Patent ID: 12255323

DETAILED DESCRIPTION OF EMBODIMENTS

In order to more clearly describe the present disclosure for the convenience of understanding the technical solution of the present disclosure, the following text is a further detailed description of the present disclosure. However, the following embodiments are only simple examples of the present disclosure, and are not intended to represent or limit the scope of protection of the claims, and the scope of protection of the present disclosure shall be based on the claims.

The following are typical but not restrictive embodiments of the present disclosure.

Embodiment 1

In this embodiment, the silicon oxide/carbon composite negative electrode material is prepared according to the following method:1) mixing metal silicon and silicon dioxide in a molar ratio of 1.5:1, and under the protection of argon, reacting at a pressure below 20 Pa and a temperature of 1380° C. to produce a silicon oxide gas, and collecting the gas at a pressure below 30 Pa at a low temperature zone collector and then precipitating to obtain the product, i.e., SiOyblocks, y=0.98;2) pulverizing the SiOyblocks obtained in step 1) into powder of about 1 mm by a universal pulverizer, and then pulverizing the product using a planetary ball mill to obtain silicon oxide particles with a median particle size of 6 μm; repeatedly grading (classifying) the obtained silicon oxide particles by a multi-stage air classifier to obtain silicon oxide particles with a specific particle size range, which specifications are as follows: SiOxparticles, wherein x is 1.05, and the D50 of the SiOxparticle is 1.1 μm, the volume of particles with a particle size below 1.0 μm accounts for 55% of all SiOxparticles, and D90=3.9 μm;3) placing the asphalt powder, polyacrylonitrile, the SiOxparticles obtained by grading in step 2) and solvent glycol in a mass ratio of 2.5:2.5:20:75 in a high-speed dispersion reactor, adjusting the rotating speed to 1000 rpm, and ball milling and dispersing for 10 h to obtain a precursor I;4) raising the temperature of the air inlet of a closed spray drying equipment to 230° C. at a rate of 10° C./min, and introducing high-purity argon, then pumping the precursor I through a peristaltic pump, and the air outlet temperature being 150° C., and obtaining a precursor II by collecting materials;5) placing the precursor II in a roller kiln, and introducing a nitrogen protective gas, increasing the temperature to 930.0° C. at 10.0° C./min, keeping the temperature for 5.0 h, and cooling to room temperature naturally to obtain precursor III; and6) screening and demagnetizing to obtain the silicon oxide/carbon composite negative electrode material.

The silicon oxide/carbon composite negative electrode material prepared in the present embodiment is a secondary particle composed of a SiOx/C material. The SiOx/C material comprises SiOxparticles and a carbon layer coated on the surface of the SiOxparticles. The SiOxparticles comprise Si microcrystals, the Si microcrystals are uniformly dispersed in SiOxparticles and SiOxparticles are oriented randomly to each other.

In this embodiment, the following method is used to characterize the structure of the product. A Malvern particle size analyzer (model: MASTERSIZER 2000) is used to test the particle size of the SiOxparticles, the SiOx/C material, and the silicon oxide/carbon composite negative electrode material; a Micromeritics specific surface area tester (Model: ST-08) is used to test the specific surface area and total pore volume, the Beishide compacted density tester (Model: 3H-2000TD) is used to test the true density, and the porosity is calculated according to the results; the Micron (CARVER 4350.22) is used to measure the compacted density, and the X′Pert PRO X-ray diffractometer (XRD) is used to test the half-peak width of Si and calculate the grain size of the Si microcrystals in combination with the Scherrer formula:

Si-size=0.89×0.15406F⁢W⁢H⁢M×0.9⁢7.

The value of x, D50, and D90 of SiOxparticles in the silicon oxide/carbon composite negative electrode material product, and the ratio of the volume of particles with a particle size below 1.0 μm to the total volume of SiOxparticles are the same as the characteristic structure of SiOxparticles in step (2).

The grain size of the Si microcrystal is 3.9 nm, in the silicon oxide/carbon composite negative electrode material, the mass fraction of carbon is 10 wt %, the D50 of the silicon oxide/carbon composite negative electrode material is 4.3 μm, and the compacted density is 1.12 g/cm3, the porosity is 2%, and the specific surface area is 4.13 m2/g. The D50 of SiOx/C material is 3.9 times of that of the SiOx.

