科研之友
微信
新浪微博
Facebook
分享链接
摘要
alpha-MnO2 has great potential as an electrochemical catalyst for promoting the round-trip efficiency of Li-air battery. Herein, by employing first-principles calculations, we investigated the geometric, electronic, and magnetic structures of alpha-MnO2 crystals accommodating lithium, O-2 molecule, and monomeric Li-oxygen species (LixO7 with the chemical formulas of LixO2 or LixO4, 1 <= x <= 12) in the (2 X 2) tunnel with loose-packed density. The studies in thermodynamics show that Li+ ions can readily be intercalated into the tunnel space and are coordinated strongly with the crystalline framework structure of alpha-MnO2, while both the components interact weakly with the inserted O-2 molecules. A pathway for O-2 dissociation in. the tunnel is dominated by the spatially confined interactions between Li+ ions and O-2 moiety, which are enhanced as the intercalated excess Li in LixO2 monomers is increased, resulting in the O-O bond lengths being gradually elongated until the bonds break in Li9O2 monomer and are converted to LixO ones. The calculated electronic arid magnetic structures reveal that the LixOy-inserted alpha-MnO2 structures become half-metallic or metallic or semiconductors with small band gaps and ferrimagnetic spin configuration. These results offer new insights into the important roles of the alpha-MnO2 tunnel structure in assuring the reversible cycles and shed light on the rational design of highly effective Catalysts with new tunnel structures in Li air battery.
- 出版日期2017-8-3
- 单位中南大学
