Stabilizing Lithium-Sulfur Batteries through Control of Sulfur Aggregation and Polysulfide Dissolution

Lithium-sulfur (Li-S) batteries are investigated intensively as a promising large-scale energy storage system owing to their high theoretical energy density. However, the application of Li-S batteries is prevented by a series of primary problems, including low electronic conductivity, volumetric fluctuation, poor loading of sulfur, and shuttle effect caused by soluble lithium polysulfides. Here, a novel composite structure of sulfur nanoparticles attached to porous-carbon nanotube (p-CNT) encapsulated by hollow MnO₂ nanoflakes film to form p-CNT@Void@MnO₂ /S composite structures is reported. Benefiting from p-CNTs and sponge-like MnO₂ nanoflake film, p-CNT@Void@MnO₂ /S provides highly efficient pathways for the fast electron/ion transfer, fixes sulfur and Li₂ S aggregation efficiently, and prevents polysulfide dissolution during cycling. Besides, the additional void inside p-CNT@Void@MnO₂ /S composite structure provides sufficient free space for the expansion of encapsulated sulfur nanoparticles. The special material composition and structural design of p-CNT@Void@MnO₂ /S composite structure with a high sulfur content endow the composite high capacity, high Coulombic efficiency, and an excellent cycling stability. The capacity of p-CNT@Void@MnO₂ /S electrode is ≈599.1 mA h g^-1 for the fourth cycle and ≈526.1 mA h g^-1 after 100 cycles, corresponding to a capacity retention of ≈87.8% at a high current density of 1.0 C.