Cathode/electrolyte Interface And The Cell Performance Of A New Type Hollow Symmetrical Solid Oxide Fuel Cells

The interface between the electrode and the electrolyte is an important part for performance of solid oxide fuel cell(SOFC).The cathode/electrolyte interface is the place where the oxygen reduction reaction(ORR)occurs,which is very important for the performance and stability of the SOFC.Therefore,investigation of the effect of the cathode/electrolyte interface on performance of the cell and the access of the full densification of the cathode/electrolyte interlayer is helpful to improve the stability and the output performance.However,there are few reports about the effect of interfacial bonding strength on the electrical properties of the SOFC,and the full densification of the interlayer between the cathode and electrolyte is still a problem.In addition,the two major types of the existing SOFC-tubular and planar structure,has its own shortcomings.The current collection of the tubular SOFC is not uniform,and the stability of the planar SOFC is poor.In order to solve above problems,we have studied the quantitative correlation between the adhesion strength and the resistance of cathode/electrolyte interface.A new hollow symmetrical structure SOFC was proposed.Based on this structure,the preparation process of the fully dense interlayer between cathode/electrolyte,and the performance of the cell under different preparation process have been investigated.The results are shown as follows:(1)A quantitative correlation between the adhesion strength and the ohmic resistance of the interface between the electrolyte and the cathode was fitted.The trend shows that the ohmic area specific resistance decreases gradually with the increase of the adhesion strength at the interfaces and reaches a plateau at a certain value.It seems that the polarization resistance has the similar changing trends with that of the ohmic resistance.(2)A new type SOFC with hollow symmetrical structure has been proposed.The effect of different sintering processes on the densification of the interlayer was investigated by using the new type SOFC.The optimal process of preparation of the full densification interlayer is:Co-sintering the GDC interlayer with the anode and electrolyte at the maximum temperature of 1300 ? for 4 hours.The GDC surface and the cross section of cell prepared by co-sintering is of fully dense,and the GDC interlayer is well combined with the YSZ electrolyte.On the contrary,the GDC surface and the cross-section of the cell prepared by the step-sintering is not completely dense,and the combination of the interlayer and the electrolyte interface is not very well,there is a large crack at the interface.(3)The new type SOFCs were prepared by three kinds of processes.Among them,the cell prepared by co-sintering GDC interlayer and step by step sintering cathode has the best overall performance.The open circuit voltage(OCV)of the cell at 750 ? is 1.006 V,the maximum output power density(MOPD)is 0.172 W/cm2,the area specific resistance(ASR)is 4.33 ?cm2;The voltage of the cell decreased from 0.79 V to 0.72 V with a degradation rate of 6.9%/100 h.At 750 ?,after 100 h constant current discharge at a discharging current of 0.37 Acm-2,the OCV of the cell decreased to 0.994V and the MOPD of the cell reached 0.161 W/cm2.The new type of SOFC worked at the operating temperature for a long time,the coarsening of anode particles may be the main reason for the degradation of the performance for SOFC.