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

Abstract

The present application provides a core-shell porous carbon microsphere, a silicon-carbon anode material, and a preparation method therefor. The preparation method for a core-shell porous carbon microsphere comprises: preparing an inner core material and a first coating material, the char yield of the first coating material being greater than the char yield of the inner core material; adjusting the solid content of the inner core material to 20% to 30%, and dispersing and emulsifying the inner core material and the first coating material under the action of a first emulsifier to form a first emulsion; spray-drying the first emulsion to acquire a core-shell resin sphere, the core-shell resin sphere comprising an inner core formed of the inner core material and a first coating layer formed of the first coating material and coating the inner core; and performing carbonization treatment on the core-shell resin sphere, followed by activation treatment, to form a core-shell porous carbon microsphere. When the core-shell porous carbon microsphere is applied to a silicon-carbon material, the volume expansion of the silicon-carbon material can be effectively alleviated, improving the cyclic 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 core-shell porous carbon microsphere, a silicon-carbon anode material, and a method for preparing the same. When applied to silicon-carbon materials, these materials can effectively alleviate volume expansion and improve cycle stability and rate performance.

[0008] This application provides a method for preparing core-shell porous carbon microspheres, comprising: preparing a core material and a first coating material, wherein both the core material and the first coating material include a resin material, the residual char rate of the first coating material is greater than that of the core material, and the hydrophilicity of the resin material in the first coating material is opposite to that of the resin material in the core material; adjusting the solid content of the core material to 20% to 30%, dispersing and emulsifying the core material and the first coating material under the action of a first emulsifier to form a first emulsion; spray-drying the first emulsion to obtain core-shell resin spheres, wherein the core-shell resin spheres include a core composed of the core material and a first coating layer composed of the first coating material and covering the core; and carbonizing the core-shell resin spheres and then activating them to form core-shell porous carbon microspheres.

[0009] In some embodiments of this application, after obtaining the core-shell resin ball, the method further includes: coating the surface of the core-shell resin ball with at least one layer of coating material, each layer of coating material comprising at least one resin material, the residual carbon content of the coating material being greater than that of the first coating material, and when there is more than one layer of coating material, the residual carbon content of the coating material increasing sequentially in the direction away from the surface of the core-shell resin ball.

[0010] In some embodiments of this application, the weight ratio of the core material to the first coating material is 1:(1-10); the weight of the first emulsifier is 0.01% to 5% of the sum of the weights of the core material and the first coating material.

[0011] In some embodiments of this application, the core material 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%, and the weight percentages of the first resin, template agent, and fast ion conductor in the core material 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.

[0012] In some embodiments of this application, the first coating material 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 first coating material are: 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; or

[0013] The first coating material comprises a third resin, and at least one of a template agent and a fast ion conductor, wherein the char residue of the third resin is between 61% and 90%, and the weight percentages of the third resin, template agent, and fast ion conductor in the first coating material are as follows: 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.

[0014] In some embodiments of this application, the core material includes a second resin, and at least one of a template agent and a fast ion conductor, wherein the char residue of the second resin is between 46% and 60%, and the weight percentages of the second resin, template agent, and fast ion conductor in the core material are as follows: 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; and

[0015] The first coating material comprises a third resin, and at least one of a template agent and a fast ion conductor, wherein the char residue of the third resin is between 61% and 90%, and the weight percentages of the third resin, template agent, and fast ion conductor in the first coating material are as follows: 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 at least one coating material includes a second coating material and a third coating material that sequentially coat the core-shell resin sphere. The first coating material includes a first resin and at least one of a template agent and a fast ion conductor. The second coating material includes a first resin, a second resin, and at least one of a template agent and a fast ion conductor. The third coating material includes a second resin, a third resin, and at least one of a template agent and a fast ion conductor.

[0017] In some embodiments of this application, the at least one coating material includes a second coating material and a third coating material that sequentially coat the core-shell resin sphere. The first coating material includes a first resin and at least one of a template agent and a fast ion conductor. The second coating material includes a first resin, a third resin, and at least one of a template agent and a fast ion conductor. The third coating material includes a second resin, a third resin, and at least one of a template agent and a fast ion conductor.

[0018] In some embodiments of this application, the method of dispersing and emulsifying the core material and the first coating material under the action of the first emulsifier to form a first emulsion includes: mixing the core material, the first coating material and the first emulsifier, dispersing them at high speed, and then emulsifying them uniformly to form the first emulsion.

[0019] In some embodiments of this application, the method of coating the surface of the core-shell resin ball with at least one coating material includes: adding a second coating material and a first organic solvent to the core-shell resin ball and mixing them evenly; and performing a spray drying treatment to form a second coating layer on the surface of the core-shell resin ball.

