Electronic Modulation and Symmetry-Breaking Engineering of Single-Atom Catalysts Driving Long-Cycling Li-S Battery

Developing efficient and durable single-atom catalysts is vitally important for the sulfur redox reaction (SROR) in Li-S battery, while it remains enormous challenging. Herein, undercoordinated Ni-N₃ moieties anchored on N,S-codoped porous carbon (Ni-NSC) is obtained to enhance the SROR. The experiments and theoretical calculations indicate that the symmetry-breaking charge transfer in Ni single-atom catalyst originates from tuning effect of sulfur atoms mediated Ni-N₃ moieties, which can both facilitate the chemical adsorption by formation of N-Ni⋅⋅⋅S_n ^2-, and achieve a rapid redox conversion of polysulfides because of the enhanced electron transfer. As results, the Ni-NSC based Li-S battery delivers a very high initial reversible capacity (1025 mAh g^-1 at 1 C), as well as outstanding cycling-stability for 2400 cycles at 2 C and 3 C, respectively. Noteworthy, the areal capacity can reach 7.8 mAh cm^-2 at 0.05 C and a retention capacity of 4.7 mAh cm^-2 after 100 cycles at 0.2 C for Ni-NSC based Li-S battery with sulfur loading of 5.88 mg cm^-2. This work provides profound insight for rational optimizing microscopic electronic density of active site to promoting SROR in metal-sulfur batteries.