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

Abstract

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 (PP₁₄ TFSI). 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. PP₁₄ TFSI 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.

Keywords: FEC solvent; High-voltage; In-situ polymerization; Interfacial layer; Ionic liquid.