An Electrolyte Engineered Homonuclear Copper Complex as Homogeneous Catalyst for Lithium–Sulfur Batteries

Abstract Lithium–sulfur (Li–S) batteries suffer from severe polysulfide shuttle, retarded sulfur conversion kinetics and notorious lithium dendrites, which has curtailed the discharge capacity, cycling lifespan and safety. Engineered catalysts act as a feasible strategy to synchronously manipulate the evolution behaviors of sulfur and lithium species. Herein, a chlorine bridge‐enabled binuclear copper complex (Cu‐2‐T) is in situ synthesized in electrolyte as homogeneous catalyst for rationalizing the Li–S redox reactions. The well‐designed Cu‐2‐T provides completely active sites and sufficient contact for homogeneously guiding the Li₂S nucleation/decomposition reactions, and stabilizing the lithium working interface according to the synchrotron radiation X‐ray 3D nano‐computed tomography, small angle neutron scattering and COMSOL results. Moreover, Cu‐2‐T with the content of 0.25 wt% approaching saturated concentration in electrolyte further boosts the homogeneous optimization function in really operated Li–S batteries. Accordingly, the capacity retention of the Li–S battery is elevated from 51.4% to 86.3% at 0.2 C, and reaches 77.0% at 1.0 C over 400 cycles. Furthermore, the sulfur cathode with the assistance of Cu‐2‐T realizes the stable cycling under the practical scenarios of soft‐packaged pouch cell and high sulfur loading (6.5 mg cm⁻² with the electrolyte usage of 4.5 µL mg_S⁻¹).