A silicon oxide-based carbon-coated modified composite anode material and its preparation method

Abstract

The present invention discloses a silicon oxide-based carbon-coated modified composite anode material and a preparation method thereof. The preparation method includes the following steps: S1. Mix the crystallized silicon oxide, graphite and absolute ethanol uniformly to obtain a mixed slurry; S2. Add tin dioxide and alginic acid or sodium alginate to water and stir to completely dissolve the alginic acid or sodium alginate to obtain a mixed solution; S3. Pour the mixed solution into the mixed slurry obtained in step S1, add water to prepare a slurry with a solid-liquid ratio of 1:10 - 1:30 g / mL, and dry to obtain a precursor of the silicon oxide-based carbon-coated modified composite anode material; S4. Calcinate the precursor obtained in step S3 to obtain the silicon oxide-based carbon-coated modified composite anode material. The silicon oxide-based carbon-coated modified composite anode material obtained by the preparation method proposed by the present invention has the advantages of simple operation, easy control of conditions, good reproducibility, stable electrochemical performance, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of anode material preparation, and particularly to a silicon oxide-based carbon-coated modified composite anode material and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are the most commercially valuable energy storage systems and are widely used in fields such as electronic products and new energy vehicles. After more than a decade of rapid development, new energy vehicles have become an important driving force for the domestic automotive market. Currently, the development of commercial lithium-ion batteries has entered a technical bottleneck and it is difficult to meet the requirements of new energy vehicles for high capacity and high endurance of lithium-ion batteries. It is imperative to develop lithium-ion batteries with high specific energy and improve the power density and efficiency of drive motors and electronic control systems.

[0003] The huge volume change of silicon oxide anode materials during lithium insertion and extraction can lead to pulverization and shedding of the active materials of the electrode, as well as defects such as low initial coulombic efficiency and poor cycle performance, and cannot meet the usage requirements of the battery. CN114937763A discloses a silicon oxide composite anode material and a preparation method thereof. Crystallized micron-scale silicon oxide and commercially available artificial graphite are ball-milled. After the organic carbon source and the oxide are uniformly mixed, a silicon oxide composite anode material is obtained through spray drying and high-temperature pyrolysis. The composite structure of the silicon oxide anode material achieved by this method is that the silicon oxide is in full contact with the graphite matrix, and a layer of amorphous carbon is coated on the outer layer of the particles compounded with the introduced tin oxide. The artificial graphite of the silicon oxide composite anode material has high conductivity and can provide an effective buffer space; in addition to forming a conductive network and buffering expansion, the amorphous carbon layer can prevent silicon oxide particles from agglomerating and reduce the direct contact between silicon oxide and the electrolyte; tin oxide can improve the overall conductivity of the material. The constructed composite structure can improve the initial charge-discharge efficiency, cycle stability, and rate performance of the silicon oxide anode material. Due to the formation of a stable SEI film on the surface of the electrode and the electrolyte, maintaining a stable material structure, the electrode surface is flat and there are no obvious cracks. However, the electrochemical performance of the composite anode material obtained by this technology still needs to be continuously improved. CN116230883A discloses a high-performance silicon oxide-based composite anode material for lithium-ion batteries and a preparation method thereof. On the basis of CN114937763A, Fe-Si75 and TiSi2 alloys are further introduced to modify the silicon oxide anode material using silicon-containing alloy materials. In addition, a carbon-coated silicon oxide composite anode material is obtained by compounding titanium oxide with silicon oxide / graphite. The obtained series of novel silicon oxide-based composite anode materials have good compatibility with high-voltage and conventional electrolytes and exhibit excellent electrochemical performance. However, the problem of the volume expansion effect of silicon oxide still has not been solved. Summary of the Invention

[0004] The object of the present invention is to provide a silicon oxide-based carbon-coated modified composite anode material and a preparation method thereof. The composite structure of the silicon oxide-based carbon-coated modified composite anode material provided by the present invention is that silicon oxide and tin oxide form a composite phase and adhere between multi-layered flaky graphite, and the periphery of the particles is coated with a carbon layer formed by the pyrolysis of alginic acid or sodium alginate, which can effectively inhibit the volume expansion of the active material to a certain extent. At the same time, by using the characteristic that the aqueous solution of alginic acid or sodium alginate has a certain viscosity, it plays a role in strengthening the binding ability between silicon oxide, tin oxide and multi-layered flaky graphite, and provides the possibility for constructing the spherical or quasi-spherical particle morphology of the composite anode material.

