Reversible Dual Anionic-Redox Chemistry in NaCrSSe with Fast Charging Capability

Utilizing the anionic redox reaction opens new approaches for the development of new battery cathode materials with extra capacities. Although, it suffers from several obstacles such as voltage hysteresis and sluggish kinetics. In this paper, a new layered chalcogenide-based on dual anionic-redox reaction is reported. The newly designed layered NaCrSSe exhibits the capacity of almost all Na+ intercalation/deintercalation (137 mAh g-1 at 50 mA g-1), and a unique charge/discharge feature with a small polarization of 0.15 V and high energy efficiencies of ~92% in initial cycles. Furthermore, a superior high-rate charge capacity of 115.5mAh g-1 (83.7% retention) was achieved at 27.8 C (4000 mA g-1), which is impressive in all bulk materials for sodium-ion batteries. Systematic characterization studies on structure evolution and DFT calculation show the charge compensation of S and Se anions during cycling. These results will enrich the anion redox chemistry and provide valuable information for developing new anion redox based cathode materials with high capacity and fast kinetics.