Core-shell porous carbon microspheres, silicon-carbon anode material, and preparation method therefor

Abstract

Provided in the present application are core-shell porous carbon microspheres, a silicon-carbon anode material, and a preparation method therefor. The preparation method for the core-shell porous carbon microspheres comprises: preparing a first resin mixture into a first resin sphere dispersion liquid, wherein the first resin mixture comprises a first resin, the first resin has a first carbon residue rate, and the first resin sphere dispersion liquid comprises microsphere-shaped first resin spheres; coating a surface of the first resin spheres with at least one layer of resin coating to form core-shell resin spheres, wherein each layer of the resin coating comprises a coating resin, a carbon residue rate of the coating resin is greater than the carbon residue rate of the first resin, and when there are more than one layers of the resin coating, the carbon residue rate of the coating resin sequentially increases in a direction away from the surface of the first resin spheres; and performing a carbonization treatment on the core-shell resin spheres, and then performing an activation treatment to form the core-shell porous carbon microspheres. The method can effectively alleviate the volume expansion of the silicon-carbon material and improve the cycling stability and rate performance of the silicon-carbon material.

Description

Core-shell porous carbon microspheres, silicon-carbon anode materials and their preparation methods Technical Field

[0001] This application relates to the field of lithium-ion batteries, and in particular to a core-shell porous carbon microsphere, a silicon-carbon anode material, and a method for preparing the same. Background Technology

[0002] Lithium-ion batteries have gained widespread application due to their high energy density and rapid charge / discharge characteristics, appearing in large-scale energy storage, electric vehicles, and various electronic products. However, with the development of various fields, the demand for power energy density is increasing day by day. Existing lithium-ion battery systems are unable to meet the current market's demand for high energy density and long cycle life, necessitating the exploration and development of anode materials with high specific capacity.

[0003] Silicon anode materials mainly form Li with lithium. 12 Si7, Li 13 Si4, Li7Si3, Li 22 Various alloy phases, including Si5, are present, with Li having the highest lithium content. 22 Si5, a silicon-lithium alloy, allows one silicon atom to alloy with 4.4 lithium atoms, resulting in a theoretical specific capacity of up to 4200 mAh / g, making it the lithium-ion battery anode material with the highest known specific capacity. Furthermore, silicon-based anode materials exhibit a low lithium insertion / extraction potential (~0.4V vs. Li / Li+), preventing lithium plating during charging. Additionally, silicon has low reactivity with electrolytes, is abundant in the Earth's crust, and is inexpensive, making it an ideal choice for next-generation lithium-ion battery anode materials. However, when elemental silicon is used as a lithium-ion battery anode material, the lithiation / delithiation process involves significant volume expansion. This volume expansion directly impacts the extremely low charge / discharge efficiency and cycle stability of elemental silicon, making it unsuitable for practical commercial applications.

[0004] To address the volume expansion during the charge-discharge process of elemental silicon, researchers have developed silicon-based composite materials by combining them with other materials. These composites offer advantages such as good stability, minimal volume change, and excellent conductivity. Currently, silicon-based composites typically store silicon using a porous carbon framework. This process involves first preparing porous carbon particles, then introducing silane gas into the pores of these particles. High-temperature pyrolysis causes the gas to precipitate as silicon nanoparticles, which are then dispersed within the pores of the porous carbon. This method allows for control over the molecular scale of silicon nanoparticles, resulting in a product with good morphology. Furthermore, the deposited silicon-carbon anode material exhibits uniform composition and a relatively dense structure. The volume expansion is buffered by the internal pores of the porous carbon, resulting in a low expansion rate and excellent cycle life.

[0005] Porous carbon microspheres possess unique performance advantages in the preparation of silicon-carbon anode materials due to their smooth surface, regular shape, good chemical stability, and high mechanical properties. Furthermore, they can improve the uniformity and efficiency of silane deposition, giving silicon-carbon anodes based on porous carbon microspheres performance characteristics that non-spherical microspheres cannot possess, such as improved compaction performance and high / low temperature resistance. Based on their internal structure, porous carbon microspheres can be classified into solid microspheres, hollow microspheres, and core-shell microspheres, all of which show promising applications in silicon-carbon anodes. Hollow microspheres and core-shell microspheres, in particular, not only possess the performance advantages of porous carbon microspheres but also, due to their unique buffer space, can solve the problem of volume expansion, thus avoiding degradation issues during charging / discharging.

[0006] Therefore, further research is needed on methods for forming core-shell porous carbon microspheres. Summary of the Invention

[0007] This application provides a method for creating core-shell porous carbon microspheres and applying it to silicon-carbon materials, which can effectively alleviate the volume expansion of silicon-carbon materials and improve their cycle stability and rate performance.

[0008] This application provides a method for preparing core-shell porous carbon microspheres, including:

[0009] A first resin mixture is prepared into a first resin ball dispersion, the first resin mixture comprising a first resin having a first char residue, and the first resin ball dispersion comprising microspheres of the first resin ball; at least one layer of resin coating is coated on the surface of the first resin ball to form a core-shell resin ball, each layer of the resin coating comprising coating resin, the char residue of the coating resin being greater than the char residue of the first resin, and when there is more than one layer of resin coating, the char residue of the coating resin increasing sequentially in the direction away from the surface of the first resin ball; the core-shell resin ball is carbonized and then activated to form a core-shell porous carbon microsphere.

[0010] In some embodiments of this application, the method for preparing the first resin ball dispersion includes: adding a first organic solvent and water to the first resin mixture to adjust the solid content of the first resin mixture from 50-100% to 30-60%, wherein the mass ratio of the first organic solvent and water to the first resin is in the range of (1-5):1, and the mass ratio of the first organic solvent to water is 1:1 to 1:10; adding a first emulsifier, a second organic solvent, and water until the solid content of the first resin mixture is reduced to 5-40%, wherein the mass percentage of the first emulsifier, the second organic solvent, and water to the first resin is in the range of (1-10):(1-15):1, and the mass ratio of the second organic solvent to water is 1:1 to 1:10; and reacting the first resin mixture at a temperature of 60-200°C for a first set time to obtain the first resin ball dispersion.

[0011] In some embodiments of this application, the first organic solvent and the second organic solvent respectively include at least one of benzene, toluene, xylene, pentane, hexane, octane, cyclohexane, cyclohexanone, methylcyclohexanone, chlorobenzene, dichlorobenzene, dichloromethane, methanol, ethanol, isopropanol, diethyl ether, propylene oxide, methyl acetate, ethyl acetate, propyl acetate, acetone, methyl butyl ketone, methyl isobutyl ketone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, acetonitrile, and pyridine; the first emulsifier includes one or more of the following: propylene oxide and ethylene oxide polymer F127, polyvinylpyrrolidone (PVP), sodium dodecyl sulfonate, hexadecyltrimethylammonium bromide (CTAB), alkoxylated fatty alcohol F86, polyoxyethylene ether F108, and polyvinyl alcohol.

[0012] In some embodiments of this application, the first resin mixture further includes at least one of a template agent and a fast ion conductor, the char residue of the first resin is between 20% and 45%, and the weight percentages of the first resin, the template agent, and the fast ion conductor are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the weight of the first resin, and the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the weight of the first resin.

[0013] In some embodiments of this application, the at least one resin coating comprises a second resin mixture or a third resin mixture, wherein the second resin mixture comprises a second resin, the third resin mixture comprises a third resin, the char residue of the second resin is greater than that of the first resin, and the char residue of the third resin is greater than that of the first resin.

[0014] In some embodiments of this application, the at least one resin coating comprises a second resin mixture and a third resin mixture sequentially coating the first resin ball. The second resin mixture comprises a second resin, and the third resin mixture comprises a third resin. The char residue of the second resin is greater than that of the first resin and less than that of the third resin.

[0015] In some embodiments of this application, the second resin mixture further includes at least one of a template agent and a fast ion conductor, the carbon residue of the second resin is between 46% and 60%, the amount of template agent added is 1 wt.% to 20 wt.% of the weight of the second resin, and the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the weight of the second resin; the third resin mixture further includes at least one of a template agent and a fast ion conductor, the carbon residue of the third resin is between 61% and 90%, the amount of template agent added is 1 wt.% to 20 wt.% of the weight of the third resin, and the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the weight of the third resin.