[0005] The present invention is realized through the following technical solutions:

[0006] A preparation method of a silicon oxide-based carbon-coated modified composite anode material, comprising the following steps:

[0007] S1. Mix the crystallized silicon oxide, graphite and absolute ethanol evenly and perform ball milling treatment to obtain a mixed slurry;

[0008] S2. Add tin dioxide and alginic acid or sodium alginate to water and stir to completely dissolve the alginic acid or sodium alginate to obtain a mixed solution. The addition amount of tin dioxide is 0.5%-2% of the weight percentage of the mixture of the crystallized silicon oxide and graphite, and the addition amount of alginic acid or sodium alginate is 5%-20% of the weight percentage of the mixture of the crystallized silicon oxide and graphite;

[0009] S3. Pour the mixed solution obtained in step S2 into the mixed slurry obtained in step S1, screen out the slurry with a mesh size of 80-120 meshes, add water to prepare a slurry with a solid-liquid ratio of 1:10-1:30 g / mL, and dry to obtain a precursor of the silicon oxide-based carbon-coated modified composite anode material;

[0010] S4. Calcinate the precursor obtained in step S3 to obtain the silicon oxide-based carbon-coated modified composite anode material.

[0011] The present invention selects alginic acid and sodium alginate as carbon sources. Alginic acid and sodium alginate are natural polymer organic substances with rich hydroxyl and carboxyl groups on the surface, and their aqueous solutions have high viscosity. With the help of the carbon coating layer with good conductivity and toughness formed after their pyrolysis, the conductivity of the composite material is improved, and the volume expansion effect of silicon oxide is buffered, further realizing the technical effects of improving the first charge-discharge efficiency and cycle stability of the silicon oxide-based carbon-coated modified composite anode material.

[0012] Preferably, the specific steps of the crystallization treatment of the silicon oxide in step S1 are as follows: micron-scale silicon monoxide is placed in a heat treatment container under the protection of an argon atmosphere, heated to 1000°C - 1100°C, and kept warm for 2.5 - 3.5 h to obtain the crystallized silicon oxide (SiO x ).

[0013] Preferably, the mass ratio of the crystallized silicon oxide to graphite in step S1 is 1:8 - 10, and the mass-to-volume ratio of the crystallized silicon oxide to absolute ethanol is 1:14 - 16 g / mL.

[0014] More preferably, the mass ratio of the crystallized silicon oxide to graphite in step S1 is 1:9, and the mass-to-volume ratio of the crystallized silicon oxide to absolute ethanol is 1:15 g / mL.

[0015] Preferably, the conditions for the ball milling treatment in step S1 are: the ball-to-material ratio is 20:1, and the ball milling is carried out at a rotation speed of 150 - 250 rpm for 0.5 - 1.5 h.

[0016] Preferably, the addition amount of tin dioxide in step S2 is 1% of the weight percentage of the mixture of the crystallized silicon oxide and graphite, and the addition amount of alginic acid or sodium alginate is 5% - 10% of the weight percentage of the mixture of the crystallized silicon oxide and graphite.

[0017] Preferably, the drying in step S3 is spray drying, and the conditions for spray drying are: the inlet air temperature is 180°C - 220°C, the outlet air temperature is 130°C - 150°C, and the feeding rate is 250 - 350 mL / h.

[0018] Preferably, the calcination temperature in step S4 is 500°C - 600°C, and the time is 2 - 6 h.

[0019] The present invention also protects the silicon oxide-based carbon-coated modified composite anode material obtained by the above preparation method. Using alginic acid or sodium alginate as the organic carbon source, the SnO2 in the prepared composite anode material is more easily reduced to Sn, thereby improving the electrochemical performance of the material. The silicon oxide-based carbon-coated modified composite anode material prepared by this method has the advantages of simple operation, easy control of conditions, good reproducibility, and stable electrochemical performance.

[0020] The present invention also protects a lithium-ion battery using the silicon oxide-based carbon-coated modified composite anode material as the anode material.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: The composite structure of the silicon oxide-based composite anode material provided by the present invention is that silicon oxide and tin oxide form a composite phase and adhere between multi-layered flaky graphite, and the periphery of the particles is coated with a carbon layer formed by the pyrolysis of alginic acid or sodium alginate, which can effectively inhibit the volume expansion of the active material to a certain extent. At the same time, by utilizing the characteristic that the aqueous solution of alginic acid or sodium alginate has a certain viscosity, it plays a role in strengthening the binding ability between silicon oxide, tin oxide and multi-layered flaky graphite, providing the possibility for constructing the spherical or quasi-spherical particle morphology of the composite anode material. In addition, using sodium alginate as the organic carbon source, the SnO2 in the prepared composite anode material is more easily reduced to Sn, thereby improving the electrochemical performance of the material. The silicon oxide-based carbon-coated modified composite anode material prepared by this method has the advantages of simple operation, easy control of conditions, good reproducibility, and stable electrochemical performance. Description of the Drawings

[0022] Figure 1 SEM image of the silicon oxide-based carbon-coated modified composite anode material obtained in Example 1.

[0023] Figure 2 SEM image of the silicon oxide-based carbon-coated modified composite anode material obtained in Example 3.

[0024] Figure 3 SEM image of the silicon oxide-based carbon-coated modified composite anode material obtained in Example 6.

[0025] Figure 4 SEM image of the silicon oxide-based carbon-coated modified composite anode material obtained in Example 7.

[0026] Figure 5 SEM image of the silicon oxide-based carbon-coated modified composite anode material obtained in Example 8.

