Probing electrochemical reactivity in an Sb2S3-containing potassium-ion battery anode: observation of an increased capacity

Abstract

Potassium-ion batteries are attracting considerable attention as a viable type of high voltage battery. Among available anode materials, composites containing Sb₂S₃ are some of the most interesting high capacity candidates. A nanostructured Sb₂S₃–reduced graphene oxide composite anode material is evaluated in this study and compared with a structurally similar SnS₂–reduced graphene oxide material reported previously by this team. The behaviour of the Sb₂S₃-based electrodes is assessed in both 1 M KPF₆ in ethylene carbonate–diethyl carbonate and 1 M KPF₆ in 1,2-dimethoxyethane electrolytes. Depotassiation capacities in excess of 650 mA h g⁻¹ are recorded for the composite electrodes, superior not only to SnS₂-based electrodes but also to all previously reported Sb₂S₃-containing electrode materials for potassium-ion batteries. In order to establish insights into the reaction mechanism of the Sb₂S₃ phase with potassium, post-cycling X-ray diffraction and in situ transmission electron microscopy are utilised. The recorded data suggest the presence of antimony alloys and potassium polysulphides as reaction products and intermediates; a possible conversion-alloying reaction mechanism is discussed. The results indicate that a capacity higher than previously believed is achievable in the Sb₂S₃ active component of potassium-ion battery electrodes.