Anatase/Rutile Phases Regulating TiO₂/C Heterointerfaces for Enhanced Polysulfide Conversion in Sulfur Cathodes

Designing heterostructured hosts is one of the promising strategies to mitigate the shuttle effect of dissolved lithium polysulfides (LiPSs) and accelerate the redox reaction kinetics between LiPSs and Li₂S, which could boost the electrochemical performance of lithium-sulfur batteries (LSBs). Among such hosts, polar TiO₂ and conductive porous carbon are an optimal and common combination. However, there exist few investigations to systematically evaluate the effect of the TiO₂ phase structure (i.e., anatase and rutile) of the TiO₂/C heterointerfaces on the catalytic efficiency toward the LiPS conversion. Herein, ultrafine anatase and rutile TiO₂ nanoparticle (3-5 nm) modified macroporous carbon microspheres (AT@MC and RT@MC) were synthesized as the sulfur hosts, respectively. The smaller the size of the TiO₂ nanoparticles, the greater the TiO₂/C heterointerfaces. And both experimental tests and theoretical calculations implied that, compared with rutile TiO₂, the TiO₂/C heterointerfaces constructed by anatase TiO₂ demonstrated a higher catalytic efficiency due to the stronger absorbability toward LiPSs and the lower energy barriers during the electrochemical process. As a result, the S@AT@MC electrodes delivered a high specific capacity and a capacity decay rate of 0.056% per cycle for 500 cycles. This work furnishes guidance on the design of TiO₂-based heterostructured hosts for high-performance LSBs.