The test results of the electrochemical performance of the silicon oxide/carbon composite negative electrode material prepared in this embodiment are shown in Table 1.

FIG.1is a scanning electron microscope image of the silicon oxide/carbon composite negative electrode material prepared in this embodiment; and from the figure, it can be seen that the particles of the silicon oxide/carbon composite negative electrode material prepared in this embodiment are relatively dense.

FIG.2is an XRD graph of the silicon oxide/carbon composite negative electrode material prepared according to the embodiment 1 of the present disclosure; and from the figure, it can be seen that the silicon oxide/carbon composite negative electrode material prepared in this embodiment has diffraction peaks of silicon dioxide and silicon.

FIG.3is a first charging and discharging curve of the silicon oxide/carbon composite negative electrode material prepared according to embodiment 1 of the present disclosure; and from the figure, it can be seen that the silicon oxide/carbon composite negative electrode material prepared in this embodiment has higher capacity and first charge and discharge efficiency.

FIG.4is a rate-cycle performance curve of the silicon oxide/carbon composite negative electrode material prepared according to embodiment 1 of the present disclosure; and from the figure, it can be seen that the silicon oxide/carbon composite negative electrode material prepared in this embodiment has excellent rate performance.

FIG.5is a cycle performance curve of the silicon oxide/carbon composite negative electrode material prepared according to embodiment 1 of the present disclosure; and from the figure, it can be seen that the silicon oxide/carbon composite negative electrode material prepared in this embodiment has excellent cycle performance.

Embodiment 2

In this embodiment, the silicon oxide/carbon composite negative electrode material is prepared according to the following method:1) mixing metal silicon and silicon dioxide in a molar ratio of 1:1, and under the protection of argon, reacting at a pressure below 50 Pa and a temperature of 1380° C. to produce a silicon oxide gas, collecting the gas at a pressure below 30 Pa at a low temperature zone collector and precipitating to obtain a product, i.e., the SiOyblocks, y=1.02;2) pulverizing the silicon oxide blocks obtained in step 1) into powder of about 1 mm by a mechanical pulverizer, and then pulverizing the product using a horizontal ball mill to obtain silicon oxide particles with a median particle size of 7 μm; grading the obtained particles by a multi-stage air classifier to obtain silicon oxide particles with a specific particle size range, which specifications are as follows: SiOxparticles, wherein x is 0.98, and the median D50 of the SiOxparticle is 2.8 μm, the volume of particles with a particle size below 1.0 μm accounts for 38% of all SiOxparticles, and D90=6.7 μm;3) placing polyacrylonitrile, phenolic resin powder and the particles obtained by grading in step 2) in a mass ratio of 10:10:80 in a V-shaped mixer, adjusting the rotating speed to 1000 rpm, and mixing for 1 h to obtain a precursor I;4) placing the precursor I in a horizontal mixing and heating equipment, and introducing high-purity nitrogen at a flow rate of 60 L/min, heating the material by circulating a heat transfer oil and raising the temperature to 650° C. at a heating rate of 8° C./min, and mixing and coating for 120 min to obtain a precursor II;5) placing the precursor II to a box furnace, and introducing a nitrogen protection gas at a flow rate of 60 L/min and raising the temperature to 900.0° C. at 10.0° C./min, keeping the temperature for 4.0 h, and cooling to room temperature naturally and then obtaining a precursor III; and6) screening and demagnetizing to obtain the silicon oxide composite negative electrode material of the lithium-ion battery.

The silicon oxide/carbon composite negative electrode material prepared in the present embodiment is a secondary particle composed of a SiOx/C material. The SiOx/C material comprises SiOxparticles and a carbon layer coated on the surface of the SiOxparticles. The SiOxparticles comprise Si microcrystals, the Si microcrystals are uniformly dispersed in SiOxparticles and SiOxparticles are oriented randomly to each other.

In this embodiment, the method according to embodiment 1 is used to characterize the structure of the product.

The value of x, D50, and D90 of SiOxparticles in the silicon oxide/carbon composite negative electrode material product, and the ratio of the volume of particles with a particle size below 1.0 μm to the total volume of SiOxparticles are the same as the characteristic structure of SiOxparticles in step (2).

