Regulating Proton Activity of Quinone-Based Electrodes for Aqueous All-Organic Batteries

Aqueous Zn-organic batteries (ZOBs) have emerged as a focal point due to their eco-sustainability and versatility. However, the origins of protons and their impact on electrochemical performance remain poorly understood and are subject to considerable debate. To address this gap, it is proposed to investigate model quinone-based electrodes, 3,5-Di-tert-butyl-o-benzoquinone (DBBQ), in mild-to-strong acidic conditions. The electrochemical features of DBBQ in Zn²⁺-based mild electrolyte are elaborated, proving its preferential coordination with protons over Zn²⁺ cations. Notably, proton-driven electrochemical reactivity exhibits superior stability and higher operating voltage, whereas the reactivity region of Zn²⁺ leads to significant capacity loss. To highlight the unique aspects of protons, an aqueous all-quinone proton battery is fabricated under acidic conditions. As a proof-of-concept demonstration, the proton rocking-chair cell exhibits satisfactory electrochemical performance, illustrating the feasibility of metal-free sustainable batteries. With an emphasis on the fundamental impacts of electrolyte composition and pH, the findings reveal that the manners of proton storage can be regulated via the regulation of solvation character of the anions, which provides new perspective to understand the mechanistic charge storage of organic electrodes in aqueous batteries.