Recent Progress of Layered Transition Metal Oxide Cathodes for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are attracting increasing attention and considered to be a low-cost complement or an alternative to lithium-ion batteries (LIBs), especially for large-scale energy storage. Their application, however, is limited because of the lack of suitable host materials to reversibly intercalate Na+ ions. Layered transition metal oxides (Nax MO2 , M = Fe, Mn, Ni, Co, Cr, Ti, V, and their combinations) appear to be promising cathode candidates for SIBs due to their simple structure, ease of synthesis, high operating potential, and feasibility for commercial production. In the present work, the structural evolution, electrochemical performance, and recent progress of Nax MO2 as cathode materials for SIBs are reviewed and summarized. Moreover, the existing drawbacks are discussed and several strategies are proposed to help alleviate these issues. In addition, the exploration of full cells based on Nax MO2 cathodes and future perspectives are discussed to provide guidance for the future commercialization of such systems.