Bifunctional design of cerium-based metal-organic framework-808 membrane modified separator for polysulfide shuttling and dendrite growth inhibition in lithium-sulfur batteries

Lithium-sulfur battery is perceived as one promising next generation rechargeable battery system, in view of its high theoretical specific capacity and energy density. However, the "shuttle effect" of polysulfides and the uncontrolled growth of lithium dendrites significantly obstruct its practical application. Herein, a bifunctional separator with double-sided modification is developed to simultaneously resolve these issues, which is constructed by growing continuous cerium-based metal-organic framework-808 (Ce-MOF-808) membranes on both sides of the commercial polypropylene (PP) separator through a simple in-situ growth method. On the cathode side, the Ce-MOF-808 membrane can play multiple roles of adsorption, selective sieving and catalytic conversion towards polysulfides, thereby effectively inhibiting their shuttle effect. On the anode side, the highly uniform pore distribution and polar groups of this MOF membrane ensure the fast and homogenous diffusion of lithium ions, endowing a stable lithium nucleation and growth in the cycles. Consequently, the Ce-MOF-808/PP separator exhibits a high initial specific capacity of 954.7 mAh g(-1) under 1 C with a very limited capacity fading of 0.025% in 500 cycles, and an outstanding rate capability. Moreover, the separator also ensures the stable cycling of the battery at raised sulfur loading and lean-electrolyte conditions.