[0020] In some embodiments of this application, the first organic solvent includes at least one selected from water, 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.

[0021] In some embodiments of this application, 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

[0022] 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

[0023] 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.

[0024] 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 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.

[0025] In some embodiments of this application, the first emulsifier includes one or more 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. The amount of the first emulsifier added is 0.1 wt.% to 10 wt.% of the total weight of the resin material in the core material and the first coating material.

[0026] This application also provides a method for preparing a silicon-carbon anode material, comprising: using the above-mentioned core-shell porous carbon microspheres 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.

[0027] In some embodiments of this application, the method further includes forming a carbon coating layer on the surface of the silicon-carbon anode material.

[0028] 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.

[0029] This application also provides a core-shell porous carbon microsphere, formed by any of the above methods, comprising: a core porous carbon layer and a first coating porous carbon layer covering the core porous carbon layer, wherein the core porous carbon layer is formed by carbonization of the core material, and the first coating porous carbon layer is formed by carbonization of the first coating material.

[0030] This application also provides a silicon-carbon anode material, comprising: the aforementioned core-shell porous carbon microspheres and elemental silicon located within the pores of the core-shell porous carbon microspheres. Further, the silicon-carbon anode material also includes a carbon coating layer covering the core-shell porous carbon microspheres.

[0031] Compared with the prior art, the core-shell porous carbon microspheres and their preparation method of this application have the following beneficial effects:

[0032] This application embodiment adjusts the residual carbon ratio of the core material and the first coating material to create resin materials with different shrinkage rates at different locations within the formed core-shell resin spheres. Therefore, during the subsequent high-temperature carbonization process, the different resin shrinkage rates allow for the creation of cavitation or hollow structures between different resin layers by controlling the amount of different resins used, resulting in resin spheres with different core-shell structures. This improves the compaction and expansion properties of the porous carbon matrix. Soft template agents can be added to the resin to create pores and increase the mesoporous content, thereby reducing the impact of slow ion dynamics in the micropores. Resins containing different elements can be used for doping, introducing heteroatoms 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. Attached Figure Description

[0033] 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:

[0034] Figure 1 is a schematic flowchart of the preparation method of core-shell porous carbon microspheres according to an embodiment of this application;

[0035] Figure 2 is a schematic diagram of the structure of the core-shell porous carbon microspheres according to an embodiment of this application;

[0036] Figure 3 is a scanning electron microscope image of the silicon-carbon anode material according to an embodiment of this application. Detailed Implementation

[0037] 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.

[0038] 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 traditional methods through the polymerization or chemical activation of phenols and aldehydes 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.

[0039] This application employs polymer resins with different shrinkage rates for doping. Due to the different shrinkage rates of the resins during high-temperature carbonization, by controlling the amount of different resins, cavitation or hollow structures will be generated between different resin layers, thereby obtaining resin spheres with different core-shell structures, which improves the compaction and expansion properties of the porous carbon matrix. At the same time, a 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. In addition, resins containing different elements can be selected for doping, thereby introducing dopant atoms 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.

[0040] Referring to Figure 1, the preparation method of core-shell porous carbon microspheres according to an embodiment of this application includes the following steps:

[0041] Step S1: Prepare a core material and a first coating material. Both the core material and the first coating material include resin materials. The char residue of the first coating material is greater than that of the core material, and the hydrophilicity of the resin material in the first coating material is opposite to that of the resin material in the core material.

[0042] Step S2: Adjust the solid content of the core material to 20% to 30%, and disperse and emulsify the core material and the first coating material under the action of the first emulsifier to form a first emulsion;

[0043] Step S3: After spray drying the first emulsion, a core-shell resin ball is obtained. The core-shell resin ball includes a core made of the core material and a first coating layer made of the first coating material and covering the core.

[0044] Step S4: After carbonizing the core-shell resin spheres, they are then activated to form core-shell porous carbon microspheres.

[0045] First, perform step S1: prepare a core material and a first coating material. Both the core material and the first coating material include resin materials. The char residue of the first coating material is greater than that of the core material, and the hydrophilicity of the resin material in the first coating material is opposite to that of the resin material in the core material.