[0016] In some embodiments of this application, the second resin mixture comprises at least one of a first resin, a second resin, a template agent, and a fast ion conductor. The weight percentages of the first resin, the second resin, the template agent, and the fast ion conductor are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the total weight of the first and second resins; the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the total weight of the first and second resins; and the char residue of the second resin is between 46% and 60%. The third resin mixture comprises at least one of a first resin, a third resin, a template agent, and a fast ion conductor. The weight percentages of the first resin, the third resin, the template agent, and the fast ion conductor are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the total weight of the first and third resins; the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the total weight of the first and third resins; and the char residue of the third resin is between 61% and 90%.

[0017] In some embodiments of this application, the second resin mixture comprises at least one of a first resin, a third resin, a template agent, and a fast ion conductor. The weight percentages of the first resin, the third resin, the template agent, and the fast ion conductor are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the total weight of the first and third resins; the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the total weight of the first and third resins; and the char residue of the third resin is between 61% and 90%. Alternatively, the third resin mixture comprises at least one of a second resin, a third resin, a template agent, and a fast ion conductor. The weight percentages of the second resin, the third resin, the template agent, and the fast ion conductor are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the total weight of the second and third resins; the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the total weight of the second and third resins; and the char residue of the second resin is between 46% and 60%.

[0018] In some embodiments of this application, the method of forming core-shell resin balls by coating the surface of the first resin ball with at least one layer of resin coating material includes: adding a second resin mixture to the first resin ball dispersion, reacting at a temperature of 60-200°C for a second set time until the second resin mixture coats the surface of the first resin ball; reacting at a temperature of 60-200°C for a fifth set time, centrifuging to separate the solids and drying them to obtain the core-shell resin balls.

[0019] In some embodiments of this application, the method of forming a core-shell resin ball by coating the surface of the first resin ball with at least one layer of resin coating material further includes: after the second resin mixture coats the surface of the first resin ball, a third resin mixture is added to the reaction vessel, and the reaction is carried out at a temperature of 60 to 200°C for a third set time until the third resin mixture coats the surface of the second resin mixture.

[0020] In some embodiments of this application, the first resin includes any one of epoxy resin, phenol-formaldehyde resin, m-diphenol-formaldehyde resin, cashew oil-modified phenolic resin, melamine-formaldehyde resin, urea-formaldehyde resin, furfuryl alcohol resin, polyurethane resin, and organosilicon resin; and / or the second resin includes any one of epoxy resin, phenol-formaldehyde resin, m-diphenol-formaldehyde resin, barium phenolic resin, molybdenum phenolic resin, cashew oil-modified phenolic resin, melamine-formaldehyde resin, urea-formaldehyde resin, furfural-phenol resin, furfural-acetone resin, polyimide, and polyurethane resin; and / or the third resin includes any one of phenol-formaldehyde resin, m-diphenol-formaldehyde resin, boron phenolic resin, phosphorus phenolic resin, barium phenolic resin, molybdenum phenolic resin, polybenzamide, polybenzamide, benzoxazine resin, polyimide, furfural-phenol resin, furfural-acetone resin, polyoxymethylene, and polyarylacetylene.

[0021] In some embodiments of this application, the fast ion conductor is made of at least one of carbon black, carbon nanotubes, fullerene, and graphene; and / or the template agent includes any one or more of polyether L61, polyether L62, polyether L63, polyether L64, polyether L72, polyether L81, polyether L92, polyether L101, polyether L121, polyether L122, polyether F38, polyether F68, polyether F77, polyether F87, polyether F88, polyether F108, polyether F127, polyether P103, polyether P104, polyether P105, and polyether P123.

[0022] This application also provides a method for preparing a silicon-carbon anode material, comprising: using core-shell porous carbon microspheres as a matrix, allowing silicon-containing gas to diffuse and adsorb into the pores of the core-shell porous carbon microspheres and undergo a cracking reaction within the pores, and depositing elemental silicon on the pore walls.

[0023] In some embodiments of this application, the method further includes forming a carbon coating layer on the surface of the silicon-carbon anode material.

[0024] In some embodiments of this application, the silicon-containing gas includes one or more of silane, disilane, propane, dimethylsilane, hexamethyldisilane, dichlorosilane, trichlorosilane, silicon tetrachloride, and silicon tetrafluoride; and / or the temperature for depositing elemental silicon on the pore walls of the pores is 300–1000°C, and the time is 0.5–6 h.

[0025] This application also provides a core-shell porous carbon microsphere, formed by any of the above-described methods for preparing core-shell porous carbon microspheres, comprising: a first porous carbon layer and at least one coated porous carbon layer covering the first porous carbon layer, wherein the first porous carbon layer is formed by carbonizing the microsphere-shaped first resin ball, and the coated porous carbon layer is formed by carbonizing the resin coating.

[0026] This application also provides a silicon-carbon anode material, formed using any of the above-described methods for preparing silicon-carbon anode materials, comprising: core-shell porous carbon microspheres and elemental silicon located within the pores of the core-shell porous carbon microspheres.

[0027] In some embodiments of this application, the silicon-carbon anode material further includes a carbon coating layer covering the core-shell porous carbon microspheres.

[0028] Compared with the prior art, the core-shell porous carbon microspheres and their preparation method of this application have the following beneficial effects:

[0029] This application first prepares a first resin ball dispersion by means of a first resin mixture, the first resin ball dispersion including microspheres of the first resin ball, thereby forming a microsphere core. Then, by coating the surface of the microspheres of the first resin ball with coating resins of different char rates, since the resins of different char rates have different shrinkage rates, cavitation or hollow structures will be generated between different resin layers due to the different shrinkage rates of the resins in the subsequent high-temperature carbonization process, thereby obtaining resin balls with different core-shell structures, improving the compaction and expansion properties of the finally formed core-shell porous carbon microspheres.

[0030] Furthermore, in this embodiment, a soft template agent can be added to the resin to create pores and increase the mesopore content, thereby reducing the impact of slow ion dynamics in the micropores; resins containing different elements can be used for doping, thereby introducing heteroatoms or fast ion conductor materials into the porous carbon matrix to solve the problem of poor conductivity of porous carbon, and to solve the problems of limited rate performance and low power density. Attached Figure Description

[0031] The following accompanying drawings describe in detail the exemplary embodiments disclosed in this application. The same reference numerals denote similar structures in several views of the drawings. Those skilled in the art will understand that these embodiments are non-limiting and exemplary, and the drawings are for illustrative purposes only and are not intended to limit the scope of this application. Other embodiments may similarly fulfill the inventive intent of this application. It should be understood that the drawings are not drawn to scale. Wherein:

[0032] Figure 1 is a schematic flowchart of the preparation method of core-shell porous carbon microspheres according to an embodiment of this application;

[0033] Figure 2 is a schematic diagram of the structure of the core-shell porous carbon microspheres according to an embodiment of this application;

[0034] Figure 3 is a schematic diagram of the structure of the silicon-carbon anode material according to an embodiment of this application. Detailed Implementation

[0035] The following description provides specific application scenarios and requirements for this application, intended to enable those skilled in the art to make and use the content of this application. Various partial modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of this application. Therefore, this application is not limited to the embodiments shown, but rather to the widest scope consistent with the claims.

[0036] Core-shell porous carbon microspheres can be classified according to raw materials into pitch-based core-shell porous carbon microspheres, coal-based core-shell porous carbon microspheres, and polymer-based core-shell porous carbon microspheres. Among polymer-based core-shell porous carbon microspheres, organic resins such as polystyrene resin, phenolic resin, polyacrylonitrile, polyvinylidene chloride, polyvinyl alcohol, and polyimide can be used as precursors. Polystyrene resin has advantages such as high carbonization yield, easy pore formation, and strong adsorption capacity. However, polystyrene resin spheres require sulfonation with sulfonating agents (such as concentrated sulfuric acid or fuming sulfuric acid). If the sulfonation reaction is insufficient or uneven, it can easily lead to problems such as severe adhesion of the carbonized spheres, low strength, and difficulty in maintaining their shape. Phenolic resin has readily available raw materials, a relatively simple production process, and properties such as heat resistance and flame retardancy. Phenolic resin also features high carbonization yield, easy pore formation, rich pore structure, and strong adsorption capacity. Core-shell porous carbon microspheres prepared by polymerizing or chemically activating phenols and aldehydes using traditional methods are mainly solid micropores. However, mesoporous carbon microspheres with complex structures such as hollow cores and shells can be obtained using template-assisted methods. Template methods include hard template methods and soft template methods. Hard template methods can prepare hollow structural materials of different types and morphologies; however, template removal is difficult, which to some extent leads to the collapse and damage of the product structure. While soft template methods allow for easy template removal and avoid the problems of hard template methods, they suffer from poor structural stability and low efficiency, introducing uncertainties to the control of the regularity of the hollow structure and the shell thickness. Furthermore, both hard and soft template methods for preparing hollow structures are expensive, have long reaction times, and require sophisticated experimental processes.

