Research of Flexible BST / PMMA Nanocomposite Films on Dielectric Energy Storage Performance

ABSTRACT With the rapid development of green energy and wearable electronics, high‐performance energy storage devices were increasingly in demand for electronics. Polymer‐based nanocomposites, combining the high dielectric constant ( ε r ) of nanoparticle fillers and the high breakdown strength ( E b ) of polymers, are promising for next‐generation flexible dielectric capacitors. In this study, flexible nanocomposites were fabricated via spin‐coating using poly(methyl methacrylate) (PMMA) as the matrix and Ba 0.8 Sr 0.2 TiO 3 (BST82)/Ba 0.6 Sr 0.4 TiO 3 (BST64) nanopowders as fillers. The nanocomposites show a dense microstructure with uniform BST distribution. Systematic studies on microstructure, dielectric properties, E b , and energy storage performance were conducted for BST volume percentages of 0–20 vol%. ε r increased from 3.61 for pure PMMA to 6.77 for BST82/PMMA and 6.55 for BST64/PMMA, while E b decreased from 846 MV/m for pure PMMA to 176 MV/m for BST82/PMMA and 187 MV/m for BST64/PMMA with 20 vol% BST. The Jayasundere‐Smith model better fits the ε r variation than the Maxwell‐Wagner model, especially with a higher BST volume percentage. At 450 MV/m, 3 vol% BST82/PMMA achieved a discharge energy storage density ( U discharge ) of 4.57 J/cm 3 , which is 1.32 times that of pure PMMA. At 500 MV/m, 1 vol% BST64/PMMA exhibited a U discharge of 7.71 J/cm 3 , which is 1.50 times that of pure PMMA with an energy storage efficiency ( η ) of 74.12%. BST64/PMMA outperformed BST82/PMMA in E b and energy storage performance, attributed to the paraelectric phase of BST64. This work offers key insights into enhancing energy storage performance in flexible polymer composites via the spin‐coating method.