Accommodating diverse ions in Prussian blue analogs frameworks for rechargeable batteries: The electrochemical redox reactions

Prussian blue analogs (PBAs) that can host almost all ions having been used in and potentially utilized in batteries, have been proposed as electrode materials for the largest variety of rechargeable batteries including single-valent (Li+, Na+, K+), multivalent (Zn2+, Cu2+, Fe2+, Mg2+, Ca2+, Sr2+, Ba2+, Pd2+, Al3+, Y3+) metal ion batteries and even non-metal charge carrier (H+, NH4+, H3O+) batteries. On the other hand, PBAs with threedimensional open framework can provide highly reversible insertion/removal of ions in both aqueous and non-aqueous electrolytes. What is more, PBAs possess two active redox species for redox reactions during electrochemical charge/discharge process, potentially providing high specific capacity for batteries. However, in most cases, only one transition-metal specie is activated during charge/discharge process, together with existence of vacancies and coordinated/interstitial water molecular, leading to 50% lower electrochemical utilization of PBAs framework. In this review, we present a comprehensive overview on electrochemical redox of PBAs hosting Li+, Na+, K+, Zn2+, Cu2+, Fe2+, Mg2+, Ca2+, Sr2+, Ba2+, Pd2+, Al3+, Y3+, H+, H3O+ and NH4+ ions for rechargeable batteries, including number of redox active species, structural evolutions, output voltage, capacity delivered and cyclic stability. We also analyze the strategies and progresses in overcoming issues associated with achieving high specific capacity, high output voltage and long cyclic lifespan of batteries based on PBAs cathodes. Finally, perspectives are provided on the design requirements for future generation of PBAs electrodes, with focus on synthetic strategies, structure design, electrolyte optimization and electrochemical principle towards large-scale electric application.

Automated summary

Prussian blue analogs (PBAs) show great potential as electrode materials for various rechargeable batteries, offering highly reversible insertion/removal of ions in both aqueous and non-aqueous electrolytes. However, challenges like limited electrochemical utilization of PBAs framework need to be addressed for further development.