[0037] This application first prepares a first resin ball dispersion by means of a first resin mixture, the first resin ball dispersion including microspheres of the first resin ball, thereby forming a microsphere core. Then, by coating the surface of the microspheres of the first resin ball with coating resins of different char rates, since the resins of different char rates have different shrinkage rates, cavitation or hollow structures will be generated between different resin layers due to the different shrinkage rates of the resins in the subsequent high-temperature carbonization process, thereby obtaining resin balls with different core-shell structures, improving the compaction and expansion properties of the finally formed core-shell porous carbon microspheres.

[0038] Referring to Figure 1, the preparation method of core-shell porous carbon microspheres according to an embodiment of this application includes the following steps:

[0039] Step S1: Prepare a first resin ball dispersion by preparing a first resin mixture, wherein the first resin mixture includes a first resin, the first resin has a first char residue, and the first resin ball dispersion includes microsphere-shaped first resin balls.

[0040] Step S2: Coat the surface of the first resin ball with at least one layer of resin coating to form a core-shell resin ball. Each layer of the resin coating includes coating resin. The residual carbon content of the coating resin is greater than that of the first resin. When there is more than one layer of resin coating, the residual carbon content of the coating resin increases sequentially in the direction away from the surface of the first resin ball.

[0041] Step S3: After carbonizing the core-shell resin spheres, they are then activated to form core-shell porous carbon microspheres.

[0042] First, perform step S1: prepare a first resin ball dispersion from the first resin mixture, wherein the first resin ball dispersion includes microsphere-shaped first resin balls.

[0043] In some embodiments of this application, the method for preparing the first resin ball dispersion includes: adding a first organic solvent and water to the first resin mixture to adjust the solid content of the first resin mixture from 50-100% to 30-60%, wherein the mass ratio of the first organic solvent and water to the first resin is in the range of (1-5):1, and the mass ratio of the first organic solvent to water is 1:1 to 1:10; adding a first emulsifier, a second organic solvent, and water until the solid content of the first resin mixture is reduced to 5-40%, wherein the mass percentage of the first emulsifier, the second organic solvent, and water to the first resin is in the range of (1-10):(1-15):1, and the mass ratio of the second organic solvent to water is 1:1 to 1:10; and reacting the first resin mixture at a temperature of 60-200°C for a first set time to obtain the first resin ball dispersion.

[0044] This application forms core-shell resin balls by forming a first resin ball dispersion containing microspheres. The process is simple and low-cost. The particle size of the first resin ball dispersion can be adjusted by adjusting the solid content, so that the particle size of the microspheres in the first resin ball dispersion is in the range of 1 to 10 μm.

[0045] In some embodiments of this application, the first organic solvent and the second organic solvent respectively include at least one of benzene, toluene, xylene, pentane, hexane, octane, cyclohexane, cyclohexanone, methylcyclohexanone, chlorobenzene, dichlorobenzene, dichloromethane, methanol, ethanol, isopropanol, diethyl ether, propylene oxide, methyl acetate, ethyl acetate, propyl acetate, acetone, methyl butyl ketone, methyl isobutyl ketone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, acetonitrile, and pyridine.

[0046] The first emulsifier includes one or more of the following: propylene oxide and ethylene oxide polymer F127, polyvinylpyrrolidone (PVP), sodium dodecyl sulfonate, hexadecyltrimethylammonium bromide (CTAB), alkoxylated fatty alcohol F86, polyoxyethylene ether (F108), and polyvinyl alcohol. The amount of the emulsifier added is 1 wt.% to 10 wt.% of the total weight of the resin mixture.

[0047] In some embodiments of this application, the first resin mixture includes a first resin, and at least one of a template agent and a fast ion conductor, wherein the char residue of the first resin is between 20% and 45%. The template agent can create pores during subsequent carbonization treatment of the core-shell resin spheres, thereby increasing the specific surface area of ​​the formed core-shell porous carbon microspheres; the fast ion conductor can increase the conductivity of the formed core-shell porous carbon microspheres, improving their electrical conductivity.

[0048] The method for preparing the first resin mixture may include: uniformly mixing a first resin, and at least one of a template agent and a fast ion conductor, to obtain the first resin mixture. In some embodiments of this application, the weight percentages of the first resin, template agent, and fast ion conductor in the first resin mixture are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the weight of the first resin, for example, 3 wt.%, 8 wt.%, 13 wt.%, and 18 wt.%; the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the weight of the first resin, for example, 0.05 wt.%, 0.1 wt.%, 1 wt.%, 4 wt.%, and 8 wt.%.

[0049] In some embodiments of this application, the first resin includes any one of epoxy resin, phenol-formaldehyde resin, re-diphenol-formaldehyde resin, cashew nut oil modified phenolic resin, melamine-formaldehyde resin, urea-formaldehyde resin, furfuryl alcohol resin, polyurethane resin, and organosilicon resin. In some embodiments of this application, the fast ion conductor is made of at least one of carbon black, carbon nanotubes, fullerene, and graphene. In some embodiments of this application, the template agent includes one or more of polyether L61, polyether L62, polyether L63, polyether L64, polyether L72, polyether L81, polyether L92, polyether L101, polyether L121, polyether L122, polyether F38, polyether F68, polyether F77, polyether F87, polyether F88, polyether F108, polyether F127, polyether P103, polyether P104, polyether P105, and polyether P123.

[0050] Step S2: At least one layer of resin coating is applied to the surface of the first resin ball to form a core-shell resin ball. Each layer of the resin coating includes coating resin, and the char residue of the coating resin is greater than that of the first resin. When there is more than one layer of resin coating, the char residue of the coating resin increases sequentially in the direction away from the surface of the first resin ball. Since the first resin ball dispersion described in this embodiment includes microspheres of the first resin ball, when the resin coating solution is added to the first resin ball dispersion, the coating resin in the resin coating solution will continue to coat the surface of the first resin ball to form a ball.

[0051] In some embodiments of this application, the at least one resin coating is a second resin mixture, which includes a second resin, and at least one of a template agent and a fast ion conductor. The char residue of the second resin is between 46% and 60%. The weight percentages of the second resin, template agent, and fast ion conductor in the second resin mixture are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the weight of the second resin, for example, 3 wt.%, 8 wt.%, 13 wt.%, and 18 wt.%; the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the weight of the second resin, for example, 0.05 wt.%, 0.1 wt.%, 1 wt.%, 4 wt.%, and 8 wt.%.

[0052] In some embodiments of this application, the at least one resin coating is a third resin mixture, which includes a third resin, a template agent, and at least one fast ion conductor. The char residue of the third resin is between 61% and 90%. The weight percentages of the third resin, template agent, and fast ion conductor in the third resin mixture are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the weight of the second resin, for example, 3 wt.%, 8 wt.%, 13 wt.%, and 18 wt.%; the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the weight of the second resin, for example, 0.05 wt.%, 0.1 wt.%, 1 wt.%, 4 wt.%, and 8 wt.%.

[0053] In some embodiments of this application, the at least one resin coating comprises a second resin mixture and a third resin mixture sequentially coating the first resin ball. The second resin mixture comprises a second resin, and the third resin mixture comprises a third resin. The char residue of the second resin is greater than that of the first resin and less than that of the third resin. For example, the char residue of the first resin is between 20% and 45%, the char residue of the second resin is between 46% and 60%, and the char residue of the third resin is between 61% and 90%. The second resin mixture may further include at least one of a template agent and a fast ion conductor. The weight percentages of the second resin, template agent, and fast ion conductor in the second resin mixture are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the weight of the second resin, for example, 3 wt.%, 8 wt.%, 13 wt.%, and 18 wt.%; the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the weight of the second resin, for example, 0.05 wt.%, 0.1 wt.%, 1 wt.%, 4 wt.%, and 8 wt.%. The third resin mixture may further include at least one of a template agent and a fast ion conductor. The weight percentages of the third resin, template agent, and fast ion conductor in the third resin mixture are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the weight of the second resin, for example, 3 wt.%, 8 wt.%, 13 wt.%, and 18 wt.%; the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the weight of the second resin, for example, 0.05 wt.%, 0.1 wt.%, 1 wt.%, 4 wt.%, and 8 wt.%.

