Composite silicon-carbon material, preparation method, application and lithium ion battery thereof

Abstract

The application discloses a kind of composite silicon-carbon materials and its preparation method, application and lithium ion battery, it includes the following steps: S1, carbon sphere precursor is heat treated, carbonization treatment and activation treatment, and obtain porous carbon sphere;The carbon sphere precursor includes carbon source and transition metal-containing polymer nanosphere;The transition metal-containing polymer nanosphere includes polymer nanosphere matrix and transition metal coating;S2, using first chemical vapor deposition, the porous carbon sphere is deposited silicon, and obtain silicon-carbon material precursor;S3, using second chemical vapor deposition, the silicon-carbon material precursor is deposited carbon;Remove transition metal, and obtain composite silicon-carbon material.The obtained composite silicon-carbon material has higher silicon loading and excellent stability and conductivity, and the lithium ion battery using the composite silicon-carbon material has excellent capacity performance, and can balance excellent cycle performance and initial efficiency.

Description

TECHNICAL FIELD

[0001] The application provides a composite silicon-carbon material, a preparation method, application and lithium ion battery thereof. BACKGROUND

[0002] Porous carbon materials are widely used in catalyst carriers, energy storage materials, separation materials and other fields due to their high specific surface area, high adsorption and other characteristics. Among them, spherical porous carbon has attracted widespread attention due to its regular structure and good stability. However, the preparation method of traditional spherical porous carbon often needs high-temperature treatment, which is high in cost, and the pore size and porosity of the obtained porous carbon are not easy to control. When applied in the technical field of preparing silicon-carbon materials, the cost is high, and the silicon-carbon material has poor conductivity and low silicon loading.

[0003] The existing solutions mainly introduce nickel metal into the porous carbon by chemical vapor deposition method, sol-gel method and other methods, and combine silica and other template agents to perform pore-forming on the carbon source to obtain spherical porous carbon, thereby improving the conductivity and silicon loading of the silicon-carbon material. However, these methods usually require high-temperature treatment, and the steps are complex. Moreover, the distribution of the obtained nickel metal in the porous carbon is uneven, which may affect the performance of the doped nickel spherical porous carbon obtained finally, and thus the conductivity and silicon loading of the silicon-carbon material are still poor. Therefore, how to prepare spherical porous carbon with good performance under the conditions of low cost and simple operation, and then obtain silicon-carbon material with good conductivity and high silicon loading, is an important challenge in the current technology. SUMMARY

[0004] In order to solve the defects of low silicon loading and poor conductivity of the silicon-carbon material obtained based on the porous carbon spheres prepared by the template method in the prior art, the application provides a composite silicon-carbon material, a preparation method, application and lithium ion battery thereof. The obtained composite silicon-carbon material has high silicon loading and excellent stability and conductivity. The lithium ion battery using the composite silicon-carbon material has excellent capacity performance, and can balance excellent cycle performance and first efficiency.

[0005] To achieve the above object, the application adopts the following technical solutions.

[0006] The application provides a preparation method of a composite silicon-carbon material, which comprises the following steps:

[0007] S1, performing heat treatment, carbonization treatment and activation treatment on a carbon sphere precursor to obtain a porous carbon sphere; the carbon sphere precursor comprises a carbon source and a transition metal-containing polymer nanosphere; the transition metal-containing polymer nanosphere comprises a polymer nanosphere matrix and a transition metal coating layer;

[0008] S2, depositing silicon on the porous carbon sphere by first chemical vapor deposition to obtain a silicon-carbon material precursor;

[0009] S3, depositing carbon on the silicon-carbon material precursor by second chemical vapor deposition; removing the transition metal to obtain a composite silicon-carbon material.

[0010] In some embodiments, in step S1, the carbon source is preferably a phenolic resin. The phenolic resin can be a thermosetting phenolic resin or a thermoplastic phenolic resin. Among them, the thermoplastic phenolic resin is preferably a linear phenolic resin, which needs to be used with a curing agent.

[0011] Preferably, the softening point of the phenolic resin is 95-105°C.

[0012] In some preferred embodiments, the carbon source is a phenolic resin, and the preparation method of the carbon sphere precursor includes the following steps:

[0013] S0, adding the carbon sphere precursor mixture to an aqueous dispersant solution to obtain a carbon sphere precursor through a curing reaction; wherein the carbon sphere precursor mixture includes a phenolic resin, a curing agent, a solvent, and a transition metal-containing polymer nanosphere; the surface of the polymer nanosphere is provided with a transition metal coating layer.

[0014] Among them, the curing agent can be a curing agent commonly used in the art, for example, one or more of hexamethylenetetramine, polyformaldehyde, an A-stage thermosetting phenolic resin, and aniline.

[0015] Among them, the mass ratio of the phenolic resin to the curing agent is preferably (15-20):1, for example, 16.7:1.

[0016] Among them, the mass ratio of the phenolic resin to the transition metal-containing polymer nanosphere is preferably (20-40):1.

[0017] Among them, the temperature of the curing reaction is preferably 95-130°C, for example, 115°C; preferably, the time of the curing reaction is 1-2h.

[0018] Among them, the curing reaction preferably further includes filtering and drying after the curing reaction.

[0019] Among them, the adding is preferably adding while stirring; the stirring speed is preferably 300-500 r / min, for example, 400 r / min.

[0020] Among them, the dispersant in the aqueous dispersant solution can be a dispersant commonly used in the art, which is preferably one or more of polyvinyl alcohol, polyvinylpyrrolidone (PVP), polyethylene glycol, and sodium dodecyl sulfate, for example, polyvinyl alcohol.

[0021] The mass fraction of the dispersant aqueous solution is preferably 0.8%-2%, for example, 1.4%, and the percentage is the mass of the dispersant in the dispersant aqueous solution accounting for the mass percentage of the dispersant aqueous solution.

[0022] The preparation method of the carbon sphere precursor mixture preferably comprises the following steps:

[0023] The phenolic resin, the curing agent and the solvent are mixed to obtain a mixed solution, and the polymer nanospheres are added to the mixed solution to obtain a carbon sphere precursor mixture.

[0024] The solvent can be a solvent commonly used in the art, for example, ethanol and / or methanol. The mass ratio of the phenolic resin to the solvent is preferably (0.4-1):1, for example, 0.67:1.

