Nanoscale Encapsulation of Sulfur Cathodes via Self-Healing and Polar Synergistic Multifunctional Coating for High-Performance Li–S Batteries

The development of lithium–sulfur (Li–S) batteries is plagued by serious polysulfide shuttling, sluggish redox reaction kinetics, and low sulfur utilization. In this work, a nanoscale poly(hindered urea) (PHU) coating with self-healability is designed for sulfur cathodes to achieve an improved electrochemical performance. The as-prepared polymer coating in a thickness of about 3 nm uniformly on the surface of the nanoscale sulfur/carbon (S/C) particles acts as a physical barrier to effectively encapsulate and accumulate lithium polysulfide (LiPS) inside the S/C nanoscale particles and thus facilitates the rapid conversion of LiPSs. In addition, the dynamic and reversible self-healing hindered urea bonds (HUBs) endow the PHU coating layer with the ability to maintain structural integrity and stability even after numerous cycles of volume expansion and shrinkage from nanoscale particles to the electrode level. More importantly, the polar groups carried by the PHU polymer exert a strong adsorption effect on LiPSs, thus further hindering the shuttling of LiPSs. Consequently, the nanoarchitecture with PHU coating layer exhibits impressive cycle stability (maintaining 82.8% capacity retention after 150 cycles at 0.5 C) and outstanding rate performance (capacity retention of 623.9 mAh g–1 at 2 C). Furthermore, even under a high sulfur loading of 8.47 mg cm–1, a high areal-specific capacity of 6.4 mAh cm–2 is still delivered.