The grain size of the Si microcrystal is 3.5 nm, in the silicon oxide/carbon composite negative electrode material, the mass fraction of carbon is 13 wt %, the D50 of the silicon oxide/carbon composite negative electrode material is 6.3 μm, and the compacted density is 1.28 g/cm3, the porosity is 2.1%, and the specific surface area is 3.9 m2/g. The D50 of SiOx/C material is 2.3 times of that of the SiOx.

The test results of the electrochemical performance of the silicon oxide/carbon composite negative electrode material prepared in this embodiment are shown in Table 1.

Embodiment 3

In this embodiment, the silicon oxide/carbon composite negative electrode material is prepared according to the following method:1) mixing metal silicon and silicon dioxide in a molar ratio of 1:3, and under the protection of neon, reacting at a pressure below 100 Pa and a temperature of 1500° C. to produce a silicon oxide gas, collecting the gas at a pressure below 50 Pa on a low temperature zone collector and precipitating to obtain a product, i.e., the SiOyblocks, y=0.91;2) pulverizing the silicon oxide blocks obtained in step 1) into powder of about 1 mm by a mechanical pulverizer, and then pulverizing the product using a horizontal ball mill to obtain silicon oxide particles with a median particle size of 4.3 μm; grading the obtained particles by a multi-stage air classifier to obtain silicon oxide particles with a specific particle size range, which specifications are as follows: SiOxparticles, wherein x is 1.13, and the median D50 of the SiOxparticle is 0.6 μm, the volume of particles with a particle size below 1.0 μm accounts for 60% of all SiOxparticles, and D90=1.6 μm;3) placing polyacrylonitrile, phenolic resin powder and the particles obtained by grading in step 2) in a mass ratio of 20:10:70 in a V-shaped mixer, adjusting the rotating speed to 1000 rpm, and mixing for 1 h to obtain a precursor I;4) placing the precursor I in a horizontal mixing and heating equipment, and introducing high-purity nitrogen at a flow rate of 30 L/min, heating the material by circulating a heat transfer oil and raising the temperature to 900° C. at a heating rate of 10° C./min, and mixing and coating for 100 min to obtain a precursor II;5) placing the precursor II to a box furnace, and introducing a nitrogen protection gas at a flow rate of 30 L/min and raising the temperature to 1100° C. at 15° C./min, keeping the temperature for 2.0 h, and cooling to room temperature naturally and then obtaining a precursor III; and6) screening and demagnetizing to obtain the silicon oxide composite negative electrode material of the lithium-ion battery.

The silicon oxide/carbon composite negative electrode material prepared in the present embodiment is a secondary particle composed of a SiOx/C material. The SiOx/C material comprises SiOxparticles and a carbon layer coated on the surface of the SiOxparticles. The SiOxparticles comprise Si microcrystals, the Si microcrystals are uniformly dispersed in SiOxparticles and SiOxparticles are oriented randomly to each other.

In this embodiment, the method according to embodiment 1 is used to characterize the structure of the product.

The value of x, D50, and D90 of SiOxparticles in the silicon oxide/carbon composite negative electrode material product, and the ratio of the volume of particles with a particle size below 1.0 μm to the total volume of SiOxparticles are the same as the characteristic structure of SiOxparticles in step (2).

The grain size of the Si microcrystal is 9 nm, in the silicon oxide/carbon composite negative electrode material, the mass fraction of carbon is about 15 wt %, the D50 of the silicon oxide/carbon composite negative electrode material is 2.9 μm, and the compacted density is 1.3 g/cm3, the porosity is 9%, and the specific surface area is 8.3 m2/g. The D50 of SiOx/C material is 4.8 times of that of the SiOx.

The test results of the electrochemical performance of the silicon oxide/carbon composite negative electrode material prepared in this embodiment are shown in Table 1.

