The cobalt atom protection layers in-situ anchored titanium carbide with controllable interlayer spacing towards stable and fast lithium ions storage

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 degrees 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 x 10(-7) cm(2) s(-1) in Li+ storage process. Furthermore, the 45, 65 and 85-Cofin-Ti3C2 exhibit lower SEI resistances (R-SEI) as 1.45 +/- 0.01, 1.26 +/- 0.01 and 1.83 +/- 0.01 Omega compared with the R-SEI of Ti3C2 (5.18 +/- 0.01 Omega), suggesting the x-Cofin-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. (C) 2021 Elsevier Inc. All rights reserved.

Automated summary

This study investigates the use of Co atom protection layers to address the self-stacking and consumption issues in MXenes, a type of two-dimensional nanomaterials used for Li+ storage. The Co atom layers not only prevent self-stacking and expand the interlayer spacing of Ti3C2, but also reduce the consumption of Li+ and electrolyte by forming a thin solid electrolyte interphase (SEI) film. The findings show that 65-Co/m-Ti3C2 exhibits the best specific capacity and rate capability, attributed to its superior diffusion coefficient in Li+ storage process. The addition of Co atom protection layers provides an approach to expand interlayer spacing and protect 2D nanomaterials.