Enhanced rate capability of S@Co3O4 microsphere wrapped by rGO for cathodes of lithium-sulfur batteries

Abstract

S@Co3O4/rGO (SCG) composite was synthesized via a readily solvothermal method and subsequent thermal treatment for cathodes of lithium-sulfur (Li-S) batteries, in which Co3O4 hollow microsphere used as a sulfur host has been initially wrapped by conductive reduced graphene oxide (rGO) network. Benefited from polar Co-S bond forming strong adsorption with polysulfides and hollow structure providing void spaces for volumetric expansion, Co3O4 additive effectively alleviates such issues as shuttle effect and electrode pulverization/failure. Moreover, rGO layer covering onto surface of Co3O4 microsphere further increases electrical conductivity and structural stability of electrode. As a result, SCG composite exhibits superior electrochemical performances with a high specific capacity of 1131.6 mAh g−1 at 0.2 C, and an enhanced rate capability tolerating a high current density of up to 5 C. The design strategy on composition and structure of cathode in this work will provide a novel route for achieving high-energy Li-S batteries.