The Protection Of Lithium Metal Anode And Basic Research For High-performance Lithium Air Battery

With the global energy crisis and increasingly serious environmental problems,the vigorous development of renewable new energy sources?solar energy,wind energy,tidal energy,etc.?is imperative.However,these regions of renewable energy production and available time cannot be balanced,restricting their development.In recent years,energy storage devices with high energy density and long cycle life have gradually attracted widespread attention.In many energy storage systems,lithium air batteries based on organic electrolytes have attracted widespread attention because of their extremely high theoretical energy density.However,lithium air batteries still face many challenges.For example,a slow catalitic capacities usually cause serious problems such as low specific capacity,high overpotential and poor cycle stability.In addition,the discharge products of lithium-air batteries are not easy to dissolve and have poor conductivity,which can easily block the air-catalyzed positive electrode and make the battery inoperable.Therefore,designing a porous catalyst with high catalytic activity is extremely important for lithium-air batteries.In addition,the lithium anode will be continuously polarized and corroded during the cycling of battery,which is also a key factor limiting the electrochemical performance of lithium-air batteries.Therefore,this paper focuses on the preparation of high-efficiency air catalytic electrodes and the optimization of metal lithium anodes:we synthesize MOFs derivatives and further optimize them with precious metals to obtain high-efficiency air catalysts and apply them to lithium air batteries;furthermore,we designed a nitrogen-sulfur double-doped carbon paper current collector loaded with pencil traces to build a high-performance lithium anode through a simple pre-stored lithium strategy and apply it to lithium air batteries.The research results are as follows:?1?We synthesized a square box ZIF-67 precursor and obtained a nitrogen-replaced porous carbon square box?Co₄N/Co-NC?embedded with Co₄N/Co nanoparticles through continuous high-temperature pyrolysis,and in the Co4N/Co-NC and,The concentration of nanoparticles on the surface of the square box surface of Co₄N/Co is Ru-Co₄N/Co-NC.Co₄N/Co-NC porous carbon nanotubes effectively promote the diffusion of electrons/ions and air and inhibit the agglomeration of Co-based active sites.A large number of Co4N/Co nanoparticles and their surface-oriented N elements are uniformLy distributed in the NC.This effectively improves the ORR/OER catalytic performance of lithium-air batteries.Also,the Ru nanolayer can effectively reduce the lithium-air battery.The lithium air battery with Ru-Co4N/Co-NC as the air catalytic material has better electrochemical performance.?2?Benefiting from the unique advantages of MOFs derivatives in lithium air batteries,we made more detailed preparations and researches on lithium air batteries on the basis of work?1?.We have successfully synthesized Co/CoxN nanoparticles embedded into N-doped hollow carbon nanocubes grafted with carbon nanotubes?Co/CoxN-HP/NC-CNT?through the pyrolysis of Co/Zn-ZIFs,which is further modified with the uniform Ir coating to obtain Ir-coated Co/CoxN-HP/NC-CNT?Ir@Co/Co_xN-HP/NC-CNT?.Due to the existence of Co/Co_xN nanoparticles,CNTs,and carbon framework,Co/Co_xN-HP/NC-CNT not only exhibits excellent electronic conductivity,but also obviously promotes the ORR/OER kinetics of Lithium air batteries.In addition,the volatilization of Zn over the high-temperature calcination leads to the formation of plenty of pores and CNTs in Ir@Co/Cox N-HP/NC-CNT,which can promote the free transfer of O₂/electrolyte and provide suitable space to storage the discharge products.Moreover,the Ir-coating layer can further reduce the side reactions and promote the reversible reaction of Lithium air batteries at very low discharge/charge overpotentials.Herein,the Ir@Co/CoxN-HP/NC-CNT based Lithium-oxygen batteries show good performances such as high specific capacity,perfect rate performance and long cycle life.?3?In order to meet the challenges of lithium anodes in lithium-air batteries,we have optimized and improved the traditional metal lithium anodes.We firstly carbonized polypyrrole rooted carbon paper?CP?in the presence of thiourea to obtain the N,S co-doped carbon paper?NS-CP?,and then drew a graphite-based layer?GL?on the surface of NS-CP?GL/NS-CP?by pencil.The resulting GL/NS-CP further reacts with molten Li by a thermal infusion strategy to form Li based GL/NS-CP?Li-GL/NS-CP?electrode.Through theoretical calculations,we found that the N,S co-doped porous carbon-based skeleton not only shows the extremely superior stability towards both molten Li infusion and electrochemical processes,but also promotes the nucleation of Li.Moreover,GL effectively enhances the surface wettability to Li and produces strong driving force to quickly lift molten Li into GL/NS-CP.The GL/NS-CP can effectively reduce the actual interface current density to suppresses lithium dendrites,and also has a symmetrical battery containing Li-GL/NS-CP anode electrode.The electrode has little obvious lithium dendrite growth and volume change after cycling at different current densities.Moreover,the lithium air battery with Li-GL/NS-CP anode shows the longer cycling life and excellent reversibility in ambient air.In the previous work of this paper,we have synthesized a variety of metal-organic framework?MOFs?derivatives and led to the surface replacement of precious metal nanoparticles to obtain highly efficient lithium air battery catalyst materials?such as Ru-Co4N/Co-NC And Ir@Co/CoxN-HP/NC-CNT?,and the optimized air electrode catalyst material is applied to lithium air batteries for performance research.Using noble metal nanoparticles?Ru,Ir,etc.?to modify the MOFs derivatives to obtain air electrode catalytic materials with high catalytic activity,which can greatly improve the electrochemical performance in lithium air batteries.The experimental results show that Li-GL/NS-CP greatly proves that these excellent results fully prove that Li-GL/NS-CP has potential application value in lithium air batteries.