Carbon-coated submicron silicon dioxide negative electrode material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of batteries, and discloses a carbon-coated submicron silicon dioxide negative electrode material as well as a preparation method and application thereof. The preparation method comprises the following steps: by taking biomass derived silicon dioxide and reducing carbohydrates as main preparation raw materials, carrying out acid pickling and ball milling on silicon dioxide to obtain submicron silicon dioxide particles; the reducing carbohydrates grow a carbon layer with a porous structure on the surface of the submicron silicon dioxide in situ through a hydrothermal reaction, and the carbon-coated submicron silicon dioxide negative electrode material is synthesized. The material combines the characteristics of high capacity of a siloxy active material and high conductivity and high stability of a carbon-based material, so that the energy density of the battery can be remarkably improved; and the porous carbon layer is grown on the surface, and a conductive network is constructed, so that the proportion of the active silicon dioxide is increased, the volume expansion of the silicon dioxide in the lithium intercalation process is effectively inhibited, and the structural stability and the cycling stability of the material are further improved.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and particularly relates to a carbon-coated submicron-sized silicon dioxide anode material, its preparation method, and its application. Background Technology

[0002] Silicon, as an alloying material, can combine with Li + During alloying / dealloying reactions, the theoretical capacity reaches as high as 4200 mAh / g. With its low operating voltage (0.4V) and ultra-high theoretical capacity, silicon has become a strong contender for next-generation lithium-ion battery anode materials. However, silicon anodes experience significant volume expansion (>300%) during charge and discharge, which directly leads to electrode pulverization, capacity loss, and ultimately affects battery life.

[0003] Compared to silicon anodes, silicon dioxide generates lithium oxide and lithium silicate salts during lithium intercalation, effectively mitigating volume expansion during charge and discharge. Meanwhile, silicon dioxide has attracted considerable attention due to its high theoretical capacity (1950 mAh / g), low discharge voltage (0.2 V), and low cost. However, its extremely poor conductivity and persistent volume expansion limit its practical application in lithium-ion battery anode materials. Current solutions mainly include reducing silicon dioxide particle size, constructing nanostructures, and combining silicon dioxide with high-conductivity materials. However, the application of silicon dioxide in lithium-ion battery anode materials faces significant challenges due to high manufacturing costs and substantial environmental hazards. Summary of the Invention

[0004] This invention aims to solve the technical problems of decreased thermal and chemical stability, rapid capacity decay, and poor cycle stability of silicon-containing anode materials in lithium-ion batteries during application. This invention provides a porous carbon-coated submicron-sized biomass-derived silica anode material, its preparation method, and its application. An amorphous pyrolytic carbon coating layer is grown in situ on the surface of submicron-sized silica using a hydrothermal method, constructing a conductive network. This effectively reduces the resistivity of the silica material, enhances its conductivity, increases the proportion of active silica, suppresses capacity decay caused by the volume expansion of the silica-based material, and improves the stability of the SEI film at the electrolyte interface. The prepared anode material exhibits high specific capacity, excellent cycle performance, and cycle stability.

[0005] The inventive concept of this invention is as follows: This invention uses biomass-derived silica and reducing sugars as the main raw materials. Specifically, the biomass-derived silica is acid-washed and ball-milled to obtain submicron-sized silica particles. The reducing sugars serve as the carbon source, and a porous carbon layer is grown in situ on the surface of the submicron-sized silica via a hydrothermal reaction, synthesizing a porous carbon-coated submicron-sized silica anode material. This anode material combines the high capacity of silicon-based active materials with the high conductivity and high stability of carbon-based materials, significantly improving the energy density of the battery. Simultaneously, the porous carbon-coated submicron-sized silica possesses high specific surface area, high porosity, and high conductivity. By growing a porous carbon layer on the surface and constructing a conductive network, the proportion of active silica is increased, effectively suppressing the volume expansion of silica during lithium intercalation, thereby improving the structural stability and cycle stability of the material.

[0006] To address the aforementioned technical problems, a first aspect of the present invention provides a method for preparing a negative electrode material, comprising the following steps:

[0007] (1) After adding biomass-derived silica particles to an acid solution for acid washing, the precipitate is extracted;

[0008] (2) Wash the precipitate extracted in step (1) until neutral, and then extract the precipitate by ball milling;

[0009] (3) Add soluble carbon source, deionized water and anhydrous ethanol to the precipitate extracted in step (2), carry out hydrothermal reaction, and then extract the precipitate;

[0010] (4) The precipitate extracted in step (3) is washed, dried and carbonized to obtain the negative electrode material.

