Three-dimensional Porous C₃N₄ Nanosheets@Reduced Graphene Oxide Network as Sulfur Hosts for High Performance Lithium-Sulfur Batteries

Highlights: •A light-weight 3D porous C₃N₄ @reduced graphene oxide (PCN@rGO) network is prepared. •The polar PCN can chemically adsorb polysulfides to alleviate shuttle effect. •The 3D network with macro/mesopores facilitates fast electron and ion transfer. •The Li-S battery shows superior rate and cycling (800 cycles) performance. -- Abstract: Lithium-sulfur (Li-S) batteries have attracted considerable attention as one of the most promising power sources due to the higher energy density, lower cost and better environmental friendliness. However, Li-S batteries still face a challenge of unsatisfied cycle life due to the so-called "shuttle effect". Here, a 3D light-weight and porous C₃N₄ nanosheets@reduced graphene oxide (PCN@rGO) network is prepared to overcome the barrier. The 3D PCN@rGO network can not only firmly anchor polysulfides by strong chemical adsorption, but also offer fast electron and mass transfer paths to enhance kinetics of redox reactions. Meanwhile, the 3D network can hinder aggregation of C₃N₄ nanosheets or rGO nanosheets to remain a high surface area. As a result, the PCN@rGO cathode delivers high reversible capacities of 1205, 1150, 986, 800, 685, and 483 mAh g⁻¹ at the rates of 0.1, 0.2, 0.5, 1, 2, and 5C, respectively, and the cathode still delivers a specific capacity of 680 mAh g⁻¹ at 0.5C after 800 cycles, demonstrating a very low capacity decay of 0.048% per cycle. The exploration of this light-weight polar C₃N₄ as a sulfur host provides a promising choice to achieve high energy density and long cycle life Li-S batteries.