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

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.