Embodiment 4

In this embodiment, the silicon oxide/carbon composite negative electrode material is prepared according to the following method:1) mixing metal silicon and silicon dioxide in a molar ratio of 5:1, and under the protection of helium, reacting at a pressure at 0.1 Pa and a temperature of 1000° C. to produce a silicon oxide gas, collecting the gas at a pressure of 0.1 Pa at a low temperature zone collector and precipitating to obtain a product, i.e., the SiOyblocks, y=1.09;2) pulverizing the silicon oxide blocks obtained in step 1) into powder of about 1 mm by a mechanical pulverizer, and then pulverizing the product using a horizontal ball mill to obtain silicon oxide particles with a median particle size of 8 μm; grading the obtained particles by a multi-stage air classifier to obtain silicon oxide particles with a specific particle size range, which specifications are as follows: SiOxparticles, wherein x is 1.0, and the median D50 of the SiOxparticle is 2.9 μm, the volume of particles with a particle size below 1.0 μm accounts for 25% of all SiOxparticles, and D90=9.5 μm;3) placing polyacrylonitrile, phenolic resin powder and the particles obtained by grading in step 2) in a mass ratio of 2.5:2.5:95 in a V-shaped mixer, adjusting the rotating speed to 1000 rpm, and mixing for 1 h to obtain a precursor I;4) placing the precursor I in a horizontal mixing and heating equipment, and introducing high-purity nitrogen at a flow rate of 100 L/min, heating the material by circulating a heat transfer oil and raising the temperature to 200° C. at a heating rate of 0.5° C./min, and mixing and coating for 100 min to obtain a precursor II;5) placing the precursor II to a box furnace, and introducing a nitrogen protection gas at a flow rate of 100 L/min and raising the temperature to 830° C. at 1° C./min, keeping the temperature for 6.0 h, and cooling to room temperature naturally and then obtaining a precursor III; and6) screening and demagnetizing to obtain the silicon oxide composite negative electrode material of the lithium-ion battery.

The silicon oxide/carbon composite negative electrode material prepared in the present embodiment is a secondary particle composed of a SiOx/C material. The SiOx/C material comprises SiOxparticles and a carbon layer coated on the surface of the SiOxparticles. The SiOxparticles comprise Si microcrystals, the Si microcrystals are uniformly dispersed in SiOxparticles and SiOxparticles are oriented randomly to each other.

In this embodiment, the method according to embodiment 1 is used to characterize the structure of the product.

The value of x, D50, and D90 of SiOxparticles in the silicon oxide/carbon composite negative electrode material product, and the ratio of the volume of particles with a particle size below 1.0 μm to the total volume of SiOxparticles are the same as the characteristic structure of SiOxparticles in step (2).

The grain size of the Si microcrystal is 3 nm; in the silicon oxide/carbon composite negative electrode material, the mass fraction of carbon is 3 wt %, the D50 of the silicon oxide/carbon composite negative electrode material is 5.8 μm, and the compacted density is 1.5 g/cm3, the porosity is 2.3%, and the specific surface area is 1.3 m2/g. The D50 of SiOx/C material is 2.0 times of that of the SiOx.

The test results of the electrochemical performance of the silicon oxide/carbon composite negative electrode material prepared in this embodiment are shown in Table 1.

Embodiment 5

In this embodiment, the silicon oxide/carbon composite negative electrode material is prepared by referring to the embodiment 2, while the difference lies in: in step 4), introducing high-purity nitrogen at a flow rate of 10 L/min, and raising the temperature to 1000° C.; and in step 5), introducing a nitrogen protection gas at a flow rate of 10 L/min.

The silicon oxide/carbon composite negative electrode material prepared in the present embodiment is a secondary particle composed of a SiOx/C material. The SiOx/C material comprises SiOxparticles and a carbon layer coated on the surface of the SiOxparticles. The SiOxparticles comprise Si microcrystals, the Si microcrystals are uniformly dispersed in SiOxparticles and SiOxparticles are oriented randomly to each other.

In this embodiment, the method according to embodiment 1 is used to characterize the structure of the product.

Regarding the SiOxparticles in the silicon oxide/carbon composite negative electrode material product, the value of x is 0.98, and the D50 of the SiOxparticle is 2.8 μm, the volume of particles with a particle size below 1.0 μm accounts for 38% of all SiOxparticles, and D90=6.7 μm.

The grain size of the Si microcrystal is 7 nm, in the silicon oxide/carbon composite negative electrode material, the mass fraction of carbon is 13 wt %, the D50 of the silicon oxide/carbon composite negative electrode material is 6.1 μm, and the compacted density is 1.32 g/cm3, the porosity is 2.5%, and the specific surface area is 4.1 m2/g. The D50 of SiOx/C material is 2.2 times of that of the SiOx.

