Size-Effects of Micropattern on Lithium Metal Surface on the Electrochemical Performance of Lithium Metal Secondary Batteries

Abstract

As lithium (Li) metal has a low reduction potential (-3.045 V vs. SHE) and a high capacity per weight (3860 mAh g-1), Li has been researched continuously as one of the fine secondary battery anode materials. However, there are some electrochemical issues that Li metal’s charge/discharge efficiency is lower than those of conventional carbon-based anode materials, and Li is intensively grown at a specific region of the Li surface and form a dendritic dendrite. Dendrites not only increase the dead Li but also lead to an internal short to cause a battery explosion. In order to solve this problem, this research group has reported that micropatterns can be formed on the surface of Li metal to successfully control Li plating/stripping position behavior In this study, we investigated how the pattern controls the shape of Li according to the charging/discharging current density, and the effect of the pattern size change on the electrochemical properties of the battery. Micropatterns of two sizes, 50 and 80 μm, are designed to have an available capacity of 1.06 and 2.44 mAh cm-2, respectively. We fabricated a micropatterned Li metal with two effective capacities and made a Li/Li symmetric cells to analyze the overpotential characteristics. The overpotential characteristic of 80 μm-patterned Li was lower than that of 50 μm-patterned Li during long charge. Also, full cells (LiNi0.6Co0.2Mn0.2O2 / 2 mAh cm-2) were fabricated with each patterned Li metals. As a result, 80 μm-patterned Li showed stable morphologic behavior inside pattern and exhibited much better electrochemical performance.