High-Energy LiNiO Li Metal Batteries Enabled by Hybrid Electrolyte Consisting of Ionic Liquid and Weakly Solvating Fluorinated Ether.

In pursuit of the highest possible energy density, researchers shift their focus to the ultimate anode material, lithium metal (Li), and high-capacity cathode materials with high nickel content (Ni > 80%). The combination of these aggressive electrodes presents unprecedented challenges to the electrolyte. Here, we report a hybrid electrolyte consisting of a highly fluorinated ionic liquid and a weakly solvating fluorinated ether, whose hybridization structure enables the reversible operation of a battery chemistry based on Li and LiNiO (Ni = 100%), delivering nearly theoretical capacity of the latter (up to 249 mAh g) for >300 cycles with retention of 78.