PVDF/PAN blend separators via thermally induced phase separation for lithium ion batteries

Abstract

PVDF/PAN blend porous membranes were prepared via thermally induced phase separation (TIPS) and used as separators for lithium ion batteries. TIPS behavior was investigated in detail to control the morphology, pore size, porosity, and mechanical properties of the blend separators as a function of PAN content. Rod-like pores are the typical structure resulted from solid−solid phase separation, while the pore size and porosity decrease with an increase of PAN in the blend. The introduction of PAN enhances the tensile strength and the thermal stability of the blend separator. The electrolyte uptake and the ionic conductivity reduce correspondingly with the decrease of the pore size and the porosity. However, the graphite/polymer electrolyte/LiFePO4 batteries with the blend separators exhibit higher C-rate performance, and better reversible charge/discharge cycle stability than those with PVDF separators and the commercial Celgard 2400.