Metal-doped carbon-coated micron silicon composite material and preparation method thereof
By using peach gum and nickel metal compounds to prepare metal-doped carbon-coated micron silicon composite materials, the problems of existing carbon-coated silicon-based materials in cycle stability and conductivity were solved, and low-cost, high-performance lithium-ion battery negative electrode materials were achieved.
Patent Information
- Application Number
- CN202510592472.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-09
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2045-05-09
AI Technical Summary
The existing carbon-coated silicon-based lithium-ion battery negative electrode materials still need to be improved in terms of cycle stability, rate performance and reversibility. Traditional carbon source materials are expensive, pollute the environment and have complex processes.
Peach gum is used as a carbon source and doped with nickel metal compounds. Metal-doped carbon-coated micron silicon composite materials are prepared by low-temperature calcination to form a uniform carbon layer to alleviate the volume change of silicon and improve conductivity.
The material's cycle stability, rate performance and reversibility are significantly improved, production costs and energy consumption are reduced, and the material has excellent performance and good market competitiveness.
Smart Images
Figure CN120117600B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of negative electrode materials for lithium-ion batteries, and in particular relates to a metal-doped carbon-coated micron silicon composite material and a preparation method thereof. Background Art
[0002] Lithium-ion batteries are widely used in portable electronic devices, electric vehicles, and other fields due to their high energy density and long cycle life. However, traditional graphite anode materials have a low theoretical specific capacity (372 mAh / g), which no longer meets the demand for high-energy-density batteries. Silicon, as an anode material, has a theoretical specific capacity of up to 4200 mAh / g and is considered the preferred anode material for next-generation lithium-ion batteries. However, silicon undergoes significant volume expansion (approximately 300%) during charge and discharge, leading to structural damage and rapid capacity decay.
[0003] To overcome this problem, researchers have developed a variety of modification methods, among which carbon coating is an effective strategy. The carbon layer can not only buffer the volume change of silicon, but also improve the conductivity of the material. However, the existing carbon-coated materials still need to be further improved in terms of cycle stability, rate performance and reversibility. Summary of the Invention
[0004] To address the shortcomings of existing technologies, the present invention provides a metal-doped carbon-coated micron silicon composite material and its preparation method. This invention uses peach gum as a carbon source and simultaneously incorporates a nickel metal compound. The combination of these two improves the structure and electrochemical properties of the silicon-carbon composite material, significantly enhancing its cycling stability, rate capability, and reversibility.
[0005] To achieve the above object, the present invention specifically adopts the following technical solutions:
[0006] The present invention provides a method for preparing a metal-doped carbon-coated micron silicon composite material, comprising the following steps:
[0007] Step 1: Add micron silicon to water and perform ultrasonic treatment to obtain a dispersion, grind peach gum into small particles and add them to the micron silicon dispersion, stir thoroughly, and obtain a mixed solution for later use;
[0008] Step 2: Add nickel chloride hexahydrate solution dropwise to the mixed solution obtained in step 1, stir thoroughly, and freeze-dry;
[0009] Step 3: calcining the freeze-dried sample obtained in step 2 at 350-600° C. to obtain a metal-doped carbon-coated micron silicon composite material.
[0010] Furthermore, the size range of the micron silicon in step 1 is 1-3 μm.
[0011] Furthermore, the purity of the peach gum in step 1 is not less than 99%, and the composition is: polysaccharides 70%-90%, protein 2%-5%, moisture not exceeding 15%, and ash not exceeding 3%.
[0012] Furthermore, in step 1, the mass ratio of micron silicon to peach gum is 1:(2-4).
[0013] Furthermore, the conditions for sufficient stirring in step 1 are: 50° C. oil bath, stirring speed of 800 rpm, and time of 4 h.
[0014] Furthermore, the concentration of the nickel chloride hexahydrate solution in step 2 is 5%, and the amount of nickel chloride hexahydrate added is 4%-6% of the mass of the micron silicon.
