Study of electrochemical properties of LiCoO2 and LiCo0.4Ni0.6O2 as cathode materials in rechargeable batteries

Abstract

Intercalation cathode materials belonging to the 4-volt class electrodes, lithiated cobalt oxide LiCoO2 and lithiated nickel cobalt oxide LiCo0.4Ni0.6O2, were synthesized by sol-gel technique. The structural characteristics of the compounds were studied using XRD, FTIR and DSC. The compounds were used as cathode materials for assembling rechargeable lithium-batteries and their electrochemical performances were studied. The potentiostat and galvanostat techniques were used to determine the electrochemical characteristics. The irreversible capacity loss of LiCoO2 during the first charge-discharge is about 20% and for LiCo0.4Ni0.6O2 is about 90% for two different current rates of 5 and 10 A kg-1. The overall electrochemical capacity of LiCo0.4Ni0.6O2 has been drastically reduced due to the s-block or p-block metal substitution. Also the un-reacted materials remained as impurities gave a very poor cycleability. However more stable charge-discharge performances have been observed for LiCoO2 at different current rates. Differences and similarities between these two cathode materials in batteries are also discussed. The Li-ion batteries were assembled using the sol-gel synthesized cathode materials, natural untreated vein graphite of Sri Lanka as the anode material and 1 M LiPF6 in EC/DMC as liquid electrolyte, and their performances were tested.