for preparing a biomimetic caterpillar-shaped porous carbon material by magnetic field-directed epitaxial induction:

[0057] S1. Grind bamboo materials at a rotation speed of 500 rpm for 4 h to break them, classify them through a 500-mesh sieve so that the particle size range of the bamboo is 20 - 30 μm; wash the surface dust with deionized water, then stir and wash with 2 mol / L hydrochloric acid for 2 h to remove metal impurities from the bamboo materials, filter and place them in an incubator for drying; add the above pretreated biomass materials to a 6 mol / L sodium hydroxide solution, stir at 150 rpm for 2 h at 30 °C, then wash and dry to obtain hydroxylated cellulose;

[0058] S2. Add the above hydroxylated cellulose to a 0.2 mol / L nickel chloride solution, the temperature of the metal coordination reaction system is 60 °C, the stirring rate is 150 rpm, and the treatment time is 2 h, then wash and dry to obtain magnetic metal-coordinated cellulose.

[0059] S3. Mix magnetic metal-coordinated cellulose with an alkylated gelatin solution at a mass ratio of 1:6 at a liquid-solid ratio of 3 g:100 ml, stir at 100 rpm for 2 h at 80 °C to obtain spherical cellulose-based aggregates; apply a directional magnetic field of 0.3 T to the solution and directionally induce for 2 h to obtain spherical cellulose-based aggregates with directionally arranged magnetic metal epitaxy;

[0060] S4. The obtained product is first calcined in an atmosphere with an Ar to acetylene ratio of 1:4 at a calcination temperature of 600 °C and a heating rate of 5 °C / min for 1 h to induce the formation of tentacle structures. The above product is then calcined under Ar at a calcination temperature of 800 °C, a heating rate of 5 °C / min, and a holding time of 2 h, and pickled in a 2 mol / L hydrochloric acid solution for 2 h to prepare biomimetic caterpillar-like porous carbon (BCPC-Ni-800-0.3).

[0061] Example 4

[0062] This example provides a preparation method for biomimetic caterpillar-like porous carbon materials by magnetic field-directed epitaxial induction:

[0063] S1. The bamboo material is ball-milled at a speed of 500 rpm for 4 h and crushed, and classified through a 500-mesh sieve to make the bamboo particle size range from 20 to 30 μm. The surface dust is washed away with deionized water, and then the metal impurities of the bamboo material are removed by stirring and washing with 2 mol / L hydrochloric acid for 2 h, filtered and placed in an incubator for drying. The above pretreated biomass material is added to a 6 mol / L sodium hydroxide solution and stirred at 30 °C at 150 rpm for 2 h, then washed and dried to obtain hydroxylated cellulose.

[0064] S2. The above hydroxylated cellulose is added to a 0.2 mol / L cobalt chloride solution, the temperature of the metal coordination reaction system is 60 °C, the stirring rate is 150 rpm, and the treatment time is 2 h. After washing and drying, magnetic metal coordination cellulose is obtained.

[0065] S3. The magnetic metal coordination cellulose and the alkylated gelatin solution with a mass ratio of 1:6 are mixed at a liquid-solid ratio of 3 g:100 ml, stirred at 80 °C at 100 rpm for 2 h to obtain spherical cellulose-based aggregates. A directional magnetic field of 0.1 T is applied to the solution, and directionally induced for 2 h to obtain spherical cellulose-based aggregates with magnetic metal epitaxial directional arrangement.

[0066] S4. The obtained product is first calcined in an atmosphere with an Ar to acetylene ratio of 1:4 at a calcination temperature of 600 °C and a heating rate of 5 °C / min for 1 h to induce the formation of tentacle structures. The above product is then calcined under Ar at a calcination temperature of 800 °C, a heating rate of 5 °C / min, and a holding time of 2 h, and pickled in a 2 mol / L hydrochloric acid solution for 2 h to prepare biomimetic caterpillar-like porous carbon (BCPC-Co-800-0.1).

