A novel polymer-modified separator for high-performance lithium-ion batteries

Abstract

In this study, hyperbranched polybenzimidazole (HBPBI) was synthesized and coated on polyethylene membrane surface with terephthaldehyde (TPA) cross-linker to obtain high-performance CHBPBIE separator for application in lithium ion battery (LIB). The introduction of benzimidazole, amino and carboxyl groups to TPA cross-linked HBPBI (CHBPBI) could improve the wettability, electrolyte uptake, heat resistance and thermal stability of CHBPBIE separator. The absorption of the liquid electrolyte is increased from 90% for the control separator to 181% for CHBPBIE separator. More importantly, the cross-linked coating structure can greatly improve the ionic conductivity of CHBPBIE separator, and it is 0.77 mS cm−1 at 25 °C, which is increased by 10.6 times compared with that of the control PE separator. The LIB half cells assembled with CHBPBI modified separator shows 73% increase in power capability at 7 C rate and a discharge capacity retention rate of 91.1% after 400 cycles at 2 C rate. Thus, the modified separator has the potential for use in high-performance LIB.