Metal-Halide Gelated MXene and Its Use as a Bifunctional Sulfur Host Stabilizing Both Cathode and Anode for Practical Lithium-Sulfur Batteries

The gelation of MXene promises to assemble a 3D conductive and catalytic monolith for various applications. However, controllable assembly and function customization are still challenging. Here, with a "killing two birds with one stone" initiator (metal halide, typically ZnI2), the controllable gelation of MXene is enabled, which produces a sulfur host that stabilizes not only the cathode but also the lithium metal anode for lithium-sulfur batteries. Zn2+ cations trigger the gelation and act as linkers between MXene nanosheets (NSs), while the iodine anions as spacers avoid the NSs restacking, forming a monolith with a well-tunable 3D structure. As a sulfur host, the formed 3D monolith with adsorptive Zn-O sites and highly accessible surface greatly enhances the sulfur redox kinetics, effectively suppressing the shuttling and sulfur loss. At the same time, iodine anions are released into the electrolyte as additives eliminating dead Li for the anode in cycling. Thus, the assembled battery shows high Coulombic efficiency (similar to above 99%, even under high sulfur loading: 6.6 mg cm(-2)) and long cycling stability. Under the practical condition (E/S ratio: 5 mu L mg(s)(-1), sulfur loading: 5 mg cm(-2)), high capacity retention of >70% for 200 cycles is achieved.