Ni3S2/N-Doped Carbon Hybrids as Efficient Bidirectional Catalysts for Accelerated Sulfur Redox Kinetics

The practical application of lithium–sulfur batteries (LSBs) is severely impeded by the dissolution and shuttle effects of lithium polysulfides (LiPSs), which can be fundamentally alleviated through the incorporation of polar catalytic materials that both confine LiPSs and accelerate their redox conversion. In this work, Ni3S2/nitrogen-doped carbon composites (NSNCs) were synthesized via a facile one-step calcination of a homogeneous low-melting eutectic precursor composed of 2-thiouracil, NiCl2·6H2O, and ethylene glycol. The simplicity and cost-effectiveness of this synthesis strategy highlight its promise for practical implementation, while optimization of the preparation conditions endows NSNCs with a desirable balance of abundant active sites and intrinsic catalytic activity. Comprehensive theoretical, experimental investigations and in situ XRD reveal the bidirectional catalytic role of NSNCs in facilitating both the deposition and decomposition of Li2S. Owing to the strong catalytic capability of this hybrid structure, the S8 ↔ Li2S conversion is markedly accelerated, and the shuttle effect is effectively suppressed. As a result, LSBs equipped with NSNC-modified separators deliver an ultralow capacity decay rate of only 0.095% per cycle over 400 cycles at 1 C, together with an outstanding rate performance of 721 mAh g–1 at 8 C.