Synthesis and electrochemical properties of pitch-based carbon-silicon anode materials
Silicon-based anode materials have the advantages of high specific capacity(3 579 mAh/g)and a wide range of sources,but the large volume effect(～300%)generated during charging and discharging will lead to severe degradation of material properties.In the process of volume expansion,the porous silicon structure can alleviate part of the mechanical stress with the help of internal pores,avoid the cracking and crushing of the material,and thus improve the cycling performance of the silicon-based anode,but the high po-rosity will reduce the lithium storage capacity of the anode material and consume more Li+in the formation of SEI film.In this experi-ment,micron silicon-aluminum alloy was selected as raw material to prepare porous silicon by acid etching,and pitch toluene solubles were used as carbon precursors to impregnate in the pores of porous silicon.By surface coating,a carbon conductive network of"inter-nal and external integration"was formed after high-temperature carbonization.When was used as the anode material of lithium-ion bat-tery,the Si/C composite exhibits a theoretical specific capacity of 1 755.06 mAh/g in the first cycles at a current density of 0.2 A/g,and a stable capacity of 915.19 mAh/g after 150 cycles.In terms of rate performance,with the increase of current density,its specific capacity decreases step by step,and the specific capacity is stable at 563.4 mAh/g at 2.0 A/g,and the capacity retention rate is higher than that of porous silicon PSi.
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