Guo Shasha, Koketsu Toshinari, Hu Zhiwei, Zhou Jing, Kuo Chang-Yang, Lin Hong-Ji, Chen Chien-Te, Strasser Peter, Sui Lijun, Xie Yu, Ma Jiwei
Shanghai Key Laboratory for R&D and Application of Metallic Functional Materials, Institute of New Energy for Vehicles, School of Materials Science and Engineering, Tongji University, Shanghai, 201804, P. R. China.
Department of Chemistry, Technical University of Berlin, 10623, Berlin, Germany.
Small. 2022 Oct;18(40):e2203835. doi: 10.1002/smll.202203835. Epub 2022 Sep 4.
Transition metal oxides (TMOs) as high-capacity electrodes have several drawbacks owing to their inherent poor electronic conductivity and structural instability during the multi-electron conversion reaction process. In this study, the authors use an intrinsic high-valent cation substitution approach to stabilize cation-deficient magnetite (Fe O ) and overcome the abovementioned issues. Herein, 5 at% of Mo -ions are incorporated into the spinel structure to substitute octahedral Fe -ions, featuring ≈1.7 at% cationic vacancies in the octahedral sites. This defective Fe ▫ Mo O electrode shows significant improvements in the mitigation of capacity fade and the promotion of rate performance as compared to the pristine Fe O . Furthermore, physical-electrochemical analyses and theoretical calculations are performed to investigate the underlying mechanisms. In Fe ▫ Mo O , the cationic vacancies provide active sites for storing Li and vacancy-mediated Li migration paths with lower energy barriers. The enlarged lattice and improved electronic conductivity induced by larger doped-Mo yield this defective oxide capable of fast lithium intercalation. This is confirmed by a combined characterization including electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT) and density functional theory (DFT) calculation. This study provides a valuable strategy of vacancy-mediated reaction to intrinsically modulate the defective structure in TMOs for high-performance lithium-ion batteries.
过渡金属氧化物（TMOs）作为高容量电极，由于其固有的电子导电性差以及在多电子转换反应过程中的结构不稳定性，存在几个缺点。在本研究中，作者采用本征高价阳离子取代方法来稳定阳离子缺陷磁铁矿（Fe₃O₄）并克服上述问题。在此，5原子百分比的Mo⁶⁺离子被引入尖晶石结构以取代八面体Fe³⁺离子，在八面体位点具有约1.7原子百分比的阳离子空位。与原始的Fe₃O₄相比，这种有缺陷的Fe₃₋ₓMoₓO₄电极在减轻容量衰减和提高倍率性能方面有显著改善。此外，进行了物理电化学分析和理论计算以研究其潜在机制。在Fe₃₋ₓMoₓO₄中，阳离子空位为存储Li提供了活性位点，并提供了具有较低能垒的空位介导的Li迁移路径。由较大的掺杂Mo引起的晶格扩大和电子导电性改善，使得这种有缺陷的氧化物能够快速嵌入锂。这通过包括电化学阻抗谱（EIS）、循环伏安法（CV）、恒电流间歇滴定技术（GITT）和密度泛函理论（DFT）计算在内的综合表征得到证实。本研究提供了一种有价值的空位介导反应策略，以本征方式调节TMOs中的缺陷结构用于高性能锂离子电池。
