Research Update: Retardation and acceleration of phase separation evaluated from observation of imbalance between structure and valence in LiFePO4/FePO4electrode

Abstract

LiFePO4is a potential positive electrode material for lithium ion batteries. We have experimentally observed an imbalance between the valence change of Fe ions and the structure change from the LiFePO4phase to the FePO4phase during delithiation by simultaneous in situ XRD and XANES measurements in an LiFePO4/FePO4electrode. The ratio of structure change to valence change clearly indicates that the phase separation from LiFePO4to FePO4is suppressed at the beginning of delithiation, while it is accelerated at the latter stage, which is due to the coherent strain caused by the lattice misfit between the two phases. © 2014 Author(s).