[0027] Figure 6 SEM image of the silicon oxide-based carbon-coated modified composite anode material obtained in Example 9.

[0028] Figure 7 SEM image of the silicon oxide-based carbon-coated modified composite anode material obtained in Example 10.

[0029] Figure 8 TEM image of the silicon oxide-based carbon-coated modified composite anode material obtained in Example 1.

[0030] Figure 9 TEM image of the silicon oxide-based carbon-coated modified composite anode material obtained in Example 10.

[0031] Figure 10 SEM image of the SiO material obtained in Comparative Example 1.

[0032] Figure 11 SEM image of the composite anode material obtained in Comparative Example 2. Detailed implementation manners

[0033] The present invention will be further described in detail below in conjunction with embodiments. These embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. For the experimental methods without specific conditions in the following embodiments, they are usually carried out according to the conventional conditions in the art or according to the conditions recommended by the manufacturer; the raw materials, reagents, etc. used, unless otherwise specified, are regarded as raw materials and reagents that can be obtained through commercial channels such as the conventional market. In the following embodiments, the solid-liquid ratio refers to the mass-volume ratio of solid to liquid, with the unit of g / mL.

[0034] The anode materials prepared in the following examples and comparative examples were made into 2032-type button-shaped simulated batteries to test their electrochemical performance. The specific steps were as follows: Weigh the active material (the material obtained in the example or comparative example), acetylene black, SBR, and CMC according to a mass ratio of 8:1:0.5:0.5. First, dissolve SBR and CMC in deionized water, and then add the uniformly mixed active material and acetylene black powder into it to make a slurry, which was uniformly coated on the copper foil substrate. The wet electrode was placed in a vacuum drying oven and dried at 80 °C for 12 h. In a dry vacuum glove box, a simulated battery was assembled. The self-made electrode above was used as the positive electrode, a lithium metal sheet was used as the negative electrode, and a Celgard 2500 membrane was used as the separator. The test voltage range was 0.01 - 1.5 V.

[0035] Example 1

[0036] Select micron-sized silicon monoxide with an average particle size of 3 μm and place it in a heat treatment furnace under argon atmosphere protection, heat it to 1050 °C, and keep it warm for 3 h to obtain the crystallized SiO x material. Weigh 4 g of SiO x and 36 g of artificial graphite respectively, add 60 mL of absolute ethanol, stir evenly, place the mixture in a planetary ball mill, with a ball-to-material ratio of 20:1, and ball mill at a speed of 200 rpm for 1 h to obtain a mixed slurry of SiO x and artificial graphite. Add tin dioxide and alginic acid to deionized water and stir magnetically for 30 min until the alginic acid is completely dissolved. The addition amounts of tin dioxide and alginic acid are 1% and 20% of the weight percentage of the mixture of SiO x and artificial graphite respectively. Pour the mixed solution of tin dioxide and alginic acid into SiO xThe mixed slurry with artificial graphite was screened to obtain a 100-mesh slurry, and then deionized water was added to prepare a slurry with a solid-liquid ratio of 1:20. It was magnetically stirred for 1 h and then spray-dried. The inlet air temperature of the spray-drying equipment was set at 200 °C, the outlet air temperature was 140 °C, and the feeding rate was 300 mL / h. The precursor of the (SiO x / G / SnO2)@C composite material passing through 300 meshes was screened out. The precursor was placed in a tubular furnace under an argon atmosphere and heated to 500 °C at a rate of 5 °C / min and held for 4 h to obtain the (SiO x / G / SnO2)@C composite anode material.

[0037] The composite anode material was assembled into a coin cell to test its electrochemical performance. When charged and discharged at 100 mA / g, the first charge-discharge efficiency reached 71.7%; when discharged at 200 mA / g for 200 cycles, the capacity retention rate was 94.9%.

[0038] Example 2

[0039] Micron-sized silicon monoxide with an average particle size of 3 μm was selected and placed in a heat treatment furnace under an argon atmosphere protection, heated to 1050 °C, and held for 3 h to obtain the crystallized SiO x material. 4 g of SiO x and 36 g of artificial graphite were weighed respectively, 60 mL of absolute ethanol was added, and they were stirred evenly. The mixture was placed in a planetary ball mill with a ball-to-material ratio of 20:1 and ball-milled at a speed of 200 rpm for 1 h to obtain the mixed slurry of SiO x and artificial graphite. Tin dioxide and alginic acid were added to deionized water and magnetically stirred for 30 min until the alginic acid was completely dissolved. The addition amounts of tin dioxide and alginic acid were 1% and 20% of the weight percentage of the mixture of SiO x and artificial graphite respectively. The mixed solution of tin dioxide and alginic acid was poured into the mixed slurry of SiO x and artificial graphite, and the 100-mesh slurry was screened out. Then deionized water was added to prepare a slurry with a solid-liquid ratio of 1:20. It was magnetically stirred for 1 h and then spray-dried. The inlet air temperature of the spray-drying equipment was set at 200 °C, the outlet air temperature was 140 °C, and the feeding rate was 300 mL / h. The precursor of the (SiO x / G / SnO2)@C composite material passing through 300 meshes was screened out. The precursor was placed in a tubular furnace under an argon atmosphere and heated to 600 °C at a rate of 5 °C / min and held for 2 h to obtain the (SiO x / G / SnO2)@C composite anode material.

