Ultra-high energy storage density and scale-up of antiferroelectric TiO2/ZrO2/TiO2stacks for supercapacitors

Antiferroelectric (AFE) HfO2/ZrO2-based thin films have recently emerged as a potential candidate for high-performance energy storage capacitors in miniaturized power electronics. However, the materials suffer from the issues of the trade-off between energy storage density (ESD) and efficiency, as well as the difficulty in scaling up of the film thickness. In this study, an AFE TiO2/ZrO2/TiO2stacked structure is proposed to overcome these difficulties. The compressive chemical pressure arising from the interdiffusion of TiO2/ZrO2layers leads to a reduction of the hysteresis and thus a high ESD and a low energy loss. Hence the TiO2/ZrO2/TiO2single-stacked AFE capacitor demonstrates a record-high ESD of 94 J cm?3and a high efficiency of 80%, along with a high maximum power density of 5 × 1010W kg?1. The degradation of the energy storage performance as the film thickness increases is alleviated by the TiO2/ZrO2/TiO2multi-stacked structure, which presents a high ESD of 80 J cm?3and efficiency of 82% with the thickness scaled up to 48 nm. This improvement is attributed to the enhancement of breakdown strength due to the barrier effect of interfaces on electrical treeing. Furthermore, the capacitors also exhibit an excellent endurance up to 1010operation cycles. With a combination of high ESD, high efficiency, high power density, and scalability, the TiO2/ZrO2/TiO2stacked structures show promising prospects for supercapacitor applications. ? The Royal Society of Chemistry 2021.