High ionic conductivity polymer electrolytes for quasi-solid-state lithium-metal batteries enabled by in situ polymerization

Lithium metal batteries have emerged as a focal point for next-generation energy storage technologies due to their high safety and energy density. However, for most polymer electrolytes, low ionic conductivity at room temperature (<10⁻⁴ S cm⁻¹), insufficient mechanical strength, and low lithium transference number (t_Li+ < 0.5) are significant barriers to practical usage. Herein, the high-performance HFBA and PAN modified PVDF-HFP-based quasi-solid polymer electrolyte 40HP is successfully produced using a novel monomer in-situ polymerization technique. The formation of a three-dimensional interconnected network structure in the electrolyte effectively suppresses polymer chain crystallization and promotes β-phase formation, achieving multiple breakthrough metrics: tensile strength of 4.0 MPa, ionic conductivity at room temperature of 1.16 × 10⁻³ S cm⁻¹, lithium transference number reaches 0.75, and electrochemical window of 4.7 V. The Li||Li symmetric cells assembled with 40HP maintain stable cycling for over 1000 h at 0.1 mAh cm⁻² without dendrite penetration. The NCM811|40HP|Li full cell exhibits a capacity retention rate of 60.2% after 200 cycles at 0.2C. This work demonstrates the synergistic enhancement of polymer electrolyte performance through HFBA-PAN co-modification, providing a scalable electrolyte regulation strategy for developing high-safety, high-energy-density quasi-solid-state lithium batteries.