Structure and surface modification of MXene for efficient Li/K-ion storage

In this paper, three-dimensional (3D) hollow Ti3C2Tx MXene tubes (HTCTs) with more –O terminal groups and fewer –F groups are successfully prepared via the template-oriented electrostatic self-assembly and the subsequent annealing treatment. The obtained 3D hollow structure with large specific surface area, unique porous structure, and enlarged interlayer spacing could prevent the re-stacking of two-dimensional (2D) sheets and shorten the diffusion pathway of ions. Furthermore, density functional theory (DFT) calculations and electrochemical tests reveal that Ti3C2O2 MXene possesses higher adsorption ability and lower diffusion barrier for K+ and Li+ compared to Ti3C2 MXene dominated by –F terminal groups. Benefiting from the synergistic effect of the structural design and surface modification, the as-prepared 3D HTCTs exhibit excellent electrochemical performance as anodes for K+ and Li+ storage compared with 2D Ti3C2Tx sheets (TCSs).