Polyimide composite separator containing surface-modified hollow mesoporous silica nanospheres for lithium-ion battery application

Polyimide (PI) hybrids of biphenyl tetracarboxylic dianhydride (BPDA) and 4,4'-oxydianiline (ODA), containing surface-treated hollow mesoporous silica (AHMS) nanospheres, are synthesized by chemical imidization and freeze-drying. The resulting xerogels exhibit high ionic conductivity and heat resistance. The volume shrinkage of the wet gels, which occurs during the drying process, is avoided by adding AHMS nanoparticles, resulting in the formation of a robust network structure of PI hybrid xemgels as a crosslinker. The cross-sectional structure of the xerogels containing AHMS nanospheres exhibits a network of interconnected polyimide microfibers. Lithium ion batteries are fabricated by inserting the PI hybrid xerogel separator between electrodes. In the repeated charge/discharge experiment, the electrolyte uptake and interfacial compatibility of the PI hybrid xerogel separator are improved significantly compared to those measured from the PI separator.