Mechanistic Insights Into Aqueous Proton Batteries

ABSTRACT Battery energy storage systems are imperative to the development of sustainable energy resources for carbon neutrality. Protons, as charge carriers, have tremendous advantages over other metallic and non‐metallic ions, such as the lowest molar mass, minimal ionic size, and high ionic conductivity. Thus, aqueous proton batteries (APBs) have remarkable electric and chemical energy conversion efficiency, becoming an advanced battery technology. In aqueous electrolytes, protons are derived from H 2 O, enabling APBs with fast diffusion kinetics, large capacity, long cycle life, and economic effectiveness. The development of APBs is systematically highlighted in this review. The highly appealing features of proton battery chemistry are discussed, followed by a detailed exploration of proton storage materials, and an in‐depth insight into six distinct proton storage mechanisms in APBs, including proton/hydrogen gas catalytic reactions, proton intercalation reactions, proton conversion reactions, proton coordination reactions, pseudocapacitive proton storage reactions, and hydrogen storage reactions. The challenges of APBs in grid‐scale energy storage are summarized, and the future development directions are prospected. This review offers mechanistic insight into the development of high‐performance proton storage materials and the design of promising APBs.