A model lithium-ion system based on the insertion properties of the spinel phase LixMn2O4 (0<x<2)

A model lithium-ion system, based on the manganese oxide, LixMnO4, has been used to study the reversibility of the lithium insertion processes in both the approximate 3 V and 4 V versus Li/Li+ voltage ranges. For the 3 and 4 V ranges, symmetrical cells with the configuration: Li1+xMn2O4/electrolyte/Li1-xMn2O4 were investigated, while asymmetrical cells, LixMn2O4/electrolyte/Li1-xMn2O4, were used to investigate the electrochemical properties of the 4 V range only. The relatively large voltage hysteresis for the symmetrical cell was considered to be due to the concurrent cubic to tetragonal symmetry change occurring for the electrode cycling over the lower voltage range. Impedance measurements confirm that the Li1+xMn2O4 electrode appears to possess significantly inferior electrochemical properties to the electrode covering the higher voltage range. The 4 V range studied in the asymmetrical configuration showed excellent reversibility towards lithium insertion and extraction.