Abstract
A solid-state reaction to synthesize a lithium multi-transition metal phosphate LiCo 1/3 Mn 1/3 Fe 1/3 PO 4 is used in this work, which has a high voltage of 3.72 V and capacity of 140 mAh g -1 at a 0.05 C rate. From the in-situ XRD analysis, LiCo 1/3 Mn 1/3 Fe 1/3 PO 4 has shown a high stability during cell charge/discharge, even operating at 5 V, which is due to the stable olivine structure. Although all the transition metals Co 2+ , Mn 2+ and Fe 2+ are at the same 4c site of the LiCo 1/3 Mn 1/3 Fe 1/3 PO 4 structure, they seem to have different chemical activities and reflect on the electrochemical performance. The capacity contributed by the Co 2+ /Co 3+ redox couple is only 20 mAh g -1 , which is less than that of the Fe 2+ /Fe 3+ and Mn 2+ /Mn 3+ redox couples. This is because of the fact that the diffusivity of lithium ion for the Co 2+ /Co 3+ redox couple is 10 -16 cm 2 s -1 which is one order less than that of the Fe 2+ /Fe 3+ and Mn 2+ /Mn 3+ redox couples in LiCo 1/3 Mn 1/3 Fe 1/3 PO 4 . Crown Copyright © 2010.