Enhanced Dielectric Energy Storage Performance of Polyimide/γ-Ga<sub>2</sub>O<sub>3</sub> Nanocomposites under Dual Trap Mechanisms
Kaige Gao, Feihua Liu, Fu Lv, Nuomei Li, Man Liu, Ziheng Ye, Minghan Yu, Rui Yin, Chen Zhang, Yu Huang, Weiwei Zhao
Abstract
The rapid development of advanced electronics, hybrid vehicles, etc. has imposed heightened requirements on the performance of polymer dielectrics. However, the energy density ( U e ) of polymer dielectrics significantly decreases due to increased leakage current and dielectric loss under high temperatures and high electric fields. Herein, γ phase Ga 2 O 3 (γ-Ga 2 O 3 ) nanoplates with wide-bandgap (∼4.7 eV) and moderate dielectric constant (∼10.0) were synthesized and incorporated into a polyimide (PI) matrix. The γ-Ga 2 O 3 nanoplates impede charge injection and transport within the nanocomposites under dual trap mechanisms, namely, deep traps introduced by band alignment at the interface between γ-Ga 2 O 3 and PI and the defective spinel structure of γ-Ga 2 O 3 with lattice defects that function as additional charge carrier traps. Additionally, γ-Ga 2 O 3 nanoplates also serve as electron scattering centers and act as electrical barriers; thus, the leakage current and conduction loss get reduced. Consequently, the nanocomposite with 1 wt % γ-Ga 2 O 3 exhibits a discharge energy density of 4.591 J cm –3 and a breakdown strength ( E b ) of 501.49 MV m –1 at 150 °C, which are significantly higher than those of commercial biaxially oriented polypropylene (BOPP) at 25 °C. Moreover, the nanocomposite exhibits remarkable cyclic stability over 120,000 cycles with only 1.2% fluctuation. This work provides a semiconductor filler strategy in the design of polymer nanocomposites for capacitive energy storage at high-temperature and high electric field environments.