[0067] Example 5

[0068] This example provides a preparation method for biomimetic caterpillar-like porous carbon materials by magnetic field-directed epitaxial induction:

[0069] S1. Grind the moso bamboo material at a rotational speed of 500 rpm for 4 h to break it, classify it through a 500-mesh sieve so that the particle size range of the moso bamboo is 20 - 30 μm; wash away the surface dust with deionized water, then stir and wash with 2 mol / L hydrochloric acid for 2 h to remove the metal impurities in the moso bamboo material, filter and place it in an incubator for drying; add the above pretreated biomass material into 6 mol / L sodium hydroxide solution, stir at 150 rpm at 30 °C for 2 h, then wash and dry to obtain hydroxylated cellulose;

[0070] S2. Add the above hydroxylated cellulose into 0.2 mol / L cobalt chloride solution, the temperature of the metal coordination reaction system is 60 °C, the stirring rate is 150 rpm, and the treatment time is 2 h. Wash and dry to obtain magnetic metal coordination cellulose.

[0071] S3. Mix magnetic metal coordination cellulose and alkylated gelatin solution with a mass ratio of 1:6 at a liquid-solid ratio of 3 g:100 ml, stir at 100 rpm at 80 °C for 2 h to obtain spherical cellulose-based aggregates; apply a directional magnetic field of 0.5 T to the solution and directionally induce for 2 h to obtain spherical cellulose-based aggregates with magnetic metal epitaxial directional arrangement;

[0072] S4. The obtained product is first calcined in an atmosphere with an Ar to acetylene ratio of 1:4 at a calcination temperature of 600 °C and a heating rate of 5 °C / min for 1 h to induce the formation of tentacle structures; the above product is secondarily calcined under Ar at a calcination temperature of 800 °C, a heating rate of 5 °C / min, and a holding time of 2 h, and pickled in 2 mol / L hydrochloric acid solution for 2 h to prepare biomimetic caterpillar-like porous carbon (BCPC-Co-800-0.5).

[0073] Comparative Example 1

[0074] This example provides a preparation method for preparing biomimetic caterpillar-like porous carbon materials by magnetic field-directed epitaxial induction:

[0075] S1. Grind the moso bamboo material at a rotational speed of 500 rpm for 4 h to break it, classify it through a 500-mesh sieve so that the particle size range of the moso bamboo is 20 - 30 μm; wash away the surface dust with deionized water, then stir and wash with 2 mol / L hydrochloric acid for 2 h to remove the metal impurities in the moso bamboo material, filter and place it in an incubator for drying; add the above pretreated biomass material into 6 mol / L sodium hydroxide solution, stir at 150 rpm at 30 °C for 2 h, then wash and dry to obtain hydroxylated cellulose;

[0076] S2. Mix hydroxylated cellulose and alkylated gelatin solution with a mass ratio of 1:6 at a liquid-to-solid ratio of 3 g:100 ml, stir at 100 rpm for 2 h at 80 °C to obtain spherical cellulose-based aggregates; apply a directional magnetic field of 0.3 T to the solution and directionally induce for 2 h to obtain spherical cellulose-based aggregates with magnetically metal epitaxial alignment;

[0077] S3. The obtained product is first calcined at a calcination temperature of 600 °C and a heating rate of 5 °C / min in an atmosphere with an Ar-to-acetylene ratio of 1:4 for 1 h to induce the formation of tentacle structures; the above product is secondarily calcined at a calcination temperature of 800 °C and a heating rate of 5 °C / min under Ar for 2 h of holding time, and pickled in 2 mol / L hydrochloric acid solution for 2 h to prepare biomimetic caterpillar-like porous carbon (PC-800-0.3).

[0078] Comparative Example 2

[0079] This example provides a preparation method for preparing biomimetic caterpillar-like porous carbon materials by magnetic field-directed epitaxial induction:

[0080] S1. Grind bamboo materials at a rotational speed of 500 rpm for 4 h to break them, classify them through a 500-mesh sieve so that the particle size range of bamboo is 20 - 30 μm; wash the surface dust with deionized water, then stir and wash with 2 mol / L hydrochloric acid for 2 h to remove metal impurities in the bamboo materials, filter and place them in an incubator for drying; add the above pretreated biomass materials to 6 mol / L sodium hydroxide solution, stir at 150 rpm for 2 h at 30 °C, then wash and dry to obtain hydroxylated cellulose;

[0081] S2. Add the above hydroxylated cellulose to 0.2 mol / L cobalt chloride solution, the temperature of the metal coordination reaction system is 60 °C, the stirring rate is 150 rpm, and the treatment time is 2 h. Apply a directional magnetic field of 0.3 T to the solution and directionally induce for 2 h to obtain spherical cellulose-based aggregates with magnetically metal epitaxial alignment;

[0082] S3. The obtained product is first calcined at a calcination temperature of 600 °C and a heating rate of 5 °C / min in an atmosphere with an Ar-to-acetylene ratio of 1:4 for 1 h to induce the formation of tentacle structures; the above product is secondarily calcined at a calcination temperature of 800 °C and a heating rate of 5 °C / min under Ar for 2 h of holding time, and pickled in 2 mol / L hydrochloric acid solution for 2 h to prepare biomimetic caterpillar-like porous carbon (C-Co-800-0.3).

