Rational design of ultra-dispersed TiO2/few-layered Ti3C2T MXene heterostructure for enhanced sodium storage

Ti 3 C 2 T x -based MXenes have become up-and-coming energy storage materials owing to their excellent physiochemical properties. However, the inadequate availability of Na + ​adsorption sites and unsatisfactory sodium storage performance hinder the application of Ti 3 C 2 T x -based electrodes in sodium-ion batteries (SIBs). Herein, the surface of few-layered Ti 3 C 2 T x was functionalized with ultra-dispersed TiO 2 nanoparticles (∼20 ​nm) to form an ultra-dispersed TiO 2 /few-layered Ti 3 C 2 T x heterostructure (UD-TiO 2 /f-Ti 3 C 2 T x ) via an in-situ sol-gel method. To further improve the electrochemical performance, a post-treatment process of calcination was also employed, which effectively removes the inert surface functional groups, especially F groups. Benefiting from the stronger Na + ​adsorption capability on TiO 2 compared to Ti 3 C 2 T x , expanded interlayer distance and increased electrical conductivity, the constructed UD-TiO 2 /f-Ti 3 C 2 T x electrode displays a remarkable capacity of 190 mAh g - 1 at 0.02 ​A ​g - 1 , which is over four times that of pristine f-Ti 3 C 2 T x (44 mAh g - 1 ). Moreover, the UD-TiO 2 /f-Ti 3 C 2 T x electrode delivers an excellent cyclability with 92% retention at 2 ​A ​g - 1 even after 10 ​000 cycles. This work offers an alternative strategy for the controllable fabrication of ultra-dispersed TiO 2 nanoparticles on the Ti 3 C 2 T x surface, and highlights the promise of the UD-TiO 2 /f-Ti 3 C 2 T x heterostructure as an anode material for SIBs, providing valuable insights into the development of high-performance Ti 3 C 2 T x -based electrodes.