Graphene-wrapped Porous Sb Anodes for Rechargeable Sodium-Ion Batteries by Mechanochemical Compositing and Metallomechanical Reduction of Sb2O3

Antimony metal nanoparticles wrapped with a-few-layer graphene coat (Sb@Gn) were prepared from their oxide form (Sb2O3) in a micrometer dimension by a novel two-step ball-milling process. The first mechanochemical process was designed to decrease the particle size of Sb2O3 microparticles for advantage of nano size and then coat the Sb2O3 nanoparticles with a-few-layer graphene (Sb2O3@Gn). The second metallomechanical ball milling process reduced the oxide to its metal form (Sb@Gn) by the help of Zn as a metallic reductant. The graphene layer (@Gn) blocked the alloying reaction between Sb and Zn and limited the size of Sb particles during the metallomechanical reduction step. The redox reaction of Sb2O3@Gn was presented via oxygen direct transfer and the redox transfer though two type vacancies in graphene layer. The Sb@Gn anode showed outstanding capacity retention along cycles and improved rate capability in sodium ion batteries. The @Gn played roles of providing conductive pathways to Sb core and limiting the size expansion during sodium alloying step