AlN reinforced polyethersulfone composite with stable high-energy-density via synergizing thermal management and suppressed electrical treeing

Polymer-based dielectrics have attracted considerable attention due to their high energy storage density (U) and flexibility in processing. However, polymer dielectrics suffer from conduction losses under high fields and temperatures, which reduces the discharge energy density (U_e) and charge-discharge efficiency (η), therefore, effective heat dissipation and maintaining performance at elevated temperatures remain critical challenges that require immediate solutions. In this study, we developed composite materials using polyethersulfone (PESU) as the matrix, incorporating varying mass fractions (1 wt%, 3 wt%, 5 wt%, and 7 wt%) of aluminum nitride (AlN) filler. Simultaneously, we systematically analyzed the thermal conductivity, electric field distribution, and electric tree evolution behavior of the composite material through finite element simulation. Experimental results indicate that, at room temperature, the composite material with 1 wt% AlN in PESU achieves a discharge energy density of 7.39 J/cm³ at 520 kV/mm, while maintaining a charge-discharge efficiency exceeding 93.5 %. The breakdown strength (E_b) of this composite reaches 531 kV/mm, representing a 28.9 % improvement compared to pure PESU. At elevated temperatures of 60 °C and 100 °C, the E_b of 1 wt% AlN-PESU increases by 42.1 % and 75.4 %, respectively, compared to PESU. Furthermore, simulation results confirm that the introduction of AlN filler significantly improves the thermal conductivity of the composite material, effectively suppresses local temperature rise and electric field distortion, contributing to the suppression of electric tree initiation and retards the progression toward electrical breakdown. This study provides theoretical foundation and engineering route for high-performance polymer-based dielectric materials with broad application value.