[0046] The resin material can be either hydrophilic or non-hydrophilic. For example, the hydrophilic resin includes waterborne epoxy resin, waterborne phenol-formaldehyde resin, waterborne resorcinol-formaldehyde resin, waterborne boron phenol-formaldehyde resin, waterborne phosphophenol-formaldehyde resin, waterborne barium phenol-formaldehyde resin, waterborne molybdenum phenol-formaldehyde resin, waterborne melamine-formaldehyde resin, waterborne urea-formaldehyde resin, and waterborne polyurethane, etc. The non-water-soluble resin includes non-water-soluble epoxy resin, non-water-soluble phenol-formaldehyde resin, non-water-soluble resorcinol-formaldehyde resin, non-water-soluble boron phenol-formaldehyde resin, non-water-soluble phosphophenol-formaldehyde resin, non-water-soluble barium phenol-formaldehyde resin, non-water-soluble molybdenum phenol-formaldehyde resin, cashew oil modified phenol-formaldehyde resin, furfural-phenol resin, furfural-acetone resin, furfuryl alcohol resin, benzoxazine resin, polyimide resin, non-hydrophilic polyurethane, and organosilicon resin, etc. The residual carbon content of the resin material is between 20% and 90%.

[0047] In some embodiments of this application, the core material includes a first resin, and at least one of a template agent and a fast ion conductor. The char residue of the first resin is between 20% and 45%. The weight percentages of the first resin, template agent, and fast ion conductor in the core material 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.%.

[0048] In some embodiments of this application, the first coating material 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 first coating material 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.%; or

[0049] The first coating material includes a third resin, and 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 weight percentages of the third resin, template agent, and fast ion conductor in the first coating material 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.%.

[0050] In this embodiment, the hydrophilicity of the resin material in the first coating material is opposite to that of the resin material in the core material. The resin material includes a first resin, a second resin, and a third resin. Therefore, when the first resin in the core material is a non-hydrophilic resin, the second or third resin in the first coating material is a hydrophilic resin. Conversely, when the first resin in the core material is a hydrophilic resin, the second or third resin in the first coating material is a non-hydrophilic resin.

[0051] In some other embodiments of this application, the resin material in the core material may further include a second resin, and the resin material in the first coating material is a third resin, wherein the hydrophilicity of the third resin is opposite to that of the second resin. For example, the core material includes a second resin, and at least one of a template agent and a fast ion conductor, wherein the char residue of the second resin is between 46% and 60%, and the weight percentages of the second resin, template agent, and fast ion conductor in the core material 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 first coating material comprises a third resin, and 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 weight percentages of the third resin, template agent, and fast ion conductor in the first coating material are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the weight of the third 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 third resin, for example, 0.05 wt.%, 0.1 wt.%, 1 wt.%, 4 wt.%, and 8 wt.%. When the second resin in the core material is a hydrophilic resin, the third resin in the first coating material is a non-hydrophilic resin.

[0052] In other embodiments of this application, the core material comprises a mixture of a first resin and a second resin, and 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 char residue of the second resin is between 46% and 60%. The weight percentages of the mixture of the first resin and the second resin, the template agent, and the fast ion conductor in the core material are as follows: the amount of template agent added is 1 wt.% to 20 wt.% of the total weight of the mixture of the first resin and the second resin, and the amount of fast ion conductor added is 0.01 wt.% to 10 wt.% of the total weight of the mixture of the first resin and the second resin. The first coating material comprises a third resin, and 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 weight percentages of the third resin, the template agent, and the fast ion conductor in the first coating material are as follows: 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 total weight of the third resin. When the first and second resins in the core material are hydrophilic resins, the third resin in the first coating material is a non-hydrophilic resin. Since the residual carbon content of both the first and second resins is lower than that of the third resin, the weight ratio of the first and second resins in the core material can be any value.

[0053] In some other embodiments of this application, the core material may further include a mixture of a first resin, a second resin, and a third resin, and at least one of a template agent and a fast ion conductor. The first coating material may include a mixture of a second resin and a third resin. It is only necessary to adjust the weight ratio of the first resin, the second resin, and the third resin according to their residual carbon content so that the residual carbon content of the first coating material is greater than that of the core material, and select the hydrophilicity of the first resin, the second resin, and the third resin so that the hydrophilicity of the resin mixture in the first coating material is opposite to that of the resin mixture in the core material.

[0054] In other words, the core material can be made from a mixture of a single resin and at least one of a template agent and a fast ion conductor, or it can be made from a mixture of two or more resins and then mixed with at least one of a template agent and a fast ion conductor. The first coating material can also be made from a mixture of a single resin and at least one of a template agent and a fast ion conductor, or it can be made from a mixture of two or more resins and then mixed with at least one of a template agent and a fast ion conductor.

[0055] In some embodiments of this application, 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 organosilicon resin, with a char residue rate between 20% and 45%. The first resin can be hydrophilic or non-hydrophilic, and can be selected as needed.

[0056] In some embodiments of this application, the second 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 organosilicon resin, with a char residue rate between 46% and 60%. The second resin can be hydrophilic or non-hydrophilic, and can be selected as needed.

