Fig. 1: Interfacial design in composite capacitor film fabrication.

a Schematic illustration detailing the LM mechanochemistry process: Extensive milling promotes LM oxidation and BN activation, facilitating coordination between δ- N atoms’ pair electrons and δ+ metal atoms’ vacant orbitals. b TEM image and corresponding EDS image of LM-BN, illustrating LM coating on BN. c XPS N 1 s spectra comparison between BN and LM-BN. d Simulated 3D electrostatic potential distribution for both BN and LM-BN, indicating LM-BN’s enhanced potential difference, which promotes dipole polarization and confines electrons through electro-positivity. e Schematic illustration demonstrating composite film’s interface stress relief through LM interface mechanochemistry, preventing interfacial cracks during the meta-stable biaxial-orientation process, in contrast to conventional rigid filler composites. f–g Display of a large volume of LM-BN powder and PP/LM-BN composite pellets, suggesting scalability potential. h Cross-sectional SEM image showcasing a thin-film achievement of 3.4 µm thickness. i Image of a large-scale BOPP composite film measuring 65 × 50 cm, demonstrating the capability for synthesizing substantial film sizes. For illustrations in these figures, the volume ratio of the LM:BN is 30:70 in LM-BN, and the LM-BN content in the composites is 2.5 vol%.