The Catalyst Design for Lithium-Sulfur Batteries: Roles and Routes

Lithium-sulfur battery is a promising candidate for next-generation high energy density batteries due to its ultrahigh theoretical energy density. However, it suffers from low sulfur utilization, fast capacity decay, and the notorious "shuttle effect" of lithium polysulfides (LiPSs) due to the sluggish reaction kinetics, which severely restrict its practical applications. Using the electrocatalyst can accelerate the redox reactions between sulfur, LiPSs and Li₂ S and suppress the shuttling of LiPSs, and thus, it is a promising strategy to solve the above problems, enabling the battery with high energy density and long cycling stability. In this personal account, we discuss the catalyst design for lithium-sulfur batteries according to the sulfur reduction reaction (SRR) and sulfur evolution reaction (SER) in the discharging and charging processes. The catalytic effects for each step in SRR and SER are highlighted and the homogenous catalysts, the selective catalysts, and the bidirectional catalysts are discussed, which can help guide the rational design of the catalysts and practical applications of lithium-sulfur batteries.