Preparation method of mixed biomass carbon coated silicon-based negative electrode material

Abstract

The invention provides a preparation method of a mixed biomass carbon coated silicon-based negative electrode material. Biomass carbon is mainly derived from prolamin, glutenin and high-activity yeast. Under the catalysis of high-activity yeast, prolamin and glutenin meet water to form a net-shaped structure, and the flexibility of the carbonized porous negative electrode material can be adjusted through different addition proportions, so that the flexible porous nitrogen-doped carbon-coated silicon-based negative electrode material can be obtained, the problem of volume expansion in the electrochemical process of a silicon negative electrode is relieved, and meanwhile, the conductivity is improved; the excellent electrochemical performance is shown. The porous silicon-based negative electrode material with controllable flexibility is obtained through drying and high-temperature annealing, the method is simple, effective and low in cost, and the prepared composite silicon-based negative electrode material is excellent in performance and suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to a method for preparing a silicon-based anode material coated with mixed biomass carbon, belonging to the field of lithium-ion battery technology. Background Technology

[0002] In recent years, with the booming development of electric vehicles and 3C electronic products, the demand for high-energy-density, high-rate batteries has been increasing year by year. How to improve the energy density, rate performance, and safety of battery materials has become an urgent problem to be solved. The graphite material used in commercial anodes has a theoretical capacity of 372 mAh / g, which is insufficient to meet the needs of high-energy-density lithium-ion batteries. Silicon anodes have attracted much attention due to their excellent theoretical capacity (4200 mAh / g) and low cost. When silicon participates in the reaction as a lithium-ion battery anode, its energy storage mechanism is an alloying reaction. During cycling, the volume expansion rate reaches nearly 300%, and the resulting internal stress will cause the material structure to collapse and shatter, accelerating the formation of the solid electrolyte interphase (SEI) film, ultimately leading to reduced battery capacity, poor cycle performance, and low first-time efficiency. The volume expansion problem of silicon anodes has become a huge obstacle restricting their commercial application in the field of lithium-ion batteries. By combining silicon with carbon materials that have excellent structural stability and ductility, the volume expansion of silicon during charging and discharging can be controlled and reduced. At the same time, the high conductivity of carbon materials can further improve the electrochemical performance of the composite material.

[0003] Common carbon materials can be divided into two categories: one is conductive materials such as carbon nanotubes and reduced graphene oxide, and the other is organic carbon materials (sugars, asphalt, polymers, etc.), which require high-temperature pyrolysis to form coating materials. Some nitrogen-containing polymers are often used for pyrolysis to generate nitrogen-containing carbon sources. Numerous experimental and theoretical studies have demonstrated that nitrogen-doped amorphous carbon has higher electrical conductivity and ion mobility than pristine carbon materials. The nitrogen doped in the carbon source not only acts as an electron donor but also provides electron carriers, enhancing electron conduction between the carbon layer and adjacent silicon particles. However, commonly used nitrogen sources are expensive and even toxic, hindering environmental protection and large-scale production. Natural biomass nitrogen-containing carbon sources have become an important research direction. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for preparing a silicon-carbon anode material coated with mixed biomass carbon.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A silicon-based anode material coated with mixed biomass carbon, characterized in that: the material is prepared by the following method, the steps of which are as follows: (1) Grind the prolamin, glutenin and highly active yeast in a mass ratio of 1:x:(1+x) / 2 to obtain mixed powder I; (2) Add silicon anode powder to mixed powder I, grind it further, add an appropriate amount of deionized water, and ultrasonically disperse to obtain a uniform mixed solution; (3) The obtained homogeneous mixed solution is dried to obtain the precursor material; (4) The obtained precursor material is subjected to high-temperature annealing to obtain a silicon-based anode material coated with mixed biomass carbon.

[0006] Preferably, in step (1), x in 1:x:(1+x) / 2 is 0.5~2.

[0007] Preferably, in step (2), the amount of silicon anode added is determined by the silicon-to-carbon mass ratio, which is 0.2 to 10.

[0008] Preferably, in step (3), the drying method is freeze drying or spray drying until the material is in powder form.

[0009] Preferably, in step (4), the high-temperature annealing device is a tube furnace, and argon gas is introduced during the annealing process with a flow rate of 50cfm ~ 300cfm.

