Constructing Charge Transfer Pathways via π-Conjugation Modulation for Long-Cycling Mg-S Batteries.

Abstract

Rechargeable magnesium-sulfur (Mg-S) batteries are considered promising candidates for next-generation energy storage systems due to their intrinsic safety and natural abundance. However, their practical deployment is limited by the sluggish conversion of short-chain polysulfides, which contribute 75% of the theoretical capacity. Herein, cuprous tetrahydroxyquinone (Cu-THQ) is employed as an electrocatalyst anchored on a polypropylene interlayer to accelerate polysulfide conversion in Mg-S batteries. The restricted π-delocalization in the coordination framework and enhanced electron donation from oxygen atoms to Cu centers create the localized electron enrichment microenvironment and upshift the d-band center. This electronic modulation establishes an efficient charge-transfer pathway and strengthens Cu-S orbital hybridization, thereby facilitating the robust anchoring and accelerated reduction of MgS₂ intermediates. Consequently, Mg-S batteries incorporating the Cu-THQ interlayer deliver a high reversible capacity of 470 mAh g^-1 after 2000 cycles at 8.36 A g^-1. Stable cycling performance is also maintained under -20 °C, demonstrating promising application potential. This work presents a π-conjugation-driven approach for accelerating polysulfide conversion and promotes the development of long-life Mg-S batteries.