Recent advances and strategies of metal phosphides for accelerating polysulfide redox and regulating Li plating

Lithium-sulfur batteries (LSBs) are widely acknowledged as the most promising energy storage systems for the future, primarily due to their remarkably high theoretical energy density. Nonetheless, the advancement of LSBs encounters various hurdles, including the substantial expansion of the cathode material, inadequate conductivity of the active material S and discharge product Li2S, the evident shuttle effect of lithium polysulfide (LiPS), and the sluggish sulfur conversion kinetics. These challenges become particularly evident when handling high sulfur loading. The issue of uneven Li dendrite growth at the anode significantly affects the long-term functionality and safety of batteries. Consequently, there is a pressing requirement for battery designs that effectively tackle these challenges. Metal phosphide, owing to its remarkable catalytic activity and distinctive physicochemical properties, has been extensively investigated and is anticipated to serve as a bifunctional material in LSBs systems. By manipulating the composition of cations, it is possible to obtain monometallic phosphide, bimetallic phosphide, and trimetallic phosphide through tailored design approaches. It has been found that metal phosphide catalysts can effectively adsorb soluble LiPS and catalyze its rapid conversion. Moreover, the synthesis of composite materials by incorporating metal phosphides with other compounds results in a synergistic effect that significantly improves catalytic performance. This study offers a thorough overview of the diverse applications of metal phosphides in enhancing cathode sulfur support materials, modifying separators, and protecting lithium anodes. The significance of metal phosphides in facilitating the anchoring of lithium polysulfides, improving electrochemical reaction rates, facilitating the nucleation and dissolution of lithium sulfide, enhancing electron and ion transport, and promoting uniform lithium deposition was underscored. Additionally, the obstacles and potential opportunities for metal phosphides in future lithium-sulfur batteries are examined, along with their practical utility.