Site-Selective investigation of high rate Prussian Blue Cathode Materials for Sodium-Ion Batteries

Sodium-ion batteries are a promising, cost-effective alternative to cobalt-based systems, with Prussian Blue (PB) as a standout cathode material. While their electrochemical performance is competitive, the underlying reaction mechanisms, especially at high cycling rates, remain unclear. Operando Mössbauer spectroscopy, XRD, and XAS have provided insights into iron evolution during low-rate cycling (0.05C–0.1C), but the reaction pathway at high rates (1C–5C) is still unknown. Furthermore, conventional methods struggle to distinguish low-spin (LS) Fe²⁺ and Fe³⁺ sites due to similar hyperfine parameters. This study aims to employ site-selective enrichment and Synchrotron Mössbauer Spectroscopy (SMS) at ESRF’s ID14 beamline to study these iron sites and reveal the features of high-rate cycling in comparison with low-rate mechanisms.