In Situ Non-Topotactic Reconstruction-Induced Synergistic Active Centers for Polysulfide Cascade Catalysis

Most reported catalysts for lithium-sulfur battery can work for only one of the multiple elementary reactions, thereby resulting in the gradual enrichment of unconverted polysulfides at the catalytic centers and aggravating the shuttle effect. Herein, the concept of cascade catalysis based on a ternary heterostructure, which divides sulfur redox reactions into distinct steps by multiple catalytic centers, is proposed to realize the tandem reduction of Li2S8 to Li2S. As a proof of concept, the ternary heterostructure Na0.67Ni0.25Mn0.75O2(NNMO)-MnS2-Ni3S4 achieved by in situ non-topotactic electrochemical reconstruction successfully integrates three types of active centers into one structure to achieve cascade catalysis. More specifically, NNMO acts as an adsorption mediator to effectively capture polysulfides, MnS2 functions better in catalyzing the conversion of polysulfides into Li2S4 and Ni3S4 demonstrates an enhanced catalytic effect for Li2S precipitation. This synergistic cascade catalysis originates primarily from the dynamic energy-level matching between the metal d-band center and the lowest unoccupied molecular orbital of the polysulfides, affording appropriate molecular orbital hybridization and facile interfacial electron transition and thus endowing favorable sulfur reduction kinetics. Eventually, the NNMO-MnS2-Ni3S4/S composite electrode exhibits excellent rate performance and high restraining ability toward the polysulfide shuttle under long cycling, high sulfur loading and low electrolyte conditions.

Automated summary

A cascade catalysis concept based on a ternary heterostructure is proposed to achieve the tandem reduction of Li2S8 to Li2S. The ternary heterostructure Na0.67Ni0.25Mn0.75O2(NNMO)-MnS2-Ni3S4 successfully integrates three types of active centers into one structure to realize cascade catalysis. The NNMO-MnS2-Ni3S4/S composite electrode exhibits excellent rate performance and high restraining ability toward the polysulfide shuttle under long cycling, high sulfur loading and low electrolyte conditions.