Optimizing inner voids in yolk-shell TiO₂ nanostructure for high-performance and ultralong-life lithium-sulfur batteries

A TiO₂ nanosheets constructed yolk-shell architecture with tunable inner voids is designed and prepared as sulfur host for high-performance and ultralong-life Li-S battery. With the integration of TiO₂ nanosheets to form yolk-shell sulfur-TiO₂ (S@void@TiO₂) architecture with controllable inner voids, the S@void@TiO₂ composite with optimized inner voids provides sufficient contacting sites to improve the utilization of insulating sulfur and allows sulfur to freely expand without destroying the electrode. In particular, the density functional theory (DFT) calculations from molecular level reveal that the hybridization of Li 1s, S 2p and O 2p orbitals ensures the effective chemisorption between polysulfides and TiO₂ with long-term cycling stability. Consequently, the optimized S@void@TiO₂ electrode maintains a capacity of 766 mAhg⁻¹ after 1000 cycles at 0.2C. Even at 2C for 400 cycles, the capacity still retains at 511 mAhg⁻¹, representing the best results of TiO₂-based nanostructures for Li-S batteries. This work illustrates that carefully design novel yolk-shell structure is important to address the shortages of sulfur-based cathodes for advanced Li-S battery.