Compressive-strain-engineered TiO2/rGO heterojunction polysulfide mediator

Abstract

The practical application of lithium-sulfur batteries (LSBs) is hindered by the polysulfide shuttle effect and sluggish redox kinetics. Herein, we report a compressive strain engineering strategy to develop a TiO2/reduced graphene oxide (rGO) heterostructure (TNGO) as a high-performance polysulfide mediator for separator modification. The introduced compressive strain in the TiO2 lattice, confirmed by structural characterizations, effectively enhances polysulfide chemisorption and accelerates Li+ diffusion. When coated on a polypropylene separator, the TNGO composite synergistically combines the conductive rGO network with the catalytically active, strained TiO2. This design simultaneously mitigates the shuttle effect and improves reaction kinetics. Consequently, the LSB with the TNGO-modified separator achieve a high initial capacity of 1072.7 mAh·g-1 at 1C and retain 409.9 mAh·g-1 after 1,000 cycles, with a low decay rate of 0.062% per cycle. Even with a high sulfur loading (4.32 mg·cm-2), the cells retain 82.3% of their capacity after 200 cycles at 0.1C. This work demonstrates compressive strain engineering as a novel and powerful strategy for separator modification in LSBs.