Sodium Ion

Water Content Matters - Key To Stability And Performance In Prussian White Systems Dreyer et. al. 1 quantified gas evolution in Prussian White PW) cathodes, showing that NaClO4 electrolyte caused significantly higher CN2 emissions than NaPF6 during cycling. Undried PW released up to 6.44 wt% water during overcharge, driving H2 evolution, while NaPF6 suppressed toxic cyanogen, underscoring the impact of water content and electrolyte on battery safety. Maddar et. al 2 showed that optimized dehydration of PW at 170°C under vacuum 10−2 mbar) for 48 hours achieved 10 wt% water loss, transitioning to a rhombohedral structure and increasing capacity to 160 mAh g−1. Longer drying times and lower pressures further enhanced electrochemical performance. Rehydration studies revealed up to 10% water uptake under standard conditions, reversing these improvements and highlighting critical thresholds for stability. Clavelin et al. 3 examined dehydration and rehydration in PW cathodes, showing that the monoclinic-to-rhombohedral phase transition occurs at 120°C under 10−2 mbar (vs. 135°C at 20 mbar). The rhombohedral phase achieved 90% of theoretical capacity 154 mAh g−1) compared to 81% 126 mAh g−1) for the monoclinic phase. Ultrafast rehydration reverted the rhombohedral phase to monoclinic within 80 minutes of air exposure. Effective control of water content and dehydration processes in Prussian White PW) cathodes is crucial for optimizing electrochemical performance and ensuring battery safety. Aqueous electrode processing is feasible if effective drying strategies are implemented. Source: [1 Dreyer SL, Maddar FM, Kondrakov A, Janek J, Hasa I, Brezesinski T. Elucidating Gas Evolution of Prussian White Cathodes for Sodium-ion Battery Application: The Effect of Electrolyte and Moisture. Batter Supercaps 2024;202300595. 2 Maddar FM, Walker D, Chamberlain TW, Compton J, Menon AS, Copley M, et al. Understanding dehydration of Prussian white: from material to aqueous processed composite electrodes for sodium-ion battery application. J Mater Chem A 2023;111577891. 3 Clavelin A, Thanh D Le, Bobrikov I, Fehse M, Drewett NE, López GA, et al. Dehydration Conditions and Ultrafast Rehydration of Prussian White: Phase Transition Dynamics and Implications for Sodium-Ion Batteries. ACS Mater Lett 2024520814.

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