[0025] In step S1, the polymer nanosphere substrate is preferably polyethylene nanospheres and / or polystyrene (PS) nanospheres.

[0026] In step S1, the transition metal in the transition metal coating layer preferably comprises one or more of nickel, copper, tin, palladium and iron, and more preferably comprises one or more of nickel, tin and palladium.

[0027] In step S1, the preparation method of the transition metal-containing polymer nanospheres is preferably a chemical plating method, and the chemical plating method preferably comprises the following steps: mixing the polymer nanosphere substrate and a transition metal plating solution, and then centrifuging, washing and drying to obtain the transition metal-containing polymer nanospheres.

[0028] The pH value of the transition metal plating solution is preferably 6-10, for example, 8 or 9.

[0029] The particle size of the polymer nanosphere substrate is preferably 20-200 nm, for example, 200 nm.

[0030] The mixing is preferably performed by ultrasonic method. Preferably, the ultrasonic time is 0.5-1.5 h, for example, 1 h.

[0031] The drying temperature is preferably 40-60°C, for example, 50°C.

[0032] In some embodiments, the transition metal plating solution preferably comprises the following components: transition metal salt 20-60 g / L, for example, 40 g / L; NaH2PO2 20-80 g / L, for example, 60 g / L; Na3C6H5O7·2H2O 10-100 g / L, for example, 60 g / L; NH4Cl 10-50 g / L, for example, 30 g / L; and a strong alkali compound, for example, NaOH.

[0033] In some embodiments, the content of the strong base compound in the transition metal plating solution is 10-15%, the percentage being the mass percentage of the total mass of the electroless plating solution.

[0034] In some embodiments, the transition metal salt in the electroless plating solution is preferably one or more of nickel sulfate, nickel chloride, copper sulfate, stannous chloride, palladium chloride and ferric chloride.

[0035] In some embodiments, before mixing the polymer nanosphere matrix and the transition metal plating solution, the polymer nanosphere matrix is further subjected to pretreatment. The pretreatment preferably includes roughening treatment and sensitization activation treatment.

[0036] The roughening treatment preferably includes the following steps:

[0037] Concentrated sulfuric acid is slowly added to water to form an aqueous sulfuric acid solution, and then potassium dichromate is added and mixed, and then the nanosphere matrix is added and subjected to ultrasonic treatment.

[0038] In some embodiments, the temperature of the ultrasonic treatment is preferably 40-60°C, for example 50°C.

[0039] In some embodiments, the time of the ultrasonic treatment is preferably 30-90 min, for example 60 min.

[0040] In some embodiments, the concentration of sulfuric acid in the aqueous sulfuric acid solution is preferably 10-30%, the percentage being the mass percentage of the aqueous sulfuric acid solution.

[0041] In some embodiments, the molar ratio of sulfuric acid to potassium dichromate is preferably (1-10):1.

[0042] The sensitization activation treatment preferably includes the following steps:

[0043] The roughened polymer nanosphere matrix is dispersed in water to obtain a polymer nanosphere matrix mixture, and stannous chloride and palladium chloride are added to the polymer nanosphere matrix mixture, respectively, and subjected to ultrasonic treatment.

[0044] In some embodiments, the temperature of the ultrasonic treatment is preferably 40-60°C, for example 45°C.

[0045] In some embodiments, the time of the ultrasonic treatment is preferably 0.5-1.5h, for example 1h.

[0046] In some embodiments, the concentration of the polymer nanosphere matrix in the polymer nanosphere matrix mixture is 10-30%, the percentage being the mass percentage of the resin microsphere mixture.

[0047] In some embodiments, the mass ratio of the polymeric nanosphere matrix, stannous chloride and palladium chloride is 100: (2~5): (0.05~0.1).

[0048] In step S1, the temperature of the heat treatment is preferably 200-400°C, further preferably 250-350°C, more preferably 280-320°C, for example 300°C.

[0049] In step S1, the time of the heat treatment is preferably 1-3 h, for example 2 h.

[0050] In step S1, the heating rate for heating to the temperature of the heat treatment is preferably 1-5°C / min, for example 5°C / min.

[0051] In step S1, the temperature of the carbonization treatment is preferably 700-900°C, further preferably 750-850°C, for example 800°C.

[0052] In step S1, the time of the carbonization treatment is preferably 2-4 h, for example 2 h.

[0053] In step S1, the heating rate for heating to the temperature of the carbonization treatment is preferably 1-5°C / min, for example 2°C / min.

[0054] In step S1, the atmosphere of the carbonization treatment is preferably an inert atmosphere, which can be nitrogen or an inert gas (for example argon). The inert atmosphere in the present application refers to a gaseous environment that does not chemically react with raw materials or other substances, and is not equivalent to an inert gas, for example nitrogen.

[0055] In step S1, the activation treatment is preferably alkali activation or gas activation; wherein the gas activation is preferably carbon dioxide activation or water vapor activation.

[0056] In some preferred embodiments, in step S1, the activation treatment is carbon dioxide activation.

[0057] The temperature of the carbon dioxide activation is preferably 850-1000°C, more preferably 900-1000°C, further more preferably 900-950°C; and the heating rate for heating to the temperature of the carbon dioxide activation is preferably 1-5°C / min, for example 1°C / min.

[0058] The time of the carbon dioxide activation is preferably 2-6 h, for example 3 h.

[0059] In step S1, the specific surface area of the porous carbon sphere is preferably 1500-2500 m 2 / g, for example 1523 m2 / g, 1532 m 2 / g, 1583 m 2 / g, 1624 m 2 / g, 1625 m 2 / g, 1642 m 2 / g, 1682 m 2 / g, 1683 m 2 / g or 1823 m 2 / g.

[0060] In step S1, the Dv50 particle size of the porous carbon spheres is preferably 9-12 μm, for example 9.8 μm, 10.3 μm, 10.4 μm, 10.5 μm, 10.7 μm, 10.8 μm or 11.1 μm.

[0061] In step S1, the pore volume of the porous carbon spheres is preferably 0.6-1.0 cm 3 / g, more preferably 0.7-0.95 cm 3 / g, for example 0.74 cm 3 / g, 0.79 cm 3 / g, 0.81 cm 3 / g, 0.83 cm 3 / g, 0.84 cm 3 / g, 0.85 cm 3 / g or 0.86 cm 3 / g.

