Ab-Initio Studies on Fluorine–Sulfur Coterminated MXene–Reduced Graphene Oxide Composites for Fast Polysulfide Conversion in Flexible Sodium–Sulfur Batteries

Flexible, high-performance cathodes are essential for
realizing
practical room-temperature sodium–sulfur (Na–S) batteries,
yet sluggish polysulfide conversion, poor retention, and mechanical
limitations remain major barriers. Here, we introduce a sulfur/fluorine
coterminated vanadium carbide MXene integrated with reduced graphene
oxide, V2CF0.67S0.33 (rGO), designed
to enhance polysulfide anchoring, catalytic activity, and flexibility
simultaneously. First-principles calculations reveal that this mixed-termination
MXene–rGO composite exhibits markedly stronger polysulfide
adsorption (0.8–3.90 eV) than single-terminated counterparts
while preserving structural integrity and metallic conductivity for
efficient charge transport. The material achieves the lowest Na2S decomposition barrier reported for MXene-based Na–S
cathodes (0.287 eV) and a reduced Gibbs free energy pathway for the
sulfur reduction reaction, enabling faster and more complete sulfur
utilization. Charge density difference, partial density-of-states,
and crystal orbital Hamilton population analyses confirm substantial
charge transfer and strong interfacial chemical bonding with Na2Sn species. Mechanical stress–strain
simulations further demonstrate robust yet flexible behavior, highlighting
its promise for wearable energy storage. This work establishes surface-termination
engineering in MXene–graphene hybrids as a promising route
toward high-capacity, durable, and mechanically compliant Na–S
batteries.