Fabrication of CoSe@NC nanocubes for high performance potassium ion batteries.

Abstract Potassium-ion batteries (PIBs) are considered as a promising candidate for large-scale energy storage. While exploring suitable anode materials are of vital need for the practical applications of PIBs. Herein, a well-designed heterostructured anode material CoSe nanocubes wrapped by N-doped carbon (CoSe@NC), has been successfully fabricated by simple annealing ZIF-67 nanocubes followed by in-situ selenization process. It is noted that ZIF-67 nanocubes are used as an effective template for the formation of porous structure, which can facilitate the construction of heterogeneous interface between CoSe and N-doped carbon (NC), effectively stabilizing CoSe with conversion reaction product Co0, increasing the diffusion mobility of electrons and K+-ions, and alleviating huge volume change. As expected, the heterostructured CoSe@NC nanocubes exhibit excellent K+-storage performance, which can display a rather high initial charge capacity (388.7 mAh g−1 at 0.1 A g−1 with the columbic efficiency of 70%), superior cyclic stability (309.6 mA h g−1 after 500 cycles at 2 A g−1), and exceptional rate capability (365.9 mAh g−1 at 2 A g−1). In terms of the low-cost and facile production approach for CoSe@NC, which makes the CoSe@NC a promising anode material for PIBs.