Advancing lithium–sulfur battery efficiency: utilizing a 2D/2D g-C₃N₄@MXene heterostructure to enhance sulfur evolution reactions and regulate polysulfides under lean electrolyte conditions

Abstract

Lithium-sulfur batteries (LSBs) show promise for achieving a high energy density of 500 W h kg^-1, despite challenges such as poor cycle life and low energy efficiency due to sluggish redox kinetics of lithium polysulfides (LiPSs) and sulfur's electronic insulating nature. We present a novel 2D Ti₃C₂ Mxene on a 2D graphitic carbon nitride (g-C₃N₄) heterostructure designed to enhance LiPS conversion kinetics and adsorption capacity. In a pouch cell configuration with lean electrolyte conditions (∼5 μL mg^-1), the g-C₃N₄-Mx/S cathode exhibited excellent rate performance, delivering ∼1061 mA h g^-1 at C/8 and retaining ∼773 mA h g^-1 after 190 cycles with a Coulombic efficiency (CE) of 92.7%. The battery maintained a discharge capacity of 680 mA h g^-1 even at 1.25 C. It operated reliably at an elevated sulfur loading of 5.9 mg cm^-2, with an initial discharge capacity of ∼900 mA h g^-1 and a sustained CE of over 83% throughout 190 cycles. Postmortem XPS and EIS analyses elucidated charge-discharge cycle-induced changes, highlighting the potential of this heterostructured cathode for commercial garnet LSB development.