Interfacial Engineering and Coupling of MXene/Reduced Graphene Oxide/C3N4 Aerogel with Optimized d‐Band Center as a Free‐Standing Sulfur Carrier for High‐Performance Li‐S Batteries

Abstract

AbstractTo overcome the shuttle effect and improve the energy density of Li–S batteries, developing free‐standing sulfur carriers with high capture and catalytic effect towards polysulfides is an effective strategy. Herein, a MXene/reduced graphene oxide/C3N4 aerogel (MG/C3N4) with three‐dimensional architecture prepared through low‐temperature hydrothermal approach followed by thermal treatment is used as sulfur carrier for free‐standing cathode of Li‐S batteries. In the MG/C3N4, MXene and rGO construct a highly conductive framework, and the MXene nanosheets offer chemical capture and catalytic activity towards lithium polysulfides, in favor of good cycling stability. The introduction of g‐C3N4 further enhances the reactivity of C‐Ti‐N at the hetero‐interface by engineering the electronic state of Ti atoms, leading to the optimized metal d‐band for expediting the multistep conversion of sulfur electrochemistry. Therefore, the free‐standing sulfur cathode with MG/C3N4 carrier achieves excellent performance with a capacity of 1315.6 mAh g−1 at 0.2 C and a capacity retention of 97.5% after 100 cycles as well as superior rate capability with 1167.4 mAh g−1 at 2 C. Even at a high sulfur loading of 4.92 mg cm−2, the cathode remains 940.3 mAh g−1 (4.62 mAh cm−2) after 200 cycles, indicating its promising potential for achieving high‐performance Li‐S batteries.