Carbon coated mesoporous Si anode prepared by a partial magnesiothermic reduction for lithium-ion batteries

Owing to its high theoretical capacity, Si based anode materials have been regarded as the most promising alternative anode materials for lithium-ion batteries. Unfortunately, the commercial application of Si based anode materials has been greatly hindered, due to the large volume change of Si materials during their lithiation/delithiation process, which results in severe pulverization, loss of electrical contact and rapid capacity fading. To address these issues, we reported a partial magnesiothermic reduction method by adjusting the proportion of added Mg powder to convert SiO2 into Si/SiO2 and subsequently to coat such a composite with a carbon layer. After removing unreacted SiO2 using HF, carbon-coated mesoporous Si (p-Si@C) can be obtained. The internal pores could accommodate the volume changes of Si and the carbon coating layer could effectively stabilize the interface during cycling. With this design, the as-prepared p-Si@C shows superior electrochemical performance compared with bare Si. When the p-Si@C electrode evaluated at a rate of 0.5 A g−1, a reversible capacity of 1146 mAh g−1 could still be maintained after 100 cycles.