| Lithium-oxygen battery is a kind of metal-air battery with metal lithium as the anode and oxygen in the air as the cathode reactant.Because of its high theoretical energy density and environmental protection,lithium-oxygen battery has attracted wide attention in recent years.In the research,it is found that there are still many problems that hinder the commercialization of lithium-oxygen batteries.Its positive electrode has some disadvantages,such as high charge-discharge potential,battery discharge products（Li2O2 or Li2O）piling up in the pore size of the positive electrode blocking the oxygen diffusion channel,etc.,resulting in poor cycle reversibility,low energy density,short cycle life and even termination of the charge-discharge process of the battery,which hinders practical applications.Therefore,it is of great significance for the practical application and development of lithium-oxygen batteries to find an effective cathode catalyst and optimize the electrochemical reaction kinetics process.In this paper,Because the reversibility of the battery is poor and the positive electrode is easy to be piled up by discharge products,a positive electrode catalyst suitable for lithium-oxygen batteries is designed to reduce the charge-discharge over-potential,increase the specific surface area of the positive electrode and prevent the accumulation of discharge products,in order to improve the battery performance and long-term operation stability.Firstly,Ni Al Mn ternary transition metal oxide material（NAM）was prepared by coprecipitation method as cathode catalyst for lithium-oxygen battery.The experimental results show that the electrochemical specific surface area of NAM can reach 83.25 m·g-1,which is the main reason for the improvement of the catalytic activity of the material.When the molar ratio of nickel,aluminum and manganese is 1:1:1.5,the deep discharge specific capacity can reach 5693.78 m A·g-1 at a current density of 0.1 m A·cm-2,and the discharge specific capacity is limited to 500 m Ah·g-1.19 charge-discharge cycles can be carried out stably.Secondly,silver composite manganese oxide materials(Ag@Mn O2-x)were prepared by one-step hydrothermal method,coprecipitation method and silver ion precipitation method,and heat treated at 220,450 and 800℃respectively,with the ratio of silver to manganese being 1:9.The analysis of the experimental results shows that the materials synthesized by silver ion precipitation method after heat treatment at 450℃are spherical formed by nanorod clusters.The structure has a large specific surface area,which can provide a place for lithium-ion reaction and a growth space for discharge products,and is conducive to improving catalytic activity.Under the condition of current density of 0.1,0.2,0.5 and 0.7 m A·cm-2,the deep discharge capacity can reach 6524.37,7364.62,6527.00 and 7315.38 m Ah·g-1,and the stable cycle is 26 cycles.Finally,silver composite Ni-Al-Mn ternary transition metal oxide material（Ag@NAM）was synthesized on the basis of previous experiments.Through physical characterization,it is found that silver affects the morphology of the material,while some silver is attached to the surface of the material,which plays a role in surface catalysis.The electrochemical performance test results showed that when the current density was 0.2m A·cm-2,the deep discharge capacity of the lithium-oxygen battery assembled by Ag@NAM with the ratio of 8.5:1.5 reached 6477.86 m Ah·g-1,which could be cycled for 28 cycles.The charge and discharge platform remained stable within 20 cycles. |
