Friedel-Crafts Acylation of Lignin for Enhanced Charge Transport in Lithium-Sulfur Battery Cathodes

The development of high-performance lithium-sulfur (Li–S) batteries is limited by slow polysulfide conversion kinetics and shuttle effect. Herein, we propose Friedel-Crafts acylation approach as a strategy for constructing π -conjugated lignin composites, exhibiting enhanced conductivity and confinement capability. The Li-S battery with fumaric chloride modified poplar lignin ester (FC-PLE) cathode exhibits an initial discharge capacity of 870.5 mAh g −1 at 0.1 C, retaining 599.7 mAh g −1 after 100 cycles, with only 0.07% capacity decay after 900 cycles. The performance improvement is attributed to extended π -conjugation in the lignin backbone and optimized charge transfer pathways. These modifications effectively inhibit LiPS shuttle effect and enhance cycling stability. Li 2 S nucleation experiments confirm that FC-PLE has a faster nucleation rate, with a deposition capacity of 84.53 mAh g −1 , superior to fumaric chloride modified alkaline lignin ester (FC-ALE, 36.46 mAh g −1 ) and fumaric chloride modified enzymatic lignin ester (FC-ELE, 42.03 mAh g −1 ). These results indicate that the introducing fumaroyl groups enhances polysulfide adsorption capability and accelerates Li 2 S nucleation of modified lignin-based cathode FC-PLE, FC-ALE, and FC-ELE. These findings highlight the potential of Friedel-Crafts modified conjugated lignin for advancing development of sustainable, high-efficiency Li-S batteries.