Functional separator consisted of polyimide nonwoven fabrics and polyethylene coating layer for lithium-ion batteries

In this paper, a composite membrane with nonwoven polyimide (PI) membrane as structural support and polyethylene (PE) particles coating layer as a thermal shutdown layer, is fabricated as the separator for lithium-ion battery. Different from PI nonwoven membrane, the PE coating PI nonwoven composite membrane (PE–PI–S) not only shows excellent thermal shutdown function, similar to traditional multilayer PP/PE/PP separator, but also exhibits much higher thermal stability, better wettability to the polar electrolyte and lower internal resistance than the PP/PE/PP separator. The electrolyte uptake and ionic conductivity of PE–PI–S increase from 58%, 0.84 mS cm−1 to 400%, 1.34 mS cm−1, respectively. Furthermore, the thermal shutdown function of PE–PI–S can be controlled widely in the temperature range from 120 °C to more than 200 °C while the multilayer PP/PE/PP separator only with a shutdown temperature range from 130 °C to 160 °C. Lithium ion battery with PE–PI–S nonwoven separator also shows excellent stable cycling and good rate performance.