Dual-single-atoms of Pt–Co boost sulfur redox kinetics for ultrafast Li–S batteries

Abstract

Applications of lithium–sulfur (Li–S) batteries are still limited by the sluggish conversion kinetics from polysulfide to Li₂S. Although various single-atom catalysts are available for improving the conversion kinetics, the sulfur redox kinetics for Li–S batteries is still not ultrafast. Herein, in this work, a catalyst with dual-single-atom Pt-Co embedded in N-doped carbon nanotubes (Pt&Co@NCNT) was proposed by the atomic layer deposition method to suppress the shuttle effect and synergistically improve the interconversion kinetics from polysulfides to Li₂S. The X-ray absorption near edge curves indicated the reversible conversion of Li₂S_x on the S/Pt&Co@NCNT electrode. Meanwhile, density functional theory demonstrated that the Pt&Co@NCNT promoted the free energy of the phase transition of sulfur species and reduced the oxidative decomposition energy of Li₂S. As a result, the batteries assembled with S/Pt&Co@NCNT electrodes exhibited a high capacity retention of 80% at 100 cycles at a current density of 1.3 mA cm⁻² (S loading: 2.5 mg cm⁻²). More importantly, an excellent rate performance was achieved with a high capacity of 822.1 mAh g⁻¹ at a high current density of 12.7 mA cm⁻². This work opens a new direction to boost the sulfur redox kinetics for ultrafast Li–S batteries.