In-situ adsorption and catalysis of polysulfide on Janus Ni₃Fe−Fe₂VO₄ heterostructure for Li − S batteries

The shuttling effect of lithium polysulfides (LiPSs) and the sluggish redox reaction of sulfur prevent the practical applications of lithium−sulfur (Li−S) batteries. Herein, a Janus Ni₃Fe−Fe₂VO₄ heterostructure with a one-to-one butted configuration on carbon black (Ni₃Fe−Fe₂VO₄/CB) is elaborately designed to realize the in-situ adsorption and catalysis of LiPSs. The special heterostructure shows a high concentration heterointerface and similar exposed surface area by optimizing the distribution and proportion of two kinds of active sites. Moreover, the covalent connection of Ni₃Fe and Fe₂VO₄ phases produces electron redistribution in the heterostructure which further increases the chemisorption and catalytic ability of Fe₂VO₄ and Ni₃Fe, respectively. It benefits the more efficient conversion for LiPSs. Battery with Ni₃Fe−Fe₂VO₄/CB decorated separators remains 983.6 mAh g⁻¹ after 500cycles at 0.2C, corresponding capacity decay rate of 0.028% per cycle, and high-rate capability of 877.5 mAh/g at 2.0C, which is 62.7% higher than battery with pristine polypropylene (PP) separators (539.5 mAh g⁻¹). Even at the low E/S ratio (5 μL mg⁻¹), it provides an excellent capacity decay rate of 0.038% per cycle over 500cycles, much lower than the pristine (0.109%). This work on heterostructure engineering offers an efficient spatial continuous reaction, which is valuable for integrating the adsorption and catalytic conversion processes for Li−S batteries.