Multifunctional Composite Separator Based on NiS2/NiSe2 Homologous Heterostructure Polyhedron Promotes Polysulfide Conversion for High Performance Lithium-Sulfur Batteries.

The shuttle effect significantly hinders the industrialization of high-energy-density lithium-sulfur batteries. To address this issue, NiS₂/NiSe₂ homologous heterostructure polyhedron (HHP) composite separators were developed to immobilize polysulfides and promote their swift conversion. An in-situ visualization symmetrical cell was specifically designed to show the rapid polysulfide adsorption capability of NiS₂/NiSe₂ HHP, while the electrolyte-separator interfacial contact behavior was simulated to elucidate the mechanism of action of the composite separator in affecting the homogeneous nucleation of lithium metal surfaces. The electrochemical experimental result highlights the substantial enhancement in the reaction kinetics of polysulfides facilitated by NiS₂/NiSe₂ HHP, owing to its high Li⁺ diffusion coefficient and Li₂S deposition capacity. The NiS₂/NiSe₂ HHP cells demonstrate high initial specific capacity (1224.1 mAh g^-1) at 0.2 C and minimal decay rates (0.073%) at 2 C. The NiS₂/NiSe₂ HHP separator has high electrochemical catalytic activity with multiple adsorption sites, enabling the rapid polysulfide conversion and contributing to the preparation of high-performance lithium-sulfur batteries.