Electrochemistry and Solid‐State Chemistry of NaMeO 2 (Me = 3d Transition Metals)

Abstract Sodium 3d transition metal oxides for Na‐ion batteries have attracted attention of battery researchers because of their new chemistries and abundant material resources in the earth. Some companies have also developed Na‐ion battery prototypes mainly consisting of a layered oxide as a positive electrode material and hard carbon as the negative one for practical use. In this article, progress of Na‐containing layered transition‐metal oxides is reviewed in terms of fundamental chemistry and technology aspects for future batteries as a post Li‐ion battery. To realize practical positive electrode materials is still challenging and the practical issues are discussed. In this context the authors propose strategies for designing layered transition‐metal oxide materials toward realization of practical Na‐ion batteries.