Covalent organic frameworks (COF)/CNT nanocomposite for high performance and wide operating temperature lithium–sulfur batteries

Lithium-sulfur (Li–S) batteries as the most promising rechargeable batteries are still facing severe challenges, such as fast capacity fade, poor cycling stability, and low sulfur utilization, mainly due to the dissolution/migration of soluble reaction intermediates during cycling. Here, a novel functionalized separator has been designed to trap the dissolved polysulfide by the facile strategy of functional coated separator which combining covalent organic frameworks with interlude Carbon Nanotubes network (COF-CNT-separator). Notably, it acts as an ionic sieve in Li–S batteries and a house for polysulfide, which selectively sieves Li+ ions and successfully confine the polysulfide within the cathode region. The battery exhibited a high reversible capacity of 1068 mAh g−1 at 1 A g−1 after the first cycle and capacity of 621 mAh g−1 after 500 cycles (sulfur content of 80% in cathode). When its high and low temperature performance were investigated, it finds that Li–S battery is suitable for a wide range of temperatures, from −10 to 50 °C, delivering a high utilization rate of sulfur, an excellent rate and cycle performance, and outstanding life cycle. Therefore, this facile strategy of combining separator with special network is an effective candidate for achieving high performance Li–S batteries. [Display omitted] •COFs/CNT, which was used for separator modification, was prepared by a simple way.•COFs can adsorb polysulfide, and CNT has good electrical and ionic conductivity.•COFs/CNT can selectively sieve Li+ ions and block the passage of polysulfide.•The COFs/CNT based LSBs shows excellent performance in a wide temperature range.•COFs/CNT modified separator shows great potential for commercialization of LSBs.