Fast K-Ion Storage Enabled by N, O Co-Doping and Atomic-Interface Engineering on WS2

WS is a promising anode for potassium-ion batteries due to its high theoretical capacity and unique layered structure. However, the intercalation-dominated K storage, large K diffusion barrier energy, and poor intrinsic electrical conductivity limit its practical application. Based on these problems, a synergetic effect of N, O codoping and atomic-interface engineering is performed for WS, in which interoverlapped superstructure of unilamellar N, O co-doped WS and C (NO-WS-C) is designed to maximize the atomic-interface contact area between WS and carbon. The unique NO-WS-C enables the occurrence of the conversion reaction between WS and K, which produces vast ultrasmall W nanoparticles (∼2 nm), resulting in the construction of a space charge zone on the W surface to enhance K storage. Furthermore, density functional theory calculations indicate that the unique NO-WS-C possesses a low bandgap (0 eV) and K diffusion energy barrier (0.2 eV) to boost K transport. Consequently, an ultrafast K-ion storage capability (107.8 mAh/g at 20C), and an ultralong cycling life over 5000 cycles at 5C with an extremely low capacity loss per cycle of 0.007 % are obtained, which are the best among previously reported WS-based anodes.