Structure and electrochemical characterization of LiNL0.3Co0.3Mn0.3Fe0.1O2 cathode for lithium secondary battery

A lithium insertion material having the composition LiNi0.3Co0.3Mn0.3Fe0.1O2 was synthesized by simple sol-gel method. The structural and electrochemical properties of the sample were investigated using X-ray diffraction spectroscopy (XRD) and the galvanostatic charge-discharge method. Rietvelt analysis of the XRD patterns shows that this compound can be classified as alpha-NaFeO2 structure type (R3m; a=2.8689(5) angstrom and 14.296(5) angstrom in hexagonal setting). Rietvelt fitting shows that a relatively large amount of Fe and Ni ion occupy the Li layer (3a site) and a relatively large amount of Li occupies the transition metal layer (3b site). LiN0.3Co0.3Mn0.3Fe0.1O2 when cycled in the voltage range 4.3-2.8 V gives an initial discharge capacity of 120 mAh/g, and stable cycling performance. LiNi0.3Co0.3Mn0.3Fe0.1O2 in the voltage range 2.8-4.5 V has a discharge capacity of 140 mAh/g, and exhibits a significant loss in capacity during cycling. Ex-situ XRD measurements were performed to study the structure changes of the samples after cycling between 2.8-4.3 V and 2.8-4.5 V for 20 cycles. The XRD and electrochemical results suggested that cation mixing in this layered structure oxide could be causing degradation of the cell capacity.