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MoSe2/N‐Doped Carbon as Anodes for Potassium‐Ion Batteries

Potassium‐ion batteries (PIBs) have attracted considerable attention due to the low redox potential, low price, and abundance, in comparison to lithium and sodium. Herein, a novel potassium MoSe2/N‐C battery with a new electrolyte, 1 m potassium bis(fluoro‐slufonyl)imide in ethyl methyl carbonate, is reported. The MoSe2/N‐C composite, which consists of carbon‐coated MoSe2 nanosheets, is synthesized through solvothermal and annealing method. As an anode material for PIBs, it exhibits an outstanding rate performance and long cycling stability. Meanwhile, a reversible capacity of 258.02 mA h g−1 is achieved after 300 cycles at 100 mA g−1, obtaining a Coulombic efficiency close to 100%. Even at a high current density, it can maintain 218 and 197 mA h g−1 at 500 and 1000 mA g−1, respectively. The charge/discharge mechanism of MoSe2/N‐C as the anode material for PIBs is investigated. These results reveal that the insertion and the extraction of K+ will lead to a phase transition of MoSe2. During the charge process, a part of the MoSe2 will transform to Mo15Se19 and the major final discharge product is K5Se3.