Superior Potassium Ion Storage via Vertical MoS2 "Nano-Rose" with Expanded Interlayers on Graphene

Abstract

Potassium has its unique advantages over lithium or sodium as a charge carrier in rechargeable batteries. However, progresses in K-ion battery (KIB) chemistry have so far been hindered by lacking suitable electrode materials to host the relatively large K⁺ ions compared to its Li⁺ and Na⁺ counterparts. Herein, molybdenum disulfide (MoS₂ ) "roses" grown on reduced graphene oxide sheets (MoS₂ @rGO) are synthesized via a two-step solvothermal route. The as-synthesized MoS₂ @rGO composite, with expanded interlayer spacing of MoS₂ , chemically bonded between MoS₂ and rGO, and a unique nano-architecture, displays the one of the best electrochemical performances to date as an anode material for nonaqueous KIBs. More importantly, a combined K⁺ storage mechanism of intercalation and conversion reaction is also revealed. The findings presented indicate the enormous potential of layered metal dichalcogenides as advanced electrode materials for high-performance KIBs and also provide new insights and understanding of K⁺ storage mechanism.

Keywords: K-ion batteries; MoS2; anodes; composites; graphene.