Solution-processed ferroelectric terpolymer nanocomposites with high breakdown strength and energy density utilizing boron nitride nanosheets

The development of high-performance capacitive energy storage devices is of critical importance to address an ever-increasing electricity need. The energy density of a film capacitor is determined by the dielectric constant and breakdown strength of dielectric materials. With the highest dielectric constant among the known polymers, poly(vinylidene fluoride)-based ferroelectric terpolymers are of great potential for high energy density capacitors. However, their energy storage capability has long been limited by the relatively low breakdown strength. Here we demonstrate remarkable improvements in the energy density and charge-discharge efficiency of the ferroelectric terpolymers upon the incorporation of ultra-thin boron nitride nanosheets (BNNSs). It is found that BNNSs function as a robust scaffold to hamper the onset of electromechanical failure and simultaneously as an efficient insulating barrier against electrical conduction in the resulting polymer nanocomposites, resulting in greatly enhanced breakdown strength. Of particular note is the improved thermal conductivity of the terpolymer with the introduction of BNNSs; this is anticipated to benefit the stability and lifetime of polymer capacitors. This work establishes a facile, yet efficient approach to solution-processable dielectric materials with performance comparable or even superior to those achieved in the traditionally melt-extruded ultra-thin films.