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 Al 2 O 3 composite separator is prepared with a phase inverse method. The colloidal Al 2 O 3 particles well dispersed in the PVDF‐HFP polymer matrix substantially enhance the mechanical strength of the PVDF‐HFP separator. The PVDF‐HFP/colloidal Al 2 O 3 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 Al 2 O 3 separator only has a 4.5% thermal shrinkage at 150 °C and exhibits high electrochemical performances upon annealing at 140 °C.