A Closed‐Loop Direct Recycling Process for Prussian White From Scrap and End‐of‐Life Sodium‐Ion Batteries

ABSTRACT

Prussian White (PW, Na ₂ Fe[Fe(CN) ₆ ]· x H ₂ O) is a leading low‐cost cathode material for sodium‐ion batteries. Yet, recycling remains largely unaddressed due to the incompatibility of conventional pyrometallurgical and hydrometallurgical routes with its cyanometallate framework. Here, a closed‐loop direct recycling process for PW cathodes is reported, for both manufacturing scrap and end‐of‐life (EOL) sodium‐ion cells. Electrodes were delaminated using a low‐energy ice‐stripping technique, and the recovered powder was regenerated via mild, 80°C aqueous resodiation without calcination or corrosive solvents. The resodiation process simultaneously reinserts Na ⁺ ions, reduces Fe ³⁺ to Fe ²⁺ , and promotes surface regeneration through temperature and anion‐activated ‘surface healing’, a mechanism supported by control experiments and confirmed by XRD, Fe K‐edge XAS, XPS, Raman spectroscopy, and electron microscopy. Resodiated PW recovers 96%–97% of pristine half‐cell capacity and, in full‐cell configurations paired with hard carbon, retains ∼80% of initial capacity after 300 cycles, outperforming the pristine benchmark of ∼60%. The total energy input for resodiation at 80°C is ∼0.50 kWh, lower than that estimated for fresh PW synthesis (∼3.98 kWh). This work provides an experimentally validated pathway for closed‐loop recovery of Prussian White cathodes, with direct relevance to sustainable scale‐up of sodium‐ion battery technology.