Li-IL@CuBTC-enhanced PEO composite polymer electrolytes for solid-state lithium batteries

초록

Polymer electrolytes in lithium batteries typically suffer from low ionic conductivity and unstable interactions with lithium metal, limiting their applicability in high-energy-density systems. To address these challenges, a novel nanoporous filler (Li-IL@CuBTC) was synthesized by encapsulating a lithium-containing ion-conductive liquid within the CuBTC metal–organic framework (MOF), and this filler was incorporated into a polyethylene oxide (PEO) matrix to form a composite polymer electrolyte. The multifunctional filler enhances ion transport, suppresses PEO crystallinity, and improves electrolyte stability. Consequently, the composite polymer electrolyte has a broad electrochemical stability window (5.9 V), strong ionic conductivity (1.2 × 10⁻4 S cm⁻¹ at room temperature), and a high lithium-ion transference number (0.69), along with excellent compatibility with lithium metal. In LFP/PLLC/Li full cells operated at 60 °C, the electrolyte delivers outstanding cycling stability, maintaining reversible capacities of 160.5 mAh g⁻¹ after 200 cycles at 0.2 C and 151.5 mAh g⁻¹ after 250 cycles at 0.2 C and 2 C respectively. This study demonstrates an effective strategy for improving composite polymer electrolytes, offering promising potential for safe, durable, and high-energy-density energy storage systems. © The Author(s), under exclusive licence to Korean Carbon Society 2026.

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