Spherical silicon-based composite material, preparation method thereof, negative electrode and battery

Abstract

The invention provides a spherical silicon-based composite material and a preparation method thereof, a negative electrode and a battery, and relates to the technical field of silicon-based composite materials, the spherical silicon-based composite material comprises phenolic resin microspheres, a conductive agent and silicon nanoparticles, the phenolic resin microspheres are doped with the conductive agent to form a matrix of the spherical silicon-based composite material, and the silicon nanoparticles are doped with the conductive agent to form the spherical silicon-based composite material. The phenolic resin microspheres are of a regular spherical structure, grooves or protrusions or the combination of the grooves and the protrusions are arranged on the outer surfaces of the phenolic resin microspheres, the conductive agent is evenly dispersed in the phenolic resin microspheres, and part of the conductive agent is dispersed on the outer surfaces of the phenolic resin microspheres. The matrix is activated to form porous carbon microspheres with discontinuous porous channels or pores, and the silicon nanoparticles are deposited in the porous channels or pores. The problems that the ion conduction rate of the spherical silicon-based composite material is reduced and the conductivity is reduced can be solved, so that the first efficiency and the cycle stability of the spherical silicon-based composite material are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicon-based composite materials, in particular to a spherical silicon-based composite material, a preparation method thereof, a negative electrode and a battery. BACKGROUND

[0002] With the rapid development of lithium ion batteries, the specific capacity of graphite negative electrode materials on the market has approached its theoretical value of 372 mAh / g, and the theoretical specific capacity of silicon in new silicon-carbon negative electrode materials reaches 4200 mAh / g, and it has attracted widespread attention in the lithium battery industry due to its low lithium intercalation potential (0.4-0.6 V) and abundant reserves (26.4% in the earth's crust). The current silicon-carbon negative electrode is mostly a composite of carbon and silicon, and the precursor carbon material is mostly carbonized, crushed and classified from biomass and / or resin, etc., which has a sharp cross section, resulting in piercing the copper foil during coating and preparation of the battery cell, which has a great safety hazard. At the same time, it is found that during the pressure test, the irregular particles have a pulverization phenomenon, which exposes the coated silicon particles, ultimately leading to a decrease in the electrochemical performance of the material.

[0003] To solve the above problems, a spherical silicon-carbon negative electrode material is developed, and a smooth spherical structure is obtained. However, it is found that the microspheres are in point contact with each other, the contact area is too small, especially after swelling, the volume of some microspheres cannot be reduced, resulting in a decrease in the initial efficiency and a decrease in the conductivity of the spherical silicon-carbon material.

[0004] Therefore, the present application is proposed. SUMMARY

[0005] One of the purposes of the present application is to provide a spherical silicon-based composite material to solve the problem of a decrease in ion conduction rate and a decrease in conductivity caused by a large decrease in the contact area between particles after swelling in the prior art, thereby improving the initial efficiency and cycle stability of the spherical silicon-based composite material.

[0006] The second purpose of the present application is to provide a preparation method of a spherical silicon-based composite material.

[0007] The third purpose of the present application is to provide a negative electrode.

[0008] The molecular structure and element type of the negative electrode material, and the fourth purpose of the present application is to provide a battery.

[0009] In order to achieve the above purposes of the present application, the following technical solutions are adopted: The first aspect of the present invention provides a spherical silicon-based composite material, comprising phenolic resin microspheres, a conductive agent, and silicon nanoparticles. The phenolic resin microspheres, after being incorporated with the conductive agent, form the matrix of the spherical silicon-based composite material. The phenolic resin microspheres have a regular spherical structure with no grooves or protrusions or a combination of both on their outer surface. The conductive agent is uniformly dispersed inside the phenolic resin microspheres and partially dispersed on the outer surface of the phenolic resin microspheres. After activation, the matrix forms porous carbon microspheres with discontinuous porous channels or pores, and the silicon nanoparticles are deposited in the porous channels or pores.

[0010] Compared with the prior art, the principles and beneficial effects of the present invention are as follows: The conductivity of silicon-carbon anode materials has a significant impact on battery performance, including initial efficiency, cycle performance, and rate capability. Traditional silicon-carbon anode materials are often doped with various carbon-based conductive agents to improve conductivity. Based on this experience, before preparing microspheres using phenolic resin, we first uniformly distribute carbon-based conductive agents in the resin solution. We then use emulsion polymerization to obtain spherical silicon-carbon anode materials doped with conductive agents. This ensures that a large amount of the conductive agent is embedded within the silicon-carbon anode material, with a small amount remaining on the surface. With the synergistic effect of graphene and other materials, this improves the conductivity of the silicon anode material, thus mitigating the problems of decreased initial efficiency and cycle performance caused by spherical materials.

