Electrochemical lithium storage performance of Si/C based anode materials prepared by mechanical alloying

摘要

Si is valuable anode materials of lithium ion batteries because of its high capacity. However, the poor cycling performance limits its application. In this paper, two kinds of carbon, graphite (Gr) and carbon black (CB), were mixed with Si by mechanical alloying (MA) to improve cycling and conductive performance of Si. After MA, the average Si particle size decreased. Mechanical alloying cannot induce the complete amorphisation of Si. Carbon did not react with Si during MA despite the carbon source. Mechanical alloying can increase lithium storage property of Si. Milled Si showed the rapidly fading characteristic which is similar to the original Si. Charge capacity of Si/CB and Si/Gr composites decreased with slowing speed compared with pure Si with the increasing cycle number. Mechanical alloying or doping cannot change lithiation and de-lithiation potentials of Si. Mechanical alloying promotes diffusion of Li in Si. The diffusion coefficient of Li in MA Si is two orders higher than that of the original Si.