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

Abstract

The TiO 2 nanosheets constructed yolk-shell sulfur-TiO 2 (S@void@TiO 2 ) architecture with optimized inner voids demonstrates high-performance and ultralong-life for Li-S battery. • Designing TiO 2 nanosheets constructed yolk-shell TiO 2 (S@void@TiO 2 ) nanostructure for Li-S battery. • Verifying intense chemical interaction via the hybridization of Li 1 s, S 2p and O 2p orbitals in S@void@TiO 2. • Optimizing the inner voids for volume expansion to guarantee the cathode integrity. • Improving the electrolyte wettability and Li + kinetics in S@void@TiO 2. • Realizing high capacity and long cycle with a small capacity decay for Li-S battery. A TiO 2 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 TiO 2 nanosheets to form yolk-shell sulfur-TiO 2 (S@void@TiO 2 ) architecture with controllable inner voids, the S@void@TiO 2 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 TiO 2 with long-term cycling stability. Consequently, the optimized S@void@TiO 2 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 TiO 2 -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.