Environmentally friendly, inexpensive iron-titanium tunneled oxide anodes for Na-ion batteries

Within this paper, we investigate the electrochemical performance of NaFeTiO4, Na0.9Fe0.9Ti1.1O4, Na0.8Fe0.8Ti1.1O4 tunneled structured anodes for Na-ion batteries. Sol-gel synthesis enables to obtain anode materials characterized by improved morphology leading to enhanced electrochemical behavior in Na-ion batteries. Impedance spectroscopy and UV-VIS measurements reveal that electronic component dominates in total electrical conductivity, which is one order of magnitude higher for Na0.9Fe0.9Ti1.1O4, Na0.9Fe0.9Ti1.1O4 in comparison to NaFeTiO4. Among the studied materials, Na0.9Fe0.9Ti1.1O4 possesses the highest charge capacity of 180 mAh g(-1) during the first cycle at C/20 and can retain 80% of the initial capacity after 30 cycles with an average charging voltage of 1.3 V vs. Na+/Na. Experiments in temperatures from -20 degrees C to +60 degrees C reveal that Na0.9Fe0.9Ti1.1O4 preserve a significant fraction of its capacity: 70 mAh g(-1) at -20 degrees C and 177 mAh g(-1) at 60 degrees C. Application of ether-based diglyme solvents instead of ester-based results in reduced irreversible reactions during the initial discharge-charge cycle, better performance under higher loads, and lower charge transfer and SEI resistance. The results prove that Na0.9Fe0.9Ti1.1O4 is an auspicious material for future low-cost Na-ion batteries with stable performance in a wide temperature range. (C) 2021 The Authors. Published by Elsevier Ltd.

Automated summary

In this study, the electrochemical performance of NaFeTiO4, Na0.9Fe0.9Ti1.1O4, and Na0.8Fe0.8Ti1.1O4 tunneled structured anodes for Na-ion batteries was investigated. The sol-gel synthesis method was employed to obtain anode materials with improved morphology, resulting in enhanced electrochemical behavior in Na-ion batteries. Impedance spectroscopy and UV-VIS measurements showed that the electronic component dominated the total electrical conductivity, which was one order of magnitude higher for Na0.9Fe0.9Ti1.1O4 and Na0.9Fe0.9Ti1.1O4 compared to NaFeTiO4. Among the studied materials, Na0.9Fe0.9Ti1.1O4 exhibited the highest charge capacity of 180 mAh g(-1) during the first cycle at C/20 and retained 80% of the initial capacity after 30 cycles with an average charging voltage of 1.3 V vs. Na+/Na. Experimental results at temperatures ranging from -20 degrees C to +60 degrees C showed that Na0.9Fe0.9Ti1.1O4 maintained a significant portion of its capacity, with 70 mAh g(-1) at -20 degrees C and 177 mAh g(-1) at 60 degrees C. The use of ether-based diglyme solvents instead of ester-based solvents reduced irreversible reactions during the initial discharge-charge cycle, improved performance under higher loads, and decreased charge transfer and solid electrolyte interface resistance. These findings demonstrate that Na0.9Fe0.9Ti1.1O4 is a promising material for future low-cost Na-ion batteries with stable performance over a wide temperature range.