[0010] Preferably, in step (4), the high-temperature annealing temperature is 600℃~800℃ and the annealing time is 0.5h~5h.

[0011] A lithium-ion battery, wherein the negative electrode material of the battery is a silicon-based negative electrode material coated with mixed biomass carbon as described in this invention. Beneficial effects

[0012] This invention provides a method for preparing silicon-based anode materials coated with mixed biomass carbon, wherein the biomass carbon is mainly derived from prolysin, glutenin, and highly active yeast. Under the catalysis of highly active yeast, prolysin and glutenin form a network structure upon contact with water. By adjusting the addition ratio, the flexibility of the porous anode material after carbonization can be controlled, thereby obtaining a flexible, porous nitrogen-doped carbon-coated silicon-based anode material. This alleviates the volume expansion problem during the electrochemical process of silicon anodes, while simultaneously improving conductivity and exhibiting excellent electrochemical performance.

[0013] This invention provides a method for preparing silicon-based anode materials coated with mixed biomass carbon. The method obtains a porous silicon-based anode material with controllable flexibility through drying and high-temperature annealing. The method is simple, effective, and low-cost. The prepared composite silicon-based anode material has excellent performance and is suitable for large-scale production. Attached Figure Description

[0014] Figure 1The energy dispersive spectroscopy (EDS) spectra of the negative electrode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 are shown.

[0015] Figure 2 Cycling data of batteries assembled with the negative electrode materials prepared in Example 1, Comparative Example 1 and Comparative Example 2 at a current density of 0.1C (the first three cycles are activated at a current density of 0.05C).

[0016] Figure 3 The image shows the cycling data of batteries assembled with the negative electrode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 at a current density of 0.4C (the first three cycles were activated at a current density of 0.05C). Detailed Implementation

[0017] To better clarify and understand the objectives, process solutions, and advantages of this invention, the technical solutions and implementation methods of this invention will be further described clearly, completely, and in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the embodiments described in this invention are implemented under the premise of the technical solutions of this invention, providing detailed implementation methods and specific operating procedures, but are only some embodiments of this invention, not all embodiments. The specific implementation methods described are limited to illustrating and explaining this invention and do not limit this invention. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0018] Unless otherwise specified, the experimental methods and conditions used in the embodiments of this invention are conventional methods and conditions. The materials, reagents, and instruments used in the embodiments, unless otherwise specified, can be obtained commercially or prepared by conventional methods. The reaction conditions described in the invention can all achieve the reactions and obtain the desired products. Due to space limitations, some embodiments are listed below to further illustrate the advantages of the technical solution of this invention.

[0019] In the following embodiments or comparative examples: Assembly of button cells: At room temperature, the working electrode is first prepared by mixing the materials prepared in the examples or comparative examples with binders and conductive agents in a ratio of 8:1:1 to prepare a uniform slurry; then, the slurry is uniformly coated onto copper foil with a scraper and dried under vacuum at 100°C for 12 hours to obtain the working electrode; finally, the copper foil coated with the sample is pressed into small discs with a diameter of 1.1 cm using a punching machine as the negative electrode, lithium foil as the positive electrode material, and 1.0 M LiPF6 carbonate electrolyte to prepare a button half cell.

[0020] The Blue Electric system is used to detect electrochemical performance, with a test voltage range of 0.01 V-1.50 V, a test temperature of 30℃, and test current densities of 0.1C and 0.4C (1C=2000 mA / g). Example

[0021] Gliadin, glutenin, and highly active yeast were weighed out in a mass ratio of 1:1:1 and mixed evenly. Then, 500 nm submicron silicon was weighed out in a silicon source:carbon source ratio of 4:6, and the mixture was further ground and mixed. An appropriate amount of deionized water was added, and the mixture was ultrasonically pulverized for 30 minutes. Then, it was stirred on a magnetic stirrer at 30 °C for 24 h. The mixed solution was frozen with liquid nitrogen and then transferred to a vacuum freeze dryer and dried for 24 h to obtain the precursor material. The precursor material was placed in an argon tube furnace and heated to 800 °C at a rate of 5 °C / min, held at that temperature for 2 h, and then cooled to room temperature at the same rate to obtain the silicon-based anode material coated with mixed biomass carbon as described in Example 1.

