锂空气电池中α-MnO_2催化剂孔道内锂-氧之间的空间限域作用
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- 英文论文题名：The Spatially Confined Li-oxygen Interaction in the Tunnel of α-MnO_2 Catalyst for Li-air battery:A First-principles Study
- 论文作者：马忠云 ; 裴勇
- 英文论文作者：Zhongyun Ma ; Yong Pei ; Department of Chemistry ; Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education ; Xiangtan University
- 年：2016
- 作者机构：湘潭大学化学学院环境友好化学与应用教育部重点实验室;
- 论文关键词：α-MnO_2孔道 ; 锂氧物种结构 ; 锂-氧相互作用 ; 半金属性 ; 磁性
- 会议召开时间：2016-07-01
- 会议录名称：中国化学会第30届学术年会摘要集-第十五分会：表界面结构调控与催化
- 语种：中文
- 分类号：TM911.41;O643.36
- 学会代码：ZGHY
- 会议名称：中国化学会第30届学术年会-第十五分会 ; 表界面结构调控与催化
- 会议地点：中国辽宁大连
- 主办单位：中国化学会
- 学会名称：中国化学会
- 页数：1
- 文件大小：330k
- 原文格式：D
- 会议级别：全国
摘要
α-MnO_2作为一种电化学催化剂对提高锂空气电池的循环性能具有很大潜力[1],近年来其催化作用的机理引起研究者们的极大兴趣。α-MnO_2体相内的孔道尺寸较大,实验证实孔道内可容纳H2O、Li2O等物种[2],锂空气电池的放电产物Li2O_2及其衍生物在孔道中的结构对可逆充放电可能起到关键性作用,此外,该孔道也提供了研究限域空间内Li-O作用的绝佳模型。在本工作中[3],我们运用第一性原理计算的方法研究了α-MnO_2的(2×2)维孔道中插入Li,O_2和锂氧化物(LixOy:化学式为LixO_2或LixO4,1≤x≤12)所形成的共混体系的几何结构和电子结构。通过热力学计算我们发现,插入孔道的锂原子与α-MnO_2内壁上的氧原子作用较强,但与插入孔道的O_2则作用很弱。随着孔道内Li原子数目的增加,Li-O作用逐渐增强,并伴随着O-O键的逐渐拉长,直至O_2周围紧密围绕9个Li时,O-O键发生断裂,并在孔道内形成Li2O。电子结构研究显示,作为半导体的α-MnO_2和Li2O_2均不导电,但当二者形成共混体系后,显示出明显的半金属性,大大提高了体系的导电性;α-MnO_2原本为反铁磁性,随着部分Mn原子上磁矩的增加而展现出一定的铁磁性。本工作在理解α-MnO_2确保电池反应的可逆性方面所起的作用提供了新的洞见,也为理性设计性能更好的孔道结构以制备新型高效催化剂提供了重要线索。
α-MnO_2 has great potential as an electrochemical catalyst for promoting the round-trip efficiency of Li-air battery.Herein,we investigated the geometric and electronic structure of α-MnO_2 crystal with its(2×2) tunnel accommodating Lithium,O_2 molecule,and Li-oxygen species(LixOy with the chemical formulas of LixO_2 and LixO4,1≤x≤12) using first-principles calculations.The studies in thermodynamics show that Li+ ions is coordinated strongly with the O atoms in the framework structure of α-MnO_2,while interacts 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 increased the intercalated excess Li in LixO_2 monomers,resulting in the O-O bond lengths be gradually elongated until the bond breaking in Li9O_2 and then converted to Li2 O.These results shed light on the rational design of highly effective catalysts with new tunnel structures in Li-air battery.
α-MnO_2 has great potential as an electrochemical catalyst for promoting the round-trip efficiency of Li-air battery.Herein,we investigated the geometric and electronic structure of α-MnO_2 crystal with its(2×2) tunnel accommodating Lithium,O_2 molecule,and Li-oxygen species(LixOy with the chemical formulas of LixO_2 and LixO4,1≤x≤12) using first-principles calculations.The studies in thermodynamics show that Li+ ions is coordinated strongly with the O atoms in the framework structure of α-MnO_2,while interacts 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 increased the intercalated excess Li in LixO_2 monomers,resulting in the O-O bond lengths be gradually elongated until the bond breaking in Li9O_2 and then converted to Li2 O.These results shed light on the rational design of highly effective catalysts with new tunnel structures in Li-air battery.
引文
[1]Débart,A.;Paterson,A.J.;Bao J.;Bruce,P.G.Angew.Chem.Int.Ed.,2008,47:4521-4524
[2]Johnson,C.S.;Dees,D.W.;Mansuetto,M.F.;Thackeray,M.M.et al.,J.Power Sources,1997,68:570-577
[2]Johnson,C.S.;Dees,D.W.;Mansuetto,M.F.;Thackeray,M.M.et al.,J.Power Sources,1997,68:570-577