Research And Application Of The Perovskite As Catalyst On Lithium Air Batteries

In this work,La0.4Sr0.6CoxMn1-xO3(x=0,0.2,0.4)?La0.4Sr0.6NixMn1-xO3(x=0,0.2,0.4)and Ag-La0.4Sr0.6MnO3 were synthesized via a sol-gel route.The crystalline structure,morphology,specific surface area and surface composition for each as-prepared material were characterized by XRD,SEM,TEM,BET and XPS techniques.The intrinsic catalytic properties of these materials toward the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)were studied in 0.1 M alkaline potassium hydroxide solution using the rotating disk electrode technique.All samples were used as bifunctional catalysts for oxygen cathode in rechargeable lithium-air batteries.The results of XPS indicated that the obtained La0.4Sr0.6CoxMn1-xO3(x=0.2,0.4)contained more oxygen vacancies and Mn4+/Mn3+ and Co3+/Co2+than La0.4Sr0.6MnO3 on the oxides surface.The ORR and OER polarization curves revealed that the bifunctional catalytic performances were improved in the order of Vulcan-XC 72.La0.4Sr0.6MnO3?La0.4Sr0.6Co0.2Mn0.8O3 and La0.4Sr0.6Co0.4Mn0.6O3.Further,the electrochemical catalytic performances of La0.4Sr0.6CoxMn1-xO3(x=0,0.2,0.4)were investigated in oxygen cathodes for rechargeable Li-air batteries.At a current density of 100 mA g-1,the discharge capacity of the oxygen cathode with the La0.4Sr0.6CoxMn1-xO3(x=0,0.2,0.4)catalyst were 5818.8 mAh g-1,6419.9 mAh g-1)7226.9 mAh g-1,respectively.Tested at 500 mA g-1 with a limited discharge depth of 1000 mA h g-1,the cathode with the La0.4Sr0.6Co0.4Mn0.6O3 catalysts showed a longer lifespan(46 cycles)than that of the cathode with the La0.4Sr0.6MnO3 catalyst(24 cycles).The surface compositional characterization results showed that the obtained La0.4Sr0.6NixMn1-xO3(x=0,0.2,0.4)contained more oxygen vacancies than the La0.4Sr0.6MnO3,as well as a certain amount of Ni3+(eg = 1)on the oxides surface.The half-cell test results showed that the Ni-doped La0.4Sr0.6NixMn1-xO3(x=0,0.2,0.4)was provided with higher bifunctional catalytic activity than the La0.4Sr0.6MnO3.In particular,the La0.4Sr0.6Ni0.2Mn0.8O3 had a lower total overpotential(1.06 V)between the oxygen evolution reaction(@ i = 5 mA cm-2)and the oxygen reduction reaction(@i =-1 mA cm-2)than that of the La0.4Sr0.6MnO3(1.249 V).Further,the electrochemical catalytic performances of La0.4Sr0.6NixMn1-xO3(x=0,0.2,0.4)were investigated in oxygen cathodes for rechargeable Li-air batteries.At a current density of 100 mA g-1,the discharge capacity of the oxygen cathode with the La0.4Sr0.6NixMn1-xO3(x=0,0.2,0.4)catalyst were 5818.8 mA h g-1,6238.6 mA h g-1,7303.7 mA h g-1,respectively.Tested at 500 mA g-1 with a limited discharge depth of 1000 mA h g-1,the cathode with the La0.4Sr0.6Co0.4Mn0.6O3 catalyst showed a longer lifespan(37 cycles)than that of the cathode with the La0.4Sr0.6MnO3 catalyst(24 cycles).As a result,the Ni-doped La0.8Sr0.2Mn0.6Ni0.4O3 cathode showed superiority to the La0.8Sr0.2MnO3 as an oxygen cathode catalyst for Li-air battery.The elemental Ag and the perovskite oxide La0.4Sr0.6MnO3 were compounded by the static method and the perovskite complex with the best catalytic performance was explored by changing the amount of elemental Ag.The intrinsic catalytic properties of these materials toward the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)were studied in 0.1 M alkaline potassium hydroxide solution using the rotating disk electrode technique.The bifunctional catalytic activity of the perovskite material increases with the increase of the Ag content and the ORR electron transfer number of 10wt%Ag-LSM is closed to the theoretical value of the four-electron reaction.Combined with XPS analysis,the catalytic performance of perovskite material was theoretically analyzed.The adsorption of oxygen and Mn4+/Mn3+ redox electron on the surface of 10wt%Ag-LSM increased the ORR catalytic activity.The electrochemical performance of La0.4Sr0.6MnO3,10wt%Ag-LSM and 20wt%Ag-LSM was investigated by the new Granville test system by assembling 2032-type coin cell.When the current density was 100 mA g-1,the initial discharge capacity of 10wt%Ag-LSM reached 6827 mA h g-1,which was significantly higher than that of 20wt%Ag-LSM and La0.4Sr0.6MnO3.When the current density is 500 mA g-1 and the charge-discharge depth is 1000 mA h g-1,the cathode with the 10wt%Ag-LSM catalyst showed a longer lifespan(39 cycles)than that of the cathode with the La0.4Sr0.6MnO3 catalyst(24 cycles).It can be seen Ag composite can improve the catalytic performance of perovskite oxide and improve its cycle life.