Tailoring the growth of iron hexacyanoferrates for high-performance cathode of sodium-ion batteries

Iron hexacyanoferrate (FeHCF) is regarded as a promising cathode material of sodium-ion batteries (SIBs) due to the merits of easy preparation, low cost and three-dimensional open framework. However, the practical application of FeHCF is highly restricted by the intrinsic [Fe(CN)₆]^4- vacancy and coordinated water as well as nanoscale particles. Herein, sodium citrate is introduced to mediate the drawbacks of FeHCF, resulting in microscale particles with less water content. Accordingly, the modified sample, FeHCF-3, achieved the performance of 92 mA h g⁻¹ at 100 mA g⁻¹ and 80 % capacity retention after 300 cycles. Furthermore, an optimal iron hexacyanoferrate (FeHCF-H-2) with high-salt-concentration preparation is designed and performs a good reversibility of 96 mA h g⁻¹ after 700 cycles at 100 mA g⁻¹. Such strategy may drive the application of high-tap, low-defect and stable cathode for SIBs.