Earth-Abundant Titanium Dioxide-Mesoporous Carbon as a Dual-Confinement Host for Lithium–Sulfur Batteries

Lithium–sulfur (Li-S) batteries are attractive next-generation energy storage systems owing to their high theoretical energy density of 2600 Wh/kg and earth-abundant, eco-friendly sulfur. However, their practical application is hindered by the insulating nature of sulfur, large volume changes during cycling, and the polysulfide shuttle effect. Herein, we designed a dual-confinement cathode architecture combining mesoporous carbon with earth-abundant titanium dioxide (TiO2). Sulfur composites with 70 wt% sulfur loading were prepared. Structural characterization via X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) analysis showed a well-developed mesoporous network in KB but not in TiO2. XRD confirmed that sulfur and anatase TiO2 coexist in the composites, with weaker sulfur peaks in the mixed host. UV-vis absorption spectra showed that nano-TiO2 removes more Li2S6 from solution than KB. Electrochemical evaluations revealed that the dual-confinement composite architecture balances the fast redox kinetics of carbon against the polysulfide affinity of TiO2. Consequently, the composite achieved a high initial discharge capacity of 1300.89 mAh/g at 0.1 C and stable cycling over 100 cycles at 0.5 C. Furthermore, ex situ XRD analysis revealed nearly complete sulfur conversion while maintaining TiO2 structural integrity. These results demonstrate an optimal balance between electronic conductivity and polysulfide mitigation via a sustainable material strategy.