Silicon-carbon negative electrode precursor material, silicon-carbon negative electrode material and preparation method of silicon-carbon negative electrode precursor material

Abstract

The invention relates to the technical field of silicon-carbon negative electrodes, in particular to a silicon-carbon negative electrode precursor material, a silicon-carbon negative electrode material and a preparation method of the silicon-carbon negative electrode precursor material. Preparing a porous carbon material; performing vapor deposition on a silicon source on the porous carbon material to obtain a silicon / porous carbon material; putting boron oxide and the silicon / porous carbon material into a ball milling tank according to a mass ratio of (1-5): (80-200), and carrying out ball milling for 1-3 hours to obtain a silicon-carbon negative electrode precursor material; according to the silicon-carbon negative electrode precursor material, the silicon-carbon negative electrode material and the preparation method of the silicon-carbon negative electrode material, the porous carbon material is prepared from the biomass carbon material, the silicon element is deposited on the porous carbon material, the boron element is doped on the porous carbon material, and the obtained silicon-carbon negative electrode material has excellent capacity and capacity retention rate and high electrochemical stability.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon-carbon negative electrode, and in particular to a silicon-carbon negative electrode precursor material, a silicon-carbon negative electrode material and a preparation method thereof. Background Art

[0002] The structure of lithium-ion batteries is mainly composed of positive electrode, negative electrode, electrolyte, diaphragm, current collector and shell. The negative electrode material usually adopts carbon materials that can store lithium with high specific capacity, potential close to lithium potential and stable structure. The negative electrode materials actually used in lithium-ion batteries are basically carbon materials, such as artificial graphite, natural graphite, mesophase carbon microspheres, petroleum coke, carbon fiber, pyrolytic resin carbon, etc.

[0003] Biomass plays an important role in our daily life, but a large amount of biomass residue is usually left after use. These residues are often not effectively treated, causing large-scale environmental pollution, so the recycling of biomass carbon is urgent. The application of biocarbon in the negative electrode of lithium-ion batteries has excellent prospects for resource recycling. Summary of the invention

[0004] The purpose of the present invention is to provide a silicon-carbon negative electrode precursor material, a silicon-carbon negative electrode material and a preparation method thereof, and to prepare a porous carbon material using a biomass carbon material, deposit silicon elements on the porous carbon material and dope boron elements, so that the obtained silicon-carbon negative electrode material has excellent capacity and capacity retention rate, and high electrochemical stability.

[0005] To achieve the above-mentioned purpose, the present invention provides a silicon-carbon negative electrode precursor material, comprising a biomass carbon material, a silicon source and an activator, wherein the mass ratio of the biomass carbon material to the activator is 1:1-4.

[0006] Preferably, the biomass carbon material includes one or more of walnut shells, peanut shells, bagasse, bamboo shoots, straw and banana stems.

[0007] Preferably, the silicon source includes one or more of silane, silicon trichloride, silicon trifluoride, disilane, tetramethylsilane and hexamethyldisiloxane.

[0008] Preferably, the activator includes one or more of potassium carbonate, citric acid, urea, potassium ferrate, ammonium bicarbonate, a surfactant and potassium hydroxide.

[0009] The above-mentioned method for preparing a silicon-carbon negative electrode precursor material comprises the following steps:

[0010] S1. Pretreatment of biomass carbon material: crush the biomass carbon material and put it into a tubular furnace, and perform high-temperature carbonization at 500-800° C. under an inert atmosphere to obtain a carbonized biomass carbon material;

[0011] S2. Preparation of porous carbon material: the carbonized biomass carbon material obtained in S1 is mixed with an activator, dried and placed in a tubular furnace, kept at 700-1000° C. for 1-3 h under an inert atmosphere, washed to neutrality and then dried to obtain a porous carbon material;

[0012] S3, silicon source vapor deposition: the porous carbon material obtained in S2 is placed in a CVD furnace, evacuated and introduced with an inert gas, the temperature is raised to 400-500°C, silicon source gas is introduced for 1-2h, the silicon source gas and the inert gas are turned off, and the silicon / porous carbon material is obtained after cooling;

[0013] S4. Put the boron oxide and the silicon / porous carbon material obtained in S3 into a ball mill according to a mass ratio of 1-5:80-200, and obtain a silicon-carbon negative electrode precursor material after ball milling for 1-3 hours.

[0014] Preferably, in S1, the pulverizing is to wash and dry the biomass carbon material and then put it into a pulverizer, and the pulverized particle size is 10-30 microns.

