Enhancement of energy storage for electrostatic supercapacitors through built-in electric field engineering

In this study, a novel yet general strategy is proposed and demonstrated to enhance the energy storage density (ESD) of dielectric capacitors by introducing a built-in electric field in the dielectric layer, which increases the applied electric field required to polarize the dielectric. By using the top and bottom electrodes of different work functions, a built-in electric field is created in the antiferroelectric layer, which leads to an increase in the critical fields for the antiferroelectric-ferroelectric phase transition and thus the enhancement of ESD. Accordingly, the TiO2/ZrO2/TiO2 antiferroelectric capacitor with asymmetric electrodes demonstrates an ultra-high ESD of 114.5 J cm−3, which is improved by ~21% compared to the antiferroelectric capacitor without a built-in field, along with high efficiency of 76%. The achieved ESD is record-high among the HfO2/ZrO2-based lead-free antiferroelectric thin-film capacitors. The result indicates that engineering the built-in electric field can be an effective and promising approach to increasing the ESD for electrostatic supercapacitors.