Review of LiFePO4 Phase Transition Mechanisms and New Observations from X-ray Absorption Spectroscopy

摘要: The high rate capability and reversibility of lithium iron phosphate battery cathodes is attributed to the highly reversible transition between its LiFePO4 FePO4 phases. Conflicting models exist for phase mechanism, such as shrinking or expanding core models, surface reaction limited model, single-phase kinetic model. A literature review suggests that subscribed theories depend upon experimental methods also geometry size particles. We study electronic structure disorder during two-phase commercial oval-shaped particles using in situ XAS (X-ray absorption spectroscopy) with �μ XANES near edge structure) difference technique along traditional EXAFS (extended X-ray fine track Debye-Waller (DW) factor. magnitude, |�μ|, tracks changes which does not follow a synchronous path content. magnitude DW shows degree structural reaches maximum middle charge/discharge cycle. combined |�μ| results LiFePO4/FePO4 occurs through “collective mosaic” an unrelaxed “sequential”