Ultrahigh Energy Density in Continuously Gradient-Structured All-Organic Dielectric Polymer Films

High-performance dielectric capacitors are critical for advanced electronics and electrical power systems. Polymeric dielectrics have been widely investigated for using in dielectric capacitors because of their high dielectric constants, flexibility, low density, and easy processability. However, it is still challenging to achieve simultaneous improvements in both energy density and efficiency in these dielectric polymers. Here, we report ferroelectric polyvinylidene-fluoride-based all-organic dielectric polymer films with continuous compositional gradient structure are reported by modulating the spatial distribution of polymethyl-methacrylate components, prepared via a facile and scalable additive manufacturing method. The continuous out-of-plane composition gradient in the all-organic dielectric polymer films allows to tune electrical and mechanical behaviors, and thus induces a notably enhanced breakdown strength by modulating the electromechanical breakdown process related to the coupling of local electric field and stress. An ultrahigh discharge energy density of 38.8 J cm−3 along with a high discharge efficiency of >80% is achieved at the electric field of 800 kV mm−1 in the gradient polymer films, which is the highest energy density reported thus far in polymer-based dielectrics including their nanocomposites and the highest energy efficiency achieved along with an energy density of >30 J cm−3.