High Current-Density-Charging Lithium Metal Batteries Enabled by Double-Layer Protected Lithium Metal Anode

Abstract

The practical application of lithium (Li) metal anode (LMA) is still hindered by non-uniformity of solid electrolyte interphase (SEI), formation of “dead” Li, and continuous consumption of electrolyte although LMA has an ultrahigh theoretical specific capacity and a very low electrochemical redox potential. Herein, a facile protection strategy is reported for LMA using a double layer (DL) coating that consists of a polyethylene oxide (PEO)-based bottom layer that is highly stable with LMA and promotes uniform ion flux, and a cross-linked polymer-based top layer that prevents solvation of PEO layer in electrolytes. Li deposited on DL-coated Li (DL@Li) exhibits a smoother surface and much larger size than that deposited on bare Li. The LiF/Li2O enriched SEI layer generated by the salt decomposition on top of DL@Li further suppresses the side reactions between Li and electrolyte. Driven by the abovementioned advantageous features, the DL@Li||LiNi0.6Mn0.2Co0.2O2 cells demonstrate capacity retention of 92.4% after 220 cycles at a current density of 2.1 mA cm–2 (C/2 rate) and stability at a high charging current density of 6.9 mA cm–2 (1.5 C rate). These results indicate that the DL protection is promising to overcome the rate limitation of LMAs and high energy-density Li metal batteries.