Heteroatom Si Substituent Imidazolium-Based Ionic Liquid Electrolyte Boosts the Performance of Dendrite-Free Lithium Batteries

The high-viscosity issue of ionic liquids hinders the practical use of ionic liquid electrolytes for high-energy density batteries. Here, we demonstrate a novel heteroatom Si substituent imidazolium-based ionic liquid electrolyte, which has low viscosity and high ionic conductivity, and the heteroatom Si substituent weakens the activity of the C-2 position of imidazolium cation, prevents the formation of a highly loose lithium corrosion layer, and enables Li/LiFePO ₄ cycling with high coulombic efficiency (up to 99.7%) and greatly enhanced cycling stability. The electrolyte is intrinsically safe and stable with lithium metal, boosts the security of Li-metal usage, and enables dense-packing Li deposition of Li anode. This strategy of building heteroatom Si substituent ionic liquid is successful in reducing the viscosity, realizing safe and stable electrolyte for assembling a high-energy density battery.