Progress and challenges of Prussian blue analogs for potassium-ion batteries: a perspective on redox-active transition metals

Potassium-ion batteries (PIBs) are becoming one of the substitutes for lithium-ion batteries (LIBs) due to their abundant raw materials and low cost. However, the lack of cathode materials with high capacity, high working voltage and excellent cycle performance limits the development of PIBs. In this case, Prussian blue analogs (PBAs) are increasingly becoming a research focus as promising cathode materials owing to their good cycle stability and rapid potassium ion diffusion rate in their 3D framework. Herein, from the perspective of redox-active transition metals (Fe, Mn, Co, Ni, etc.), we present the development and electrochemical properties of all the reported PBAs and summarize their advantages and disadvantages in terms of capacity, cycle life, voltage plateau, cost, etc. Finally, aiming at PBAs with different redox-active transition metals, some versatile strategies and specific methods are proposed for the future development of PBAs and the commercial application of PIBs.