[0015] Furthermore, the freeze-drying temperature in step 2 is -40°C and the processing time is 12 h.
[0016] Furthermore, the calcination in step 3 is carried out under an argon atmosphere, and the calcination treatment time is 1-3 h.
[0017] The present invention also provides a metal-doped carbon-coated micron silicon composite material obtained by the above preparation method.
[0018] Traditional silicon-carbon composite materials generally use materials such as asphalt and phenolic resin as carbon sources. Such solutions have high production costs, pollute the environment, and have complex processes. The present invention uses peach gum as a carbon source, which is green, environmentally friendly, and inexpensive. It is mainly composed of macromolecular polysaccharides and has good water absorption. It forms a sol-gel in a dispersed silicon particle solution and easily forms a strong bond (hydrogen bond) with the surface of the silicon particles, making the carbon layer of the silicon-carbon precursor before carbonization more uniform, improving the uniformity and structural stability of the outer carbon layer, and helping to alleviate the damage caused by the violent expansion of silicon to the carbon matrix framework during multiple charge and discharge processes. At the same time, the porous network structure of peach gum will enhance the cross-linking effect under the action of nickel ions, and can capture nickel ions through physical adsorption (such as electrostatic action and van der Waals force), thereby enhancing the degree of intermolecular bonding. Peach gum contains a small amount of glucuronic acid, and its carboxylate (-COO - ) can bind nickel ions through monodentate or bidentate coordination to form electronegative cavities; and the nickel ions in the structure can significantly promote the degree of graphitization of peach gum carbon through mechanisms such as dissolution-precipitation, surface diffusion and carbide intermediates, thereby enhancing the conductivity of the carbon layer.
[0019] Typically, the temperature required for the graphitization process is between 2300-3000°C, but the present invention can produce ordered carbon layers with a high degree of graphitization under low temperature conditions. Under low calcination temperature conditions, peach gum can only be partially carbonized. Therefore, the present invention introduces nickel chloride hexahydrate into the doping process, which can accelerate graphitization. Under low-temperature calcination conditions, it can catalyze the carbon layer to promote the degree of graphitization. This not only effectively reduces process energy consumption, but also promotes the transformation of peach gum into graphite carbon with a three-dimensional ordered structure, improves the electrical conductivity of the silicon-carbon material, and enhances the stability of the electrochemical structure.
[0020] The beneficial effects of the present invention are:
[0021] The process of the present invention utilizes peach gum combined with a nickel metal compound to produce a highly graphitized, ordered carbon layer under low-temperature carbonization conditions. This significantly increases the electrical conductivity of the resulting silicon-carbon material while also improving the surface wettability of the composite material, thereby effectively enhancing its electrochemical performance. The process is simple, energy-efficient, and utilizes a broad and inexpensive supply of micron-sized silicon powder and carbon sources. The resulting metal-doped carbon-coated micron-silicon composite material exhibits excellent performance and strong market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 This is a 1C cycle test chart of the composite material 52345 soft-pack full battery prepared in Examples 1-3 of the present invention and Comparative Examples 1-3.
[0023] Figure 2 2C cycle test chart of composite 18650 steel shell full battery prepared in Example 1 and Comparative Examples 1-3 of the present invention.
[0024] Figure 3 These are the EIS graphs of the composite material button-type half-cells prepared in Example 1 of the present invention and Comparative Examples 1-3.
[0025] Figure 4 This is the SEM image of the composite material prepared in Example 1 of the present invention. DETAILED DESCRIPTION
[0026] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.
[0027] Example 1
[0028] A method for preparing a metal-doped carbon-coated micron silicon composite material, comprising the following steps:
[0029] 1. Weigh micron silicon and peach gum in a mass ratio of 1:3. Add micron silicon to deionized water (solid-liquid ratio 1:50) and ultrasonically disperse it. Grind the peach gum into small particles (30-50 μm) and add it to the dispersion. Stir in an oil bath at 50°C and 800 rpm for 4 hours to obtain a mixed solution.
