Novel functional separator with self-assembled MnO₂ layer via a simple and fast method in lithium-sulfur battery

Modifying separator with metal oxides has been considered as a strong strategy to inhibit the shuttling of soluble polysulfide in the lithium-sulfur battery (Li-S battery). Manganesedioxide (MnO₂), one kind of transition metal oxide, is widely applied to decorate the PP (Polypropylene) separator. However, the fabrication by physical coating is always multistep and complicated. Here, we design a simple and fast method to chemically decorate separator. Based on the oxidizing property of acidic KMnO₄ solution, the PP separator was oxidized and an ultrathin self-assembled MnO₂ layer was directly constructed on one side of separator, by immersing in acidic KMnO₄ solution for only 1 h. The self-assembled MnO₂ layer has the synergistic effect of adsorption and catalytic conversion on polysulfides, which can effectively inhibit the shuttle effect. It can also help battery to maintain excellent electrochemical kinetics in the electrochemical cycle and maintain the effective recycling of active substances. As a result, the shuttling of polysulfide is greatly prohibited by this novel functional separator, and cycling stability is outstandingly improved, with a low-capacity decaying of 0.058% after 500 cycles at 0.5C. The rapid and simple modification method proposed in this study has a certain reference value for the future large-scale application of lithium-sulfur battery.