[0011] In some embodiments of the present invention, the biomass-derived silica is selected from at least one of diatomaceous bio-silica and calcined diatomaceous earth; preferably diatomaceous bio-silica.

[0012] In some embodiments of the present invention, the calcined diatomite includes low-temperature calcined diatomite (diatomite sample obtained by air calcination purification at 700°C, which can retain more of the original structure of diatom precursors) and flux-calcined diatomite (diatomite sample obtained by air calcination purification at a temperature above 700°C).

[0013] In some embodiments of the present invention, the soluble carbon source is selected from at least one of glucose, fructose, galactose, sucrose, lactose, maltose, trehalose, cellobiose, starch, pectin, and phenolic resin; preferably glucose.

[0014] In some embodiments of the present invention, in step (1), the acid solution used for pickling is hydrochloric acid, and the concentration of the hydrochloric acid is 0.5-3 mol / L.

[0015] In some embodiments of the present invention, in step (1), the pickling time is 6-24 hours.

[0016] In some embodiments of the present invention, in step (1), after acid washing, the precipitate is extracted by vacuum filtration after standing.

[0017] In some embodiments of the present invention, in step (2), the ball milling is performed at a rotation speed of 300-700 rpm for 9-36 hours. During ball milling, the mass ratio of the precipitate, grinding balls, and milling media is (0.3-3):(0.3-3):1. The grinding balls are preferably zirconia balls, and the milling media are preferably anhydrous ethanol.

[0018] In some embodiments of the present invention, in step (2), after ball milling, the precipitate is extracted by suction filtration after standing for 1-6 hours.

[0019] In some embodiments of the present invention, in step (2), the washing process uses deionized water and the washing time is 10-15 minutes.

[0020] In some embodiments of the present invention, in step (3), the mass ratio of the precipitate, soluble carbon source, deionized water and anhydrous ethanol is 1:(1-2):(10-20):(10-20).

[0021] In some embodiments of the present invention, in step (3), the temperature of the hydrothermal reaction is 120°C-220°C.

[0022] In some embodiments of the present invention, in step (3), the hydrothermal reaction takes 2-12 hours.

[0023] Research has found that ternary control of carbon source concentration, hydrothermal reaction temperature, and reaction time is beneficial for synthesizing carbon-coated silica anode materials with high specific surface area, high mechanical strength, and a thin, dense carbon layer. Excessive carbon coating thickness leads to an excessively high carbon content, reducing both theoretical and actual capacity, hindering lithium-ion diffusion, significantly decreasing the lithium insertion / extraction rate, increasing electrode polarization, and resulting in overall performance degradation, even accelerating capacity decay and reducing cycle stability. Increasing the carbon source concentration and hydrothermal reaction time increases the carbon coating thickness and carbon content; raising the reaction temperature yields a denser carbon layer structure. This invention, through precise control of carbon source concentration, hydrothermal reaction temperature, and hydrothermal reaction time, enables the synthesis of carbon-coated samples with the same carbon content at higher temperatures as those synthesized at lower temperatures, exhibiting higher reversible capacity and cycle stability.

[0024] In some embodiments of the present invention, in step (3), ultrasonic dispersion is performed before the hydrothermal reaction.

[0025] In some embodiments of the present invention, in step (3), after the hydrothermal reaction, the precipitate is extracted by suction filtration after standing for 3-24 hours.

[0026] In some embodiments of the present invention, in step (4), the carbonization is performed by heat treatment at 400-1200°C for 2-8 hours in an inert atmosphere, wherein the inert atmosphere is an argon atmosphere or a nitrogen atmosphere.

[0027] In some embodiments of the present invention, in step (4), deionized water is used for washing, and the washing time is 10-15 minutes.

[0028] In some embodiments of the present invention, in step (4), the drying temperature is 60-120°C.

[0029] A second aspect of the present invention provides a negative electrode material prepared by the above-described method for preparing a negative electrode material. The negative electrode material comprises biomass-derived silica particles and porous carbon. The porous carbon is grown in situ on the surface of the biomass-derived silica particles and coats the biomass-derived silica. The particle size of the biomass-derived silica particles is submicron.

