Double-particle-size pitch repeatedly-coated shaped graphite silicon-carbon negative electrode material as well as preparation method and application of graphite silicon carbon negative electrode material

Abstract

The invention discloses a preparation method of a double-particle-size pitch repeatedly-coated shaped graphite silicon-carbon negative electrode material, which comprises the following steps: performing CVD vapor deposition on nano silicon on shaped graphite, then coating an outer-layer carbon source with a layer of thickness-controllable mesophase carbon through a thermal polycondensation reaction of pitch, and performing double-layer pitch coating, so that better coating can be realized, the nano silicon is prevented from being exposed and being in direct contact with electrolyte, the technical problems in the prior art are thoroughly solved, and the obtained composite silicon-carbon material is high in first efficiency, good in cycle performance and good in rate capability; and according to the mechanism, the silicon carbon material coated with the asphalt with different particle sizes for multiple times is good in coating layer binding property, good in coating effect, uniform, stable and good in conductivity after carbonization, migration of lithium ions is facilitated, the high-rate discharge capacity is improved, and the cycle performance is remarkably improved.

Description

technical field [0001] The invention relates to the technical field of battery anode materials, in particular to a double-particle-diameter pitch multiple-coated and shaped graphite-silicon-carbon anode material and a preparation method and application thereof. Background technique [0002] Current state-of-the-art lithium-ion batteries are no longer sufficient to meet the growing demands of electric vehicles and large-scale energy batteries. Silicon is considered the most promising candidate to replace graphite. It is the second most abundant element in the earth's crust, is environmentally friendly, and has an ultra-high theoretical capacity (4200 mAh / g). At present, among most silicon-carbon anode materials in the market, hot melt carbonization is the most common way to coat silicon, and single coating is more common, but the disadvantage of single carbon coating is that the carbon layer is thin, which is difficult for silicon to The resulting volume expansion is easy t...

AI Technical Summary

Problems solved by technology

At present, among most silicon-carbon anode materials in the market, hot melt carbonization is the most common way to coat silicon, and single coating is more common, but the disadvantage of single carbon coating is that the carbon layer is thin, which is difficult for silicon to The resulting volume expansion is easy to break the carbon layer, resulting in direct contact between silicon and electrolyte, resulting in capacity loss and safety hazards; in addition, the single carbon coating is not satisfactory for the coating of porous graphite, and for micropores and mesoporous The coating is relatively complete, while the macropores will be exposed. The advantage of multiple coatings is that asphalt with different particle sizes can meet the coating requirements of porous graphite.

[0003] Patent document CN110571424A discloses a method for preparing silicon-carbon materials from nano-silicon shaped graphite through spheroidization equipment. Its nano-silicon is difficult to compound with shaped graphite, and nano-silicon is easy to fall off in the subsequent process, and there is no soft carbon coating such as pitch. Material with poor electrical conductivity

Poor magnification and low first effect

Images