LixCoO2 (0<x<-1): A new cathode material for batteries of high energy density

A new system LixCoO2 (0<x〈-1) has been prepared by electrochemical extraction of lithium from the parent LiCoO2 ordered rock-salt structure. Measured open-circuit voltages with respect to lithium metal are approximately twice those of LixTiS2 (0〈-x〈-1), and a theoretical energy density of 1.11 kWh kg−1 is calculated for LixCoO2Li. Preliminary voltage-composition curves show low overvoltages and good reversibility for current densities up to 4 mA cm−2 over a large range of x.