Polydopamine coated poly(m-phenylene isophthalamid) membrane as heat-tolerant separator for lithium-ion batteries

Poly(m-phenylene isophthalamide) (PMIA) membranes are promising heat-tolerant separator candidates of lithium-ion batteries (LIBs), while their wettability toward carbonate electrolyte and corresponding batteries performance are not desirable. Herein, PMIA membranes coated with ultrathin mussel-inspired polydopamine (PDA) layer were fabricated as separators in LIBs. The introduced amino, quinonyl, and catechol groups in PDA coating could enhance the wettability of the resultant PMIA-PDA separator toward electrolyte. The PMIA-PDA separator had excellent thermal stability, showing a thermal shrinkage of 5.2% at 200 °C. The contact angle of the thermal-treated PMIA-PDA separator could maintain at 26.1°, which decreased by 42.7% compared with the pristine PMIA separator. The PMIA-PDA separator also displayed a high ionic conductivity (0.86 mS cm −1 ) and a low interfacial electric resistance (62.4 Ω). Consequently, the assembled LiCoO 2 /PMIA-PDA/Li battery achieved good cyclic stability with the capacity retention of 84.3% (121.1 mAh g −1 ) after 100 cycles under 30 °C. More significantly, the relevant capacity retention remained at 89.0% (127.5 mAh g −1 ) under 60 °C, which implied a great potential of PMIA-PDA membranes as separators of high-safety LIBs.