Yang Bin, Jiang Haoran, Zhou Yucun, Liang Zhuojian, Zhao Tianshou, Lu Yi-Chun
Electrochemical Energy and Interfaces Laboratory, Department of Mechanical and Automation Engineering , The Chinese University of Hong Kong , Shatin , N.T. 999077 Hong Kong SAR , China.
HKUST Energy Institute, Department of Mechanical and Aerospace Engineering , The Hong Kong University of Science and Technology , Clear Water Bay , Kowloon 999077 , Hong Kong SAR , China.
ACS Appl Mater Interfaces. 2019 Jul 24;11(29):25940-25948. doi: 10.1021/acsami.9b07048. Epub 2019 Jul 10.
Lithium-sulfur batteries offer a high theoretical gravimetric energy density and low cost, but the full utilization of the sulfur electrode has been limited by the premature passivation of insulating lithium sulfide (LiS). Anion has been one of the major parameters to improve Li-S batteries in addition to solvent, additives, and electrode structures. Here, we reveal the role of anion donicity on the passivation of Li-S battery and its underlying working mechanism. We show that anions with high donicity effectively reduce the charge-transfer resistance during the cycling of Li-S cells and alleviate the LiS passivation by transforming the dense film LiS to porous three-dimensional flake LiS. UV-vis spectroscopy revealed that anions with higher donicity exhibit higher LiS solubility, which is consistent with their stronger bonding to Li, as revealed by nuclear magnetic resonance and density functional theory calculations. Our study reveals the role of anion donicity in LiS passivation and its underlying mechanism, offering rational design consideration for electrolyte salts in achieving high sulfur utilization and high energy efficiency for Li-S batteries.
锂硫电池具有较高的理论重量能量密度和低成本，但硫电极的充分利用受到绝缘硫化锂（LiS）过早钝化的限制。除了溶剂、添加剂和电极结构外，阴离子一直是改善锂硫电池的主要参数之一。在此，我们揭示了阴离子给电子性对锂硫电池钝化的作用及其潜在的工作机制。我们表明，具有高给电子性的阴离子有效地降低了锂硫电池循环过程中的电荷转移电阻，并通过将致密的LiS膜转变为多孔三维片状LiS来减轻LiS钝化。紫外可见光谱表明，具有较高给电子性的阴离子表现出较高的LiS溶解度，这与核磁共振和密度泛函理论计算所揭示的它们与Li更强的键合一致。我们的研究揭示了阴离子给电子性在LiS钝化中的作用及其潜在机制，为实现锂硫电池的高硫利用率和高能效的电解质盐提供了合理的设计考量。
