A silicon-carbon composite material for battery anode and its preparation method

Abstract

This invention discloses a silicon-carbon composite material for battery anodes and its preparation method, relating to the field of silicon-carbon composite materials. The silicon-carbon composite material for battery anodes comprises the following components in parts by weight: 15-40 parts silicon source, 20-60 parts organic acid, 5-15 parts phosphorus source, and 10-30 parts carbon source, wherein the silicon source is metallic silicon micropowder. This invention effectively combines the high specific capacity of silicon with the good conductivity and structural stability of carbon. The introduction of phosphorus doping further optimizes the conductive network of the material and stabilizes its interface structure, providing an effective buffer space for the significant volume expansion of silicon during charging and discharging. The raw materials used, such as metallic silicon micropowder, citric acid, and bamboo charcoal powder, are all widely available and inexpensive chemical or biomass raw materials, enabling phosphorus doping and ultimately obtaining a silicon-carbon composite material with a uniform structure and controllable component distribution.

Description

Technical Field

[0001] This invention relates to the field of silicon-carbon composite materials, and in particular to a silicon-carbon composite material for battery negative electrodes and its preparation method. Background Technology

[0002] With the increasing demand for high-energy-density energy storage from electric vehicles, portable electronic devices, and other applications, the development of next-generation high-performance lithium-ion and sodium-ion batteries has become a research hotspot. Currently, commercial lithium-ion battery anodes mainly use graphite materials, but their theoretical specific capacity is relatively low (approximately 372 mAh / g), which has gradually become a bottleneck for improving battery energy density.

[0003] Silicon is considered one of the most promising next-generation anode materials due to its extremely high theoretical specific capacity, suitable lithium insertion / extraction potential, and abundant reserves. However, silicon undergoes significant volume changes during charging and discharging, which leads to the breakage and pulverization of active material particles and loss of electrical contact with the current collector. Simultaneously, these drastic volume fluctuations cause continuous rupture and regeneration of the solid electrolyte interface film on the electrode surface, continuously consuming electrolyte and active lithium / sodium ions. This ultimately results in rapid capacity decay and a sharp decline in cycle life. Furthermore, silicon's inherently poor conductivity also limits its rate performance.

[0004] To overcome the aforementioned shortcomings, constructing silicon-carbon composite materials is one of the most promising directions in existing technologies. Carbon materials have good electrical conductivity and certain mechanical flexibility. When combined with silicon, they can effectively buffer volume expansion and improve electrical conductivity. However, many existing silicon-carbon composite material preparation technologies are often complex, expensive, and energy-intensive, and the carbon sources used are costly, which is not conducive to large-scale commercial applications. At the same time, how to achieve uniform composite of silicon, carbon, and other functional components through simpler and more economical processes to synergistically improve the electrochemical performance of materials remains a technical problem that needs to be solved. Summary of the Invention

[0005] The main objective of this invention is to provide a silicon-carbon composite material for battery anodes and a method for preparing the same, which can effectively solve the technical problems raised in the background art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A silicon-carbon composite material for battery negative electrode comprises the following components in parts by weight: 15-40 parts silicon source, 20-60 parts organic acid, 5-15 parts phosphorus source, and 10-30 parts carbon source.

[0008] Preferably, the silicon source is metallic silicon powder, including elemental silicon powder.

[0009] Preferably, the organic acid is citric acid, and the polycarboxylic acid is citric acid.

[0010] Preferably, the phosphorus source is ammonium dihydrogen phosphate or phosphoric acid.

[0011] Preferably, the carbon source is bamboo charcoal powder or activated carbon powder.

[0012] A method for preparing a silicon-carbon composite material for a battery negative electrode, the method specifically includes the following steps:

[0013] Step 1, Mixing: Add 15-40 parts by weight of silicon source and 20-60 parts by weight of organic acid to deionized water and stir to mix;

[0014] Step 2, pH adjustment: Add ammonia water dropwise to the mixture obtained in Step 1 to adjust the pH value of the mixture to 8.0~8.5;

[0015] Step 3, Phosphorus-carbon compounding: Add 5-15 parts by weight of phosphorus source and 10-30 parts by weight of carbon source to the mixture obtained in Step 2, and stir until homogeneous;

[0016] Step 4, gelation: The mixture obtained in step 3 is heated to evaporate the water and form a wet gel;

[0017] Step 5, Drying: Dry the wet gel obtained in Step 4 at 100~120℃ to constant weight to obtain dry gel;

[0018] Step 6, Calcination: Under an inert atmosphere, the dry gel obtained in Step 5 is calcined at 700~900℃, and after cooling, the silicon-carbon composite material is obtained.

