Active zinc selenide nanocatalysts induced by crystal phase engineering for enhanced sulfur redox kinetics

• The phase composition of ZnSe electrocatalysts was controlled through crystal phase engineering. • The non-conventional hexagonal phase was incorporated into the cubic-phase ZnSe host (HC-ZnSe). • The obtained HC-ZnSe can effectively confine and catalyze the conversion of polysulfides. • The assembled Li-S batteries with HC-ZnSe modified separator achieve rate capability and long-cycle stability. 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 SeO 2 , 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. This work modulates the phase composition of zinc selenide through crystal phase engineering, successfully introducing the unconventional hexagonal phase into the cubic ZnSe host. Such an interesting structure can not only effectively adsorb lithium polysulfides but also accelerate their redox kinetics, thereby significantly improving the long-term cycling stability of lithium-sulfur batteries.