(Digital Presentation) Polydopamine-Functionalized Bacterial Cellulose As Biopolymer Separator for Lithium-Sulfur Batteries

Li-S chemistry is regarded as promising next-generation battery technology, but the development of Li-S battery technology is severely impeded by the challenges of polysulfide shuttling and lithium dendrite formation. To address these issues, we coated polydopamine on bacterial cellulose (BC) to create a biopolymer separator. BC provides its dense network, while the presence of polydopamine offers dense polar functional groups to curb polysulfide shuttling by confining them in the sulfur cathode side. Such a separator, with the uniform distribution of nanoscale pores and functional chemical groups, also ensures a consistent Li⁺ flux at the anode surface, thus addressing the problem of lithium dendrite formation. Our results suggest that this polydopamine/BC-based biopolymer separator has superior performance over the commercial polyolefin-based separator. In particular, the Li-S batteries assembled with this biopolymer separator exhibited a specific discharge capacity of 1449 mAh/g at 0.1C and 909 mAh/g at 1C, while showing a small capacity fade of 0.023% per cycle.