Changes in the structure and magnetic properties of Li _1.08Mn_1.92O₄ after charge-discharge cycles with a 18650-type cylindrical battery

Charge-discharge cycle performance was examined for the cell Li _1.08Mn_1.92O₄/1 M LiPF₆ in EC:DEC(1:1)/MCMB. The structure and magnetic properties were determined before and after cycling using X-ray diffraction and SQUID measurements. After both 340 cycles at RT and 150 cycles at 55°C, single-phase properties were observed for all samples, but samples in the discharged state showed broadening of X-ray diffraction peaks with decrease in the capacity retention ratio. Decreases in lattice parameter and increases in magnetic susceptibility were clearly observed for samples in the discharged state with decreased capacity retention ratios, while small changes in lattice parameter and magnetic susceptibility were observed for samples in the charged state. It was shown that Li intercalation/de-intercalation becomes difficult with cycling in the shallow charged state. Furthermore, it was suggested that the cell capacity decreases because of the disorder in the Li ion conductive pathway caused by the impaired stability of the samples.