Nature of insulating-phase transition and degradation of structure and electrochemical reactivity in an olivine-structured material, LiFePO4.

Synthesis time using microwave irradiation was varied to elucidate the electrochemical degradation mechanism of LiFePO(4) related to the evolution of Fe(2)P. When the amount of Fe(2)P was above a critical level, LiFePO(4) tended to change into an insulating phase, Li(4)P(2)O(7). The correlation between structural analysis and electrochemical analysis attributed the initial degradation of LiFePO(4) to the low electronic conductivity of Li(4)P(2)O(7), whereas the deficiency of P and O evolved by Li(4)P(2)O(7) resulted in the cyclic degradation of LiFePO(4). This kind of correlation between structure and electrochemical performance in intercalation materials will significantly contribute to an explanation of their degradation mechanism for their application.