Achieving ultra-high discharge energy density of dielectric polymer nanocomposites by in situ synthesis

Polymer dielectrics are promising dielectric materials for high-energy-density dielectric capacitors owing to their facile processability and high breakdown strength. Currently, the primary method used to prepare nanocomposites involves the combination of polymers and nanoparticles and utilises the high insulation abilities of nanoparticles to limit the migration of carriers to obtain a high breakdown strength and charge–discharge efficiency. However, the dispersion of nanofillers in nanocomposites prepared using traditional methods is unsatisfactory, which not only leads to unsatisfactory energy-storage performance but also limits their applications owing to inconsistent batch-to-batch performance. Herein, nanocomposites with high energy densities are prepared through the in situ synthesis of nanoparticles in polymer solutions. Owing to the uniform dispersion and excellent insulation performance of the nanoparticles, the nanocomposites demonstrated a discharge energy density of 26.5 J/cm3 with a charge–discharge efficiency of 68% at the optimal composition. Additionally, amorphous nanoparticles have a higher energy barrier than crystalline nanoparticles, which can inhibit the carrier transport more effectively to obtain a lower leakage current. Compared with traditional preparation approaches, the as-proposed method for preparing nanocomposites is simple, and the resulting materials exhibit high performance, which is critical for the application of nanocomposites in capacitors.