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 C=N 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.