Multicomponent synergy and simultaneous improvement of catalytic conversion and chemisorption of polysulfides via CoFe/FeN0.0324/TiN modified Li-S battery separator

Lithium-sulfur (Li-S) batteries present tremendous potential in promising high energy storage systems because of their high energy density and specific capacity. However, the shuttle effect and slow reaction kinetics of the intermediate lithium polysulfide (LiPSs) result in fast capacity fading. Herein, multicomponent synergy nitrogen-doped carbon nanotube (CNT) framework dotted by CoFe/FeN 0.0324 /TiN heterostructure (CoFe/FeN 0.0324 /TiN@N-CNT) were developed and prepared by in-situ nitridation approach as polysulfide mediator to simultaneously realize physicochemical adsorption and catalytic conversion of polysulfide. Transition metal nitrides, such as FeN 0.0324 , are known for their polar surfaces that can chemically adsorb polysulfides efficiently. Additionally, CoFe and TiN have been shown to catalyze polysulfide redox reactions. This understanding paves the way for the development of heterostructured CoFe/FeN 0.0324 /TiN nanoparticles that significantly enhance the immobilization, diffusion, and transformation of polysulfides. Moreover, nitrogen-doped carbon nanotubes (CNTs) decorated with bimetallic CoFe afford intriguing benefits. The CoFe alloy not only facilitates the in-situ growth of CNTs but also contributes to prominent Li + /electron conductivity. Together, CoFe and CNTs provide substantial physical confinement and catalytic sites, thereby accelerating redox kinetics and effectively mitigating the shuttle effect. Owing to these advantages, CoFe/FeN 0.0324 /TiN@N-CNT separators exhibit remarkable electrochemical properties including superior rate capacity of 738 mAh g −1 at 3C, high reversible capacity of 708 mAh g −1 at 0.5C after 400 cycles and 607 mAh g −1 at 1C after 1000 cycles with per cycle declining rate of 0.09 % and 0.048 %, respectively, and ultralong cycle life at 4C after 1000 cycle. Even with a relatively high sulfur loading of 2.3 mg, the modified batteries still exhibit a satisfactory reversible capacity at 0.5C. This work paves a unique avenue combined prudent spacial framework with heterogeneous synergy strategy for manufacturing high-energy–density Li-S batteries.