[0030] 2. Take nickel chloride hexahydrate and dissolve it in deionized water to prepare a solution with a concentration of 5%. Add the prepared nickel chloride hexahydrate solution dropwise to the mixed solution (the amount of addition is based on the mass ratio of nickel chloride hexahydrate to micron silicon of 0.05:1), and then stir at room temperature for 12 hours. The obtained stirred solution is transferred to -40°C and kept for 12 hours for freeze drying. The obtained sample is placed in a furnace under argon protection, and the temperature is increased to 600°C at 5°C / min and calcined for 2 hours to obtain a metal-doped carbon-coated micron silicon composite material.
[0031] Example 2
[0032] A method for preparing a metal-doped carbon-coated micron silicon composite material, comprising the following steps:
[0033] 1. Weigh micron silicon and peach gum in a mass ratio of 1:2. Add micron silicon to deionized water (solid-liquid ratio 1:50) and ultrasonically disperse it. Grind the peach gum into small particles (30-50 μm) and add it to the dispersion. Stir in an oil bath at 50°C and 800 rpm for 4 hours to obtain a mixed solution.
[0034] 2. Take nickel chloride hexahydrate and dissolve it in deionized water to make a solution with a concentration of 5%. Add the prepared nickel chloride hexahydrate solution dropwise to the mixed solution (the amount of addition is based on the mass ratio of nickel chloride hexahydrate to micron silicon of 0.05:1), and then stir at room temperature for 12 hours. The obtained stirred solution is transferred to -40°C and kept for 12 hours for freeze drying. The obtained sample is placed in a furnace under argon protection, and the temperature is increased to 500°C at 5°C / min and calcined for 2 hours to obtain a metal-doped carbon-coated micron silicon composite material.
[0035] Example 3
[0036] A method for preparing a metal-doped carbon-coated micron silicon composite material, comprising the following steps:
[0037] 1. Weigh micron silicon and peach gum in a mass ratio of 1:4. Add micron silicon to deionized water (solid-liquid ratio 1:50) and ultrasonically disperse. Grind the peach gum into small particles (30-50 μm) and add it to the dispersion. Stir in an oil bath at 50°C and 800 rpm for 4 hours to obtain a mixed solution.
[0038] 2. Take nickel chloride hexahydrate and dissolve it in deionized water to make a solution with a concentration of 5%. Add the prepared nickel chloride hexahydrate solution dropwise to the mixed solution (the amount of addition is based on the mass ratio of nickel chloride hexahydrate to micron silicon of 0.05:1), and then stir at room temperature for 12 hours. The obtained stirred solution is transferred to -40°C and kept for 12 hours for freeze drying. The obtained sample is placed in a furnace under argon protection, and the temperature is increased to 400°C at 5°C / min and calcined for 2 hours to obtain a metal-doped carbon-coated micron silicon composite material.
[0039] Comparative Example 1
[0040] A method for preparing a metal-doped carbon-coated micron silicon composite material, comprising the following steps:
[0041] 1. Weigh micron silicon and peach gum in a mass ratio of 1:3. Add micron silicon to deionized water (solid-liquid ratio 1:50) and ultrasonically disperse it. Grind the peach gum into small particles (30-50 μm) and add it to the dispersion. Stir in an oil bath at 50°C and 800 rpm for 4 hours to obtain a mixed solution.
[0042] 2. Take copper chloride hexahydrate and dissolve it in deionized water to make a solution with a concentration of 5%. Add the prepared copper chloride hexahydrate solution dropwise to the mixed solution (the amount of addition is based on the mass ratio of copper chloride hexahydrate to micron silicon of 0.05:1), then stir at room temperature for 12 hours. Transfer the obtained stirred solution to -40°C and keep it at -40°C for 12 hours for freeze drying. Place the obtained sample in a furnace under argon protection, heat it to 600°C at 5°C / min and calcine it for 2 hours to obtain a metal-doped carbon-coated micron silicon composite material.
