Promoting fast potassium storage in CoSe2/VSe2 non-layered/layered heterostructured nanofibers

Abstract

Constructing heterostructures has been considered 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 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 phase boundaries, which gives rise to significantly enhanced electrochemical performance in potassium-ion batteries with a high reversible capacity of ∼400 mA h g⁻¹ for 200 cycles at 1 A g⁻¹. Density functional theory calculations and molecular dynamics simulations suggest that K diffusion is facilitated at the interface with a more reduced energy barrier, thus achieving high reversible capacity and stable cycling performance.