Coordinated Immobilization and Rapid Conversion of Polysulfide Enabled by a Hollow Metal Oxide/Sulfide/Nitrogen-Doped Carbon Heterostructure for Long-Cycle-Life Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are recognized as the prospective candidate in next-generation energy storage devices due to their gratifying theoretical energy density. Nonetheless, they still face the challenges of the practical application including low utilization of sulfur and poor cycling life derived from shuttle effect of lithium polysulfides (LiPSs). Herein, a hollow polyhedron with heterogeneous CoO/Co9 S8 /nitrogen-doped carbon (CoO/Co9 S8 /NC) is obtained through employing zeolitic imidazolate framework as precursor. The heterogeneous CoO/Co9 S8 /NC balances the redox kinetics of Co9 S8 with chemical adsorption of CoO toward LiPSs, effectively inhibiting the shuttle of LiPSs. The mechanisms are verified by both experiment and density functional theory calculation. Meanwhile, the hollow structure acts as a sulfur storage chamber, which mitigates the volumetric expansion of sulfur and maximizes the utilization of sulfur. Benefiting from the above advantages, lithium-sulfur battery with S-CoO/Co9 S8 /NC achieves a high initial discharge capacity (1470 mAh g-1 ) at 0.1 C and long cycle life (ultralow capacity attenuation of 0.033% per cycle after 1000 cycles at 1 C). Even under high sulfur loading of 3.0 mg cm-2 , lithium-sulfur battery still shows the satisfactory electrochemical performance. This work may provide an idea to elevate the electrochemical performance of LSBs by constructing a hollow metal oxide/sulfide/nitrogen-doped carbon heterogeneous structure.

Facile and scalable synthesis of silicon nanowires from waste rice husk silica by the molten salt process.

Designing nanostructured silicon, such as in the form of nanoparticles, wires, and porous structures, for high-performance Li-ion electrodes, has progressed significantly. These approaches have largely overcome the capacity fading of silicon electrodes from volume expansion during lithiation/de-lithiation. However, they involve high costs, complex processes, and hazardous precursors. Herein, we propose an electrochemical fabrication of silicon nanowires from waste rice husks via a molten salt process based on electrodeoxidation. The addition of NiO as an electric conductor improved the production efficiency and created pores in the nanowires after washing. The electrically produced high-purity silicon yielded high capacity, and the nanowires provided sufficient free volume to accommodate silicon electrode expansion, resulting in improved cycle life. The converted silicon nanowires from the molten salt process will help develop sustainable energy storage materials.