Improving the properties of HDPE based separators for lithium ion batteries by blending block with copolymer PE-b-PEG

 To improve the performances of HDPE-based separators, polyether chains were incorporated into HDPE membranes by blending with poly(ethylene-block-ethylene glycol) (PE-b-PEG) via thermally induced phase separation (TIPS) process. By measuring the composition, morphology, crystallinity, ion conductivity, etc, the influence of PE-b-PEG on structures and properties of the blend separator were investigated. It was found that the incorporated PEG chains yielded higher surface energy for HDPE separator and improved affinity to liquid electrolyte. Thus, the stability of liquid electrolyte trapped in separator was increased while the interfacial resistance between separator and electrode was reduced effectively. The ionic conductivity of liquid electrolyte soaked separator could reach 1.28×10^-3 S·cm¹ at 25℃, and the electrochemical stability window was up to 4.5 V (versus Li⁺/Li). These results revealed that blending PE-b-PEG into porous HDPE membranes could efficiently improve the performances of PE separators for lithium batteries.