Electronic origin of difference in discharge curve between LixCoO2 and NaxCoO2 cathodes

This paper presents a novel approach to an explanation of apparently different characters of the discharge/charge curve in LixCoO2 (monotonous curve in large range of lithium content) and NaxCoO2 − y systems (step-like curve). Comprehensive experimental and theoretical studies on crystallographic, electronic and electrical transport properties of the LixCoO2 battery cathode material are reported. In the case of NaxCoO2 − y it was evidenced that the origin of the observed step-like character of the discharge/charge curve of NaxCoO2 − y is due to the specific features of the electronic structure, arisen from the presence of the oxygen vacancies and sodium ordering.