Abstract
Electrostatic capacitors attract great interest in energy storage fields due to their advantages of high power-density, fast charge/discharge speed, and great reliability. Intensive efforts have been placed on the development of high-energy-density of capacitors. Herein, a novel supercapacitor with Hf(0.2) Zr(0.8) O(2) /xAl(2) O(3) /Hf(0.2) Zr(0.8) O(2) (HAHx) is designed to improve the breakdown strength (E(b) ) through optimizing Al(2) O(3) (AO) film thickness. Low-temperature annealing is first proposed to enhance the polarization difference (P(m) -P(r) ) due to the formation of dispersed polar nanoregions, which is called "superparaelectric-like" similar to previous super-paraelectric behavior of perovskite structures. As results, both large E(b) and P(m) -P(r) values are obtained, leading to an ultrahigh energy storage density of 87.66 J cm(-3) with a high efficiency of 68.6%, as well as a reliable endurance of 10(7) cycles. This work provides a feasible pathway to improve both the polarization difference and breakdown strength of HfO(2) -based films by the combination of insulation insertion layer and low-temperature annealing. The proposed strategy can contribute to the realization of high-performance electrostatic supercapacitors with excellent microsystem compatibility.