[0030] Specifically, the negative electrode material of the present invention utilizes a porous carbon coating method to construct a conductive network on the surface of biomass-derived silica, thereby enhancing the conductivity of the material, increasing the proportion of active silica, and effectively limiting the volume expansion of silica. These multiple synergistic effects jointly improve the specific capacity and cycle life of the material.

[0031] In some embodiments of the present invention, the specific surface area of ​​the negative electrode material is 40-75 m². 2 / g.

[0032] A third aspect of the present invention provides a negative electrode sheet comprising a negative electrode material prepared by the above-described method for preparing negative electrode material, or comprising the above-described negative electrode material.

[0033] A fourth aspect of the present invention provides a lithium-ion battery comprising the aforementioned negative electrode sheet.

[0034] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages:

[0035] (1) This invention uses biomass-derived silica and reducing sugars as main raw materials to prepare a porous carbon-coated submicron-sized silica anode material. This anode material has a biomass-derived silica core and a reducing porous carbon layer grown in situ on the silica surface, thereby endowing the anode material with high conductivity and high capacity. At the same time, the in-situ grown carbon layer has the characteristics of high mechanical strength and high specific surface area, which can reduce the decomposition of electrolyte on the surface of the anode material and suppress the volume expansion of silica during the charging and discharging process, thereby significantly enhancing the structural stability and cycle performance of the silica-based anode material during the charging and discharging process.

[0036] (2) The anode material of the present invention has abundant raw material sources and low cost, which can greatly reduce raw material costs and effectively reduce environmental impact, thus promoting its commercial application. When the porous carbon-coated submicron-sized silicon dioxide anode material is applied to lithium-ion batteries, it exhibits a reversible capacity >850mAh / g after charge-discharge cycling at a current density of 100mA / g, and a capacity retention rate of more than 90% after 50 cycles. Attached Figure Description

[0037] Figure 1 SEM image of the negative electrode material prepared in Example 3;

[0038] Figure 2 Impedance comparison diagrams of the negative electrode materials prepared in Example 3 and Comparative Example 1;

[0039] Figure 3 The graph shows the cycle performance of lithium-ion coin cells assembled from the negative electrode materials prepared in Example 3 and Comparative Example 1.

[0040] Figure 4 The charge-discharge curves of a lithium-ion coin cell assembled from the negative electrode material prepared in Example 3 are shown.

[0041] Figure 5 The graph shows the rate performance test results of a lithium-ion coin cell assembled from the negative electrode material prepared in Example 1. Detailed Implementation

[0042] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.

[0043] Example 1

[0044] A method for preparing a carbon-coated submicron-sized silicon dioxide anode material includes the following steps:

[0045] 1 kg of low-temperature calcined diatomaceous earth particles were crushed and then immersed in 1 L of 0.5 mol / L HCl for 6 hours. The suspension was collected, and the precipitate was extracted by vacuum filtration and washed with deionized water until neutral. The precipitate was dried and then mixed with zirconia balls and anhydrous ethanol (the mass ratio of precipitate, zirconia balls, and anhydrous ethanol was 1:2:1). The mixture was ball-milled at 350 rpm for 24 hours. After the mixture was allowed to stand for 4 hours, the turbid liquid was collected, and the precipitate was extracted by vacuum filtration. The precipitate was dried, and then a mixed solution of glucose, deionized water, and anhydrous ethanol was added and stirred (the mass ratio of precipitate, glucose, deionized water, and anhydrous ethanol was 1:2:15:15). The mixture was then ultrasonically dispersed, poured into a reaction vessel, and heated to 150°C for 2 hours. After the reaction was completed, the mixture was allowed to stand for 12 hours, and the precipitate was extracted by vacuum filtration and washed with deionized water for 10 minutes. The mixture was then dried at 80°C. The dried product was placed in a tube furnace, argon gas was introduced, and the temperature was raised to 800°C at a rate of 5°C / min. The temperature was held for 2 hours to obtain the carbon-coated submicron-sized silicon dioxide anode material of this experimental example.

