The effect of varying the acid to metal ion ratio R on the structural, thermal, and electrochemical properties of sol-gel derived lithium nickel cobalt oxides

The lithiated nickel cobalt oxide LiNi0.8Co0.2O2 was synthesized using citric acid as a chelating agent by a sol-gel method. The effect of varying the acid to metal ion ratio R on the structural, thermal, and electrochemical properties of the synthesized compound were studied. The discharge capacity of LiNi0.8Co0.2O2 synthesized with an acid to metal ion ratio R=1 was 187 and 176 mAh/g for the 1st and 10th cycles, respectively. Increasing the R value to 2 resulted in a decrease in capacity to 170 mAh/g for the 1st cycle and 161 mAh/g after 10 cycles. A further increase in R value to 3 did not cause any appreciable improvement in the electrochemical performance of the cell. However, there was no decrease in capacity or cyclability compared to the compound synthesized at R=1. The structural, thermal, and electrochemical performance of the materials synthesized at different R values are compared and discussed. (C) 2002 Elsevier Science B.V. All rights reserved.