Jones John-Paul, Jones Simon C, Krause Frederick C, Pasalic Jasmina, Bugga Ratnakumar
Jet Propulsion Laboratory , California Institute of Technology , Pasadena , California 91109 , United States.
J Phys Chem Lett. 2018 Jul 5;9(13):3751-3755. doi: 10.1021/acs.jpclett.8b01400. Epub 2018 Jun 26.
Lithium sulfur batteries promise significant improvements in specific energy compared to Li-ion, but are limited by capacity fade upon cycling. Efforts to improve durability have focused on suppressing the solubility of intermediate polysulfides in the electrolyte. Here we describe an in situ electrochemical polysulfide detection method based on the cyclic volatmmetric response. The voltammetric peaks correlate with increased discharge, consistent with increased polysulfide species in the electrolyte as demonstrated by prior literature measurements using spectroscopic methods. We verified that adding metal sulfide species to the sulfur cathode and ceramic-coatings on the polyolefin separator result in reduced polysulfide concentration, consistent with improved cycle life reported earlier. Further, the use of highly concentrated electrolytes produces no detectable dissolved polysulfide species. Future advances in Li/S technology could utilize this method to determine the polysulfide contents in the electrolyte, and thus quantify the efficacy of the sulfur-sequestering strategies.
锂硫电池有望在比能量方面比锂离子电池有显著提升，但受限于循环过程中的容量衰减。提高耐久性的努力主要集中在抑制中间多硫化物在电解质中的溶解度。在此，我们描述了一种基于循环伏安响应的原位电化学多硫化物检测方法。伏安峰与放电增加相关，这与电解质中多硫化物种类增加一致，正如先前使用光谱方法进行的文献测量所表明的那样。我们证实，向硫阴极添加金属硫化物物种以及在聚烯烃隔膜上涂覆陶瓷涂层会导致多硫化物浓度降低，这与之前报道的循环寿命改善情况相符。此外，使用高浓度电解质不会产生可检测到的溶解多硫化物物种。锂硫技术未来的进展可以利用这种方法来确定电解质中的多硫化物含量，从而量化硫固定策略的效果。
