Quantitative analysis of cation mixing and local valence states in LiNixMn2-xO4 using concurrent HARECXS and HARECES measurements
Quantitative analysis of cation mixing and local valence states in LiNixMn2-xO4 using concurrent HARECXS and HARECES measurements
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使用并行 HARECXS 和 HARECES 测量对 LiNixMn2-xO4 中的阳离子混合和局部价态进行定量分析
DOI：
10.1093/jmicro/dfw008
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发表时间：
2016
期刊：
影响因子：
1.8
通讯作者：
S. Muto
中科院分区：
文献类型：
--
作者：
Y. Yamamoto;K. Kataoka;J. Akimoto;K. Tatsumi;T. Kousaka;J. Ohnishi;T. Takahashi;S. Muto
采用高角分辨电子沟道X射线能谱和电子能量损失谱分析了锂离子电池正极材料LiNixMn2−xO4(x=0，0.2，0.5)和Li0.21Ni0.7Mn1.64O4−δ(记为Asx=0.7)中的阳离子混合。量化了四面体锂中心和八面体过渡金属中心之间的混合，并考察了过渡金属的位置相关价态。在未掺杂(x=0)的样品中，发现Mn只占据了Mn3+或Mn4+的八面体位置。Forx=0.2-0.7，部分镍离子(6-13%取决于ONX)占据四面体反位。无论占据位置如何，所有的镍离子都处于二价态。Forx=0.2和0.7，锰离子同时占据八面体和四面体位置；八面体位置上的锰离子是四价的，而四面体位置上的锰离子是二价和三价离子的混合物。Forx=0.5，锰只占据八面体位置，所有离子都被确定为四价态(在实验精度范围内)。所有样品基本上满足局部电荷中性条件。本研究论证了用HARECXS/HARECES定量分析锂锰氧化物尖晶石材料的原子构型和价态的可行性。
Cation mixing in positive electrode materials for rechargeable lithium ion batteries, LiNixMn2−xO4(x= 0, 0.2, 0.5) and Li0.21Ni0.7Mn1.64O4−δ(denoted asx= 0.7), is analyzed by high-angular-resolution electron-channeling X-ray/electron spectroscopy (HARECXS/HARECES) techniques, using energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy. Mixing between the tetrahedral lithium sites and the octahedral transition metal sites is quantified, and the site-dependent valence states of the transition metals are examined. In the non-doped (x= 0) sample, Mn was found to occupy only octahedral sites as either Mn3+or Mn4+. Forx= 0.2–0.7, some of the nickel ions (6–13% depending onx) occupy tetrahedral anti-sites. All the nickel ions are in the divalent state, regardless of the occupation site. Forx= 0.2 and 0.7, manganese ions occupy both octahedral and tetrahedral sites; those in the octahedral sites are tetravalent, while the tetrahedral sites contain a mixture of divalent and trivalent ions. Forx= 0.5, manganese occupies only the octahedral sites, with all ions determined to be in the tetravalent state (within experimental accuracy). All the samples substantially satisfied the local charge neutrality conditions. This study demonstrates the feasibility of using HARECXS/HARECES for quantitative analysis of the atomic configuration and valence states in lithium manganese oxide spinel materials.