A Dual-Function Na2 SO4 Template Directed Formation of Cathode Materials with a High Content of Sulfur Nanodots for Lithium-Sulfur Batteries

Abstract

The sulfur content in carbon-sulfur hybrid using the melt-diffusion method is normally lower than 70 wt%, which greatly decreases the energy density of the cathode in lithium-sulfur (Li-S) batteries. Here, a scalable method inspired by the commercialized production of Na₂ S is used to prepare a hierarchical porous carbon-sulfur hybrid (denoted HPC-S) with high sulfur content (≈85 wt%). The HPC-S is characterized by the structure of sulfur nanodots naturally embedded in a 3D carbon network. The strategy uses Na₂ SO₄ as the starting material, which serves not only as the sulfur precursor but also as a salt template for the formation of the 3D carbon network. The HPC-S cathode with such a high sulfur content shows excellent rate performance and cycling stability in Li-S batteries because of the sulfur nanoparticles, the unique carbon framework, and the strong interaction between them. The production method can also be readily scaled up and used in practical Li-S battery applications.

Keywords: dual-function templates; hierarchical porous carbon frameworks; lithium-sulfur batteries; sulfur nanodots.