Secondary gas phase coated silicon monoxide negative electrode material and preparation method thereof

Abstract

The invention discloses a secondary gas phase coated silicon monoxide negative electrode material and a preparation method thereof, and belongs to the technical field of lithium ion battery electrode materials, a zinc metal frame is generated in situ on the surface of a graphene oxide nanosheet to obtain a zinc metal frame / graphene nanosheet, and the zinc metal frame / graphene nanosheet is coated with a secondary gas phase coated silicon monoxide negative electrode material. Mixing the zinc metal frame / graphene nanosheet with water-borne epoxy resin, coating the lanthanum-magnesium-doped secondary gas phase coated silicon monoxide powder, carbonizing to obtain carbon-coated lanthanum-magnesium-doped silicon monoxide powder, adding the carbon-coated lanthanum-magnesium-doped silicon monoxide powder, a binder, a conductive carbon black agent and deionized water into a mixing defoaming machine, stirring and mixing to obtain a mixture; and drying to obtain the secondary gas phase coated silicon monoxide negative electrode material. And the material has higher conductivity, first coulombic efficiency, 100-cycle capacity retention rate and lower volume change percentage.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery electrode materials, and specifically relates to a secondary gas-phase coated silicon monoxide negative electrode material and a preparation method thereof. Background Art

[0002] With the rapid development of new energy vehicles, wearable devices, energy storage systems and other fields, lithium-ion batteries, as their core power source, have increasingly higher requirements for energy density, cycle life and safety performance. As a key component of lithium-ion batteries, the performance of negative electrode materials directly affects the overall performance of the battery. At present, although commercial graphite negative electrode materials have been widely used, their theoretical specific capacity is limited and it is difficult to meet the needs of high-energy density batteries. Therefore, the development of new high-performance negative electrode materials has become a research hotspot in the field of lithium-ion batteries. As a potential high-capacity negative electrode material, silicon dioxide has a high theoretical specific capacity and a moderate lithium insertion potential, but it still has problems such as low first coulombic efficiency, low lithium desorption capacity and poor conductivity in practical applications.

[0003] The Chinese invention patent application with publication number CN112086630A discloses a method for preparing a silicon oxide composite negative electrode material and its product. The composite negative electrode material uses silicon and silicon dioxide as initial raw materials, generates silicon oxide through a neutralization reaction; after silicon oxide is vaporized, it is passed into a chemical vapor deposition furnace containing carbon material, and a primary product is obtained after chemical vapor deposition; finally, carbon coating is performed to obtain a silicon oxide composite negative electrode material. The lithium-ion battery assembled from the composite negative electrode material has a high capacity.

[0004] However, in lithium-ion battery products, lithium ions in silicon oxide negative electrode materials and positive electrode materials easily generate irreversible lithium oxide, resulting in a decrease in the product's first coulombic efficiency and capacity retention rate. Summary of the invention

[0005] The present invention dopes lanthanum magnesium with silicon oxide through a secondary gas phase reaction, loads a Zn metal framework on graphene oxide nanosheets, uniformly disperses them in water and combines them with a water-based epoxy resin, realizes double carbon coating by a spray drying method, and obtains a secondary gas phase coated silicon oxide negative electrode material through argon protection.

[0006] The purpose of the present invention can be achieved by the following technical solutions: A method for preparing a secondary gas-phase coated silicon oxide negative electrode material comprises the following steps: Step 1: in situ generating a zinc metal framework on the surface of graphene oxide nanosheets to obtain a zinc metal framework / graphene nanosheets, and then mixing the zinc metal framework / graphene nanosheets into a water-based epoxy resin and coating the lanthanum-doped magnesium secondary vapor-phase coated silicon oxide powder to obtain a resin-coated lanthanum-doped magnesium silicon oxide powder; Step 2: placing the resin-coated lanthanum-doped magnesium silicon oxide powder in a tube furnace, keeping the temperature at 600-800° C. for 30-60 minutes under argon protection, and naturally cooling to room temperature to obtain carbon-coated lanthanum-doped magnesium silicon oxide powder; Step 3: Add carbon-coated lanthanum-doped magnesium silicon oxide powder, a binder, a conductive carbon black agent and deionized water into a mixing degassing machine and stir for 15-30 minutes, and dry the product to constant weight to obtain a secondary gas-phase coated silicon oxide negative electrode material.

[0007] Furthermore, the mass ratio of the carbon-coated lanthanum-doped magnesium silicon oxide powder, the binder, the conductive carbon black agent and the deionized water is 8-10:1-3:1-3:15-17.

