The scalable and high performance polyimide dielectrics containing alicyclic structures for high-temperature capacitive energy storage

•Polyimide with an alicyclic structure was prepared for capacitor energy storage.•High bandgap width and weak charge transfer complex improve energy storage property.•Conductive and breakdown mechanism were investigated at high temperature.•Discharge energy density of 4.63 J cm−3 was obtained at room temperature.•0.78 J cm−3 and efficiency of 95% at 150 °C and 200 MV m−1 were achieved.