[0011] Furthermore, the particle size distribution of the phenolic resin microspheres is 0.5~100μm, and the median particle size Dv50 is distributed in the range of 3~15μm; preferably, the particle size distribution of the phenolic resin microspheres is 2~20μm, and the median particle size Dv50 is distributed in the range of 7~12μm.

[0012] Furthermore, the conductive agent is one or more of nano-carbon materials and nanoparticles, wherein the nano-carbon material has a one-dimensional or two-dimensional structure, and the nano-carbon material includes, but is not limited to, carbon black, conductive graphite, vapor-grown carbon fiber (VGCF), carbon nanotubes, and graphene; preferably, the nano-carbon material includes one or more of acetylene black (ACET), Super P, highly conductive carbon black, graphite microcrystals, single-walled carbon nanotubes, multi-walled carbon nanotubes, and activated carbon fibers; the nanoparticles are conductive metal elements such as Cu, Ag, Al, Zn, and Zr, and their compounds.

[0013] Beneficial effects: In this technical solution, nano-carbon materials can contact active materials from different dimensions such as points, lines and surfaces to build conductive mesh channels, while nanoparticles provide conductive particles. Both can effectively improve the specific capacity, first efficiency and cycle performance of silicon-based anode materials.

[0014] Furthermore, based on the content of the phenolic resin microspheres being 100%, the content of the conductive agent is 0.001~15wt%, and the size is 50~800nm, which can be uniformly dispersed inside the spheres, increasing the contact area with the active material and ensuring consistent material performance; preferably, based on the content of the phenolic resin microspheres being 100%, the content of the conductive agent is 0.005~5wt%.

[0015] Beneficial effects: In this technical solution, different contents of conductive agent have different effects on improving the capacity, first efficiency and cycle performance of spherical silicon anode material. Therefore, the content of conductive agent is limited to ensure the best effect on improving the conductivity of spherical silicon anode material.

[0016] Furthermore, the silicon content in the silicon-based composite material is 5-90%; preferably, the silicon content in the silicon-based composite material is 30-70%. And / or, the spherical silicon-based composite material has a specific surface area of ​​0.1~55 m2 / g and a pore volume of 0.001~0.1 cm3 / g; preferably, the spherical silicon-based composite material has a specific surface area of ​​0.5~10 m2 / g and a pore volume of 0.001~0.05 cm3 / g.

[0017] A second aspect of the present invention provides a method for preparing spherical silicon-based composite materials, the method comprising: Step S1: Provide a powdered conductive agent with a content of 0.001~15wt%. Disperse the conductive agent powder in a dispersant solution, stir evenly, and then add it to a phenolic solution and stir evenly. In step S2, after the dispersant solution is completely dissolved, phenolic liquid is added, and after stirring evenly, the mixed solution from S1 is added to the above solution, and the mixture is stirred, heated, cured and dried to obtain phenolic resin microspheres containing conductive agent. Step S3: Under high temperature and inert atmosphere, the phenolic resin microspheres in S2 are carbonized and activated to obtain porous carbon microspheres. In step S4, the porous carbon microspheres from S3 are brought into contact with the silicon-containing precursor under high temperature and inert atmosphere to perform silicon deposition.

[0018] Further, the specific process in step S2 is as follows: after the dispersant solution is completely dissolved, phenolic liquid is added and stirred evenly. The mixed solution in S1 is added to the above solution and stirred and heated to 50~100℃, and kept at this temperature for 0.2~2 hours. The curing agent is dissolved in water and added to the solution system of phenolic resin, conductive agent and dispersant. The temperature is kept at 70~100℃ for 1~10 hours. After the reaction is completed, the sedimentation is allowed to continue for 12~48 hours and the upper layer is discarded. The mixture is then dried at 80℃ for 24 hours to obtain conductive agent-doped phenolic resin microspheres. The specific process in step S3 is as follows: the phenolic resin microspheres in S2 are carbonized at 500~800℃ in an inert atmosphere for 1~3 hours to obtain carbon microspheres, and then water-activated at 700~850℃ in an inert atmosphere for 1~3 hours to obtain porous carbon microspheres. The specific process in step S4 is as follows: the porous carbon microspheres in S3 are brought into contact with a silicon-containing precursor for silicon deposition in an inert atmosphere at 150~1000℃ for 1~100 hours.