[0008] Furthermore, the zinc metal framework / graphene nanosheet is prepared by the following steps: N,N-dimethylformamide and anhydrous ethanol are mixed to obtain a mixed solution, 2-aminoterephthalic acid and acetic acid are dissolved in the mixed solution and added into a reactor, zinc acetate and graphene oxide nanosheets are added and ultrasonically dispersed for 10-20 minutes, kept at 100-150° C. for 8-12 hours, naturally cooled to room temperature, centrifuged to collect the precipitate, washed the precipitate with anhydrous ethanol, and dried to obtain zinc metal framework / graphene nanosheets.

[0009] Furthermore, the mixed liquid is obtained by mixing N,N-dimethylformamide and anhydrous ethanol in a mass ratio of 9:1.

[0010] Furthermore, the usage ratio of 2-aminoterephthalic acid, acetic acid, mixed solution, zinc acetate and graphene oxide nanosheets is 2-4 g: 0.8-1.2 g: 200 mL: 0.8-1.2 g: 1.5-2 g.

[0011] Furthermore, the resin-coated lanthanum-doped magnesium silicon oxide powder is specifically prepared by the following steps: Zinc metal framework / graphene nanosheets, water-based epoxy resin and water are added into a stirring kettle and stirred and mixed, and then lanthanum-doped magnesium secondary vapor-coated silicon oxide powder is added and ultrasonically dispersed for 15-30 minutes, the obtained mixture is spray-dried by a spray dryer, and the obtained powder is vacuum-dried at 90-110° C. for 4-6 hours to obtain resin-coated lanthanum-doped magnesium silicon oxide powder with a particle size of 4.5-5 μm.

[0012] Furthermore, the usage ratio of zinc metal framework / graphene nanosheets, water-based epoxy resin and water is 3-4g:60-80g:1000-1200mL.

[0013] Furthermore, the lanthanum-doped magnesium secondary vapor-coated silicon dioxide powder is prepared by the following steps: Lanthanum powder, magnesium powder, silicon powder and silicon dioxide powder are mixed evenly and transferred to a vacuum furnace, kept at a vacuum degree of 1-1.2 Pa and a temperature of 1000-1100°C for 2-4 hours, then heated to 1400-1500°C and kept for 20-24 hours, the product is naturally cooled to room temperature and ground to obtain lanthanum-doped magnesium secondary gas-coated silicon oxide powder with a particle size of 3-4 μm.

[0014] Furthermore, the mass ratio of lanthanum powder, magnesium powder, silicon powder and silicon dioxide powder is 0.1-0.3:1-1.2:3-3.2:6-6.2.

[0015] Beneficial effects of the present invention: 1. In the preparation process of the secondary gas phase coated silicon oxide negative electrode material of the present invention, firstly, a secondary gas phase reaction method is used to obtain lanthanum-doped magnesium secondary gas phase coated silicon oxide powder, and then zinc metal framework / graphene nanosheets are mixed into water-based epoxy resin and the lanthanum-doped magnesium secondary gas phase coated silicon oxide powder is coated to obtain resin-coated lanthanum-doped magnesium silicon oxide powder, which has higher electrical conductivity, first coulomb efficiency and 100 cycle capacity retention rate and lower volume change percentage.

[0016] 2. In the lanthanum-magnesium doped secondary vapor-coated silicon oxide powder of the present invention, the atomic radius of lanthanum and magnesium is relatively large, and a rigid network structure can be formed after doping, which can inhibit the volume expansion of the silicon oxide active phase. In addition, the doped lanthanum and magnesium reduce a part of the silicon oxide, reduce the oxygen content in the material, reduce the content of the irreversible lithium oxide phase generated by the reaction of the silicon oxide negative electrode material with lithium ions during the first charge, reduce the irreversible capacity of the silicon oxide negative electrode material, and thus improve the coulombic efficiency of the material.

