Abstract 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. During electrochemical deintercalation of lithium an increase in the electrical conductivity by 6 orders of magnitude was recorded. The observed insulator–metal transition in LixCoO2 can be interpreted on the basis on the Anderson type transition. Drastic evolution of the top valence band features well corroborates crystallographic data as well as the particular effect of the oxygen octahedron distortion on computed DOS shape. 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.