[0019] Furthermore, the dispersant in steps S1 and S2 is selected from one or more of polyethylene glycol, paraffin wax, Span-80, Tween-80, polyvinyl alcohol 1788, polyvinyl alcohol 1799, polyvinyl alcohol 2499, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide (CTAB).

[0020] A third aspect of the present invention provides a negative electrode, wherein the active material of the negative electrode comprises the above-described spherical silicon-based composite material and the spherical silicon-based composite material obtained by the above-described preparation method.

[0021] A fourth aspect of the present invention provides a battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode comprises a negative electrode active material comprising the above-described spherical silicon-based composite material and the spherical silicon-based composite material obtained by the above-described preparation method. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 Here is a SEM image of the phenolic resin microspheres in Example 1; Figure 2 This is a magnified view of a portion of the phenolic resin microspheres in Example 1. Detailed Implementation

[0024] The embodiments and examples of the present invention will be described in detail below with reference to the implementation methods and examples. However, those skilled in the art will understand that the following implementation methods and examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The first aspect of this invention provides a spherical silicon-based composite material, comprising phenolic resin microspheres, a conductive agent, and silicon material. The phenolic resin microspheres, after being incorporated with the conductive agent, form the matrix of the spherical silicon-based composite material. The phenolic resin microspheres have a regular spherical structure, with no grooves, protrusions, or a combination of both on their outer surface. Furthermore, the phenolic resin microspheres have a uniform internal diameter. The conductive agent is uniformly dispersed inside the phenolic resin microspheres, and partially dispersed on the outer surface of the phenolic resin microspheres. Specifically, a small amount of the conductive agent is dispersed on the surface of the microspheres. After activation, the matrix forms discontinuous porous channels or pores with a high specific surface area. The silicon material is deposited within the porous channels or pores.

[0026] The conductive agent is one or more of nano-carbon materials and nanoparticles. The nano-carbon materials have a one-dimensional or two-dimensional structure, including but not limited to carbon black, conductive graphite, vapor-grown carbon fiber (VGCF), carbon nanotubes, and graphene; preferably, they are selected from one or more of acetylene black (ACET), Super P, highly conductive carbon black, graphite microcrystals, single-walled carbon nanotubes, multi-walled carbon nanotubes, and activated carbon fibers. The nanoparticles are one or more of conductive elemental metals and their compounds, selected from one or more of Cu, Ag, Al, Zn, and Zr. In this technical solution, the nano-carbon materials can contact the active material from different dimensions such as points, lines, and surfaces to build a conductive mesh channel, while the nanoparticles provide conductive particles. Both can effectively improve the specific capacity, first-efficiency, and cycle performance of silicon-based anode materials.

[0027] In some preferred embodiments, the phenolic resin microspheres have a particle size distribution of 0.5–100 μm and a median particle size Dv50 distribution of 3–15 μm. Typical but non-limiting particle sizes can be, for example, 0.5 μm, 1 μm, 4 μm, 8 μm, 16 μm, 30 μm, 50 μm, 70 μm, 900 μm, and 100 μm, and typical but non-limiting median particle size Dv50 can be, for example, 3 μm, 5 μm, 7 μm, 10 μm, 13 μm, and 15 μm. However, this is not a limitation; more preferably, the phenolic resin microspheres have a particle size distribution of 2–20 μm and a median particle size Dv50 distribution of 7–12 μm, which is more conducive to meeting application requirements.

[0028] In some preferred embodiments, the phenolic resin microspheres comprise 100% of the total content, and the conductive agent comprises 0.001 to 15 wt%. However, this is not a limitation; more preferably, the conductive agent comprises 0.005 to 5 wt% of the total content of the phenolic resin microspheres. In this technical solution, different contents of conductive agent have varying effects on improving the capacity, first-efficiency performance, and cycle performance of the spherical silicon anode material. Therefore, limiting the content of the conductive agent ensures the optimal effect on improving the conductivity of the spherical silicon anode material.

