Thickness effect of Yttria-Stabilized Zirconia as the electrolyte in all-solid-state thin-film supercapacitor with a wide operating temperature range

Materials manufacturing technologies have helped meet new electronic challenges, such as miniaturization and high performance under extreme operating conditions. This work introduces a thin-film supercapacitor with a wide range of operating temperatures based on symmetric Ru electrodes fabricated by sputtering and YttriaStabilized Zirconia (YSZ) electrolyte by Atomic Layer Deposition (ALD). YSZ thicknesses of 45, 70, and 90 nm were evaluated, and the total thickness of the device was less than 200 nm. Operating at 1.8 V, it was found that by increasing the temperature from 50 to 200 degrees C, the energy density improved for all thicknesses. The 45 nm YSZ showed the highest values, 0.129 mWh/cm3 at 50 degrees C and 60.4 mWh/cm3 at 200 degrees C. The improvement was related to activating ionic conduction in YSZ, which increased the dielectric constant from 58 to 209. We discuss the energy storage mechanism with galvanostatic charge-discharge, chronoamperometry, cyclic voltammetry, and impedance spectroscopy. Material characterization suggests that decreasing thickness positively affects energy storage due to residual compressive stress. Our results are relevant for the application as in-chip energy storage deposited directly in integrated circuitry, especially in harsh operating conditions. This research opens up the possibility of moving from wearable micro-thick devices to nano-thick devices.