A New Candidate in Polyanionic Compounds for Potassium Ion Battery Anode: MXene Derived Carbon Coated π-Ti₂O(PO₄)₂

Intercalation-type reaction that occurs in polyanion materials is considered to be a facile way to counter the mismatched relationship between the large K⁺ and compact host structure for potassium ion batteries (PIBs). However, the large “dead” weight and poor conductivity introduced by the polyanion framework severely limit the electrochemical performance of polyanion anodes. Herein, a new rigid K⁺ host of 1D π-Ti₂O(PO₄)₂ with carbon-coated (TOP@C) is simply synthesized through a simple Ti₃C₂T_x-derived method. The density functional theory (DFT) calculations and experimental results show that the potassium storage properties are unquestionably improved by the small cell volume change during cycling, the intercalation pseudo-capacitance energy storage mechanism, and the large K-storage tunnels with lower migration energy (0.23 eV) of TOP@C anode (134.5 mAh g^-1 after 2000 cycles at 1.0 A g^-1). The TOP@C//PTCDA full batteries, which clearly illustrate their promising application in advanced PIBs, successfully achieved a high energy density of 119.4 Wh kg^-1 and a power density up to 632.8 W kg^-1 with regard to the total mass of TOP@C and PTCDA.