Understanding the Relationships between Morphology, Solid Electrolyte Interphase Composition, and Coulombic Efficiency of Lithium Metal.

Traditionally, dendrite growth is considered to be one of the reasons leading to poor performance of lithium metal. However, it is found that the growth of dendrites does not necessarily reduce the Coulombic efficiency (CE) of lithium metal. Here, the relationships among morphologies, solid electrolyte interphase (SEI) composition, and the CE of lithium metal have been systematically studied. By comparing different kinds of morphologies of lithium metal and the electrolytes, we discovered that SEI composition showed a great influence on the CE of lithium metal owing to the enhanced desolvation of the SEI by ionic compounds such as lithium fluoride and lithium nitride. In addition, we further developed a new method using electrochemical impedance spectroscopy of the symmetric Li-Li cell to study the properties of the SEI.