Unraveling the Diversity of the Storage Mechanism in Carbonyl Materials toward Different Metal Ions

Due to their structural diversity, environmental friendliness, and resource renewability, organic electroactive compounds are versatile hosts for the energy storage of different metal ions. However, the consistency and variety of the energy storage performance and mechanism for the designed organic electrode materials in aqueous electrolytes toward different metal ions have rarely been researched. Here, one type of organic material integrated with anhydride and imide groups was designed and studied in detail. Among the two functional groups, the anhydride carbonyl groups were found to be the dominant contributors during the initial discharge step due to the higher binding energy toward the different metal ions, while the imides were responsible for the second-step coordination with monovalent metal ions. With the increment of the valence of guest metal ions, the activity of the imides decreased and became nearly inactive for the storage of aluminum ions. On the contrary, the anhydride carbonyl groups were always active for the storage of various metal ions and became the capacity contributors when the valence of the metal ions increased. Moreover, similar energy storage behaviors and close potentials were detected during the first discharge step for these different metal ions.