Advanced Graphene@Sulfur composites via an in-situ reduction and wrapping strategy for high energy density lithium–sulfur batteries

Abstract

Graphene/sulfur composite has been extensively studied for sulfur cathodes. However, a rapid and scalable fabrication of sulfur/graphene composite with advanced structures and functions is still a big challenge. Here, we report a unique solution-based strategy to simultaneously realize the reduction of graphene oxide (GO), the synthesis of elemental sulfur (S) and the effective packaging of S. In this strategy, the S firstly reacts with hydrazine hydrate and N, N-Dimethylformamide mixture, which generates a reductive sulfur-containing compound. When mixing this reductive sulfur-containing compound with GO dispersion, GO will be reduced and the reductive sulfur-containing compound will be oxidized to generate S. At the same time S will be well encapsulated inside highly wrinkled graphene layers because of the great interaction between graphene and sulfur through this method. Benefited from the unique packaging structures, the sulfur cathode demonstrates superior electrochemical performance in specific capacity, rate capability and cycling stability. A record high specific capacity of 705 mA h/g is realized at 2C even for a thick sulfur cathode with an areal density of 8.1 mg cm−2. This study brings a facile strategy for the fabrication of advanced sulfur/graphene composites with high energy and power densities.