ИСТИНА

The development of rechargeable batteries for large scale applications (electric vehicles, energy storage systems) requires exploration of new safe, low-cost electrode materials with high specific energy and power. Polyanion-type materials based on phosphates and fluoride-phosphates have received much attention as alternative cathodes for metal-ion batteries due to their high thermal stability and the inductive effect of polyanion-groups. These compounds exhibit rich crystal chemistry: the linking of M(O,F)6 octahedra and PO4 tetrahedra arranges polyhedra networks of different dimensionality with channels and voids occupied by alkali ions, which determine size and metrics of formed cavities. One of the ways towards the enhancement of electrode characteristics is to use multi-electron systems by exploring materials that could cycle more than one alkali ion per active transition metal. In this sense, vanadium and molybdenum containing materials are worthwhile because V and Mo are known to easily adopt a wide range of oxidation states preserving a stable octahedral environment. Structural and electrochemical properties of pyrophosphates AMoP2O7 (A = Li and Na) and the NASICON-structured NaMo2(PO4)3 were investigated. According to the bond valence energy landscapes (BVEL) analysis, the AMoP2O7 structures possess 3D alkali migration pathways with the different activation energies (0.8 eV for LiMoP2O7 and 4.5 eV for NaMoP2O7) proving LiMoP2O7 to exhibit superior electrochemical characteristics compared to NaMoP2O7. This observation was supported by electrochemical measurements which revealed the remarkable electrochemical activity of LiMoP2O7 towards reversible de/intercalation of both Li+ and Na+ ions