Improvement of Redox Kinetics of Dendrite-Free Lithium–Sulfur Battery by Bidirectional Catalysis of Cationic Dual-Active Sites
Shuaiqiang Feng, Jiongfan Wang, Jianfeng Wen, Xinyu Li, Zhiyong Wang, Yaping Zeng, Jianrong Xiao
Abstract
The practical application of lithium–sulfur batteries (LSBs) is hampered by the slow lithium polysulfide (LIPS) conversion kinetics and the uncontrollable anode-metal lithium dendrites. Herein, a three-dimensional cation dual-active-site eggshell structure compound (3DCS-FMO@C) was synthesized by soft template, ion exchange, and pyrolysis to modify the commercial separator. Experimental and theoretical analysis results showed that Mn 2+ and Fe 2+ sites in 3DCS-FMO@C can synergistically adsorb LIPSs, effectively regulate the bidirectional conversion dynamics of intermediate liquid-phase LIPSs and solid-phase lithium sulfide, and reduce the energy barrier of the reaction. The 3DCS-FMO@C-modified separator with high mechanical stability and no reduction in ion diffusion also had a lithiophilic central core that can homogenize the lithium-ion flow, thereby inhibiting the dendrite growth of lithium. Based on the above advantages, 3DCS-FMO@C-modified separator LSBs had better electrochemical performance, including an initial capacity of 1530 mAh g –1 at 0.1C and an ultralow decay rate of 0.029% for 1000 cycles at 0.5C. A high area capacity of 8.7 mAh cm –2 was achieved even with high sulfur loading and poor electrolyte. This work provided a basis for understanding the bidirectional catalysis for practical application in LSBs and simultaneously solved the problem of lithium dendrites.