Lamellar Aromatic Polyimine with Strong Self-Trapped Excitons for Efficient Capacitive Energy Storage

Solid film capacitors play a crucial role in the modern electrical and electronic industry, with organic polymer materials dominating the market owing to their cost-effectiveness and exceptional processability. However, the low dielectric constants of current polymers gradually fail to meet the increasing demands for high energy density of capacitors. Improving the energy storage capacity of polymer films is imperative yet very challenging. This work synthesizes an aromatic polyimine (API) with high crystallinity and unique electronic structures, which experimentally demonstrate outstanding charge storage capacity. The simple synthesis procedures of APIs allow for large-scale production at a low cost. The obtained API exhibits a typical layered crystal structure, which can be further exfoliated into quasi-two-dimensional lamellar nanoflakes via direct sonication. Notably, API undergoes a self-trapped transition band state due to the strong electron-phonon coupling at room temperature, imparting reliable charge capture ability under high electric field strength. As a result, incorporating a small amount of lamellar API into biaxially oriented polypropylene film can significantly enhance their energy storage density. This work introduces a novel crystalline polymer with exceptional charge capture and storage capabilities, providing a new avenue for the development of next-generation polymer film capacitors.