[0054] In some embodiments of this application, the second resin mixture comprises at least one of a first resin, a second resin, a template agent, and a fast ion conductor. The weight percentages of the first resin, the second resin, the template agent, and the fast ion conductor are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the total weight of the first and second resins; the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the total weight of the first and second resins; the char residue of the first resin is between 20% and 45%; the char residue of the second resin is between 46% and 60%; and the mass ratio of the first resin to the second resin can be adjusted as needed. Adjustments are required; the third resin mixture includes at least one of a first resin, a third resin, a template agent, and a fast ion conductor, wherein the weight percentages of the first resin, the third resin, the template agent, and the fast ion conductor are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the total weight of the first and third resins, the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the total weight of the first and third resins, the char residue of the first resin is between 20% and 45%, the char residue of the third resin is between 61% and 90%, and the mass ratio of the first resin to the third resin can be adjusted as needed.

[0055] In some embodiments of this application, the second resin mixture includes at least one of a first resin, a third resin, a template agent, and a fast ion conductor. The weight percentages of the first resin, the third resin, the template agent, and the fast ion conductor are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the total weight of the first and third resins; the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the total weight of the first and third resins; the char residue of the first resin is between 20% and 45%; the char residue of the third resin is between 61% and 90%; and the weight percentages of the first and third resins are as follows: The mass ratio of the resin can be adjusted as needed; the third resin mixture includes at least one of the second resin, the third resin, and a template agent and a fast ion conductor, wherein the weight percentages of the second resin, the third resin, the template agent, and the fast ion conductor are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the total weight of the second resin and the third resin, the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the total weight of the second resin and the third resin, the char residue of the second resin is between 46% and 60%, and the mass ratio of the second resin and the third resin can be adjusted as needed.

[0056] In other words, the first resin mixture can be made by mixing a single resin with at least one of a template agent and a fast ion conductor, or it can be made by mixing two or more resins and then mixing them with at least one of a template agent and a fast ion conductor.

[0057] In some embodiments of this application, the method of forming core-shell resin spheres by coating the surface of the first resin spheres with at least one layer of resin coating material includes: adding a second resin mixture to the first resin sphere dispersion, reacting at a temperature of 60–200°C for a second predetermined time until the second resin mixture coats the surface of the first resin spheres; reacting at a temperature of 60–200°C for a fifth predetermined time, separating the solids and drying them to obtain the core-shell resin spheres. Because the surface of the microspherical first resin spheres in the first resin sphere dispersion has a large number of specific surface functional groups, the second resin in the second resin mixture will anchor to the surface of the first resin spheres through hydrogen bonding, undergoing condensation and further growing to form highly cross-linked clustered core-shell resin spheres. At a temperature of 60–200°C, the second resin in the second resin mixture can solidify on the surface of the first resin spheres at a faster rate, thereby promoting the formation of the core-shell resin spheres. After the predetermined reaction time, the second resin in the second resin mixture can completely coat the surface of the first resin spheres.

[0058] The separation includes any one of centrifugation, filtration, and pressure filtration; the drying method includes one of atmospheric pressure drying, vacuum drying, spray drying, and fluidized bed drying; the drying temperature is 50–300℃, and the drying time is 0.5–20h.

[0059] In some embodiments of this application, the method of forming core-shell resin spheres by coating the surface of the first resin sphere with at least one layer of resin coating material further includes: after the second resin mixture coats the surface of the first resin sphere, a third resin mixture is continuously added to the reaction vessel, and the reaction is carried out at a temperature of 60-200°C for a third set time until the third resin mixture coats the surface of the second resin mixture. Since the surface of the second resin also has a large number of specific surface functional groups, the third resin in the third resin mixture will anchor to the surface of the second resin sphere through hydrogen bonding and undergo condensation polymerization, and further grow to form highly cross-linked clustered core-shell resin spheres.

[0060] In some embodiments of this application, the second resin includes any one of epoxy resin, phenol-formaldehyde resin, m-diphenol-formaldehyde resin, barium phenol-formaldehyde resin, molybdenum phenol-formaldehyde resin, cashew oil-modified phenol-formaldehyde resin, melamine-formaldehyde resin, urea-formaldehyde resin, furfural-phenol resin, furfural-acetone resin, polyimide, and polyurethane resin.

[0061] In some embodiments of this application, the third resin includes any one of phenol-formaldehyde resin, m-diphenol-formaldehyde resin, boron phenol-formaldehyde resin, phosphorus phenol-formaldehyde resin, barium phenol-formaldehyde resin, molybdenum phenol-formaldehyde resin, polybenzamide, polybenzamide, benzoxazine resin, polyimide, furfural-phenol resin, furfural-acetone resin, polyoxymethylene diphenylene, and polyarylacetylene.

[0062] Step S3: The core-shell resin spheres are carbonized and then activated to form core-shell porous carbon microspheres. During the carbonization process, the resin molecules in the core-shell resin spheres undergo a carbonization reaction, transforming into core-shell porous carbon microspheres. The carbonization process includes the breaking of macromolecular C-C and CH bonds, the cleavage of oxygen- and nitrogen-containing functional groups, and then a series of complex physical and chemical processes such as cyclization and aromatization to transform them into core-shell porous carbon microspheres. The structure of the core-shell porous carbon microspheres contains a certain amount of porosity, which is beneficial for subsequent activation.

[0063] In some embodiments of this application, the carbonization process can be carried out under vacuum conditions or an inert atmosphere, wherein the inert atmosphere can be an inert atmosphere formed by at least one of nitrogen, argon, or helium; the carbonization equipment used in the carbonization process can be a box furnace, a vacuum furnace, a pusher kiln, or a rotary kiln. For example, the carbonization process includes: after introducing an inert atmosphere into the reaction chamber, heating at a rate of 1–20 °C / min, heating to 300–1000 °C, and holding at that temperature for 0.5–10 hours.

[0064] The activation treatment can be either physical or chemical, and can yield porous carbon with a higher specific surface area. Physical activation refers to gas activation, which uses water vapor, flue gas (a mixture of water vapor, CO2, N2, etc.), CO2, or air as the activating gas, and contacts the carbonized core-shell resin balls at a high temperature of 800–1000°C. During physical activation, the oxidizing activating gas erodes the surface of the carbonized core-shell resin balls at high temperature, causing the previously closed pores in the carbonized core-shell resin balls to reopen and further expand. The structure in the core-shell resin balls generates new pores due to selective oxidation, while tar and uncarbonized materials are also removed, ultimately yielding activated carbon. Because physical activation typically uses gas as the activating agent, the process is relatively simple, and the generated waste gas is mainly CO2 and water vapor, resulting in less environmental pollution. Chemical activation typically uses dehydrating agents such as potassium hydroxide, sodium hydroxide, and zinc chloride to inhibit the formation of tar and other unwanted products during carbonization. Highly alkaline chemical reagents support the formation of porous structures through dehydration and polymer degradation. The advantages of chemical activation include higher specific surface area and shorter activation time.

[0065] The activator in the activation treatment described in this application embodiment is at least one of water vapor, carbon dioxide, a mixture of water vapor and carbon dioxide, potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, or zinc chloride; the activation temperature is 600–1000℃, and the activation time is 0.5–12 h. The activation treatment forms a rich porous structure in the core-shell porous carbon microspheres. During the activation process, the activator reacts with the core-shell porous carbon microspheres, consuming some carbon atoms in the continuous reaction, thus leaving pores at those locations. Through the selective reaction of the active sites in the core-shell porous carbon microspheres with the activating gas, porous carbon microspheres with a multi-level (including microspheres and mesopores) pore structure are formed. The framework structure is stable and does not easily react with the activating gas, thus maintaining its original structure well.

