Titanium activation in Prussian Blue based electrodes for NA-ion batteries: a synthesis and electrochemical study

Sodium titanium hexacyanoferrate (TiHCF, Na0.86Ti0.73[Fe(CN)6]3H2O) is synthesized by a simple co-precipitation method in this study. Its crystal structure, chemical composition, and geometric/electronic structural information are investigated by X-ray powder diffraction (XRPD), microwave plasma-atomic emission spectroscopy (MP-AES), and X-ray absorption spectroscopy (XAS). The electroactivity of TiHCF as a host for Li-ion and Na-ion batteries is studied in organic electrolytes. The results demonstrate that TiHCF is a good positive electrode material for both Li-ion and Na-ion batteries. Surprisingly, however, the material shows better electrochemical performance as a Na-ion host, offering a capacity of 74 mAh g1 at C/20 and a 94.5% retention after 50 cycles. This is due to the activation of Ti towards the redox reaction, making TiHCF a good candidate electrode material for Na-ion batteries.