Expanded polytetrafluoroethylene reinforced polyvinylidenefluoride–hexafluoropropylene separator with high thermal stability for lithium-ion batteries

PVDF–HFP/ePTFE composite separator with high thermal stability and low thermal shrinkage characteristic has been developed. The PVDF–HFP acts to absorb the electrolyte and shutdown at elevated temperature. The thermally stable ePTFE matrix is adopted to improve the mechanical strength and sustain the insulation after the shutdown. This novel separator presents good ion conductivity (up to 1.29 mS cm−1) and has a low thermal shrinkage of 8.8% at 162 °C. The composite separator shutdown at 162 °C and keep its integrity before 329 °C. Cells based on the composite separator show excellent capacities at high rate discharge and stable cycling performance.