Selenium-doped modified silicon-carbon negative electrode material, and preparation method and application thereof

Abstract

This invention discloses a selenium-doped modified silicon-carbon anode material, comprising a silane-deposited silicon-carbon material and selenium doped therein. The silane-deposited silicon-carbon material is composed of porous carbon and nano-silicon, with the porous carbon serving as the silicon host and the nano-silicon acting as the active material and uniformly distributed within the porous carbon. Selenium is uniformly doped into the silicon-carbon matrix, forming a selenium-doped modified silicon-carbon composite structure. This invention also discloses the preparation method and application of this material. This invention achieves uniform selenium doping through solid-state grinding, vacuum sealing, and high-temperature heat treatment, utilizing the porous carbon framework to suppress the selenium shuttle effect and volume expansion. During the first discharge, selenium generates Li₂Se in situ, suppressing irreversible Li₂O formation, thinning the SEI film, reducing interfacial impedance, and improving the first coulombic efficiency and active material utilization rate of the silicon-carbon anode.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion secondary battery materials, specifically relating to selenium-doped modified silicon-carbon anode materials, and also to the preparation method and application of such anode materials. Background Technology

[0002] Lithium-ion batteries, due to their high energy density, long cycle life, and lack of memory effect, have been widely used in portable electronic devices, electric vehicles, and large-scale energy storage. To meet the ever-increasing demand for high energy density, the development of novel high-performance electrode materials has become a research hotspot. Silicon-based materials, with their ultra-high theoretical specific capacity (approximately 4200 mAh / g), low lithium intercalation potential, and abundant resources, are considered one of the most promising anode materials for next-generation high-energy-density lithium-ion batteries. However, silicon-based anode materials face two major challenges in practical applications: first, the enormous volume expansion (over 300%) during lithiation / delithiation processes leads to the pulverization of active materials, electrode structure collapse, and continuous rupture and regeneration of the solid electrolyte interface film, resulting in rapid capacity decay; second, the inherently low electronic conductivity of silicon limits its rate performance. Currently, nanostructuring silicon and combining it with carbon materials is an effective strategy to alleviate volume expansion, but further optimization is still needed.

[0003] To address the aforementioned issues, introducing a silicon / carbon composite structure with silane deposition is an effective way to improve the conductivity and structural stability of the material. However, the interfacial stability and volume buffering capacity of conventional silicon / carbon anodes during long-term cycling still need improvement. In recent years, selenium (Se) has attracted widespread attention as an electrode material due to its high theoretical specific capacity and excellent electronic conductivity. During the initial discharge process, selenium-containing materials react with lithium in situ to generate Li₂Se with high ionic conductivity. This reaction can effectively compete for electrons, thereby suppressing the formation of irreversible Li₂O, reducing the thickness of the solid electrolyte interfacial film, lowering the interfacial impedance, and improving the initial coulombic efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a selenium-doped modified silicon-carbon anode material, which solves the problems of high interfacial impedance and low initial coulombic efficiency of existing silicon-carbon anode materials in lithium-ion batteries.

[0005] Another object of the present invention is to provide a composite material prepared by a method for preparing selenium-doped modified silicon-carbon anode materials.

[0006] A third objective of this invention is to provide the application of selenium-doped modified silicon-carbon anode materials in lithium-ion batteries.

[0007] The technical solution adopted in this invention is a selenium-doped modified silicon-carbon anode material, comprising a silane-deposited silicon-carbon material and selenium doped therein. The silane-deposited silicon-carbon material is composed of porous carbon and nano-silicon. The porous carbon serves as the silicon host, and the nano-silicon serves as the active material and is uniformly distributed inside the porous carbon. The selenium element is uniformly doped in the silicon-carbon material matrix, forming a selenium-doped modified silicon-carbon composite structure.

[0008] Another technical solution adopted in this invention is a method for preparing selenium-doped modified silicon-carbon anode materials, which is specifically implemented according to the following steps: Step 1: In a glove box under an argon atmosphere, weigh the silicon carbide material deposited by silane and selenium powder according to the proportion, put them into an agate mortar and grind them together to obtain a mixed powder. Step 2: Place the ground mixed powder into a sealed container and use a tube sealing machine to vacuum and seal it; Step 3: Place the sealed quartz tube into a muffle furnace and heat it using a programmed heating method. Hold it at that temperature for a certain period of time, then cool it down to room temperature before removing it. Step 4: Disassemble the sealed quartz tube in an argon atmosphere glove box, then clean it in a fume hood, and finally dry, sieve and collect the product.