[0046] Example 2

[0047] A method for preparing a carbon-coated submicron-sized silicon dioxide anode material includes the following steps:

[0048] 1 kg of low-temperature calcined diatomaceous earth particles were crushed and then immersed in 1 L of 0.5 mol / L HCl for 6 hours. The suspension was collected, and the precipitate was extracted by vacuum filtration and washed with deionized water until neutral. The precipitate was dried and then mixed with zirconia balls and anhydrous ethanol (the mass ratio of precipitate, zirconia balls, and anhydrous ethanol was 1:2:1). The mixture was ball-milled at 350 rpm for 24 hours. After the mixture was allowed to stand for 4 hours, the turbid liquid was collected, and the precipitate was extracted by vacuum filtration. The precipitate was dried, and then a mixed solution of glucose, deionized water, and anhydrous ethanol was added and stirred (the mass ratio of precipitate, glucose, deionized water, and anhydrous ethanol was 1:2:15:15). The mixture was then ultrasonically dispersed, poured into a reaction vessel, and heated to 180°C for 3 hours. After the reaction was completed, the mixture was allowed to stand for 12 hours, and the precipitate was extracted by vacuum filtration and washed with deionized water for 10 minutes. The mixture was then dried at 80°C. The dried product was placed in a tube furnace, argon gas was introduced, and the temperature was raised to 800°C at a rate of 5°C / min. The temperature was held for 2 hours to obtain the carbon-coated submicron-sized silicon dioxide anode material of this experimental example.

[0049] Example 3

[0050] A method for preparing a carbon-coated submicron-sized silicon dioxide anode material includes the following steps:

[0051] 1 kg of low-temperature calcined diatomaceous earth particles were crushed and then immersed in 1 L of 0.5 mol / L HCl for 6 hours. The suspension was collected, and the precipitate was extracted by vacuum filtration and washed with deionized water until neutral. The precipitate was dried and then mixed with zirconia balls and anhydrous ethanol (the mass ratio of precipitate, zirconia balls, and anhydrous ethanol was 1:2:1). The mixture was ball-milled at 350 rpm for 24 hours. After the mixture was allowed to stand for 4 hours, the turbid liquid was collected, and the precipitate was extracted by vacuum filtration. The precipitate was dried, and then a mixed solution of glucose, deionized water, and anhydrous ethanol was added and stirred (the mass ratio of precipitate, glucose, deionized water, and anhydrous ethanol was 1:1:15:15). The mixture was then ultrasonically dispersed, poured into a reaction vessel, and heated to 210°C for 2 hours. After the reaction was completed, the mixture was allowed to stand for 12 hours, and the precipitate was extracted by vacuum filtration and washed with deionized water for 10 minutes. The mixture was then dried at 80°C. The dried product was placed in a tube furnace, argon gas was introduced, and the temperature was raised to 800°C at a rate of 5°C / min. The temperature was held for 2 hours to obtain the carbon-coated submicron-sized silicon dioxide anode material of this experimental example.

[0052] Example 4

[0053] A method for preparing a carbon-coated submicron-sized silicon dioxide anode material includes the following steps:

[0054] 1 kg of low-temperature calcined diatomaceous earth particles were crushed and then immersed in 1 L of 0.5 mol / L HCl for 6 hours. The suspension was collected, and the precipitate was extracted by vacuum filtration and washed with deionized water until neutral. The precipitate was dried and then mixed with zirconia balls and anhydrous ethanol (the mass ratio of precipitate, zirconia balls, and anhydrous ethanol was 1:2:1). The mixture was ball-milled at 350 rpm for 24 hours. After the mixture was allowed to stand for 4 hours, the turbid liquid was collected, and the precipitate was extracted by vacuum filtration. The precipitate was dried, and then a mixed solution of glucose, deionized water, and anhydrous ethanol was added and stirred (the mass ratio of precipitate, glucose, deionized water, and anhydrous ethanol was 1:1:15:15). The mixture was then ultrasonically dispersed, poured into a reaction vessel, and heated to 210°C for 3 hours. After the reaction was completed, the mixture was allowed to stand for 12 hours, and the precipitate was extracted by vacuum filtration and washed with deionized water for 10 minutes. The mixture was then dried at 80°C. The dried product was placed in a tube furnace, argon gas was introduced, and the temperature was raised to 800°C at a rate of 5°C / min. The temperature was held for 2 hours to obtain the carbon-coated submicron-sized silicon dioxide anode material of this experimental example.

