Cathode Catalyst For High Performance Li-O-2 Batteries

Since the lithium-ion battery came out,it has been widely used in various 3C products.In 2019,the Nobel Prize in chemistry was awarded to three scientists who have made great contributions to the lithium-ion battery,which is enough to explain its impact on the world.However,in recent years,with the increasing shortage of fossil energy and the increasingly serious environmental pollution,the electric vehicle industry is booming.The short board of lithium-ion battery in this field is gradually emerging.A series of problems,such as insufficient energy storage and high cost,need to be solved.In terms of theoretical and practical application research and development,the development of lithium-ion battery has reached a bottleneck period.Therefore,the research and development of new batteries with better performance will become another breakthrough direction in the field of power batteries in the future.At present,researchers have begun to research and develop various new batteries,such as sodium ion batteries,lithium oxygen batteries,lithium sulfur batteries,zinc air batteries,etc.the key to the research and development of both low-cost sodium ion batteries and lithium oxygen batteries with high energy density is the research and development of electrode materials.Although the lithium-oxygen battery in the early stage of research has a high initial theoretical capacity,it shows poor stability,large overpotential and short cycle life in the process of battery charging and discharging.The R&D and design of positive catalyst is an important link to improve the performance of lithium-oxygen battery.Among the many two-way catalysts designed by the R&D personnel at present,the research of transition metal oxides and carbon materials Most widely.In order to reduce the overpotential and improve the cycle life and cycle stability of the lithium oxygen battery,several solutions are designed for the problems faced by the positive catalyst.The specific research contents are as follows:（1）The two-step hydrothermal method was used to synthesize 1,3,5-benzoic acid tricarboxylic acid manganese metal organic framework Mn-BTC MOF material as a precursor,explore the experimental conditions,and adjust the Mn ion concentration in the preparation method to obtain Mn-BTC with uniform size,control different calcination temperatures to get two crystallinity Mn₂O₃ and different crystal forms of Mn₃O₄.Through morphological observation,it is found that Mn₃O₄ formed by annealing at 900℃loses the channel structure,and Mn₂O₃ obtained at 450℃has Mn-The structure of BTC MOF,using Mn₂O₃ and Mn₃O₄ as positive electrode catalysts for lithium-oxygen batteries,assembling the batteries,and testing their cycle stability.In the battery test,Mn₂O₃ that retains the shape of Mn-BTC has better electrocatalytic performance and cycle stability At 200 m A g^-1 current density,the two cycles reached 50 cycles,at 1000 m A g^-1 current density,Mn₂O₃ cycled 100 cycles,Mn₃O₄ cycled 84 cycles,and the Mn₂O₃ overpotential was lower and the discharge platform was more stable.（2）On the basis of the preparation of Mn₂O₃ material with Mn-BTC MOF structure,the manganese trioxide nanocomposite（Ru O₂/Mn₂O₃）loaded with ruthenium oxide in two different ways is used for oxygen reduction and oxygen precipitation of lithium-oxygen batteries.The catalytic process explores the dual-function electrocatalytic performance of Ru O₂/Mn₂O₃.Complexes with different Ru O₂ content were obtained by in situ and ex situ methods.Approximately 2.7 wt%of the micron-level precious metal oxide Ru O₂ content is then deposited on the nanorod transition metal oxide Mn₂O₃（in-suit Ru O₂@Mn₂O₃）.Doping Ru O₂ in the in-suit method can reduce the precious metal content and provide more activity Site to reduce battery manufacturing costs.The composite product obtained by the ex-situ method has a higher content of precious metal oxides.The study found that several metal elements on the surface of the catalyst can help the discharge product deposit evenly and protect the active parts on the surface of the catalyst,thereby making the battery cycle performance more stable and cycle,longer life.When Mn-BTC is directly used as a Ru O₂ carrier,the obtained catalyst can improve the cycle stability of the battery,and allow the discharge product Li₂O₂ to be stably deposited and decomposed,and the increased active sites can improve the cycle stability(at high current density The life of the battery is 267 cycles:and the life of the battery is a long cycle at low current density(>1600h,330 cycles:but the content of Ru O₂ limits its deep discharge capacity,which prompted us to develop a new The research ideas are used to design Li-O₂ battery catalysts.This method can be selected according to actual needs.The pore structure carrier optimizes the catalytic effect of the catalyst.（3）Using citron peel sponge as a precursor,high-temperature pyrolysis method to prepare bio-carbon material as a catalyst,as a positive electrode catalyst for lithium-oxygen batteries,by comparing with Super-P,explore high-temperature pyrolysis bio-carbon material as air The effect of the electrode on the lithium-oxygen battery,based on the hydrothermal reaction and annealing to obtain C-Urea,by immersing the carbon material in the polymer polyaniline PANI,annealing under the same conditions to form N-doped C-PANI,contrast doping The electrochemical performance of N’s biomass carbon material as a positive electrode material for lithium-oxygen batteries.The biomass-derived carbon material has a large specific surface area（327.64m²/g）,the surface is wrinkled,the edges can be seen as a layer,and there are many microporous structures below 5nm.These micropores make this material very Strong adsorption capacity,the N element dorping in C-PANI exists in the form of heteroatoms,and there are functional groups in C-Urea,which are not completely heteroatoms.These dopings cause the carbon material sp² hybrid orbit to change and form more defects improve the electrocatalytic performance of the battery.In the cycle stability test,the C-PANI material circulated 181 cycles at a high current density and 342 cycles at a low current density,and the overpotential was also lower than the other three materials with excellent difunction electrocatalytic performance and stability.