The source of first-cycle capacity loss in LiFePO4

The electrochemical extraction of Lithium from solid-state syathesised LiFe PO4 has been studied by neutron powder diffraction. A "coffee-bag" type cel l of configuration < Li-metal lliq. el.l LiFePO4> has been charged to 4.1 V , dismantled in a glovebox, and the composite cathode powder sample scraped from the current collector. Two-phase Rietveld refinement gave a triphylit e (LiFePO4) to heterosite (FePO4) phase-ratio of 18:82. lin the absence of significant absorption effects, this ratio is a true representation of the conversion of LiFePO4 to FeFO4. Possible mechanisms for lithium extraction/ insertion during the first-cycle are discussed. (C) 2001 Elsevier Science B .V. All rights reserved.