期刊
CHEMISTRY OF MATERIALS
卷 25, 期 13, 页码 2691-2699出版社
AMER CHEMICAL SOC
DOI: 10.1021/cm401293r
关键词
olivine; site substitution; Li electrochemistry; sarcopside
资金
- Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center
- U.S. Department of Energy, Office of Science, Basic Energy Sciences [DE-SC0001294, DE-AC02-06CH11357, DE-AC02-98CH10886]
- Oak Ridge National Laboratory's Spallation Neutron Source
- Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy
- National Institute of Standards and Technology, U.S. Department of Commerce
The crystal structure and delithiation mechanism of Li-site substituted LiFePO4 have been revealed by investigation of supervalent V3+ substitution. The combined X-ray and neutron powder diffraction data analysis surprisingly shows that the substituting aliovalent vanadium ions occupy the Fe site while some of the Fe resides at the Li site, probably as sarcopside, which leads to an increase in the unit cell volume. Such substitution reduces the miscibility gap at room temperature and also significantly lowers the solid solution formation temperature in the two-phase region. The effect of the phase diagram modification results in improved kinetics, leading to better rate performance. Such substitution, however, significantly lowers the LiFePO4 capacity at moderate current densities.
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