[0017] 3. The resin-coated lanthanum-doped magnesium silicon oxide powder of the present invention has zinc metal framework / graphene nanosheets dispersed therein. After the zinc metal framework is composited with the graphene oxide nanosheets, the hydrophilicity of the graphene oxide nanosheets is utilized to improve its dispersibility in the waterborne epoxy resin and prevent the material from agglomerating. After the resin-coated lanthanum-doped magnesium silicon oxide powder is carbonized, the zinc metal framework therein forms zinc oxide particles with a stable porous structure, which can expand cracks and disperse stress when dispersed in the carbon-coated shell, and the zinc oxide may form a stable interface in the electrolyte, reduce side reactions, and improve cycle stability, thereby increasing the 100-cycle capacity retention rate of the silicon oxide negative electrode material. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Embodiment 1: A method for preparing a secondary gas-phase coated silicon oxide negative electrode material, comprising the following steps: S1: 0.1kg lanthanum powder, 1kg magnesium powder, 3kg silicon powder and 6kg silicon dioxide powder are mixed evenly and transferred to a vacuum furnace, kept at a vacuum degree of 1Pa and a temperature of 1000°C for 2h, and then heated to 1400°C and kept for 20h to generate silicon dioxide vapor, magnesium vapor and lanthanum vapor in the furnace. The evenly mixed gaseous mixture is rapidly condensed to form lanthanum magnesium-silicon dioxide material. The product is naturally cooled to room temperature and ground to obtain lanthanum-magnesium-doped secondary vapor-coated silicon dioxide powder with a particle size of 3-4μm.

[0020] As a strong reducing agent, magnesium preferentially reacts with silicon dioxide to form silicon monoxide under high temperature and vacuum conditions. The vapors of magnesium and lanthanum diffuse together in a vacuum to form a composite doping layer. The high diffusion rate of magnesium complements the strong oxidation tendency of lanthanum, inhibiting the coarsening, agglomeration and volume expansion of silicon grains and promoting uniform doping.

[0021] S2: N,N-dimethylformamide and anhydrous ethanol were mixed in a mass ratio of 9:1 to obtain a mixed solution, 2 g of 2-aminoterephthalic acid and 0.8 g of acetic acid were dissolved in 200 mL of the mixed solution and added to a reactor, 0.8 g of zinc acetate and 1.5 g of graphene oxide nanosheets were added and ultrasonically dispersed for 10 min, the mixture was kept at 100 °C for 8 h, naturally cooled to room temperature, and the precipitate was collected by centrifugation. The precipitate was washed 3 times with anhydrous ethanol and dried at 60 °C for 12 h to obtain zinc metal framework / graphene nanosheets.

[0022] S3: Add 3g zinc metal framework / graphene nanosheets, 60g water-based epoxy resin and 1000mL water into a stirring kettle, stir at a speed of 1000r / min for 30min, then add 100g lanthanum-doped magnesium secondary vapor-coated silicon oxide powder and ultrasonically disperse for 15min; the obtained mixed solution is spray dried using a spray dryer, and the obtained powder is vacuum dried at 90°C for 4h to obtain resin-coated lanthanum-doped magnesium silicon oxide powder with a particle size of 4.5-5μm.

[0023] S4: 30 g of resin-coated lanthanum-doped magnesium silicon oxide powder was placed in a tubular furnace, kept warm for 30 min under argon protection at 600° C., and naturally cooled to room temperature to obtain carbon-coated lanthanum-doped magnesium silicon oxide powder.

[0024] Epoxy resin is used as a carbon precursor. The hydroxyl groups and ether bonds on its molecular chain can be combined with the surface of lanthanum-doped magnesium silicon oxide through hydrogen bonds to form a uniformly coated composite slurry.

[0025] S5: Add carbon-coated lanthanum-doped magnesium silicon oxide powder, binder, conductive carbon black agent and deionized water in a mass ratio of 8:1:1:15 into a mixing degassing machine and stir for 15 minutes. Dry the product at 50°C to constant weight to obtain a secondary gas-coated silicon oxide negative electrode material.

[0026] Embodiment 2: A method for preparing a secondary gas-phase coated silicon oxide negative electrode material, comprising the following steps: S1: 0.2kg lanthanum powder, 1.1kg magnesium powder, 3.1kg silicon powder and 6.1kg silicon dioxide powder are mixed evenly and transferred to a vacuum furnace, and kept at a vacuum degree of 1.1Pa and a temperature of 1050°C for 3 hours, and then the temperature is raised to 1450°C and kept for 22 hours to generate silicon dioxide vapor, magnesium vapor and lanthanum vapor in the furnace. The evenly mixed gaseous mixture is rapidly condensed to form lanthanum magnesium-silicon dioxide material. The product is naturally cooled to room temperature and ground to obtain lanthanum-magnesium-doped secondary vapor-coated silicon dioxide powder with a particle size of 3-4um.