[0062] In step S1, the proportion of micropores in the porous carbon spheres is preferably 58%-98%, more preferably 58%-74%, for example 64%, 66%, 67%, 68% or 70%, the percentage being the proportion of the volume of the micropores to the total pore volume of the porous carbon spheres. The micropores refer to pores with a pore size of less than 2 nm.

[0063] In step S1, the proportion of mesopores in the porous carbon spheres is preferably 10%-32%, more preferably 20%-30%, for example 24%, 25%, 26%, 27% or 29%, the percentage being the proportion of the volume of the mesopores to the total pore volume of the porous carbon spheres. The mesopores refer to pores with a pore size of 2-50 nm.

[0064] In step S1, the proportion of macropores in the porous carbon spheres is preferably 1%-15%, for example 6%, 7%, 8%, 9% or 10%, the percentage being the proportion of the volume of the macropores to the total pore volume of the porous carbon spheres. The macropores refer to pores with a pore size of greater than 50 nm.

[0065] In step S1, the content of carbon element in the porous carbon sphere is preferably 85%-94%, more preferably 88%-92%, for example 88.6%, 90.3%, 90.8%, 91.6%, 92.4%, 92.9%, 93.3% or 93.6%, the percentage being the mass percentage in the total mass of the porous carbon sphere.

[0066] In step S1, the content of oxygen element in the porous carbon sphere is preferably 1%-8%, more preferably 3%-6%, for example 1.2%, 1.8%, 2.8%, 4.1%, 4.2%, 4.3%, 4.7%, 4.8% or 7.7%, the percentage being the mass percentage in the total mass of the porous carbon sphere.

[0067] In step S1, the content of transition metal element in the porous carbon sphere is preferably 1%-6%, the percentage being the mass percentage in the total mass of the porous carbon sphere. When the transition metal element in the porous carbon sphere includes nickel, the content of nickel is preferably 1.5%-5.5%, for example 2.8%, 3.5%, 4.2%, 4.3%, 4.8%, 5.2%, 5.3% or 5.4%, the percentage being the mass percentage in the total mass of the porous carbon sphere.

[0068] In step S2, the silicon source of the first chemical vapor deposition is preferably an organic silane, more preferably one or more of methylsilane, disilane and chlorosilane, for example methylsilane.

[0069] The flow rate of the silicon source is preferably 200-300 cc / min, for example 250 cc / min.

[0070] In step S2, the temperature of the first chemical vapor deposition is preferably 500-700℃, for example 600℃.

[0071] In step S2, the time of the first chemical vapor deposition is preferably 2-6 h, for example 3 h.

[0072] In step S2, the heating rate for heating to the temperature of the first chemical vapor deposition is preferably 1-5℃ / min, for example 3℃ / min.

[0073] In step S2, the atmosphere of the first chemical vapor deposition is preferably an inert atmosphere. The inert atmosphere can be nitrogen or an inert gas (for example argon). The inert atmosphere in the present application refers to a gaseous environment that does not chemically react with raw materials or other substances, and is not equivalent to an inert gas, for example nitrogen.

[0074] The flow rate of the atmosphere is preferably 450-550 cc / min, for example 500 cc / min.

[0075] In steps S2 and S3, the first and second chemical vapor depositions are preferably performed in a fluidized bed reactor.

[0076] In step S3, the carbon source of the second chemical vapor deposition is preferably an organic carbon source.

[0077] The organic carbon source is preferably one or more of acetylene, methane and propylene, for example acetylene.

[0078] The flow rate of the organic carbon source is preferably 80-150 cc / min, for example 100 cc / min.

[0079] In step S3, the temperature of the second chemical vapor deposition is preferably 500-700°C, for example 600°C.

[0080] In step S3, the time of the second chemical vapor deposition is preferably 2-4 h, for example 2 h.

[0081] In step S3, the atmosphere of the second chemical vapor deposition is preferably an inert atmosphere. The inert atmosphere can be nitrogen or an inert gas (for example argon). The inert atmosphere in the present application refers to a gaseous environment that does not chemically react with raw materials or other substances, and is not equivalent to an inert gas, for example nitrogen.

[0082] The flow rate of the atmosphere is preferably 350-450 cc / min, for example 400 cc / min.

[0083] In step S3, the transition metal removal method is preferably an acid pickling treatment.

[0084] The acid in the acid pickling agent of the acid pickling treatment preferably includes one or more of nitric acid, sulfuric acid and hydrochloric acid, for example nitric acid.

[0085] The concentration of the acid in the acid pickling agent of the acid pickling treatment is preferably 8%-15%, for example 10%, the percentage being the mass of the acid as a percentage of the total mass of the acid pickling agent.

[0086] The temperature of the acid pickling treatment is preferably 55-65°C, for example 60°C.

[0087] The time of the acid pickling treatment is preferably 2-5 h, for example 3 h.

[0088] In step S3, the transition metal removal preferably includes filtration, washing and drying. The washing agent of the washing is preferably water.

[0089] The composite silicon-carbon material is prepared by the preparation method of the composite silicon-carbon material.

[0090] In the present application, the composite silicon-carbon material can be a core-shell structure; the core of the core-shell structure comprises a porous carbon sphere and a silicon nanoparticle, and the silicon nanoparticle is distributed on the surface and in the pores of the porous carbon sphere; the shell of the core-shell structure is a carbon layer, and the composite silicon-carbon material is distributed with carbon nanotubes, and the carbon nanotubes are distributed in one or more of the carbon layer, the surface and the pores of the porous carbon sphere.

[0091] In the present application, the composite silicon-carbon material is preferably a mesoporous material.

[0092] In the present application, the specific surface area of the composite silicon-carbon material is preferably 2.7-3 m 2 / g, for example 2.9 m 2 / g or 3 m 2 / g.

[0093] In the present application, the powder resistivity of the composite silicon-carbon material is preferably 0.4-0.7 Ω·m, for example 0.47 Ω·m or 0.62 Ω·m.

[0094] In the present application, the silicon loading of the composite silicon-carbon material is preferably 45%-55%, for example 53% or 49%, and the percentage is the percentage of the mass of the silicon nanoparticle to the total mass of the composite silicon-carbon material.

