Electronic structure adjustment of lithium sulfide by a single-atom copper catalyst toward high-rate lithium-sulfur batteries

Electrocatalytically reducing the energy barrier for Li₂S deposition/dissociation is a promising strategy for high-rate Li-S batteries. However, the catalytic sites would be covered by the insulating Li₂S product during discharge, which deteriorates the catalytic activity. Here, suggested by first-principles calculations, single-atom copper (SA-Cu) was screened out to endow the insulator-to-metal transition of adsorbed Li₂S in view of the electronic structure. In addition to the thermodynamically reduced redox energy barrier, metallic Li₂S nuclei deposited on SA-Cu decorated nitrogen-doped carbon fiber foam (SA-Cu@NCNF) with favorable electronic transport present 3D spherical clusters rather than conventional 2D lateral morphology by continuous 3D nucleation and growth. The Li₂S deposition capacity and the catalytic efficiency of Li₂S-covered catalytic sites are thus greatly improved. As a result, SA-Cu@NCNF based Li-S cells with a sulfur loading of 4 mg cm⁻² retained an areal capacity of 1.60 mAh cm⁻² at 5 C after 500 cycles (0.038% decay per cycle). A competitive areal capacity of 8.44 mAh cm⁻² was obtained at 0.2 C with a sulfur loading of 10 mg cm⁻². The demonstration of the distinctive design of catalysts to adjust the electronic structure of adsorbed Li₂S paves the way for developing high-rate and long-life Li-S batteries.