[0057] In some embodiments of this application, the third 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 organosilicon resin, with a char residue rate between 61% and 90%. The third resin can be hydrophilic or non-hydrophilic, and can be selected as needed.

[0058] 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.

[0059] In some embodiments of this application, the method for preparing the core material may include: uniformly mixing a first resin, a template agent, and at least one fast ion conductor to obtain the core material. The method for preparing the first coating material may include: uniformly mixing a second resin, a template agent, and at least one fast ion conductor to obtain the first coating material; or uniformly mixing a third resin, a template agent, and at least one fast ion conductor to obtain the first coating material.

[0060] Even when the core material and the first coating material have different compositions, the core material and the first coating material can still be obtained by uniform mixing.

[0061] Step S2: Adjust the solid content of the core material to 20% to 30%, and disperse and emulsify the core material and the first coating material under the action of the first emulsifier to form a first emulsion; the weight ratio of the core material to the first coating material is 1:(1 to 10); the weight of the first emulsifier is 0.01% to 5% of the sum of the weights of the core material and the first coating material.

[0062] In some embodiments of this application, the first emulsifier includes one or more of the following: propylene oxide and ethylene oxide polymer F127, polyvinylpyrrolidone (PVP), hexadecyltrimethylammonium bromide (CTAB), alkoxylated fatty alcohol F86, polyoxyethylene ether (F108), and polyethylene glycol.

[0063] A method for adjusting the solid content of the core material to 20% to 30% includes adding an aqueous solution to the core material.

[0064] The method for dispersing and emulsifying the core material and the first coating material under the action of a first emulsifier to form a first emulsion includes: mixing the core material, the first coating material, and the first emulsifier, then dispersing them at high speed, and then uniformly emulsifying them using a high-pressure homogenizer to form the first emulsion. The high-speed dispersion is carried out at a stirring speed of 1000–15000 rpm for 1–60 min; the homogenization pressure is 10–80 MPa, and the homogenization is performed 1–5 times. The reaction temperature for forming the first emulsion is 80–200°C, and the reaction time is 0.5–20 h. The first emulsion is used in subsequent steps to form core-shell resin spheres.

[0065] Step S3: After spray drying the first emulsion, core-shell resin spheres are obtained. Each core-shell resin sphere comprises a core made of the core material and a first coating layer made of the first coating material and covering the core. The spray drying temperature is 100–300°C, and the outlet temperature of the equipment cavity for obtaining the core-shell resin spheres is 80–110°C. These temperature settings optimize the drying rate of the first emulsion and the rate of core-shell resin sphere formation.

[0066] In some embodiments of this application, after obtaining the core-shell resin ball, the method further includes: coating the surface of the core-shell resin ball with at least one layer of coating material, each layer of coating material comprising at least one resin material, the residual carbon content of the coating material being greater than that of the first coating material, and when there is more than one layer of coating material, the residual carbon content of the coating material increasing sequentially in the direction away from the surface of the core-shell resin ball.

[0067] A method for coating the surface of the core-shell resin ball with at least one coating material includes: adding a second coating material and a first organic solvent to the core-shell resin ball and mixing them evenly; and performing a spray drying treatment to form a second coating layer on the surface of the core-shell resin ball.

[0068] In some embodiments of this application, the first organic solvent includes one of water, 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.

[0069] In some embodiments of this application, the at least one coating material includes a second coating material and a third coating material that sequentially coat the core-shell resin sphere. The first coating material includes a first resin and at least one of a template agent and a fast ion conductor. The second coating material includes a first resin, a second resin, and at least one of a template agent and a fast ion conductor. The third coating material includes a second resin, a third resin, and at least one of a template agent and a fast ion conductor. The char residue and hydrophilicity of the first, second, and third resins are selected as needed, as long as the char residue of the outer coating material increases sequentially and the hydrophilicity of the at least one coating material is the same as that of the first coating material.

[0070] In some embodiments of this application, the at least one coating material includes a second coating material and a third coating material that sequentially coat the core-shell resin sphere. The first coating material includes a first resin and at least one of a template agent and a fast ion conductor. The second coating material includes a first resin, a third resin, and at least one of a template agent and a fast ion conductor. The third coating material includes a second resin, a third resin, and at least one of a template agent and a fast ion conductor.

[0071] Step S4: 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 into core-shell porous carbon microspheres. The structure of the core-shell porous carbon microspheres contains a certain amount of pores, which is beneficial for subsequent activation.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] This application also provides a core-shell porous carbon microsphere, formed by any of the above methods, comprising: a core porous carbon layer and a first coating porous carbon layer covering the core porous carbon layer, wherein the core porous carbon layer is formed by carbonization of the core material, and the first coating porous carbon layer is formed by carbonization of the first coating material.

