Surface modification enables long-term cycling of Prussian white in sodium-ion batteries

Abstract

Prussian blue analogs (PBAs) are promising cathodes for sodium-ion batteries. Yet, their cycling stability is limited by intrinsic structural degradation and surface deterioration associated with the open metal-CN coordination network. Here, we present a synergistic strategy combining particle-level surface modification and electrode-level additive dispersion to enhance the performance and durability of manganese hexacyanoferrate. The controlled addition of ammonium persulfate forms a reconstructed surface layer that stabilizes the open framework during ion (de)intercalation. Acid-treated carbon (ATC) dispersed in the precursor improves nucleation during synthesis, as well as the electronic conductivity and charge transfer during electrode operation. The resulting PBA microcubes show excellent durability, sustaining stable cycling for 500 cycles at 1C. The feasibility of this approach was further demonstrated in a scaling-up attempt with higher reactant concentrations. The optimized PBA material delivers a high specific capacity of 140 mA•h•g⁻¹ at 0.1C, along with excellent rate capability, retaining 108.6 mA•h•g⁻¹ even at 10C.