Particle Size Control in Continuous Flow Coprecipitation of High‐Sodium‐Content Prussian White

Sodium‐ion batteries are a cost‐effective and more sustainable alternative to lithium‐ion systems for large‐scale energy storage. Among potential cathode materials, Prussian white (PW) is attractive due to its open framework, high theoretical capacity, and favorable sodium‐ion transport. In this study, we report a continuous‐flow coprecipitation process for the scalable synthesis of high‐sodium‐content PW with controlled composition, crystallinity, and particle size. The system employs a Taylor–Couette reactor with separate ferrocyanide/reductant/acid and FeSO 4 /acid feeds; redox control via Na 2 SO 3 and mild acidification suppresses Prussian blue impurities. Operation at 90°C and ≈ 1 bar with a mean residence time of ≈ 60 min yields monoclinic PW with Na/Fe ratios of 0.81–0.88, median particle sizes (D50) of 6–17 µm, water contents of 10.8–13.2 wt%, and BET surface areas of ≈ 7.7–7.9 m 2 g −1 at space‐time yields of 47–93 g L −1 h −1 . The study addresses the synthesis and materials characterization; electrochemical testing was outside its scope.