Optimizing the conjugated structure of aromatic polyurea for high-temperature capacitive energy storage

Polymer dielectrics that can operate under simultaneous electric and thermal extremes are urgently needed in advanced electrical and electronic devices. However, the high thermal stability of polymers is typically endowed by the conjugated aromatic backbones, leading to enhanced conduction loss and poor energy storage density. Herein, we regulate the bridge linkages between adjacent benzene rings to simultaneously improve the thermal stability and optimize the conjugated structure of polyurea (PU), thereby achieving high-temperature energy storage performance. With the introduction of ether, methylene, and isopropyl structural units, the dihedral angles between adjacent benzene planes gradually increase, enabling PU to achieve excellent energy density (U_e) and charge-discharge efficiency (η) with suppressed leakage conduction and improved breakdown strength. The optimal PU with isopropyl moiety achieves an attractive U_e of 5.1 and 2.1 J/cm³ with η above 90% at 30 and 150 °C, respectively. This work provides a facile strategy to improve the energy storage performance of aromatic polymers by optimizing the interaction between adjacent conjugated benzene planes.