Enhanced breakdown strength and energy storage density in polyurea all-organic composite films

Abstract

Polymer dielectric materials are highly desirable in electronic devices. However, neither low nor high dielectric constant polymers could meet the requirement of high energy storage application due to the contradiction between dielectric constant and breakdown strength. Herein, in order to obtain high performance polymer dielectrics, poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) is filled, as a functional material, into polyurea (PUA) matrix to form all-organic composites. Fortunately, PUA/P(VDF-TrFE-CFE) composites exhibit excellent performance with high dielectric constant and maintain high breakdown strength, resulting in enhanced energy storage density. The breakdown strength of composite film increases to 5130 kV cm−1, and the energy storage density can reach 4.3 J cm−3, which is much higher than pure PUA (2.4 J cm−3) and commercially biaxially oriented polypropylene (BOPP, 1.2 J cm−3). The enhancement of energy density of composite films is mainly attributed to the dipole interaction between PUA and P(VDF-TrFE-CFE) chains, which leads to increases of dielectric constant and maintain high breakdown strength simultaneously. This work provides an effective route to improve the energy density of linear dielectrics and showing great application potential for energy storage.