Rechargeable sodium-ion battery based on a cathode of copper hexacyanoferrate

In this work, the performance of copper (II) hexacyanoferrate(III) (CuHCF) as a cathode material for sodium-ion batteries was studied. The compound was synthesized by a precipitation reaction in aqueous solution in a closed system. The morphology and structure show nanoparticles agglomerated with sizes ranging between 40 and 70 nm and a crystalline phase with a cubic structure, respectively. The material exhibited a stable performance with a working potential of around 3.4 V vs. Na⁺/Na. The gravimetric capacity obtained is close to 30 mAh g⁻¹ for 100 cycles at a rate of C/20, which is around half of the capacity for CuHCF when it encounters water in its structure, e.g., zeolite-type (60 mAh g⁻¹), which is less than the theoretical capacity for this material (85.1 mAh g⁻¹). CuHCF could be a promising cathode material for sodium-ion batteries considering its electrochemical performance.