Anthraquinone-based polyimide cathodes for sodium secondary batteries

Two polyimides using redox-active anthraquinone group as the connection unit are synthesized and characterized as cathodes for sodium secondary batteries. Sodium cells based on these two polyimide cathodes provide reversible capacities as high as 165 and 192 mAh g− 1, respectively, with excellent cyclabilities. A reversible four-electron transfer can occur for both of these two polyimides in the voltage range of 1.2-3.2 V with cyclic voltammetry measurements. These results suggest that anthraquinone is a promising connection unit for designing polyimide-based cathodes with high capacities for sodium secondary batteries.