PNNL

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, we report a facile protection strategy for LMA using a double layer (DL) coating that consists of a polyethylene oxide (PEO)-based bottom layer which is highly stable with LMA and promotes uniform ion flux, and a cross-linked polymer-based top layer which prevents solvation of PEO layer in electrolytes. Li deposited on DL-coated Li (DL@Li) substrate exhibits a smoother surface and much larger size than that deposited on bare Li substrate. The LiF/Li2O enriched SEI layer generated by the salt decomposition on top of DL coating layer further suppresses the side reaction between Li and electrolyte. Driven by the abovementioned advantageous features, the DL@Li||LiNi0.6Mn0.2Co0.2O2 (NMC622) cells demonstrate a capacity retention of 92.4% after 220 cycles at a medium current density of 2.1 mA cm–2 (C/2 rate). Notably, the DL@Li||NMC622 cells are stable at a high charging current density of 6.9 mA cm–2 (1.5C rate). These results indicate that the DL protection has a good potential to overcome the rate limitation of LMAs and high energy-density Li metal batteries.