[0095] In the present application, the content of carbon in the composite silicon-carbon material is preferably 45%-55%, for example 47% or 51%, and the percentage is the percentage of the mass of carbon in the composite silicon-carbon material to the total mass of the composite silicon-carbon material.

[0096] In the present application, the tap density of the composite silicon-carbon material is preferably 0.90-1.5 g / cm 3 , for example 0.93 g / cm 3 .

[0097] The present application provides an application of the composite silicon-carbon material as described above as a negative electrode material in a lithium ion battery.

[0098] The present application also provides a lithium ion battery comprising the composite silicon-carbon material as described above.

[0099] On the basis of common sense in the art, the above-mentioned preferred conditions can be combined arbitrarily, i.e. to obtain each preferred example of the present application.

[0100] The reagents and raw materials used in the present application are commercially available.

[0101] The positive progress effect of the present application is that:

[0102] In the preparation method of the composite silicon-carbon material of the present application, porous carbon spheres are obtained by using a carbon sphere precursor comprising polymer nanospheres containing transition metals and a carbon source, the obtained composite silicon-carbon material has a high silicon loading amount and excellent stability and conductivity, the lithium ion battery using the composite silicon-carbon material as a negative electrode material has excellent capacity performance, and can have excellent cycle performance and first efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0103] Figure 1 Structure schematic diagram of the porous carbon spheres obtained in step S1 in Examples 1-9.

[0104] Reference signs:

[0105] Nickel coating layer 1

[0106] Pore 2

[0107] Porous carbon sphere matrix 3 DETAILED DESCRIPTION

[0108] The present application will be further described by way of examples, but the present application is not limited to the scope of the examples. In the following examples, the experimental methods not specified in the specific conditions are selected according to the conventional methods and conditions, or according to the product instructions.

[0109] Example 1

[0110] (1) Preparation of the composite silicon-carbon material:

[0111] S0, Preparation of the carbon sphere precursor:

[0112] S0-1, Roughening treatment: 50 mL of concentrated sulfuric acid was slowly added to 10 mL of deionized water, then 1 g of potassium dichromate was added and stirred uniformly, 3 g of PS nanospheres (particle size 200 nm) were added, and ultrasonic treatment was performed at 50 ℃ for 1 h. After centrifugation, the PS nanospheres were washed with deionized water.

[0113] S0-2, Sensitization treatment: the PS nanospheres obtained by the roughening treatment were dispersed with 10 mL of water, 10 mL of PdCl2 with a concentration of 3 g / L and 20 mL / L of SnCl2 were added respectively, and after mixing uniformly, ultrasonic treatment was performed at 50 ℃ for 1 h. After completion, deionized water was used for washing, and a polymer nanosphere matrix was obtained.

[0114] S0-3, preparation of polymer nanospheres containing transition metal by electroless plating: 3 g of the polymer nanospheres substrate prepared in the above step S0-2 was poured into 100 mL of electroless plating solution and ultrasonically treated at 40 °C for 1 h. After the treatment, the polymer nanospheres were separated by centrifugation, washed repeatedly with deionized water, and dried at 50 °C to obtain polymer nanospheres containing transition metal (including the polymer nanospheres substrate and the nickel coating layer, with a particle size of 200 nm). The electroless plating solution was prepared by the following steps: first, 4 g of NiSO4·6H2O was added to deionized water; then, 6 g of NaH2PO2 was added; next, 6 g of Na3C6H5O7·2H2O was added; finally, 3 g of NH4Cl was added, and the solution was completely dissolved. Sodium hydroxide (10% by mass) was added to adjust the pH to 8.

[0115] S0-4, preparation of carbon sphere precursor: 60 g of phenol-formaldehyde resin with a softening point of 95-105 °C was dissolved in 90 g of ethanol, and 3.6 g of hexamethylenetetramine curing agent was added. Then, 3 g of polymer nanospheres containing transition metal was added, and the mixture was mixed uniformly to obtain a carbon sphere precursor mixture. A PVA aqueous solution with a mass fraction of 1.4% was prepared by dissolving 600 g of PVA in deionized water. The carbon sphere precursor mixture was poured into the PVA aqueous solution while stirring at a rotation speed of 400 r / min. The mixture was reacted at 115 °C for 1 h, and then filtered and dried to obtain the carbon sphere precursor.

[0116] S1, preparation of porous carbon spheres:

[0117] S1-1, heat treatment of the carbon sphere precursor in a nitrogen atmosphere: the temperature was raised to 300 °C at a rate of 5 °C / min and held for 2 h;

[0118] S1-2, carbonization treatment: the temperature was raised to 800 °C at a rate of 2 °C / min in a nitrogen atmosphere and held for 2 h;

[0119] S1-3, activation treatment: the temperature was raised to 950 °C at a rate of 1 °C / min, and the nitrogen gas was replaced with carbon dioxide. The porous carbon spheres were obtained by activating with carbon dioxide for 3 h.

[0120] The structure of the porous carbon spheres is shown in Figure 1 The porous carbon spheres include a porous carbon sphere substrate 3, a nickel coating layer 1, and pores 2.

[0121] S2, preparation of silicon-carbon material precursor:

[0122] The prepared porous carbon spheres were added into a fluidized bed reactor, nitrogen was first introduced to replace the air in the reactor, and the fluidized bed was heated to 600°C at a heating rate of 3°C / min, and a mixture of nitrogen (flow rate of 500 cc / min) and silane (SiH4, flow rate of 250 cc / min) was introduced, and the deposition time was 3 h, to obtain a silicon-carbon material precursor;

[0123] S3, preparation of a composite silicon-carbon material:

[0124] S3-1, then the obtained silicon-carbon material precursor was subjected to a second chemical vapor deposition: the silane gas was replaced by acetylene gas, and the flow rate of nitrogen was 400 cc / min, the flow rate of acetylene gas was 100 cc / min, and the gas was introduced at 600°C for 2 h.

[0125] S3-2, removal of transition metal: after the material was cooled, it was taken out, soaked in 10% nitric acid at 60°C for 3 h, and then washed to remove the nickel metal, and then the material was filtered and washed with deionized water to obtain the final composite silicon-carbon material.

