High-Efficiency Polysulfide Trapping with g-C3N4/CNT Hybrids for Superior Lithium-Sulfur Batteries

Abstract

Commercialization of lithium-sulfur (Li-S) batteries is critically hampered by the severe lithium polysulfide shuttle effect. Hence, designing multifunctional materials that synergistically provide physical confinement of polysulfides, chemical entrapment, and catalytic promotion is a viable route for improving Li-S battery performance. Herein, graphitic carbon nitride (g-C₃N₄) with abundant nitrogen atoms was used as the chemical adsorption material to realize a “physical-chemical” dual confinement for polysulfides. Furthermore, the integration of CNTs with g-C₃N₄ is intended to substantially enhance the conductivity of the cathode material. Consequently, the synthesized g-C₃N₄/CNT composite, which functions as an effective polysulfide immobilizer, significantly improved the cycling stability and discharge capacity of Li-S batteries. This enhancement can be attributed to its potent adsorption and catalytic activities. Li-S cells utilizing g-C₃N₄/CNT cathodes exhibit exceptional discharge capacity and notable rate capability. Specifically, after 100 cycles at 0.2 C, the discharge capacity was 701 mAh g⁻¹. Furthermore, even at a high rate of 2 C, a substantial capacity of 457 mAh g⁻¹ was retained.