[0019] Preferably, in step one, the stirring speed is 300-500 rpm and the mixing time is 1-3 hours.

[0020] Preferably, in step four, the temperature for heating and gelation is 60~90℃.

[0021] Preferably, in step six, the heating rate of the calcination treatment is 2~5℃ / minute, and the temperature is maintained for 2~4 hours after reaching the set temperature.

[0022] Preferably, in step six, the inert atmosphere is a nitrogen or argon atmosphere.

[0023] The beneficial effects that can be achieved by the above embodiments of the present invention include: by combining silicon source and carbon source, the high specific capacity of silicon material and the good conductivity and structural stability of carbon material are effectively combined. At the same time, the introduction of phosphorus element for doping can further optimize the conductive network of the material and stabilize its interface structure, significantly improving the specific capacity, first coulombic efficiency and long cycle stability of composite material, making it more suitable for the negative electrode of high performance lithium-ion battery or sodium-ion battery.

[0024] The sol-gel method and carbon coating strategy adopted can make silicon particles uniformly dispersed and embedded in a three-dimensional porous carbon matrix formed by organic acid cracking carbon and added carbon source. This can provide an effective buffer space for the huge volume expansion of silicon during charging and discharging, inhibit the pulverization and shedding of active material, and thus greatly improve the structural integrity and cycle life of the electrode.

[0025] With the sol-gel process as the core, the process steps are simple, the equipment requirements are conventional, and there is no need for complex and expensive processes such as vapor deposition. The raw materials used, such as silicon metal powder, citric acid, and bamboo charcoal powder, are all widely available and inexpensive chemical or biomass raw materials. In particular, the use of biomass carbon sources such as bamboo charcoal powder is in line with the concept of green and low-cost manufacturing, and has good economic benefits and potential for large-scale production.

[0026] Through an organic acid-assisted sol-gel process, the initial uniform mixing of silicon, phosphorus, and carbon components at the molecular / nanoscale was achieved. The subsequent calcination process carbonized the organic acids to form a conductive carbon network, while simultaneously achieving phosphorus doping. Ultimately, a silicon-carbon composite material with a uniform structure and controllable component distribution was obtained, which is crucial for obtaining products with consistent and reliable performance. Attached Figure Description

[0027] Figure 1 This is a flowchart of a method for preparing a silicon-carbon composite material for a battery negative electrode according to the present invention. Detailed Implementation

[0028] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0029] A silicon-carbon composite material for battery negative electrode comprises the following components in parts by weight: 15-40 parts silicon source, 20-60 parts organic acid, 5-15 parts phosphorus source, and 10-30 parts carbon source.

[0030] like Figure 1 As shown, a method for preparing a silicon-carbon composite material for a battery negative electrode includes the following steps: 15-40 parts of silicon source, 20-60 parts of organic acid, 5-15 parts of phosphorus source, and 10-30 parts of carbon source.

[0031] In this embodiment, the silicon source is metallic silicon powder, which includes elemental silicon powder.

[0032] In this embodiment, the organic acid is citric acid, and the polycarboxylic acid is citric acid.

[0033] In this embodiment, the phosphorus source is ammonium dihydrogen phosphate or phosphoric acid.

[0034] In this embodiment, the carbon source is bamboo charcoal powder or activated carbon powder.