[0015] Preferably, in S2, washing is performed by acid washing and deionized water washing in sequence, which is repeated 2-3 times until neutral.

[0016] Preferably, in S3, the flow rate of the inert gas is 1.2-5.0 L / min, and the flow rate of the silicon source is 0.8-2 L / min.

[0017] Preferably, in S3, the inert gas is one or more of argon, nitrogen, helium and neon.

[0018] A silicon-carbon negative electrode material is obtained by mixing the above-mentioned silicon-carbon negative electrode precursor material with a binder, a conductive agent and a solvent.

[0019] Therefore, the present invention adopts the above-mentioned silicon-carbon negative electrode precursor material, silicon-carbon negative electrode material and preparation method thereof, and its beneficial effects are:

[0020] 1. The present invention uses biomass carbon materials to prepare porous carbon materials, deposits silicon elements on the porous carbon materials and dopes boron elements, and the obtained silicon-carbon negative electrode material has excellent capacity and capacity retention rate, and high electrochemical stability;

[0021] 2. The specific surface area of ​​the porous carbon material provided by the present invention is 1800-2000m 2 / g, micropores account for more than 88%, of which micropores of 0.7-1nm account for 10-25% of the total micropores, and mesopores account for 1-5%.

[0022] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the first round charge and discharge curve diagram of Example 4 and Example 5 of the present invention. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with the accompanying drawings and embodiments. Unless otherwise defined, the technical terms or scientific terms used in the present invention should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs. The above-mentioned features or features mentioned in the specific examples mentioned in the present invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0025] Example 1

[0026] A method for preparing a silicon-carbon negative electrode precursor material comprises the following steps:

[0027] S1. Pretreatment of biomass carbon material: After washing and drying the banana stems, put them into a crusher, put the crushed banana stems with a particle size of 30 microns into a tubular furnace, and perform high-temperature carbonization at 800° C. under an inert atmosphere to obtain carbonized biomass carbon material.

[0028] S2. Preparation of porous carbon material: The carbonized biomass carbon material obtained in S1 was mixed with a mixture of urea and citric acid in a mass ratio of 1:3, dried and placed in a tube furnace, kept at 1000°C for 2.5 hours under an inert atmosphere, washed to neutrality and then dried to obtain a porous carbon material. The porous carbon material has a partially graphitized amorphous structure and a specific surface area of ​​1980 m 2 / g, micropores account for 88%, of which micropores of 0.7-1nm account for 15% of the total micropores, and mesopores account for 3%, forming a hierarchical porous carbon structure dominated by micropores.

[0029] In S2, washing is performed by acid washing and deionized water washing in sequence, which are repeated 2-3 times until neutral.

[0030] S3, silicon source vapor deposition: the porous carbon material obtained in S2 is placed in a CVD furnace, evacuated and then introduced with argon gas at a flow rate of 4.5 L / min, the temperature is raised to 450°C, silane gas is introduced for 1 h, the flow rate of the silicon source is 1.5 L / min, the silane gas and argon gas are turned off, and the silicon / porous carbon material is obtained after cooling;

[0031] S4. Put the boron oxide and the silicon / porous carbon material obtained in S3 into a ball mill at a mass ratio of 1:100, a ball-to-material ratio of 10:1, a ball mill speed of 350 r / min, and perform alternating forward and reverse ball milling for 2 hours to obtain a silicon-carbon negative electrode precursor material.

[0032] Example 2

[0033] A method for preparing a silicon-carbon negative electrode precursor material comprises the following steps:

[0034] S1. Pretreatment of biomass carbon material: Wash and dry the peanut shells and put them into a crusher. Put the crushed peanut shells with a particle size of 20 microns into a tubular furnace and perform high-temperature carbonization at 800° C. under an inert atmosphere to obtain carbonized biomass carbon material.

[0035] S2. Preparation of porous carbon material: The carbonized biomass carbon material obtained in S1 was mixed with potassium carbonate and potassium hydroxide in a mass ratio of 1:4, dried and placed in a tube furnace, kept at 900°C for 1.5 hours under an inert atmosphere, washed to neutrality and then dried to obtain a porous carbon material. The porous carbon material has a partially graphitized amorphous structure and a specific surface area of ​​1800m 2 / g, micropores account for 88% and mesopores account for 5%.

[0036] In S2, washing is performed by acid washing and deionized water washing in sequence, which are repeated 2-3 times until neutral.

