Studies on LiNi0.7Al0.3-xCoxO2 solid solutions as alternative cathode materials for lithium batteries

A series of phase-pure Co- and Al-substituted lithium nickel oxide solid solutions of the composition LiNi0.7Al0.3-xCoxO2 with x = 0.0, 0.1, 0.15, 0.2, and 0.3, has been synthesized by adopting urea-assisted combustion (UAC) route. The structure and the physico-electrochemical features of the doped materials have been evaluated through PXRD, FTIR, SEM, CV, and charge/discharge studies. The stabilization of Ni in the +3 state and the existence of enhanced 2D-layered structure without any cation mixing have been substantiated from XRD. The results of the XRD and FTIR studies have established the complete mixing of Al and Co with Ni, especially at the various levels and the combinations of the dopants attempted in the present study. The enhanced electrochemical performance of LiNi0.7Al0.3-xCoxO2 may be attributed to the "synergetic effect" resulting from the presence of both Al3+ and Co3+ dopants in the LiNiO2 matrix. From CV studies, it was understood that the addition of 10% Co is effective in suppressing the phase transformation during Li+ intercalation process that leads to better electrochemical properties. The effect and the extent of substitution of Ni with Al and Co on the structural and electrochemical performance of LiNi0.7Al0.3-xCoxO2 are discussed elaborately in this communication. (C) 2003 Elsevier Ltd. All rights reserved.