[0055] Comparative Example 1

[0056] A method for preparing a silicon dioxide anode material includes the following steps:

[0057] 1 kg of low-temperature calcined diatomaceous earth particles were crushed and then immersed in 1 L of 0.5 mol / L HCl for 6 hours. The suspension was collected, and the precipitate was extracted by vacuum filtration and washed with deionized water until neutral. The precipitate was dried and then mixed with zirconia balls and anhydrous ethanol (the mass ratio of precipitate, zirconia balls, and anhydrous ethanol was 1:2:1). The mixture was ball-milled at 350 rpm for 24 hours. After the mixture was allowed to stand for 4 hours, the turbid liquid was collected, and the precipitate was extracted by vacuum filtration. The precipitate was placed in a tube furnace, and argon gas was introduced. The temperature was raised to 800℃ at a rate of 5℃ / min and held for 2 hours to obtain the silicon dioxide anode material of this comparative example.

[0058] Comparative Example 2

[0059] Referring to the preparation method of carbon-coated submicron-sized silica anode material in Example 1, only the mass ratio of precipitate, glucose, deionized water and anhydrous ethanol was changed to 1:3:15:15, and the reaction vessel was heated to 120°C and kept at that temperature for 6 hours.

[0060] Comparative Example 3

[0061] Referring to the preparation method of carbon-coated submicron-sized silica anode material in Example 1, only the mass ratio of precipitate, glucose, deionized water and anhydrous ethanol was changed to 1:3:15:15, and the reaction vessel was heated to 150°C and kept at that temperature for 6 hours.

[0062] Comparative Example 4

[0063] Referring to the preparation method of carbon-coated submicron-sized silica anode material in Example 1, only the mass ratio of precipitate, glucose, deionized water and anhydrous ethanol was changed to 1:3:15:15, and the reaction vessel was heated to 180°C and kept at that temperature for 6 hours.

[0064] Comparative Example 5

[0065] A method for preparing a carbon-coated silicon dioxide anode material includes the following steps:

[0066] A mixed solution of glucose, deionized water, and anhydrous ethanol was added to silica powder and stirred (the mass ratio of silica powder, glucose, deionized water, and anhydrous ethanol was 1:2:15:15). The mixture was then ultrasonically dispersed, poured into a reaction vessel, and heated to 210°C for 2 hours. After the reaction, the mixture was allowed to stand for 12 hours, and the precipitate was extracted by vacuum filtration. The precipitate was washed with deionized water for 10 minutes and then dried at 80°C. The dried product was placed in a tube furnace, argon gas was introduced, and the temperature was increased to 800°C at a rate of 5°C / min and held for 2 hours to obtain the silicon-carbon anode composite material of this comparative example.

[0067] Comparative Example 6

[0068] A method for preparing a carbon-coated submicron-sized silicon dioxide anode material includes the following steps:

[0069] 1 kg of low-temperature calcined diatomaceous earth particles were crushed and then immersed in 1 L of 0.5 mol / L HCl for 6 hours. The suspension was collected, and the precipitate was extracted by vacuum filtration and washed with deionized water until neutral. The precipitate was dried and then mixed with zirconia balls and anhydrous ethanol (the mass ratio of precipitate, zirconia balls, and anhydrous ethanol was 1:2:1). The mixture was ball-milled at 350 rpm for 24 hours. After the mixture was allowed to stand for 4 hours, the turbid liquid was collected, and the precipitate was extracted by vacuum filtration. The precipitate was dried, and then a mixed solution of carbon nanotubes, deionized water, and anhydrous ethanol (the mass ratio of precipitate, carbon nanotubes, deionized water, and anhydrous ethanol was 1:2:15:15) was added and stirred. The mixture was then ultrasonically dispersed, poured into a reaction vessel, and heated to 210 °C for 2 hours. After the reaction was completed, the mixture was allowed to stand for 12 hours, and the precipitate was extracted by vacuum filtration and washed with deionized water for 10 minutes. The mixture was then dried at 80 °C. The dried product was placed in a tube furnace, argon gas was introduced, and the temperature was raised to 800°C at a rate of 5°C / min. The temperature was held for 2 hours to obtain the carbon-coated submicron-sized silicon dioxide anode material of this experimental example.