[0037] S3, silicon source vapor deposition: put the porous carbon material obtained in S2 into a CVD furnace, evacuate and introduce neon gas at a flow rate of 2.5 L / min. Raise the temperature to 450°C, introduce silicon source gas for 1.2 h at a flow rate of 0.8 L / min, turn off the silicon source gas and neon gas, cool down and obtain silicon / porous carbon material;

[0038] S4. Put the boron oxide and the silicon / porous carbon material obtained in S3 into a ball mill at a mass ratio of 1:98, a ball-to-material ratio of 10:1, a ball mill speed of 350 r / min, and perform forward and reverse alternating ball milling for 2 hours to obtain a silicon-carbon negative electrode precursor material.

[0039] Example 3

[0040] A method for preparing a silicon-carbon negative electrode precursor material comprises the following steps:

[0041] S1. Pretreatment of biomass carbon materials: Wash and dry the bagasse and put it into a crusher. Put the crushed bagasse with a particle size of 10 microns into a tubular furnace and perform high-temperature carbonization at 600° C. under an inert atmosphere to obtain a carbonized biomass carbon material.

[0042] S2. Preparation of porous carbon material: The carbonized biomass carbon material obtained in S1 was mixed with a mixture of urea and citric acid in a mass ratio of 1:3, dried and placed in a tube furnace, kept at 700°C for 2 hours under an inert atmosphere, washed to neutrality and then dried to obtain a porous carbon material. The porous carbon material has a partially graphitized amorphous structure and a three-dimensional interconnected hierarchical porous carbon structure with a specific surface area of ​​2000m 2 / g, micropores account for 90%, which is conducive to storing more charges, of which 0.7-1nm micropores account for 20% of the total micropores, and mesopores account for 5%.

[0043] In S2, washing is performed by acid washing and deionized water washing in sequence, which are repeated 2-3 times until neutral.

[0044] S3, silicon source vapor deposition: the porous carbon material obtained in S2 is placed in a CVD furnace, evacuated and then introduced with argon gas at a flow rate of 3 L / min, the temperature is raised to 450°C, silane gas is introduced for 2 h at a flow rate of 1 L / min, the silane gas and the inert gas are turned off, and the silicon / porous carbon material is obtained after cooling;

[0045] S4. Put the boron oxide and the silicon / porous carbon material obtained in S3 into a ball mill at a mass ratio of 2:191, a ball-to-material ratio of 10:1, a ball mill speed of 350 r / min, and perform alternating forward and reverse ball milling for 2 hours to obtain a silicon-carbon negative electrode precursor material.

[0046] Example 4

[0047] The silicon-carbon negative electrode precursor material obtained in Example 1, the binder polypyrrole, the conductive agent graphene and the solvent N-methylpyrrolidone are mixed to obtain a silicon-carbon negative electrode material.

[0048] Example 5

[0049] The silicon-carbon negative electrode precursor material obtained in Example 2, the binder polypyrrole, the conductive agent graphene and the solvent N-methylpyrrolidone are mixed to obtain a silicon-carbon negative electrode material.

[0050] Example 6

[0051] The silicon-carbon negative electrode precursor material obtained in Example 3, the binder polypyrrole, the conductive agent graphene and the solvent N-methylpyrrolidone are mixed to obtain a silicon-carbon negative electrode material.

[0052] Comparative Example 1

[0053] S1. Pretreatment of biomass carbon material: After washing and drying the banana stems, put them into a crusher, put the crushed banana stems with a particle size of 30 microns into a tubular furnace, and perform high-temperature carbonization at 800° C. under an inert atmosphere to obtain carbonized biomass carbon material.

[0054] S2. Preparation of porous carbon material: The carbonized biomass carbon material obtained in S1 is mixed with a mixture of urea and citric acid in a mass ratio of 1:3, dried and placed in a tubular furnace, kept warm at 1000°C for 2.5h under an inert atmosphere, washed to neutrality and then dried to obtain a porous carbon material.

[0055] In S2, washing is performed by acid washing and deionized water washing in sequence, which are repeated 2-3 times until neutral.

[0056] S3, silicon source vapor deposition: the porous carbon material obtained in S2 is placed in a CVD furnace, evacuated and then introduced with argon gas at a flow rate of 4.5 L / min, the temperature is raised to 400-500°C, silane gas is introduced for 1-2 hours, the flow rate of the silicon source is 1.5 L / min, the silane gas and argon gas are turned off, and the silicon / porous carbon material is obtained after cooling.