[0040] The composite anode material was assembled into a coin cell to test its electrochemical performance. When charged and discharged at 100 mA / g, the first charge-discharge efficiency reached 73.2%; when discharged at 200 mA / g, it cycled for 189 weeks and the capacity retention rate was 89.9%.

[0041] Example 3

[0042] Micron-sized silicon monoxide with an average particle size of 3 μm was selected and placed in a heat treatment furnace under argon atmosphere protection, heated to 1050 °C, and held for 3 h to obtain the crystallized SiO x material. 4 g of SiO x and 36 g of artificial graphite were weighed respectively, 60 mL of absolute ethanol was added, and the mixture was stirred evenly. The mixture was placed in a planetary ball mill with a ball-to-material ratio of 20:1 and ball milled at a speed of 200 rpm for 1 h. The slurry with a mesh size of 100 was screened out to obtain the mixed slurry of SiO x and artificial graphite. Tin dioxide and alginic acid were added to deionized water and magnetically stirred for 30 min until the alginic acid was completely dissolved. The addition amounts of tin dioxide and alginic acid were 1% and 20% of the weight percentage of the mixture of SiO x and artificial graphite respectively. The mixed solution of tin dioxide and alginic acid was poured into the mixed slurry of SiO x and artificial graphite, and the slurry with a mesh size of 100 was screened out. Then deionized water was added to make a slurry with a solid-liquid ratio of 1:20, and it was magnetically stirred for 1 h and then spray-dried. The inlet air temperature of the spray drying equipment was set at 200 °C, the outlet air temperature was 140 °C, and the feeding rate was 300 mL / h. The precursor of the (SiO x / G / SnO2)@C composite material passing through 300 meshes was screened out. The precursor was placed in a tubular furnace under argon atmosphere and heated to 600 °C at a rate of 5 °C / min and held for 4 h to obtain the (SiO x / G / SnO2)@C composite anode material. The composite material was assembled into a coin cell to test its electrochemical performance. When charged and discharged at 100 mA / g, the first charge-discharge efficiency reached 70.0%; when discharged at 200 mA / g, it cycled for 300 weeks and the capacity retention rate was 90.4%.

[0043] Example 4

[0044] Micron-sized silicon monoxide with an average particle size of 3 μm was selected and placed in a heat treatment furnace under argon atmosphere protection, heated to 1050 °C, and held for 3 h to obtain the crystallized SiO x material. 4 g of SiO x and 36 g of artificial graphite were weighed respectively, 60 mL of absolute ethanol was added, and the mixture was stirred evenly. The mixture was placed in a planetary ball mill with a ball-to-material ratio of 20:1 and ball milled at a speed of 200 rpm for 1 h to obtain SiO xThe mixed slurry with artificial graphite. Tin dioxide and sodium alginate were added to deionized water and magnetically stirred for 30 min until the sodium alginate was completely dissolved. The addition amounts of tin dioxide and sodium alginate were 1% and 5% of the weight percentages of the mixture of SiO x and artificial graphite, respectively. The mixed solution of tin dioxide and sodium alginate was poured into the mixed slurry of SiO x and artificial graphite. The slurry with 100 meshes was screened out, and then deionized water was added to prepare a slurry with a solid-liquid ratio of 1:20. After magnetic stirring for 1 h, spray drying was carried out. The inlet air temperature of the spray drying equipment was set at 200 °C, the outlet air temperature was 140 °C, and the feeding rate was 300 mL / h. The precursor of the (SiO x / G / SnO2)@C composite material passing through 300 meshes was screened out. The precursor was placed in a tubular furnace under an argon atmosphere and heated to 600 °C at a rate of 5 °C / min and held for 4 h to obtain the (SiO x / G / SnO2)@C composite anode material. The composite material was assembled into a button cell to test its electrochemical performance. Charging and discharging were carried out at 100 mA / g, and the first charging and discharging efficiency reached 75.8%; discharging was carried out at 200 mA / g for 490 cycles, and the capacity retention rate was 84.3%.

