Challenges and Opportunities of Water-Based Processing of Prussian White Electrodes

Prussian white (PW) is among the most promising cathode materials for sodium-ion batteries due to its high theoretical specific capacity and cost-effective synthesis routes. To maintain cost advantages compared with lithium-ion batteries, water-based electrode processing is desirable; however, the strong water affinity of PW introduces significant challenges. Here, we systematically investigate the influence of thermal pre-treatment of PW on particle morphology during aqueous processing and on the electrochemical performance and evaluate how binder selection affects electrode stability. Repeated dehydration and rehydration during pre-treatment and subsequent water-based processing trigger phase transformations, leading to surface cracking and porosity. In addition, direct contact with water can promote partial dissolution of Na + and [Fe(CN) 6 ] 4− and generate vacancies within the crystal framework. Although N-methyl-2-pyrrolidone-based processing yields unwarped electrodes, high bulk and interfacial resistances limit rate capability at C/2. In contrast, the water-processed electrode delivers higher specific discharge capacity despite inward warping. An additional step of thermal pre-treatment can be beneficial for capacity retention. Overall, these findings reveal a trade-off between particle integrity and long-term electrochemical cyclability of PW electrodes and suggest that binder selection should be a key consideration in further optimization.