Preparation And Performance Investigation Of Transition-metal Oxides As Cathode Catalysts For Non-aqueous Li-air Batteries

Energy source is the material foundation of human society relies for survival anddevelopment. As energy demand is increasing sharply across the world, the rapid depletionof fossil fuels, environmental pollution and other issues severely restrict the “sustainable”development of human civilization. As a result, creating a new energy-material systemwhich can efficiently reduce pollution becomes a hot scientific research field, in order tosettle the issues of energy crisis. In recent years, rechargeable Li-air battery as a newbattery system has attracted considerable attention because of their theoretical high energydensity. Moreover, the catalytic activity plays a vital role in non-aqueous Li-air battery.Compared with other catalytic materials, the transition-metal oxides have attractedextensive attention as alternative catalysts in Li-air battery due to salient advantages of lowcost, high catalytic activity, and environmental friendliness. In this thesis, two types oftransition-metal oxides are synthesized and used as the electrocatalyst for exploring theirelectrochemical properties, the results are as follow:Multiporous MnCo2O4microspheres are prepared by the solvothermal methodfollowed by pyrolysis of carbonate precursor. The multiporous MnCo2O4mirospheresshow good electrocatalytic activity toward ORR/OER in alkaline solution and non-aqueouselectrolyte, because the porous structure of MnCo2O4mirospheres which we fabricatedprovides high electrocatalytic active sites. Employing the multiporous MnCo2O4mirospheres as catalysts in Li-air batteries, the cells display splendid electrochemicalproperty, lower overpotential, E=1.2V and excellent discharge capacity. At the currentdensity of100mA g-1, the discharge capacity of Li-air cell with MnCo2O4mirospheres isup to5956.3mAh g-1, which is much larger than that of Super P. what is more, the cellexhibits prominent capacity reversibility over50cycles in pure O2atmosphere.Perovskite-like transition-metal oxides La1.6Sr0.4NiO4and La1.6Sr0.4Ni0.6Cu0.4O4whichare used as cathode materials in non-aqueous Li-air batteries are fabricated byglycine-nitrate process (GNP). The experimental results manifest that the Cu-dopedLa1.6Sr0.4Ni0.6Cu0.4O4has a uniform particles size distribution and exhibits betterelectrocatalytic activity than La1.6Sr0.4NiO4. The initial discharge capacity of Li-air cellwith La1.6Sr0.4Ni0.6Cu0.4O4is up to5559.4mAh g-1,which is higher than that ofLa1.6Sr0.4NiO4(4602.4mAh g-1), and the charging platform is3.8V, at the current densityof0.1mA cm-1. The cell shows smaller polarization compared with La1.6Sr0.4NiO4-basedLi-air cell. In addition, cell with La1.6Sr0.4Ni0.6Cu0.4O4as catalysts processes better rateperformance and higher cycling stability than that of La1.6Sr0.4NiO4.