[0066] This application also provides a method for preparing a silicon-carbon anode material, comprising: using any one of the core-shell porous carbon microspheres described in the embodiments of this application as a matrix, allowing silicon-containing gas to enter the pores of the core-shell porous carbon microspheres through diffusion adsorption and undergoing a cracking reaction in the pores, and depositing elemental silicon on the pore walls.

[0067] In some embodiments of this application, the silicon-containing gas includes one or more of silane, disilane, propane, dimethylsilane, hexamethyldisilane, dichlorosilane, trichlorosilane, silicon tetrachloride, and silicon tetrafluoride. In some embodiments of this application, the core-shell porous carbon microspheres are used as a substrate and placed in a fluidized bed or CVD furnace. A silicon-containing gas, silane, is introduced and diffuses into the pores. Silicon is then deposited on the pore walls of the core-shell porous carbon microspheres via high-temperature pyrolysis, yielding a silicon-carbon anode material. The temperature for depositing elemental silicon on the pore walls is 300–1000°C, and the time is 0.5–6 hours.

[0068] In some embodiments of this application, a step of carbon coating is further included to form a carbon coating layer on the surface of core-shell porous carbon microspheres with elemental silicon deposited within the pores. The method for forming the carbon coating layer includes gas-phase coating and liquid-phase coating, with gas-phase coating being preferred. The gas-phase coating method includes: subjecting a carbon-containing gas to high-temperature pyrolysis, thereby forming the carbon coating layer on the surface of the core-shell porous carbon microspheres with elemental silicon deposited within the pores. The carbon-containing gas includes one or more of methane, ethane, propane, acetylene, propyne, butyne, and ethylene. For example, one or more of methane, ethylene, and acetylene are introduced into a reactor, and high-temperature pyrolysis forms a uniform carbon coating layer on the entire surface of the silicon-carbon anode material. The temperature for forming the carbon coating layer is 300–1000°C, and the coating time is 0.5–6 hours.

[0069] This application also provides a core-shell porous carbon microsphere, formed by any of the above-described methods for preparing core-shell porous carbon microspheres, comprising: a first porous carbon layer and at least one coated porous carbon layer covering the first porous carbon layer, wherein the first porous carbon layer is formed by carbonizing the microsphere-shaped first resin ball, and the coated porous carbon layer is formed by carbonizing the resin coating.

[0070] This application also provides a silicon-carbon anode material, formed using any of the above-described methods for preparing silicon-carbon anode materials, comprising: core-shell porous carbon microspheres and elemental silicon located within the pores of the core-shell porous carbon microspheres. In some embodiments of this application, the silicon-carbon anode material further comprises: a carbon coating layer covering the core-shell porous carbon microspheres.

[0071] This application first prepares a first resin sphere dispersion from a first resin mixture, the first resin sphere dispersion comprising microspheres to form a microsphere core. Then, coatings with resins having different char rates are applied to the surface of the microspheres. Since resins with different char rates have different shrinkage rates, during the subsequent high-temperature carbonization process, the different resin shrinkage rates result in cavitation or hollow structures between the resin layers, thus obtaining resin spheres with different core-shell structures. This improves the compaction and expansion properties of the final core-shell porous carbon microspheres. Simultaneously, a template agent can be added to the resin material to create pores and increase the mesopore content, thereby reducing the impact of slow ion dynamics in the micropores. Furthermore, dopant elements can be added to the resin material to modify it, introducing dopant atoms or fast ion conductors into the porous carbon matrix to address the poor conductivity of porous carbon, thus solving the problems of limited rate performance and low power density. The dopant elements include nitrogen, phosphorus, boron, etc., thereby forming a modified resin material.

[0072] In this embodiment, the method for determining the char residue rate is as follows: Weigh a certain weight of the cured phenolic resin sample (W1) and place it in a crucible (W0) with a constant weight. Cover the crucible and place it in a resistance furnace that has been heated to 800°C. After the temperature is raised back to 800°C and held at that temperature for a certain period of time, remove the sample and place it in a desiccator. After cooling to room temperature, weigh the sample (W2). Perform three parallel determinations and take the arithmetic mean. Char residue rate = 1 - (W1 + W0 - W2) / W1.

[0073] Example 1

[0074] Preparation of core-shell porous carbon microspheres:

[0075] S1. Preparation of the first and second resins:

[0076] A non-water-soluble phenolic resin (first resin) with a carbon residue rate of 42% was uniformly mixed with template agent F127 (added at 3% of the resin mass) to obtain a first resin mixture.

[0077] A water-soluble phenolic resin (second resin) with a residual carbon content of 46% was uniformly mixed with template agent F127 (added at 5% of the resin mass) and fast ion conductor carbon nanotubes (added at 0.03% of the resin mass) to obtain a second resin mixture.

[0078] S2. Synthesis of core-shell resin spheres:

[0079] A first resin mixture and a second resin mixture with a mass ratio of 25:75 were selected. The solid content of the first resin mixture and the second resin mixture was adjusted to 30% by adding methanol (the first organic solvent) and pure water, respectively. After the solid content was adjusted, they were placed in different raw material tanks. The first resin mixture was added to the reaction tank, and the first emulsifier, polyvinylpyrrolidone (3.5% of the resin mass), was added. Methanol (the second organic solvent) and pure water were added to dilute the solid content to 10%, and the mass ratio of methanol to pure water in the system was 1:5. The reaction temperature was controlled at 120°C, and the reaction was stirred for 4 hours to obtain a first resin ball dispersion. Then, the second resin mixture was added to the reaction tank, and the reaction temperature was controlled at 120°C. The reaction was stirred for 3 hours to allow the second resin mixture to coat the surface of the first resin balls. Then, the reaction temperature was controlled at 160°C, and the reaction was stirred for another 2 hours. After centrifugation, the mixture was dried at 180°C for 6 hours to obtain core-shell resin balls.

[0080] S3. Synthesis of core-shell porous carbon:

[0081] The core-shell resin spheres were placed in a carbonization furnace and heated to 600°C at a rate of 2°C / min under a nitrogen protective atmosphere. The temperature was maintained at 600°C for 4 hours and then cooled to room temperature to obtain carbonized material. Then, the heating temperature was increased to 950°C, and carbon dioxide gas was introduced at a flow rate of 2L / kg carbonized material / min to activate the carbon microspheres. After activation for 8 hours, the temperature was lowered to obtain porous carbon microspheres with a core-shell structure.

[0082] Preparation of silicon-carbon anode materials:

[0083] 1 kg of core-shell porous carbon microspheres were placed in a fluidized bed, and nitrogen was introduced to replace the air under vacuum. The reaction temperature was controlled at 550℃, the deposition chamber pressure was ≤200 Pa, and silane gas was introduced at a flow rate of 3.5 L / min. The silicon deposition time was 3 h, and a composite material in which nano-silicon permeates into the pores of the porous carbon microspheres was obtained.

[0084] After stopping the silane supply, the temperature of the fluidized bed was controlled at 600℃, and acetylene gas was continuously introduced into the furnace at a flow rate of 0.5 L / min for 4 hours to achieve surface carbon coating of the composite microsphere material. After natural cooling, a porous silicon-carbon anode material was obtained. The structure of the silicon-carbon anode material is shown in Figure 2, including: core-shell porous carbon microspheres and a carbon coating layer 12 covering the core-shell porous carbon microspheres. The core-shell porous carbon microspheres include a first porous carbon layer 10 and a first coated porous carbon layer 11 covering the core porous carbon layer. The first porous carbon layer 10 is formed by carbonizing the microsphere-shaped first resin ball, and the first coated porous carbon layer 11 is formed by carbonizing the resin coating. The SEM image of the silicon-carbon anode material is shown in Figure 3. It should be noted that since the first porous carbon layer 10 and the first coated porous carbon layer 11 covering the first porous carbon layer are both porous carbon and are formed in the same carbonization process, the boundary between the first porous carbon layer 10 and the first coated porous carbon layer 11 cannot be clearly shown in Figure 3.

[0085] Example 2

[0086] S1. Preparation of the first resin mixture and the second resin mixture:

[0087] A non-water-soluble phenolic resin (second resin) with a carbon residue rate of 56% was uniformly mixed with template agent F127 (added at 2% of the resin mass) to obtain a first resin mixture.

