基于锂掺杂分子筛改性隔膜的高性能锂硫电池

High-performance lithium-sulfur batteries enabled by a separator modified by lithium-doped zeolite

锂硫电池在下一代高能量密度可充电电池中极具吸引力,但多硫化物严重的穿梭效应阻碍了它的实际应用。本工作利用离子交换法成功地制备了一种锂掺杂分子筛(Li@CHA),并将其与氧化石墨烯(GO)结合用于修饰常规聚丙烯隔膜,以缓解锂硫电池的穿梭效应问题。借助扫描电镜(SEM)、能谱分析(EDS)、X射线衍射(XRD)、氮气吸-脱附法以及电化学测试,深入研究了Li@CHA的形貌、结构及用于锂硫电池的电化学性能。研究显示,Li@CHA可在隔膜表面充当“离子筛”,有效抑制多硫化物阴离子的自由穿梭,并提高锂离子的传输性能。此外,GO也可以通过化学吸附进一步抑制穿梭效应,并改善修饰层的导电性,降低电池阻抗。因此,采用这种改性隔膜的锂硫电池表现出增强的反应动力学、出色的倍率性能和稳定的循环性能,在3 C下获得了638 mAh/g的高倍率容量,在0.5 C下循环500圈后仍具有71.0%的高容量保持率。本工作为抑制多硫化物的穿梭效应提供了一条新的思路,有望进一步推动锂硫电池的实际应用。

Although lithium-sulfur batteries are attractive for next-generation high-energy density rechargeable batteries,their practical uses are limited by the severe shuttle effect of polysulfides.In this study,a lithium-doped zeolite(Li@CHA)was effectively prepared using an ion-exchange technique and combined with graphene oxide(GO)to alter the conventional polypropylene separator to alleviate the shuttling problem of lithium-sulfur batteries.The morphology,structure,and electrochemical performance of Li@CHA were thoroughly studied using a scanning electron microscope,energy-dispersive X-ray spectroscopy,X-ray powder diffraction,and nitrogen adsorption-desorption technique and electrochemical measurements.The results revealed that the Li@CHA could act as an"ionic sieve"of the separator,efficiently hindering the free shuttle of polysulfide anions and enhancing the transport performance of Li+.Additionally,GO could suppress the shuttle effect through chemisorption,and improve the conductivity of the altered layer,thereby reducing the impedance of the battery.Hence,the lithium-sulfur battery employing the modified separator demonstrated enhanced reaction kinetics,excellent rate capability,and stable cycling performance,achieving a high rate capacity of 638 mAh/g at 3 C and a high capacity retention rate of 71.0%after 500 cycles at 0.5 C.This work provides a novel idea for suppressing the shuttle effect of polysulfides,which is anticipated to further promote the practical application of lithium-sulfur batteries.