Preparation And Li-O₂Cathode Performances Of Hierarchically Porous Co3O₄Films

Li-air battery has captured worldwide attention in recent years for its very highspecific energy. However, its practical application is currently limited by severalfactors, such as poor power capability, poor cyclability and low efficiency caused byhigh overpotential. All of these are largely determined by interfacial reactions onoxygen electrocatalysts in the air electrodes. Hence positive electrode catalysts arecritical for the performance of Li-air battery. Many studies have revealed that porousstructure of positive catalyst has a great effect on its performance. In particular,hierarchical porous structure shows good cyclability.In this work, we use hierarchical porous cathode catalyst material Co₃O₄aspositive electrode of the Li-air battery. Cathode catalysts are prepared by situelectrochemical deposition, and obtained hierarchical porous structure Co₃O₄byvarying the calcination temperature to adjust the formation of pore size. Then weimprove its catalysis of charging process by spurting Pt nanoparticles on the surface ofCo₃O₄films. The battery’s performances were investigated by physical and chemicalproperties and electrochemical properties.（1） Hierarchical porous Co₃O₄were obtained at different calcination temperatures from250°C to400°C, the samples calcined at300°C exhibited the best dischargeperformances. The initial discharge capacity reached2462mAh/g at the current of0.2mA. In study of battery’s rate capability, as the current of charge/dischargeincreases, the battery’s charge/discharge capacity decreased significantly, due to thepolarization of the battery increases. The initial discharge capacity of Li-air batteryreached4120.8mAh/g,3392.6mAh/g,2462mAh/g and416.1mAh/g at the current of0.05mA,0.1mA,0.2mA and0.5mA respectively. In battery’s cyclability test, thedischarge capacity decreased to no more then1000mAh/g after the6thcycle. However,when limiting its capacity of charge/discharge to1000mAh/g, the Li-air battery’s cycleperformance is greatly improved reaching14cycles.（2） In order to enhance the catalysis of the battery’s charging process, we spurting Ptnanoparticles on catalyst’s surface. The average potential of charging processes was3.1V which was0.8V less that compared to the3.9V of the pristine porous Co₃O₄films.The initial discharge capacity of the battery reached940.4mAh/g at the current of0.1mA. The discharge capacity decreased to636.9mAh/g at the10thcycle. Thecapacity retention was67.7%. The Mesopores of hierarchical porous Co₃O₄films arepartly blocked by Pt nanoparticles, when spurting Pt nanoparticles on the surface ofCo₃O₄. Therefore the discharge capacities of the batteries decreased.