Strain and solvation effects on Ti3C2O–TiN heterostructures as bifunctional electrocatalysts for Li–S batteries: a first-principles study

Abstract

Lithium–sulfur (Li–S) batteries are widely considered to be the most promising next-generation rechargeable energy storage systems due to their ultrahigh theoretical energy density. However, their practical deployment is severely hindered by the shuttle effect and sluggish redox kinetics. Here, we propose a 2D Ti₃C₂O–TiN heterostructure as a bifunctional electrocatalyst. Furthermore, considering the volume change of the cathode during charge–discharge cycles, strain engineering was employed to simulate the performance effects induced by this structural change. Based on density functional theory (DFT) calculations, we systematically investigated the sulfur immobilization and kinetic catalytic performance of the Ti₃C₂O–TiN heterostructure under various biaxial strain conditions. Our results reveal that the Ti₃C₂O–TiN heterostructure maintains strong anchoring capability for LiPSs and exhibits high catalytic activity under both compressive and tensile strains. Compressive strain enhances the interaction between LiPSs and the substrate, while tensile strain significantly promotes the decomposition of Li₂S and diffusion of Li⁺. These effects are primarily attributed to strain-induced modulation of the local electrochemical reactivity and the strength of the Li–S bonds. Furthermore, solvation significantly alters the anchoring and catalytic behavior, shifting the Li₂S₂ → Li₂S conversion pathway from the Li₃S₂ to the LiS intermediate. Our study provides valuable theoretical insights into the future development of high-performance catalytic cathode materials for Li–S batteries.