High-quality Fe4[Fe(CN)6]3 Nanocubes: Synthesis and Electrochemical Performance as Cathode Material for Aqueous Sodium-ion Battery

High-quality Fe-4[Fe(CN)(6)](3) (HQ-FeHCF) nanocubes were synthesized by a simple hydrothermal method. Its structure, morphology and water content are characterized. Fe-4[Fe(CN)(6)](3) exhibits regular cubic shape with a uniform size of ca. 500 nm, which belongs to the face-centered cubic phase. Fe-4[Fe(CN)(6)](3) shows discharge capacities of 124, 118, 105, 94, 83, 74 and 64 mAh.g(-1) at 1C, 2C, 5C, 10C, 20C, 30C and 40C rate, respectively, in the aqueous ternary electrolyte of NaClO4-H2O-Polyethylene glycol. Its capacity retention remains 100% after 500 charge/discharge cycles at the rate of 5C. The full battery with Fe-4[Fe(CN)(6)](3) as cathode and NaTi2(PO4)(3) as anode was fabricated, which delivers a specific energy density of 126 Wh.kg(-1) (based on the active electrode materials) with a voltage output of 1.9 V. Furthermore, 92% of its initial discharge capacity retains after 140 charge/discharge cycles at a rate of 5C, and its Coulomb efficiency is close to 100%.