▎ 摘　　要

Polymer-based materials with a high dielectric constant show great potential for energy storage applications. Since the intrinsic dielectric constant of most polymers is very low, the integration of carbon nanotubes (CNTs) into the polymers provides an attractive and promising way to reach a high dielectric constant owing to their outstanding intrinsic physical performances. However, these CNT-based composites usually suffer from high dielectric loss, low breakdown strength and the difficulty to tailor the dielectric constant. Herein, we have designed and fabricated a new class of candidates composed of graphene oxide-encapsulated carbon nanotube (GO-e-CNT) hybrids. The obtained GO-e-CNT-polymer composites not only exhibit a high dielectric constant and low dielectric loss, but also have a highly enhanced breakdown strength and maximum energy storage density. Moreover, the dielectric constant of the composites can be tuned easily by tailoring the loading of GO-e-CNTs. It is believed that the GO shells around CNTs play an important role in realizing the high dielectric performances of the composites. GO shells can not only effectively improve the dispersion of CNTs, but also act as insulation barriers for suppressing leakage current and increasing breakdown strength. Our strategy provides a new pathway to achieve CNT-based polymer composites with high dielectric performances for energy storage applications.