With a goal of increasing energy density and reducing production cost, lithium and other metal-sulfur batteries have attracted tremendous interest due to their high theoretical energy density and the earth-abundant sulfur feedstock. However, the shuttle effect caused by soluble metal polysulfides diffusion, leading to rapid capacity decay and huge degradation of the cell electrochemical performance, is the most serious problem that metal-sulfur battery system faces and has to be addressed urgently. Both physical confinement and chemical binding strategies have been widely investigated in recent years, however it was concluded that a simple physical confinement (i.e., with carbon-based additives) is not sufficient to prevent diffusion and shuttling of polysulfides due to its weak intermolecular interactions over a long-term cell cycling, resulting in loss of active sulfur and degradation of capacity. In this talk, I will present some recent progress on surface engineered polar CeO2 as cathode additives via chemical binding in Li-S batteries, including (1) shape-controlled synthesis and redox chemistry of CeO2; 2) chemical etching surface modification of CeO2 for abundant surface defects; 3) CeO2 on cellulose derived carbon as effective interlayer. The different exposed crystal planes, Ce3+/Ce4+ redox pair, and oxygen vacancy concentration of surface engineered CeO2 play critical roles in entrapping and even accelerating the conversion rate of polysulfides.

Polar cathode additives for mitigating polysulfides shuttling in metal-sulfur batteries

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