The test results of the electrochemical performance of the silicon oxide/carbon composite negative electrode material prepared in this embodiment are shown in Table 1.

Embodiment 6

In this embodiment, the silicon oxide/carbon composite negative electrode material is prepared by referring to the embodiment 2, while the difference lies in: in step 4), raising the temperature to 950° C.

The silicon oxide/carbon composite negative electrode material prepared in the present embodiment is a secondary particle composed of a SiOx/C material. The SiOx/C material comprises SiOxparticles and a carbon layer coated on the surface of the SiOxparticles. The SiOxparticles comprise Si microcrystals, the Si microcrystals are uniformly dispersed in SiOxparticles and SiOxparticles are oriented randomly to each other.

In this embodiment, the method according to embodiment 1 is used to characterize the structure of the product.

Regarding the SiOxparticles in the silicon oxide/carbon composite negative electrode material product, the value of x is 0.98, and the D50 of the SiOxparticle is 2.8 μm, the volume of particles with a particle size below 1.0 μm accounts for 38% of all SiOxparticles, and D90=6.7 μm.

The grain size of the Si microcrystal is 4 nm, in the silicon oxide/carbon composite negative electrode material, the mass fraction of carbon is 13.2 wt %, the D50 of the silicon oxide/carbon composite negative electrode material is 7.0 μm, and the compacted density is 1.3 g/cm3, the porosity is 2.1%, and the specific surface area is 3.5 m2/g. The D50 of SiOx/C material is 2.5 times of that of the SiOx.

The test results of the electrochemical performance of the silicon oxide/carbon composite negative electrode material prepared in this embodiment are shown in Table 1.

Embodiment 7

In this embodiment, the silicon oxide/carbon composite negative electrode material is prepared by referring to the embodiment 2, while the difference lies in: in step (2), SiOxparticles, wherein x is 0.98, and the D50 of the SiOxparticle is 4.5 μm, the volume of particles with a particle size below 1.0 μm accounts for 29% of all SiOxparticles, and D90=9.8 μm.

The silicon oxide/carbon composite negative electrode material prepared in the present embodiment is a secondary particle composed of a SiOx/C material. The SiOx/C material comprises SiOxparticles and a carbon layer coated on the surface of the SiOxparticles. The SiOxparticles comprise Si microcrystals, the Si microcrystals are uniformly dispersed in SiOxparticles and SiOxparticles are oriented randomly to each other.

In this embodiment, the method according to embodiment 1 is used to characterize the structure of the product.

The value of x, D50, and D90 of SiOxparticles in the silicon oxide/carbon composite negative electrode material product, and the ratio of the volume of particles with a particle size below 1.0 μm to the total volume of SiOxparticles are the same as the characteristic structure of SiOxparticles in step (2).

The grain size of the Si microcrystal is 3.6 nm, in the silicon oxide/carbon composite negative electrode material, the mass fraction of carbon is 13 wt %, the D50 of the silicon oxide/carbon composite negative electrode material is 8.3 μm, and the compacted density is 1.18 g/cm3, the porosity is 2.0%, and the specific surface area is 1.1 m2/g. The D50 of SiOx/C material is 1.8 times of that of the SiOx.

The test results of the electrochemical performance of the silicon oxide/carbon composite negative electrode material prepared in this embodiment are shown in Table 1.

Embodiment 8

In this embodiment, the silicon oxide/carbon composite negative electrode material is prepared by referring to the embodiment 2, while the difference lies in: in step (2), SiOxparticles, wherein x is 0.98, and the D50 of the SiOxparticle is 0.2 μm, the volume of particles with a particle size below 1.0 μm accounts for 58% of all SiOxparticles, and D90=1.7 μm.

The silicon oxide/carbon composite negative electrode material prepared in the present embodiment is a secondary particle composed of a SiOx/C material. The SiOx/C material comprises SiOxparticles and a carbon layer coated on the surface of the SiOxparticles. The SiOxparticles comprise Si microcrystals, the Si microcrystals are uniformly dispersed in SiOxparticles and SiOxparticles are oriented randomly to each other.

In this embodiment, the method according to embodiment 1 is used to characterize the structure of the product.

