Ionic Liquid Boosting the Electrochemical Stability of a Poly(1,3‐dioxolane) Gel Electrolyte for High‐voltage Solid‐State Lithium Batteries.

Poor interfacial contact between solid‐state electrolytes and electrodes limits high‐voltage performance of solid‐state lithium batteries. A new gel electrolyte is proposed via in‐situ polymerization, incorporating fluoroethylene carbonate (FEC) solvent and ionic liquid1‐butyl‐1‐methylpiperidinium bis(trifluoromethylsulfonyl)imide (PP14TFSI). This combination synergistically enhances Li ion transport, achieving a transfer number of 0.58 and improved electrochemical performance. FEC protects the Al current collectors from LiPF6 corrosion and promotes a protective interfacial layer formation. PP14TFSI improves interfacial contact and provides stable components. An interface layer of fluorine and nitrogen composites forms, preventing side reactions. LiCoO2||PPE||Li cell exhibits robust cycling stability at 4.45 V, retaining ~80 % capacity after 200 cycles at room temperature with 0.2 C and 1 C rates, showing increased coulombic efficiency. NCM811||PPE||Li cell also displays exceptional cycling. In‐situ polymerization and FEC‐ionic liquid coordination enable high‐voltage solid‐state lithium metal batteries for practical use. [ABSTRACT FROM AUTHOR]