Synthesis And Electrochemical Performance Of Perovskite Type Catalyst For Lithium Oxygen Batteries

As a special kind of lithium air battery, it has the same reaction mechanisms asLi-O2, but they have different structures and work environment. The latest researchprogress on lithium-air batteries as well as air electrode was reviewed. The recentresearch progress about kinds of catalysts in lithium-air batteries were summarized,especially perovskite-type compound oxide. And some synthetic methods ofperovskite-type compound oxide were simply introduced. Through reviewof the literature and the laboratory conditions, perovskite-type compound oxide wassynthesized by sol-gel method as cathodematerials in Li-O2batteries.Firstly, the optimum synthesis conditions of LaNi0.8Co0.2O3by sol-gel methodand its electrochemical performance as cathodecatalysts in lithium-oxygen batterieswere studied.Using nitrate as raw material, the effect of the amount of citric acid andethylene glycol, pH, reaction temperature, calcination temperature and time on thestructure, morphology and electrochemical performance of LaNi0.8Co0.2O3werestudied in detail. Reactions at calcining process and calcination temperature werestudied by thermogravimetric analysis. The structure, morphology andelectrochemical performance of LaNi0.8Co0.2O3were also studied. When the moleratio of citric acid, ethylene glycol and metal ions is2:2:1, pH to8, water bath at90℃for5h, calcination at700℃for3h in air, the synthesized LaNi0.8Co0.2O3have excellent electrochemical performance. It has an initial discharge capacity of2152mAh g-1at100mA g-1and cut-off voltage of2V under Super P as carbonmaterials. Under limiting the discharge and charge time to4h, the voltage can keep atabove2V after30cycles at0.1C. When limiting the discharge and charge time to2h,the voltage can keep at above2V after25cycles at0.2C.Secondly, the preparation technology of gas diffusion electrode was analyzed.By comparing Super P, acetylene black and graphene, the electrochemicalperformance of graphene is best when LaNi0.8Co0.2O3were used as cathodecatalystsin lithium-oxygen batteries. Meanwhile the dose of catalysts and PVDF wasresearched. When the mole ratio of graphene, catalysts and PVDF is8:1:1, the initialdischarge capacity is2152mAh g-1at0.1C and cut-off voltage of2V.At last, using AgNO3as Ag material and ascorbic acid as a reductant,LaNi0.8Co0.2O3/Ag was synthesized. The morphology and electrochemicalperformance were studied. The results show that the sample become smaller, and degree of crystallinity have no effect after loading Ag. When the mole ratio ofgraphene, catalysts and PVDF is8:1:1, the initial discharge capacity is2854mAh g-1at0.1C and cut-off voltage of2V. The initial discharge capacity drastically reducesto910mAh g-1at0.4C. When limiting the discharge and charge time to4h, thevoltage can keep at above2V after60cycles at0.1C.