[0083] Comparative Example 3

[0084] This example provides a preparation method for preparing biomimetic caterpillar-like porous carbon materials by magnetic field-directed epitaxial induction:

[0085] S1. Grind the moso bamboo material at a rotational speed of 500 rpm for 4 h to break it, and classify it through a 500-mesh sieve so that the particle size range of the moso bamboo is 20 - 30 μm; wash the surface dust with deionized water, then stir and wash with 2 mol / L hydrochloric acid for 2 h to remove the metal impurities in the moso bamboo material, filter and place it in an incubator for drying; add the above pretreated biomass material to 6 mol / L sodium hydroxide solution, stir at 150 rpm at 30 °C for 2 h, then wash and dry to obtain hydroxylated cellulose;

[0086] S2. Add the above hydroxylated cellulose to 0.2 mol / L cobalt chloride solution, the temperature of the metal coordination reaction system is 60 °C, the stirring rate is 150 rpm, and the treatment time is 2 h. Wash and dry to obtain magnetic metal coordination cellulose.

[0087] S3. Mix magnetic metal coordination cellulose and alkylated gelatin solution with a mass ratio of 1:6 at a liquid-solid ratio of 3 g:100 ml, stir at 100 rpm at 80 °C for 2 h to obtain spherical cellulose-based aggregates; apply a directional magnetic field of 0.3 T to the solution and directionally induce for 2 h to obtain spherical cellulose-based aggregates with magnetic metal epitaxial directional arrangement;

[0088] S4. The obtained product is secondarily calcined under Ar at a calcination temperature of 800 °C, a heating rate of 5 °C / min, and a holding time of 2 h, and pickled in 2 mol / L hydrochloric acid solution for 2 h to prepare a biomimetic caterpillar-shaped porous carbon material (PC-Co-800-0.3).

[0089] Performance test:

[0090] Perform scanning electron microscopy tests on the porous carbon materials obtained in the examples. Taking Example 1 and Example 4 as actual examples, specifically as Figure 1 and Figure 2 shown. Its specific structure is biomimetic caterpillar-shaped.

[0091] Perform nitrogen adsorption / desorption tests on the materials of the examples and comparative examples to determine their specific surface areas and pore structures, perform tensile strength tests to determine their mechanical properties, and perform four-probe tests to determine their electrical conductivities. The specific test results are shown in Table 1 and Figure 3 shown.

[0092] To evaluate its feasibility as a carbon-silicon anode material, porous carbon materials were deposited with silane / acetylene by chemical vapor deposition for 1 h to prepare a silicon-carbon anode material (BCPC-Co-800-0.3 / Si / C) with a silicon content of 56%. Constant current charge-discharge tests were carried out to evaluate its electrochemical performance. The specific preparation method is as follows: a negative electrode slurry was prepared from the composite material, carbon black and CMC binder in a ratio of 8:1:1, and then it was coated on a copper foil with a spatula. It was dried in vacuum at 60 °C for 24 h, cut into discs with a diameter of 18 mm, and assembled into CR2032 batteries. The silicon deposition amount and the first reversible capacity at a current density of 0.1 A / g were measured. The test results are shown in Table 1 and Figure 4 as follows.

[0093] Table 1 Performance data of porous materials in the examples and comparative examples

[0094]

[0095] By comparing Example 1, Example 2 and Example 3, since different magnetic metal materials have different magnetic moments and respond differently to the magnetic field under the same magnetic field strength, the physico-chemical properties of the materials are affected. When the magnetic metal solution is cobalt hydroxide, it is the best magnetic metal solution for the preparation process of the present invention.

