Silicon carbon composite microsphere, and preparation method and application thereof

Abstract

The invention provides a silicon carbon composite microsphere, and a preparation method and application thereof. The method comprises the following steps that (1) silicon dispersion liquid is prepared: 30 to 95 percent of asphalt and 5 to 70 percent of silicon are used as raw materials, and are dispersed in an organic solvent; ball milling is performed; (2) other carbon sources are added into grinding liquid; the ball milling is further performed; (3) the dispersion liquid obtained through the ball milling is added into a high-temperature high-pressure reactor; high-temperature high-pressure reaction is performed under the inert gas protection; (4) products obtained in the third step are subjected to suction filtration to obtain solid particles; (5) the solid particles obtained in the fourth step are subjected to high-temperature carbonizing treatment in inertia non-oxidizing atmosphere to obtain the silicon carbon composite microsphere. The method has the advantages that the asphalt and the micron silicon are used as raw materials; the raw materials are cheap and are easy to obtain; a dispersing agent is nontoxic and can be recovered; the process is simple; the sphericity degree of the obtained material is good; the tap density is high; the specific surface is small; a stable SEI membrane is favorably formed; the circulation stability is excellent.

Description

technical field

[0001] The invention relates to a silicon-carbon composite microsphere negative electrode material, in particular to the application of the silicon-carbon composite microsphere as a high specific capacity lithium ion battery negative electrode material.

[0002] Background technique:

[0003] Lithium-ion batteries have outstanding advantages such as high specific energy, small self-discharge, long service life, green and pollution-free, and have been widely used in portable electronic products and electric vehicles. With the development and progress of society, the further application of lithium-ion batteries urgently needs to increase the energy density, and the development of electrode materials with high specific capacity is one of the effective ways.

[0004] Among the negative electrode materials, carbon materials are mainly commercialized at present, and their theoretical specific capacity is low, about 372mAh g -1 . Silicon has a high theoretical spec...

Examples

Embodiment 1

[0037] Step 1) Preparation of silicon dispersion: Disperse medium-temperature asphalt and silicon powder in polydimethylsiloxane with a mass ratio of 1:1 as the raw material, organic solvent: raw material ratio of 10:1, ball mill slurry viscosity of 500 -1000Pa·s. Use a ball mill for ball milling. The ball milling is carried out under an inert protective nitrogen atmosphere. During the ball milling, zirconia balls are added. The size of the zirconia balls is 0.1mm. The mass ratio of zirconia balls to pitch and silicon is X=10, and X is the mass of zirconia balls. / (asphalt+silicon) quality, 800rpm ball mill for 2 hours;

[0038] Step 2) Add 5 μm graphite flakes to the dispersion, the amount of graphite flakes added is 20% of the mass of raw material medium-temperature pitch and silicon powder, and further ball milling, adding zirconia balls during ball milling, the size of the zirconia balls is 0.3mm, and the size of the zirconia balls is 0.3mm. The mass ratio of balls to pi...

Embodiment 2

[0049] It differs from Example 1 only in that the mass ratio of medium-temperature pitch to silicon powder in step 1) is 2:1, and the carbonization temperature in step 5) is 900°C. .

[0050] The characterization of the silicon-carbon composite material is the same as in Example 1.

[0051] The positive electrode, negative electrode, electrolyte and battery assembly of the battery are the same as in Example 1. The composition of the obtained silicon carbon electrode material and the test results of the battery are listed in Table 1 and Table 2.

Embodiment 3

[0053] It differs from Example 1 only in that the mass ratio of medium-temperature pitch to silicon powder in step 1) is 3:1, and the carbonization temperature in step 5) is 800°C.

[0054] The characterization of the silicon-carbon composite material is the same as in Example 1.

[0055] The positive electrode, negative electrode, electrolyte and battery assembly of the battery are the same as in Example 1. The composition of the obtained silicon carbon electrode material and the test results of the battery are listed in Table 1 and Table 2.

technical field

[0001] The invention relates to a silicon-carbon composite microsphere negative electrode material, in particular to the application of the silicon-carbon composite microsphere as a high specific capacity lithium ion battery negative electrode material.

[0002] Background technique:

[0003] Lithium-ion batteries have outstanding advantages such as high specific energy, small self-discharge, long service life, green and pollution-free, and have been widely used in portable electronic products and electric vehicles. With the development and progress of society, the further application of lithium-ion batteries urgently needs to increase the energy density, and the development of electrode materials with high specific capacity is one of the effective ways.

[0004] Among the negative electrode materials, carbon materials are mainly commercialized at present, and their theoretical specific capacity is low, about 372mAh g -1 . Silicon has a high theoretical spec...

Examples

Embodiment 1

[0037] Step 1) Preparation of silicon dispersion: Disperse medium-temperature asphalt and silicon powder in polydimethylsiloxane with a mass ratio of 1:1 as the raw material, organic solvent: raw material ratio of 10:1, ball mill slurry viscosity of 500 -1000Pa·s. Use a ball mill for ball milling. The ball milling is carried out under an inert protective nitrogen atmosphere. During the ball milling, zirconia balls are added. The size of the zirconia balls is 0.1mm. The mass ratio of zirconia balls to pitch and silicon is X=10, and X is the mass of zirconia balls. / (asphalt+silicon) quality, 800rpm ball mill for 2 hours;

[0038] Step 2) Add 5 μm graphite flakes to the dispersion, the amount of graphite flakes added is 20% of the mass of raw material medium-temperature pitch and silicon powder, and further ball milling, adding zirconia balls during ball milling, the size of the zirconia balls is 0.3mm, and the size of the zirconia balls is 0.3mm. The mass ratio of balls to pi...

Embodiment 2

[0049] It differs from Example 1 only in that the mass ratio of medium-temperature pitch to silicon powder in step 1) is 2:1, and the carbonization temperature in step 5) is 900°C. .

[0050] The characterization of the silicon-carbon composite material is the same as in Example 1.

[0051] The positive electrode, negative electrode, electrolyte and battery assembly of the battery are the same as in Example 1. The composition of the obtained silicon carbon electrode material and the test results of the battery are listed in Table 1 and Table 2.

Embodiment 3

[0053] It differs from Example 1 only in that the mass ratio of medium-temperature pitch to silicon powder in step 1) is 3:1, and the carbonization temperature in step 5) is 800°C.

[0054] The characterization of the silicon-carbon composite material is the same as in Example 1.

[0055] The positive electrode, negative electrode, electrolyte and battery assembly of the battery are the same as in Example 1. The composition of the obtained silicon carbon electrode material and the test results of the battery are listed in Table 1 and Table 2.

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