Effect of Urea as Electrolyte Additive for Stabilization of Lithium Metal Electrodes

Owing to its lowest standard redox potential, low density, and high theoretical specific capacity, lithium metal has been considered to be the ideal anode material for secondary lithium batteries. However, lithium metal is thermodynamically unstable in liquid organic electrolytes (LOEs). When lithium metal comes in contact with an LOE, it reacts easily with it to form the solid electrolyte interphase (SEI) layer. Once the stable and robust SEI layer forms, it can inhibit the direct contact between lithium metal and LOE and the further decomposition of the electrolyte. Nevertheless, the inhomogeneity in chemical composition or thickness of the SEI layer can cause the growth of lithium dendrites, which lead to short-circuits in batteries. In this study, we suggested the use of urea as a new electrolyte additive to restrain the growth of lithium dendrites via the formation of a uniform and robust SEI layer on the lithium surface. The Li symmetric cell with 0.5 M urea electrolyte additive exhibited better cyclability over 415 cycles at 1 mA cm–2; this number of cycles was >40 times larger than that of the Li symmetric cell without urea additive. Further, the Li–O2 cell with electrolyte additive was cycled for more than 200 cycles at 0.1 mA cm–2 under the limited capacity mode of 1000 mA h g–1.