Polydopamine-assisted in-situ formation of dense MOF layer on polyolefin separator for synergistic enhancement of lithium-sulfur battery

The separator is of great significance to alleviate the shuttle effect and dendrite growth of lithium-sulfur batteries.However,most of the current commercial separators cannot meet these requirements well.In this work,a dense metal-organic-framework(MOF)modification layer is in-situ prepared by the assistant of polydopamine on the polypropylene separators.Due to the unique structure and synergistic effect of polydopamine(PDA)and zeolitic imidazolate framework-8(ZIF-8),the functional separator can not only trap the polysulfides effectively but also promote the transport of lithium ions.As a result,the battery assembled with the functional separator exhibits excellent cycle stability.The capacity remains 711 mAh·g^(−1)after 500 cycles at 2 C,and the capacity decay rate is as low as 0.013%per cycle.The symmetrical battery is cycled for 1,000 h at 2 mA·cm^(−2)(2 mAh·cm^(−2))with the plating/stripping overpotential of 20 mV.At the same time,the modification separator shows a higher lithium ion transference number(0.88),better thermal stability and electrolyte wettability than the unmodified separator.