[0009] Another feature of the technical solution of the present invention is that, In step 1, the mass ratio of the silicon-carbon material deposited by silane to the selenium powder is (6-125):1, and the grinding time is 15-30 min.

[0010] In step 2, the sealed container is a quartz tube, and a tube sealing machine is used for vacuum sealing.

[0011] In step 3, the heat treatment is carried out in a muffle furnace at a heating rate of 1-5 °C / min, heated to 350-500 °C, and held for 10-15 h.

[0012] In step 3, after heat treatment, the temperature is reduced to room temperature at a rate of 1-3 °C / min.

[0013] The cleaning process in step 4 includes: repeated rinsing and filtration with alcohol and deionized water; drying is done by vacuum drying at a temperature of 60-80 ℃ for 12-24 h.

[0014] The third technical solution adopted in this invention is the application of selenium-doped modified silicon-carbon anode material in lithium-ion batteries.

[0015] The beneficial effects of this invention are: The selenium-doped modified silicon-carbon anode material of this invention is modified by solid-phase selenization of silane-deposited silicon-carbon material with selenium powder. Utilizing the physical confinement effect and high conductivity of the porous carbon matrix on selenium, the shuttle effect and volume expansion of selenium are suppressed, reducing charge transfer resistance. More importantly, during the first discharge, selenium in the material preferentially reacts with lithium to form Li₂Se with high ionic conductivity in situ. This reaction effectively suppresses the formation of irreversible Li₂O, thereby significantly thinning the solid electrolyte interface film, reducing interfacial transport impedance, minimizing irreversible capacity loss, and improving the first-discharge coulombic efficiency. Furthermore, the method of this invention provides a novel selenium-doped modified silicon-carbon anode material for lithium-ion batteries with low impedance and high first-discharge efficiency. Attached Figure Description

[0016] Figure 1 This is a transmission electron microscope (TEM) image of the selenium-doped modified silicon-carbon anode material prepared in Example 2 of this invention; Figure 2 This is the EDS energy spectrum of undoped selenium silicon-carbon material; Figure 3 This is the EDS energy spectrum of the selenium-doped modified silicon-carbon anode material prepared in Example 5 of this invention; Figure 4 This is a cycle performance diagram of the selenium-doped modified silicon-carbon anode materials prepared in Examples 1-4 of this invention. Detailed Implementation

[0017] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0018] This invention relates to a selenium-doped modified silicon-carbon anode material, comprising a silane-deposited silicon-carbon material and selenium doped therein. The silane-deposited silicon-carbon material is composed of porous carbon and nano-silicon, with the porous carbon serving as the silicon host and the nano-silicon acting as the active material and uniformly distributed within the porous carbon. Selenium is uniformly doped into the silicon-carbon material matrix, forming a selenium-doped modified silicon-carbon composite structure.

[0019] The process of selenium-doped modified silicon-carbon anode material is implemented according to the following steps: Step 1: In a glove box under an argon atmosphere, weigh the silicon-carbon material deposited by silane and elemental selenium (Se) powder according to the proportion, put them into an agate mortar and grind them together to obtain a mixed powder. In step 1, the mass ratio of silicon-carbon material to selenium powder in silane deposition is (3-10):1, and the grinding time is 15-30 min. Step 2: Place the ground mixed powder into a quartz tube and use a tube sealing machine to vacuum and seal it; Step 3: Place the sealed quartz tube into a muffle furnace and heat it using a programmed heating method. Hold it at that temperature for a certain period of time, then cool it down to room temperature before removing it. In step 3, the heat treatment heating rate is 1-5 °C / min, the temperature is raised to 350-500 °C, and the holding time is 10-15 h; Step 4: Disassemble the sealed quartz tube in an argon atmosphere glove box, then clean it in a fume hood, and finally dry, sieve and collect the product. The cleaning process includes: repeated rinsing and filtration with alcohol and deionized water; drying is done by vacuum drying at a temperature of 60-80 ℃ for 12-24 h.

