Unveiled correlations between electron affinity and solvation in redox potential of quinone-based sodium-ion batteries

First-principles density functional theory method is employed with experimental techniques to investigate the redox properties and charge storage performance of seven quinone derivatives and to assess their potential as cathodes in sodium-ion batteries. The computed redox properties are comprehensively correlated with other properties, namely, electron affinity (EA), solvation energy, charge storage capacity, and energy density. The correlations are further verified to be applied not only to quinones but also to other organic molecules. The established universal correlations highlight three main conclusions. First, EA and solvation energy need to be cooperatively tuned to achieve a specific redox potential. Second, the exceptionally high performance of anthraquinone-2,6-dicarboxylic acid can be explained by the correlation of the redox potential with EA and solvation energy. Third, the differences in the performance between the calculated and experimental values for the other six quinone derivatives mainly result from the Na binding configurations, highlighting the experimental charge capacity is extraordinarily enhanced by metastable Na binding scenarios.