Nitrogen-doped porous graphene/MnO2 composite as sulfur hosts for lithium-sulfur batteries

Abstract

Lithium‑sulfur batteries have been considered as a promising chemical power source owing to the low costs, high energy densities, and nontoxicity. However, sulfur-based cathodes have several shortcomings, including poor electrochemical activity and fast capacity attenuation. In this work, manganese dioxide (MnO2) and nitrogen-doped porous graphene (pNGA) were introduced to the sulfur cathode to improve its electrochemical activity and prevent the rapid decay of capacity. The pNGA/MnO2 composite with a three-dimensional architecture was fabricated by steam etching of nitrogen-doped graphene aerogel and chemical deposition of MnO2 nanoparticles. In this structure, the nitrogen-doped porous graphene acts as a skeleton to form a conductive network. The MnO2 particles anchored on graphene sheets have a good interaction with polysulfides. The as-prepared pNGA/MnO2@S cathode shows an excellent comprehensive electrochemical performance. The calculated specific capacities are 1144, 1007, 920, 852, and 762 mA h g−1 at 0.1C, 0.2C, 0.5C, 1C, and 2C respectively. In addition, the pNGA/MnO2@S cathode displays a good cycling performance: the specific capacity maintains at 887 mA h g−1 at 0.5C over 100 cycles.