Defect-engineered bilayer MOFs separator for high stability lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries with their low price, high energy density, and environmental friendliness are considered as an ideal candidate for next generation energy storage devices. However, their development is heavily impeded by the polysulfide shuttle and inevitable growth process of lithium dendrites. In order to solve these problems simultaneously, herein, a defect-engineered separator was designed based on the commercial polypropylene (PP) substrate by constructing defective and defect-free Cu3(BTC)2 (HKUST) metal organic frameworks (MOFs) on each side. On the cathode side, the existence of defects on the HKUST MOFs enhanced the Cu atoms catalytic activity and could act as "blockers" to inhibit polysulfide shuttling through Lewis acid-base interactions. Meantime, at the anode side, defect-free MOFs could be used as lithium-ion guides that can balance the internal electric field, resulting in stable lithium-ion stripping/plating and uniform lithium metal deposition. As the consequences, the assembled Li–S battery with a bilayer HKUST MOFs separator showed the long-term cycling with a super low-capacities decay of 0.06% per cycle under 1000 cycles. A prospective strategy for interfacial engineering of bilayer separator is expected from this work to facilitate the development of high performance and stability Li–S battery.