[0027] S2: N,N-dimethylformamide and anhydrous ethanol were mixed in a mass ratio of 9:1 to obtain a mixed solution, 3 g of 2-aminoterephthalic acid and 1 g of acetic acid were dissolved in 200 mL of the mixed solution and added to a reactor, 1 g of zinc acetate and 1.8 g of graphene oxide nanosheets were added and ultrasonically dispersed for 10-20 min, the mixture was kept at 120°C for 10 h, naturally cooled to room temperature, and the precipitate was collected by centrifugation. The precipitate was washed 4 times with anhydrous ethanol and dried at 70°C for 18 h to obtain zinc metal framework / graphene nanosheets.

[0028] S3: Add 3.5g zinc metal framework / graphene nanosheets, 70g water-based epoxy resin and 1100mL water into a stirring kettle, stir at a speed of 1100r / min for 50min, then add 110g lanthanum-doped magnesium secondary vapor-coated silicon oxide powder and ultrasonically disperse for 20min; the obtained mixed solution is spray dried using a spray dryer, and the obtained powder is vacuum dried at 100°C for 5h to obtain resin-coated lanthanum-doped magnesium silicon oxide powder with a particle size of 4.5-5μm.

[0029] S4: 40 g of resin-coated lanthanum-doped magnesium silicon oxide powder was placed in a tubular furnace, kept warm at 700° C. for 50 min under argon protection, and naturally cooled to room temperature to obtain carbon-coated lanthanum-doped magnesium silicon oxide powder.

[0030] S5: Add carbon-coated lanthanum-doped magnesium silicon dioxide powder, binder, conductive carbon black agent and deionized water in a mass ratio of 9:2:2:16 into a mixing degassing machine and stir for 20 minutes. Dry the product at 55°C to constant weight to obtain a secondary gas-coated silicon dioxide negative electrode material.

[0031] Embodiment 3: A method for preparing a secondary gas-phase coated silicon oxide negative electrode material, comprising the following steps: S1: 0.3kg lanthanum powder, 1.2kg magnesium powder, 3.2kg silicon powder and 6.2kg silicon dioxide powder are mixed evenly and transferred to a vacuum furnace, and kept at a vacuum degree of 1.2Pa and a temperature of 1100°C for 4 hours, and then the temperature is raised to 1500°C and kept for 24 hours to generate silicon dioxide vapor, magnesium vapor and lanthanum vapor in the furnace. The evenly mixed gaseous mixture is rapidly condensed to form lanthanum magnesium-silicon dioxide material. The product is naturally cooled to room temperature and ground to obtain lanthanum-magnesium-doped secondary vapor-coated silicon dioxide powder with a particle size of 3-4um.

[0032] S2: N,N-dimethylformamide and anhydrous ethanol were mixed in a mass ratio of 9:1 to obtain a mixed solution, 4 g of 2-aminoterephthalic acid and 1.2 g of acetic acid were dissolved in 200 mL of the mixed solution and added to a reactor, 1.2 g of zinc acetate and 2 g of graphene oxide nanosheets were added and ultrasonically dispersed for 20 min, the mixture was kept at 150°C for 12 h, naturally cooled to room temperature, and the precipitate was collected by centrifugation. The precipitate was washed 5 times with anhydrous ethanol and dried at 80°C for 24 h to obtain zinc metal framework / graphene nanosheets.

[0033] S3: Add 4g zinc metal framework / graphene nanosheets, 80g water-based epoxy resin and 1200mL water into a stirring kettle, stir at a speed of 1200r / min for 60min, then add 120g lanthanum-doped magnesium secondary vapor-coated silicon oxide powder and ultrasonically disperse for 30min; the obtained mixed solution is spray dried using a spray dryer, and the obtained powder is vacuum dried at 110°C for 6h to obtain resin-coated lanthanum-doped magnesium silicon oxide powder with a particle size of 4.5-5μm.

[0034] S4: 50 g of resin-coated lanthanum-doped magnesium silicon oxide powder was placed in a tubular furnace, kept warm at 800° C. for 60 min under argon protection, and naturally cooled to room temperature to obtain carbon-coated lanthanum-doped magnesium silicon oxide powder.

[0035] S5: Add carbon-coated lanthanum-doped magnesium silicon dioxide powder, binder, conductive carbon black agent and deionized water in a mass ratio of 10:3:3:17 into a mixing degassing machine and stir for 30 minutes. Dry the product at 60°C to constant weight to obtain a secondary gas-coated silicon dioxide negative electrode material.

[0036] The binder used in Examples 1 to 3 is polyvinylidene fluoride.

