Rational construction of VSe2 encapsulated in selenized polyacrylonitrile toward a high-rate capacity and wide temperature tolerance for potassium-ion batteries

Abstract

Metal selenides are considered potential anode materials for potassium-ion batteries (PIBs) because of their decent theoretical capacity and abundant energy reserves. Nevertheless, selenides display relatively huge volumetric dilatation and slow kinetic reactions, resulting in unsatisfactory rate and cycling performances. Herein, a hybrid material, VSe₂/selenized polyacrylonitrile (SePAN), is rationally designed as an anode for PIBs via electrospinning followed by selenidation treatment. SePAN is a dual functional matrix that can efficiently cushion the volumetric variation and provide significant capacity improvement for its chemical bonding effect. Density functional theory (DFT) calculation results demonstrate that the formation of a Se–C bond in SePAN skeletons is beneficial for promoting the charge transfer and the binding interaction between VSe₂ and the SePAN substrate, favoring an improved storage capacity of selenide species. Moreover, VSe₂ anchored on the SePAN substrate plays a crucial role in accelerating the reaction kinetics. As expected, the structural virtue endows VSe₂/SePAN with high reversibility during potassiation/depotassiation, resulting in an excellent rate capacity (188 mA h g⁻¹ at a current density of 5.0 A g⁻¹) and a superior cyclability for K⁺ (481 mA h g⁻¹ at 0.1 A g⁻¹ after 50 cycles) storage at room temperature. Furthermore, the cells still deliver promising electrochemical performance at 0 °C, which supplies a new perspective of the electrode in maximizing the desirable K⁺ storage and wide temperature tolerance.