Binary Metal Alloy Electrocatalyst Synergistically Accelerates the Bidirectional Polysulfide Conversions in Lithium–Sulfur Batteries

The sluggish redox kinetics of polysulfides and the resulting shuttle effect remain significant challenges for the practical utilization of lithium-sulfur (Li-S) batteries. To address the unidirectional catalytic limitations of conventional electrocatalysts, we herein report a binary metal (CoNi) alloy embedded in a carbon matrix on carbon nanofibers (CoNi@C-CNFs) as a highly efficient electrocatalyst to accelerate bidirectional polysulfide conversions. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) reveals a significantly improved catalytic effect of the CoNi alloy toward polysulfide conversions after introducing the Ni component. Theoretical simulations further confirm that the synergistic interaction between the Co and Ni atoms enhances catalytic performance. Electrochemical measurements demonstrate a high specific capacity of 705 mAh g^-1 at 3.0 C and exceptional long-term cyclic stability at both 1.0 and 2.0 C. Impressively, an areal capacity of 5.28 mAh cm^-2 is achieved under a sulfur loading of ∼6.1 mg cm^-2 with lean electrolyte conditions (∼6.5 μL mg_s^-1).