[0045] Example 5

[0046] Microcrystalline silicon oxide with an average particle size of 3 μm was selected and placed in a heat treatment furnace under an argon atmosphere protection, heated to 1050 °C, and held for 3 h to obtain the crystallized SiO x material. 4 g of SiO x and 36 g of artificial graphite were weighed respectively, 60 mL of absolute ethanol was added, and the mixture was stirred evenly. The mixture was placed in a planetary ball mill with a ball-to-material ratio of 20:1 and ball milled at a speed of 200 rpm for 1 h to obtain the mixed slurry of SiO x and artificial graphite. Tin dioxide and sodium alginate were added to deionized water and magnetically stirred for 30 min until the sodium alginate was completely dissolved. The addition amounts of tin dioxide and sodium alginate were 1% and 20% of the weight percentages of the mixture of SiO x and artificial graphite, respectively. The mixed solution of tin dioxide and sodium alginate was poured into the mixed slurry of SiO x and artificial graphite. The slurry with 100 meshes was screened out, and then deionized water was added to prepare a slurry with a solid-liquid ratio of 1:20. After magnetic stirring for 1 h, spray drying was carried out. The inlet air temperature of the spray drying equipment was set at 200 °C, the outlet air temperature was 140 °C, and the feeding rate was 300 mL / h. The precursor of the (SiO x / G / SnO2)@C composite material passing through 300 meshes was screened out. The precursor was placed in a tubular furnace under an argon atmosphere and heated to 600 °C at a rate of 5 °C / min and held for 2 h to obtain the (SiO x(SiO₂ / G / SnO₂)@C composite anode material. The composite material was assembled into a coin cell to test its electrochemical performance. When charged and discharged at 100 mA / g, the first charge-discharge efficiency reached 72.6%; when discharged at 200 mA / g, after 210 cycles, the capacity retention rate was 120.6%.

[0047] Example 6

[0048] Select micron-sized silicon monoxide with an average particle size of 3 μm and place it in a heat treatment furnace under argon atmosphere protection. Heat it to 1050 °C and hold for 3 h to obtain crystallized SiO x material. Weigh 4 g of SiO x and 36 g of artificial graphite respectively, add 60 mL of absolute ethanol, stir evenly, place the mixture in a planetary ball mill, with a ball-to-material ratio of 20:1, and ball mill at a speed of 200 rpm for 1 h to obtain SiO x and artificial graphite mixed slurry. Add tin dioxide and sodium alginate to deionized water and stir magnetically for 30 min until the sodium alginate is completely dissolved. The addition amounts of tin dioxide and sodium alginate are 1% and 20% of the weight percentage of the mixture of SiO x [[ID=1...]]and artificial graphite respectively. Pour the mixed solution of tin dioxide and sodium alginate into the mixed slurry of SiO x and artificial graphite, screen out the slurry with a mesh size of 100, then add deionized water to make a slurry with a solid-liquid ratio of 1:20, stir magnetically for 1 h, and perform spray drying. Set the inlet air temperature of the spray drying equipment to 200 °C, the outlet air temperature to 140 °C, and the feeding rate to 300 mL / h. Screen out the precursor of (SiO x / G / SnO₂)@C composite material. Place the precursor in a tubular furnace under argon atmosphere, heat it to 600 °C at a rate of 5 °C / min, and hold for 4 h to obtain (SiO x (SiO₂ / G / SnO₂)@C composite anode material. The composite material was assembled into a coin cell to test its electrochemical performance. When charged and discharged at 100 mA / g, the first charge-discharge efficiency reached 72.8%; when discharged at 200 mA / g, after 500 cycles, the capacity retention rate was 106.2%.

[0049] Example 7

[0050] Select micron-sized silicon monoxide with an average particle size of 3 μm and place it in a heat treatment furnace under argon atmosphere protection. Heat it to 1050 °C and hold for 3 h to obtain crystallized SiO x material. Weigh 4 g of SiO x and 36 g of artificial graphite respectively, add 60 mL of absolute ethanol, stir evenly, place the mixture in a planetary ball mill, with a ball-to-material ratio of 20:1, and ball mill at a speed of 200 rpm for 1 h to obtain SiO xand artificial graphite mixed slurry. Tin dioxide and sodium alginate were added to 50 mL of deionized water and magnetically stirred for 30 min until the sodium alginate was completely dissolved. The addition amounts of tin dioxide and sodium alginate were 1% and 5% of the weight percentage of the SiO x and artificial graphite mixture, respectively. The mixed solution of tin dioxide and sodium alginate was poured into the SiO x and artificial graphite mixed slurry. The slurry with 100 mesh was screened out, and then deionized water was added to prepare a slurry with a solid-liquid ratio of 1:20. After magnetic stirring for 1 h, spray drying was carried out. The inlet air temperature of the spray drying equipment was set at 200 °C, the outlet air temperature was 140 °C, and the feeding rate was 300 mL / h. The precursor of the (SiO x / G / SnO2)@C composite material passing through 300 mesh was screened out. The precursor was placed in a tubular furnace under an argon atmosphere and heated to 500 °C at a rate of 5 °C / min and held for 4 h to obtain the (SiO x / G / SnO2)@C composite anode material. The composite material was assembled into a button cell to test its electrochemical performance. When charging and discharging at 100 mA / g, the initial charge-discharge efficiency reached 75.7%; when discharging at 200 mA / g for 300 cycles, the capacity retention rate was 95.7%.

