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Candidates for high-energy cathodes in potassium-ion batteries (KIBs) are selected by fully screening the inorganic compound structure database. The compounds that satisfy the specific conditions for plausible KIB cathodes are further subjected to theoretical and electrochemical verification, and KVP2O7 is finally pinpointed. KVP2O7 can reversibly desert/insert approximate to 60% of K+ (60 mA h g(-1)) during either chemical or electrochemical oxidation/reduction. KVP2O7 shows an average discharge potential of approximate to 4.2 V versus K/K+, which corresponds to an energy density of 253 W h kg(-1) at 0.25 C. This high energy density characteristic of KVP2O7 is maintained both during fast charge/discharge (C/D) and prolonged redox cycles. The C/D of KVP2O7 is also accompanied by a phase transition between a monoclinic KVP2O7 (P2(1)/c) and a triclinic K1-xVP2O7 (P (1) over bar). The structure interpretation of a new K1-xVP2O7 phase indicates that K+-extraction induces a conformational change of two tetrahedral PO4 units in pyrophosphates. The P (1) over bar phase of K1-xVP2O7 (x approximate to 0.6) remains stable during the C/D process, although it returns to the inborn P2(1)/c phase after thermal treatment. It is believed that the datamining protocol designed for this study will provide a new strategy for materials discovery and that the pinpointed KVP2O7 can be utilized as a reliable KIB cathode.