Enhanced performance of modified HDPE separators generated from surface enrichment of polyether chains for lithium ion secondary battery

Porous high density polyethylene (HDPE) membrane is an important type of separator for lithium ion batteries (LIBs). To improve the electrochemical performances of HDPE-based separators, a copolymer of poly(ethylene-block-ethylene glycol) (PE-b-PEG) was blended into porous HDPE separators via TIPS process. By measuring the composition, morphology and crystallinity, etc., the phase behavior and surface enrichment behavior of the HDPE/PE-b-PEG/LP system were studied. Compared with pure HDPE separators, surface enrichment of PE-b-PEG chains enhanced the compatibility between separators and liquid electrolyte and electrodes. The ionic conductivity of liquid electrolyte soaked blend separator was up to 1.24×10−3 S cm−1 at 25 °C. Furthermore, the interface resistance between separator and electrode was effectively reduced by the surface enriched polyether chains. All the results indicated that PE-b-PEG could be a promising blend substance to improve the electrochemical performances of HDPE separators prepared via TIPS process.