Layered Ni-MOFs with dual-ligand modulation: A high-rate-performance sulfur host for enhanced catalytic activity in lithium-sulfur batteries

Redox sluggishness and polysulfide dissolution in lithium-sulfur (Li-S) batteries arise from weak host with polysulfides interactions. Herein, ligand defects are controllably engineered within a two-dimensional (2D) Ni-based metal-organic frameworks (Ni-MOFs) that is epitaxially grown on rGO to afford ultrathin composite nanosheets. By precisely modulating the molar ratio of terephthalic acid to salicylic acid during solvothermal synthesis, a series of Ni-MOFs/rGO composites (denoted NPS/rGO) are obtained. The defective architecture simultaneously exposes a high density of open coordination sites and establishes continuous Li-ion diffusion pathways. Notably, NPS-3/rGO exhibits maximal long-chain lithium polysulfides (LiPSs) chemisorption as quantified (ultraviolet–visible (UV–vis)) and fastest liquid–liquid and liquid–solid redox kinetics (symmetric-cell cyclic voltammograms (CV) and potentiostatic nucleation). When evaluated as a sulfur host in Li-S coin cells, the S@NPS-3/rGO cathode effectively suppresses polysulfide shuttling. Consequently, the NPS-3/rGO cathode delivers 1493.4 mAh·g⁻¹ at 0.1 C, 683.6 mAh·g⁻¹ at 2 C and less than 0.049% capacity decay per cycle over 750 cycles at 1 C, even at 3.72 mg·cm⁻² and electrolyte/sulfur (E/S) ratio of 11.88 µL·mg⁻¹, it retains 1002.8 mAh·g⁻¹ at 0.1 C. This work highlights the potential of dual-ligand-modulated, ultrathin defective MOFs/carbon hybrids for high-rate, long-life Li-S batteries.