Few-Layered Tin Sulfide Nanosheets Supported on Reduced Graphene Oxide as a High-Performance Anode for Potassium-Ion Batteries.

Anodes involving conversion and alloying reaction mechanisms are attractive for potassium-ion batteries (PIBs) due to their high theoretical capacities. However, serious volume change and metal aggregation upon potassiation/depotassiation usually cause poor electrochemical performance. Herein, few-layered SnS nanosheets supported on reduced graphene oxide (SnS @rGO) are fabricated and investigated as anode material for PIBs, showing high specific capacity (448 mAh g at 0.05 A g ), high rate capability (247 mAh g at 1 A g ), and improved cycle performance (73% capacity retention after 300 cycles). In this composite electrode, SnS nanosheets undergo sequential conversion (SnS to Sn) and alloying (Sn to K Sn , KSn) reactions during potassiation/depotassiation, giving rise to a high specific capacity. Meanwhile, the hybrid ultrathin nanosheets enable fast K storage kinetics and excellent structure integrity because of fast electron/ionic transportation, surface capacitive-dominated charge storage mechanism, and effective accommodation for volume variation. This work demonstrates that K storage performance of alloy and conversion-based anodes can be remarkably promoted by subtle structure engineering.