Dual-Functional Metal–Organic Framework Freestanding Aerogel Boosts Sulfur Reduction Reaction for Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) technology stands out as a promising energy storage system. However, its journey toward practical implementation is hindered by sluggish sulfur reduction reaction (SRR) kinetics. A free-standing graphene aerogel (GA) combined with a copper-based metal–organic framework (MOF–GA) is fabricated as the sulfur host material for Li–S battery cathodes. The presence of MOF particles assumes a dual role, demonstrating its efficacy not only as a catalyst for the reduction reaction of graphene oxide (GO) but also as an electrochemical catalyst to promote sluggish SRR kinetics. The former amplifies electron transfer kinetics within the electrode, and the latter elevates the overall cell performance. Experimental results and theoretical calculations have proven the catalytic activity of MOF–GA electrodes, leading to a higher sulfur utilization of over 80% and a lower capacity decay of 0.082% per cycle. Under extreme conditions, the Li–S cells show a high initial specific capacity of 1113.0 mAh·g –1 under an elevated loading of 4.25 mg·cm –2 and a high sulfur fraction >70%. This study shows the effectiveness of the synergist effects of MOF particles within the GA framework in promoting the sulfur redox reaction in Li–S batteries.