WS2 anode in Na and K-ion battery: Effect of upper cut-off potential on electrochemical performance

Abstract

Transition metal dichalcogenides (TMDs)-based layered anode materials are gaining attention because of their large interlayer spacing to host Na- and K-ions. However, the capacity retention and coulombic efficiency are major obstacles for such rechargeable K-ion battery anodes. Beside, understanding operating potential window employed during charge-discharge processes plays important role on the electrochemical performance. In this work, the impact of operating potential window of WS2 electrodes during charge-discharge is investigated in Na and K-ion battery. WS2 nano-plates are synthesized using one step solid-state reaction under autogenic pressure at elevated temperature (RAPET) method. The upper cut-off potential is restricted to 2.0, 2.5, and 3.0 V to understand the stability of the electrode. The restriction of upper cut-off potential at 2.0 V, results into the capacity retention of 73% (180 mAh g−1) and 75% (250 mAh g−1) in Potassium-ion and Sodium-ion batteries at the end of 50 cycles. Further, kinetic analysis reveals that the K-ion storage in WS2 electrode is diffusion dominated due to intercalation of K-ion into host lattice, and Na-ion storage is pseudo-capacitive in nature.