[0126] (2) Preparation of a button lithium ion battery

[0127] According to the mass ratio of the composite silicon-carbon material, conductive agent Super P (SP), carboxymethyl cellulose (CMC), and butadiene rubber (SBR) being 90:4:2:4 (total 100 parts by mass), the composite silicon-carbon material was added with the binder CMC, SBR, conductive agent SP, and solvent ethanol (220 mL), and mixed uniformly to prepare a negative electrode slurry, the negative electrode slurry was coated on a copper foil, and vacuum dried for 12 h to prepare a negative electrode sheet, the electrolyte was LiPF6 / EC+DEC, the volume ratio of EC and DEC was 1:1, a metal lithium sheet was used as a counter electrode, a polyethylene (PE) separator was used, and the negative electrode sheet, the separator, the metal lithium sheet, and the electrolyte were assembled in a glove box filled with hydrogen to obtain a button lithium ion battery.

[0128] Example 2

[0129] The difference between this example and Example 1 is that in step S0-3, the pH of the electroless plating solution is 9, and the other conditions remain the same as in Example 1.

[0130] Example 3

[0131] The difference between this example and Example 1 is that in step S0-3, the pH of the electroless plating solution is 10, and the other conditions remain the same as in Example 1.

[0132] Example 4

[0133] The difference between this embodiment and embodiment 1 is that polyethylene nanospheres are used to replace PS nanospheres in step S0-1, and the rest of the conditions are the same as embodiment 1.

[0134] Embodiment 5

[0135] The difference between this embodiment and embodiment 1 is that the temperature of the heat treatment in step S1-1 is 250°C, and the rest of the conditions are the same as embodiment 1.

[0136] Embodiment 6

[0137] The difference between this embodiment and embodiment 1 is that the temperature of the carbonization treatment in step S1-2 is 750°C, and the rest of the conditions are the same as embodiment 1.

[0138] Embodiment 7

[0139] The difference between this embodiment and embodiment 1 is that the temperature of the carbonization treatment in step S1-2 is 850°C, and the rest of the conditions are the same as embodiment 1.

[0140] Embodiment 8

[0141] The difference between this embodiment and embodiment 1 is that the temperature of the carbonization treatment in step S1-2 is 900°C, and the rest of the conditions are the same as embodiment 1.

[0142] Embodiment 9

[0143] The difference between this embodiment and embodiment 1 is that the temperature of the activation treatment in step S1-3 is 1000°C, and the rest of the conditions are the same as embodiment 1.

[0144] Comparative Example 1

[0145] The difference between this comparative example and embodiment 1 is that there is no step S0-3, and the polymer nanosphere matrix is used to replace the transition metal-containing polymer nanospheres in step S0-4; that is, in step S1, the obtained carbon sphere precursor only includes the polymer nanosphere matrix, and does not include a nickel coating layer, and the rest of the conditions are the same as embodiment 1.

[0146] Comparative Example 2

[0147] The difference between this comparative example and embodiment 1 is that there is no step S0-1, S0-2, and S0-3, and no transition metal-containing polymer nanospheres are added in step S0-4; that is, in step S1, the obtained carbon sphere precursor does not include transition metal-containing polymer nanospheres, and the rest of the conditions are the same as embodiment 1.

[0148] Comparative Example 3

[0149] The difference between this comparative example and embodiment 1 is that there is no step S1-1, that is, no heat treatment is performed, and the rest of the conditions are the same as embodiment 1.

[0150] Effect Example 1

[0151] The porous carbon spheres obtained in Examples 1-9 and Comparative Examples 1-3 were respectively tested for Dv50 particle size, pore volume, specific surface area and element content, and the test results are shown in Table 1. Among them, the particle size was tested by a laser particle size instrument, the pore volume and specific surface area were tested by a gas adsorption BET method, and the element content was tested by EDS.

[0152] Effect Example 2

[0153] The composite silicon-carbon materials obtained in Examples 1-9 and Comparative Examples 1-3 were respectively tested for silicon loading, powder resistivity, specific surface area and tap density. Among them, the silicon loading was tested by a TGA thermal gravimetric analyzer, the powder resistivity was tested by an RTS-4 type four-probe tester, the specific surface area was tested by a gas adsorption BET method, and the tap density was tested by a tap density analyzer (Dandong Bitai BT-311). The above test results are shown in Table 2.

[0154] Effect Example 3

[0155] The button-type lithium ion batteries prepared in Examples 1-9 and Comparative Examples 1-3 were respectively tested for first discharge capacity, first efficiency and cycle performance. The test was performed in a Wuhan Lan Dian Xinwei 5v / 10mA type battery tester, the charge-discharge voltage range was controlled at 0.005-2.0V, the charge-discharge rate was 0.5C, the charge-discharge cycle was performed, and the capacity retention rate was tested at 150 cycles, 300 cycles and 400 cycles, respectively. The specific test data are shown in Tables 3 and 4.

[0156]

[0157]

[0158]

[0159]

[0160] According to Tables 1, 2, 3 and 4, the specific surface area of the porous carbon spheres obtained in Examples 1-9 can reach 1523-1823 m 2 / g, the Dv50 particle size can reach 9.8-11.1 μm, and the pore volume can reach 0.74-0.95 cm 3 / g, the micropore ratio can reach 58%-74%, the mesopore ratio can reach 20%-32%, the macropore ratio can reach 6%-10%, the content of carbon element can reach 88.6%-94%, the content of oxygen element can reach 1.2%-7.7%, and the content of nickel element can reach 1.5%-5.4%; the specific surface area of the obtained composite silicon-carbon material can reach 2.6-4 m 2 / g, the powder resistivity can reach 0.41-0.87 Ω·m, the silicon loading can reach 43%-54%, and the tap density can reach 0.92-0.98 g / cm 3 The lithium ion battery containing the composite silicon-carbon material has excellent capacity performance and can balance excellent initial efficiency and cycle performance. Specifically, the initial discharge capacity of the lithium ion battery can reach 1810 mAh / g, and even can reach 1900 mAh / g or more; the initial efficiency can reach 89% or more, and even can reach 93% or more; and the cycle capacity retention rate after 400 cycles can reach 85% or more.

