Self-assembled Protective Layer by Symmetric Ionic Liquid for Long-cycling Lithium-Metal Batteries

A lithium (Li) metal is expected to be an ideal anode material for energy-dense storage devices due to its intrinsic high capacities (3,860 mAh g^-1). However, its practical implementation was hindered by a dendritic Li deposition, which exacerbates the cycling efficiency of Li-metal batteries. Herein, we present a novel ionic liquid (IL) electrolyte additive modified by symmetric alkyl chains to control the Li deposition. This symmetric design generated a self-assembled lithiophobic shielding layer on Li protuberances, leading to the smooth deposition of Li. In addition, our symmetric ILs stabilized electrode interphase with higher inorganic components by anchoring counter anions near the Li-metal electrode. As a result, our symmetric IL enabled reliable cycling of Li-LiNi_0.6Co_0.2Mn_0.2O₂ cell (three times excessed Li) with high Coulombic efficiency (~99.8%) over 250 cycles. In this presentation, I will discuss a new design protocol for IL-based electrolytes and provides a promising way to high efficiency, stable-cycling Li-metal batteries.