Structural investigation and electrochemical behaviour of Li[NixLi(1/3−2x/3)Mn(2/3−x/3)]O2 compounds by a simple combustion method

Li[NixLi(1/3−2x/3)Mn(2/3−x/3)]O2 (x=0.17, 0.25, 0.33, 0.5) compounds have been prepared by a simple combustion method. Compared with the mixed hydroxide or sol–gel method, the combustion method is very simple, and will therefore reduce the manufacturing cost of the cathode material. The structural and electrochemical properties of the samples were investigated using X-ray diffraction spectroscopy (XRD) and the galvanostatic charge–discharge method. Rietvelt analysis of the XRD patterns shows that these compounds can be classified as α-NaFeO2 structure type.Compounds with high Ni content (x=0.25–0.5 in Li[NixLi(1/3−2x/3)Mn(2/3−x/3)]O2) appear to be composed of two phases, namely Ni-rich and Ni-deficient phases with the same α-NaFeO2 structure. By contrast, the Li[Ni0.17Li0.22Mn0.61]O2 compound with a low Ni content has good phase integrity with only a single phase. The initial charge–discharge and irreversible capacity become larger as x in Li[NixLi(1/3−2x/3)Mn(2/3−x/3)]O2 decreases. The Li[Ni0.50Mn0.50]O2 compound has a relatively low initial discharge capacity of 200 mAh g−1 and exhibits a large loss in capacity during cycling. On the other hand, Li[Ni0.17Li0.22Mn0.61]O2 and Li[Ni0.25Li0.17Mn0.58]O2 compounds give high initial discharge capacities of over 245 mAh g−1 and a stable cycle performance in the voltage range 4.8–2.0 V. The XRD and electrochemical results suggest that the simple combustion method is more appropriate for synthesizing Li[NixLi(1/3−2x/3)Mn(2/3−x/3)]O2 compounds with low Ni content.