[0161] The inventors have found that the composite silicon-carbon material in the application has a high silicon loading and a low powder resistivity, and the lithium ion battery containing the same has excellent capacity performance and can balance excellent initial efficiency and cycle performance. However, the lithium ion battery obtained by using a polymer nanosphere matrix, not using a polymer nanosphere containing a transition metal, or not performing heat treatment, cannot achieve the above-mentioned excellent electrochemical performance. This may be because the pore structure brought by using PS as a template, the obtained composite silicon-carbon material has a larger pore volume, thereby being able to load more silicon and having more space to buffer the expansion of silicon. In the deposition process, compared with no nickel doping, the addition of nickel metal can promote the deposition of silane and the growth of carbon nanotubes.

[0162] Compared with Example 1, in Comparative Example 1, a polymer nanosphere matrix is used, that is, in step S1, the obtained carbon sphere precursor only includes a polymer nanosphere matrix, and does not include a nickel coating layer. When the obtained composite silicon-carbon material is applied to a lithium ion battery, the initial discharge capacity of the obtained lithium ion battery is significantly reduced, and the initial efficiency and the cycle capacity retention rate after 400 cycles are also poor.

[0163] Compared with Example 1, in Comparative Example 2, no polymer nanosphere containing a transition metal is used, that is, in step S1, the obtained carbon sphere precursor does not include a polymer nanosphere containing a transition metal. When the obtained composite silicon-carbon material is applied to a lithium ion battery, the initial discharge capacity, the initial efficiency, and the cycle capacity retention rate after 400 cycles of the obtained lithium ion battery are all significantly deteriorated.

[0164] Compared with Example 1, in Comparative Example 3, step S1-1, i.e. the heat treatment, was not performed, but step S1-2, i.e. the carbonization treatment, was directly performed, and the initial discharge capacity, the initial efficiency and the cycle capacity retention rate after 400 cycles of the obtained lithium ion battery were all significantly deteriorated.

[0165] As can be seen from Comparative Examples 1, 2 and 3, as the pH value of the electroless plating solution increases in turn, the silicon loading of the obtained composite silicon-carbon material decreases in turn, the powder resistivity increases in turn, and the initial discharge capacity and the initial efficiency of the obtained lithium ion battery are all reduced in turn. This may be because controlling the pH value can control the doping amount of nickel metal, and the presence of nickel metal can catalyze the deposition of silane, thereby affecting the conversion rate of silane and the loading of silicon.

[0166] Although the specific embodiments of the present application are described above, those skilled in the art should understand that this is only an illustration, and the protection scope of the present application is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present application, and such changes and modifications all fall within the protection scope of the present application.

Claims

1. A method for preparing a composite silicon-carbon material, characterized by, It comprises the following steps: S1, heat treatment, carbonization treatment and activation treatment are carried out on the carbon sphere precursor to obtain a porous carbon sphere; the preparation method of the carbon sphere precursor comprises the following steps: S0, the carbon sphere precursor mixture is added into a dispersant aqueous solution, and a solidification reaction is carried out to obtain a carbon sphere precursor; wherein the carbon sphere precursor mixture comprises phenolic resin, a curing agent, a solvent and transition metal-containing polymer nanospheres; the transition metal-containing polymer nanospheres comprise a polymer nanosphere matrix and a transition metal coating layer; S2, silicon is deposited on the porous carbon sphere by using first chemical vapor deposition to obtain a silicon-carbon material precursor; S3, carbon is deposited on the silicon-carbon material precursor by using second chemical vapor deposition; the transition metal is removed to obtain a composite silicon-carbon material.

2. The method of making a composite silicon-carbon material of claim 1, wherein, In step S1, the carbon sphere precursor meets one or more of the following conditions a-c: a. In step S1, the polymer nanosphere matrix is polyethylene nanosphere and / or polystyrene nanosphere; b. In step S1, the transition metal in the transition metal coating layer comprises one or more of nickel, copper, tin, palladium and iron; c. In step S1, the preparation method of the transition metal-containing polymer nanosphere is chemical plating.

3. The method of making a composite silicon-carbon material of claim 2, wherein, In step S1, the transition metal in the transition metal coating layer comprises one or more of nickel, tin and palladium.

4. The method of making a composite silicon-carbon material of claim 2, wherein, In step S1, the chemical plating method comprises the following steps: mixing the polymer nanosphere matrix and a transition metal plating solution, and then carrying out centrifugation, cleaning and drying.

5. The method of claim 4, wherein the silicon-carbon composite material is prepared by the steps of: mixing a silicon source and a carbon source to form a mixture; and heating the mixture to form the silicon-carbon composite material. The pH value of the transition metal plating solution is 6-10; And / or, the particle size of the polymer nanosphere matrix is 20-200 nm.

6. The method of making a composite silicon-carbon material of claim 5, wherein, The pH value of the transition metal plating solution is 8 or 9.

7. The method of making a composite silicon-carbon material of claim 5, wherein, The particle size of the polymer nanosphere matrix is 200 nm.

8. The method of making a composite silicon-carbon material of claim 1, wherein, In step S1, the softening point of the phenolic resin is 95-105℃.

9. The method of making a composite silicon-carbon material of claim 1, wherein, The preparation method of the carbon sphere precursor meets one or more of the following conditions a-h: a. The curing agent is one or more of hexamethylenetetramine, polyformaldehyde, A-stage thermosetting phenolic resin and aniline; b. The mass ratio of the phenolic resin to the curing agent is (15-20):1; c. The mass ratio of the phenolic resin to the transition metal-containing polymer nanosphere is (20-40):1; d. The temperature of the solidification reaction is 95-130℃; e. The time of the solidification reaction is 1-2h; f. The adding is carried out while stirring; g. The dispersant in the dispersant aqueous solution is one or more of polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol and sodium dodecyl sulfonate; h. The mass fraction of the dispersant aqueous solution is 0.8%-2%, and the percentage is the mass of the dispersant in the dispersant aqueous solution accounting for the mass percentage of the dispersant aqueous solution.

10. The method of claim 9, wherein the composite silicon-carbon material is prepared by the steps of: The mass ratio of the phenolic resin to the curing agent is 16.7:

1.

11. The method of making a composite silicon-carbon material of claim 9, wherein, The temperature of the solidification reaction is 115℃.