[0096] By comparing Example 1 with Comparative Example 1 (without adding a magnetic metal solution), 2 (without adding a carboxyl-containing organic substance), and 3 (without acetylene induction during the first calcination process), metal coordination cannot be carried out in Comparative Example 1, there is no crystal nucleus as a catalyst, and the formation of tentacle structures cannot be induced, resulting in a decrease in mechanical strength; in Comparative Example 2, self-assembly is not carried out using a specific organic substance, only dispersed metal-coordinated cellulose is formed, the formed microporous structure is less, the specific surface area of the material is reduced, and at the same time, a spherical-like structure cannot be formed, and the mechanical strength is also reduced; in Comparative Example 3, no acetylene induction is used, and tentacle structures cannot be formed, and the specific surface area cannot be effectively increased. Therefore, in the present invention, biomass cellulose is first activated and coordinated with metal ions, then reacted with a carboxyl-containing organic substance and self-assembled, and a directional magnetic field is applied to make the metal active sites arranged directionally, and finally a bionic caterpillar-like porous carbon material is obtained through multiple sinterings, which not only ensures the mechanical strength and specific surface area of the material, but also improves the electrical performance of the corresponding battery.

[0097] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the art to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for preparing porous carbon materials by magnetic field-directed epitaxial induction, characterized in that the method comprises the following steps: S1. After the biomass material is pretreated, lignin degradation and cellulose activation treatment are carried out to obtain hydroxylated cellulose; S2. The hydroxylated cellulose is mixed with a magnetic metal solution for a coordination reaction to obtain magnetic metal-coordinated cellulose; S3. After the magnetic metal-coordinated cellulose is self-assembled with a carboxyl-containing organic solution, a directional magnetic field is applied to epitaxially induce metal active sites to obtain a directionally arranged cellulose material; S4. The directionally arranged cellulose material is first calcined under a mixed gas of an inert gas and a hydrocarbon compound; second calcination is carried out under an inert condition, and acid washing is carried out to obtain a biomimetic caterpillar-shaped porous carbon material.

2. The method for preparing porous carbon materials by magnetic field-directed epitaxial induction according to claim 1, characterized in that in step S2, the magnetic metal solution is any one of soluble iron, cobalt, and nickel salt solutions, and the concentration of the magnetic metal solution is 0.1-0.5 mol / L.

3. The method for preparing porous carbon materials by magnetic field-directed epitaxial induction according to claim 1, characterized in that during the coordination reaction in step S2, the temperature of the reaction system is 60-80 °C, the stirring rate is 100-200 rpm, and the reaction time is 1-4 h.

4. The method for preparing porous carbon materials by magnetic field-directed epitaxial induction according to claim 1, characterized in that in step S3, the carboxyl-containing organic matter is any one of alkylated gelatin, alkylated rice bran protein, and spider silk protein, and the mass ratio of the magnetic metal-coordinated cellulose to the carboxyl-containing organic matter is 1:4-1:8; the temperature during the self-assembly process is 60-80 °C, the stirring rate is 100-200 rpm, and the self-assembly time is 1-3 h.

5. The method for preparing porous carbon materials by magnetic field-directed epitaxial induction according to claim 1, characterized in that the directional magnetic field intensity is 0.1-0.5 T, and the treatment time is 1-3 h.

6. The method for preparing porous carbon materials by magnetic field-directed epitaxial induction according to claim 1, characterized in that in step S4, the volume ratio of the inert gas to the hydrocarbon compound in the mixed gas is 1:3-1:5, the inert gas is any one of helium, neon, or argon, and the hydrocarbon compound is any one of acetylene or methane; the temperature during the first calcination process is 500-700 °C, the heating rate is 5-8 °C / min, and the heat preservation time is 1-3 h; during the second calcination process, the calcination temperature is 700-900 °C under an inert atmosphere condition, the heating rate is 5-8 °C, and the heat preservation time is 2-4 h; 7. The method for preparing porous carbon materials by magnetic field-directed epitaxial induction according to claim 1, characterized in that the pickling in step S4 is carried out in a hydrochloric acid solution, the concentration of the hydrochloric acid solution is 1-3 mol / L, and the pickling time is 1-3 h.

8. The method for preparing porous carbon materials by magnetic field-directed epitaxial induction according to claim 1, characterized in that the pretreatment process in step S1 includes crushing, sieving, washing and drying; the lignin degradation and cellulose activation processes are treated with an alkaline solvent.

9. The porous carbon material obtained by the method according to any one of claims 1 to 8, characterized in that the porous carbon material is in the shape of a bionic caterpillar, the specific surface area ≥ 2700 m 2 / g, the mechanical strength ≥ 230 MPa, and the conductivity ≥ 2.7 S / cm.

10. A lithium / sodium ion battery, characterized in that the electrode precursor of the battery includes the porous carbon material according to claim 9.

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