The value of x, D50, and D90 of SiOxparticles in the silicon oxide/carbon composite negative electrode material product, and the ratio of the volume of particles with a particle size below 1.0 μm to the total volume of SiOxparticles are the same as the characteristic structure of SiOxparticles in step (2).

The grain size of the Si microcrystal is 3.7 nm, in the silicon oxide/carbon composite negative electrode material, the mass fraction of carbon is 13 wt %, the D50 of the silicon oxide/carbon composite negative electrode material is 2.4 μm, and the compacted density is 1.1 g/cm3, the porosity is 5.3%, and the specific surface area is 9.8 m2/g. The D50 of SiOx/C material is 12 times of that of the SiOx.

The test results of the electrochemical performance of the silicon oxide/carbon composite negative electrode material prepared in this embodiment are shown in Table 1.

Embodiment 9

In this embodiment, the silicon oxide/carbon composite negative electrode material is prepared according to the following method:1) mixing metal silicon and silicon dioxide in a molar ratio of 1.8:1, and under the protection of argon, reacting at a pressure below 50 Pa and a temperature of 1380° C. to produce a silicon oxide gas, collecting the gas at a pressure below 30 Pa at a low temperature zone collector and precipitating to obtain a product, i.e., the SiOyblocks, y=1.1, placing the SiOyblocks to a box furnace, and introducing a nitrogen protection gas and raising the temperature to 950.0° C. at 8.0° C./min, keeping the temperature for 4 h, and then taking the same out;2) pulverizing the SiOyblocks obtained in step 1) into powder of about 1.5 mm by a jet crusher, and then pulverizing the product using a planetary ball mill to obtain silicon oxide particles with a D50 of 8 μm; repeatedly grading the obtained particles by a multi-stage air classifier to obtain silicon oxide particles with a specific particle size range, which specifications are as follows: SiOxparticles, wherein the value of x is 0.95, and the D50 of the SiOxparticle is 4.3 μm, the volume of particles with a particle size below 1.0 μm accounts for 13% of all SiOxparticles, and D90=9 μm;3) placing asphalt powder, pplypyrrole and the particles obtained by grading in step 2) in a mass ratio of 15:10:75 in a high-speed fusion machine, adjusting the rotating speed to 1000 rpm, and mixing for 1 h to obtain a precursor I;4) placing the precursor I in an NH-type vacuum kneading equipment, and introducing high-purity nitrogen, raising the temperature to 700° C. at a heating rate of 3° C./min, and continuously stirring, mixing and coating for 180 min to obtain a precursor II;5) placing the precursor II to a roller kiln, and introducing a nitrogen protection gas and raising the temperature to 900.0° C. at 10.0° C./min, keeping the temperature for 4.0 h, and cooling to room temperature naturally and then obtaining a precursor III; and6) screening and demagnetizing to obtain the silicon oxide composite negative electrode material of the lithium-ion battery.

The silicon oxide/carbon composite negative electrode material prepared in the present embodiment is a secondary particle composed of a SiOx/C material. The SiOx/C material comprises SiOxparticles and a carbon layer coated on the surface of the SiOxparticles. The SiOxparticles comprise Si microcrystals, the Si microcrystals are uniformly dispersed in SiOxparticles and SiOxparticles are oriented randomly to each other.

In this embodiment, the method according to embodiment 1 is used to characterize the structure of the product.

The value of x, D50, and D90 of SiOxparticles in the silicon oxide/carbon composite negative electrode material product, and the ratio of the volume of particles with a particle size below 1.0 μm to the total volume of SiOxparticles are the same as the characteristic structure of SiOxparticles in step (2).

The grain size of the Si microcrystal is 3.6 nm, in the silicon oxide/carbon composite negative electrode material, the mass fraction of carbon is 14 wt %, the D50 of the silicon oxide/carbon composite negative electrode material is 7.9 μm, and the compacted density is 1.2 g/cm3, the porosity is 2.0%, and the specific surface area is 1.5 m2/g. The D50 of SiOx/C material is 1.8 times of that of the SiOx.

The test results of the electrochemical performance of the silicon oxide/carbon composite negative electrode material prepared in this embodiment are shown in Table 1.

