Active sites-rich zeolitic imidazolate framework/MXene heterostructure modified separator with improved Li⁺ transport for high-performance Li-S batteries

The inevitable shuttling of lithium polysulfides (LiPSs) and poor redox kinetics restrict real-world applications of lithium-sulfur (Li-S) batteries, although they have been paid plentiful attention. Herein, a thin and multifunctional heterostructure (ZIF-L/MXene), consisting of leaf-like zeolitic imidazolate framework sheets (ZIF-L) and two-dimensional layered Ti3C2Tx MXene nanosheets, is developed for modification of polyolefin-based separators. A good combination of the merits of the ZIF-L and MXene can hinder the restacking of MXene nanosheets and achieve a large specific surface area, thus exposing plentiful active sites for adsorption and catalytic reaction of LiPSs. Taking these obviously synergistic effects, the ZIF-L/MXene heterostructure modified separators not only alleviate the shuttling of LiPSs but also promote their kinetics conversion. Furthermore, with an improved electrolyte affinity, the ZIF-L/MXene modified separators can accelerate the transport of Li+. Thus, the modified separator endows a Li-S cell with an admirable discharge capacity of 1371.7 mAh g-1 at 0.2 C and favorable cycling stability, with a slow capacity decay ratio of 0.075% per cycle during 500 cycles. Even under a sulfur loading of ~ 4.1 mg cm-2, the Li-S battery can achieve an excellent capacity of 990.6 mAh g-1 at 0.1 C and maintain an excellent cycling performance. The novel ZIF-L/MXene heterostructure modified separator in this work can provide an alternative strategy for designing thin and light separators for high-performance Li-S batteries, via the enhancement of redox kinetics and reduction of shuttling of the LiPSs.