Enhanced capacitive performance through integration of electrical insulation and thermal conductivity

Polymer electrostatic capacitors are important in advanced power electronic systems due to their high voltage resistance, rapid charge-discharge rate, and reliable performance. Growing demands from emerging fields such as hybrid vehicles, oil and gas exploitation, and aerospace power systems escalate the need for polymer dielectrics capable of high operating temperatures exceeding 150℃. However, commercial dielectric biaxial-oriented polypropylene suffers from low energy storage density and limited operating temperature (<105 ℃).

Polyetherimide (PEI) has recently attracted widespread attention due to its high glass transition temperature and low dielectric loss. Unfortunately, the leakage current of this aromatic polymer increases dramatically at elevated temperatures, leading to an increased conduction loss. High conduction loss not only reduces discharge energy efficiency and energy density but also generates substantial Joule heat which poses a significant risk to the lifespan of the capacitive components. Therefore, the integration of high electrical insulation and thermal conductivity is of vital importance for high-temperature dielectrics.

In a new study published in Advanced Powder Materials, a team of researchers from Central South University in China, and University of Wollongong In Australia, presented a strategy to integrate high electrical insulation and high thermal conductivity by bonding carbon quantum dots (CQDs) with the diamine monomer of polyetherimide (PEI). CQDs were synthesized at the kilogram scale, which were then incorporated as bonding sites to form a crosslinked network, combining the Coloumb blockade effect, to effectively “trap free electrons and extend the trajectory of unbound electron movement,” explains lead author Xiaona Li. “As a result, the hybrid dielectrics PEI-NH₂-CQDs demonstrate a significantly improved electrical resistivity at 200℃.” Furthermore, an improved energy density of 3.6 J cm^-3 with a discharged energy efficiency exceeding 90% was achieved at 200 ℃, together with a high thermal conductivity of 0.65 W m^-1 K^-1 for PEI-NH₂-CQDs. “Taken together, these qualities superior thermal stability and reliability of the capacitors, reinforcing the potential of this dielectric in the field of high-temperature energy storage applications,” adds Li. “Our results pave the way for large-scale production of reliable PEI-NH₂-CQDs dielectrics.”

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Contact the author: Hang Luo (hangluo@csu.edu.cn). State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, P. R. China.

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