Stable and Ion-Conductive Polymeric Lithicone for Lithium Metal Anode Protection

Lithium (Li) metal batteries are becoming increasingly appealing for electric mobility and other high-tech applications as they offer high energy density advantage coming from the utilization of Li metal anode with an ultrahigh theoretical specific capacity and an extremely low reduction potential. However, the practical application of Li metal anode is hampered by a variety of issues. These include dendrite formation which poses a risk for fire, formation of unstable solid electrolyte interphase (SEI) and “dead” Li resulting in a fast capacity fading, which are aggravated at high current densities. In this work, we report Li metal protection by a lithium-glycerol lithicone (LGL) layer formed by utilizing <i>tert</i>-butoxide and glycerol precursors in a molecular layer deposition process. The as-formed protection layer shows a good stability and a high ionic conductivity. The performance of the LGL-protected Li metal anode (LGL@Li) is demonstrated in both symmetric and full cell configurations at high current densities. The LGL@Li||LGL@Li cells demonstrate improved cycling stability compared with Li||Li cells during Li metal stripping/plating process at ~ 2.3 mAcm^-2 (2C) and areal capacity of 1.1 mAhcm^-2. Furthermore, LGL@Li||NMC622 cells show a capacity retention of ~ 87 % compared with ~ 35 % for Li||NMC622 cells after 200 cycles at a high current density of 2.1 mAcm^-2 (C/2). Our results show that LGL protection strategy is promising for practical Li metal batteries.