Highly crystalline Prussian blue/graphene composites for high-rate performance cathodes in Na-ion batteries

Abstract

We report the synthesis of highly crystalline Prussian Blue (PB) embedded in graphene oxide (GO) layers and its superior electrochemical properties. Highly crystalline PB is prepared from Fe₂O₃ nanoparticles anchored on GO (Fe₂O₃/GO). Regulated Fe³⁺-ion release and slow crystallization with [Fe(CN)₆] in the vicinity of Fe₂O₃/GO produce a GO-interconnected PB (HC-PB/GO) with fewer [Fe(CN)₆] vacancies and H₂O molecules. When compared with PB synthesized under identical conditions without GO, the HC-PB/GO delivers a noticeably higher reversible capacity and better cyclability as a cathode in Na-ion batteries (SIBs). The improvement in high-rate performance is rather striking. While the energy density of PB at a charge/discharge (C/D) rate of 2.0 A g⁻¹ is negligible, the HC-PB/GO delivers 280 mW h g⁻¹. The increase of electronic conduction and Na⁺ ion diffusion in HC-PB/GO contribute to a substantial improvement in rate capability.