Nanoscale Encapsulation\nof Sulfur Cathodes via Self-Healing\nand Polar Synergistic Multifunctional Coating for High-Performance\nLi–S Batteries

The development of lithium–sulfur (Li–S)\nbatteries\nis plagued by serious polysulfide shuttling, sluggish redox reaction\nkinetics, and low sulfur utilization. In this work, a nanoscale poly(hindered\nurea) (PHU) coating with self-healability is designed for sulfur cathodes\nto achieve an improved electrochemical performance. The as-prepared\npolymer coating in a thickness of about 3 nm uniformly on the surface\nof the nanoscale sulfur/carbon (S/C) particles acts as a physical\nbarrier to effectively encapsulate and accumulate lithium polysulfide\n(LiPS) inside the S/C nanoscale particles and thus facilitates the\nrapid conversion of LiPSs. In addition, the dynamic and reversible\nself-healing hindered urea bonds (HUBs) endow the PHU coating layer\nwith the ability to maintain structural integrity and stability even\nafter numerous cycles of volume expansion and shrinkage from nanoscale\nparticles to the electrode level. More importantly, the polar groups\ncarried by the PHU polymer exert a strong adsorption effect on LiPSs,\nthus further hindering the shuttling of LiPSs. Consequently, the nanoarchitecture\nwith PHU coating layer exhibits impressive cycle stability (maintaining\n82.8% capacity retention after 150 cycles at 0.5 C) and outstanding\nrate performance (capacity retention of 623.9 mAh g<sup>–1</sup> at 2 C). Furthermore, even under a high sulfur loading of 8.47 mg\ncm<sup>–1</sup>, a high areal-specific capacity of 6.4 mAh\ncm<sup>–2</sup> is still delivered.