Electrochemical and electrical properties of Nb- And/or C-containing LiFePO4 composites

LiFePO4-based powders prepared through various synthesis conditions are presented. Depending on whether the precursors contain carbon or not, LiFePO4-based composites obtained contain significant amounts of carbon as well. We did not succeed in doping LiFePO4 with Nb and produced, instead, crystalline β-NbOPO4 and/or an amorphous (Nb,Fe,C,O,P) matrix around LiFePO4 particles. The total electrical conductivity is of ∼10-9S.cm-1 at 25°C with an activation energy of ca. 0.65 eV for pure LiFePO4 and LiFePO 4/β-NbOPO4 composite. C-containing LiFePO4 samples, including those that had been tentatively doped with Nb, are much more conductive (up to 1.6.10-1 S.cm-1) with an activation energy ΔE ∼ 0.08 eV. © 2005 Materials Research Society.