π‐Conjugation Modulation of Polydisulfide Cathodes via Thiophene Substitution for Magnesium‐Organic Batteries

ABSTRACT

Organic disulfide cathodes exhibit great promise for potential applications in rechargeable magnesium batteries due to their multi‐electron S–S redox chemistry. However, the sluggish kinetics, dissolution in ether‐based electrolytes, and poor conductivity severely limit practical performance. Guided by density functional theory calculations, dithiophene disulfide (DST) was identified as a promising precursor for Mg storage, in which thiophene substitution enhances π‐conjugation, lowers the S─S bond dissociation energy, and improves magnesiation thermodynamics. To suppress dissolution, DST was polymerized into poly(dithiophene disulfide) (PDST), and CNTs were integrated in situ to construct a conductive network, raising the electronic conductivity by four orders of magnitude. The resulting PDST/CNT cathode delivers a capacity of 162 mAh g ⁻¹ at 50 mA g ⁻¹ . Furthermore, the cathode retains approximately 89 mAh g ⁻¹ after 1500 cycles at 500 mA g ⁻¹ and stable electrochemical activity was also observed at −20°C. Kinetic analysis suggests that CNT incorporation facilitates bulk active‐site utilization. Ex situ XPS and Raman spectroscopy further support the reversible cleavage and reformation of S─S bonds, with the polythiophene backbone being largely preserved during cycling. This work highlights a synergistic strategy coupling thiophene substitution, polymerization, and conductive‐network engineering for developing high‐performance disulfide polymer cathodes in magnesium batteries.