[0029] In some preferred embodiments, the silicon content in the silicon-based composite material is 5% to 90%. Typical, but not limiting, silicon content ratios can be, for example, 5%, 8%, 16%, 25%, 40%, 60%, 80%, and 90%. However, it is not limited to these, and it is further preferred that the silicon content in the silicon-based composite material is 30% to 70%. And / or, the specific surface area of ​​the spherical silicon-based composite material is 0.1~55 m² / g, and the pore volume is 0.001~0.1 cm³ / g. Typical, but not limiting, specific surface areas can be, for example: 0.1 m² / g, 0.2 m² / g, 0.5 m² / g, 1 m² / g, 2 m² / g, 4 m² / g, 8 m² / g, 16 m² / g, 30 m² / g, 50 m² / g; and pore volumes can be, for example: 0.001 cm³ / g, 0.002 cm³ / g, 0.005 cm³ / g, 0.01 cm³ / g, 0.05 cm³ / g, 0.1 cm³ / g. However, this is not limited to these, and it is further preferred that the specific surface area of ​​the spherical silicon-based composite material is 0.5~10 m² / g, and the pore volume is 0.001~0.05 cm³ / g.

[0030] A second aspect of the present invention provides a method for preparing spherical silicon-based composite materials, the method comprising: Step S1: Provide conductive agent powder, disperse the conductive agent powder in a dispersant solution, stir evenly, and then add it to a phenolic solution and stir evenly. Step S2: Prepare a dispersant solution, add phenolic liquid and stir evenly, add the mixed solution from S1, stir and heat to 50~100℃, keep warm for 0.2~2 hours, dissolve the curing agent in water and add it to the solution system of phenolic resin, conductive agent and dispersant, keep warm at 70~100℃ for 1~10 hours, after the reaction is completed, let it settle for 12~48 hours and pour off the upper liquid, dry at 80℃ for 24 hours to obtain conductive agent doped phenolic resin microspheres; Step S3: Carbonize the phenolic resin microspheres from S2 at 500-800℃ for 1-3 hours under an inert atmosphere to obtain carbon microspheres, and then activate them with water at 700-850℃ for 1-3 hours under an inert atmosphere to obtain porous carbon microspheres. In step S4, the porous carbon microspheres from S3 are brought into contact with a silicon-containing precursor under an inert atmosphere at 150~1000℃ to deposit silicon for 1~100 hours.

[0031] In some preferred embodiments, the dispersant in steps S1 and S2 is selected from one or more of polyethylene glycol, paraffin wax, Span-80, Tween-80, polyvinyl alcohol 1788, polyvinyl alcohol 1799, polyvinyl alcohol 2499, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide (CTAB). In the embodiments of the present invention, polyethylene glycol is selected as the dispersant.

[0032] A third aspect of the present invention provides a negative electrode, wherein the active material of the negative electrode comprises the above-described spherical silicon-based composite material and the spherical silicon-based composite material obtained by the above-described preparation method.

[0033] A fourth aspect of the present invention provides a battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode comprises a negative electrode active material, and the negative electrode active material comprises the above-described spherical silicon-based composite material and the spherical silicon-based composite material obtained according to the above-described preparation method.

[0034] The present invention is further illustrated below with specific embodiments and comparative examples. However, it should be understood that these embodiments are merely for illustrative purposes and should not be construed as limiting the invention in any way. Unless otherwise specified, the raw materials used in the embodiments and comparative examples of the present invention were carried out under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products. Example 1

[0035] Step S1: Weigh 0.1g of polyethylene glycol, disperse it in 20g of water, heat and stir for 1 hour, add 0.024g of hydroxylated multi-walled carbon nanotubes and stir for 1 hour to obtain a uniformly dispersed conductive agent solution. Add 30g of resin solution at room temperature and stir for 1 hour. Step S2: Weigh 0.3 g of polyethylene glycol, disperse it in 100 g of water, heat to 70 °C and stir until homogeneous. Add the mixed solution from reaction S1, raise the temperature to 95 °C, and stir for 2 hours. Add 2 g of hexamethylenetetramine, and continue stirring for 4 hours until the reaction is complete. Pour off the solution and allow it to settle for 72 hours. Dry at 80 °C to obtain conductive agent-doped resin microspheres. The powder sample is green. The electron microscopy results are as follows: Figure 1 As shown, obvious carbon nanotubes can be observed; In step S3, the resin microspheres from S2 were carbonized at 600°C for 2 hours under a nitrogen atmosphere, ground, and then sieved through a 200-mesh sieve. They were then activated with water at 800°C for 2 hours at a water flow rate of 5 ml / min to obtain porous carbon material. The particle size, specific surface area, and pore volume are shown in Table 1.

