Asymmetric cathode membrane with tunable positive charge networks for highly stable Li-S batteries

Freestanding cathodes with a high sulfur loading more than 4 mg cm(-2) are essential for practical high-energy density Li-S batteries. However, Li+ transport is sluggish and polysulfide shuffling is serious in thick cathodes, leading to rapid capacity loss and inferior rate performance. Herein, an asymmetric Li-S cathode threaded with positive charges networks was introduced by a facile phase separation strategy coupled with cationic-crosslinking method. This large-area and flexible cathode membrane shows a gradient distribution of pore structure with a skin sieving layer supported on a thick porous submatrix. This dual sulfur host reveals an inbuilt ability to suppress polysulfide shuffling in Li-S cells. Meanwhile, the positive charge networks derived from post-crosslinking endows the cathode frameworks with boosted S-n(2-) trapping ability and enhanced ionic transport kinetics. Further adjustment of the cationic networks reveals its ionic exchange mechanism in accelerating the redox reactions at the positive charge interface. As a result, composite membrane with high sulfur loading (9.1 mg cm(-2)) yields a capacity of over 8.1 mA h cm(-2) for long-term cycling. This scalable and functional asymmetric cathode design presents an alternative route toward high energy density Li-S batteries.