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

- Antimony nanoparticles wrapped with a-few-layer graphene coat (Sb@Gn) were prepared.
- The Sb@Gn was synthesized by mechanochemical and metallomechnical ball milling process form Sb2O3
- The Sb@Gn anode showed outstanding capacity retention and improved rate capability.
- The graphene layer not only provide conductive pathway but also limit volume expansion.

Antimony metal nanoparticles wrapped with a-few-layer graphene coat (Sb@Gn) were fabricated from their oxide form (Sb2O3) in a micrometer dimension using a novel two-step ball-milling process. The first mechanochemical process was designed to decrease the particle size of Sb2O3 microparticles for ensuring advantages of nano size and to subsequently 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, limiting the size of Sb particles during the metallomechanical reduction step. During reduction, oxygen species were transferred from of Sb2O3 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 O2− is plausible routes for O2− 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.

Sb nanoparticles wrapped with a-few-layer graphene coat (Sb@Gn) were prepared from Sb2O3 by a two-step ball-milling process. The e− and O2− were counter-transferred through graphene layer (@Gn) during zinco-mechanical reduction of Sb2O3 to Sb. The Sb/Zn alloying was completely avoided by the @Gn. Sb@Gn showed excellent performances as anodes for sodium ion batteries.136