Understanding the sodium storage mechanisms of organic electrodes in sodium ion batteries: issues and solutions

Organic electrode materials offer a new opportunity to develop high energy/power density, low-cost, environmentally benign sodium ion batteries (SIBs). For many years this category of materials has not been considered as a potential electrode candidate for SIBs mainly because excessive research focused on inorganic materials due to their successful commercialization in the proven lithium ion battery (LIB) technologies. However, recently, many promising advancements have been made in the field of organic cathode and anode materials for SIB applications. This review for the first time consolidates and provides insights into the different sodium storage mechanisms observed in various categories of organic electrode materials. We believe that the fundamental understanding of the redox mechanisms that govern the electrochemical performances of SIBs is necessary to design new materials/electrodes and is beneficial for enhancing the existing properties of investigated compounds.