Graphene-wrapped microspheres decorated with nanoparticles as efficient cathode material for lithium-sulfur battery

Abstract

• Graphene-wrapped microspheres decorated with metal nanoparticles was developed. • Cr-Ni-NDs@G is an efficient multifunctional sulfur host material for Li-S batteries. • The interaction and conversion kinetic of lithium polysulfide were studied. • The sulfur cathode exhibits high specific capacity and cycling performance. Lithium-sulfur (Li-S) battery is now a promising technology for energy storage. However, the commercialization of Li-S battery was hindered by the shuttle effect of lithium polysulfide and the slow reaction kinetics of sulfur. In this study, MIL-101(Cr) with graphene oxide was composited together through spray-drying. Then, a graphene microsphere composite consisted of three-dimensional conductive network decorated with Cr-Ni-based nanodots (Cr-Ni-NDs) was developed through a facile heat treatment. The microsphere composite was denoted as Cr-Ni-NDs@G, which offers a porous structure and high surface area to increase the accommodation and uniform distribution of sulfur in the cathode. Meanwhile, the three-dimensional conductive network embedded by Cr and Ni nanoparticle not only improved the transportation of electrons, but also act as the active site strengthening the adsorption of lithium polysulfide, promoting the catalytic transformation of lithium polysulfide to Li 2 S. Due to these complementary features, the S/Cr-Ni-NDs@G cathode exhibited a high initial specific capacity (1222.3 mAh·g −1 at 0.2C) and good rate performance (706 mAh·g −1 at 3.0C). In addition, after 500cycles at 1.0C, the faded rate of per cycle of the Li-S battery is only 0.059%. The result demonstrated that S/Cr-Ni-NDs@G composite can be a promising energy storage material in the development of Li-S batteries.