Preparation method of silicon-carbon composite material and its precursor for lithium ion battery

Abstract

The invention discloses a method for preparing a silicon-carbon composite material for lithium-ion batteries and its precursor. The preparation method of the precursor includes the following steps: after mixing graphite micropowder and nanometer silicon powder with a surfactant, respectively adding into the dispersant, 200-800W power ultrasonic treatment for 30-120min, remove the dispersant, dry to obtain the first powder and the second powder respectively; the first powder and the second powder were respectively dispersed in the pyrolysis In the carbon precursor solution, the 200-800W power ultrasonic stirring is uniform, and the first mixed liquid and the second mixed liquid are obtained, and the first mixed liquid and the second mixed liquid are respectively added to the dispersant, the dispersant is removed, dried, and respectively obtained The third powder and the fourth powder. The preparation method of the silicon-carbon negative electrode material of the present invention solves the problem of Si dispersion in the composite material and the problem of inhibition of Si expansion and pulverization, so that the specific capacity and cycle performance of the negative electrode material can be effectively improved.

Description

technical field [0001] The invention relates to the technical field of lithium-ion batteries, in particular to a method for preparing a silicon-carbon composite material and a precursor thereof for lithium-ion batteries. Background technique [0002] At present, among the anode materials for lithium-ion batteries on the market, the traditional graphite anode still occupies the mainstream position. However, due to the constraints of the structural characteristics of traditional graphite itself, it faces problems such as low theoretical capacity, low platform, and high-current charging and discharging are prone to generate lithium dendrites. Demand for high energy density, long cruising range and high capacity. [0003] Alloy anode materials show great advantages in terms of capacity, among which silicon is the most representative. The theoretical specific capacity of silicon is about 4200mAh / g, 10 times that of traditional graphite. The gradual mass production of high-capac...

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Problems solved by technology

[0004] Although silicon has unparalleled advantages in lithium-ion batteries, it still has a large number of structural and performance drawbacks.

Silicon is very easy to agglomerate, and it is difficult to fully mix and evenly mix with graphite materials. During the charging and discharging process, the resulting alloying and dealloying directly lead to volume effect, and the continuous expansion and contraction make silicon particles serious. Cracking, pulverization, destruction and remodeling of SEI film consume a lot of limited electrolyte and lithium source

[0005] To sum up, in the preparation process of the negative electrode material, the existing method cannot achieve satisfactory results due to improper control, which seriously leads to low first effect, fast cycle attenuation, and the conductivity of silicon itself and ion diffusion. The performance is relatively poor, which limits the specific capacity and rate of the battery, and also brings a series of hidden dangers to the subsequent production of battery products

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