Stable Cycling Cathode Materials and Their Energy Storage Mechanism for Sodium Ion Batteries

The development of large scale energy storage systems (ESSs) aimed at application with renewable electricity sources and in smart grids is expected to address energy shortage and environmental issues. Sodium ion batteries (SIBs) exhibit remarkable potential for satisfying the raw material supply and economic requirements of large scale ESSs because of the high richness and accessibility of sodium reserves. High stability of electrodes during cycling means long service life for energy storage, which is important for large scale ESSs to reduce the cost s generated by exchange or maintenance processes. Using low cost and abundant elements in cathodes with long cycling stability is preferable for lowering expenses on cathodes because it is vital for large scale ESSs to cut costs resulting from manufacture, exchange, and maintenance operations. Organic electroactive compounds hold great potential to act as cathode materials for SIBs because of their environmental friendliness, sustainability, and high theoretical capacity after rational design. Most reported organic materials have no reversibly sodium ions in their natural state , however, which is different from other promising cathodes for commercialization Therefore, the sodium detachable ability of these materials to directly match with sodium free anode needs more exploration. Another promising type of cathode for large scale application is Prussian blue analogues PBAs However, PBAs suffer from poor cyclability and sluggish kinetics due to large lattice distortion and poor conductivity which severely damage their practical application in large scale SIBs Therefore, it is necessary to understand the origins of capacity decrease in PBAs at the atomic scale and materials scale with the aim of fabricating suitable PBAs for large scale applications.