Inelastic neutron scattering on Prussian White as a function of the Na and water content

Prussian Blue Analogues (PBAs, AxM[M'(CN)6)]·zH2O) are a promising class of materials for sustainable positive battery electrodes, especially Prussian White (PW, Na2-xFe[Fe(CN)6]) due to its high theoretical capacity (160-170 mAh/g) and high operating potential (~3.2 V). However, the material exhibits many phase transitions as a function of the Na and water content followed by large volume changes. Water stabilizes the structure but is not good for battery applications leading to capacity fade upon electrochemical cycling. Thus, it must be removed or replaced with another compatible molecule. To successfully chemically modify PBAs and substitute water, a deeper fundamental understanding of the interactions between water and the PBA framework is needed. Inelastic neutron scattering (INS) is an ideal technique to study how neutral guest species, such as water, interact with A-site cations in PBAs. The INS experiment aims at developing a fundamental understanding of the structure-property relationships in PBAs and to pave the way for developing improved energy storage materials.