Journal
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
Volume 104, Issue 11, Pages 5934-5945Publisher
WILEY
DOI: 10.1111/jace.17948
Keywords
anode material; band gap; Fermi level; Li4Ti5O12; synergistic mechanism
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Funding
- Beijing Natural Science Foundation [2182082]
- National Natural Science Foundation of China [11675267]
- Scientific Instrument Developing Project [ZDKYYQ20170001]
- International Partnership Program of the Chinese Academy of Sciences [211211KYSB20170060, 211211KYSB20180020]
- Fundamental Research Funds for the Central Universities
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The article presents a synergistic strategy of tuning localized electrons in Li4Ti5O12 through Mg/Zr co-doping and oxygen vacancy incorporation to improve its conductivity. The study reveals that co-doping and vacancy incorporation effectively enhance the dynamic characteristics of the LTO electrode, achieving excellent rate performance and cycle stability.
Li4Ti5O12 (LTO) attracts great interest due to the zero strain during cycles but the poor electronic and ionic conductivity critically impede the practical application. Herein, we report a synergy strategy of tuning localized electrons to shift Fermi level and band gap by Mg/Zr co-doping and oxygen vacancy incorporation, which significantly improves Li+ and electronic transport. More importantly, the intrinsic synergistic mechanism has been revealed by neutron diffraction, X-ray absorption spectra, and first-principles calculations. The elastic effect of lattice induced by Mg/Zr co-doping allows LTO to accommodate more oxygen vacancies to a certain degree without a severe lattice distortion, which largely improves the electronic conductivity. Mg/Zr co-doping and oxygen vacancy incorporation effectively enhanced the dynamic characteristics of LTO electrode, achieving the excellent rate performance (90 mAh/g at 20C) and cycle stability (96.9% after 500 cycles at 10C). First-principles calculations confirm Fermi level shifts to the conduction band, and the band gap becomes narrowed due to the synergistic modulation, and the intrinsic mechanism of the enhanced electronic and Li-ion conductivity is clarified. This study offers some insights into achieving the fast Li+ insertion/extraction by tuning the crystal and electronic structure with lattice doping and oxygen vacancy engineering.
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