Unearth the understanding of interfacial engineering techniques on nano sulfur cathodes for steady Li–S cell systems

Abstract

Inherent/tough cell issues such as the troublesome shuttling of intermediate Li₂S_n (n = 3−8) and the inferior conductivity of S/Li₂S are still hardly eliminated in rechargeable Li–S cells. Continually rationalizing the cathodes via innovative interfacial engineering would, thereby, be an indispensable propellant for expediting cell kinetics for practical utilizations. By the deliberate choice of nano S cathodes as a typical fundamental research paradigm, we herein affirm a special controllable engineering protocol via (i) in situ pyrrole molecules polymerization on S nanoparticles and (ii) osmosis-driven procedures where inner high-density S atoms tend to be evenly etched/lost. Parameters such as the aging time and persulfate salt addition are verified as dominant factors to tune the exterior shell thickness and S content in samples. To further strengthen the cathode structural integrity and conductivity, virus-like hierarchical S@PPy@ZnIn₂S₄ products are constructed by the intimate growth of conductive/polar ZnIn₂S₄ nanolayers on all exterior S@PPy surfaces. Given the positive collaborations from electrode functionality integration and architecture setup, such interface-reinforced cathodes showcase prominent Li-storage performances on either long-lasting cyclic stability/endurance or rate capabilities. This work provides insights into delicate engineering techniques on elemental S for superior Li–S cell systems, and may also open up a smart “nano-interface-level” platform for more artificial/control designs toward other relatively inert molecular nanocrystals.