[0051] Example 8

[0052] Micron-sized silicon monoxide with an average particle size of 3 μm was selected and placed in a heat treatment furnace under an argon atmosphere protection. It was heated to 1050 °C and held for 3 h to obtain the crystallized SiO x material. 4 g of SiO x and 36 g of artificial graphite were weighed respectively, 60 mL of absolute ethanol was added, and the mixture was stirred evenly. The mixture was placed in a planetary ball mill with a ball-to-material ratio of 20:1 and ball milled at a speed of 200 rpm for 1 h to obtain the SiO x and artificial graphite mixed slurry. Tin dioxide and sodium alginate were added to deionized water and magnetically stirred for 30 min until the sodium alginate was completely dissolved. The addition amounts of tin dioxide and sodium alginate were 1% and 5% of the weight percentage of the SiO x and artificial graphite mixture, respectively. The mixed solution of tin dioxide and sodium alginate was poured into the SiO x and artificial graphite mixed slurry. The slurry with 100 mesh was screened out, and then deionized water was added to prepare a slurry with a solid-liquid ratio of 1:20. After magnetic stirring for 1 h, spray drying was carried out. The inlet air temperature of the spray drying equipment was set at 200 °C, the outlet air temperature was 140 °C, and the feeding rate was 300 mL / h. The precursor of the (SiO x / G / SnO2)@C composite material passing through 300 mesh was screened out. The precursor was placed in a tubular furnace under an argon atmosphere and heated to 500 °C at a rate of 5 °C / min and held for 6 h to obtain the (SiO x(SiO₂ / G / SnO₂)@C composite anode material. The composite material was assembled into a coin cell to test its electrochemical performance. When charged and discharged at 100 mA / g, the first charge-discharge efficiency reached 74.9%; when discharged at 200 mA / g, it was cycled for 420 weeks, and the capacity retention rate was 80.4%.

[0053] Example 9

[0054] Select micron-sized silicon monoxide with an average particle size of 3 μm and place it in a heat treatment furnace under argon atmosphere protection. Heat it to 1050 °C and hold for 3 h to obtain crystallized SiO x material. Weigh 4 g of SiO x and 36 g of artificial graphite respectively, add 60 mL of absolute ethanol, stir evenly, place the mixture in a planetary ball mill, with a ball-to-material ratio of 20:1, and ball mill at a speed of 200 rpm for 1 h to obtain a mixed slurry of SiO x and artificial graphite. Add tin dioxide and sodium alginate to deionized water and stir magnetically for 30 min until the sodium alginate is completely dissolved. The addition amounts of tin dioxide and sodium alginate are 1% and 10% of the weight percentage of the mixture of SiO x and artificial graphite respectively. Pour the mixed solution of tin dioxide and sodium alginate into the mixed slurry of SiO x and artificial graphite, screen out the slurry with a mesh size of 100, then add deionized water to make a slurry with a solid-liquid ratio of 1:20, stir magnetically for 1 h, and perform spray drying. Set the inlet air temperature of the spray drying equipment to 200 °C, the outlet air temperature to 140 °C, and the feeding rate to 300 mL / h. Screen out the precursor of (SiO x / G / SnO₂)@C composite material. Place the precursor in a tubular furnace under argon atmosphere and heat it to 500 °C at a rate of 5 °C / min, and hold for 4 h to obtain (SiO x / G / SnO₂)@C composite anode material. The composite material was assembled into a coin cell to test its electrochemical performance. When charged and discharged at 100 mA / g, the first charge-discharge efficiency reached 77.5%; when discharged at 200 mA / g, it was cycled for 500 weeks, and the capacity retention rate was 96.0%.

[0055] Example 10

[0056] Select micron-sized silicon monoxide with an average particle size of 3 μm and place it in a heat treatment furnace under argon atmosphere protection. Heat it to 1050 °C and hold for 3 h to obtain crystallized SiO x material. Weigh 4 g of SiO x and 36 g of artificial graphite respectively, add 60 mL of absolute ethanol, stir evenly, place the mixture in a planetary ball mill, with a ball-to-material ratio of 20:1, and ball mill at a speed of 200 rpm for 1 h, then screen out the slurry with a mesh size of 100 to obtain SiO xand artificial graphite mixed slurry. Tin dioxide and sodium alginate were added to deionized water and magnetically stirred for 30 min until the sodium alginate was completely dissolved. The addition amounts of tin dioxide and sodium alginate were 1% and 5% by weight of the mixture of SiO x and artificial graphite, respectively. The mixed solution of tin dioxide and sodium alginate was poured into the mixed slurry of SiO x and artificial graphite. The slurry with a mesh size of 100 was screened out, and then deionized water was added to prepare a slurry with a solid-liquid ratio of 1:20. After magnetic stirring for 1 h, spray drying was carried out. The inlet air temperature of the spray drying equipment was set at 200 °C, the outlet air temperature was 140 °C, and the feeding rate was 300 mL / h. The precursor of (SiO x / G / SnO2)@C composite material passing through 300 meshes was screened out. The precursor was placed in a tubular furnace under an argon atmosphere and heated to 600 °C at a rate of 5 °C / min and held for 2 h to obtain (SiO x / G / SnO2)@C composite anode material. The composite material was assembled into a coin cell to test its electrochemical performance. Charging and discharging were carried out at 100 mA / g, and the first charge-discharge efficiency reached 75.6%; discharging was carried out at 200 mA / g for 500 cycles, and the capacity retention rate was 89.0%.

