Possibility of modification of phosphoolivine by substitution in Li sublattice

Possibility of substitution of Li+ by Al3+, Zr4+ or W6+ and its influence on physicochemical properties of LiFePO4 phosphoolivine was investigated by means of XRD, SEM/EDS, electrical conductivity and Seebeck coefficient measurements. The possible range of solid solution formation in Li1 − 3xAlxFePO4, Li1 − 4xZrxFePO4 and Li1 − 6xWxFePO4 doped phospoolivines was found to be very narrow. Transport properties of the synthesized materials were found to be rather weakly dependent on the assumed chemical composition. No increase of electrical conductivity of the doped samples was observed. The battery performance of selected olivines was tested by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Comparing to Li0.97Al0.01FePO4 and Li0.96Zr0.01FePO4, Li0.94W0.01FePO4 material performed significantly worse, which may be attributed to the presence of a secondary phase and blocking of Li-ion transport paths by dopant.