[0020] This invention relates to a selenium-doped modified silicon-carbon anode material for use in lithium-ion batteries. This material innovatively incorporates selenium uniformly into a silane-deposited silicon-carbon matrix, introducing selenium into the anode material through a solid-phase selenization modification process. During the first discharge, the selenium in the material preferentially reacts with lithium to form Li₂Se with high ionic conductivity in situ. This reaction effectively suppresses the formation of irreversible Li₂O, thereby significantly reducing the thickness of the solid electrolyte interfacial film, lowering interfacial transport impedance, and minimizing irreversible capacity loss. Furthermore, the porous carbon matrix physically confines the selenium particles, effectively suppressing the shuttle effect of polyselenides and buffering the volume expansion of selenium during charge and discharge. The excellent electronic conductivity of selenium itself further improves the overall conductivity of the composite material, enhances electrode reaction kinetics, and increases the utilization rate of active materials. The development of a silicon-carbon anode with a selenium-doped modified structure provides a simple and efficient design concept for reducing interfacial impedance, improving first-time coulombic efficiency, and promoting the development of high-energy-density lithium-ion batteries.

[0021] Example 1 The preparation method of selenium-doped modified silicon-carbon anode material is carried out according to the following steps: Step 1: In an argon-atmospheric glove box, weigh the silane-deposited silicon-carbon material and elemental selenium (Se) powder in a ratio of 8:1, put them into an agate mortar and grind them to obtain a mixed powder. Step 2: Place the mixed powder ground in Step 1 into a quartz tube and use a tube sealing machine to vacuum and seal it. Step 3: Place the sealed quartz tube from Step 2 into a muffle furnace, heat it to 400℃ at a rate of 5℃ / min, and hold it for 12 hours.

[0022] Step 4: Open the sealed quartz tube in an argon atmosphere glove box, then rinse and filter it repeatedly with alcohol and deionized water in a fume hood. Finally, dry it under vacuum at 60°C for 12 hours and collect it by sieving.

[0023] Example 2 The preparation method of selenium-doped modified silicon-carbon anode material is carried out according to the following steps: Step 1: In a glove box under an argon atmosphere, weigh the silicon-carbon material deposited by silane and elemental selenium (Se) powder in a ratio of 10:1, put them into an agate mortar and grind them to obtain a mixed powder. Step 2: Place the mixed powder ground in Step 1 into a quartz tube and use a tube sealing machine to vacuum and seal it. Step 3: Place the sealed quartz tube from Step 2 into a muffle furnace, heat it to 400℃ at a rate of 5℃ / min, and hold it for 12 hours.

[0024] Step 4: The sealed quartz tube is disassembled inside a glove box under an argon atmosphere. Then, it is repeatedly rinsed and filtered with alcohol and deionized water in a fume hood. Finally, it is vacuum dried, sieved, and collected to obtain the final product. Its transmission electron microscopy morphology is as follows: Figure 1 As shown.

[0025] Example 3 The preparation method of selenium-doped modified silicon-carbon anode material is carried out according to the following steps: Step 1: In an argon-atmospheric glove box, weigh the silicon-carbon material deposited by silane and elemental selenium (Se) powder in a 4:1 ratio, put them into an agate mortar and grind them together to obtain a mixed powder. Step 2: Place the mixed powder ground in Step 1 into a quartz tube and use a tube sealing machine to vacuum and seal it. Step 3: Place the sealed quartz tube from Step 2 into a muffle furnace, heat it to 400℃ at a rate of 5℃ / min, and hold it for 12 hours.

[0026] Step 4: Open the sealed quartz tube in an argon atmosphere glove box, then rinse and filter it repeatedly with alcohol and deionized water in a fume hood, and finally dry it under vacuum and collect it by sieving.

[0027] Example 4 The preparation method of selenium-doped modified silicon-carbon anode material is carried out according to the following steps: Step 1: In an argon-atmosphere glove box, weigh the silane-deposited silicon-carbon material and elemental selenium (Se) powder in a 3:1 ratio, put them into an agate mortar and grind them to obtain a mixed powder. Step 2: Place the mixed powder ground in Step 1 into a quartz tube and use a tube sealing machine to vacuum and seal it. Step 3: Place the sealed quartz tube from Step 2 into a muffle furnace, heat it to 400℃ at a rate of 5℃ / min, and hold it for 12 hours.

