Chemical and Morphological Changes of High Voltage Lithium-Manganese Rich Cathodes with Cycling

Researchers used full-field transmission X-ray microscopy (TXM), capable of 3D imaging at high spatial resolution over a field of view of about 30×30×30 μm, to study the mechanisms driving structural degradation and voltage fade in a high capacity cathode material with nominal composition Li_1.2Mn_0.525Ni_0.175Co_0.1O₂. This high-potential cathode material promises almost twice the useable capacity (~280 mAh/g) as standard cathodes. Unfortunately, when this material is electrochemically cycled at voltages greater than 4.5 V, there is significant loss of energy as the cathode is progressively cycled, making the material unsuitable for practical applications.

TXM analysis in this study provides both the spatial resolution (~30 nm) and spectroscopic capability in 2D and 3D required to distinguish the distinct evolution of bulk and surface regions of the battery materials, and to follow the emergence of new local phases. Comparison of morphology and 3D internal structure of electrodes processed through multiple charge cycles provides direct information about particle breakup and changes in chemical phase during electrochemical cycling, providing valuable insight into the degradation mechanism at a materials level.

ORNL research for this project was sponsored by the DOE Vehicle Technologies Office.

Citation:

Feifei Yang, Yijin Liu, Surendra K. Martha, Ziyu Wu, Joy C. Andrews, Gene E Ice, Piero Pianneta, Jagjit Nanda, “Nanoscale Morphological and Chemical Changes of High Voltage Lithium-Manganese Rich NMC Composite Cathodes with Cycling, ” Nano Letters. DOI: 10.1021/nl502090z

For more information, please contact Jagjit Nanda.