Enhanced energy density in cellulose doped polyimide-based all organic composites for high temperature capacitor applications

The growing demand for electronic devices has induced a significant requirement for high energy density capacitors. In this investigation, we introduced small groups of cyanoethyl cellulose (CEC) into a polyimide (PI) substrate to create all organic CEC/PI composite films for high energy density capacitor applications. Due to the large dipole moment in C-CN dipoles in CEC groups, the dielectric constant of the CEC/PI-5 (5% CEC) composite increased by 26.3% to 4.31. Compared to the pristine PI film at room temperature, the breakdown field of the CEC/PI-0.5 increased by 4.7% from 502.29 to 526.1 MV m-1 and the energy storage density increased by 95% to 11.70 J cm-3. Furthermore, the CEC/PI-0.5 film exhibited an energy density of 6.39 J cm-3 with the breakdown field of 400 MV m-1 at 150 degrees C, which is 93.05% higher in energy densities than that of the pristine PI film. Furthermore, simulation results indicate that CEC groups can introduce deep traps in the CEC/PI composite, which can inhibit charge movement in the composite and increase the breakdown field of it. In this study, it was found that by adding small amount of CEC polar group in PI film, the high temperature energy density of CEC/PI composite materials was significantly improved. This study not only makes a significant contribution to the development of high-temperature energy-density capacitors, but also pave a way by using small molecule polar polymers to improve the energy density of dielectric materials at high temperature.