[0079] This application also provides a silicon-carbon anode material, comprising: the aforementioned core-shell porous carbon microspheres and elemental silicon located within the pores of the core-shell porous carbon microspheres. Further, the silicon-carbon anode material also includes a carbon coating layer covering the core-shell porous carbon microspheres.

[0080] This application involves atomizing a first emulsion into small droplets using a spray device. Under the influence of a hot airflow, heat exchange occurs, causing the aqueous phase in the first emulsion to evaporate rapidly. Driven by hydrophobic interactions, the first coating material solidifies and shrinks, forming a "protective shell" on the surface of the core material, resulting in resin spheres with a capsule structure. Furthermore, spray drying offers advantages such as readily available equipment, low operating costs, good product weight, high production capacity, and a simple process, making it suitable for continuous, automated, large-scale industrial production.

[0081] By mixing resin materials with different char residue ratios, the shrinkage rates of these resin materials differ during high-temperature carbonization. Therefore, by controlling the amount of different resins used, cavitation or hollow structures can be generated between the layers of different resin materials, resulting in porous carbon microspheres with different core-shell structures. This improves the compaction and expansion properties of the porous carbon matrix. Simultaneously, template agents can be added to the resin materials to create pores and increase the mesopore content, thereby reducing the impact of slow ion dynamics in the micropores. Furthermore, doping elements can be added to the resin materials to modify them, 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 doping elements include nitrogen, phosphorus, boron, etc., to form modified resin materials.

[0082] 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.

[0083] Example 1

[0084] Preparation of core-shell porous carbon microspheres:

[0085] Preparation of S1, core material, and first coating material:

[0086] Non-hydrophilic thermoplastic phenolic resin with a residual carbon rate of 42% was heated and melted at 90°C with fast ion conductor carbon nanotubes (added at 0.03% of the resin weight) and mixed uniformly. After cooling, the mixture was pulverized to a particle size of 2μm. Urotropine (added at 8% of the resin weight) was added and mixed uniformly to obtain the core material.

[0087] The first coating material was obtained by uniformly mixing hydrophilic phenolic resin with a residual carbon rate of 46% with template agent F127 (added at 5% of the resin weight) and fast ion conductor carbon nanotubes (added at 0.05% of the resin weight). The weight ratio of the core material to the first coating material was 20:80.

[0088] S2. Synthesis of core-shell resin spheres:

[0089] The first coating material in S1 was added to the reactor. The solid content was adjusted to 30% by adding pure water and then mixed and stirred evenly. Sodium dodecyl sulfonate (0.5% of the weight of the first coating material) was added as an emulsifier and stirred. Then the core material was added and dispersed in a high-speed disperser at 6000 rpm for 10 min. Then it was homogenized three times by a high-pressure homogenizer at a pressure of 30 MPa. Finally, the solution was dried by spray drying at a rate of 15 mL / min with an inlet temperature of 170℃ and an outlet temperature of 80℃ to obtain core-shell resin balls.

[0090] S3. Synthesis of core-shell porous carbon microspheres:

[0091] The core-shell resin spheres were placed in a carbonization furnace and heated to 700°C at a rate of 1°C / min under a nitrogen protective atmosphere. The temperature was maintained at 700°C for 3 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 2 L / kg carbonized material / min to activate the carbon microspheres. After activation for 6 hours, the temperature was lowered to obtain porous carbon microspheres with a core-shell structure.

[0092] Preparation of silicon-carbon anode materials:

[0093] 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, 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 2.5 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. The structure of the silicon-carbon anode material is shown in Figure 2, comprising: 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 core porous carbon layer 10 and a first coating porous carbon layer 11 covering the core porous carbon layer. The core porous carbon layer is formed by carbonization of the core material, and the first coating porous carbon layer is formed by carbonization of the first coating material. The SEM image of the silicon-carbon anode material is shown in Figure 3. It should be noted that since both the core porous carbon layer 10 and the first coating porous carbon layer 11 are porous carbon and formed in the same carbonization step, the boundary between the core porous carbon layer 10 and the first coating porous carbon layer 11 is not clearly shown in Figure 3.

[0094] Example 2

[0095] Preparation of S1, core material, and first coating material:

[0096] A non-hydrophilic thermoplastic phenolic resin with a residual carbon content of 42% was heated and melted at 90°C and uniformly mixed with fast ion conductor carbon nanotubes (added at 0.03% of the resin weight). After cooling, the mixture was pulverized to a particle size of 2μm, and hexamethylenetetramine (added at 8% of the resin weight) was added and mixed uniformly to obtain the core material. A first coating material was obtained by uniformly mixing hydrophilic phosphorophenolic resin with a residual carbon content of 69%, hydrophilic phenolic resin with a residual carbon content of 59% (the weight ratio of the two resins was 70:30), template agent F127 (added at 5% of the resin weight), and fast ion conductor carbon nanotubes (added at 0.05% of the resin weight). The weight ratio of the core material to the first coating material was 15:85.

