Superior Capacitive Energy Storage at High Temperature of All-Organic Aromatic Polymer via Enhancing Conjugate Angle between Benzene Rings

High-temperature polymer capacitors with superior energy storage density are considerable and desirable components in advanced power pulse, electrical, and energy conversion systems. However, due to the π-π conjugated benzene ring structure, carriers migrate through polyimide (PI) chains, reducing discharge energy density (U_e) and charge-discharge efficiency (η) at high temperature. Here, the ether (−O−) and isopropylidene (−C(CH₃)₂−) groups are purposefully introduced into the position between the benzene rings to increase the conjugate angle in PI chains, and spatial folded chains are designed to impede charge transport at high temperature. The experimental results show both surface charge dissipation rate and leakage current decrease at 150 °C when (−C(CH₃)₂−) groups increase, indicating that deep traps that hinder charge transport are introduced in the chains. Hence, the breakdown strength of the designed polymer (BAPP+BPADA) significantly increases, and its U_e and η reach 3.87 J/cm³ and 90% at 150 °C, 2.74-times the energy density of the pristine PI film. Simultaneously, the BAPP+BPADA film exhibits excellent discharge response and cycling charge-discharge stability, which have the potential to be applied in functional devices under extreme conditions. The work performs a superior energy storage all-organic film and offers a strategy that regulates the chains’ spatial topological structure for future aromatic polymers for high-temperature energy storage.