Bock David C, Tallman Killian R, Guo Haoyue, Quilty Calvin, Yan Shan, Smith Paul F, Zhang Bingjie, Lutz Diana M, McCarthy Alison H, Huie Matthew M, Burnett Veronica, Bruck Andrea M, Marschilok Amy C, Takeuchi Esther S, Liu Ping, Takeuchi Kenneth J
Energy Science and Photon Sciences Directorate, Brookhaven National Laboratory, Upton, NY 11973, USA.
Phys Chem Chem Phys. 2020 Nov 25;22(45):26200-26215. doi: 10.1039/d0cp02322a.
Iron based materials hold promise as next generation battery electrode materials for Li ion batteries due to their earth abundance, low cost, and low environmental impact. The iron oxide, magnetite Fe3O4, adopts the spinel (AB2O4) structure. Other 2+ cation transition metal centers can also occupy both tetrahedral and/or octahedral sites in the spinel structure including MgFe2O4, a partially inverse spinel, and ZnFe2O4, a normal spinel. Though structurally similar to Fe3O4 in the pristine state, previous studies suggest significant differences in structural evolution depending on the 2+ cation in the structure. This investigation involves X-ray absorption spectroscopy and X-ray diffraction affirmed by density functional theory (DFT) to elucidate the role of the 2+ cation on the structural evolution and phase transformations during (de)lithiation of the spinel ferrites Fe3O4, MgFe2O4, and ZnFe2O4. The cation in the inverse, normal and partially inverse spinel structures located in the tetrahedral (8a) site migrates to the previously unoccupied octahedral 16c site by 2 electron equivalents of lithiation, resulting in a disordered [A]16c[B2]16dO4 structure. DFT calculations support the experimental results, predicting full displacement of the 8a cation to the 16c site at 2 electron equivalents. Substitution of the 2+ cation results in segregation of oxidized phases in the charged state. This report provides significant structural insight into the (de)lithiation mechanisms for an intriguing class of iron oxide materials.
由于铁基材料在地壳中储量丰富、成本低廉且对环境影响较小，因此有望成为下一代锂离子电池的电极材料。氧化铁磁铁矿Fe3O4具有尖晶石（AB2O4）结构。其他2 +阳离子过渡金属中心也可以占据尖晶石结构中的四面体和/或八面体位点，包括部分反尖晶石MgFe2O4和正尖晶石ZnFe2O4。尽管在原始状态下结构与Fe3O4相似，但先前的研究表明，根据结构中的2 +阳离子不同，其结构演变存在显著差异。本研究采用X射线吸收光谱和X射线衍射，并通过密度泛函理论（DFT）进行验证，以阐明2 +阳离子在尖晶石铁氧体Fe3O4、MgFe2O4和ZnFe2O4的（脱）锂过程中对结构演变和相变的作用。反尖晶石、正尖晶石和部分反尖晶石结构中位于四面体（8a）位点的阳离子通过2个电子当量的锂化迁移到先前未占据的八面体16c位点，从而形成无序的[A]16c[B2]16dO4结构。DFT计算支持了实验结果，预测在2个电子当量时8a阳离子会完全迁移到16c位点。2 +阳离子的取代导致充电状态下氧化相的分离。本报告为一类有趣的氧化铁材料的（脱）锂机制提供了重要的结构见解。
