Improved High-Temperature Capacitive Performance of Poly(ether imide) by Copolymerization with Molecular Semiconductors

The demand for high-temperature polymer dielectrics continues to rise in fields such as smart grids, wind power generation, and electric vehicles. However, high-temperature dielectrics like poly(ether imide) (PEI) still face the issue of leakage current under electrothermal coupling fields, leading to a sharp decrease in the energy storage density. To address this challenge, we propose a molecular semiconductor copolymerization strategy, wherein 1,4,5,8-naphthalene tetracarboxylic dianhydride (NTCDA) and 3,4,9,10-perylene tetracarboxylic dianhydride are incorporated into the PEI backbone. This approach not only suppresses space charge migration but also ensures long-term leakage current stabilization, significantly improving the charge–discharge cycling stability and energy storage density. Crucially, copolymerization eliminates the risk of nanoscale phase separation between semiconductors and PEI matrices, ensuring uniform dielectric properties. By systematically optimizing the molecular semiconductor content, we demonstrate that a 0.125 mol % copolymerized PEI (NTCDA-co-PEI) achieves a remarkable energy storage density of 3.91 J/cm3 at 150 °C─double that of intrinsic PEI─while maintaining a stable dissipation factor. This work provides a scalable molecular design strategy for high-performance polymer dielectrics operating under extreme electrothermal conditions, paving the way for next-generation capacitive energy storage systems.