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. A highly efficient,porous and thermally stable composite separator of PVDF‐HFP/colloidal alumina is prepared using a phase inverse method. The higher adsorption energy owing to the citrate acid ligand on Al2O3 surface enhances the mechanical strength of the separator and the composite separator exhibits pronounced electrochemical performances, rate capacity, and cycling stability.