Variation in the interface strength of silicon with surface engineered Ti3C2 MXenes

Abstract

Current advancements in battery technologies require electrodes to combine high-performance active materials such as Silicon (Si) with two-dimensional materials such as transition metal carbides (MXenes) for prolonged cycle stability and enhanced electrochemical performance. More so, it is the interface between these materials, which is the nexus for their applicatory success. Herein, the interface strength variations between amorphous Si and Ti₃C₂T_x MXenes are determined as the MXene surface functional groups (T_x) are changed using first principles calculations. Si is interfaced with three Ti₃C₂ MXene substrates having surface −OH, −OH and −O mixed, and −F functional groups. Density functional theory (DFT) results reveal that completely hydroxylated Ti₃C₂ has the highest interface strength of 0.6 J m⁻² with amorphous Si. This interface strength value drops as the proportion of surface −O and −F groups increases. Additional analysis of electron redistribution and charge separation across the interface is provided for a complete understanding of underlying physico-chemical factors affecting the surface chemistry and resultant interface strength values. The presented comprehensive analysis of the interface aims to develop sophisticated MXene based electrodes by their targeted surface engineering.