Advanced PVDF-HFP-based composite quasi-solid polymer electrolyte for high-energy lithium-ion batteries with enhanced safety and durability

The development of high-energy lithium-ion batteries (LIBs) with enhanced safety and durability requires overcoming challenges related to electrolyte instability, low ionic conductivity, and inadequate mechanical strength. This study introduces a composite quasi-solid polymer electrolyte (CQSPE) based on PVDF-HFP, optimized with Al₂O₃ nanoparticles to enhance fire retardancy, mechanical strength, ionic conductivity, and interfacial stability. The CQSPE containing 15 wt% Al₂O₃ exhibits a high ionic conductivity of 6.5 mS cm⁻¹ at 60 °C and a tensile strength of 1.56 MPa, effectively suppressing dendrite formation during cycling. The influence of CQSPE thickness (30, 60, and 90 μm) on electrochemical performance is systematically analyzed. The 60 μm membrane demonstrates optimal performance, with superior plasticizer retention and balanced mechanical properties. In a full-cell configuration (Gr-SiOx|CQSPE|NCM622), the 60 μm electrolyte delivers a reversible areal capacity of 2.61 mAh cm⁻² with 72.96 % capacity retention after 300 cycles at 0.5C. Additionally, a double-layered pouch cell with this optimized CQSPE exhibits an initial discharge capacity of 1 Ah (2.76 mAh cm⁻²) and 79.6 % capacity retention over 350 cycles at 0.5C/1C. The facile structural design of CQSPE provides a promising pathway for the development of high-performance solid-state lithium-ion batteries in the near future.