Incorporation of elaborately Synthesized BNNSs by a mild mechanical stirring process for the concurrent enhancement of thermal conductivity and dielectric breakdown strength of PVDF

Abstract

Due to the growing energy demands, it is highly desirable to concurrently improve the thermal conductivity and dielectric breakdown strength of dielectric film capacitors. Polyvinylidene fluoride (PVDF) is hitherto regarded as a most satisfactory alternative for dielectric capacitors but with relatively low thermal conductivity and dielectric breakdown strength. Herein, a major contribution is made to the concurrent enhancement of PVDF-based thermal conductivity and dielectric properties. It can be readily achieved through the incorporation of as-prepared high-quality few-layered boron nitride nanosheets (BNNSs) with a minimized loading (defined as PVDF-BNNSs). BNNSs dispersion with intact structure and a large aspect ratio is prepared by a unique mild mechanical stirring process assisted by dimethyformamide/1-butanol (DMF/1-butanol) solvent and a low power ultrasonic. Encouragingly, the characteristic breakdown strength with a maximum value of 334 MV/m reaches for PVDF-BNNSs composite only with 3 vol% BNNS loading, to be 1.6 times of pure PVDF. It also presents a high discharged energy density up to 9.9 J cm-3, along with an efficiency of 68.3%. Synchronously, the thermal conductivity accomplishes a high value of 1.12 W/m·K with only 8 vol% BNNS loading. A further theoretical analysis reveals that high-quality appropriate BNNSs loading could be preferentially arranged in parallel with PVDF surface. It indicates that BNNSs have good interface compatibility with PVDF, thus to improve its associated performances concurrently.