Hot stretching induced Orientation of Calcium Copper Titanate Nanorods in Polyetherimide for Enhanced Energy Storage Density

Polymer dielectric composites have garnered growing attention due to their ability to combine properties of both polymers and ceramic fillers. However, the relatively low energy storage density still limits their application in continuously updating electronic capacitors. Herein, we present copper calcium titanate nanorods (CCTONRs) and polyetherimide (PEI) based dielectric composites with an enhanced energy storage density through orientating of CCTONRs achieved by hot stretching. First, 1D structured CCTONRs are synthesized and surface-modified using carboxylated polyetherimide (cPEI), offering cPEI@CCTONRs. The cPEI@CCTONRs are then incorporated into PEI matrix, followed by hot stretching, resulting cPEI@CCTONRs/PEI-HS composites. Due to the surface modification of CCTONRs, cPEI@CCTONRs are homogeneously dispersed in PEI matrix. Additionally, an 100% hot stretching ratio leads to an orientation degree of 18.4% of cPEI@CCTONRs within the composite. As a result, the dielectric constant of the hot stretched composite film with 15 wt% cPEI@CCTONRs reaches 10.14, with its breakdown strength remaining at a high level of 467.4 MV·m^-1. Therefore, the discharged energy density of this composite can be up to 10.1 J·cm^-3, which is 2.52 times to that of pure PEI. This work is highly feasible for the development of outstanding performance energy storage materials for film capacitor with high-density energy storage.