Engineering electron cloud density of phenazine for high-voltage and long-life alkaline batteries

Abstract

Alkaline aqueous batteries, with intrinsic high safety and potential for high voltage, have always been a hot research topic. Despite several generations of development of anode materials, they still face the challenge of poor cycling stability. Imines have a significant advantage in stability compared to other n-type materials, but their potential is not low enough compared to metal anodes. Herein, a symmetrically structured, extended π-conjugated imine compound, namely cyano-substituted dotriaconta tetrazaoctacyclo (4CNDTZ), was synthesized for the first time and evaluated as the anode materials for alkaline aqueous batteries. 4CNDTZ exhibits a remarkable capacity of 250 mAh g^-1 at 0.2 A g^-1, coupled with a remarkably low plateau potential of -0.81 V (vs. SHE), significantly below that of conventional alkaline battery anodes. Advanced characterization techniques alongside theoretical calculations confirm that the active sites crucial for its performance are the CN and CN groups, driving an oxidation–reduction process involving the transfer of 4 K⁺ and 4 electrons. When coupled with Ni(OH)₂ cathode, the full cells exhibit a discharge voltage plateau of 1.17 V, allowing the full cells to achieve an energy density of up to 170 Wh kg^-1 and sustain stable operation through 10,000 cycles.