Insights on the proton mechanism in carbonyl-based organic electrode of neutral aqueous battery

Implementing proton insertion/removal in an aqueous battery has advantages like high safety, high rate, and low-temperature properties. The proton energy storage materials are mainly based on inorganic material in a strong acid electrolyte. Proton batteries attract much attention under neutral condition, especially based on the metal-free organic electrode. However, the proton concentration of neutral electrolyte is very low, and the proton insertion mechanism is not well understood. Herein, we firstly uncover the special energy storage mechanism of carbonyl materials as proton acceptor in neutral electrolyte. Carbonyl groups adsorb water molecular and induce proton insertion, this diffusion-free mechanism determines its fast reaction kinetics, which helps to improve the power density. Released OH− during proton insertion creates a local alkaline environment, which broadens the electrochemical window and contributes to the high energy density. With the structural diversity and tunability of carbonyl group, this special mechanism indicates that carbonyl-based organic materials are potential electrode for low-cost and high-performance neutral aqueous battery in the future.