Abstract
Although Li-air batteries (LAB) have a high theoretical energy density (3500 Wh kg−1), further developments are required to overcome their practical limitations. Regarding the Li-metal negative electrode (NE), we have previously reported on the reversibility of the Li dissolution/deposition reaction by using Li|Li symmetric cells with a tetraglyme (G4)-based electrolytic solution. Particularly, in the 1.0 M LiNO3/G4 electrolyte under an O2 atmosphere, a Li2O protective layer is efficiently formed on the Li-metal electrode at a current density of 0.40 mA cm−2, and Li dendrite formation is suppressed. In the present study, we expanded the test conditions (current densities up to 2.0 mA cm−2 and temperatures of 10 to 50 °C) to clarify the dissolution/deposition behavior of the Li-metal NE. The effects of two electrolyte solutions, namely LiTFSI/G4 and LiNO3/G4, on the Li-metal NE were evaluated based on cyclical testing using Li|Li symmetric cells under an O2 atmosphere. The NEs were also examined by scanning electron microscopy and X-ray photoelectron spectroscopy. The results indicated that not only LiNO3 salt but also the supply of Li and nitrate ions at the Li electrode surface are critical factors in LAB performance.