[0057] Example 11

[0058] Microcrystalline silicon oxide with an average particle size of 3 μm was selected and placed in a heat treatment furnace under an argon atmosphere protection, heated to 1000 °C, and held for 3.5 h to obtain the crystallized SiO x material. 4 g of SiO x and 32 g of artificial graphite were weighed respectively, 56 mL of absolute ethanol was added, and the mixture was stirred evenly. The mixture was placed in a planetary ball mill with a ball-to-material ratio of 20:1 and ball milled at a speed of 150 rpm for 1.5 h to obtain the mixed slurry of SiO x and artificial graphite. Tin dioxide and sodium alginate were added to deionized water and magnetically stirred for 30 min until the sodium alginate was completely dissolved. The addition amounts of tin dioxide and sodium alginate were 0.5% and 5% by weight of the mixture of SiO x and artificial graphite, respectively. The mixed solution of tin dioxide and sodium alginate was poured into the mixed slurry of SiO x and artificial graphite. The slurry with a mesh size of 100 was screened out, and then deionized water was added to prepare a slurry with a solid-liquid ratio of 1:10. After magnetic stirring for 1 h, spray drying was carried out. The inlet air temperature of the spray drying equipment was set at 180 °C, the outlet air temperature was 130 °C, and the feeding rate was 250 mL / h. The precursor of (SiO x / G / SnO2)@C composite material passing through 300 meshes was screened out. The precursor was placed in a tubular furnace under an argon atmosphere and heated to 500 °C at a rate of 5 °C / min and held for 6 h to obtain (SiO x(SiO / G / SnO2)@C composite anode material.

[0059] Example 12

[0060] Select micron-sized silicon monoxide with an average particle size of 3 μm and place it in a heat treatment furnace under argon atmosphere protection. Heat it to 1100 °C and keep it at this temperature for 2.5 h to obtain the crystallized SiO x material. Weigh 4 g of SiO x and 40 g of artificial graphite respectively, add 64 mL of absolute ethanol, stir evenly, place the mixture in a planetary ball mill, with a ball-to-material ratio of 20:1, and ball mill at a speed of 250 rpm for 0.5 h to obtain the mixed slurry of SiO x and artificial graphite. Add tin dioxide and sodium alginate to deionized water and stir magnetically for 30 min until the sodium alginate is completely dissolved. The addition amounts of tin dioxide and sodium alginate are 2% and 20% of the weight percentage of the mixture of SiO x and artificial graphite respectively. Pour the mixed solution of tin dioxide and sodium alginate into the mixed slurry of SiO x and artificial graphite, sieve out the slurry with a mesh size of 100, then add deionized water to make a slurry with a solid-liquid ratio of 1:30, stir magnetically for 1 h, and perform spray drying. Set the inlet air temperature of the spray drying equipment to 220 °C, the outlet air temperature to 150 °C, and the feeding rate to 350 mL / h. Sieve out the precursor of (SiO x / G / SnO2)@C composite material passing through 300 meshes. Place the precursor in a tubular furnace under argon atmosphere, heat it to 600 °C at a rate of 5 °C / min, and keep it at this temperature for 2 h to obtain the (SiO x / G / SnO2)@C composite anode material.

[0061] Comparative Example 1

[0062] Select micron-sized silicon monoxide with an average particle size of 3 μm, sieve out the SiO material passing through 300 meshes, assemble it into a button cell and test its electrochemical performance. Charge and discharge at 100 mA / g, and the initial charge-discharge efficiency reaches 59.9%; discharge at 200 mA / g for 90 cycles, and the capacity retention rate is 8.1%.

[0063] Comparative Example 2

[0064] Select micron-sized silicon monoxide with an average particle size of 3 μm and place it in a heat treatment furnace under argon atmosphere protection. Heat it to 1050 °C and keep it at this temperature for 3 h to obtain the crystallized SiO x material. Weigh 4 g of SiO x36 g of artificial graphite was added, and 60 mL of absolute ethanol was added and stirred evenly. The mixture was placed in a planetary ball mill with a ball-to-material ratio of 20:1 and ball milled at a speed of 200 rpm for 1 h. The slurry with a mesh size of 80 was sieved out. Tin dioxide and glucose were added to 50 mL of deionized water and magnetically stirred for 30 min. The addition amounts of tin dioxide and glucose were 1% and 20% of the weight percentage of the mixture of SiO x and artificial graphite, respectively. The mixed solution of tin dioxide and glucose was poured into the slurry, and then deionized water was added to prepare a slurry with a solid-to-liquid ratio of 1:20, and magnetically stirred for 1 h, followed by spray drying. The inlet air temperature of the spray drying equipment was set at 250 °C, the outlet air temperature was 140 °C, and the feeding rate was 300 mL / h. The precursor of the (SiO x / SnO2 / G)@C composite material passing through 300 meshes was sieved out. The precursor was placed in a tubular furnace under an argon atmosphere and heated to 600 °C at a rate of 5 °C / min and held for 6 h to obtain the (SiO x / SnO2 / G)@C composite anode material. The composite material was assembled into a button battery to test its electrochemical performance. Charging and discharging were carried out at 100 mA / g, and the first charge-discharge efficiency reached 74.9%; discharging was carried out at 200 mA / g for 300 cycles, and the capacity retention rate was 80.4%.