[0022] The energy spectrum of the silicon-based anode material coated with mixed biomass carbon in Example 1 is shown below. Figure 1 As shown, the results indicate that Si, C, and N elements are uniformly distributed on the surface of the negative electrode material.

[0023] The cycle performance of the assembled battery is as follows: Figure 2 and Figure 3 As shown in the figure, the capacity retention rate of Example 1 was 60.9% after 100 cycles at 0.1C and 52.1% after 200 cycles at 0.4C.

[0024] Submicron silicon (500 nm) and highly active dry yeast were weighed at a mass ratio of 4:6, mixed evenly, and then deionized water was added. The mixture was ultrasonically homogenized for 30 minutes, and then stirred on a magnetic stirrer at 30 °C for 24 h. After freezing with liquid nitrogen, the mixture was placed in a vacuum freeze dryer and dried for 24 h to obtain the precursor material. The precursor material was then placed in an argon tube furnace and sintered at 800 °C for 2 h to obtain the anode material of Comparative Example 1.

[0025] The energy spectrum of the negative electrode material obtained in Comparative Example 1 is as follows: Figure 1 As shown, the results indicate that the distribution of the N element is sparser than that in Example 1.

[0026] The cycle performance of the assembled battery is as follows: Figure 2 and Figure 3 As shown in the figure, the capacity retention rate of Comparative Example 1 is 54.0% after 100 cycles at 0.1C and 49.8% after 200 cycles at 0.4C.

[0027] Submicron silicon (500 nm) and maltodextrin were weighed at a mass ratio of 4:6, mixed uniformly, and then deionized water was added. The mixture was then subjected to high-speed shearing and stirring in an ultrasonic machine for 4 hours. The mixture was then frozen with liquid nitrogen and placed in a vacuum freeze dryer for 24 hours to obtain the precursor material. The precursor was then placed in an argon tube furnace and sintered at 800 °C for 2 hours to obtain the anode material of Comparative Example 2.

[0028] The energy spectrum of the negative electrode material obtained in Comparative Example 2 is as follows: Figure 1 As shown, the results indicate that the N element has the sparsest distribution.

[0029] The cycle performance of the assembled battery is as follows: Figure 2 and Figure 3 As shown in the figure, the capacity retention rate of Comparative Example 2 is 34.3% after 100 cycles at 0.1C and 40.7% after 200 cycles at 0.4C.

Claims

1. A silicon-based anode material coated with mixed biomass carbon, characterized in that: The material is prepared by the following method, the steps of which are as follows: (1) Grind the prolamin, glutenin and highly active yeast in a mass ratio of 1:x:(1+x) / 2 to obtain mixed powder I; (2) Add silicon anode powder to mixed powder I, grind it further, add an appropriate amount of deionized water, and ultrasonically disperse to obtain a uniform mixed solution; (3) The obtained homogeneous mixed solution is dried to obtain the precursor material; (4) The obtained precursor material is subjected to high-temperature annealing to obtain a silicon-based anode material coated with mixed biomass carbon.

2. The silicon-based anode material coated with mixed biomass carbon as described in claim 1, characterized in that: In step (1), x in 1:x:(1+x) / 2 is 0.5~2.

3. The silicon-based anode material coated with mixed biomass carbon as described in claim 1, characterized in that: In step (2), the amount of silicon anode added is determined by the silicon-to-carbon mass ratio, which is 0.2 to 10.

4. The silicon-based anode material coated with mixed biomass carbon as described in claim 1, characterized in that: In step (3), the drying method is freeze drying or spray drying until the material is in powder form.

5. The silicon-based anode material coated with mixed biomass carbon as described in claim 1, characterized in that: In step (4), the high-temperature annealing device is a tube furnace, and argon gas is introduced during the annealing process with a flow rate of 50cfm ~ 300cfm.

6. The silicon-based anode material coated with mixed biomass carbon as described in claim 1, characterized in that: In step (4), the high-temperature annealing temperature is 600℃~800℃ and the annealing time is 0.5h~5h.

7. A lithium-ion battery, characterized in that: The negative electrode material of the battery is a silicon-based negative electrode material coated with mixed biomass carbon as described in any one of claims 1 to 6.

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