Rechargeable systems based on sulfur cathodes have attracted considerable interest as promising candidates for advanced energy storage owing to their exceptionally large theoretical energy density. However, widespread implementation of these batteries is still hindered by several intrinsic challenges. In particular, soluble lithium polysulfide intermediates tend to dissolve into the electrolyte and migrate between electrodes, which leads to active material loss and severe capacity decay. In addition, the redox conversion reactions involving these sulfur species proceed relatively slowly, resulting in poor reaction kinetics and reduced electrochemical efficiency. In this work, a nickel@carbon (Ni@C) composite was synthesized from a nickel-based metal-organic framework (Ni-MOF) constructed using 1,4-benzenedicarboxylic acid (BDC) obtained from recycled polyethylene terephthalate (PET) plastic. The synthesized composite was later integrated with a carbon membrane containing both nitrogen and sulfur dopants, which had been derived from recycled corrugated paper. The obtained free-standing Ni@C/NSCM membrane provides effective physical confinement and strong chemical adsorption toward polysulfide intermediates while simultaneously facilitating their rapid redox conversion. In addition, the synergistic effect between N/S heteroatom dopants and the embedded Ni@C nanoparticles enhances electronic transport and promotes reaction kinetics. By employing operando impedance measurements together with distribution-of-relaxation-times evaluation, the device utilizing the Ni@C/NSCM cathode exhibits considerably reduced polarization resistance relative to the cell based on the untreated NSCM framework. This observation verifies that the embedded nickel nanostructures provide a catalytic role during the electrochemical reactions. Consequently, the Ni@C/NSCM/Li2S6 cathode with a sulfur loading of 3.84 mg delivers 980.1 mAh g-1 at 0.2 C and retains 96.5% of its capacity after 200 cycles. Remarkably, even with 8.0 mg of sulfur, the cell still maintains 92.8% capacity retention at 0.1 C. Overall, the present study offers an environmentally friendly approach for transforming discarded plastic and biomass resources into efficient binder-free electrode materials.
Li et al. (Mon,) studied this question.