Relaxation Crystal Analysis of LiFePO4 Cathode for Li-Ion Secondary Battery

Lithium iron phosphate has been attracting much attention as the next generation cathode material in secondary Li-ion batteries. We inserted lithium into LiXFePO4 (x approximate to 0) electrochemically and investigated the relaxation process of two-phase after termination of lithium insertion process by means of X-ray Rietveld analysis. It was found that the amount of LiFePO4 decreased and that of FePO4 increased after the termination of lithium insertion. It is considered that LiFePO4 including lithium defects preferable for Li diffusion formed during lithium insertion and that the defective LiFePO4 separated to LiFePO4 without defects and FePO4 at the relaxation process. (C) 2012 The Electrochemical Society. [DOI:10.1149/2.012204esl] All rights reserved.