Constructing multi-dimensional migration channel by nickel-doped WS2 composite: High speed sodium and potassium ion storage kinetics in WS2 nanosheets

Tungsten disulfide (WS2) exhibits high theoretical capacity (433 mAh g−1) and unique layered structure, which is a potential anode material for sodium ion batteries. The sodium ions are diffused mainly along the (0 0 2) crystal plane of WS2, showing unsatisfactory Na+ diffusion kinetics leads to poor rate capacity. It is still a challenge to break through the two-dimensional diffusion of Na+ and to realize the rapid multi-dimensional transport of more Na+. In this work, the multi-dimensional migration channel structure constructed by Nickel-doped WS2 composite, which exhibits penetrable interlayer defects on the (0 0 2) crystal plane of WS2 nanosheets. On one hand, the interlayer defects as active sites can absorb more Na+, showing higher sodium storage capacity. On the other hand, the DFT results show that these interlayer defect structures can greatly reduce the diffusion barrier for Na+ migration along the vertical direction of (0 0 2) crystal plane of WS2. The structure expands the diffusion of Na+ from two-dimensional plane to multi-dimensional, which enables high speed sodium and potassium ion storage kinetics. This work provides a new idea for improving ion diffusion and accelerating electrochemical reaction kinetics of other transition metal layered compounds.