[0043] Comparative Example 2
[0044] A method for preparing a metal-doped carbon-coated micron silicon composite material, comprising the following steps:
[0045] 1. Weigh micron silicon and sodium alginate (viscosity 200±20 mPa.s, 98%) powders in a mass ratio of 1:3. Add the micron silicon to deionized water (solid-to-liquid ratio 1:50) and ultrasonically disperse it. Then add the sodium alginate powder to the dispersion and stir in an oil bath at 50°C and 800 rpm for 4 hours to obtain a mixed solution.
[0046] 2. Take nickel chloride hexahydrate and dissolve it in deionized water to prepare a solution with a concentration of 5%. Add the prepared nickel chloride hexahydrate solution dropwise to the mixed solution (the amount of addition is based on the mass ratio of nickel chloride hexahydrate to micron silicon of 0.05:1), and then stir at room temperature for 12 hours. The obtained stirred solution is transferred to -40°C and kept for 12 hours for freeze drying. The obtained sample is placed in a furnace under argon protection, and the temperature is increased to 600°C at 5°C / min and calcined for 2 hours to obtain a metal-doped carbon-coated micron silicon composite material.
[0047] Comparative Example 3
[0048] A method for preparing a metal-doped carbon-coated micron silicon composite material, comprising the following steps:
[0049] 1. Weigh micron silicon and sodium carboxymethyl cellulose (viscosity 600-1000 mPa.s, AR) powders in a mass ratio of 1:3. Add the micron silicon to deionized water (solid-to-liquid ratio 1:50) and ultrasonically disperse it. Then add the sodium carboxymethyl cellulose powder to the dispersion and stir in an oil bath at 50°C and 800 rpm for 4 hours to obtain a mixed solution.
[0050] 2. Take nickel chloride hexahydrate and dissolve it in deionized water to prepare a solution with a concentration of 5%. Add the prepared nickel chloride hexahydrate solution dropwise to the mixed solution (the amount of addition is based on the mass ratio of nickel chloride hexahydrate to micron silicon of 0.05:1), and then stir at room temperature for 12 hours. The obtained stirred solution is transferred to -40°C and kept for 12 hours for freeze drying. The obtained sample is placed in a furnace under argon protection, and the temperature is increased to 600°C at 5°C / min and calcined for 2 hours to obtain a metal-doped carbon-coated micron silicon composite material.
[0051] Test example
[0052] In order to detect the performance of the lithium ion battery negative electrode material prepared by the present invention, the half-cell test method, 18650 steel shell full battery, 523450 soft package full battery, scanning electron microscope, specific surface area and porosity analyzer were used for testing.
[0053] 18650 steel-cased full-cell: A standard lithium-ion battery model, where 18 represents an 18 mm diameter, 65 represents a 65 mm length, and 0 represents a cylindrical battery. 523450 soft-pack full-cell: A standard soft-pack lithium-ion battery model, where 52 represents a 5.2 mm thickness, 34 represents a 34 mm width, and 50 represents a 50 mm length.
[0054] The half-cell testing method involves preparing an electrode slurry with a mass ratio of active material: conductive agent: binder of 6:2:2. The slurry is coated on copper foil, dried under vacuum at 60°C for 12 hours, cut into 12 mm diameter circular electrode pieces, and assembled into a button-type half-cell.
