Engineering strong electronegative nitrogen-rich porous organic polymer for practical durable lithium-sulfur battery

Abstract

The practical application of porous organic polymers (POPs) in Li–S batteries (LiSBs) is severely hampered by low sulfur loading and weak chemisorption. Here, a novel organosulfur copolymer host (POP@F/S) with polar nitrogen-rich heteroatoms is prepared by in situ anchoring of sulfur in 3D perfluorinated hierarchical porous polymers via nucleophilic aromatic substitution reaction (SNAr) reaction. The design of hierarchical pore structure with high porosity not only offers strong physical confinement to polysulfide species but also increase the sulfur loading and buffer the volume change during lithiation. Notably, calculations and experimental results indicate that the triazine and secondary amine nitrogen atoms containing lone electron pairs can act as Lewis base sites to strongly interact with the terminal lithium ions in lithium polysulfide, thereby suppressing the shuttle effect. Attributed to these merits, LiSBs with POP@F/S composite cathode exhibit excellent rate capability and ultra-low capacity decay of only 0.019% per cycle after 500 cycles at 1C. Even more excitingly, a desirable areal capacity of 8.65 mAh cm−2 is delivered when with 7.9 mg cm−2 sulfur loading, and a satisfactory lifetime of over 150 cycles is maintained even under lean electrolyte (E/S = 5 μL mg−1), demonstrating remarkable potential in developing high-performance LiSBs.