Screening of electrode materials and cell concepts for composite ceria + salt electrolytes

Abstract

Summary The optimization of the performance of electrodes (oxide‐based) for composite electrolytes (Ce0.9Gd0.1O1.95 + (Li0.52Na0.48)2CO3) is addressed in this work acting mostly on the electrode chemical nature (eg, LaCoO3, Li0.43NiO2, or LiNiO2), thickness (single and multiple screen‐printed layers), and cell layer concept (with/without barrier layers between electrode and electrolyte). The cell performance and stability were analyzed by electrochemical impedance spectroscopy, X‐ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. LaCoO3 electrodes deposited on the electrolyte using an intermediate barrier layer showed a promising area specific resistance of 0.22 Ω.cm2 at 600°C. This optimized cell processing route was adopted as reference to study the endurance performance of distinct electrode materials up to 100 hours in air, at 550°C, where lithiated NiO showed the best stability.

Electrode protective barrier layers for molten carbonate confinement

“…This promising result obtained with minimum processing optimization indicates the immense positive impact of the LN37 PBL with respect to situations where this layer was absent. In fact, in similar tests performed in the absence of an LN37 PBL, the ohmic resistance increased almost 100% in only 100 hours 30 …”

“…In fact, in similar tests performed in the absence of an LN37 PBL, the ohmic resistance increased almost 100% in only 100 hours. 30 Figure 9B shows two impedance spectra obtained after 2 hours and 200 hours. Data overlap is obvious with respect to the cell ohmic resistance.…”

“…Previous work showed the efficacy of protective barrier layers (PBLs) to enhance the stability of LC in molten carbonate–based cells 30 . These layers were introduced to try to constrain the molten phase and thereby prevent possible changes in chemical composition and microstructure of electrode materials due to interaction with the molten phase.…”

“…Unfortunately, CGO-based PBLs increased cell ohmic losses even if effective with respect to the confinement of the molten salt. 30 To circumvent this drawback, in this work, only electronic conductors based on NiO were tested as PBLs. Lithiation of NiO is known to increase the p-type conductivity due to the assumed replacement of Li for Ni in the NiO lattice.…”

“…Previous work showed the efficacy of protective barrier layers (PBLs) to enhance the stability of LC in molten carbonate-based cells. 30 These layers were introduced to try to constrain the molten phase and thereby prevent possible changes in chemical composition and microstructure of electrode materials due to interaction with the molten phase. In line with this perspective, the efficiency of a transition metal oxide protective layer for Nibased electrodes was previously demonstrated as well as the complex role of the electrode microstructure on the performance of MCFCs.…”