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 TiO(2 )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.

Automated summary

Designing heterostructured hosts is crucial for enhancing the performance of lithium-sulfur batteries. In this study, ultrafine anatase and rutile TiO2 nanoparticle-modified macroporous carbon microspheres were synthesized. The TiO2/C heterointerfaces constructed by anatase TiO2 demonstrated a higher catalytic efficiency compared to rutile TiO2, leading to a high specific capacity and low capacity decay rate for the S@AT@MC electrodes.