Graphene-wrapped Porous Sb Anodes for Sodium-Ion Batteries by Mechanochemical Compositing and Metallomechanical Reduction of Sb <inf>2</inf> O <inf>3</inf>

Abstract

© 2017 Elsevier Ltd Antimony metal nanoparticles wrapped with a-few-layer graphene coat (Sb@Gn) were fabricated from their oxide form (Sb 2 O 3 ) in a micrometer dimension using a novel two-step ball-milling process. The first mechanochemical process was designed to decrease the particle size of Sb 2 O 3 microparticles for ensuring advantages of nano size and to subsequently coat the Sb 2 O 3 nanoparticles with a-few-layer graphene (Sb 2 O 3 @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, limiting the size of Sb particles during the metallomechanical reduction step. During reduction, oxygen species were transferred from of Sb 2 O 3 through @Gn to Zn along redox transfer pathways rather than direct mass transfer via unsaturated vacancies in the @Gn. the redox transfer involving oxidation of @Gn by O 2− is plausible routes for O 2− transfer in the metallomechanical reduction. The Sb@Gn anode exhibited outstanding capacity retention along charge/discharge cycles and improved rate capability in sodium-ion batteries. The @Gn provided conductive pathways to the Sb core and limited size expansion during sodium-lithium alloying.