Utilizing the synergistic effect between the Schottky barrier and field redistribution to achieve high-density, low-consumption, cellulose-based flexible dielectric films for next-generation green energy storage capacitors

After decades of development, the study of flexible dielectric materials has changed the focus from BOPP/PVDF/PI-based systems to those that can be biodegraded, not only because of several bottlenecks in the former systems but also because of the pollution they cause on the earth. Though various strategies were used, the improvement in the energy storage performance was slow. Recently, hydrogen bond replacement has been utilized for achieving a high energy density in sandwich-structured cellulose-based films; however, the efficiency was relatively low due to an uneven electric field distribution. In this work, a similar technology of the dissolution-regeneration route was used, and the multilayer-structured cellulose-based films were obtained by changing the sequence of fillers embedding in each sublayer. The differences in mechanical properties between films was revealed due to the different particle sizes and the presence of a slip layer effect. As a result of the synergistic effect between the field redistribution and the decreasing Fermi level, a breakdown strength as high as 6.24 MV cm −1 was achieved with a super high energy density of 31.07 J cm −3 and an efficiency of 80.03%, and the computer simulation fitted very well with the experimental data. The electric field distribution also help to reduce the energy consumption, for such a high energy density was triggered by a lower voltage. In addition, the film showed good fatigue endurance at both room temperature and 150 °C, which is caused by the intrinsic strong adiabaticity of cellulose. This work offers a unique approach to deeply understanding the electric breakdown mechanism in dielectric polymers and indicates the feasibility of cellulose in replacing petroleum-based polymers in the dielectric field. Due to the synergistic effect of field redistribution and the Fermi level's moving, an ESD of 31.07 J cm −3 with η of 80.03% was obtained in the SZS, which is the best performance in cellulose-based dielectric capacitors to the authors' knowledge.