In-situ decoration of MOF-derived carbon on nitrogen-doped ultrathin MXene nanosheets to multifunctionalize separators for stable Li-S batteries

A novel MXene/MOF derivative 2D hybrid (N-Ti3C2/C) was fabricated by decorating nitrogen-doped MXene nanosheets with porous carbon resulted from in-situ nucleation and conversion of ZIF-67 on exfoliated MXenes, which was then employed to modify the commercial separator for Li-S batteries. The uniformly decorated ZIF-67 can isolate MXene nanosheets from restacking and leave sufficient Lewis acidic adsorption surface of MXenes exposed. Moreover, it can also provide nitrogen source to dope nitrogen into MXenes, endowing them with improved surface properties. DFT calculation results demonstrate that such nitrogen-doped MXenes have a stronger chemical adsorption capability for polysulfides than pure MXenes. With further assistance of ZIF-67 derived porous carbon, the N-Ti3C2/C coated PP separator (N-Ti3C2/C@PP) could not only efficiently prevent the shuttling of polysulfides, but also successfully suppress the dendrite growth of lithium anodes. Therefore, the Li-S batteries with N-Ti3C2/C@ PP separator exhibit a high specific capacity of 1332 mAh g(-1) at 0.1 C and an extended cycling stability of 0.07% per cycle capacity decay for 500 cycles at 0.5 C at sulfur loading of 3.4 mg cm(-2). Even at a higher sulfur loading over 10 mg cm(-2), these Li-S batteries still deliver a high and stable areal capacity of 6.3 mAh cm(-2).