Phosphate materials for cathodes in lithium ion secondary batteries

Olivine phosphates of general formula LiMPO4 (M = Fe, Co, Ni) were prepared and characterised in order to evaluate new potential cathode materials for secondary lithium ion batteries. The synthesis was performed by soft chemistry methods to avoid problematical and energetic expensive solid state reactions. In all the compounds no secondary phase was detected and the powder morphology was found to be suitable for cathode layers preparation. Only LiFePO4 and LiCoPO4 showed reversible lithium deintercalation-intercalation at 3.5 and 4.8 V vs. Li+/Li, respectively. The LiCoPO4 high potential makes this compound very attractive for high energy batteries, but unfortunately its lifetime appears to be too poor.