[0097] S2. Synthesis of core-shell resin spheres:

[0098] The first coating material in S1 was added to the reactor. The solid content was adjusted to 20% by adding pure water and then mixed and stirred evenly. The emulsifier polyvinyl alcohol (1.0% of the weight of the first coating material) was added and stirred. Then the core material was added and dispersed in a high-speed disperser at 6000 rpm for 10 min. Then it was homogenized twice by a high-pressure homogenizer at a pressure of 50 MPa. Finally, the solution was dried by spray drying at a rate of 20 mL / min with an inlet temperature of 180℃ and an outlet temperature of 80℃ to obtain core-shell resin balls.

[0099] S3. Synthesis of core-shell porous carbon microspheres:

[0100] 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. The temperature was maintained at 700°C for 2 hours and then cooled to room temperature to obtain carbonized material. The heating temperature was then increased to 900°C, and steam was introduced at a gas flow rate of 1.0 L / kg carbonized material / min to activate the carbon microspheres. After activation for 6 hours, the temperature was lowered to obtain porous carbon microspheres with a core-shell structure.

[0101] S4. Synthesis of silicon-carbon anode materials:

[0102] 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, 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 2.5 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.

[0103] Example 3

[0104] Preparation of S1, core material, and first coating material:

[0105] A non-hydrophilic thermoplastic phenolic resin with a residual carbon content of 42% was heated and melted at 90°C and uniformly mixed with fast ion conductor carbon nanotubes (added at 0.03% of the resin weight) and template agent P123 (added at 5% of the resin weight). After cooling, the mixture was pulverized to a particle size of 3 μm, and hexamethylenetetramine (added at 10% of the resin weight) was added and mixed uniformly to obtain the core material. A hydrophilic phenolic resin with a residual carbon content of 59% was uniformly mixed with template agent P123 (added at 8% of the resin weight) and fast ion conductor carbon nanotubes (added at 0.05% of the resin weight) to obtain the first coating material. A hydrophilic phosphorophenolic resin with a residual carbon content of 69% was uniformly mixed with template agent F127 (added at 10% of the resin weight) and fast ion conductor graphene (added at 0.02% of the resin weight) to obtain the second wall material. The weight ratio of the core material to the first coating material was 15:85.

[0106] S2. Synthesis of core-shell resin spheres:

[0107] The first coating material in S1 was added to the reactor, and the solid content was adjusted to 10% by adding pure water. After mixing and stirring evenly, sodium dodecyl sulfonate (1.5% of the weight of the first coating material) was added as an emulsifier and stirred. Then, the core material was added and dispersed in a high-speed disperser at 10,000 rpm for 10 min. Then, it was homogenized three times under a high-pressure homogenizer at 40 MPa. Finally, the solution was dried in a spray dryer at a rate of 10 mL / min with an inlet temperature of 180°C and an outlet temperature of 80°C to obtain resin balls. The second wall material was mixed and pure water was added to adjust the solid content to 20%. Then, the above resin balls were added and dispersed in a high-speed disperser at 10,000 rpm for 10 min. Then, it was homogenized three times under a high-pressure homogenizer at 40 MPa. Finally, the solution was dried in a spray dryer at a rate of 10 mL / min with an inlet temperature of 180°C and an outlet temperature of 80°C to obtain resin balls with a three-layer resin structure.

[0108] S3. Synthesis of core-shell porous carbon microspheres:

[0109] 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 sodium hydroxide were then mixed at a weight ratio of 1:2.5 and activated at 700°C for 2 hours. 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.

[0110] S4. Synthesis of silicon-carbon anode materials:

[0111] 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, 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 2.5 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.

[0112] Example 4

[0113] Preparation of S1, core material, and first coating material:

[0114] A non-hydrophilic thermoplastic epoxy resin with a residual carbon content of 36% and a non-hydrophilic thermoplastic phenolic resin with a residual carbon content of 42% (resin weight ratio of 40:60) were uniformly mixed with fast ion conductor carbon nanotubes (added at 0.03% of the resin weight) and template agent P123 (added at 5% of the resin weight) at 90°C. After cooling, the mixture was pulverized to a particle size of 3μm, and hexamethylenetetramine (added at 10% of the resin weight) was added and mixed uniformly to obtain the core material. A first coating material was obtained by uniformly mixing a hydrophilic phenolic resin with a residual carbon content of 59% and a hydrophilic phosphorophenolic resin with a residual carbon content of 69% (resin weight ratio of 50:50) with template agent P123 (added at 8% of the resin weight) and fast ion conductor carbon nanotubes (added at 0.05% of the resin weight). The weight ratio of the core material to the first coating material was 10:90.

