Novel synthesis and electrochemical properties of perovskite-type NaFeF3 for a sodium-ion battery

Highly crystallized perovskite-type NaFeF3 has been investigated as the cathode for sodium-ion batteries through the roll-quench method. In the charge-discharge measurement, the first discharge capacity was 197 mAh g(-1) at a rate of 0.076 mA cm(-2) between 1.5 V and 4.5 V. Reversible Fe2+/Fe3+ redox reaction on cycle was confirmed by XPS. The ex situ XRD measurements for charged or discharged NaFeF3 pellets revealed the reversible vibration on cycle, due to the structure strength and flexibility of the corner-sharing matrix. The peak intensities of (1 1 2) and (0 0 4) were changed with accompanying insertion/extraction of sodium, suggesting the extracted sodium has returned to the original 4c site on discharge. (C) 2011 Elsevier B.V. All rights reserved.