This paper gives an overview of the research carried out on lithium and sodium layered materials as positive electrodes of lithium (sodium)‐ion batteries. It focuses on the solid‐state chemistry contribution to discover new materials and to optimize the properties versus the requirements imposed by the applications. Among, all material structures, which are considered, the layered ones (lithium based), are the best candidates for high energy density batteries for mobile applications. Recently, the homologous Na materials, which have lower energy, are considered for stationary applications due to their low price. Starting for LiMO2 materials or NaxMO2 (0.5 < x < 1), many substituted phases, obtained by high‐temperature solid‐state chemistry, have allowed stabilizing the layered structure in large composition domains to increase the specific capacity, which is directly related to the number of exchanged electrons during the cycling process.