Department of Chemical and Biomolecular Engineering , University of California, Berkeley , Berkeley , California 94720 , United States.
ACS Appl Mater Interfaces. 2019 Dec 26;11(51):47878-47885. doi: 10.1021/acsami.9b15606. Epub 2019 Dec 10.
There is a growing demand for higher energy density lithium batteries. One approach for addressing this demand is enabling lithium metal anodes. However, nucleation and growth of electronically conductive protrusions, which cause short circuits, prevent the use of this technology with liquid electrolytes. The use of rigid solid electrolytes such as polystyrene--poly(ethylene oxide) electrolytes is one solution. An additional requirement for practical cells is needed to use electrolytes with high salt concentration to maximize the flux of lithium ions in the cell. The first systematic study of the effect of salt concentration on the morphology of electrodeposited lithium through a rigid block copolymer electrolyte is presented. The nature, areal density, and morphologies of defective lithium deposits created during galvanostatic cycling of lithium-lithium symmetric cells were determined using hard X-ray microtomography. Cycle life decreases rapidly with increasing salt concentration. X-ray microtomography reveals the presence of multiglobular protrusions, which are nucleated at impurity particles at low salt concentrations; here, the areal density of defective lithium deposits was independent of salt concentration. At the highest salt concentration, this density increases abruptly by a factor of about 10, and defects were also nucleated at locations where no impurities were visible.
人们对高能量密度锂电池的需求日益增长。解决这一需求的一种方法是启用锂金属阳极。然而，电子导电突起物（即导致短路的物质）的成核和生长阻止了这项技术与液体电解质一起使用。使用刚性固体电解质，如聚苯乙烯-聚（氧化乙烯）电解质，是一种解决方案。为了在实际电池中使用高浓度盐的电解质以最大化电池中锂离子的通量，还需要额外的要求。本文首次通过刚性嵌段共聚物电解质系统地研究了盐浓度对电沉积锂形态的影响。通过硬 X 射线微断层扫描，使用恒电流循环锂-锂对称电池来确定锂沉积过程中形成的缺陷锂的形态、面密度和形貌。随着盐浓度的增加，循环寿命迅速下降。X 射线微断层扫描揭示了多球形突起物的存在，这些突起物在低盐浓度下在杂质颗粒处成核；在这里，缺陷锂的面密度与盐浓度无关。在最高盐浓度下，这一密度突然增加了约 10 倍，而且在没有杂质可见的位置也开始成核缺陷。