[0115] S2. Synthesis of core-shell resin spheres:

[0116] The first coating material in S1 was added to the reactor. The solid content was adjusted to 10% by adding pure water and then mixed and stirred evenly. The emulsifier polyvinylpyrrolidone (1.5% of the weight of the first coating material) was added and stirred. Then the core material was added and dispersed in a high-speed disperser at 8000 rpm for 10 min. Then it was homogenized three times by a high-pressure homogenizer at a pressure of 30 MPa. Finally, the solution was dried by spray drying at a rate of 10 mL / min with an inlet temperature of 190℃ and an outlet temperature of 80℃ to obtain core-shell resin balls.

[0117] S3. Synthesis of core-shell porous carbon microspheres:

[0118] 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 was then mixed with potassium hydroxide at a weight ratio of 1:2 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.

[0119] S4. Synthesis of silicon-carbon anode materials:

[0120] 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, 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 2.5 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.

[0121] Example 5

[0122] S1. Preparation of the first coating material:

[0123] The first coating material was obtained by uniformly mixing hydrophilic boron phenolic resin with a residual carbon rate of 71% and hydrophilic phenolic resin with a residual carbon rate of 55% (the weight ratio of the two resins was 90:10), fast ion conductor carbon nanotubes (added at 0.03% of the resin weight), and template agent P123 (added at 5% of the resin weight).

[0124] S2. Synthesis of core-shell resin spheres:

[0125] The first coating material in S1 was added to the reactor. The solid content was adjusted to 35% by adding pure water and then mixed and stirred evenly. The emulsifier polyvinylpyrrolidone (3.5% of the weight of the first coating material) was added and stirred. The mixture was dispersed in a high-speed disperser at 8000 rpm for 10 min. Then, it was homogenized once by a high-pressure homogenizer at a pressure of 30 MPa. Finally, the solution was dried by spray drying at a rate of 20 mL / min with an inlet temperature of 200℃ and an outlet temperature of 90℃ to obtain resin balls.

[0126] S3. Synthesis of core-shell porous carbon microspheres:

[0127] 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 10 hours, the temperature was lowered to obtain porous carbon microspheres with a core-shell structure.

[0128] S4. Synthesis of silicon-carbon anode materials:

[0129] 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, 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 2.5 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.

[0130] Comparative Example 1

[0131] S1. Resin preparation:

[0132] The first resin material was obtained by uniformly mixing hydrophilic phenolic resin with a residual carbon rate of 55% with template agent P123 (added at 5% of the resin weight) and fast ion conductor carbon nanotubes (added at 0.05% of the resin weight).

[0133] S2. Synthesis of cured resin:

[0134] The first resin material in S1 is placed in a curing chamber and dried and cured at 150°C for 10 hours in an air atmosphere. Then, it is coarsely crushed to obtain the cured resin.

[0135] S3. Synthesis of porous carbon:

[0136] 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 weight ratio of 1:2. The temperature was increased to 750°C for activation for 1.5 hours. 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.

[0137] S4. Synthesis of silicon-carbon anode materials:

[0138] 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, 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 2.5 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.

[0139] Table 1

[0140] Table 2

[0141] Table 1 shows the specific surface area, pore volume, particle size, and mesopore ratio of the silicon-carbon anode materials formed in Examples 1-5 and Comparative Example 1 of this application. It can be seen from the table that Examples 1-5 can produce similar specific surface area, pore volume, and particle size as in Comparative Example 1, and their basic indicators are not affected by the method.

[0142] 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.

[0143] 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: A core material and a first coating material are prepared, both of which include a resin material. The char residue of the first coating material is greater than that of the core material, and the hydrophilicity of the resin material in the first coating material is opposite to that of the resin material in the core material. The solid content of the core material is adjusted to 20% to 30%, and the core material and the first coating material are dispersed and emulsified under the action of the first emulsifier to form a first emulsion; After spray drying the first emulsion, a core-shell resin ball is obtained. The core-shell resin ball includes a core made of the core material and a first coating layer made of the first coating material and covering the core. 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, After obtaining the core-shell resin spheres, the process further includes: coating the surface of the core-shell resin spheres with at least one layer of coating material, each layer of coating material comprising at least one resin material, the residual char rate of the coating material being greater than that of the first coating material, and when there is more than one layer of coating material, the residual char rate of the coating material increasing sequentially in the direction away from the surface of the core-shell resin spheres.

