Sodium layered oxides NaxCoO2 form one of the most fascinating low-dimensional and strongly correlated systems; in particular P2–NaxCoO2 exhibits various single-phase domains with different Na+/vacancy patterns depending on the sodium concentration. Here we used sodium batteries to clearly depict the P2–NaxCoO2 phase diagram for x≥0.50. By coupling the electrochemical process with an in situ X-ray diffraction experiment, we identified the succession of single-phase or two-phase domains appearing on sodium intercalation with a rather good accuracy compared with previous studies. We reported new single-phase domains and we underlined the thermal instability of some ordered phases from an electrochemical study at various temperatures. As each phase is characterized by the position of its Fermi level versus the Na+/Na couple, we showed that the synthesis of each material, even in large amounts, can be carried out electrochemically. The physical properties of the as-prepared Na1/2CoO2 and Na2/3CoO2 ordered phases were characterized and compared. Electrochemical processes are confirmed to be an accurate route to precisely investigate in a continuous way such a complex system and provide a new way to synthesize materials with a very narrow existence range.

A combined computational/experimental study on LiNi 1/3 Co 1/3 Mn 1/3 O 2 is presented. Both density functional theory and experiments are used to probe the active redox pairs and changes in electronic structure of LiNi 1/3 Co 1/3 Mn 1/3 O 2 during intercalation or deintercalation of Li. The phase stability and voltage curve of this material are also shown in this paper. Both the experimental and computational data show that LiNi 1/3 Co 1/3 Mn 1/3 O 2 material is a high-capacity stable electrode for advanced rechargeable lithium ion batteries.