Steering Sulfur Reduction Pathways via Cisplatin Enables High Performance in Lithium‐Sulfur Batteries

The sulfur reduction reaction (SRR) is an attractive 16‐electron transfer process that endows Li‐S batteries with a theoretical capacity of 1,672 mAh g‐1. However, the slow kinetics and complex pathways of the SRR cause the shuttling of soluble polysulfides (PSs), thus fast capacity fading. Here, we report using cisplatin (cis‐Pt) as a novel mediator to improve the SRR kinetics and a molecular probe to identify the SRR pathways. We show that cis‐Pt with a reductive Pt2+ center can directly slice the S‐S bonds of PSs, leading to enhanced charge transfer kinetics, guided SRR pathways, and depth conversion of PSs to Li2S. With cis‐Pt added, Li‐S coin cells deliver a maximum specific capacity of 1,437 mAh g‐1 and a capacity decay of 0.017% per cycle after 1000 cycles, while a pouch cell with a practical electrolyte‐sulfur ratio (2.5 μl mg‐1) exhibits a high energy density of 318.8 Wh kg‐1. Our mechanistic studies reveal that cis‐Pt steers the cathodic SRR pathways by generating redox active cis‐Pt/PSs complexes, enabling the replacement of the sluggish SRR with a faster redox cycling of Pt4+/Pt2+ pairs. These findings provide insights into the rational design of functional mediators for tackling the cathodic challenges inside Li‐S batteries.