A review of metal phosphides with catalytic effects in Li-S batteries: boosting the redox kinetics

Lithium-sulfur batteries (Li-S batteries) are being widely studied as promising energy-storage solutions for the next generation owing to their excellent properties including high energy density, eco-friendliness, and low cost. Nevertheless, drawbacks, especially the severe "shuttle effect" and slow transformation of polysulfides, hinder the road to commercialization of Li-S batteries. The functional utilization of metal compounds in Li-S batteries has been verified, such as enhancing the conductivity, adsorption of lithium polysulfides (LPSs) and improving the kinetics of electrode processes. Benefiting from the outstanding catalytic capability and relatively good conductivity, metal phosphides have gradually received intense attention over the past few years. Consequently, significant progress has been achieved in the optimization of phosphides for Li-S batteries in recent years. This review introduces the application of metal phosphides in Li-S batteries from the aspects of their own characteristics, material structure design, and material interface control. The aim of this review is to enhance the understanding of the operational mechanism of metal phosphides and provide guidance for the development of Li-S batteries.