Electroanalytical studies on sol-gel derived LiNi0.8Co0.2O2

The electrochemical behavior of LiNi0.C-8(O0).O-2(2), synthesized by a sol-gel method with maleic acid as a chelating agent, was investigated using galvanostatic charge-discharge cycling and electrochemical impedance spectroscopy. Unimolar solutions of LiPF6 in mixed carbonate solvents such as EC:DEC, DEC:DMC, PC:DMC and EC:DEC:DMC were used as the electrolytes. The impedance response was found to be dependent on the extent of intercalation and deintercalation, although it was independent of the electrolyte composition. However, the charge-discharge behavior of the cathode material was found to be dependent on the electrolyte composition. Cells with 1 M LiPF6 in EC:DEC gave the highest capacity. With this electrolyte, the first-cycle discharge capacity was 187 mAhg(-1). The first-cycle capacities obtained with the other electrolytes were lower, between 174 and 182 mAhg(-1). The impedance parameters of the system at different levels of intercalation and deintercalation were derived using equivalent circuit models. (C) 2003 Elsevier B.V. All rights reserved.