Porous Carbon from Luffa cylindrica for Efficient Polysulfide Regulation in Room-Temperature Sodium–Sulfur Batteries

Abstract Room-temperature sodium–sulfur (RT Na–S) batteries have emerged as viable options for large-scale energy storage due to the plentiful supply and inexpensive cost of Na and S. However, their application is limited by poor conductivity, severe polysulfide shuttling, and slow redox kinetics. While conventional RT Na–S batteries suffer from the dissolution and migration of soluble polysulfide intermediates, sulfur confinement within microporous carbon can restrict long-chain polysulfide dissolution and promote a more spatially confined sulfur conversion pathway, thereby improving cycling stability and efficiency. This study involved the synthesis of hierarchically porous carbon materials from Luffa cylindrica through temperature controlled carbonization, which are then utilized as sulfur host matrices. The modified S/LC-1000 composite exhibits a well-developed micro/mesoporous structure and strong sulfur–carbon interactions. The optimized microporous/mesoporous LC-1000 host likely suppresses the dissolution of long-chain sodium polysulfides and promotes a more confined sulfur redox pathway. This pathway modulation, driven by sulfur confinement within micropores, enables efficient polysulfide immobilization while simultaneously facilitating enhanced ion/electron transport and improving overall electrochemical reversibility, thereby leading to improved stability and performance. The S/LC-1000 exhibits an initial discharge capacity of 1730 mAh g–1 and sustains about 1360 mAh g–1 after 300 cycles at 0.5 C while sustaining about 677 mAh g–1 after 10,000 cycles at 5C, demonstrating enhanced rate capability and diminished charge-transfer resistance. This study presents a sustainable and efficient approach for developing biomass-derived carbon hosts to address critical constraints of RT Na–S batteries and enhance their application.