Comparative analysis of the changes in local Ni/Mn environment in lithium-nickel-manganese oxides with layered and spinel structure during electrochemical extraction and reinsertion of lithium

被引:18
作者
Zhecheva, E. [1 ]
Stoyanova, R. [1 ]
Alcantara, R. [2 ]
Lavela, P. [2 ]
Tirado, J. L. [2 ]
机构
[1] Bulgarian Acad Sci, Inst Gen & Inorgan Chem, BU-1113 Sofia, Bulgaria
[2] Univ Cordoba, Fac Ciencias, Lab Quim Inorgan, Cordoba 14071, Spain
关键词
electrode materials; EPR spectroscopy; local structural characterization; lithium-ion batteries;
D O I
10.1016/j.jpowsour.2007.06.127
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Electron paramagnetic resonance spectroscopy was used to analyse the changes in local Ni, Mn environment in layered LiNi1/2Mn1/2O2 and spinel LiNi1/2Mn3/2O4 after electrochemical extraction and reinsertion of lithium. For layered LiNi1/2Mn1/2O2, the EPR signal from Mn4+ is only detected, while residual antiferromagnetic correlations between Ni2+ and Mn4+ ions gives rise to strong resonance absorption for LiNi1/2Mn3/2O4 spinel. The first charge process of layered LiNi1/2Mn1/2O2 leads to oxidation of Ni2+ ions located both in the transition metal sites and in the Li sites. The reverse process of reduction of these nickel ions was suggested to proceed between 4.4-3.0 V and 2.5-1.4 V, respectively. Lithium extraction from LiNi1/2Mn3/2O4 spinel leads to oxidation of paramagnetic Ni2+ to diamagnetic Ni4+ without significant changes in the local environment of Mn4+. For both fully delithiated compositions, Li1-xNi1/2Mn1/2O2 and Li1-xNi1/2Mn3/2O4, an EPR spectrum from localized Mn4+ ions is observed, indicating an exhaustion of paramagnetic Ni2+ ions in the vicinity of Mn4+ ions. Furthermore, it has been found that the Mn4+ environment including paramagnetic Mn4+ and Ni2+ neighbours is restored after the first cycle of charge/discharge. (C) 2007 Elsevier B.V. All rights reserved.
引用
收藏
页码:519 / 523
页数:5
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