Mesoporous N-doped graphene prepared by a soft-template method with high performance in Li-S batteries.

Abstract

Lithium sulfur (Li-S) batteries, which have high theoretical capacity, are promising candidates for energy storage systems; however, several obstacles, including insulating nature and volumetric expansion of sulfur as well as shuttle effects of polysulfides, impede the commercialization of these batteries. Herein, we utilized mesoporous N-doped graphene (NGM) as a sulfur host, which was synthesized using a type of triblock copolymer, Pluronic F127 (PF127), as a soft template. PF127 not only acted as a spacer to prevent the graphene layers from restacking during the hydrothermal reaction, but also resulted in the formation of high-density wrinkles on the surface of the graphene sheets after annealing. The crumpled NGM with a nitrogen doping content of 4.80 at% had the high specific area and total pore volume of up to 958.72 m2 g-1 and 2.39 cm3 g-1, respectively, providing space for the accommodation and uniform distribution of sulfur in the cathode. Therefore, the sulfur content was increased to 87.2 wt% in the graphene sulfur composite, achieving the discharge capacity of 492.2 mA h g-1TE at 1.08 A g-1TE with a low capacity decay rate of 0.12% per cycle after 400 cycles. Thus, this study provides an effective strategy for enhancing the specific surface area and pore volume of graphene to develop Li-S batteries with high performance.