First-principles insights into selenium and sulfur doping on Ti2CO2 MXene for mitigating the shuttle effect in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are promising next-generation energy storage devices due to their high energy density, cost-effectiveness, and environmental friendliness. However, their practical application is hindered by the shuttle effect of lithium polysulfides (Li2Sx) and the poor electrical conductivity of the sulfur cathode. In this study, we employ first-principles density functional theory calculations to investigate the effects of selenium (Se) or sulfur (S) doping on Ti2CO2 MXene as an anchoring material to mitigate these challenges. Our findings reveal that substituting oxygen with Se or S enhances the electronic conductivity of Ti₂CO₂ by transforming it into a metallic conductor. The adsorption energies of various Li2Sx clusters (x = 1, 2, 4, 6, 8) on the doped MXenes demonstrate significantly improved binding, particularly for low-sulfur content clusters, which is crucial for inhibiting the shuttle effect. Furthermore, charge transfer analysis confirms that Se or S doping enhances the interaction between Li2Sx and the MXene surface, promoting better electrochemical performance. These results establish Se or S doping as an effective strategy for optimizing MXene-based anchoring materials in high-performance Li-S batteries.