A semi-immobilized sulfur-rich copolymer backbone with conciliatory polymer skeleton and conductive substrates for high-performance Li-S batteries

Sulfur-rich polymers have gained a great deal of attention as the next-generation active materials in lithium-sulfur (Li-S) batteries due to their low cost, environmental compatibility, naturally sulfur uniform dispersion, and distinctive structure covalently bonding with sulfur atoms. However, the poor electrical conductivity and undesirable additional shuttle effect still hinder the commercial application of sulfur-rich polymers. Herein, we report a flexible semi-immobilization strategy to prepare allyl-terminated hyperbranched poly(ethyleneimine)-functionalized reduced graphene oxide (A-PEI-EGO) as sulfur-rich copolymer backbone. The semi-immobilization strategy can effectively reconcile the demand for polymer skeleton and conductive substrates through forming quaternary ammonium groups and reducing oxygen-containing functional groups, resulting in enhanced skeleton adsorption capacity and substrate electronic conductivity, respectively. Furthermore, the stable covalent bonding connection based on polymer molecules (A-PEI) not only completely prevents the additional shuttle effect of lithiation organic molecules and even sulfur-rich oligomers, but provides more inverse vulcanization active sites. As a result, the as-prepared A-PEI-EGO-S cathodes display an initial discharge capacity of 1338 mA h g−1 at a rate of 0.1 C and an outstanding cycling stability of 0.046% capacity decay per cycle over 600 cycles. Even under 6.2 mg cm−2 S-loaded and sparing electrolyte of 6 µL mg−1, the A-PEI-EGO-S cathode can also achieve a superior cycling performance of 98% capacity retention after 60 cycles, confirming its application potential.