This project investigated the complex role of water in Prussian blue analogues (PBAs)—a family of framework materials used as cathodes in sodium-ion batteries. By combining neutron diffraction, total scattering, inelastic and quasi-elastic neutron scattering, and complementary spectroscopic methods, the research explored how water content, alkali cation concentration, and vacancy levels together determine the composition, local structure, and dynamic behavior of these materials.
The studies revealed that PBAs are far more structurally flexible and dynamic than previously assumed: both water molecules and sodium ions occupy a range of positions that shift with temperature and hydration state. Dehydration or sodium depletion increases disorder, while distortions of the framework were shown to be an intrinsic property of the structure.
Through a comprehensive multi-technique approach, the work established new strategies for accurately characterizing the composition, structure, and dynamics of PBAs, providing crucial insights for the design of stable and efficient electrode materials for next-generation sodium-ion batteries.