[0037] Comparative Example 1: The difference from Example 1 is that lanthanum powder is not added in step S1, and the prepared magnesium-doped secondary vapor-coated silicon oxide powder is used instead of the lanthanum-doped magnesium secondary vapor-coated silicon oxide powder, and the other steps remain unchanged to prepare silicon oxide negative electrode material.

[0038] Comparative Example 2: The difference from Example 1 is that lanthanum powder and magnesium powder are not added in step S1, and the prepared secondary vapor-coated silicon oxide powder is used instead of the lanthanum-magnesium-doped secondary vapor-coated silicon oxide powder, and the other steps remain unchanged to obtain silicon oxide negative electrode material.

[0039] Comparative Example 3: The difference from Example 1 is that in step S3, conventional graphene oxide nanosheets are used to replace the zinc metal framework / graphene nanosheets prepared in step S2, and the other steps remain unchanged to obtain a silicon oxide negative electrode material.

[0040] The secondary gas-coated silicon oxide negative electrode materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were respectively mixed with acetylene black and polyvinylidene fluoride in a mass ratio of 8:1:1, ground with nitrogen methyl pyrrolidone as a solvent to form a uniform slurry and coated on a copper foil, dried at 90°C in vacuum for 24 hours, and rolled to obtain an electrode sheet; the obtained negative electrode sheet was cut into electrode sheets with a diameter of 12 mm for battery assembly.

[0041] The assembly process was carried out in a glove box filled with argon, and the water and oxygen content was less than 0.01ppm. The battery used a CR2032 button cell, with a metal lithium sheet as the counter electrode, a polypropylene film as the diaphragm, and 1M lithium hexafluorophosphate as the electrolyte. The assembled button cell was subjected to a 0.5C charge and discharge cycle performance test at 25°C and a voltage range of 0.01-1.5V. The battery conductivity, first coulomb efficiency, volume change percentage, and 100 cycle capacity retention rate were recorded and measured. The results are shown in Table 1: Table 1: Performance test results project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Conductivity (S / cm) 32.1 32.8 33.4 31.3 32.2 32.0 First coulombic efficiency (%) 89.3 89.9 91.2 86.5 85.4 89.5 Volume change percentage (%) 80 78 77 88 90 96 100 cycles capacity retention rate (%) 82.7 83.3 84.2 76.8 75.3 72.8

[0042] It can be seen from Table 1 that the performance of the secondary gas-coated silicon 2 oxide negative electrode materials prepared in Examples 1 to 3 of the present invention is significantly better than that of the comparative example, with higher conductivity, first coulombic efficiency and 100 cycle capacity retention rate and lower volume change percentage.

[0043] The first coulombic efficiency and capacity retention rate in Comparative Examples 1 and 2 decreased significantly, while the volume change percentage increased. This is because the lanthanum-magnesium-doped secondary vapor-phase coated silicon oxide powder has a better performance improvement effect in this aspect than the silicon oxide material alone. This may be because the atomic radius of lanthanum and magnesium is large, and a rigid network structure can be formed after doping, which can inhibit the volume expansion of the silicon oxide active phase. In addition, the doped lanthanum and magnesium reduce part of the silicon oxide, reduce the oxygen content in the material, and reduce the content of the irreversible lithium oxide phase generated by the reaction of the silicon oxide negative electrode material with lithium ions during the first charge, thereby reducing the irreversible capacity of the silicon oxide negative electrode material, thereby improving the coulombic efficiency of the material.

[0044] The percentage of volume change in comparative example 3 increased and the capacity retention rate after 100 cycles decreased significantly, which may be because after the zinc metal framework / graphene nanosheet filler is carbonized, the zinc metal framework forms zinc oxide particles with a stable porous structure, which are dispersed in the carbon-coated shell and can expand cracks and disperse stress. If it is not added, the percentage of volume change of the silicon oxide negative electrode material will increase. In addition, zinc oxide may form a stable interface in the electrolyte, reduce side reactions, and improve cycle stability, thereby increasing the capacity retention rate of the silicon oxide negative electrode material after 100 cycles.

