Rational Design of Tungsten Selenide @ N-Doped Carbon Nanotube for High-Stable Potassium-Ion Batteries.

Potassium-ion batteries (PIBs) are deemed as one of the most promising energy storage systems due to their high energy density and low cost. However, their commercial application is far away from satisfactory because of limited suitable electrode materials. Herein, core-shell structured WSe @N-doped C nanotubes are rationally designed and synthesized via selenizing WO @ polypyrrole for the first time. The large interlayer spacing of WSe can facilitate the intercalation/deintercalation of K . Meanwhile, the core-shell structured nanotube provides favorable interior void space to accommodate the volume expansion of WSe during cycling. Thus, the obtained electrode exhibits superb electrochemical performance with a high capacity of 301.7 mAh g at 100 mA g over 120 cycles, and 122.1 mAh g can remain at 500 mA g even after 1300 cycles. Ex-situ X-ray diffraction analysis reveals the K-ion storage mechanism of WSe @N-doped C includes intercalation and conversion reaction. Density function theory (DFT) calculation demonstrates the reasonable diffusion pathway of K . In addition, the obtained WSe @N-doped C nanotubes have been used as anode material for lithium-ion batteries, which also show good rate performance and high cycle stability. Therefore, this work offers a new methodology for the ration design of new structure electrode materials with long cycle stability.