Polydopamine-assisted in-situ formation of dense MOF layer on polyolefin separator for synergistic enhancement of lithium-sulfur battery
Xiuxiu Wu, Cheng Zhou, Chenxu Dong, Chunli Shen, Binbin Shuai, Cheng Li, Yan Li, Qinyou An, Xu Xu, Liqiang Mai
Abstract
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.