Giant energy storage and dielectric performance in all-polymer nanocomposites

Dielectric polymers used in electrical energy storage require a combination of key metrics, including a high dielectric constant (K), low loss and high breakdown strength (E_b), all while being capable of operating at high temperatures^1-6. Decades of research into polymer-inorganic composites have achieved only limited success in reaching these goals^5,7,8. Here we introduce high-temperature immiscible blends of two dipolar polymers that, through nanophase separation, self-assemble into three-dimensional all-polymer nanocomposites. The resulting nanostructures induce coiled-chain morphology and large conformation changes, which, combined with relatively low rotational barrier and high dipole moments of both polymers, yield ultrahigh dielectric responses (K > 13) while maintaining a low loss (tanδ approximately 0.002) across a wide temperature range. Simultaneously, the nanostructured interfaces act as barriers for mobile charges, markedly reducing conduction losses at high fields and temperatures. The all-polymer three-dimensional nanocomposites with concurrently high K, high E_b and low loss deliver unprecedented discharged energy densities at elevated temperatures (18.7 J cm^-3, 15.1 J cm^-3 and 8.6 J cm^-3 at 150 °C, 200 °C and 250 °C, respectively). The approach is applicable to other immiscible dipolar blends, demonstrating its universality and tunability. This work addresses the urgent needs in electrical energy storage and provides a new paradigm towards high-energy-density polymer dielectrics over a broad temperature range.