PEALD YSZ-based bilayer electrolyte for thin film-solid oxide fuel cells

Abstract

Yttria-stabilized zirconia (YSZ) thin film electrolyte deposited by plasma enhanced atomic layer deposition (PEALD) was investigated. PEALD YSZ-based bi-layered thin film electrolyte was employed for thin film solid oxide fuel cells on nanoporous anodic aluminum oxide substrates, whose electrochemical performance was compared to the cell with sputtered YSZ-based electrolyte. The cell with PEALD YSZ electrolyte showed higher open circuit voltage (OCV) of 1.0 V and peak power density of 182 mW cm(-2) at 450 °C compared to the one with sputtered YSZ electrolyte(0.88 V(OCV), 70 mW cm(-2)(peak power density)). High OCV and high power density of the cell with PEALD YSZ-based electrolyte is due to the reduction in ohmic and activation losses as well as the gas and electrical current tightness.

A review on recent status and challenges of yttria stabilized zirconia modification to lowering the temperature of solid oxide fuel cells operation

“…48,49 One of the solutions to enhance the YSZ electrolyte conductivity for the SOFCs operating temperature at low-to-intermediate temperature is reducing the thickness of YSZ electrolyte from 100 μm to 10 μm providing the minimal ohmic resistance, which will make the diffusion of ion oxides or proton easier through the YSZ electrolyte.. 50,51 Besides, the strategy by using the bilayer electrolyte design based on YSZ electrolyte or introducing an alternative oxide ion conductor to YSZ electrolyte will also prepare an excellent conductivity property at low-to-intermediate temperature and reliable to operate the SOFCs system below than 800°C. 52,53 Hence, it will expand the potential of the application of SOFCs to be implemented in the portable application and transportation sector. The high conductivity of solid electrolyte will give benefits, like, to minimize cell impedance, minimize leakage currents, and control the mobility of ionic and electron charge carriers.…”

Review on process-microstructure-performance relationship in ALD-engineered SOFCs

“…For example, a mixture of conducting oxides, e.g., doped CeO 2 , as the electrolyte may be susceptible to a reduction of the electrolyte at the anode at elevated temperatures, leading to electronic conduction (shorting) through the electrolyte and a lowered OCV; this becomes even more dominant when the electrolyte becomes thinner [71]. In some cases, direct electrical path (i.e., pin-hole in electrolyte) between electrodes exist, and no OCV is observed [59,60,68,70]. Cathode polarization loss, is usually the main operational loss in LT-SOFCs because of the high activation energy associated with ORR.…”

“…However, the cell performance was very low (<1 mW cm −2 at 550°C) due to physical defects induced by the chemical etching process leading to chemical shorting through the electrolyte. ALD YSZ electrolytes on a nanoporous substrate ALD thin films have also been widely employed as dense electrolytes for nanoporous substrates (e.g., anodized aluminum-oxide (AAO))-based MEA designs [59][60][61][62][63][64][65][66][67][68][69][70][71]. In 2011, ALD Al 2 O 3 , which is not an ionic conductor, was used to fabricate gas-tight electrolytes by physically filling pinholes and voids.…”

“…In addition, the anode structure was stabilized [64]. Cha's group reported the use of an ALD YSZ layer at the anode to impede reduction of doped CeO 2 (GDC or YDC) at elevated temperature [60,61,70,71]. By adopting the ALD YSZ layer, the OCV increased from ∼0.3 V to >1.0 V. Hong et al reported anodized aluminum oxide (AAO)-based SOFCs with a 180 nm layer of YSZ electrolyte fabricated by ALD [62].…”

“…Recently, a similarly structured SOFC with PEALD YSZ was reported by Lee et al They fabricated a Ni anode instead of Pt, and achieved comparable OCV and maximum power density [63]. PEALD YSZ was also applied as a protective layer for less dense YSZ electrolyte fabricated otherwise (using sputtering); it did not have pinholes, and therefore perfectly blocked the gas permeation [70]. PEALD YSZ was also adopted for protecting sputtered GDC that was used as a cathodic interfacial electrolyte [71].…”