Highly Efficient PVDF-HFP/Colloidal Alumina Composite Separator for High-Temperature Lithium-Ion Batteries

Toward high-temperature lithium-ion batteries, adding inorganic materials are proposed as an effective strategy. However, inorganic particles tend to aggregate in the polymer matrix, causing degradation in battery performance. Here, a PVDF-HFP/colloidal Al₂O₃ composite separator is prepared with a phase inverse method. The colloidal Al₂O₃ particles well dispersed in the PVDF-HFP polymer matrix substantially enhance the mechanical strength of the PVDF-HFP separator. The PVDF-HFP/colloidal Al₂O₃ composite separator owns a high electrolyte uptake of 372%, a high ionic conductivity of 1.3 × 10⁻³ S cm⁻¹ at 80 °C and delivers high capacity retention of 95.6% after 100 charge–discharge cycles at 0.5 C. In addition, PVDF-HFP/colloidal Al₂O₃ separator only has a 4.5% thermal shrinkage at 150 °C and exhibits high electrochemical performances upon annealing at 140 °C.