A porous Cu1.82Se@MXene conductive interlayer for room-temperature sodium-sulfur batteries

Abstract

Room-temperature sodium-sulfur batteries are promising for large-scale energy storage because of the low cost and high abundance of sodium and sulfur, but their practical application is still limited by polysulfide shuttling, sluggish sulfur redox kinetics, and poor long-term stability. In this work, a porous Cu1.82Se@MXene hybrid interlayer was constructed as a functional separator coating for room-temperature sodium-sulfur batteries. Porous Cu2O microspheres were first prepared through a sacrificial-template route and then converted into Cu1.82Se while retaining the original spherical framework. After electrostatic assembly with MXene nanosheets, the obtained composite formed an integrated conductive network with abundant active sites. The modified separator exhibited improved electrolyte wettability, good mechanical integrity, effective suppression of sodium polysulfide diffusion, and enhanced redox response. Scan-rate-dependent CV, EIS, and GITT results further confirmed accelerated Na+ transport, reduced charge-transfer resistance, and lower reaction polarization. As a result, the Cu1.82Se@MXene interlayer enabled high reversible capacities and excellent long-cycle stability, delivering 925.7 mAh g−1 after 200 cycles at 0.2 C and 626.5 mAh g−1 after 800 cycles at 1.0 C. These results demonstrate the effectiveness of coupling Cu-based catalytic sites with a conductive MXene framework for separator engineering in room-temperature sodium-sulfur batteries.