Robustness 4, 4?-Diphenylmethane diisocyanate modified sponge-like porous AramidSeparators for boosting safety and electrochemical performance in lithium-ion batteries

The fabrication of novel separators with high safety and remarkable performance has always been a hot topic due to their effect on the safety and electrochemical performance of lithium-ion batteries (LIBs). In this study, the impregnation method is used to create the 4, 4 '-diphenylmethane diisocyanate (MDI) modified poly (m-phenylene isophthalamide) (PMIA) separators (PMIA-M) with 3-D sponge-like porous network structure. With the increase of cross-linking time, the elongation at break of PMIA-M separators increases to 47.2%, and the mechanical strength decreases after increasing to 31.7 MPa. In addition, PMIA-M separators has excellent thermal stability, no dimensional shrinkage at 200 degrees C and self-extinguishing property. Moreover, the expansion of polar groups improves the surface polarity of the PMIA-M separators, promoting the electrolyte-philic property and leading to a significant increase in electrochemical performance. Transport channels of Li+ can be regulated, so that the growth of lithium dendrites can be inhibited and the cycle stability is significantly improved. The capacity retention of the LiCoO2/Li cell assembled by the PMIA-M-12 separator is 94.7% after 50 cycles at 0.2C and prior to that of the pristine PMIA separator (77.6%). Therefore, the PMIA-M separators are promising material for electronic products and new energy vehicles.