[0070] Comparative Example 7

[0071] A method for preparing a carbon-coated submicron-sized silicon dioxide anode material includes the following steps:

[0072] 1 kg of low-temperature calcined diatomaceous earth particles were crushed and then immersed in 1 L of 0.5 mol / L HCl for 6 hours. The suspension was collected, and the precipitate was extracted by vacuum filtration and washed with deionized water until neutral. The precipitate was dried and then mixed with zirconia balls and anhydrous ethanol (the mass ratio of precipitate, zirconia balls, and anhydrous ethanol was 1:2:1). The mixture was ball-milled at 350 rpm for 24 hours. After the mixture was allowed to stand for 4 hours, the turbid liquid was collected, and the precipitate was extracted by vacuum filtration. The precipitate was dried, and then a mixed solution of graphite, deionized water, and anhydrous ethanol (the mass ratio of precipitate, graphite, deionized water, and anhydrous ethanol was 1:2:15:15) was added and stirred. The mixture was then ultrasonically dispersed, poured into a reaction vessel, and heated to 210°C for 2 hours. After the reaction was completed, the mixture was allowed to stand for 12 hours, and the precipitate was extracted by vacuum filtration and washed with deionized water for 10 minutes. The mixture was then dried at 80°C. The dried product was placed in a tube furnace, argon gas was introduced, and the temperature was raised to 800°C at a rate of 5°C / min. The temperature was held for 2 hours to obtain the carbon-coated submicron-sized silicon dioxide anode material of this experimental example.

[0073] Performance testing

[0074] 1. Microstructure

[0075] Figure 1 The image shows the SEM image of the negative electrode material prepared in Example 3. It can be seen that the carbon-coated submicron-sized silicon dioxide negative electrode material prepared in this invention exhibits irregular granular shape with a particle size of approximately 5 μm.

[0076] 2. Material impedance

[0077] The EIS test results of Example 3 and Comparative Example 1 were further performed using an OCTOSTAR200 instrument, as shown below. Figure 2 As shown. By Figure 2 It can be seen that the resistivity of lithium-ion batteries prepared by carbon-coated submicron-sized silicon dioxide anode materials and submicron-sized silicon dioxide anode materials are 483.9Ω and 203.1Ω, respectively, indicating that constructing a conductive network on the silicon dioxide surface by carbon coating can significantly improve the conductivity of the material.

[0078] 3. Electrochemical performance

[0079] The negative electrode materials, carbon black, and polyacrylic acid prepared in Examples 1-4 and Comparative Examples 1-7 were mixed at a mass ratio of 7:2:1 and dispersed in deionized water. The resulting slurry was coated onto copper foil to a thickness of 100 μm to obtain the negative electrode sheet; then, the negative electrode sheet was dried in a vacuum oven at 80 °C for 12 hours. The negative electrode sheet was cut into discs with a diameter of 10 mm for battery assembly. The active material loading was 1-1.2 mg. The electrolyte was 1 mol / L LiPF6, EC / EMC / DC (volume ratio 1:1:1). Lithium foil was used as the counter electrode and reference electrode, and Celgard 2400 was used as the separator. Finally, the assembly of the CR2032 coin cell was completed in a glove box filled with Ar.

[0080] Test conditions: The coin cells prepared in Examples 1-4 and Comparative Examples 1-7 were tested in a voltage range of 0.01-3V (relative to Li / Li). + First, activation was performed using three charge-discharge cycles at a current density of 50 mA / g, followed by cycle testing at a current density of 100 mA / g. The results are shown in Table 1 and 2. Figure 3-4 As shown.

[0081] Table 1:

[0082]

[0083] As shown in Table 1, the lithium-ion batteries prepared from the carbon-coated submicron-sized silica anode materials obtained in Examples 1-4 of this invention exhibit better initial discharge specific capacity, discharge specific capacity after 50 cycles, and capacity retention after 50 cycles compared to Comparative Examples 1-7. The main reason for this is that Examples 1-4 used specific biomass-derived silica and reducing sugars as the main raw materials, and implemented ternary control over the carbon source concentration, hydrothermal reaction temperature, and reaction time, resulting in porous carbon-coated submicron-sized silica anode materials with high specific surface area, high porosity, and high conductivity.

