High‐Energy‐Density Waterborne Dielectrics from Polyelectrolyte‐Colloid Complexes

Abstract To meet the demands of miniaturization and integration of next‐generation power systems, a major challenge is to improve the energy density of used dielectric capacitors. Polymer nanocomposites are of great potential for high‐energy‐density capacitors. However, most of them are prepared via melt blending at high temperatures or solution processing in hazardous organic solvents, which are energy consuming and environmentally problematic. It has long remained economically and ecologically challenging to develop new dielectric materials. Here, a class of high‐energy‐density dielectrics made by electrostatically complexing polyvinylidene fluoride (PVDF) latex with oppositely charged chitosan in an aqueous phase is reported. At the charge neutralization point, the film of PVDF@Chitosan complexes demonstrates the highest breakdown strength (630 MV m⁻¹) and recoverable energy density (10.1 J cm⁻³), which are respectively 279% and 421% higher than the bare PVDF latex film, and far beyond most of the conventional solvent‐ or melt‐processed polymer films. The largely improved capacitive performances are ascribed to the significant minimization of losses at the critical charge neutralization point. The concept can be extended to a wide range of colloids, including polystyrene latex and aqueous bentonite suspension, highlighting the versatility of the proposed approach to develop environmentally friendly high‐performance capacitors.