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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 Co3 O4 /TiO2 p-n junctions (p-Co3 O4 /n-TiO2 -HPs) are fabricated to implement the sequential catalysis of S8(solid) → Li2 S4(liquid) → Li2 S(solid) . Co3 O4 sheets physiochemically immobilize the pristine sulfur and ensure the rapid reduction of S8 to Li2 S4 , while TiO2 dots realize the effective precipitation of Li2 S, bridged by the directional migration of polysulfides from p-type Co3 O4 to n-type TiO2 attributed to the interfacial built-in electric field. As a result, the sulfur cathode coupled with p-Co3 O4 /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.
Li et al. (Sun,) studied this question.