Mesoporous amorphous FeOF nanococoons for high-rate and long-life rechargeable sodium-ion batteriesElectronic supplementary information (ESI) available. See DOI: 10.1039/c5ta04288g

• Main Authors: Fu, Shi Yan, Li, Yuan Zhi, Chu, Wei, Yang, Yi Mei, Tong, Dong Ge, Le Zeng, Qing
• Format: Article
• Language: English
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c5ta04288g

A novel solution plasma processing approach was developed to synthesize mesoporous amorphous FeOF nanococoons on a large scale via using NaF and FeCl 3 · x H 2 O as the precursors, and CO 2 released from the hydrolysis of urea as the growth director. The obtained mesoporous amorphous FeOF nanococoons deliver a reversible capacity of 238.9 mA h g −1 at a current rate of 1 A g −1 and show almost no degradation, even after 3000 cycles by adopting the optimized 1.0 M sodium trifluoromethanesulfonate (NaTFSA) in triglyme (TGM) as the electrolyte and tuning the cut-off voltage to 1.3 V. Furthermore, the nanococoons exhibit a capacity of 190.4 mA h g −1 at an ultrahigh current density of 20 A g −1 because of the coexisting pseudocapacitance-type reaction. Meanwhile, a commercial 18650-type battery was fabricated that exhibited a stable discharge capacity of 4897 mA h at 4 A for 300 cycles, which allows for consideration of this type of room-temperature battery in commercial utilization. The superior electrochemical performance of the mesoporous amorphous FeOF nanococoons is because of the collaboration of the optimized electrolyte, controlling the terminal voltage to 1.3 V, and their particular nanostructure, which significantly improve the ionic and electronic transport and intercalation kinetics of Na ions. Mesoporous amorphous FeOF nanococoons exhibited high rate performance and long life as cathode materials for sodium-ion batteries.