Towards Prussian blue analogues-based advanced aqueous batteries: From facing critical challenges to feasible solutions

Prussian blue analogues (PBAs) have been considered as one of the most promising candidates of aqueous batteries owing to their advantages such as large pore size, high safety, low solubility equilibrium constant, and adjustable output voltage. However, controllable synthesis of high-performance PBAs for aqueous batteries remains a challenging task due to the presence of unavoidable crystal defects, coordinated water, metal ion dissolution, and a stable window of limited aqueous solution. To address these challenges and achieve practical applications, significant efforts made and some key progress have been made. The structure and electrochemical behavior of PBA, such as electronic transfer, ion transport, ion diffusion, and material phase transitions, are extensively discussed. In addition, on the basis of a comprehensive introduction to the many challenges faced by the use of PBAs in aqueous batteries, we systematically summarized the synthesis routes of PBAs and modification strategies, such as acid/base chemical etching, inorganic/organic compound, transition metal doping. Finally, an insight into the future research directions and further development prospects of PBAs-based materials are proposed so as to facilitate the extensive application in the filelds of aqueous batteries. This review provides significant comprehension for construction and optimization of high-performance PBAs-based materials used in aqueous batteries.