Rapid and solvent-free mechanochemical synthesis of Na iron hexacyanoferrate for high-performance Na-ion batteries

Sodium iron hexacyanoferrate (NaFeHCF) containing Fe as the only transition metal element has attained extensive interest for Na-ion batteries due to the low raw material cost and high resource abundance; however, the traditional solution-based synthesis methods, including coprecipitation and hydrothermal reaction, are usually time-consuming and difficult to control the interstitial water and Na content in the lattice, which puts a challenge on the high-efficiency and controllable preparation of NaFeHCF. Herein, we demonstrate a rapid and solvent-free mechanochemical route under the Ar atmosphere to synthesize Na1.59Fe[Fe(CN)6]0.95?0.051.92H2O cathode, which delivers an initial discharge capacity of-130 mA h g(-1 )at 0.2 ? and 118 mA h g(-1) at a high rate of 10 C. Besides, ex situ XRD confirms that NaFeHCF cathode experienced a phase transition from the initial cubic phase to Na-free cubic structure during the first charging process and followed by a reversible phase change between the monoclinic and Na-free cubic structures in the subsequent cycles. More impressively, the optimized NaFeHCF/NaTi2(PO4)(3) full cell reveals a decent capacity retention of 80% over 1000 cycles at 1 C, exhibiting a promising prospect in the practical application. Our current work sheds light on the high-efficient scalable production of highperformance NaFeHCF cathodes for Na-ion batteries via mechanochemical approach. (c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

In this study, NaFeHCF cathode material was successfully synthesized through a rapid and solvent-free mechanochemical method. The cathode exhibited excellent discharge performance at high rates and underwent a reversible phase transition process.