A review of alkaline aqueous electrolytes for supercapacitors

Alkaline aqueous electrolytes (primarily KOH and NaOH solutions) have served as crucial electrolyte systems in supercapacitors due to their high ionic conductivity, environmental friendliness, low cost and high safety. This review systematically summarizes the fundamental characteristics of aqueous alkaline electrolytes, including the basic features and advantages, the functions of key components (alkali sources, solvents, additives), and the interaction between aqueous alkaline electrolytes and electrode materials (carbon−based, metal oxides/hydroxides, conductive polymers). It highlights the core challenges in alkaline electrolyte systems: the narrow electrochemical stability window (≤1.0 V) and performance deterioration at low temperatures. In response, the review covers recent advancements in optimization strategies such as the high–concentration electrolyte strategy, novel composite electrolytes, and the water/organic co–solvent strategy. Finally, future research directions are proposed, including: developing novel alkaline electrolytes with wider potential windows and higher stability, and designing high−performance, long−life electrode materials compatible with alkaline environments.