[0084] Figure 3 The graph shows the cycle performance of lithium-ion coin cells assembled from the negative electrode materials prepared in Example 3 and Comparative Example 1 (the horizontal axis represents the number of cycles, and the vertical axis represents the discharge capacity). The graph shows that the coin cells prepared in Example 2 and Comparative Example 2 have discharge capacities of 821.71 mAh / g and 130.47 mA h / g, respectively, after 50 cycles, and capacity retention rates of 91.75% and 70.90%, respectively.

[0085] Figure 4The graph shows the charge-discharge curves (horizontal axis: Capacity, vertical axis: Potential) of a lithium-ion coin cell assembled from the negative electrode material prepared in Example 3. The curves indicate that the initial charge-discharge specific capacity is 1397.34 mAh / g, and the subsequent reversible capacity is greater than 800 mAh / g. The irreversible capacity loss in the first cycle is due to the formation of a solid electrolyte film on the electrode material surface, and the reaction between silicon dioxide and Li. + This is caused by the formation of irreversible lithium oxide and lithium silicate salts through a lithiation reduction reaction.

[0086] Figure 5 The graph shows the rate performance test results of a lithium-ion coin cell assembled from the negative electrode material prepared in Example 1. Figure 5 It can be seen that when the current density is 0.1 A / g, 0.2 A / g, 0.5 A / g, 1 A / g, and 2 A / g, the reversible capacity of C@SiO2 prepared in Example 1 is approximately 662.37 mAh / g, 574.53 mAh / g, 468.65 mAh / g, 377.20 mAh / g, and 275.73 mAh / g, respectively. When the current is restored to 0.1 A / g, the capacity of C@SiO2 is higher than the initial capacity at 0.1 A / g, and no significant capacity decay is observed.

[0087] For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.

Claims

1. A method for preparing a negative electrode material, characterized in that, Includes the following steps: (1) After adding biomass-derived silica particles to an acid solution for acid washing, the precipitate is extracted; (2) Wash the precipitate extracted in step (1) until neutral, and then extract the precipitate by ball milling; (3) Add soluble carbon source, deionized water and anhydrous ethanol to the precipitate extracted in step (2), carry out hydrothermal reaction, and then extract the precipitate; (4) The precipitate extracted in step (3) is washed, dried and carbonized to obtain the negative electrode material.

2. The method for preparing the negative electrode material according to claim 1, characterized in that, The biomass-derived silica is selected from at least one of diatomaceous bio-silica and calcined diatomaceous earth. And / or, the soluble carbon source is selected from at least one of glucose, fructose, galactose, sucrose, lactose, maltose, trehalose, cellobiose, starch, pectin, and phenolic resin.

3. The method for preparing the negative electrode material according to claim 1, characterized in that, In step (1), the acid solution used for pickling is hydrochloric acid, and the concentration of the hydrochloric acid is 0.5-3 mol / L.

4. The method for preparing the negative electrode material according to claim 1, characterized in that, In step (2), the ball milling is performed at a speed of 300-700 rpm for 9-36 hours.

5. The method for preparing the negative electrode material according to claim 1, characterized in that, In step (3), the mass ratio of the precipitate, soluble carbon source, deionized water and anhydrous ethanol is 1:(1-2):(10-20):(10-20); and / or, the temperature of the hydrothermal reaction is 120℃-210℃; and / or, the time of the hydrothermal reaction is 2-12 hours.

6. The method for preparing the negative electrode material according to claim 1, characterized in that, In step (4), the carbonization is performed by heat treatment at 400-1200℃ for 2-8 hours in an inert atmosphere.

7. A negative electrode material, characterized in that, The negative electrode material is prepared by the method of any one of claims 1-6, wherein the negative electrode material comprises biomass-derived silica particles and porous carbon; the porous carbon is grown in situ on the surface of the biomass-derived silica particles and coats the biomass-derived silica; the particle size of the biomass-derived silica particles is submicron.

8. The negative electrode material according to claim 7, characterized in that, The specific surface area of ​​the negative electrode material is 250-400 m². 2 / g.

9. A negative electrode sheet, characterized in that, The negative electrode material includes the negative electrode material prepared by the method of any one of claims 1-6, or the negative electrode material according to claim 7 or 8.

10. A lithium-ion battery, characterized in that, Includes the negative electrode sheet as described in claim 9.

Images