Review of metal phosphides as electrocatalysts for accelerating sulfur redox reactions in lithium–sulfur batteries

Lithium-sulfur (Li-S) energy devices integrating the merits of lithium and sulfur are promising owing to their high capacity and remarkable energy density, but slow conversion kinetics and shuttling of sulfur species impede their practical utilization. Metal phosphides with strong chemical polarity and high catalytic activity have shown great potential as electrocatalysts to mitigate these issues. This review systematically summarizes the emerging use of metal phosphides in Li-S batteries, particularly in sulfur hosts, coating layers, and interlayers. The design/construction principles, detailed functions, and efficiencies in improving battery performance are then analyzed for representative metal phosphides. Neglected issues and remaining challenges are then identified and discussed, and future development directions are given. This work highlights the superiority of metal phosphides as electrocatalysts and paves the way for designing commercial Li-S batteries.