Embodiment 10

In this embodiment, the silicon oxide/carbon composite negative electrode material is prepared according to the following method:1) mixing metal silicon and silicon dioxide in a molar ratio of 2:1, and under the protection of argon, reacting at a pressure below 20 Pa and a temperature of 1380° C. to produce a silicon oxide gas, collecting the gas at a pressure below 30 Pa at a low temperature zone collector and precipitating to obtain a product, i.e., the SiOyblocks, y=1.05;2) pulverizing the silicon oxide blocks obtained in step 1) into powder of about 1 mm by a ultra-low temperature crusher, and then pulverizing the product using a planetary ball mill to obtain silicon oxide particles with a D50 of 1.5 μm; repeatedly grading the obtained particles by a multi-stage air classifier to obtain silicon oxide particles with a specific particle size range, which specifications are as follows: SiOxparticles, wherein x is 1.15, and the D50 of the SiOxparticle is 0.4 μm, the volume of particles with a particle size below 1.0 μm accounts for 67% of all SiOxparticles, and D90=1.9 μm;3) placing asphalt powder and the particles obtained by grading in step 2) in a mass ratio of 10:90 in a high-energy ball mill, adjusting the rotating speed to 1000 rpm, and mixing for 5 h to obtain a precursor I;4) placing the precursor I to a pusher kiln, and introducing a nitrogen protection gas and raising the temperature to 980.0° C. at 10.0° C./min, keeping the temperature for 5.0 h, and cooling to room temperature naturally and then obtaining a precursor II; and5) screening and demagnetizing to obtain the silicon oxide composite negative electrode material of the lithium-ion battery.

The silicon oxide/carbon composite negative electrode material prepared in the present embodiment is a secondary particle composed of a SiOx/C material. The SiOx/C material comprises SiOxparticles and a carbon layer coated on the surface of the SiOxparticles. The SiOxparticles comprise Si microcrystals, the Si microcrystals are uniformly dispersed in SiOxparticles and SiOxparticles are oriented randomly to each other.

In this embodiment, the method according to embodiment 1 is used to characterize the structure of the product.

The value of x, D50, and D90 of SiOxparticles in the silicon oxide/carbon composite negative electrode material product, and the ratio of the volume of particles with a particle size below 1.0 μm to the total volume of SiOxparticles are the same as the characteristic structure of SiOxparticles in step (2).

The grain size of the Si microcrystal is 4.5 nm, in the silicon oxide/carbon composite negative electrode material, the mass fraction of carbon is 7 wt %, the D50 of the silicon oxide/carbon composite negative electrode material is 1.7 μm, and the compacted density is 1.08 g/cm3, the porosity is 8.3%, and the specific surface area is 9.4 m2/g. The D50 of SiOx/C material is 4.3 times of that of the SiOx.

The test results of the electrochemical performance of the silicon oxide/carbon composite negative electrode material prepared in this embodiment are shown in Table 1.

Comparative Embodiment 1

For the specific preparation method of the present comparative embodiment, reference is made to embodiment 2, and the difference lies in that in steps (1) and (2), the silicon oxide is directly used as the raw material for ball milling and grading; and the silicon oxide/carbon composite negative electrode material prepared according to the present comparative embodiment is a secondary particle composed of a SiOx/C material, the SiOx/C material comprises SiOxparticles and a carbon layer coated on the surface of the SiOxparticles, but the SiOxparticles do not comprise Si microcrystals.

The test results of the electrochemical performance of the silicon oxide/carbon composite negative electrode material prepared in this comparative embodiment are shown in Table 1.

Electrochemical Performance Testing Method:

taking the material prepared in each embodiment and the comparative embodiment as the negative electrode material, mixing it with the binder (CMC+SBR) and the conductive agent in a mass ratio of 92:4:4, adding an appropriate amount of water as a dispersant to prepare a slurry, and coating the slurry on a copper foil, and performing vacuum drying and rolling to prepare a negative electrode sheet; adopting metal lithium sheet as the positive electrode, and using an electrolyte mixed with LiPF6three-component mixed solvent of 1 mol/L according to EC:DMC:EMC=1:1:1 (v/v), and using polypropylene microporous membrane as the separator, assembling a CR2025 type button battery in the MB200B type glovebox of M. Braun Inertgas-Systeme GmbH of Germany filled with argon.