[0088] A mixture of non-water-soluble phenolic resin (third resin) with a residual carbon rate of 69% and non-water-soluble phenolic resin (second resin) with a residual carbon rate of 56% (the two resins in a mass ratio of 5:5) was uniformly mixed with template agent F127 (added at 5% of the resin mass) and fast ion conductor carbon nanotubes (added at 0.05% of the resin mass) to obtain a second resin mixture.

[0089] S2. Synthesis of core-shell resin spheres:

[0090] A first resin mixture and a second resin mixture with a mass ratio of 50:50 were selected. The solid content of the first resin mixture and the second resin mixture in S1 was adjusted to 30% by adding methanol (the first organic solvent). After the solid content was adjusted, they were placed in different raw material tanks. The first resin mixture was added to the reaction tank, and the emulsifier cetyltrimethylammonium bromide (CTAB) was added (the amount added was 5% of the resin mass). Methanol (the second organic solvent) and pure water were added to dilute the solid content to 10%. The mass ratio of methanol to pure water in the system was 1:5. The reaction temperature was controlled at 130°C, and the reaction was stirred for 5 hours to obtain the first resin ball dispersion.

[0091] Then, the second resin mixture was added to the reactor, the reaction temperature was controlled to 130°C, and the reaction was stirred for 2 hours to coat the surface of the first resin ball with the second resin mixture. Then, the reaction temperature was controlled to 180°C, and the reaction was stirred for 1 hour. After centrifugation, the mixture was dried at 150°C for 10 hours to obtain the core-shell resin ball.

[0092] S3. Synthesis of core-shell porous carbon:

[0093] The core-shell resin spheres were placed in a carbonization furnace and heated to 500°C at a rate of 2°C / min under a nitrogen protective atmosphere. Then, the temperature was increased to 700°C at a rate of 1°C / min and held at 700°C for 2 hours before being cooled to room temperature to obtain carbonized material. The carbonized material was then mixed with sodium hydroxide at a mass ratio of 1:3 and activated at 800°C for 1 hour. The activated material was repeatedly washed and filtered with deionized water, hydrochloric acid, and deionized water until the pH of the filtrate was neutral. The material was then dried at 150°C for 10 hours to obtain porous carbon microspheres with a core-shell structure.

[0094] S4. Synthesis of silicon-carbon anode materials:

[0095] 1 kg of core-shell porous carbon microspheres were placed in a fluidized bed, and nitrogen was introduced to replace the air under vacuum. The reaction temperature was controlled at 550℃, the deposition chamber pressure was ≤200 Pa, and silane gas was introduced at a flow rate of 3 L / min. The silicon deposition time was 4 h, resulting in a composite material in which nano-silicon permeates into the pores of the porous carbon microspheres. After stopping the introduction of silane, the temperature of the fluidized bed was controlled at 600℃, and acetylene gas was introduced into the furnace at a flow rate of 0.5 L / min for 4 h to achieve carbon coating on the surface of the composite microspheres. After natural cooling, the porous carbon silicon anode material was obtained.

[0096] Example 3

[0097] S1. Preparation of the first resin mixture and the second resin mixture:

[0098] A first resin mixture was obtained by uniformly mixing a thermoplastic phenolic resin (second resin) with a carbon residue of 56% with fast ion conductor graphene (added at 0.01% of the resin mass).

[0099] A second resin mixture was obtained by uniformly mixing water-soluble phosphorophenolic resin (third resin) with a residual carbon rate of 69% and water-based epoxy resin (first resin) with a residual carbon rate of 35% (the two resins in a mass ratio of 9:1), template agent F127 (added at 5% of the resin mass), and fast ion conductor carbon nanotubes (added at 0.05% of the resin mass). The mass ratio of the first resin mixture to the second resin mixture was 30:70.

[0100] S2. Synthesis of core-shell resin spheres:

[0101] A first resin mixture and a second resin mixture with a mass ratio of 30:70 were selected. The solid content of the first resin mixture and the second resin mixture in S1 was adjusted to 40% by adding ethanol (the first organic solvent) and pure water, respectively. After the solid content was adjusted, they were placed in different raw material tanks. The first resin mixture was added to the reaction tank, and the emulsifier polyvinylpyrrolidone (added at 8% of the resin mass) was added. Methanol (the second organic solvent) and pure water were added to dilute the solid content to 8%, and the mass ratio of methanol to pure water in the system was 1:4. The reaction temperature was controlled at 160℃ and the reaction was carried out for 6 hours to obtain a dispersion of first resin balls. Then, the second resin mixture was added to the reaction tank, and the reaction temperature was controlled at 170℃. The mixture was stirred and reacted for 5 hours to coat the surface of the first resin balls with the second resin mixture. The reaction temperature was then controlled at 180℃ and the reaction was continued to be stirred for 3 hours. After centrifugation, the mixture was dried at 180℃ for 6 hours to obtain core-shell resin balls.

[0102] S3. Synthesis of core-shell porous carbon:

[0103] The core-shell resin spheres were placed in a carbonization furnace and heated to 500°C at a rate of 5°C / min under a nitrogen protective atmosphere. Then, the temperature was increased to 800°C at a rate of 1°C / min and held at 800°C for 1 hour before being cooled to room temperature to obtain carbonized material. The carbonized material and potassium hydroxide were then mixed at a mass ratio of 1:2 and activated at 700°C for 1 hour. The activated material was repeatedly washed and filtered with deionized water, hydrochloric acid, and deionized water until the pH of the filtrate was neutral. The material was then dried at 150°C for 10 hours to obtain porous carbon microspheres with a core-shell structure.

[0104] S4. Synthesis of silicon-carbon anode materials:

[0105] 1 kg of core-shell porous carbon microspheres were placed in a fluidized bed, and nitrogen was introduced to replace the air under vacuum. The reaction temperature was controlled at 550℃, the deposition chamber pressure was ≤200 Pa, and silane gas was introduced at a flow rate of 2 L / min. The silicon deposition time was 5 h, resulting in a composite material in which nano-silicon permeates into the pores of the porous carbon microspheres. After stopping the introduction of silane, the temperature of the fluidized bed was controlled at 600℃, and acetylene gas was introduced into the furnace at a flow rate of 0.5 L / min for 4 h to achieve carbon coating on the surface of the composite microspheres. After natural cooling, the porous carbon silicon anode material was obtained.

[0106] Example 4

[0107] S1. Preparation of the first resin mixture and the second resin mixture:

[0108] A first resin mixture was obtained by uniformly mixing water-soluble melamine-formaldehyde resin with a residual carbon rate of 59% and fast ion conductor graphene (added at 0.02% of the resin mass).

[0109] A second resin mixture was obtained by uniformly mixing furfural resin with a residual carbon content of 62%, template agent P123 (added at 5% of the resin mass), and fast ion conductor carbon nanotubes (added at 0.05% of the resin mass).

[0110] A third resin mixture was obtained by uniformly mixing water-soluble boron phenolic resin with a residual carbon rate of 71%, template agent P123 (added at 5% of the resin mass), and fast ion conductor carbon nanotubes (added at 0.05% of the resin mass). The mass ratio of the first resin mixture, the second resin mixture, and the third resin mixture was 10:20:70.

[0111] S2. Synthesis of core-shell resin spheres:

[0112] A first resin mixture, a second resin mixture, and a third resin mixture with a mass ratio of 10:20:70 were selected. The solid content of the first resin mixture, the second resin mixture, and the third resin mixture in S1 was adjusted to 30%, 20%, and 15% respectively by adding pure water, methanol, and pure water. After the solid content was adjusted, they were placed in different raw material tanks. The first resin mixture was added to the reaction tank, and the emulsifier polyvinylpyrrolidone (added at 5% of the resin mass) was added. Methanol and pure water were added to dilute the solid content to 8%, and the mass ratio of methanol to pure water in the system was 1:6. The reaction temperature was controlled at 160℃, and the reaction was carried out for 5 hours to obtain a first resin ball dispersion. Then, the second resin mixture was added to the reaction tank, and the reaction temperature was controlled at 170℃. The reaction was stirred for 3 hours to allow the second resin mixture to coat the surface of the first resin balls. The third resin mixture was added to the reaction tank, and the reaction temperature was controlled at 150℃. The reaction was stirred for 6 hours, and the mixture was centrifuged and dried at 150℃ for 8 hours to obtain core-shell resin balls.

