Advancements in cathode materials for aqueous proton batteries

Aqueous proton (hydrogen-ion) batteries (APBs) have attracted significant attention recently as one of the most promising alternatives to lithium-ion batteries. However, the advancement of APBs is largely constrained by the slow development of cathode materials. This review summarizes the latest progress in APB cathode materials, including metal oxides, Prussian blue analogs, and organic materials. The electrochemical properties of these reported cathode materials—including charge storage mechanisms, capacity, rate performance, and cycling stability—are identified and analyzed to enable the development of high-performance APBs suitable for practical applications. The intricate interplay between material structures and proton dynamics is thoroughly examined, revealing how nanostructure engineering, heteroatom doping, and strategic material compositing can lead to unprecedented performance enhancements. Finally, the technological advancements, scientific challenges, and future research opportunities of APB cathode materials are briefly reviewed. Additionally, strategies to enhance their electrochemical performance are proposed, providing insights and guidance for the next phase of APB research.