Non-metallic charge carriers for aqueous batteries

Charge carriers are fundamental components of batteries that determine battery chemistry and performance. Non-metallic charge carriers provide an alternative to metallic charge carriers in aqueous batteries, enabling fast kinetics, long cyclic lifetime and low manufacturing costs. Non-metallic charge carriers not only can be inserted into the electrode framework, where they establish covalent–ionic bonds, but can also serve as reversible redox centres for charge transfer, resulting in superior performance compared with metallic charge carrier-based devices. In this Review, we discuss cationic and anionic non-metallic charge carriers, their physicochemical properties, charge storage mechanisms and electrode interactions. We examine battery configurations of non-metallic charge carrier-based devices and analyse battery performance based on costs, capacity, working potential, rate capability and cycling stability. Finally, we highlight design strategies for aqueous batteries based on non-metallic charge carriers and future applications. This Review discusses non-metallic charge carriers for aqueous batteries, investigating fundamental mechanisms of charge storage and electrode interactions, as well as battery design and performance.