A simple, efficient, fluorine-free synthesis method of MXene/Ti3C2Tx anode through molten salt etching for sodium-ion batteries

MXenes are mentioned in many applications due to their unique properties. However, the traditional etching method has a lengthy synthesis time, dangerous process, and high cost. Molten salt etching is not only short in time but also safe and simple, laying a good foundation for industrialization. Here, we compare the traditional F-containing etching method with the molten salt etching method. Transmission electron microscopy elemental mapping images and X-ray photoelectron spectroscopy show that the Ti₃C₂T_x surface end of traditional etching is terminated by –F, while the Ti₃C₂T_x surface end of molten salt etching is terminated by –Cl. Finally, the sodium-ion batteries are fabricated and the performance difference of the three etching methods is compared. The results show that the capacity of 102.1 mAh g^–1 can still be reached when the molten salt etching MXene material returns to 0.1 A g^–1 after the current density of 5 A g^–1. After 500 cycles at 1 A g^–1, there is no significant loss of capacity and the Coulomb efficiency is close to 100%. This work describes that molten salt etching MXene has comparable sodium storage capacity to conventional F-containing etched MXene, making it a potential candidate for the production of large-scale sodium-ion batteries.