Test of first efficiency of capacity: the charge-discharge test of the button battery is performed on the LAND battery test system of Wuhan Jinnuo Electronics Co., Ltd., and under a normal temperature condition, charging and discharging are conducted at a constant current of 0.1 C, and the charge-discharge voltage is limited to 0.005˜1.5V.

Rate performance test: the charge-discharge test of the button battery is performed on the LAND battery test system of Wuhan Jinnuo Electronics Co., Ltd., under a normal temperature condition, discharging is conducted at a constant current of 1 C, charging is conducted at a constant current of 2 C, and the charge-discharge voltage is limited to 0.005˜1.5V.

Cycle performance test: the charge-discharge test of the button battery is performed on the LAND battery test system of Wuhan Jinnuo Electronics Co., Ltd., and under a normal temperature condition, charging and discharging are conducted at a constant current of 0.1 C, and the charge-discharge voltage is limited to 0.005˜1.5V.

The test results of the electrochemical performance are shown in the following table.

TABLE 1FirstFirst50-cyclereversiblecharge-capacitycapacitydischarge1 C/2 C RateretentionmAh/gefficiency %performance %rate %Embodiment 11600.176.794.093.8Embodiment 2161077.192.392.6Embodiment 3152975.191.893.2Embodiment 41591.276.393.692.1Embodiment 51605.277.092.092.5Embodiment 61603.176.892.292.3Embodiment 71618.677.890.688.4Embodiment 81519.373.184.589.8Embodiment 91625.977.590.587.9Embodiment 101517.872.484.089.5Comparative143460.854.365.2Embodiment 1

Based on the above embodiments and comparative embodiment, it can be seen that the silicon oxide/carbon composite negative electrode material provided in each of embodiments 1˜6 of the present disclosure is in a reasonable structure, and its internal porous structure can absorb a part of the volume expansion to synergistically improve the cycle performance of the material; in addition, the carbon filled among the SiOxparticles can provide good electrical contact among the particles, reduces direct contact between the electrolyte and active substances and thus avoids the cycle degradation caused by loss of electrical contact between the active substances when the particles are powdered, and the SiOxparticles comprise Si microcrystals. Such a structure is also very helpful for improving the performance of the silicon oxide/carbon composite negative electrode material, and the distribution of the particle size of the SiOxparticles is suitable. The capacity and the first coulomb efficiency of the product of embodiments 1˜6 are high, and the rate performance and cycle stability are excellent.

In embodiment 7, the D50 of the SiOxparticles is too large, the granulation effect is poor, and the electrical contact among the particles is bad, and in the charge-discharge process, larger particles easily result in the circumstance that the particles are broken due to the internal stress of lithium intercalation/deintercalation and the active substance is naked, and thus the cycle performance of the product in embodiment 7 is lowered compared with the products in embodiments 1˜6, and the rate performance is also affected disadvantageously.

In embodiment 8, the D50 of the SiOxparticles is too small, so that the material has a relatively large specific surface area and a larger proportion of silicon dioxide may be produced on the surface of the particles, and then loss of battery capacity is rendered when it is used as a negative electrode material, in addition, a too large specific surface area will cause uneven distribution of the carbonaceous binder during the granulation process, the conductivity among particles is weakened, and the capacity play of the material is further affected, and thus the rate performance and the cycle performance of the product in embodiment 8 are lowered compared with those of the products in embodiments 1˜6.

In embodiment 9, the D50 of the SiOxparticles is too large, and the particles with a particle size below 1.0 μm are also too few, which renders more obvious descending of the rate performance and the cycle performance.

In embodiment 10, the D50 of the SiOxparticles is too small, and the particles with a particle size below 1.0 μm are also too many, which renders more secondary reactions and thus lowers the first efficiency of capacity, and the rate performance and the cycle performance are also lowered.

The comparative embodiment 1 does not adopt the solution of the present disclosure, and the SiOxparticles in the product structure do not comprise Si microcrystals. Therefore, the electrochemical performance of the product is lowered.

The applicant declares that the present disclosure uses the above embodiments to illustrate the detailed methods of the present disclosure, but the present disclosure is not limited to the above detailed methods, that is, this does not mean that the present disclosure can only be implemented depending on the above detailed methods.