Scalable Polyimide‐Poly(Amic Acid) Copolymer Based Nanocomposites for High‐Temperature Capacitive Energy Storage

The developments of next-generation electric power systems and electronics demand for high temperature (≈150 °C), high energy density, high efficiency, scalable, and low-cost polymer-based dielectric capacitors are still scarce. Here, the nanocomposites based on polyimide-poly(amic acid) copolymers with a very low amount of boron nitride nanosheets are designed and synthesized. Under the actual working condition in hybrid electric vehicles of 200 MV m-1 and 150 °C, a high energy density of 1.38 J cm-3 with an efficiency higher than 96% is achieved. This is about 2.5 times higher than the room temperature energy density (≈0.39 J cm-3 under 200 MV m-1 ) of the commercially used biaxially oriented polypropylene, the benchmark of dielectric polymer. Especially, the energy density and efficiency at 150 °C show no sign of degradation after 20 000 cycles of charge-discharge test and 35 days' high-temperature endurance test. This research provides an effective and low-cost strategy to develop high-temperature polymer-based capacitors.