Mo‐Incorporated Magnetite Fe3O4 Featuring Cationic Vacancies Enabling Fast Lithium Intercalation for Batteries

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2022-10, Vol.18 (40), p.n/a
• Main Authors: 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
• Format: Article
• Language: English
• Subjects: Cations; cation‐deficient Fe 3O 4; Density functional theory; Electrochemical analysis; Electrochemical impedance spectroscopy; Electrodes; fast Li intercalation; Intercalation; Iron oxides; kinetics; Lattice vacancies; Lithium; Lithium-ion batteries; Magnetite; Mathematical analysis; mechanistic insights; molybdenum‐doping; Nanotechnology; Structural stability; Substitution reactions; Titration; Transition metal oxides
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202203835

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 (Fe3O4) and overcome the abovementioned issues. Herein, 5 at% of Mo4+‐ions are incorporated into the spinel structure to substitute octahedral Fe3+‐ions, featuring ≈1.7 at% cationic vacancies in the octahedral sites. This defective Fe2.93▫0.017Mo0.053O4 electrode shows significant improvements in the mitigation of capacity fade and the promotion of rate performance as compared to the pristine Fe3O4. Furthermore, physical‐electrochemical analyses and theoretical calculations are performed to investigate the underlying mechanisms. In Fe2.93▫0.017Mo0.053O4, 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‐Mo4+ 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. The Fe2.93▫0.017Mo0.053O4 is tailored by controlled substitution of octahedral Fe3+‐ions with high‐valent Mo4+‐ions via a simple and economical sol‐gel method. The presence of cationic vacancies in combination with the enhanced electronic conductivity enable fast lithium intercalation, mitigate the capacity fade, and improve the rate performance in lithium‐ion batteries.