Implanting single-atom N2-Fe-B2 catalytic sites in carbon hosts to stabilize high-loading and lean-electrolyte lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries suffer from soluble lithium polysulfide (LiPS) shuttling and sluggish redox kinetics. The rational design of carbon-supported single-atom catalysts (SACs) as both LiPS immobilizers and sulfur redox promoters is of great significance for high-loading and lean-electrolyte Li-S batteries. However, the most popular nonpolar porphyrin-like transition metal-nitrogen (M-N-4) SACs cannot maximize the catalytic activity of the metal center. Herein, a B, N co-coordinated N-2-Fe-B-2 SAC embedded in a B, N-rich carbon matrix (denoted as Fe SAs@BCN) is disclosed for the first time to construct state-of-the-art Li-S batteries. We reveal experimentally and theoretically that the asymmetric N-2-Fe-B-2 configuration not only rapidly captures LiPSs through strong Lewis acid-base interactions, but also greatly catalyzes the bidirectional sulfur redox chemistry by lowering the Li2S deposition/decomposition energy barriers. As such, the well-designed SACs enable Li-S batteries to promise extraordinary durability (82% retention over 1000 cycles at 5 C) and high areal capacities even under harsh sulfur mass loadings. More encouragingly, a 359 Wh kg(-1) pouch cell with an ultrahigh loading of 11.6 mg.S cm(-2) and a lean electrolyte to sulfur (E/S) ratio of 3 mu L mg.S-1 is further demonstrated. This work shows that N-2-Fe-B-2 SACs hold great promise in realizing high-energy-density Li-S batteries.

Automated summary

Researchers have developed a carbon-supported single-atom catalyst (SAC) for lithium-sulfur batteries. The catalyst not only immobilizes lithium polysulfide (LiPS) but also promotes sulfur redox reactions, leading to improved battery performance. The SACs showed high durability and areal capacities, even under harsh conditions.