12. The method of making a composite silicon-carbon material of claim 9, wherein, The stirring speed is 300-500 r / min.

13. The method of making a composite silicon-carbon material of claim 12, wherein, The stirring speed is 400 r / min.

14. The method of making a composite silicon-carbon material of claim 9, wherein, The dispersant in the dispersant aqueous solution is polyvinyl alcohol.

15. The method of making a composite silicon-carbon material of claim 9, wherein, The mass fraction of the dispersant aqueous solution is 1.4%.

16. The method of making a composite silicon-carbon material of claim 1, wherein, Step S1 meets one or more of the following conditions a-h: a. In step S1, the temperature of the heat treatment is 200-400℃; b. In step S1, the time of the heat treatment is 1-3 h; c. In step S1, the heating rate to the temperature of the heat treatment is 1-5℃ / min; d. In step S1, the temperature of the carbonization treatment is 700-900℃; e. In step S1, the time of the carbonization treatment is 2-4 h; f. In step S1, the heating rate to the temperature of the carbonization treatment is 1-5℃ / min; g. In step S1, the atmosphere of the carbonization treatment is inert atmosphere; h. In step S1, the activation treatment is alkali activation or gas activation.

17. The method of making a composite silicon-carbon material of claim 16, wherein, Step S1 meets one or more of the following conditions a-e: a. In step S1, the temperature of the heat treatment is 250-350℃; b. In step S1, the time of the heat treatment is 2 h; c. In step S1, the temperature of the carbonization treatment is 750-850℃; d. In step S1, the heating rate to the temperature of the carbonization treatment is 2℃ / min; e. In step S1, the gas activation is carbon dioxide activation or water vapor activation.

18. The method of making a composite silicon-carbon material of claim 17, wherein, In step S1, the temperature of the heat treatment is 280-320℃.

19. The method of making a composite silicon-carbon material of claim 18, wherein, In step S1, the temperature of the heat treatment is 300℃.

20. The method of making a composite silicon-carbon material of claim 17, wherein, In step S1, the temperature of the carbonization treatment is 800℃.

21. The method of making a composite silicon-carbon material of claim 17, wherein, The carbon dioxide activation meets one or more of the following conditions a-c: a. The temperature of the carbon dioxide activation is 850-1000℃; b. The heating rate to the temperature of the carbon dioxide activation is 1-5℃ / min; c. The time of the carbon dioxide activation is 2-6 h.

22. The method of making a composite silicon-carbon material of claim 21, wherein, The temperature of the carbon dioxide activation is 900-1000℃.

23. The method of making a composite silicon-carbon material of claim 22, wherein, The temperature of the carbon dioxide activation is 900-950℃.

24. The method of making a composite silicon-carbon material of claim 21, wherein, The time of the carbon dioxide activation is 3 h.

25. The method of making a composite silicon-carbon material of claim 1, wherein, In step S1, the porous carbon spheres meet one or more of the following conditions a-i: a、In step S1, the specific surface area of the porous carbon sphere is 1500-2500 m 2 / g; b. In step S1, the Dv50 particle size of the porous carbon spheres is 9-12 μm; c. In step S1, the porous carbon sphere has a pore volume of 0.6-1.0 cm 3 / g; d. In step S1, the proportion of micropores in the porous carbon spheres is 58%-98%, the percentage being the proportion of the volume of the micropores to the total pore volume of the porous carbon spheres; e. In step S1, the proportion of mesopores in the porous carbon spheres is 10%-32%, the percentage being the proportion of the volume of the mesopores to the total pore volume of the porous carbon spheres; f. In step S1, the proportion of macropores in the porous carbon spheres is 1%-15%, the percentage being the proportion of the volume of the macropores to the total pore volume of the porous carbon spheres; g. In step S1, the content of carbon element in the porous carbon spheres is 85%-94%, the percentage being the mass percentage in the total mass of the porous carbon spheres; h. In step S1, the content of oxygen element in the porous carbon spheres is 1%-8%, the percentage being the mass percentage in the total mass of the porous carbon spheres; i. In step S1, the content of transition metal element in the porous carbon spheres is 1%-6%, the percentage being the mass percentage in the total mass of the porous carbon spheres.

26. The method of making a composite silicon-carbon material of claim 25, wherein, In step S1, the porous carbon spheres satisfy one or more of the following conditions a-i: a. In step S1, the specific surface area of the porous carbon spheres is 1523 m 2 / g, 1532 m 2 / g, 1583 m 2 / g, 1624 m 2 / g, 1625 m 2 / g, 1642 m 2 / g, 1682 m 2 / g, 1683 m 2 / g or 1823 m 2 / g; b. In step S1, the Dv50 particle size of the porous carbon spheres is 9.8 μm, 10.3 μm, 10.4 μm, 10.5 μm, 10.7 μm, 10.8 μm or 11.1 μm; c. in step S1, the porous carbon sphere has a pore volume of 0.7-0.95 cm 3 / g; d. In step S1, the proportion of micropores in the porous carbon spheres is 58%-74%; e. In step S1, the proportion of mesopores in the porous carbon spheres is 20%-30%; f. In step S1, the proportion of macropores in the porous carbon spheres is 6%, 7%, 8%, 9% or 10%; g. In step S1, the content of carbon element in the porous carbon spheres is 88%-92%; h. In step S1, the content of oxygen element in the porous carbon spheres is 3%-6%; i. In step S1, when the transition metal element in the porous carbon spheres includes nickel, the content of nickel is 1.5%-5.5%, the percentage being a mass percentage of the total mass of the porous carbon spheres.

27. The method of making a composite silicon-carbon material of claim 25, wherein, The pore volume of the porous carbon spheres in step S1 is 0.74 cm 3 / g, 0.79 cm 3 / g, 0.81 cm 3 / g, 0.83 cm 3 / g, 0.84 cm 3 / g, 0.85 cm 3 / g, or 0.86 cm 3 / g.

28. The method of making a composite silicon-carbon material of claim 25, wherein, In step S1, the proportion of micropores in the porous carbon spheres is 64%, 66%, 67%, 68% or 70%.

29. The method of making a composite silicon-carbon material of claim 25, wherein, In step S1, the proportion of mesopores in the porous carbon spheres is 24%, 25%, 26%, 27% or 29%.

