Abstract
The andante electrocatalytic conversion and grievous shuttle effect of lithium polysulfides (LiPSs) lead to stagnant applications of lithium-sulfur (Li-S) batteries. Plentiful catalysts such as ZnS-FeS heterostructures have been employed to solve those problems. However, the mechanism of this heterostructures on sulfur reduction reaction (SRR) especially the conversion of Li2S2 to Li2S (Li2S2RR) and Li+ migration has not been revealed. Herein, a ZnS-FeS heterostructures embedded in hierarchical porous carbon (ZnS-FeS/HPC) was demonstrated that can act as effective catalyst to accelerate Li2S2RR and promote the Li+ diffusion simultaneously. This improvement can be attributed to the moderate adsorption energy and lower d-band center of the heterostructures to reaction intermediates. Moreover, with both homogeneous porous structure and abundant polarity sites, the modified separator using ZnS-FeS/HPC was endowed with selectivity to promote uniform Li+ flux and migration, as well as impede the dendritic Li growth and LiPSs shuttling. Benefited from above advantages, the batteries exhibited superior initial capacity of 1674.7 mAh/g (current density: 0.2C). Even at 3C, the batteries can cycle steadily for over 1500 cycles along with ultralow rate of capacity decay (0.044 %). This work opens up a new insight to explore bidirectional catalyst for realizing remarkable performance Li-S batteries.
Published Version
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