LiNi0.5Mn1.5O4 (LNM) spinel is a commercial positive electrode material for lithium batteries. This material is attractive as oxygen vacancies are formed in this spinel material, which is an essential requirement for SOFC materials. We found that the LNM spinel showed rapid oxygen release and uptake rates and that a large amount of oxygen vacancies was formed Thus, here we attempt to utilize this spinel as a cathode material for SOFC.
All the cathode material requirements have been investigated. The spinel showed excellent chemical stability from 1000 to 1400 oC in air, while it underwent reduction in H2 at 800 oC. No interaction between LNM and yttria-stabilized zirconia (YSZ) electrolyte was observed by XRD and EDS characterizations. The total conductivity of LNM was about 0.2-5 S cm-1 at the temperature of 400-800 oC by 4-probe DC test. The LNM was spin-coated on both sides of an YSZ electrolyte support to form a symmetry cell for electrochemical performance investigation with gold paste as current collector. The resistance of the LNM cathode was 0.77 Ω cm2 at 800 oC according to impedance spectroscopy measurements (EIS), better than traditional La1-xSrxMnO3 perovskite cathode material. A long term study of cathode impedance was also conducted. It indicated that the cathode material can uptake oxygen from the atmosphere gradually at temperatures lower than 700 oC, leading to a decrease of the oxygen vacancy amount and an increase of cathode resistance with time.
Further studies are focusing on investigating the oxygen exchange property of LNM spinel from electrochemical aspects, in order to get a better understanding of the nature between the oxygen vacancy and the electrochemical properties of material.
See more of this Group/Topical: Transport and Energy Processes