High-voltage pH-decoupling aqueous redox flow batteries for future energy storage

Aqueous redox flow batteries (ARFBs) have attracted lots of attention as powerful and durable technologies for sustainable energy storage. However, the wide adoptions of ARFBs still face the challenge of restrained voltage output due to the limited electrochemical stable window of water. As a prospective solution, the pH-decoupling strategy, which uses positive and negative electrolytes with different pH values, has been proven to overcome the thermodynamic limit of water and expand the operational voltage range of the ARFBs. This review outlines the recent advancements in different types of pH-decoupling ARFBs, including the two-chamber system, three-chamber system, and decoupled system with independent pH recovery function. The merits and technical challenges for being highlighted to assess the application potentials of each system design. Furthermore, insights for future research directions are provided to guide further system enhancement and promote the development of stable pH-decoupling ARFBs.