Site-specific lithium adsorption and directional ion transport in Ti2CO2 MXenes: insights from nuclear magnetic resonance and climbing-image nudged elastic band calculations.

The development of advanced anode materials is critical for improving the performance of lithium-ion batteries. Ti2CO2 MXene, with its metallic conductivity and rich surface chemistry, has emerged as a promising candidate; however, the fundamental processes of lithium adsorption and diffusion remain insufficiently understood. In this work, we employ first-principles calculations combined with nuclear magnetic resonance (NMR) analysis and climbing-image nudged elastic band (NEB) simulations to investigate the lithiation mechanism of Ti2CO2. NMR shielding tensors reveal the evolution of local electronic environments, from anisotropic Ti-O-Li interactions at low lithium coverage to delocalized charge redistribution at higher lithiation, thereby stabilizing adsorption sites. NEB simulations further identify anisotropic diffusion pathways, with a dominant low-barrier channel (0.09-0.24 eV) that remains active even under high loading. These results demonstrate that Ti2CO2 provides both structural resilience and electronic conductivity, highlighting its potential as an efficient host material for next-generation lithium-ion batteries.