[0055] The 18650 steel-cased full-cell battery is composed of lithium nickel cobalt manganese oxide (high nickel) as the positive electrode material and silicon-carbon composite graphite as the negative electrode material. The positive electrode slurry is formulated with a ratio of active material: PVDF: SP = 95%: 2.5%: 2.5%. The slurry is then coated on aluminum foil and vacuum-dried for 24 hours to form the positive electrode sheet. The negative electrode slurry is formulated with a ratio of active material: PAA / CMC: SBR: SP: SWCNT = 95%: 2%: 1%: 1%: 1%. The slurry is then coated on copper foil and vacuum-dried for 24 hours to form the negative electrode sheet. The electrolyte was purchased commercially, and the separator was a PE film. After electrode rolling, slitting, and winding, the cells were assembled into full batteries in a glove box. After a 100% charge quantization layer and a 0.1 C-10 C capacity gradient, constant current charge and discharge experiments were conducted on a LAND battery testing system. Unless otherwise specified, the following data are based on 1 C-10 C charge and discharge cycles, with charge and discharge voltages limited to 2.75 V-4.2 V. Data were collected using a computer-controlled charge and discharge cabinet.
[0056] The 523450 soft-pack full-cell battery is composed of lithium iron phosphate as the positive electrode material and silicon-carbon composite graphite as the negative electrode material. The positive electrode slurry is formulated with a ratio of active material: PVDF: SP = 96%:2%:2%. The slurry is then coated on aluminum foil and vacuum-dried for 24 hours to form the positive electrode sheet. The negative electrode slurry is formulated with a ratio of active material: PAA / CMC:SBR:SP:SWCNT = 95%:2%:1%:1%:1%. The slurry is then coated on copper foil and vacuum-dried for 24 hours to form the negative electrode sheet. The electrolyte was purchased commercially, and the separator was a PE film. After electrode rolling, slitting, and winding, the cells were assembled into full batteries in a glove box. After passing through an 80% charge quantization layer and a 0.1 C-10 C capacity separation, constant current charge and discharge experiments were conducted on a LAND battery testing system. Unless otherwise specified, the following data are based on 1 C-10 C charge and discharge cycles, with charge and discharge voltages limited to 2.75-4.2 V. Data were collected using a computer-controlled charge and discharge cabinet.
[0057] The material composition and crystal structure were analyzed using a PertPowder X-ray diffractometer (Cu target Ka radiation source, voltage 40 kV, current 40 mA, scan rate 6° / min). The morphology and structure of the samples were analyzed using Tecnai G2 F20 high-resolution transmission electron microscopes and Tecnai G2 F20 high-resolution transmission electron microscopes. Electrochemical performance (CV, EIS, etc.) of the assembled button-type half-cells was tested using an electrochemical workstation (CHI600E). Long-cycle performance data of 18650 / 523450 full cells was collected using a Blue Electric test cabinet and a Newway test cabinet. The test results are shown in Table 1.
[0058] Table 1 Button half-cell test results
[0059]
[0060] It can be seen from the button half-cell test data in Table 1 that the first charge and discharge specific capacity and coulombic efficiency provided by the composite materials of Examples 1-3 are better than those of the comparative example. Due to the low calcination temperature, peach gum carbon can only be partially carbonized. Although the graphitized carbon layer formed by the peach gum carbon doped with nickel ions has excellent conductivity after carbonization, the graphitized carbon layer itself lacks lithium deintercalation sites. In addition, the introduction of nickel ions also enhances the toughness of the carbon layer framework of the silicon-carbon material. Therefore, the electrochemical properties such as specific capacity and coulombic efficiency of the embodiment are better than those of the comparative example. During the pyrolysis of the biomass material after copper ion incorporation, Cu 2+ Loading on the surface promotes the decomposition of tar and other substances into small molecular gases (H2, CO, etc.), increasing the specific surface area, but reduces the carbonization efficiency or causes the carbon material structure to become disordered. This structure has lower conductivity than the embodiment with a high degree of graphitization. For this reason, the first coulombic efficiency of Comparative Example 1 is lower. In addition, the peach gum carbon source used in the embodiment has special water absorption properties. In the precursor carbon-silicon mixed solution, the silicon particles can be uniformly adsorbed in the cavities formed by the colloid, forming a uniform carbon layer structure after carbonization. However, the sodium alginate carbon source used in Comparative Example 2 and the sodium carboxymethyl cellulose carbon source used in Comparative Example 3 did not achieve this effect.
