Abstract
The shuttle effect of lithium polysulfides (LiPSs) and the slow sulfur reduction kinetics seriously hinder the practical application of lithium-sulfur (Li-S) batteries, and the development of efficient electrocatalysts is an effective strategy to solve the above problems. Controlling the phase composition of electrocatalysts through crystal phase engineering is a useful strategy to improve the catalytic activity of electrocatalysts. Herein, crystal phase engineering is reported by regulating the phase composition of zinc selenide (ZnSe) to enhance the electrochemical performance of Li-S batteries. By tuning the ratio of ZIF-8 to SeO2, the unconventional hexagonal phase was successfully introduced into the cubic ZnSe host (HC-ZnSe). Experimental studies and analyses have shown that HC-ZnSe can capture LiPSs and accelerate sulfur conversion more effectively than pure cubic ZnSe. As a result, the Li-S batteries with the optimized HC-ZnSe-4 modified separator exhibit an improved rate performance of 612 mAh g−1 at 2 C, and long-term cycling stability with 0.034% capacity decay per cycle over 1000 cycles at 1 C. Moreover, a high reversible areal capacity of 6.1 mAh cm−2 can be achieved over 200 cycles even with sulfur loading as high as 6.8 mg cm−2. This work demonstrates that crystal phase engineering is a promising strategy for optimizing catalyst performance for Li-S batteries.