Li-storage in LiFe1/4Mn1/4Co1/4Ni1/4PO4 solid solution

Olivine structured LiFe1/4Mn1/4Co1/4Ni1/4PO4 in pure solid solution single phase was obtained using solid-state reaction. For the carbon-coated material, in a voltage range of 3.0-5.1 V (vs. Li/Li+), three voltage plateaus were observed clearly in both galvanostatic discharging and galvanostatic intermittent titration technique (GITT) curves. These three plateaus are corresponding to Co3+/Co2+, Mn3+/Mn2+ and Fe3+/Fe2+ redox couples. No definite plateau can be assigned to Ni3+/Ni2+ redox couple in this voltage range. The overpotentials show the maximum when the redox reaction shifts from one redox couple to another couple. The apparent chemical diffusion coefficients of lithium ((D) over bar (Li)) are in the same order of magnitude 10(-15) cm(2) s(-1) for all transition reactions. (C) 2008 Elsevier B.V. All rights reserved.