Nitrogen-Doped Carbon Coated WS 2 Nanosheets as Anode for High-Performance Sodium-Ion Batteries.

Due to the cost-effectiveness of sodium source, sodium-ion batteries (SIBs) have attracted considerable attention. However, SIBs still have some challenges in competing with lithium-ion batteries for practical applications. Particularly, the high rate capability and cycling stability are posing big problems for SIBs. Here, nitrogen-doped carbon-coated WS2 nanosheets (WS2 /NC) were successfully synthesized by a high-temperature solution method, followed by carbonization of polypyrrole. When used as anode electrodes for SIBs, WS2 /NC composite exhibited high-rate capacity at 386 and 238.1 mAh g-1 at 50 and 2,000 mA g-1 , respectively. Furthermore, even after 400 cycle, the composite electrode could still deliver a capacity of ~180.1 mAh g-1 at 1,000 mA g-1 , corresponding to a capacity loss of 0.09% per cycle. The excellent electrochemical performance could be attributed to the synergistic effect of the highly conductive nature of the nitrogen-doped carbon-coating and WS2 nanosheets. Results showed that the WS2 /NC nanosheets are promising electrode materials for SIBs application.