ИСТИНА

As soon as K+ ions can be readily de/intercalated into graphite and hard carbons, main efforts are focused now on the cathode part. Searching for new cathode materials largely involves polyanion materials such as phosphates. Recently it was shown that potassium vanadium fluoride-phosphate, KVPO4F, adopting the KTP structure, demonstrates a reversible K+ intercalation at an average potential of ca 4.0 V vs K/K+ revealing rapid kinetics and fast diffusion (DK = 10-10 – 10-12 cm2/s). At the same moment, a significant part of electrochemical capacity was found to deliver at extremely high potentials around 4.6 V vs K/K+ accompanied by severe electrolyte decomposition and vanadium dissolution. Decreasing the working potential is usually possible through substitution in metal or anion sublattices. In this work, we synthesized and investigated potassium vanadyl phosphate KVPO4O homeotypic to KVPO4F and compared the electrochemical performance of KVPO4X (X = O, F) cathode materials.