[0113] S3. Synthesis of core-shell porous carbon:

[0114] The core-shell resin spheres were placed in a carbonization furnace and heated to 500°C at a rate of 5°C / min under a nitrogen protective atmosphere. Then, the temperature was increased to 800°C at a rate of 1°C / min. The temperature was maintained at 800°C for 1 hour and then cooled to room temperature to obtain carbonized material. The heating temperature was then increased to 900°C, and carbon dioxide gas was introduced at a flow rate of 3 L / kg carbonized material / min to activate the carbon microspheres. After activation for 10 hours, the temperature was lowered to obtain porous carbon microspheres with a core-shell structure.

[0115] S4. Synthesis of silicon-carbon anode materials:

[0116] [Corrected according to Rule 91 07.04.2025] 1 kg of core-shell porous carbon microspheres were placed in a fluidized bed, and nitrogen was introduced to replace the air under vacuum. The reaction temperature was controlled at 550°C, the deposition chamber pressure was ≤200 Pa, and silane gas was introduced at a flow rate of 2 L / min. The silicon deposition time was 5 h, resulting in a composite material in which nano-silicon permeates into the pores of the porous carbon microspheres. After stopping the introduction of silane, the temperature of the fluidized bed was controlled at 600°C, and acetylene gas was introduced into the furnace at a flow rate of 0.5 L / min for 4 h to achieve carbon coating on the surface of the composite microspheres. After natural cooling, the porous carbon silicon anode material was obtained.

[0117] Example 5

[0118] S1. Preparation of the first resin mixture:

[0119] A first resin mixture was obtained by uniformly mixing DOPO type benzoxazine resin with a residual carbon rate of 62%, thermoplastic phenolic resin with a residual carbon rate of 38% (the two resins in a mass ratio of 4:1), template agent P123 (added at 5% of the resin mass), and fast ion conductor graphene (added at 0.05% of the resin mass).

[0120] S2. Synthesis of core-shell resin spheres:

[0121] The solid content of the first resin mixture in S1 was adjusted to 10% by adding methanol and pure water, and the mass ratio of methanol to pure water in the system was 1:5. The first resin mixture was then added to a reaction vessel, and the emulsifier polyvinylpyrrolidone (addition amount was 5% of the resin mass) was added. The reaction temperature was controlled at 160℃ and the reaction was carried out for 8 hours. After centrifugation, it was dried at 150℃ for 8 hours to obtain core-shell resin balls.

[0122] S3. Synthesis of core-shell porous carbon:

[0123] The core-shell resin spheres were placed in a carbonization furnace and heated to 500°C at a rate of 5°C / min under a nitrogen protective atmosphere. Then, the temperature was increased to 800°C at a rate of 1°C / min. The temperature was maintained at 800°C for 1 hour and then cooled to room temperature to obtain carbonized material. The heating temperature was then increased to 950°C, and carbon dioxide gas was introduced at a flow rate of 3 L / kg carbonized material / min to activate the carbon microspheres. After activation for 8 hours, the temperature was lowered to obtain porous carbon microspheres with a core-shell structure.

[0124] S4. Synthesis of silicon-carbon anode materials:

[0125] 1 kg of core-shell porous carbon microspheres were placed in a fluidized bed, and nitrogen was introduced to replace the air under vacuum. The reaction temperature was controlled at 550℃, the deposition chamber pressure was ≤200 Pa, and silane gas was introduced at a flow rate of 2 L / min. The silicon deposition time was 5 h, resulting in a composite material in which nano-silicon permeates into the pores of the porous carbon microspheres. After stopping the introduction of silane, the temperature of the fluidized bed was controlled at 600℃, and acetylene gas was introduced into the furnace at a flow rate of 0.5 L / min for 4 h to achieve carbon coating on the surface of the composite microspheres. After natural cooling, the porous carbon silicon anode material was obtained.

[0126] Comparative Example 1

[0127] S1. Preparation of the first resin mixture:

[0128] A first resin mixture was obtained by uniformly mixing water-soluble phenolic resin with a residual carbon rate of 55% with template agent P123 (added at 5% of the resin mass) and fast ion conductor carbon nanotubes (added at 0.05% of the resin mass).

[0129] S2. Synthesis of cured resin:

[0130] The first resin mixture in S1 was placed in a curing chamber and dried and cured at 150°C for 10 hours in an air atmosphere. Then, it was coarsely crushed to obtain the cured resin.

[0131] S3. Synthesis of porous carbon:

[0132] The cured resin was placed in a carbonization furnace and heated to 500°C at a rate of 5°C / min under a nitrogen protective atmosphere. Then, it was heated to 800°C at a rate of 1°C / min and held at 800°C for 1 hour before being cooled to room temperature to obtain carbonized material. The carbonized material was then pulverized and mixed with potassium hydroxide at a mass ratio of 1:2. The temperature was increased to 700°C for activation for 1 hour. The activated material was repeatedly washed and filtered with deionized water, hydrochloric acid, and deionized water until the pH of the filtrate was neutral. The material was then dried at 150°C for 10 hours to obtain porous carbon microspheres with a core-shell structure.

[0133] S4. Synthesis of silicon-carbon anode materials:

[0134] Porous carbon material is placed in a fluidized bed, and nitrogen is introduced to replace the air under vacuum. The reaction temperature is controlled at 550℃, the deposition chamber pressure is ≤200pa, and silane gas is introduced at a flow rate of 2L / min. The silicon deposition time is 5h, resulting in a composite material in which nano-silicon permeates into the porous carbon channels. After stopping the introduction of silane, the temperature of the fluidized bed is controlled at 600℃, and acetylene gas is introduced into the furnace at a flow rate of 0.5L / min for 4h to achieve carbon coating on the surface of the composite material. After natural cooling, the porous carbon silicon anode material is obtained.

[0135] Table 1

[0136] Table 2

[0137] Table 1 shows the specific surface area, pore volume, particle size and mesopore ratio of the silicon-carbon anode material formed in the embodiments of this application. It can be seen from the table that: Examples 1 to 5 can prepare similar specific surface area, pore volume and particle size as in Comparative Example 1, and their basic indicators are not affected by the method.

[0138] Table 2 shows a comparison of the electrical performance data of the silicon-carbon anode materials formed in the embodiments of this application. It can be seen that the first-cycle full-charge expansion rate of the electrodes in Examples 1 to 5 is significantly lower than that in Comparative Example 1, indicating that the hollow structure prepared in Examples 1 to 5 can effectively suppress the expansion after charging and discharging; thereby effectively protecting the SEI on the material surface from expansion and cracking, and effectively improving the cycle capacity retention rate of the material.

[0139] Finally, it should be understood that the embodiments disclosed herein are illustrative of the principles of the embodiments of this application. Other modified embodiments are also within the scope of this application. Therefore, the embodiments disclosed herein are merely examples and not limitations. Those skilled in the art can implement the applications in this application by adopting alternative configurations based on the embodiments in this application. Therefore, the embodiments of this application are not limited to those embodiments precisely described in the application.

Claims

1. A method for preparing core-shell porous carbon microspheres, characterized in that, include: The first resin mixture is prepared into a first resin ball dispersion, the first resin mixture comprising a first resin having a first char residue, and the first resin ball dispersion comprising microsphere-shaped first resin balls. At least one layer of resin coating is coated on the surface of the first resin ball to form a core-shell resin ball. Each layer of the resin coating includes coating resin. The residual carbon content of the coating resin is greater than that of the first resin. When there is more than one layer of resin coating, the residual carbon content of the coating resin increases sequentially in the direction away from the surface of the first resin ball. The core-shell resin spheres are carbonized and then activated to form core-shell porous carbon microspheres.

2. The method for preparing core-shell porous carbon microspheres according to claim 1, characterized in that, The method for preparing the first resin ball dispersion includes: Add a first organic solvent and water to the first resin mixture to adjust the solid content of the first resin mixture from 50-100% to 30-60%, wherein the mass ratio of the first organic solvent and water to the first resin is in the range of (1-5):1, and the mass ratio of the first organic solvent to water is 1:1 to 1:10; The solid content of the first resin mixture is reduced to 5-40% by adding a first emulsifier, a second organic solvent and water, wherein the mass percentage of the first emulsifier, the second organic solvent and water to the first resin is in the range of (1-10):(1-15):1, and the mass ratio of the second organic solvent to water is 1:1 to 1:10; The first resin mixture is reacted at a temperature of 60-200°C for a first set time until the first resin ball dispersion is obtained.

