ИСТИНА

The success of Li-ion batteries for large scale applications (electric vehicles, stationary energy storage devices) relies heavily on the development of new cathode materials with high power and energy density along with long cycle life. In the search for high-energy cathode materials for metal-ion batteries we have explored the A2MPO4F (A=Li, Na; M=Co, Mn, Fe) fluoride-phosphates with 3D and layered structures. The fluoride-phosphates were prepared through different synthetic routes (solid-state reactions, cryochemistry, ion-exchange) depending on the chemistry of transition metal. Combination of synchrotron X-ray/neutron diffraction and electron microscopy were applied to present a thorough structural characterization; electrochemical activity of fluoride-phosphate materials was tested in Li- and Na-cells. Electrochemical measurements revealed that lithium de/intercalation in 3D-Li2MPO4F system occurs in the solid solution regime with average discharge voltages ranging from 3.4 V (vs. Li/Li+) for Li2FePO4F to 4.8 V for the Co-counterpart; and the redox potential might be tuned by appropriate substitution on the transition metal site. Electrochemical properties of 3D fluoride-phosphate family will be compared with those of layered compounds; and impact of structure peculiarities (dimensionality, conjugation of transition metal octahedra) will be discussed.