[0028] Step 4: Open the sealed quartz tube in an argon atmosphere glove box, then rinse and filter it repeatedly with alcohol and deionized water in a fume hood. Finally, dry it under vacuum at 80°C for 24 hours and collect it by sieving.

[0029] Example 5 The preparation method of selenium-doped modified silicon-carbon anode material is carried out according to the following steps: Step 1: In an argon-atmospheric glove box, weigh the silane-deposited silicon-carbon material and elemental selenium (Se) powder in a ratio of 8:1, put them into an agate mortar and grind them to obtain a mixed powder. Step 2: Place the mixed powder ground in Step 1 into a quartz tube and use a tube sealing machine to vacuum and seal it. Step 3: Place the sealed quartz tube from Step 2 into a muffle furnace, heat it to 450°C at a rate of 3 °C / min, and hold it for 14 h.

[0030] Step 4: In a glove box under argon atmosphere, disassemble the sealed quartz tube. Then, in a fume hood, repeatedly rinse and filter the tube using alcohol and deionized water. Finally, dry the tube under vacuum at 75°C for 20 hours, sieve, and collect the final product. The EDS spectrum is shown below. Figure 3 As shown.

[0031] Example 6 The preparation method of selenium-doped modified silicon-carbon anode material is carried out according to the following steps: Step 1: In an argon-atmospheric glove box, weigh the silane-deposited silicon-carbon material and elemental selenium (Se) powder in a ratio of 8:1, put them into an agate mortar and grind them to obtain a mixed powder. Step 2: Place the mixed powder ground in Step 1 into a quartz tube and use a tube sealing machine to vacuum and seal it. Step 3: Place the sealed quartz tube from Step 2 into a muffle furnace, heat it to 400℃ at a rate of 3℃ / min, and hold it for 12 hours.

[0032] Step 4: Open the sealed quartz tube in an argon atmosphere glove box, then rinse and filter it repeatedly with alcohol and deionized water in a fume hood. Finally, dry it under vacuum at 75°C for 20 hours and collect it by sieving.

[0033] Example 7 The preparation method of selenium-doped modified silicon-carbon anode material is carried out according to the following steps: Step 1: In an argon-atmosphere glove box, weigh the silane-deposited silicon-carbon material and elemental selenium (Se) powder in a 3:1 ratio, put them into an agate mortar and grind them to obtain a mixed powder. Step 2: Place the mixed powder ground in Step 1 into a quartz tube and use a tube sealing machine to vacuum and seal it. Step 3: Place the sealed quartz tube from Step 2 into a muffle furnace, heat it to 400℃ at a rate of 3℃ / min, and hold it for 12 hours.

[0034] Step 4: Open the sealed quartz tube in an argon atmosphere glove box, then rinse and filter it repeatedly with alcohol and deionized water in a fume hood. Finally, dry it under vacuum at 75°C for 20 hours and collect it by sieving.

[0035] Example 8 The preparation method of selenium-doped modified silicon-carbon anode material is carried out according to the following steps: Step 1: In an argon-atmospheric glove box, weigh the silicon-carbon material deposited by silane and elemental selenium (Se) powder in a 4:1 ratio, put them into an agate mortar and grind them together to obtain a mixed powder. Step 2: Place the mixed powder ground in Step 1 into a quartz tube and use a tube sealing machine to vacuum and seal it. Step 3: Place the sealed quartz tube from Step 2 into a muffle furnace, heat it to 450°C at a rate of 3 °C / min, and hold it for 14 h.

[0036] Step 4: Open the sealed quartz tube in an argon atmosphere glove box, then rinse and filter it repeatedly with alcohol and deionized water in a fume hood. Finally, dry it under vacuum at 75°C for 20 hours and collect it by sieving.

