The cobalt atom protection layers in-situ anchored titanium carbide with controllable interlayer spacing towards...

MXenes are the typical ions insertion-type two-dimensional (2D) nanomaterials, have attracted extensive attention in the Li⁺ storage field. However, the self-stacking of layered structure and the consumption of electrolyte during the process of charge/discharge will limit the Li⁺ diffusion dynamics, rate capability and capacity of MXenes. Herein, a Co atom protection layers with electrochemical nonreactivity were anchored on/in the surface/interlayer of titanium carbide (Ti₃C₂) by in-situ thermal anchoring (x-Co/m-Ti₃C₂, x  = 45, 65 and 85), which can not only avoid the self-stacking and expand the interlayer spacing of Ti₃C₂ but also reduce the consumption of Li⁺ and electrolyte by forming the thin solid electrolyte interphase (SEI) film. The interlayer spacing of Ti₃C₂ can be expanded from 0.98 to 1.21, 1.36 and 1.33 nm when the anchoring temperatures are 45, 65 and 85 °C due to the pillaring effects of Co atom layers, in where the 65-Co/m-Ti₃C₂ can achieve the best specific capacity and rate capability attributed to its superior diffusion coefficient of 8.8 × 10^-7 cm² s^-1 in Li⁺ storage process. Furthermore, the 45, 65 and 85-Co/m-Ti₃C₂ exhibit lower SEI resistances (R_SEI) as 1.45 ± 0.01, 1.26 ± 0.01 and 1.83 ± 0.01 Ω compared with the R_SEI of Ti₃C₂ (5.18 ± 0.01 Ω), suggesting the x-Co/m-Ti₃C₂ demonstrates a thin SEI film due to the protection of Co atom layers. The findings propose a Co atom protection layers with electrochemical nonreactivity, not only giving an approach to expand the interlayer spacing, but also providing a protection strategy for 2D nanomaterials.