Utilizing the Built-in Electric Field of p-n Junctions to Spatially Propel the Stepwise Polysulfide Conversion in Lithium-Sulfur Batteries.
basic_science · Level V
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- Record sourced from PubMed, PMID 34632643.
- Also identified by DOI 10.1002/adma.202105067.
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Abstract
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 Co<sub>3</sub> O<sub>4</sub> /TiO<sub>2</sub> p-n junctions (p-Co<sub>3</sub> O<sub>4</sub> /n-TiO<sub>2</sub> -HPs) are fabricated to implement the sequential catalysis of S<sub>8(solid)</sub> → Li<sub>2</sub> S<sub>4(liquid)</sub> → Li<sub>2</sub> S<sub>(solid)</sub> . Co<sub>3</sub> O<sub>4</sub> sheets physiochemically immobilize the pristine sulfur and ensure the rapid reduction of S<sub>8</sub> to Li<sub>2</sub> S<sub>4</sub> , while TiO<sub>2</sub> dots realize the effective precipitation of Li<sub>2</sub> S, bridged by the directional migration of polysulfides from p-type Co<sub>3</sub> O<sub>4</sub> to n-type TiO<sub>2</sub> attributed to the interfacial built-in electric field. As a result, the sulfur cathode coupled with p-Co<sub>3</sub> O<sub>4</sub> /n-TiO<sub>2</sub> -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.