[0037] Comparative Example 1 As a comparison, the preparation of silicon-carbon anode materials is carried out according to the following steps: Step 1: In an argon-atmospheric glove box, weigh out the silicon carbide material deposited by silane and put it into an agate mortar for mixing and grinding. Step 2: Place the powder ground in Step 1 into a quartz tube and use a tube sealing machine to vacuum and seal it. Step 3: Place the sealed quartz tube from Step 2 into a muffle furnace, heat it to 400℃ at a rate of 5℃ / min, and hold it for 12 hours.

[0038] Step 4: The sealed quartz tube is opened inside a glove box under an argon atmosphere. Then, it is repeatedly rinsed and filtered with alcohol and deionized water in a fume hood. Finally, it is vacuum dried at 60°C for 12 hours, sieved, and collected to obtain the final product. Its EDS spectrum is shown below. Figure 2 As shown.

[0039] Figure 4 The graphs show the cycle performance of the selenium-doped modified silicon-carbon anode materials prepared in Examples 1, 2, 3 and 4. At a current density of 1.0 C, the discharge specific capacity of the sample in Example 4, with a mass ratio of nano-silicon to selenium of 3:1, is higher than that of the sample in Example 1, with a mass ratio of 8:1.

[0040] This invention discloses a method for preparing selenium-doped modified silicon-carbon anode materials. Selenium powder is uniformly doped into a silicon-carbon matrix by solid-state grinding, vacuum sealing, and high-temperature heat treatment of silane-deposited silicon-carbon material. Using a porous carbon framework as the host, the confinement effect of selenium suppresses shuttle effects and volume expansion. During the first discharge, selenium generates Li₂Se in situ, inhibiting the formation of irreversible Li₂O, thinning the SEI film, reducing interfacial impedance, and improving the first coulombic efficiency. Simultaneously, the high conductivity of selenium further enhances the electron / ion diffusion kinetics of the composite material, improving the utilization rate of the active material.

Claims

1. A selenium-doped modified silicon-carbon anode material, characterized in that, The invention includes a silicon-carbon material deposited with silane and a selenium element doped therein. The silicon-carbon material deposited with silane is composed of porous carbon and nano-silicon. The porous carbon serves as the silicon host, and the nano-silicon serves as the active material and is uniformly distributed inside the porous carbon. The selenium element is uniformly doped into the silicon-carbon material matrix, forming a selenium-doped modified silicon-carbon composite structure.

2. The method for preparing selenium-doped modified silicon-carbon anode material according to claim 1, characterized in that, The specific steps are as follows: Step 1: In a glove box under an argon atmosphere, weigh the silicon carbide material deposited by silane and selenium powder according to the proportion, put them into an agate mortar and grind them together to obtain a mixed powder. Step 2: Place the ground mixed powder into a sealed container and use a tube sealing machine to vacuum and seal it; Step 3: Place the sealed quartz tube into a muffle furnace and heat it using a programmed heating method. Hold it at that temperature for a certain period of time, then cool it down to room temperature before removing it. Step 4: Disassemble the sealed quartz tube in an argon atmosphere glove box, then clean it in a fume hood, and finally dry, sieve and collect the product.

3. The method for preparing selenium-doped modified silicon-carbon anode material according to claim 2, characterized in that, In step 1, the mass ratio of the silicon-carbon material deposited by silane to the selenium powder is (6-125):1, and the grinding time is 15-30 min.

4. The method for preparing selenium-doped modified silicon-carbon anode material according to claim 2, characterized in that, In step 2, the sealed container is a quartz tube, and a tube sealing machine is used for vacuum sealing.

5. The method for preparing selenium-doped modified silicon-carbon anode material according to claim 2, characterized in that, In step 3, the heat treatment is carried out in a muffle furnace at a heating rate of 1-5 °C / min, heated to 350-500 °C, and held for 10-15 h.

6. The method for preparing selenium-doped modified silicon-carbon anode material according to claim 2, characterized in that, In step 3, after heat treatment, the temperature is reduced to room temperature at a rate of 1-3 °C / min.

7. The method for preparing selenium-doped modified silicon-carbon anode material according to claim 2, characterized in that, The cleaning process in step 4 includes: repeated rinsing and filtration with alcohol and deionized water; drying is done by vacuum drying at a temperature of 60-80℃ for 12-24 hours.

8. The application of the selenium-doped modified silicon-carbon anode material according to any one of claims 1-7 in lithium-ion batteries.

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