Closed‐Loop Recyclable and Thermal‐Conductive Fluoropolyimide Composites for High‐Temperature Capacitors

ABSTRACT The extensively developed high‐temperature energy storage (HTES) encounters rising sustainable issues caused by polymer dielectrics. Due to the harsh service conditions, including high temperature and voltage, daunting challenges remain in the design of polymer dielectrics that can break through the trade‐offs among recyclability, heat‐resistance, thermal‐conductivity, and electrical performances, which are pivotal for HTES. Herein, a polymer dielectric architecture is introduced that integrates an imine‐linked fluorinated polyimide (IM‐FPI) network with covalent triazine‐based nanosheets (CNNSs). Dynamic imine bonding between the fluorinated imide segments and CNNS fillers enables composite films that simultaneously address the conventional trade‐offs limiting polymer dielectrics. The thermal conductivity of the composite films reaches 3.95 W m −1 K −1 , while capacitors enabled by CNNS/IM‐FPIs show exceptional energy density ( U d = 4.98 J cm −3 at 200°C, η = 90%) and durability ( η > 90% after 1 × 10 5 charging‐discharging cycles at 200°C). CNNS/IM‐FPIs can be fully decomposed into monomers and fillers for closed‐loop recycling, and the recovered CNNS/IM‐FPIs can maintain the intrinsic performances. This study provides a promising approach to eco‐friendly high‐temperature polymer dielectrics.