Design Of LaMnO₃ Based Oxygen Catalytic Electrode And Its Performance Of Zn-air Battery

The growing demand for safe,clean and renewable energy has prompted researchers to conduct large-scale research on new energy batteries.To date,Li-ion batteries are deemed to be one of the most mature rechargeable battery technology,and have been widely commercialized in consumer products including electric vehicles,medical devices,and other portable electronics.However,due to their high cost,unsatisfactory energy density,and potential toxicity of Li-ion batteries,researchers have begun searching for other alternatives.Zn-air batteries（ZABs）with high inherent theoretical energy density and safety have become one of excellent candidates for the new generation of electric transportation and electrical energy storage systems.However,the biggest technical obstacle to the commercialization of ZABs is the sluggish kinetics of oxygen reduction and oxygen evolution reactions（ORR and OER）that occur at the air cathode.Although some noble metal-based catalysts（such as Pt/C,Ru O₂,etc.）are still the focus of some researchers due to their high intrinsic ORR/OER catalytic activities,it is undeniable that their high cost and low stability caused by the scarcity of noble metals in nature will be two major problems that limit the industrialization of their application.Therefore,it is of great significance to seek a non-noble metal-based catalyst with abundant natural resources,high catalytic activity,and excellent stability.Perovskite materials have attracted a lot of attention due to their abundant resources and good stability.This paper mainly focuses on the LaMnO₃ perovskite oxide with good intrinsic catalytic activity towards ORR.By optimizing the design of its material,its bi-functionality is increased and its ORR catalytic performance is further improved,so that the LaMnO₃ perovskite oxide can be one of promising air electrode of Zn-air batteries.The specific work is as follows:（1）We used a simple and easy-to-operate ultrasonic mixing technology to prepare a LaMnO₃-CoO composite material to improve the OER catalytic activity of LaMnO₃perovskite oxide.The composite material was then applied as an air electrode material of Zn-air battery,and its charge-discharge performance and cycle stability were studied,so as to discuss the influence of CoO on the reliability of LaMnO₃ perovskite oxide.The results showed that the abundant chemisorbed oxygen active sites on the surface of CoO nanoparticles can enhance the catalytic activity of the composite electrode for ORR,and the introduction of CoO nanoparticles successfully overcome the problem of unsatisfactory OER performance of LaMnO3 perovskite oxides.The LaMnO3-CoO composite achieved a current density of 10 m A cm-2 at 550 m V and showed a much smaller Tafel slope value of 146 m V dec-1 than that of pure LaMnO3 oxide with 213 m V dec-1.In addition,the Zn-air battery with LaMnO3-CoO composite material as the air electrode can still achieve a high voltammetric efficiency of 58.6% even after 150 charge-discharge cycles,and its stability was much higher than that of the Pt/C+Ru O2 catalyst（51.3%）.This work fully demonstrates that developing LaMnO3 perovskite oxide-based composites enables highly durable and efficient bifunctional electrocatalysts,while also providing important ideas for enhancing the versatility of materials.（2）We applied urea as an additive for the preparation of LaMnO3 perovskite oxide by a sol-gel method,and achieved the regulation of A-site vacancies in LaMnO3 perovskite oxide by the one-step method.Studies showed that the proper introduction of urea can adjust the A-site vacancies of LaMnO3 perovskite oxide,thereby distorting the perovskite lattice and increasing its lattice oxygen content.After optimizing the amount of urea,it was found that the 3.0U-LaMnO3（3.0U-LMO,the molar ratio of urea to total metal ions was 3）catalyst with more La vacancies（VLa）exhibited the most excellent electrocatalytic activity.Its ORR reaction showed a maximum half-wave potential of 0.74 V and a limiting current density of 5.737 m A cm-2.The excellent performance of 3.0U-LMO was attributed to the easier charge transfer from Mn to O in the Mn O6 octahedron,which activated the more surface active lattice oxygen and enhanced the oxygen reduction performance of LaMnO3 perovskite.In addition,the Zn-air battery with 3.0U-LMO as the air electrode exhibited good cycle stability with a high voltammetric efficiency of 55.3% after 150 charge-discharge cycles,which was much higher than that of Pt/ C+Ru O2 catalyst with a value of 51.3%.This work provides a new strategy for designing perovskite oxides with A-site defects as the air electrode for highly active zinc-air batteries,which is simple to operate,cost-effective,and suitable for large-scale fabrication.