Promoting Fast Potassium Storage in CoSe2/VSe2 Non-Layered/Layered Heterostructured Nanofibers

Abstract

Constructing heterostructures has been considered as a promising strategy to enhance the electrochemical performance of active materials for energy storage. However, the mechanism for boosting K storage by the heterointerfaces between two phases with different crystal structures is still unclear. Herein, we have designed a heterostructure consisting of non-layered CoSe2 and layered VSe2 decorated on the surface of N-doped carbon nanofibers. Interestingly, the lattice mismatch between these two phases creates a large amount of lattice distortion at the phase boundaries, which gives rise to a significantly enhanced electrochemical performance in potassium-ion battery with high reversible capacity of ~400 mAh g-1 for 200 cycles at 1 A g-1. Density functional theory calculation and molecular dynamics simulations suggest that K diffusion is facilitated at the interface with much reduced energy barrier, thus achieving a high reversible capacity and a stable cycling performance.