3. The method for preparing core-shell porous carbon microspheres according to claim 1, characterized in that, The weight ratio of the core material to the first coating material is 1:(1~10); the weight of the first emulsifier is 0.01% to 5% of the sum of the weights of the core material and the first coating material.

4. The method for preparing core-shell porous carbon microspheres according to claim 1, characterized in that, The core material comprises a first resin, and at least one of a template agent and a fast ion conductor. The char content of the first resin is between 20% and 45%. The weight percentages of the first resin, template agent, and fast ion conductor in the core material 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 first coating material comprises 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 first coating material are as follows: 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; or The first coating material comprises a third resin, and at least one of a template agent and a fast ion conductor, wherein the char residue of the third resin is between 61% and 90%, and the weight percentages of the third resin, template agent, and fast ion conductor in the first coating material are as follows: 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.

6. The method of claim 1, wherein the core-shell porous carbon microspheres are prepared by the steps of: The core material comprises a second resin, and at least one of a template agent and a fast ion conductor, wherein the carbon residue of the second resin is between 46% and 60%, and the weight percentages of the second resin, template agent, and fast ion conductor in the core material are as follows: 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; as well as The first coating material comprises a third resin, and at least one of a template agent and a fast ion conductor, wherein the char residue of the third resin is between 61% and 90%, and the weight percentages of the third resin, template agent, and fast ion conductor in the first coating material are as follows: 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.

7. The method for preparing core-shell porous carbon microspheres according to claim 2, characterized in that, The at least one coating material includes a second coating material and a third coating material that sequentially coat the core-shell resin sphere. The first coating material includes a first resin and at least one of a template agent and a fast ion conductor. The second coating material includes a first resin, a second resin, and at least one of a template agent and a fast ion conductor. The third coating material includes a second resin, a third resin, and at least one of a template agent and a fast ion conductor.

8. The method for preparing core-shell porous carbon microspheres according to claim 2, characterized in that, The at least one coating material includes a second coating material and a third coating material that sequentially coat the core-shell resin sphere. The first coating material includes a first resin and at least one of a template agent and a fast ion conductor. The second coating material includes a first resin, a third resin, and at least one of a template agent and a fast ion conductor. The third coating material includes a second resin, a third resin, and at least one of a template agent and a fast ion conductor.

9. The method for preparing core-shell porous carbon microspheres according to claim 1, characterized in that, The method of dispersing and emulsifying the core material and the first coating material under the action of the first emulsifier to form a first emulsion includes: mixing the core material, the first coating material and the first emulsifier, dispersing them at high speed, and then emulsifying them uniformly to form the first emulsion.

10. The method for preparing core-shell porous carbon microspheres according to claim 2, characterized in that, A method for coating the surface of the core-shell resin ball with at least one coating material includes: adding a second coating material and a first organic solvent to the core-shell resin ball and mixing them evenly; and performing a spray drying treatment to form a second coating layer on the surface of the core-shell resin ball.

11. The method for preparing core-shell porous carbon microspheres according to claim 10, characterized in that, The first organic solvent includes at least one of water, 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.

12. The method for preparing core-shell porous carbon microspheres according to any one of claims 5 to 8, 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 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. The method for preparing core-shell porous carbon microspheres according to claim 1, characterized in that, The first emulsifier comprises one or more 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. The amount of the first emulsifier added is 0.1 wt.% to 10 wt.% of the total weight of the resin material in the core material and the first coating material.

15. A method for preparing a silicon-carbon negative electrode material, characterized by, include: Using the core-shell porous carbon microspheres as described in any one of claims 1 to 14 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.

16. The method of producing a silicon-carbon negative electrode material according to claim 15, characterized by, The method further includes forming a carbon coating layer on the surface of the silicon-carbon anode material.

17. The method of producing a silicon-carbon negative electrode material according to claim 15, characterized by, 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.

18. A core-shell porous carbon microsphere formed by any one of the methods of claims 1 to 14, characterized in that, include: The core porous carbon layer and the first coated porous carbon layer covering the core porous carbon layer, wherein the core porous carbon layer is formed by carbonization of the core material and the first coated porous carbon layer is formed by carbonization of the first coating material.

19. A silicon-carbon negative electrode material formed using any one of the methods of claims 15 to 17, characterized in that, include: Core-shell porous carbon microspheres and elemental silicon located within the pores of the core-shell porous carbon microspheres.

20. The silicon-carbon negative electrode material of claim 19, wherein, Also includes: A carbon coating layer that covers the core-shell porous carbon microspheres.

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