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)]O-2 (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 alpha-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)]O-2) appear to be composed of two phases, namely Ni-rich and Ni-deficient phases with the same alpha-NaFeO2 structure. By contrast, the Li[Ni0.17Li0.22Mn0.61]O-2 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)]O-2 decreases. The Li[Ni0.50Mn0.50]O-2 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]O-2 and Li[Ni(0.25)Li(0.17)Mno.58]O-2 compounds give high initial discharge capacities of over 245 mAhg(-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)]O-2 compounds with low Ni content. (C) 2003 Elsevier B.V. All rights reserved.