Hierarchically interconnected WS2/graphene foam for high-performance sodium storage

Sodium-ion batteries (SIBs), as the promising energy storage systems alternative to lithium-ion batteries (LIBs), are given increasing expectations and highly valued owing to the abundant reserves and low cost of sodium-containing minerals. However, further applications are still limited by the lack of anode material with high capacity and long cycle life. Herein, highly permeable foam-like tungsten disulfide/reduced graphene oxide composites with 3D interconnected hierarchical porous structure (3DHP WS2/RGO) are designed and studied as anode materials in SIBs. Remarkably improved battery performance is obtained, including high reversible capacity (419 mA h g−1 at 100 mA g−1), excellent cycling stability (1000 cycles) and superior rate capability (360 mA h g−1 at 2 A g−1). Electrochemical characterizations reveal that the high pseudocapacitive behavior dominates the fast ions/charge reaction kinetics, and the reversible conversion between Na2S generated in the first discharge process and S as evidenced by various advanced characterization techniques dominates sodium storage. The exceptional performance exhibited by 3DHP WS2/RGO composite sheds new light on the development of two-dimensional transition metal dichalcogenides-based materials for next-generation energy storage systems.