Fabrication And Performances Investigation Of Pd/Fe₃O₄/C Air Electrode Catalyst For Lithium-air Battery

In the recent years, lithium-air battery has been paid full attention. With highspecific energy of up to3622Whkg^-1（provided that it takes organic electrolyte and O₂isdeoxidize into Li₂O₂at the negative electrode.） and environmental friendly features aswell as cheaper cost, lithium-air battery obviously has the potential of extensiveapplication and is expected to be new battery of the second generation. In this study, theelectrolyte mainly consists of LiPF₆/EC and DEC, while the synthesized catalystsmainly refers to graphite/Fe₃O₄catalyst, highly-dispersed Pd/C catalyst, highly-dispersed Pd/Fe₃O₄/C catalyst, Graphene catalyst, and Pt/rGO catalyst.The Fe₃O₄nanoparticles can be synthesized mainly by chemical coprecipitationmethod or hydro-thermal method, while highly-dispersed Pd/Fe₃O₄/C catalyst andPt/rGO catalyst by microwave ethylene glycol reduction method and graphene catalystby improved Hummers method.The nanoparticle diameter of Fe₃O₄synthesized by chemical coprecipitationmethod and hydro-thermal method is4.15nm and4.03nm respectively. Those Fe₃O₄nanoparticles synthesized by hydro-thermal method are found via SEM to be smallerand more evenly distributed. However, through charge and discharge test, it’s found thatwhile Fe₃O₄is integrated with graphite and used as compound catalyst, its charge anddischarge capacities do not have regular change as the quantity of Fe₃O₄increases ordecreases.The particle diameters of the highly-dispersed Pd/C catalyst and Pd/Fe₃O₄/Ccatalyst synthesizes by microwave ethylene glycol reduction method are3.992nm and4.062nm respectively. The battery using Pd/C catalyst has a first discharge plateau of2.2V with a specific discharge capacity of1500mAhg^-1and a first charge plateau of3.3V with a specific charge capacity of3250mAhg^-1, while the battery usingPd/Fe₃O₄/C catalyst has a first discharge plateau of2.8V with a specific dischargecapacity of3500mAhg^-1and a first charge plateau of4.1V with a specific chargecapacity of671mAhg^-1.Through observation via SEM and TEM, graphite catalyst synthesized by hummersmethod has clear laminated structures, while the Pt/rGO catalyst synthesized bymicrowave ethylene glycol reduction method, with a particle diameter of0.288nm, alsohas clear laminated structures and the Pt particles are successfully but unevenly distributed on the Graphene particles. The battery using Graphene has a first dischargeplateau of2.3V with a specific discharge capacity of2000mAh·g^-1, and a charge plateauof4.0V with a specific charge capacity of1340mAh·g^-1, while the battery using Pt/rGOcatalyst has a first discharge plateau of2.5V with a specific discharge capacity of8050mAh·g^-1. With a specific charge capacity of only40mAhg^-1, the Pt/rGO catalystbattery has no charge plateau.