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/cm 3 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.