Dihydrophenazine Derived Pd₆L₁₂ Cage: Self-Assembly, Polyradical Cations, and Lithium Battery Cathode Application

In this study, we present the self-assembly of a dihydrophenazine-based Pd₆L₁₂-type coordination cage 1 showing excellent redox activity and demonstrate the use as the cathode for lithium batteries. The structure of cage 1 was confirmed by single-crystal X-ray diffraction analysis. The excellent reversible redox performance of 1 and its electrochromic properties induced by radical species were systematically characterized using in situ UV-vis-NIR and EPR spectroelectrochemistry. Notably, a highly stable radical cationic species 1^12•+, containing 12 radical cations, was successfully obtained through the chemical oxidation of 1, and its single-crystal structure was resolved. The excellent redox properties of 1 enable its application as a cathode material for lithium batteries. The 1|Li cell exhibited good cycling stability, nearly 100% coulombic efficiency, and an initial discharge capacity of 84 mAh g⁻¹ within a voltage range of 2.5-4.0 V. Furthermore, in situ 2D EPR experiments on lithium batteries visually revealed the excellent cycling stability of the 1-based cathode material and its reversible two-step electron transfer process. This study provides important insights into the design, synthesis, and properties of functionalized redox-active coordination cages, offering a reference for their application in energy storage and functional materials research.