A new magnesium hydride route to synthesize morphology-controlled Si/rGO nanocomposite towards high-performance lithium storage

Abstract

Si/graphene composites have attracted great attention for application as anode materials of Li-ion batteries owing to their superior capacity and cycle stability. Magnesiothermic reduction of silica is a quite scalable and cost-effective method to synthesize Si/graphene composite. However, this remains a considerable challenge because the intense heat accumulation during the violent exothermic reaction makes it difficult to remain the desired nanostructure of the silica precursor and results in severe aggregation of silicon grains. Herein, we offer a mild and scalable route to efficiently convert silica into morphology-controlled Si nanoparticles by magnesium hydride (MgH2) reduction at a low temperature. The Si nanoparticles that are produced from silica template structure are fine and narrowly distributed, showing the ability to preserve morphology characteristics. The as-synthesized Si/rGO composite exhibits outstanding electrochemical properties, delivering a superior rate capability (513 mA h g−1 at 5 A g−1) and a high reversible capacity of 894 mA h g−1 over 100 cycles at 0.2 A g−1. We believe MgH2 reduction of silica demonstrates its great potential in fabricating Si based anode materials.