Method for preparing silicon composite cathode material of lithium ion battery

Abstract

The invention discloses a preparation method of a silicon composite anode material for lithium ion batteries and the silicon composite anode material is composed of nc-Si / packing carbon / cracking carbon. Packing carbon powder is adopted as scattered matrix, Li-Si alloy powder is adopted as a reducing agent and a liquid silicon halide or a liquid silane halide is chemically deoxidized by the high-energy ball milling; afterwards, heat treatment and solvent washing are conducted over the deoxidized silicon halide or silane halide under the shielding gas so as to obtain an nc-Si / packing carbon complex, wherein the nc-Si is nanometer porous silicon and nanometer silicon fiber. The nc-Si / packing carbon complex passes through the high-molecular carbon source cladding and heat treatment under the shielding gas to obtain an nc-Si / packing carbon / cracking carbon composite anode material. A charge-discharge test of constant current is conducted at a current density of 0.1 mA / mg to 0.3 mA / mg; the coulombic efficiency of the first circulation of the silicon composite anode material reaches up to 70 percent to 80 percent; and after 30 circulations, the reversible capacity reaches 680 mAh / g and the capacity retention rate reaches more than 95 percent.

Description

technical field [0001] The invention relates to a preparation method of a battery electrode material, in particular to a preparation method of a silicon composite negative electrode material for a lithium ion battery. Background technique [0002] Lithium-ion batteries are being used more and more widely, from micro-batteries required for small electronic devices to power sources for large electric vehicles. The improvement of lithium-ion battery performance mainly depends on the performance of lithium intercalation and extraction electrode materials. At present, mesophase carbon microspheres and modified graphite are widely used as negative electrode materials in commercial lithium-ion batteries, but there are disadvantages such as low theoretical lithium storage capacity (graphite is 372mAh / g), and easy occurrence of organic solvent co-intercalation. The research and application of anode materials for ion batteries has become the key to improving battery performance. Amon...

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Problems solved by technology

[0004] Nature Nanotechnology magazine, No. 3, 2008, page 31 reported that the one-dimensional nanowire-arranged silicon thin-film electrode prepared by the gas-liquid-solid (VLS) template-free technology can approach the theoretical value for the first time, and can be greater than 3000mAh / g. It is reversible under the condition of high capacity, but the preparation cost is high, the reproducibility is difficult to guarantee, and it is also difficult to quickly mass-produce; SolidState Ionics magazine 2007, volume 178, page 1297, reported that metal magnesium was used as a reducing agent, and high-energy ball milling chemical reduction Silicon tetrabromide is prepared to obtain nano-silicon for lithium-ion battery negative electrode materials, but the follow-up treatment process is more complicated, difficult to operate, and the cycle performance of the material is not good; the 1882 page of the 11th issue of Journal of Inorganic Chemistry in 2007 reported that porous silicon / Graphite / carbon composite material, the charge capacity of the material remains at 649.9mAh·g after 200 cycles -1 , but the first charging and discharging efficiency is low, and needs to be further improved and improved

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