“…5 Until now, only a few electrode compounds have been reported for K storage, including organic materials, transition metal oxides and carbides, and two-dimensional (2D) transition metal nitride materials. [6][7][8][9] Chong et al synthesized Ni-substituted Prussian blue analogues as cathode materials for KIBs, which achieved a high energy density 306.0 W h kg À1 with a satisfactory retention rate of 96.3% after 200 cycles at 10 mA g À1 . 10 Ge et al based on first principles calculations found that ternary transition metal chalcogenides Ti 2 PX 2 (X = S, Se, Te) exhibited potential performance for KIBs, whose storage capacity is 281 mA h g À1 and diffusion barrier energy is 0.07 Ev.…”