Synergistic Regulation of Polysulfides Conversion and Deposition by MOF-Derived Hierarchically Ordered Carbonaceous Composite for High-Energy Lithium-Sulfur Batteries

To achieve a high sulfur loading is critical for high-energy lithium-sulfur batteries. However, high sulfur loading, especially at a low electrolyte/sulfur ratio (E/S), usually causes low sulfur utilization, mainly caused by the slow redox kinetics of polysulfides and the passivation of the discharge product, poor electrically/ionically conducting Li2S. Herein, by using cobalt-based metal organic frameworks (Co-MOFs) as precursors, a Co, N-doped carbonaceous composite (Co, N-CNTs (carbon nanotubes)-CNS (carbon nanosheet)/CFC (carbon fiber cloth)) is fabricated with hierarchically ordered structure, which consists of a free-standing 3D carbon fiber skeleton decorated with a vertical 2D carbon nanosheets array rooted by interwoven 1D CNTs. As an effective polysulfides host, the hierarchically ordered 3D conductive network with abundant active sites and voids can effectively trap polysulfides and provide fast electron/ions pathways to convert them. In addition, Co and N heteroatoms can strengthen the interaction with polysulfides and accelerate its reaction kinetics. More importantly, the interwoven CNTs with Co, N-doping can induce 3D Li2S deposition instead of conventional 2D deposition, which benefits improving sulfur utilization. Therefore, for Co, N-CNTs-CNS/CFC electrodes, even at a high sulfur loading of 10.20 mg cm(-2) with a low E/S of 6.94, a high reversible areal capacity of 7.42 mAh cm(-2) can be achieved with excellent cycling stability.