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 Li2Sx 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.