Anchoring I via Charge-Transfer Interaction by a Coordination Supramolecular Network Cathode for a High-Performance Aqueous Dual-Ion Battery.

Iodine is considered to have broad application prospects in the field of electrochemical energy storage. However, the high solubility of I severely hampers its practical application, and the lack of research on the anchoring mechanism of I has seriously hindered the development of advanced cathode materials for iodine batteries. Herein, based on the molecular orbital theory, we studied the charge-transfer interaction between the acceptor of I with a σ* empty antibonding orbital and the donor of pyrimidine nitrogen with lone-pair electrons, which is proved by the results of UV-vis absorption spectroscopy, Raman spectroscopy, and density functional theory (DFT) calculations. The prepared dual-ion battery (DIB) exhibits a high voltage platform of 1.2 V, a remarkable discharge-specific capacity of up to 207 mAh g, and an energy density of 233 Wh kg at a current density of 5 A g, as well as outstanding cycle stability (operating stably for 5000 cycles) with a high Coulombic efficiency of 97%, demonstrating excellent electrochemical performance and a promising prospect in stationary energy storage.