ScholarWorks@숙명여자대학교

초록

Lithium-oxygen (Li-O2) batteries are an emerging energy storage alternative with the potential to meet the recent increase in demand for high-energy-density batteries. From a practical viewpoint, lithium-air (Li-Air) batteries using ambient air instead of pure oxygen could be the final goal. However, the slow oxygen reduction and evolution reactions interfere with reversible cell operation during cycling. Therefore, research continues to explore various catalyst materials. The present study attempts to improve the performance of Li-Air batteries by using porphyrin-based materials known to have catalytic effects in Li-O2 batteries. The results confirm that the iron phthalocyanine (FePc) catalyst not only exhibits a catalytic effect in an air atmosphere with a low oxygen fraction but also suppresses electrolyte decomposition by stabilizing superoxide radical ions (O2-) at a high voltage range. Density functional theory calculations are used to gain insight into the exact FePc-mediated catalytic mechanism in Li-Air batteries, and various ex situ and in situ analyses reveal the reversible reactions and structural changes in FePc during electrochemical reaction. This study provides a practical solution to ultimately realize an air-breathing battery using nature-friendly catalyst materials. Iron phthalocyanines (FePcs) as a promising bifunctional electrocatalyst are employed in different atmospheric environments using O2 and air-breathing cells for high performance and suppression of side reactions (electrolyte decomposition) in the high voltage range. By using FePc, it simultaneously promotes the battery reaction and suppresses the electrolyte decomposition in the high voltage range (over 4.0 V). Also, when FePc is used in an air atmosphere, O2 and CO2 competitively bind with the central metal of FePc and proceed with the reaction. image

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