Tailoring anisotropic thermal conductivity of 2D aramid nanoribbon-based dielectrics with potential high-temperature capacitive energy storage†

Polymer dielectrics operating at >150 °C with exceptional capacitive energy storage are crucial for electric and electronic devices. When exposed to high electric fields and temperatures, efficient heat management is paramount in dissipating Joule heat and minimizing leakage current. However, polymers naturally exhibit low thermal conductivity. Herein, we demonstrate the realization of high anisotropic thermal conductivity in dielectrics based on 2D aramid nanoribbons (ANRs), showing great potential for high-temperature capacitive energy storage applications. Nanodiamond (ND) fillers, surface-modified with poly-dopamine (PDA), are intercalated between the hierarchically assembled ANR layers along the in-plane direction, forming ND@PDA-ANR composite dielectrics. By optimizing the filler loading ratio to 20 wt%, an impressive in-plane thermal conductivity of 17.13 W m⁻¹ K⁻¹ and a remarkable anisotropic ratio of 39.84 are achieved. As validated in electric–thermal–mechanical coupling models solved using the phase field method, the thermal breakdown is effectively suppressed, allowing for a high breakdown strength of 302 kV mm⁻¹ at 150 °C. This contributes to an enhanced energy density of 2.42 J cm⁻³ at 150 °C, representing a substantial 806.7% improvement compared to the pristine dielectric. Simultaneously, the efficiency remains at above 80%. Furthermore, our composite dielectrics demonstrate exceptional cycling stability, thermal stability, Young's modulus, and flexibility.