Polymer Dots Enabling Ultrahigh Capacitive Energy Storage in Cellulose-based All-Organic Nanocomposites

Abstract

Dielectric capacitors represent a promising alternative to conventional electrochemical counterparts for applications in high-voltage networks, integrated circuits, and portable flexible electronics. Currently, most practical dielectric polymers are derived from petroleum-based sources, whereas environmentally sustainable biomass dielectric materials remain largely underexplored. We report a class of cyanoethyl cellulose (CEC)-based nanocomposites enhanced with polyethyleneiminebased polymer dots (PEPDs), which simultaneously elevate both the dielectric constant (ε r ) and breakdown strength (E b ). The wide-band-gap PEPDs with abundant amino groups form hydrogen bonds with the CEC backbone, ensuring uniform dispersion and creating continuous polar interfacial regions that substantially improve ε r . In parallel, the high electron affinity of the polymer matrix, together with deep-level traps introduced by the wide-band-gap PEPDs, effectively suppresses charge migration and reduces conductive loss, leading to a notable enhancement in E b . As a results, the optimized composite achieves a remarkable discharged energy density (U d ) of 35.2 J/cm 3 at 700 MV/m, outperforming current dielectric biomass materials. This work establishes a promising pathway for the development of cellulose-based nanocomposites toward next-generation high-energy-density dielectric capacitors.