[0035] A method for preparing a silicon-carbon composite material for a battery negative electrode, the method specifically includes the following steps:

[0036] Step 1, Mixing: Add 15-40 parts by weight of silicon source and 20-60 parts by weight of organic acid to deionized water and stir to mix;

[0037] Step 2, pH adjustment: Add ammonia water dropwise to the mixture obtained in Step 1 to adjust the pH value of the mixture to 8.0~8.5;

[0038] Step 3, Phosphorus-carbon compounding: Add 5-15 parts by weight of phosphorus source and 10-30 parts by weight of carbon source to the mixture obtained in Step 2, and stir until homogeneous;

[0039] Step 4, gelation: The mixture obtained in step 3 is heated to evaporate the water and form a wet gel;

[0040] Step 5, Drying: Dry the wet gel obtained in Step 4 at 100~120℃ to constant weight to obtain dry gel;

[0041] Step 6, Calcination: Under an inert atmosphere, the dry gel obtained in Step 5 is calcined at 700~900℃, and after cooling, the silicon-carbon composite material is obtained.

[0042] In this embodiment, in step one, the stirring speed is 300-500 rpm and the mixing time is 1-3 hours.

[0043] In this embodiment, the temperature for heating and gelation in step four is 60~90℃.

[0044] In this embodiment, in step six, the heating rate of the calcination treatment is 2~5℃ / minute, and the temperature is maintained for 2~4 hours after reaching the set temperature.

[0045] In this embodiment, in step six, the inert atmosphere is a nitrogen or argon atmosphere.

[0046] In the embodiments provided by this invention, it should be understood that the disclosed devices, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and other division methods may exist in actual implementation. Modules described as separate components may or may not be physically separated, and components shown as modules may or may not be physical units, i.e., they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of the method in this embodiment according to actual needs.

[0047] The above embodiments are only used to illustrate the technical methods of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical methods of the present invention without departing from the spirit and scope of the technical methods of the present invention.

Claims

1. A silicon-carbon composite material for a battery negative electrode, characterized in that: It includes the following components in parts by weight: 15-40 parts silicon source, 20-60 parts organic acid, 5-15 parts phosphorus source, and 10-30 parts carbon source.

2. The silicon-carbon composite material for a battery negative electrode according to claim 1, characterized in that: The silicon source is metallic silicon powder, which includes elemental silicon powder.

3. The silicon-carbon composite material for a battery negative electrode according to claim 1, characterized in that: The organic acid is citric acid, and the polycarboxylic acid is citric acid.

4. The silicon-carbon composite material for a battery negative electrode according to claim 1, characterized in that: The phosphorus source is ammonium dihydrogen phosphate or phosphoric acid.

5. The method for preparing a silicon-carbon composite material for a battery negative electrode according to claim 1, characterized in that: The carbon source is bamboo charcoal powder or activated carbon powder.

6. A method for preparing a silicon-carbon composite material for a battery negative electrode according to any one of claims 1-5, characterized in that, The method specifically includes the following steps: Step 1, Mixing: Add 15-40 parts by weight of silicon source and 20-60 parts by weight of organic acid to deionized water and stir to mix; Step 2, pH adjustment: Add ammonia water dropwise to the mixture obtained in Step 1 to adjust the pH value of the mixture to 8.0~8.5; Step 3, Phosphorus-carbon compounding: Add 5-15 parts by weight of phosphorus source and 10-30 parts by weight of carbon source to the mixture obtained in Step 2, and stir until homogeneous; Step 4, gelation: The mixture obtained in step 3 is heated to evaporate the water and form a wet gel; Step 5, Drying: Dry the wet gel obtained in Step 4 at 100~120℃ to constant weight to obtain dry gel; Step 6, Calcination: Under an inert atmosphere, the dry gel obtained in Step 5 is calcined at 700~900℃, and after cooling, the silicon-carbon composite material is obtained.

7. A method for preparing a silicon-carbon composite material for a battery negative electrode according to claim 6, characterized in that: In step one, the stirring speed is 300-500 rpm, and the mixing time is 1-3 hours.

8. A method for preparing a silicon-carbon composite material for a battery negative electrode according to claim 6, characterized in that: In step four, the temperature for heating and gelation is 60~90℃.

9. A method for preparing a silicon-carbon composite material for a battery negative electrode according to claim 6, characterized in that: In step six, the heating rate of the calcination treatment is 2~5℃ / minute, and the temperature is maintained for 2~4 hours after reaching the set temperature.

10. A method for preparing a silicon-carbon composite material for a battery negative electrode according to claim 6, characterized in that: In step six, the inert atmosphere is either nitrogen or argon.

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