Structural changes and electrochemical properties of Li2Cu1 − xMxO2 for lithium secondary batteries

Li2CuO2 substituted by various cations, such as Co, Ni, Fe, Mn, and Ti, was examined to decrease the irreversible capacity of unsubstituted one. Among several kinds of cations tested, Ni and Co were found to be effective in improving the irreversible capacity. Li2Cu0.7Ni0.3O2 exhibited a reversible capacity of about 150 mAh/g, while the unsubstituted one exhibited a capacity of only about 100 mAh/g. The structural changes in the Cu-based oxides that occurred during the electrochemical reaction were investigated with ex-situ XRD measurements. The results indicated that the structural transformation behavior changed as a result of the cation substitution.