In-situ Raman investigation and application of phenazine-based organic electrode in aqueous proton batteries

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Aqueous proton batteries (APBs) have aroused attention because of the proton as charge carrier with smaller ionic size and faster kinetics when compared to the metallic ions in aqueous solutions. Although phenazine-based organic compounds with available redox-active sites are considered as promising organic electrode materials, the comprehensive study of their proton-storage behaviors and APB applications is still lacking so far. Herein, a rod-like diquinoxalino-phenazine (DPZ) organic compound is designed and synthetized via a facile dehydration approach. In-situ Raman investigation and theoretical calculation are conducted to probe into the proton redox process of DPZ organic electrode for the first time. It is demonstrated that three CN electroactive regions in each DPZ molecular unit could be simultaneously coordinated with two protons and the redox reaction between CN and CN bonds is highly reversible upon proton insertion/extraction. As expected, the DPZ organic electrode delivers a large proton-storage capacity of ∼ 218 mAh/g and long-term cycle performance without obvious dissolubility in acidic aqueous electrolyte. For real applications, soft-package and wire-shaped APBs based on such DPZ organic electrode are constructed, and they both achieve outstanding electrochemical characteristics, revealing their great potential applications in low-cost, high-safety, and high-performance energy technologies and portable/wearable electronics.