Decoration of hollow nitrogen-doped carbon nanofibers with tapered rod-shaped NiCo2S4 as a 3D structural high-rate and long-lifespan self-supported anode material for potassium-ion batteries

Abstract Although potassium ion batteries (KIBs) have been invested in development as an emerging low-cost, high-content energy storage system at present. However, the large ionic radius of K+-ion lead to poor rate performance and low cycle life. Therefore, it is extremely necessary to develop a new type of potassium storage material. Here, we report a novel three-dimensional (3D) structural self-supported anode composite material for KIBs, which consists of tapered rod-shaped nanomaterial NiCo2S4 and nitrogen-doped hollow carbon nanofibers (NiCo2S4@N-HCNFs). Then, the composite material was obtained by high temperature carbonization and hydrothermal reaction process. The prepared electrode materials were used to assemble K half-cells for electrochemical performance measurement, achieved the capacity of 263.7 mAh g−1 after 200 cycles at a current density of 100 mA g−1 and an outstanding stability of retaining 134.3 mAh g−1 at 3200 mA g−1 after 600 cycles. It has superior performance and convenient synthesis process over other reported metal sulfides self-supported anode materials for KIBs so far. The novel structure not only shorten the ion transmission distance, but also increase the contact area with the electrolyte. It can improve electrochemical performance effectively.