Explore the Effects of Microstructural Defects on Voltage Fade of Li- and Mn-Rich Cathodes.
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.
Department of Chemistry, Brookhaven National Laboratory , Upton, New York 11973, United States.
Enyuan
E
Hu
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.|Materials Genome Institute, Shanghai University , Shanghai 200444, China.
Yingchun
Y
Lyu
Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973, United States.
Huolin L
HL
Xin
Department of Chemistry, Brookhaven National Laboratory , Upton, New York 11973, United States.
Jue
J
Liu
Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973, United States.
Lili
L
Han
Department of Chemistry, Brookhaven National Laboratory , Upton, New York 11973, United States.
Seong-Min
SM
Bak
National Synchrotron Light Source II, Brookhaven National Laboratory , Upton, New York 11973, United States.
Jianming
J
Bai
Department of Chemistry, Brookhaven National Laboratory , Upton, New York 11973, United States.|Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.
Xiqian
X
Yu
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.
Hong
H
Li
Department of Chemistry, Brookhaven National Laboratory , Upton, New York 11973, United States.
Xiao-Qing
XQ
Yang
lithium-ion battery; microstructural defect; prelithiation; voltage fade