Understanding crystal structures, ion diffusion mechanisms and sodium storage behaviors of NASICON material

Sodium super ionic conductor (NASICON) based electrode and electrolyte compounds offer new prospect to achieve higher energy/power densities, improved safety, and longer cycle life in sodium ion batteries (SIBs). For many years NASICON compounds have not been regarded as a possible electrode material for SIBs, mainly because, the research was focusing on the electrolyte aspect. However, in recent years NASICON type materials have attracted a great deal of attention as an electrode as well due to their excellent properties, which include high ionic mobility, better safety and improved structural stability. This review for the first time features and consolidates the ion diffusion mechanisms and crystal structures of different explored NASICON materials. It also provides insight into the present challenges to commercialize these materials for developing functional SIBs. We believe that the thorough understanding of the ion diffusion mechanisms and crystal structures of NASICON based materials is necessary to design new electrodes and will be useful to improve the electrochemical performances of SIBs. The advantages/disadvantages of each category of materials are also discussed. Apart from the widely investigated NASICON type cathode and anode materials, the rarely explored electrolyte material is also included for the complete review of this potential material. We believe that our detailed analysis on crystal structure and ion diffusion mechanism presented in this review will provide insights into important progress that are made in NASICON materials and could open up new opportunities for devising battery formulations that would continue to evolve and will also appeal to broad research audience.Y