[0065] From Figures 1 to 7 and 11, it can be seen that compared with the silicon oxide-based composite anode material prepared with glucose as the carbon source, when alginic acid or sodium alginate is selected as the carbon source, the obtained material particles have a spherical or quasi-spherical morphology and are mainly composed of flakes with a length of about 10 μm and a thickness of less than 1 μm and small pieces of particles. This composite structure can effectively alleviate the volume effect of the silicon oxide-based composite anode material during the lithium insertion and extraction process, avoid the separation of the active material from the current collector, and stabilize the structure of the electrode, thereby obtaining excellent cycle performance. At the same time, Figure 8 and 9 show that the amorphous carbon coating on the particle surface is thin and uniform, which can reduce the occurrence of more side reactions caused by the direct contact between the active material and the electrolyte, and improve the first charge-discharge efficiency of the composite material.

[0066] The particles of the material obtained in the present invention have a spherical or quasi-spherical morphology, which can make the amorphous carbon coating on the particle surface thin and uniform. At the same time, its specific surface area is also relatively small. In addition, this spherical or quasi-spherical particle morphology and the constructed composite structure contribute to reducing the degree of cracking or pulverization of silicon oxide particles caused by the release of internal stress generated during the lithium insertion and extraction process of the silicon oxide-based composite anode material, thereby avoiding the rapid attenuation of the electrochemical capacity.

[0067] The description of the above embodiments is only used to help understand the technical solution and its core idea of the present invention. It should be noted that for those skilled in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a silicon oxide-based carbon-coated modified composite anode material, characterized in that, It includes the following steps: S1. Mix the crystallized silicon oxide, graphite and absolute ethanol evenly, and perform ball milling treatment to obtain a mixed slurry; S2. Add tin dioxide and alginic acid or sodium alginate to water and stir to completely dissolve the alginic acid or sodium alginate to obtain a mixed solution. The addition amount of tin dioxide is 0.5%-2% of the weight percentage of the mixture of the crystallized silicon oxide and graphite, and the addition amount of alginic acid or sodium alginate is 5%-20% of the weight percentage of the mixture of the crystallized silicon oxide and graphite; S3. Pour the mixed solution obtained in step S2 into the mixed slurry obtained in step S1, screen out the slurry with a mesh size of 80-120, add water to prepare a slurry with a solid-liquid ratio of 1:10-1:30 g / mL, and dry it to obtain a precursor of the silicon oxide-based carbon-coated modified composite anode material; S4. Calcinate the precursor obtained in step S3 at a calcination temperature of 500°C-600°C for 2-6 h to obtain the silicon oxide-based carbon-coated modified composite anode material.

2. The preparation method according to claim 1, wherein The specific steps of the crystallization treatment of the crystallized silicon oxide in step S1 are as follows: The micron-sized silicon monoxide is placed in a heat treatment container under the protection of an argon atmosphere, heated to 1000°C-1100°C, and kept warm for 2.5-3.5 h to obtain the crystallized silicon oxide.

3. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of the crystallized silicon oxide to graphite is 1:8-10, and the mass-volume ratio of the crystallized silicon oxide to absolute ethanol is 1:14-16 g / mL.

4. The preparation method according to claim 3, wherein In step S1, the mass ratio of the crystallized silicon oxide to graphite is 1:9, and the mass-volume ratio of the crystallized silicon oxide to absolute ethanol is 1:15 g / mL.

5. The preparation method according to claim 1, characterized in that, The conditions of the ball milling treatment in step S1 are: the ball-to-material ratio is 20:1, and the ball milling is carried out at a speed of 150-250 rpm for 0.5-1.5 h.

6. The preparation method according to claim 1, characterized in that, In step S2, the addition amount of tin dioxide is 1% of the weight percentage of the mixture of the crystallized silicon oxide and graphite, and the addition amount of alginic acid or sodium alginate is 5%-10% of the weight percentage of the mixture of the crystallized silicon oxide and graphite.

7. The preparation method according to claim 1, characterized in that, The drying in step S3 is spray drying, and the conditions of spray drying are: the inlet air temperature is 180°C-220°C, the outlet air temperature is 130°C-150°C, and the feeding rate is 250-350 mL / h.

8. The silicon oxide-based carbon-coated modified composite anode material obtained by the preparation method according to any one of claims 1-7.

9. A lithium-ion battery, characterized in that, Using the silicon oxide-based carbon-coated modified composite anode material according to claim 8 as the anode material.

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