[0036] Step S4: The porous material was placed in a tube furnace and heated from room temperature to 580°C at a rate of 5°C / min in a N2 atmosphere. Then, the temperature was changed to a 25% SiH4-N2 mixed gas and maintained at 580°C for 18 hours in the 25% SiH4-N2 mixed atmosphere. After changing to a N2 atmosphere, the material was allowed to cool naturally, crushed, and graded to obtain a silicon-based anode material. The silicon content in the obtained silicon-based anode material was 48.9 wt.%, the specific surface area was 2.38 m2 / g, and the pore volume data are shown in Table 2. The obtained silicon-based anode material was used to prepare a button cell to characterize its electrochemical performance, and the data are shown in Tables 3 and 4. Example 2

[0037] The preparation steps in this embodiment are the same as in Example 1, except that graphene oxide is used instead of hydroxylated multi-walled carbon nanotubes in Example 1, and the amount of conductive agent is 0.024g. Example 3

[0038] The preparation steps in this embodiment are the same as those in Example 1, except that acetylene black (ACET) is used instead of the hydroxylated multi-walled carbon nanotubes in Example 1, and the amount of conductive agent is 0.024g. Example 4

[0039] The preparation steps in this embodiment are the same as those in Example 1, except that: nano copper powder is used instead of hydroxylated multi-walled carbon nanotubes in Example 1, and the amount of conductive agent is 0.024g. Example 5

[0040] The preparation steps S2, S3, and S4 of this embodiment are the same as those in Example 1, except that: in step S1, 0.1g of polyethylene glycol is weighed, dispersed in 20g of water, heated and stirred for 1 hour, cooled to room temperature, 0.012g of hydroxylated multi-walled carbon nanotubes are added and stirred for 1 hour, then 0.012g of graphene oxide is added and stirred for another hour to obtain a uniformly dispersed conductive agent mixed solution. Then, 30g of resin solution is added at room temperature and stirred for 1 hour. Comparative Example 1

[0041] Steps S2, S3, and S4 in this comparative example are the same as in Example 1, except that no conductive agent is added in step S1, thus obtaining a spherical silicon-based composite material without any conductive agent. Comparative Example 2

[0042] Steps S2, S3, and S4 in this comparative example are the same as in Example 1, except that the mass of the conductive agent hydroxylated multi-walled carbon nanotubes in step S1 is 0.012 g.

[0043] Using the silicon-based composite materials prepared in the examples and comparative examples as the negative electrode active material, negative electrode sheets were prepared respectively. CR2032 coin cells were fabricated using conventional methods, and the electrical performance of the cells was tested. The specific testing methods are as follows: (1) Half-cell assembly: Assemble CR2032 button cells in a glove box, with lithium metal sheet as counter electrode, polypropylene microporous membrane as separator, and LiPF6 dissolved in a mixture of ethyl carbonate (EC) and diethyl carbonate (DEC) (volume ratio EC:DEC=1:1), wherein the concentration of LiPF6 is 1mol / L.

[0044] The battery was tested for charge and discharge using the LAND battery testing system.

[0045] (2) Cyclic specific capacity and initial efficiency test: After the CR2032 button cell was left to stand for 6 hours, it was discharged at 0.1C to 0.005V and the capacity was recorded as Q1; then it was discharged at a constant voltage of 0.005V until the current was cut off at 0.01C and the total capacity was recorded as Q2; after standing for 5 minutes, it was charged at a constant current of 0.1C to 1.5V; the initial delithiation specific capacity is the specific capacity (or mass specific capacity) of the electrode material, and the ratio of the initial delithiation capacity to the initial lithium insertion capacity is the initial coulombic efficiency of the battery.

[0046] The data obtained from the above embodiments and comparative examples are shown in Tables 1, 2, 3 and 4 below. Table 1 is the micropore data table for conductive agent-modified porous carbon, Table 2 is the micropore data table for conductive agent-modified spherical silicon-based anode material, Table 3 is the electrochemical data table for conductive agent-doped spherical silicon-carbon anode, and Table 4 is the charge-discharge data table for conductive agent-doped spherical silicon-carbon anode.

