Iron(III) phosphates obtained by thermal treatment of the tavorite-type FePO4*H2O material: structures and electrochemical properties in lithium batteries

International audienceThermal treatment of the Tavorite-type material FePO4*H2O leads to the formation of two crystallized iron phosphates, very similar in structure. Their structural description is proposed taking into account results obtained from complementary characterization tools (thermal analyses, diffraction, and spectroscopy). These structures are similar to that of the pristine material FePO4*H2O: iron atoms are distributed between the chains of cornersharing FeO6 octahedra observed in FePO4*H2O and the octahedra from the tunnels previously empty, in good agreement with the formation of a Fe4/3PO4(OH)-type phase. The formation of an extra disordered phase was also proposed. These samples obtained by thermal-treatment of FePO4*H2O also intercalate lithium ions through the reduction of Fe3+ to Fe2+ at an average voltage of ∼2.6 V (vs Li+/Li), with a good cyclability and a reversible capacity around 120 mA h g−1 (>160 mA h g−1 during the first discharge)