Honeycomb graphite network confined in biphasic TiO2 homojunction nanotubes as the sulfur host for advanced lithium sulfur batteries

Abstract

We designed a biphasic TiO₂ homojunction nanotube containing an N-doped honeycomb graphite network coated with by a carbon layer (HGN@TiO₂@C) as the sulfur host to improve the Li–S battery performance. Theoretical calculations and experiments demonstrated that the design of a high-conductivity TiO₂ homojunction with near-perfect lattice matching and rich interfaces/boundaries, accompanied by the conductive HGN inside the conductive carbon layer, effectively confines sulfur and offers additional buffer space. This design not only facilitates the effective conversion of LiPSs and enhances both electronic and ion conductivity but also improves the sulfur adsorption and catalytic properties, thereby boosting the kinetics of sulfur evolution reactions. Besides, the unique porous structure of HGN achieves an overall enhancement in S/HGN conductivity by providing a high specific surface area to load more sulfur and accommodate the volume changes occurring during the charge–discharge process. Benefiting from these synergistic effects, HGN@TiO₂@C exhibits high coulombic efficiency, outstanding rate performance, and superior cycling stability (601.7 mA h g⁻¹ for the fourth cycle and ≈626.8 mA h g⁻¹ after 200 cycles at 1C, corresponding to a capacity retention of ≈104.2%).