[0057] Comparative Example 2

[0058] The silicon / porous carbon material obtained in Comparative Example 1, the binder polypyrrole, the conductive agent graphene and the solvent N-methylpyrrolidone were mixed to obtain a silicon-carbon negative electrode material.

[0059] Test Example 1

[0060] a. The capacity retention rates of Examples 4-6 and Comparative Example 2 after 100 cycles are shown in Table 1. It can be seen that the capacity retention rates of the silicon-carbon negative electrode materials of Examples 4-6 are relatively high, and the addition of boron element inhibits the growth of lithium dendrites.

[0061] Table 1. Capacity retention rate of Examples 4-6 and Comparative Example 2 after 100 cycles

[0062]

[0063] b. The first round of charge and discharge tests were performed on Example 4 and Example 5 at a current density of 0.2C. The results are as follows: Figure 1 As shown, it can be seen that the silicon-carbon negative electrode materials obtained in Example 4 and Example 5 have a higher first-cycle capacity, and the porous carbon material prepared from the biomass carbon material has abundant pores.

[0064] Therefore, the present invention adopts the above-mentioned silicon-carbon negative electrode precursor material and silicon-carbon negative electrode material, uses biomass carbon material to prepare porous carbon material, deposits silicon element on the porous carbon material and dopes boron element, and the obtained silicon-carbon negative electrode material has excellent capacity and capacity retention rate, and high electrochemical stability.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A silicon-carbon negative electrode precursor material, characterized in that: The invention comprises a biomass carbon material, a silicon source and an activator, wherein the mass ratio of the biomass carbon material to the activator is 1:1-4.

2. The silicon-carbon negative electrode precursor material according to claim 1, characterized in that: The biomass carbon material includes one or more of walnut shells, peanut shells, bagasse, bamboo shoots, straw and banana stems.

3. The silicon-carbon negative electrode precursor material according to claim 1, characterized in that: The silicon source includes one or more of silane, silicon trichloride, silicon trifluoride, disilane, tetramethylsilane and hexamethyldisiloxane.

4. The silicon-carbon negative electrode precursor material according to claim 1, characterized in that: The activator includes one or more of potassium carbonate, citric acid, urea, potassium ferrate, ammonium bicarbonate, a surfactant and potassium hydroxide.

5. A method for preparing a silicon-carbon negative electrode precursor material according to any one of claims 1 to 4, characterized in that: The following steps are included: S1. Pretreatment of biomass carbon material: crush the biomass carbon material and put it into a tubular furnace, and perform high-temperature carbonization at 500-800° C. under an inert atmosphere to obtain a carbonized biomass carbon material; S2. Preparation of porous carbon material: the carbonized biomass carbon material obtained in S1 is mixed with an activator, dried and placed in a tubular furnace, kept at 700-1000° C. for 1-3 h under an inert atmosphere, washed to neutrality and then dried to obtain a porous carbon material; S3, silicon source vapor deposition: the porous carbon material obtained in S2 is placed in a CVD furnace, evacuated and introduced with an inert gas, the temperature is raised to 400-500°C, silicon source gas is introduced for 1-2h, the silicon source gas and the inert gas are turned off, and the silicon / porous carbon material is obtained after cooling; S4. Put the boron oxide and the silicon / porous carbon material obtained in S3 into a ball mill according to a mass ratio of 1-5:80-200, and obtain a silicon-carbon negative electrode precursor material after ball milling for 1-3 hours.

6. The method for preparing a silicon-carbon negative electrode precursor material according to claim 5, characterized in that: In S1, the biomass carbon material is pulverized by washing, drying and then putting it into a pulverizer, and the pulverized particle size is 10-30 microns.

7. The method for preparing a silicon-carbon negative electrode precursor material according to claim 5, characterized in that: In S2, washing is performed by acid washing and deionized water washing in sequence, which are repeated 2-3 times until neutral.

8. The method for preparing a silicon-carbon negative electrode precursor material according to claim 5, characterized in that: In S3, the flow rate of the inert gas is 1.2-5.0 L / min, and the flow rate of the silicon source is 0.8-2 L / min.

9. The method for preparing a silicon-carbon negative electrode precursor material according to claim 5, characterized in that: In S3, the inert gas is one or more of argon, nitrogen, helium and neon.

10. A silicon-carbon negative electrode material, characterized in that: The silicon-carbon negative electrode precursor material according to any one of claims 1 to 4 is mixed with a binder, a conductive agent and a solvent to obtain a silicon-carbon negative electrode material.

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