Durability of advanced low temperature lithium compound electrode ceramic fuel cell for transportation

Abstract

In recent years, a ceramic fuel cell with lithium compound such as Ni_0·8Co_0·15Al_0·05LiO₂ (NCAL) as its electrode is reduced in H₂ to produce lithium compounds containing molten salt and diffused into oxide electrolyte to form an “oxide-lithium compounds molten salt” composite electrolyte with ultra-high ionic conductivity, which made the cell have remarkable low-temperature power generation performance. It is found that the dynamic migration of lithium compounds produced by NCAL anode in the cell with Ce_0.9Gd_0.1O_2-δ (GDC) as electrolyte during the constant current durability test is the main reason for the cell performance degradation. In this paper, we found that adding different mass ratios of NaFeO₂ to the GDC electrolyte to construct GDC/NaFeO₂ composite electrolyte can significantly affect the durability of the cell. Under the constant current density test conditions of 550 °C, 0.2 A cm⁻², the performance of the cell with GDC/NaFeO₂ composite with a mass ratios of 8/2 as electrolyte maintained relatively good durability in the constant current test of 50 h. The characterization results show that the NaFeO₂ reacts with lithium compounds such as LiOH to generate LiFeO₂ and NaOH, and NaFeO₂ is reduced to Fe and NaOH by H₂. A proper amount of NaFeO₂ in the GDC/NaFeO₂ composite electrolyte can produce sodium compound molten salt during the performance test to replace the role of lithium compound molten salt in improving the electrolyte ionic conductivity and the cell sealing, while slowing down the dynamic migration of the molten salt in the cell, thus improving the durability of the cell. The findings in this paper provide evidence and relevant theories for the performance degradation and durability improvement mechanism of this new type of lithium compound electrode ceramic fuel cell (LCCFCs), and propose new strategies for obtaining LCCFCs with better durability.