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.