Crumpled nitrogen-doped aerogels derived from MXene and pyrrole-formaldehyde as modified separators for stable lithium-sulfur batteries

A crumpled nitrogen-doped porous MPF13-550 composite is synthesized through freeze-dried and high-temperature carbonized methods by polymerization of formaldehyde and pyrrole on Ti3C2Tx MXene surface by hydrogen bonding to form gels as precursors. MPF13-550 has strong adsorption to polysulfides due to the properties of MXene’s Lewis acid and polar surface. Therefore, the multifunctional separator fabricated by coating the commercial polypropylene (PP) separator with MPF13-550 exhibits favorable electrochemical performance in lithium-sulfur batteries. [Display omitted] •A crumpled nitrogen-doped porous MPF13-550 composite is synthesized through polymerization of formaldehyde and pyrrole on Ti3C2Tx MXene surface.•MPF13-550 composite can immobilize lithium polysulfides via strong chemisorption and reactivate polysulfides via its high conductivity.•The multifunctional separator with MPF13-550 exhibits favorable electrochemical performance in lithium-sulfur batteries. Lithium-sulfur batteries have high theoretical specific capacity and energy density, but their industrialization is limited by the polysulfide shuttle effect and the sluggish reaction kinetics. It has been recognized that MXene has strong adsorption of polysulfides due to the Lewis acidic surface. In this work, a crumpled nitrogen-doped porous MPF13-550 composite is synthesized through freeze-dried and high-temperature carbonized methods, in which the monomers of formaldehyde and pyrrole induced by Ti3C2Tx MXene form polymer gels as precursors. The as-prepared MPF13-550 possesses a large specific surface area (179 m2 g−1) and high nitrogen doping (10.22 at.%). The multifunctional separator fabricated by coating the commercial polypropylene (PP) separator with MPF13-550 (MPF13-550/PP) is applied in lithium-sulfur (Li-S) battery, in which the functional separator has the advantages of immobilizing lithium polysulfides via strong chemisorption and reactivation of sulfur because of the high conductivity. Consequently, the Li-S battery with the MPF13-550/PP separator exhibits high initial discharge capacity (1235 mA h g−1 at 0.1 C), good rate capabilities (593 mA h g−1 at 2.0 C), and remarkable cycling performance (721 mA h g−1 at 0.2 C after 200 cycles).