Li metal has been known as an ideal anode material for high performance batteries due to its high theoretical specific capacity and lowest working potential. However, Li metal is thermodynamically unstable in polar aprotic electrolytes: it reacts with the electrolytes to form a solid electrolyte interface (SEI) layer. This layer, when a stable SEI layer is formed, it can prevent the direct contact between Li metal and liquid electrolyte and further decomposition of the electrolyte. Nevertheless, the non-uniform chemical composition of the SEI layer can induce an uneven current distribution on the Li surface, which causes Li dendrite growth and resulting electric short circuit. Thus far, approaches focused on making the stable and uniform SEI layer to prevent Li dendrite formation from modulating the electrolyte component and preventing the use of electrolyte additives.

In the present work, we suggest the use of an electrolyte additive for forming a uniform and stable SEI layer on Li surface for suppressing the growth of Li dendrite. The base electrolyte of 1 M LiTFSI in TEGDME was used for tests. The Li symmetric cell containing the electrolyte additive was galvanostatically cycled over 500 cycles for each charge and discharge time of 2 h at a current density 1 mA cm^-2, which was >50 times longer than that of the Li symmetric cell without additive in electrolyte. This electrolyte additive helps to make a stable and uniform SEI layer, leading to effectively suppressing the growth of Li dendrite. Further, the electrolyte additive can be used in the Li metal based batteries such as a Li-O₂ battery. The Li-O₂ cell containing the additive was cycled for longer than 200 cycles at a current density of 0.1 mA cm^-2 under the limited capacity mode of 1000 mAh g^-1, which was >4 times longer than that of the Li-O₂ cell without the additive in electrolyte. This electrolyte additive remarkably improved the electrochemical performance, especially cyclability of Li-O₂ batteries.