3. The method for preparing core-shell porous carbon microspheres according to claim 2, characterized in that, The first organic solvent and the second organic solvent each include at least one of benzene, toluene, xylene, pentane, hexane, octane, cyclohexane, cyclohexanone, methylcyclohexanone, chlorobenzene, dichlorobenzene, dichloromethane, methanol, ethanol, isopropanol, diethyl ether, propylene oxide, methyl acetate, ethyl acetate, propyl acetate, acetone, methyl butyl ketone, methyl isobutyl ketone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, acetonitrile, and pyridine; the first emulsifier includes at least one of the following: a polymer of propylene oxide and ethylene oxide F127, polyvinylpyrrolidone (PVP), sodium dodecyl sulfonate, hexadecyltrimethylammonium bromide (CTAB), alkoxylated fatty alcohol F86, polyoxyethylene ether F108, and polyvinyl alcohol.

4. The method for preparing core-shell porous carbon microspheres according to claim 1, characterized in that, The first resin mixture further includes at least one of a template agent and a fast ion conductor. The carbon residue of the first resin is between 20% and 45%. The weight percentages of the first resin, the template agent, and the fast ion conductor are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the weight of the first resin, and the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the weight of the first resin.

5. The method for preparing core-shell porous carbon microspheres according to claim 4, characterized in that, The at least one resin coating comprises a second resin mixture or a third resin mixture, wherein the second resin mixture comprises a second resin, the third resin mixture comprises a third resin, the char residue of the second resin is greater than that of the first resin, and the char residue of the third resin is greater than that of the first resin.

6. The method for preparing core-shell porous carbon microspheres according to claim 4, characterized in that, The at least one resin coating comprises a second resin mixture and a third resin mixture that sequentially coat the first resin ball. The second resin mixture comprises a second resin, and the third resin mixture comprises a third resin. The char residue of the second resin is greater than that of the first resin and less than that of the third resin.

7. The method for preparing core-shell porous carbon microspheres according to claim 5 or 6, characterized in that, The second resin mixture further includes at least one of a template agent and a fast ion conductor, the carbon residue of the second resin is between 46% and 60%, the amount of template agent added is 1 wt.% to 20 wt.% of the weight of the second resin, and the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the weight of the second resin; The third resin mixture further includes at least one of a template agent and a fast ion conductor, the char residue of the third resin is between 61% and 90%, the amount of template agent added is 1 wt.% to 20 wt.% of the weight of the third resin, and the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the weight of the third resin.

8. The method for preparing core-shell porous carbon microspheres according to claim 5 or 6, characterized in that, The second resin mixture comprises at least one of a first resin, a second resin, a template agent, and a fast ion conductor, wherein the weight percentages of the first resin, the second resin, the template agent, and the fast ion conductor are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the total weight of the first resin and the second resin, the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the total weight of the first resin and the second resin, and the char residue of the second resin is between 46% and 60%. The third resin mixture includes at least one of a first resin, a third resin, a template agent, and a fast ion conductor. The weight percentages of the first resin, the third resin, the template agent, and the fast ion conductor are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the total weight of the first and third resins; the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the total weight of the first and third resins; and the char residue of the third resin is between 61% and 90%.

9. The method for preparing core-shell porous carbon microspheres according to claim 5 or 6, characterized in that, The second resin mixture includes at least one of a first resin, a third resin, a template agent, and a fast ion conductor, wherein the weight percentages of the first resin, the third resin, the template agent, and the fast ion conductor are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the total weight of the first resin and the third resin; the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the total weight of the first resin and the third resin; and the char residue of the third resin is between 61% and 90%. The third resin mixture includes at least one of a second resin, a third resin, a template agent, and a fast ion conductor. The weight percentages of the second resin, the third resin, the template agent, and the fast ion conductor are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the total weight of the second and third resins; the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the total weight of the second and third resins; and the char residue of the second resin is between 46% and 60%.

10. The method for preparing core-shell porous carbon microspheres according to claim 9, characterized in that, A method for forming core-shell resin spheres by coating the surface of the first resin sphere with at least one layer of resin coating material includes: adding a second resin mixture to the first resin sphere dispersion, reacting at a temperature of 60-200°C for a second set time until the second resin mixture coats the surface of the first resin sphere; reacting at a temperature of 60-200°C for a fifth set time, centrifuging to separate the solids and drying them to obtain the core-shell resin spheres.

11. The method for preparing core-shell porous carbon microspheres according to claim 10, characterized in that, The method of forming a core-shell resin ball by coating the surface of the first resin ball with at least one layer of resin coating material further includes: after the second resin mixture coats the surface of the first resin ball, a third resin mixture is added to the reaction vessel, and the reaction is carried out at a temperature of 60 to 200°C for a third set time until the third resin mixture coats the surface of the second resin mixture.

12. The method for preparing core-shell porous carbon microspheres according to claim 5 or 6, characterized in that, The first resin includes any one of epoxy resin, phenol-formaldehyde resin, resorcinol-formaldehyde resin, cashew oil-modified phenolic resin, melamine-formaldehyde resin, urea-formaldehyde resin, furfuryl alcohol resin, polyurethane resin, and silicone resin, and / or The second resin includes any one of epoxy resin, phenol-formaldehyde resin, m-diphenol-formaldehyde resin, barium phenol-formaldehyde resin, molybdenum phenol-formaldehyde resin, cashew oil-modified phenol-formaldehyde resin, melamine-formaldehyde resin, urea-formaldehyde resin, furfural-phenol resin, furfural-acetone resin, polyimide, and polyurethane resin; and / or The third resin includes any one of phenol-formaldehyde resin, m-diphenol-formaldehyde resin, boron phenol-formaldehyde resin, phosphorus phenol-formaldehyde resin, barium phenol-formaldehyde resin, molybdenum phenol-formaldehyde resin, polybenzamide, polybenzamide, benzoxazine resin, polyimide, furfural-phenol resin, furfural-acetone resin, polyoxymethylene, and polyarylacetylene.

13. The method for preparing core-shell porous carbon microspheres according to claim 12, characterized in that, The fast ion conductor is made of at least one of carbon black, carbon nanotubes, fullerene, and graphene; and / or The template agent includes any one or more of polyether L61, polyether L62, polyether L63, polyether L64, polyether L72, polyether L81, polyether L92, polyether L101, polyether L121, polyether L122, polyether F38, polyether F68, polyether F77, polyether F87, polyether F88, polyether F108, polyether F127, polyether P103, polyether P104, polyether P105, and polyether P123.

14. A method for preparing a silicon-carbon anode material, characterized in that, include: Using the core-shell porous carbon microspheres as described in any one of claims 1 to 13 as a matrix, silicon-containing gas is diffused and adsorbed into the pores of the core-shell porous carbon microspheres and undergoes a cracking reaction within the pores, thereby depositing elemental silicon on the pore walls.

15. The method for preparing the silicon-carbon anode material according to claim 14, characterized in that, The method further includes forming a carbon coating layer on the surface of the silicon-carbon anode material.

16. The method for preparing the silicon-carbon anode material according to claim 14, characterized in that, The silicon-containing gas includes one or more of silane, disilane, propane, dimethylsilane, hexamethyldisilane, dichlorosilane, trichlorosilane, silicon tetrachloride, and silicon tetrafluoride; and / or the temperature for depositing elemental silicon on the pore walls of the pores is 300–1000°C, and the time is 0.5–6 h.

17. A core-shell porous carbon microsphere, formed by any one of claims 1 to 13, characterized in that, include: A first porous carbon layer and at least one coated porous carbon layer covering the first porous carbon layer, wherein the first porous carbon layer is formed by carbonization of the microsphere-shaped first resin sphere, and the coated porous carbon layer is formed by carbonization of the resin coating.

18. A silicon-carbon anode material, formed by any one of claims 14 to 16, characterized in that, include: Core-shell porous carbon microspheres and elemental silicon located within the pores of the core-shell porous carbon microspheres.

19. The silicon-carbon anode material according to claim 18, characterized in that, Also includes: A carbon coating layer that covers the core-shell porous carbon microspheres.

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