Synergistic design of g-C₃N₄-supported CNTs: experimental and DFT insights for enhanced electrochemical performance in flexible Li-S batteries

In addressing the shuttle effect and sluggish redox kinetics of lithium polysulfides (LiPSs) in lithium-sulfur batteries, we developed a novel heterostructure combining 1D carbon nanotubes (CNTs) grown on a 2D sheet of graphitic carbon nitride (g-C3N4) to improve conversion reaction kinetics and LiPS adsorption capacity. The high pyridine N content in g-C3N4 facilitates homogeneous Li ion deposition and enhances affinity between Li and N atoms. Extensive experimental characterization and density functional theory (DFT) calculations validated the interaction between g-C3N4-CNT/S and LiPSs. In pouch cell evaluation, the hybrid g-C3N4-CNT/S cathode, with similar to 70% sulfur loading, demonstrated outstanding rate performance, delivering similar to 895 mA h g(-1) at 0.1C and retaining similar to 500 mA h g(-1) even at 1.5C under lean electrolyte conditions (E/S similar to 5 mu l mg(-1)). Long-term stability over 250 cycles, with a capacity retention of 86% and a coulombic efficiency (CE) of 90.4%, was achieved, even with an elevated sulfur loading of 6.2 mg cm(-2). Post-mortem investigation using X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) elucidated surface chemistry changes and elemental composition alterations, highlighting the formation of various reaction products during charge-discharge cycles. This study underscores the cost-effective heterostructure strategy's potential for advancing LiSBs in practical applications.