@article{LUO2026, 
author = {Wen LUO and Jiyu XU and Kai FU and Hongwei CAI},
title = {Development on Prussian Blue for Aqueous Ion Batteries},
year = {2026},
journal = {Journal of the Chinese Ceramic Society},
volume = {54},
number = {3},
pages = {1161-1176},
keywords = {electrode material, electrochemical energy storage, Prussian blue analogues materials, aqueous ion batteries},
url = {https://www.sciopen.com/article/10.14062/j.issn.0454-5648.20250176},
doi = {10.14062/j.issn.0454-5648.20250176},
abstract = {Aqueous ion batteries have attracted recent attention due to their low cost, high safety, and environmental friendliness, making them a promising alternative to conventional lithium-ion batteries. Among the various electrode materials explored for aqueous ion batteries, Prussian blue analogues (PBAs), with the general formula A2T[M(CN)6] (where A = Li, Na, K; T = Fe, Co, Ni, Mn, Cu; and M = Fe, Mn, Co), emerge as a highly promising class of materials. PBAs are characterized by their large open frameworks, abundant ion insertion sites, and ease of synthesis, which contribute to their superior electrochemical performance. This review systematically summarizes the structural properties, synthesis strategies, and applications of PBAs in aqueous lithium-ion, sodium-ion, potassium–ion, and ammonium-ion batteries, while addressing the key challenges and future directions for their development. The crystal structure of PBAs, determined by X-ray diffraction, consists of a face-centered cubic (FCC) framework, where Fe3+ and M2+ ions are octahedrally coordinated to the carbon and nitrogen atoms of cyanide groups, respectively. This structure creates a three-dimensional porous network capable of accommodating various guest ions. PBAs, which are derived via substituting Fe with other transition metals (i.e., Cr, V, Mn, Co, Ni, and Cu), retain the same structural framework, but exhibit enhanced electrochemical properties due to the presence of dual redox-active centers (i.e., Fe3+/Fe2+ and M3+/M2+). These redox pairs enable high theoretical capacities and reaction potentials, making PBAs suitable for high-performance battery applications. However, PBAs often suffer from structural defects, such as Fe(CN)6 vacancies, which can compromise their electrochemical stability. These vacancies, typically formed during rapid precipitation, can lead to a structural collapse during cycling, particularly in systems involving multi-electron reactions. To mitigate these issues, researchers have developed some strategies to synthesize low–defect PBAs with an improved structural integrity and cycling stability. PBAs can be synthesized by various methods, i.e., co-precipitation, hydrothermal synthesis, and single-precursor approaches. Co-precipitation as one of the most common methods involves the reaction of Fe3+ salts with [Fe2+(CN)6]4– in aqueous solutions, resulting in the formation of PB or its analogues. Hydrothermal synthesis involves the production of well-crystallized PBAs with controlled morphologies at high temperatures and pressures. The single-precursor method, which relies on the slow release of Fe3+ or Fe2+ ions from [Fe(CN)6]4– or [Fe(CN)6]3– precursors, offers a route to highly mono-dispersive PBA nanoparticles. Despite the widespread use of lithium-ion batteries, their application in aqueous systems is limited due to the poor compatibility of PBAs with hydrated Li+ ions. The small ionic radius of Li+ leads to a structural instability in PBAs, thus having a rapid capacity decay. However, recent studies have explored the use of salt-in-water electrolytes to improve the reversibility of Li+ insertion in PBAs, offering a potential pathway for their application in aqueous lithium-ion batteries. Aqueous sodium-ion batteries with their low cost and natural abundance of sodium emerge as a viable alternative to lithium–ion batteries. PBAs, particularly those based on Fe, Mn, and Co, have the excellent performance in sodium-ion batteries due to their ability to accommodate larger Na+ ions. For instance, FeFe–PBAs and MnFe–PBAs exhibit high specific capacities and long cycle lives, making them attractive candidates for grid-scale energy storage. However, the presence of structural vacancies remains a challenge as they can lead to capacity fading during cycling. Aqueous potassium-ion batteries face some challenges due to the large ionic radius of K+, which can cause significant volume changes during cycling. PBAs with their large interstitial spaces are well-suited for K+ insertion and demonstrate high reaction potentials and excellent cycling stability. For instance, K2NiFe(CN)6 has a remarkable performance with a high capacity retention over thousands of cycles. In addition, mixed-ion systems, such as Na+/K+ hybrid batteries, are also developed to leverage the advantages of both ions, further enhancing the performance of PBAs in potassium-ion batteries. Aqueous ammonium-ion batteries, though less explored, offer unique advantages due to the large ionic radius of NH4+, which matches well with the interstitial spaces in PBAs. This compatibility results in high reaction potentials and stable cycling. Recent studies have demonstrated that PBAs such as CuFe-PBAs can achieve high specific capacities and excellent cycle life in NH4+batteries, particularly when paired with Zn anodes. However, the development of full-cell configurations remains a challenge due to the limited availability of NH4+-compatible anodes. Aqueous proton batteries, though less common, have shown a potential due to the unique transport mechanism of protons in PBAs. Protons can rapidly diffuse through the hydrogen-bonded water networks within the PBA structure, enabling a high-rate performance. PBAs such as Nao·4(VO)3[Fe(CN)6]2·12H2O demonstrate high capacities and excellent cycling stability in acidic electrolytes, making them promising candidates for high-power applications. Despite the development of PBAs for aqueous ion batteries, several challenges still remain. The presence of structural vacancies and water in the PBA framework can lead to a capacity fading and a structural instability during cycling. Future research should focus on understanding the mechanisms of vacancy formation and developing strategies to eliminate these defects. In addition, the optimization of electrolyte composition and the enhancement of electronic conductivity in PBAs are also critical for improving their performance in practical applications. In conclusion, PBAs represent a versatile and promising class of materials for aqueous ion batteries, offering high capacities, long cycle lives, and superior rate capabilities. PBAs have a potential to play a key role in the development of next-generation energy storage systems via addressing the existing challenges and further exploring their electrochemical properties.}
}