30. The method of making a composite silicon-carbon material of claim 25, wherein, In step S1, the content of carbon element in the porous carbon spheres is 88.6%, 90.3%, 90.8%, 91.6%, 92.4%, 92.9%, 93.3% or 93.6%.

31. The method of making a composite silicon-carbon material of claim 25, wherein, In step S1, the content of oxygen element in the porous carbon spheres is 1.2%, 1.8%, 2.8%, 4.1%, 4.2%, 4.3%, 4.7%, 4.8% or 7.7%.

32. The method of making a composite silicon-carbon material of claim 26, wherein, In step S1, the content of nickel is 2.8%, 3.5%, 4.2%, 4.3%, 4.8%, 5.2%, 5.3% or 5.4%.

33. The method of making a composite silicon-carbon material of claim 1, wherein, In step S2 and step S3, one or more of the following conditions a-k are satisfied: a. In step S2, the silicon source of the first chemical vapor deposition is an organic silane; b. In step S2, the temperature of the first chemical vapor deposition is 500-700℃; c. In step S2, the time of the first chemical vapor deposition is 2-6 h; d. In step S2, the temperature rising rate for rising to the temperature of the first chemical vapor deposition is 1-5℃ / min; e. In step S2, the atmosphere of the first chemical vapor deposition is an inert atmosphere; f. In step S2 and step S3, the first chemical vapor deposition and the second chemical vapor deposition are carried out in a fluidized bed reactor; g. In step S3, the carbon source of the second chemical vapor deposition is an organic carbon source; h. In step S3, the temperature of the second chemical vapor deposition is 500-700℃; i. In step S3, the time of the second chemical vapor deposition is 2-4 h; j. In step S3, the atmosphere of the second chemical vapor deposition is an inert atmosphere; k. In step S3, the way of removing transition metal is acid washing treatment.

34. The method of making a composite silicon-carbon material of claim 33, wherein, In step S2, the silicon source of the first chemical vapor deposition is one or more of methylsilane, disilane and chlorosilane.

35. The method of making a composite silicon-carbon material of claim 34, wherein, The first chemical vapor deposition in step S2 is performed at a temperature of 600℃.

36. The method of making a composite silicon-carbon material of claim 34, wherein, The flow rate of the silicon source in step S2 is 200-300 cc / min.

37. The method of making a composite silicon-carbon material of claim 36, wherein, The flow rate of the silicon source in step S2 is 250 cc / min.

38. The method of making a composite silicon-carbon material of claim 33, wherein, The first chemical vapor deposition in step S2 is performed at a temperature of 600℃.

39. The method of making a composite silicon-carbon material of claim 33, wherein, The first chemical vapor deposition in step S2 is performed for 3 h.

40. The method of making a composite silicon-carbon material of claim 33, wherein, The ramping rate for ramping up to the temperature of the first chemical vapor deposition in step S2 is 3℃ / min.

41. The method of making a composite silicon-carbon material of claim 33, wherein, The flow rate of the atmosphere in step S2 is 450-550 cc / min.

42. The method of making a composite silicon-carbon material of claim 41, wherein, The flow rate of the atmosphere in step S2 is 500 cc / min.

43. The method of making a composite silicon-carbon material of claim 33, wherein, The organic carbon source in step S3 is one or more of acetylene, methane and propylene.

44. The method of making a composite silicon-carbon material of claim 43, wherein, The organic carbon source in step S3 is acetylene.

45. The method of making a composite silicon-carbon material of claim 33, wherein, The flow rate of the organic carbon source in step S3 is 80-150 cc / min.

46. The method of making a composite silicon-carbon material of claim 45, wherein, The flow rate of the organic carbon source in step S3 is 100 cc / min.

47. The method of making a composite silicon-carbon material of claim 33, wherein, The second chemical vapor deposition in step S3 is performed at a temperature of 600℃.

48. The method of making a composite silicon-carbon material of claim 33, wherein, The flow rate of the atmosphere in step S3 is 350-450 cc / min.

49. The method of making a composite silicon-carbon material of claim 48, wherein, The flow rate of the atmosphere in step S3 is 400 cc / min.

50. A composite silicon-carbon material, characterized in that, It is prepared by the method for preparing a composite silicon-carbon material according to any one of claims 1-49.

51. The composite silicon-carbon material of claim 50, wherein, The composite silicon-carbon material satisfies one or more of the following conditions a-g: a. The composite silicon-carbon material is a mesoporous material; b. The composite silicon-carbon material is a core-shell structure; the core of the core-shell structure comprises porous carbon spheres and silicon nanoparticles, the silicon nanoparticles are distributed on the surface and in the pores of the porous carbon spheres; the shell of the core-shell structure is a carbon layer, the composite silicon-carbon material contains carbon nanotubes, and the carbon nanotubes are distributed in one or more of the carbon layer, the surface and the pores of the porous carbon spheres; c. the specific surface area of the composite silicon-carbon material is 2.7-3 m 2 / g; d. The powder resistivity of the composite silicon-carbon material is 0.4-0.7 Ω·m; e. The silicon loading of the composite silicon-carbon material is 45%-55%, the percentage being the percentage of the mass of the silicon nanoparticles in the total mass of the composite silicon-carbon material; f. The content of carbon in the composite silicon-carbon material is 45%-55%, the percentage being the percentage of the mass of carbon in the composite silicon-carbon material in the total mass of the composite silicon-carbon material; g. the tap density of the composite silicon-carbon material is 0.90-1.5 g / cm 3 .

52. The composite silicon-carbon material of claim 51, wherein, The composite silicon-carbon material satisfies one or more of the following conditions a-e: a. the specific surface area of the composite silicon-carbon material is 2.9 m 2 / g or 3 m 2 / g; b. The powder resistivity of the composite silicon-carbon material is 0.47 Ω·m or 0.62 Ω·m; c. The silicon loading of the composite silicon-carbon material is 53% or 49%; d. The content of carbon in the composite silicon-carbon material is 47% or 51%; e. the tap density of the composite silicon-carbon material is 0.93 g / cm 3 .

53. Use of the composite silicon-carbon material according to any one of claims 50-52 as an anode material in a lithium ion battery.

54. A lithium-ion battery, characterized in that, It comprises the composite silicon-carbon material according to any one of claims 50-52.

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