Synthesis And Investigation Of Novel Catalysts Of Oxygen Cathode For Li-O₂ Battery

The exploration of energy storage and transform devices with large energy density,long cycle life,and environmental compatibility is a very urgent need on the road of sustainable development of human society.At present,the development of widely used lithium-ion batteries has gradually approached the limit of theoretical energy density and manufacturing technology,and its low energy density has caused it to appear insufficient in applications such as large energy storage stations and electric vehicles.Nonaqueous lithium–oxygen?Li-O₂?batteries have attracted much attention around the world due to their ultra-high theoretical energy density(?3500 Wh kg^-1).However,the practical application of Li-O₂ batteries is still hindered by high over voltages,low energy efficiency and poor stability.As for gas cathode,slow and unstable ORR/OER?oxygen reduction/evolution reaction?process is one of the reasons for the above problems.Thus,designing and exploring new catalysts of the cathode will make great hence for the development of Li-O₂ batteries.In this paper,we focused on the design of a new type of air electrode catalyst,combines the morphology of the catalyst and the design of the electrode structure,hoping to effectively improve the performance of Li-O₂ batteries.The completed research results mainly include:?1?An integrated Co O-Co N composite cathode?Co O-Co N/PCP?with yucca-like morphology was prepared.We use hydrothermal-nitriding technology to prepare Co O-Co N/PCP with a three-dimensional open structure,a high surface area,and fully exposed active sites.The rich phase interface and relatively more oxygen vacancies produced by partial nitridation can effectively improve the ORR/OER catalytic activity and stability of the composite.The yucca morphology of the Co?OH?F precursor is perfectly inherited by the composite,which providing rich three-phase reaction interfaces and facilitates the diffusion of Li⁺and O₂.In the Li-O₂ battery test,the current density is 50 m A g^-1,and its discharge capacity can reach 5423 m Ah g^-1.With a limited capacity of 500 m Ah g^?1,the battery was cycled for200 cycles without apparent degradation at a rate of 100 m A g^-1,compared with 60 and 70cycles of PCP and Co₃O₄/CP cathodes.?2?A series of N-CNTs-coated transition metal alloy high-performance composite catalysts AB/N-CNTs?A,B=Co,Ni,Fe?were prepared.We use CVD method to prepare N-CNTs with uniform properties on the surface of the alloy.A series of tests have shown that highly graphitized CNTs improve the stability of the material and that the rich and highly dispersed active sites exhibit excellent catalytic activity.As a cathode catalyst for Li-O₂batteries,it is found that the Fe Co/N-CNTs catalyst with the highest intrinsic catalytic activity exhibits the best battery performance.With a current density of 100 m A g^?1,its discharge capacity is up to 12931 m Ah g^?1,and exhibit a low overpotential of 0.8 V.Under a cutoff capacity of 1000 m Ah g^?1,Fe Co/N-CNTs electrode can keep this capacity within 160 cycles,which is 1.5 and 2.0 times of Fe Ni/N-CNTs and Co Ni/N-CNTs,respectively.