Graphene oxide-polypyrrole composite as sulfur hosts for high-performance lithium-sulfur batteries

Abstract

Lithium-sulfur batteries are considered as a promising candidate for the next-generation high energy density storage devices. However, they are still hindered by serious capacity decay on cycling caused by the dissolution of redox intermediates. Here, we designed a unique structure with polypyrrole (ppy) inserting into the graphene oxide (GO) sheet for accommodating sulfur. Such a sulfur host not only exhibits a good electronic and ionic conductivity, but also can suppress polysulfide dissolution effectively. With this advanced design, the composite cathode showed a high specific capacity of 548.4[Formula: see text]mA[Formula: see text]h[Formula: see text]g[Formula: see text] at 5.0 C. A stable Coulombic efficiency of [Formula: see text]99.5% and a capacity decay rate as low as 0.089% per cycle along with 300 cycles at 1.0 C were achieved for composite cathodes with 78[Formula: see text]wt.% of S. Besides, the interaction mechanism between PPy and lithium polysulfides (LPS) was investigated by density-functional theory (DFT), suggesting that only the polymerization of N atoms can bind strongly to Li ions of LPS rather than single N atoms. The 3D structure GO-PPy host with high conductivity and excellent trapping ability to LPS offered a viable strategy to design high-performance cathodes for Li–S batteries.