Water driven phase transitions in Prussian white cathode materials

Abstract Prussian white (PW, N a 2 Fe close=")" open="("> CN 6 ? z H O ) is a promising cathode material for use in sodium-ion batteries large-scale energy storage applications, which demand long cycling life-times. However, non-aqueous battery applications PW must not contain any water, and yet dehydration induces large volume change destabilizing the structure reducing life. The undergoes multiple phase transitions as function of both sodium water content, however, mechanism behind poorly understood. Here, we neutron diffraction to explore influence on PW. For first time, two structures single composition were observed near room temperature independent synthesis method. These differ FeN 6 FeC octahedral tilting configurations, connected ordering framework. removal modulates magnitude pre-existing structural distortions, if it itself disordered within structure, rather than modifying nature distortions. results provide robust fundamental understanding chemical driving force impacting distortions blue analogues. insights guidance designing tilt-engineering ultimately enabling new materials with enhanced long-term electrochemical performance applications.