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

Abstract

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/TiO₂ stacked structure is proposed to overcome these difficulties. The compressive chemical pressure arising from the interdiffusion of TiO₂/ZrO₂ layers leads to a reduction of the hysteresis and thus a high ESD and a low energy loss. Hence the TiO₂/ZrO₂/TiO₂ single-stacked AFE capacitor demonstrates a record-high ESD of 94 J cm⁻³ and a high efficiency of 80%, along with a high maximum power density of 5 × 10¹⁰ W kg⁻¹. The degradation of the energy storage performance as the film thickness increases is alleviated by the TiO₂/ZrO₂/TiO₂ multi-stacked structure, which presents a high ESD of 80 J cm⁻³ and 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 10¹⁰ operation cycles. With a combination of high ESD, high efficiency, high power density, and scalability, the TiO₂/ZrO₂/TiO₂ stacked structures show promising prospects for supercapacitor applications.