Trimetallic ZnCoNi-NC@MWCNT Separator with Enhanced Polysulfide Trapping for Stable Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are promising candidates for next-generation energy storage systems, yet their practical implementation is severely hindered by the shuttle effect of soluble lithium polysulfides (LiPSs) and sluggish multistep sulfur redox kinetics. Here, we design a ZnCoNi zeolitic imidazolate framework (ZnCoNi-ZIF) that is in situ grown on acid-treated multiwalled carbon nanotubes (MWCNTs) and subsequently carbonized to afford an N-doped carbon/MWCNT composite embedded with Zn–Co–Ni nanoparticles (denoted as ZnCoNi-NC@MWCNT). This composite is employed as a functional coating on commercial polypropylene separators. The cooperative effect of trimetallic active sites and the conductive carbon matrix endows the separator with polar M-Nx and pyridinic N sites, a high-surface-area mesoporous architecture, and continuous electron pathways, enabling physical confinement, chemical anchoring, and electrocatalytic conversion of LiPSs. Specifically, uniformly distributed Zn–Co–Ni nanoparticles act as electrocatalytic centers to accelerate the reversible multistep sulfur transformation, while the synergistic interplay among these components mitigates the shuttle effect and reinforces the electrode–electrolyte interface stability. Consequently, Li–S cell with this modified separator delivers 894 mAh g–1 at 5.2 mg cm–2 sulfur loading and 0.2 C, and maintains stable cycling over 1908 cycles at 2.2 mg cm–2 and 0.5C with a low capacity decay of ≈0.041% per cycle and Coulombic efficiency approaching 100%. This work presents a trimetallic-catalyst-based separator engineering strategy for high-performance, long-life Li–S batteries.