Two-dimensional metal-organic framework with perpendicular one-dimensional nano-channel as precise polysulfide sieves for highly efficient lithium-sulfur batteries

Although they are regarded as one of the most promising energy storage devices, lithium-sulfur batteries still suffer from severe “shuttle effects”, which limit their further applications. In this work, a unique two-dimensional metal-organic framework with a small perpendicular one-dimensional channel (5.2 Å) was prepared and employed as a highly efficient ion sieve to suppress notorious “shuttle effects” in Li-S batteries. The thin but closely packed laminar-like 2D CuBDC sheets could effectively suppress the shuttle of polysulfides and cause facile transport kinetics of the lithium ions during cycling. Consequently, after use as a functional separator in an Li-S battery, a capacity of 830 mA h g⁻¹at 1 C was obtained after a long cycling period of 1000 cycles. The excellent capacity of 795 mA h g⁻¹could still be obtained when cycled at 0.5 C after 500 cycles under a high sulfur loading of 5.2 mg cm⁻², suggesting the superb polysulfide sieving ability of 2D CuBDC sheets.