Singh Harishchandra, Topsakal Mehmet, Attenkofer Klaus, Wolf Tamar, Leskes Michal, Duan Yandong, Wang Feng, Vinson John, Lu Deyu, Frenkel Anatoly I
Department of Materials Science and Chemical Engineering, Stony Brook University, Stony Brook, New York 11794, United States.
Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States.
Phys Rev Mater. 2018;2. doi: 10.1103/PhysRevMaterials.2.125403.
Doped metal oxide materials are commonly used for applications in energy storage and conversion, such as batteries and solid oxide fuel cells. The knowledge of the electronic properties of dopants and their local environment is essential for understanding the effects of doping on the electrochemical properties. Using a combination of X-ray absorption near-edge structure spectroscopy (XANES) experiment and theoretical modeling we demonstrate that in the dilute (1 at. %) Mn-doped lithium titanate (LiTiO, or LTO) the dopant Mn ions reside on tetrahedral (8) sites. First-principles Mn K-edge XANES calculations revealed the spectral signature of the tetrahedrally coordinated Mn as a sharp peak in the middle of the absorption edge rise, caused by the 1 → 4 transition, and it is important to include the effective electron-core hole Coulomb interaction in order to calculate the intenisty of this peak accurately. This dopant location explains the impedance of Li migration through the LTO lattice during the charge-discharge process, and, as a result - the observed remarkable 20% decrease in electrochemical rate performance of the 1% Mn-doped LTO compared to the pristine LTO.
掺杂金属氧化物材料通常用于能量存储和转换应用，如电池和固体氧化物燃料电池。了解掺杂剂的电子性质及其局部环境对于理解掺杂对电化学性质的影响至关重要。通过结合X射线吸收近边结构光谱（XANES）实验和理论建模，我们证明在稀（1原子%）锰掺杂的钛酸锂（LiTiO，或LTO）中，掺杂的锰离子位于四面体（8）位点。第一性原理锰K边XANES计算揭示了四面体配位锰的光谱特征，表现为吸收边上升中部的一个尖锐峰，这是由1→4跃迁引起的，为了准确计算该峰的强度，考虑有效电子-核空穴库仑相互作用很重要。这种掺杂剂位置解释了充放电过程中锂通过LTO晶格迁移的阻抗，结果是，与原始LTO相比，1%锰掺杂的LTO的电化学速率性能显著下降了20%。
