Journal
NANO LETTERS
Volume 16, Issue 10, Pages 5999-6007Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.6b01609
Keywords
lithium-ion battery; voltage fade; microstructural defect; prelithiation
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Funding
- U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies [DE-SC0012704]
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-SC0012704, DE-AC02-76SF00515]
- Shanghai Municipal Science and Technology Commission [14DZ2261200]
- National Science Foundation of China [51325206, 51421002]
- Strategic Priority Research Program of the Chinese Academy of Sciences [XDA09010000]
- National project 973 [2012CB932900]
- U.S. DOE [DE-AC02-06CH11357]
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Li- and Mn-rich (LMR) cathode materials have been considered as promising candidates for energy storage applications due to high energy density. However, these materials suffer from a serious problem of voltage fade. Oxygen loss and the layered-to-spinel phase transition are two major contributors of such voltage fade. In this paper, using a combination of X-ray diffraction (XRD), pair distribution function (PDF), X-ray absorption (XAS) techniques, and aberration corrected scanning transmission electron microscopy (STEM), we studied the effects of micro structural defects, especially the grain boundaries, on the oxygen loss and layered-to-spinel phase transition through prelithiation of a model compound Li2Ru0.5Mn0.5O3. It is found that the nanosized micro structural defects, especially the large amount of grain boundaries created by the prelithiation can greatly accelerate the oxygen loss and voltage fade. Defects (such as nanosized grain boundaries) and oxygen release form a positive feedback loop, promote each other during cycling, and accelerate the two major voltage fade contributors: the transition metal reduction and layered-to-spinel phase transition. These results clearly demonstrate the important relationships among the oxygen loss, microstructural defects and voltage fade. The importance of maintaining good crystallinity and protecting the surface of LMR material are also suggested.
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