[0047] Item Dv10 (pm) Dv50 (pm) Dv99 (pm) Concentration Specific surface Pore volume Pore ratio Example 1 3.4 10.2 14.5 1.10 1922 0.72 91% Example 2 3.8 8.9 14.1 0.97 1879 0.80 89% Example 3 3.3 9.1 14.3 1.08 1853 0.78 87% Example 4 3.6 9.4 14.9 1.12 1955 0.73 87% Example 5 3.4 10.3 15.1 0.96 1848 0.76 88% Comparative Example 1 3.2 9.1 14.6 1.10 1876 0.75 90% Comparative Example 2 3.5 9.6 13.8 1.07 1856 0.73 92% Table 1 (Data sheet of conductive agent modified porous carbon microspheres) Item Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Pore volume (cm3 / g) 0.020 0.040 0.041 0.013 0.021 0.010 0.030 Specific surface area (m2 / g) 1.200 0.811 0.788 0.524 1.180 0.483 1.400 Table 2 (Micropore Data of Conductive Agent Modified Spherical Silicon-Based Anode Material) Item 1.5V initial coulombic efficiency (%) 1.5V gravimetric capacity (mAh / g) 0.8V initial coulombic efficiency (%) 0.8V gravimetric capacity (mAh / g) Resistivity Example 1 92.1% 1982 83.0% 1515 1.4 Example 2 92.8% 1949 84.1% 1521 1.6 Example 3 91.5% 1943 82.3% 1463 1.3 Example 4 92.3% 1905 83.4% 1466 1.4 Example 5 93.2% 2032 84.9% 1608 1.0 Comparative Example 1 85.6% 1820 70.0% 1091 2.5 Comparative Example 2 85.9% 1920 82.1% 1354 1.5 Table 3 (Electrochemical Data Table for Conductive Agent-Doped Spherical Silicon-Carbon Anode) Item 0.1C charge 0.5C charge 1C charge 0.1C discharge 0.5C discharge 1C discharge Example 1 100% 85.5% 80.4% 100% 85.4% 71.5% Example 2 100% 85.4% 80.1% 100% 85.7% 71.2% Example 3 100% 85.1% 80.7% 100% 86.0% 71.1% Example 4 100% 85.6% 81.0% 100% 85.1% 71.8% Example 5 100% 86.1% 81.3% 100% 86.2% 72.4% Comparative Example 1 100% 84.3% 79.5% 100% 83.8% 70.1% Comparative Example 2 100% 84.9% 80.1% 100% 85.1% 70.9% Table 4 (Charge-Discharge Data Table for Conductive Agent-Doped Spherical Silicon-Carbon Anodes) The data above show that, compared with unmodified spherical anode materials, spherical anode materials doped with carbon nanotubes and other substances exhibit significantly improved specific capacity and initial efficiency, and decreased resistivity. After rate charge-discharge, the specific capacity at the same rate is significantly increased by 1-2%. In Example 5, the combined use of hydroxylated multi-walled carbon nanotubes and graphene oxide resulted in a particularly significant improvement in conductivity. The study found that in silicon-carbon anode materials prepared from unmodified resin microspheres, the original spheres are in point contact, leading to limited ion transport. This results in the inability to retain capacity and cycle performance while maintaining the integrity of the anode material. However, by modifying the resin microspheres with conductive agents, new conductive agents are added inside and on the surface of the microspheres to act as ion transport channels, increasing the ion transport area and shortening the transport channels, significantly improving conductivity. Furthermore, the embodiments of this invention also ensure that the modified microspheres still meet the particle size requirements for silicon-carbon anode materials, showing broad application prospects in improving the capacity and cycle performance of silicon-carbon anode materials.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A spherical silicon-based composite material, characterized by, The spherical silicon-based composite material comprises phenolic resin microspheres, conductive agent and silicon nanoparticles. The phenolic resin microspheres form a matrix of the spherical silicon-based composite material after being mixed with the conductive agent. The phenolic resin microspheres have a regular spherical structure without grooves or protrusions or a combination of both on the outer surface. The conductive agent is uniformly dispersed in the interior of the phenolic resin microspheres and partially dispersed on the outer surface of the phenolic resin microspheres. The matrix forms porous carbon microspheres with discontinuous porous channels or pores after being activated. The silicon nanoparticles are deposited in the porous channels or pores.

