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.
|Number of pages||9|
|Publication status||Published - 2016 Oct 12|
Bibliographical noteFunding Information:
The work at Brookhaven National Laboratory was supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies under Contract No. DE-SC0012704. Use of the beamline (28ID) at National Synchrotron Light Source II (NSLS-II) and STEM at Center for Functional Nanomaterials of Brookhaven National Laboratory were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contracts No. DE-SC0012704. Y.L. is supported by the Shanghai Municipal Science and Technology Commission (No. 14DZ2261200). H.L. is supported by National Science Foundation of China (51325206, 51421002), "Strategic Priority Research Program" of the Chinese Academy of Sciences (XDA09010000) and National project 973 (2012CB932900). We acknowledge technical support from the scientists at beamline 12-BM-B and 17-BMB of APS (ANL), supported by the U.S. DOE under Contract No. DE-AC02-06CH11357. Part of this research was conducted at the BL2-2 of Stanford Synchrotron Radiation Lightsource. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515.
© 2016 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanical Engineering