Advanced Flexible and Porous Gel Polymer Electrolytes Based on a Photocrosslinked Thiol-Ene/Hydroxyethyl Cellulose Semi-Interpenetrating Polymer Network for Lithium-Ion Batteries

Abstract

Cross-linked gel polymer electrolytes for lithium-ion batteries were prepared using a unique photocrosslinking technology. Hydroxyethyl cellulose was dissolved in N-vinylpyrrolidone and combined with polyethylene glycol diacrylate, trimethylolpropane triacrylate, and pentaerythritol tetrakis(3-mercaptopropionate), then subjected to UV irradiation to form a semi-interpenetrating network. This cross-linked structure enhanced stability and compatibility with liquid electrolytes and significantly improved ionic conductivity (2.14 × 10−3 S cm−¹) compared to hydroxyethyl cellulose-based GPEs. The hydrophilic hydroxyethyl cellulose blend and flexible pentaerythritol tetrakis(3-mercaptopropionate) contributed to improved mechanical and thermal stability, increased liquid retention, and reduced electrolyte leakage. The GHPT-3 electrolyte exhibited electrochemical stability up to 4.5 V and delivered excellent cycling performance in a lithium metal cell with a LiFePO₄ cathode, providing a high reversible capacity of 155.8 mAh g−¹ at 0.1 C with near-perfect coulombic efficiency. Remarkably, it retained 90.3% of its initial discharge capacity after 100 cycles. GHPT-3 effectively suppressed lithium dendrite formation for over 1000 h, outperforming a commercial liquid electrolyte, which failed within 895 h. These advancements highlighted GHPT-3's potential as a safer, high-performance electrolyte for lithium-ion batteries.