3D interconnected N-doped graphene architecture encapsulated with oxygen-deficient TiO2 nanotube array: synergism of oxygen vacancy and carbon materials on enhanced sulfur conversion and catalytic activity of TiO2 nanotube array in Li–S batteries

Abstract

The main challenges to Li–S battery use include poor conductivity, the shuttling effect, and slow LiPS transition. In this work, a 3D framework of N-doped graphene interconnected with defect-rich TiO₂ nanotubes acts as a sulfur host. A narrow TiO₂ nanotube reduces lithium-ion diffusion length and facilitates fast charge transport. The unique 3D porous nanostructure holds a wide range of sulfur species and provides optimal pathways for electrolyte penetration. It also counters volume expansion during cycling and serves as a platform for the successful absorption of LiPSs. The TiO₂ nanowire with oxygen vacancy/N-doped graphene aerogel/sulfur (S-OVTNW/NGA) electrode has a small aspect ratio and is attached to graphene layers, which anchors LiPSs through a strong chemical interaction. Oxygen deficiency boosts electrical conductivity, reduces LiPS flow into the electrolyte, improves catalytic performance, and speeds up LiPS transformation. This design provides excellent electrochemical performance. The cathode has a notable primary specific capacity of 1370.2 mAh g⁻¹ at J = 0.2 C, with a sulfur ratio of 80%. Following 100 cycles, the observed capacity of the specimen remains at 879.2 mAh g⁻¹, signifying a retention rate of 66.5%. Its capacity of 635.5 mAh g⁻¹ under 4 C shows its excellent rate performance. The findings may accelerate the development of electrode materials for lithium–sulfur (Li–S) batteries that are more efficient and cost-effective.