Robust Room‐Temperature Sodium‐Sulfur Batteries Enabled by a Sandwich‐Structured MXene@C/Polyolefin/MXene@C Dual‐functional Separator

Room‐temperature sodium‐sulfur (RT‐Na‐S) batteries are attracting increased attention due to their high theoretical energy density and low‐cost. However, the traditional RT‐Na‐S batteries assembled with glass fiber (GF) separators are still hindered by the polysulfide shuttle effect and sodium dendrite growth, limiting the battery's capacity and cycling stability. Here, a facile and effective method toward commercial polyolefin separators for constructing stable RT‐Na‐S batteries is presented. By coating commercial polypropylene membrane with core‐shell structured MXene@C nanosheets, a powerful dual‐functional separator with improved electrolyte wettability that can inhibit polysulfide migration and induce uniform sodium disposition is developed. More importantly, the modified separator can also accelerate the conversion kinetics of sodium polysulfides. Benefiting from these characteristics, the as‐prepared RT‐Na‐S battery exhibits a remarkably enhanced capacity (1159 mAh g‐1 at 0.2 C) and excellent cycling performance (95.8% of capacity retention after 650 cycles at 0.5 C). This study opens a promising avenue for the development of high‐performance Na‐S batteries. A powerful dual‐functional separator is developed by coating commercial polypropylene membrane with core‐shell structured MXene@C nanosheets. When employed in room‐temperature sodium‐sulfur batteries, this separator can not only guide a uniform sodium disposition, but also has good capability to capture and convert the polysulfides, leading to the significantly enhanced capacity and cycling performance.