[0061] Figure 1 This is a 1C cycle test chart of the composite material 52345 soft-pack full battery prepared in Examples 1-3 of the present invention and Comparative Examples 1-3. Figure 1 It can be seen from the first 160 cycles of the 523450 soft pack fully charged that the embodiment has excellent cycle stability. Within the 80% capacity life range, its capacity attenuation trend is much smaller than that of the comparative example.
[0062] Figure 2 This is a graph showing the cycle test of a full battery with a composite material 18650 steel shell prepared in Example 1 and Comparative Examples 1-3 of the present invention. Figure 2 It can be seen that Example 1 has a 400-cycle cycle retention rate of >85% under 2C cycle conditions, has good cycle performance, and can be applied to 3C, energy storage and other fields. The downward trend of its long-cycle capacity retention rate is much smaller than that of Comparative Examples 1-3.
[0063] Figure 3 The EIS diagram of the composite material button half-cell prepared in Example 1 and Comparative Examples 1-3 of the present invention. Figure 3From the electrochemical impedance spectroscopy, it can be seen that with the introduction of nickel ions, the degree of graphitization of the carbon layer of the materials in Example 1 and Comparative Examples 2 and 3 changes, and their impedance decreases accordingly. The ohmic impedance and charge impedance of Comparative Example 1 doped with metal copper ions are much greater than those of the sample doped with nickel ions. The impedance values of Example 1 are all smaller than those of all comparative examples, which is due to the uniform distribution of the coating layer of peach gum carbon precursor on the silicon surface.
[0064] Figure 4 This is the SEM image of the composite material prepared in Example 1 of the present invention. Figure 4 It can be observed from the SEM image in the figure that the micron silicon particles in Example 1 are uniformly wrapped by the carbon layer without serious agglomeration. The particle surface shows a dense graphitized carbon layer and tiny graphite balls caused by nickel are observed.
[0065] Finally, it should be emphasized that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A method for preparing a metal-doped carbon-coated micron silicon composite material, characterized in that: The steps include: Step 1: Add micron silicon to water and perform ultrasonic treatment to obtain a dispersion, grind peach gum into small particles and add them to the micron silicon dispersion, stir thoroughly, and obtain a mixed solution for later use; Among them, the size range of micron silicon is 1-3 μm, and the mass ratio of micron silicon to peach gum is 1:(2-4); Step 2: Add nickel chloride hexahydrate solution dropwise to the mixed solution obtained in step 1, stir thoroughly, and freeze-dry; Among them, the addition amount of nickel chloride hexahydrate is 4%-6% of the mass of micron silicon; Step 3: calcining the freeze-dried sample obtained in step 2 at 350-600° C. to obtain a metal-doped carbon-coated micron silicon composite material.
2. The method for preparing the metal-doped carbon-coated micron silicon composite material according to claim 1, characterized in that: The conditions for sufficient stirring in step 1 are: 50°C oil bath, stirring speed of 800 rpm, and time of 4 h.
3. The method for preparing the metal-doped carbon-coated micron silicon composite material according to claim 1, characterized in that: The concentration of the nickel chloride hexahydrate solution in step 2 is 5%.
4. The method for preparing the metal-doped carbon-coated micron silicon composite material according to claim 1, characterized in that: The freeze-drying temperature in step 2 is -40°C and the processing time is 12 h.
5. The method for preparing the metal-doped carbon-coated micron silicon composite material according to claim 1, characterized in that: The calcination in step 3 is carried out under an argon atmosphere, and the calcination treatment time is 1-3 h.
6. The metal-doped carbon-coated micron silicon composite material obtained by the preparation method according to any one of claims 1 to 5.