Utilizing the Built-in Electric Field of p-n Junctions to Spatially Propel the Stepwise Polysulfide Conversion in Lithium-Sulfur Batteries

Integrating sulfur cathodes with effective catalysts to accelerate polysulfide conversion is a suitable way for overcoming the serious shuttling and sluggish conversion of polysulfides in lithium-sulfur batteries. However, because of the sharp differences in the redox reaction kinetics and complicated phase transformation of sulfur, a single-component catalyst cannot consistently accelerate the entire redox process. Herein, hierarchical and defect-rich Co3O4/TiO2 p-n junctions (p-Co3O4/n-TiO2-HPs) are fabricated to implement the sequential catalysis of S-8(solid) -> Li2S4(liquid) -> Li2S(solid). Co3O4 sheets physiochemically immobilize the pristine sulfur and ensure the rapid reduction of S-8 to Li2S4, while TiO2 dots realize the effective precipitation of Li2S, bridged by the directional migration of polysulfides from p-type Co3O4 to n-type TiO2 attributed to the interfacial built-in electric field. As a result, the sulfur cathode coupled with p-Co3O4/n-TiO2-HPs delivers long-term cycling stability with a low capacity decay of 0.07% per cycle after 500 cycles at 10 C. This study demonstrates the synergistic effect of the built-in electric field and heterostructures in spatially enhancing the stepwise conversion of polysulfides, which provides novel insights into the interfacial architecture for rationally regulating the polysulfide redox reactions.

Automated summary

Hierarchical and defect-rich Co3O4/TiO2 p-n junctions were fabricated to sequentially catalyze the conversion of sulfur in lithium-sulfur batteries, resulting in long-term cycling stability with low capacity decay. This study demonstrates the synergistic effect of built-in electric field and heterostructures in enhancing polysulfide conversion, providing novel insights for rational regulation of redox reactions.