[0045] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that many changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a secondary gas-phase coated silicon oxide negative electrode material, characterized in that: The steps include: Step 1: in situ generating a zinc metal framework on the surface of graphene oxide nanosheets to obtain a zinc metal framework / graphene nanosheets, and then mixing the zinc metal framework / graphene nanosheets into a water-based epoxy resin and coating the lanthanum-doped magnesium secondary vapor-phase coated silicon oxide powder to obtain a resin-coated lanthanum-doped magnesium silicon oxide powder; Step 2: placing the resin-coated lanthanum-doped magnesium silicon oxide powder in a tube furnace, keeping the temperature at 600-800° C. for 30-60 minutes under argon protection, and naturally cooling to room temperature to obtain carbon-coated lanthanum-doped magnesium silicon oxide powder; Step 3: Add carbon-coated lanthanum-doped magnesium silicon oxide powder, a binder, a conductive carbon black agent and deionized water into a mixing degassing machine and stir for 15-30 minutes, and dry the product to constant weight to obtain a secondary gas-phase coated silicon oxide negative electrode material.

2. The method for preparing a secondary gas-phase coated silicon oxide negative electrode material according to claim 1, characterized in that: The mass ratio of the carbon-coated lanthanum-doped magnesium silicon oxide powder, the binder, the conductive carbon black agent and the deionized water in step three is 8-10:1-3:1-3:15-17.

3. The method for preparing a secondary gas-phase coated silicon oxide negative electrode material according to claim 1, characterized in that: The zinc metal framework / graphene nanosheet is specifically prepared by the following steps: N,N-dimethylformamide and anhydrous ethanol are mixed to obtain a mixed solution, 2-aminoterephthalic acid and acetic acid are dissolved in the mixed solution and added into a reactor, zinc acetate and graphene oxide nanosheets are added and ultrasonically dispersed for 10-20 minutes, kept at 100-150° C. for 8-12 hours, naturally cooled to room temperature, centrifuged to collect the precipitate, washed the precipitate with anhydrous ethanol, and dried to obtain zinc metal framework / graphene nanosheets.

4. The method for preparing a secondary gas-phase coated silicon oxide negative electrode material according to claim 3, characterized in that: The mixed liquid is obtained by mixing N,N-dimethylformamide and anhydrous ethanol in a mass ratio of 9:

1.

5. The method for preparing a secondary gas-phase coated silicon oxide negative electrode material according to claim 3, characterized in that: The usage ratio of the 2-aminoterephthalic acid, acetic acid, mixed solution, zinc acetate and graphene oxide nanosheets is 2-4g: 0.8-1.2g: 200mL: 0.8-1.2g: 1.5-2g.

6. The method for preparing a secondary gas-phase coated silicon oxide negative electrode material according to claim 1, characterized in that: The resin-coated lanthanum-doped magnesium silicon oxide powder is specifically prepared by the following steps: Zinc metal framework / graphene nanosheets, water-based epoxy resin and water are added into a stirring kettle and stirred and mixed, and then lanthanum-doped magnesium secondary vapor-coated silicon oxide powder is added and ultrasonically dispersed for 15-30 minutes, the obtained mixture is spray-dried by a spray dryer, and the obtained powder is vacuum-dried at 90-110° C. for 4-6 hours to obtain resin-coated lanthanum-doped magnesium silicon oxide powder with a particle size of 4.5-5 μm.

7. The method for preparing a secondary gas-phase coated silicon oxide negative electrode material according to claim 6, characterized in that: The usage ratio of the zinc metal framework / graphene nanosheets, water-based epoxy resin and water is 3-4 g: 60-80 g: 1000-1200 mL.

8. The method for preparing a secondary gas-phase coated silicon oxide negative electrode material according to claim 1, characterized in that: The lanthanum-doped magnesium secondary vapor-phase coated silicon dioxide powder is prepared by the following steps: Lanthanum powder, magnesium powder, silicon powder and silicon dioxide powder are mixed evenly and transferred to a vacuum furnace, kept at a vacuum degree of 1-1.2 Pa and a temperature of 1000-1100°C for 2-4 hours, then heated to 1400-1500°C and kept for 20-24 hours, the product is naturally cooled to room temperature and ground to obtain lanthanum-doped magnesium secondary gas-coated silicon oxide powder with a particle size of 3-4 μm.

9. The method for preparing a secondary gas-phase coated silicon oxide negative electrode material according to claim 8, characterized in that: The mass ratio of the lanthanum powder, magnesium powder, silicon powder and silicon dioxide powder is 0.1-0.3:1-1.2:3-3.2:6-6.

2.

10. A secondary gas-phase coated silicon oxide negative electrode material, characterized in that: The material is prepared by the method for preparing a secondary gas-phase coated silicon monoxide negative electrode material as described in any one of claims 1 to 9.