2. The spherical silicon-based composite material of claim 1, wherein The particle size distribution of the phenolic resin microspheres is 0.5-100 μm, and the median particle size Dv50 distribution is 3-15 μm. Preferably, the particle size distribution of the phenolic resin microspheres is 2-20 μm, and the median particle size Dv50 distribution is 7-12 μm.

3. The spherical silicon-based composite material of claim 1, wherein, The conductive agent comprises one or more of nano-carbon materials and nano-particles. The nano-carbon materials have one-dimensional or two-dimensional structures and include, but are not limited to, carbon black, conductive graphite, vapor grown carbon fiber (VGCF), carbon nanotube and graphene. Preferably, the nano-carbon materials include one or more of acetylene black (ACET), Super P, special conductive carbon black, graphite microcrystal, single-walled carbon nanotube, multi-walled carbon nanotube and activated carbon fiber. The nano-particles are one or more of conductive metal elements and compounds thereof, and include, but are not limited to, Cu, Ag, Al, Zn and Zr.

4. The spherical silicon-based composite material of claim 1, wherein, The content of the conductive agent is 0.001-15 wt% based on 100% of the content of the phenolic resin microspheres. Preferably, the content of the conductive agent is 0.005-5 wt%.

5. The spherical silicon-based composite material of claim 1, wherein The content of silicon in the spherical silicon-based composite material is 5-90% based on 100% of the content of the spherical silicon-based composite material. Preferably, the content of silicon in the spherical silicon-based composite material is 30-70%. The specific surface area of the spherical silicon-based composite material is 0.1-55 m2 / g, and the pore volume is 0.001-0.1 cm3 / g. Preferably, the specific surface area of the spherical silicon-based composite material is 0.5-10 m2 / g, and the pore volume is 0.001-0.05 cm3 / g.

6. A method for preparing the spherical silicon-based composite material according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: S1. Providing a conductive agent in powder form, dispersing the conductive agent powder in a dispersant solution, stirring uniformly, adding a phenolic solution and stirring uniformly; S2. Providing another portion of the dispersant solution, adding a phenolic liquid, stirring uniformly, adding the mixed solution in S1, and stirring, heating, solidifying and drying to obtain phenolic resin microspheres containing the conductive agent; S3. Carbonizing and activating the phenolic resin microspheres in S2 under high temperature and inert atmosphere to obtain porous carbon microspheres; S4. Contacting the porous carbon microspheres in S3 with a silicon-containing precursor under high temperature and inert atmosphere to deposit silicon and obtain a spherical silicon-based composite material.

7. The method of claim 6, wherein the silicon-based composite material is a spherical silicon-based composite material. The specific process in the step S2: configure the dispersant solution, add the phenolic liquid and stir uniformly, add the mixed solution in S1 and stir and heat to 50~100℃, keep for 0.2~2 hours, add the solidified agent aqueous solution, keep at 70~100℃ for 1~10 hours, after the reaction is finished, settle for 12~48 hours, pour off the upper liquid, dry at 80℃ for 24 hours, and obtain the conductive agent doped phenolic resin microspheres; The specific process in the step S3: carbonize the phenolic resin microspheres in S2 at 500~800℃ under inert atmosphere for 1~3 hours, and obtain the carbon microspheres, and activate at 700~850℃ under inert atmosphere for 1~3 hours to obtain the porous carbon microspheres; The specific process in the step S4: contact the porous carbon microspheres in S3 with the silicon precursor at 150~1000℃ under inert atmosphere for 1~100 hours to deposit silicon, and obtain the spherical silicon-based composite material.

8. The method of claim 6 or 7, wherein the method further comprises the step of: The dispersant in the steps S1 and S2 is selected from one or more of polyethylene glycol, paraffin, Span-80, Tween-80, polyvinyl alcohol 1788, polyvinyl alcohol 1799, polyvinyl alcohol 2499, sodium dodecyl sulfate, cetyltrimethylammonium bromide (CTAB).

9. A negative electrode characterized by comprising: The active material of the negative electrode comprises the spherical silicon-based composite material according to any one of claims 1-5 and the spherical silicon-based composite material obtained by the preparation method according to any one of claims 6~8.

10. A battery characterized by The battery comprises a positive electrode, a negative electrode, a separator and an electrolyte, the negative electrode comprises a negative electrode active material, and the negative electrode active material comprises the spherical silicon-based composite material according to any one of claims 1-5 and the spherical silicon-based composite material obtained by the preparation method according to any one of claims 6~8.

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