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.