First-principles Study On Ionic Conductive Mechanism Of CoMn₂O₄ Spinel

Solid oxide fuel cells（SOFCs）are devices that can convert the chemical energy stored in the fuel into electrical energy,which can be connected by interconnects between single cells.At the current operating temperature of SOFCs,the most suitable material for manufacturing interconnects is ferritic stainless steel.The oxide film will form on the surface of ferritic stainless steel in the high temperature working environment,which will affect the conductivity of the battery.Therefore,it is convenient to prepare a layer of coating on the surface of the interconnect to isolate it from oxygen,prevent the formation of oxide film,and improve the comprehensive performance of SOFCs.Cobalt-manganese spinel is one of the most potential coating material for interconnects at present.However,the conductive mechanism is still unclear.Therefore,it is of great significance to explore the conductive mechanism of spinel coating on the surface of metallic interconnects to promote the application of the ferritic stainless steel in the solid oxide fuel cell.In this paper,we have systematically studied the atomic diffusion behavior in CoMn₂O₄spinel,and analyzed the conductive mechanism of CoMn₂O₄spinel on this basis.The diffusion process of point defects in CoMn₂O₄spinel crystal are simulated by using the first principle calculation method.Firstly,the defect models with three types of vacancies and five types of interstitial atoms are established and optimized respectively.Secondly,we calculated and analyzed the energy barriers of vacancy diffusion,interstitial atoms and cascade reaction respectively by using CI-NEB method,and then calculated the corresponding diffusion coefficients.Our results show that in the process of atomic diffusion of CoMn₂O₄spinel crystal,the mobility of O atomic defect is the highest,followed by that of Co atomic defect,and the mobility of Mn defect is the lowest.Therefore,it is possible to improve the conductivity of CoMn₂O₄spinel by increasing the concentration of O atomic defects.This paper systematically analyzed the point defect diffusion and atomic conductivity of the interconnect coating material CoMn₂O₄spinel crystal.The obtained activation energy and diffusion coefficient can provide theoretical support for relevant experiments and the practical application of metallic interconnects in SOFCs.