M‑Site Vacancy-Mediated Adsorption and Diffusion of Sodium on Ti₂CO₂ MXene

MXenes is a promising electrode material for Na ion batteries. To achieve better electrode performance in different aspects, we provide theoretical insight into vacancy engineering of a common MXene, Ti₂CO₂. We find that the vacancy changes conductivity of Ti₂CO₂, gives rise to stronger Na ion adsorption, and increases the capacity by introducing more accommodation for Na ion. Vacancy-affected Na ion diffusion is also investigated, which shows different trends according to its relative position to vacancy. The present results not only provide a fundamental understanding of vacancy in MXene but also shed some light on the possible strategy for improving the performance of MXene as electrode material through vacancy engineering.