PVDF composites reinforced by dispersed Al2O3 particles for thermally and mechanically stable separators in lithium-ion battery

The performances and safety of lithium-ion batteries (LIBs) strongly depend on the integrity of the separators, that prevent immediate contact between cathodes and anodes in battery. To enhance the stability of lithium-ion batteries at high-temperature, incorporating inorganic materials such as Al₂O₃ into polymer composites is advisable for separators applications. Here, we fabricated polyvinylidene fluoride (PVDF) composite membranes reinforced with alumina (Al₂O₃) in nanopowder (PVDF/Al₂O₃) and colloidal form (PVDF/ c- Al₂O₃) via phase inversion. The results show that colloidal Al₂O₃ particles were evenly distributed within the PVDF membranes compared to the PVDF/Al₂O₃ composites, which led to minimal shrinkage up to 200 °C, high ionic conductivity (4.0 × 10⁻³ S cm⁻¹), and improved mechanical strength. Significant strengthening and the strain rate sensitivity coefficients on mechanical properties of the resulted composites were also determined. Batteries assembled with the PVDF/ c- Al₂O₃ composites as separators demonstrated stable capacity retention of 96.8 % after 70 charge-discharge cycles at 0.2 C. These findings suggest that PVDF/ c- Al₂O₃ composites are promising thermally and mechanically durable separators for advanced lithium-ion battery applications.