Depth-Dependent Redox Behavior of LiNi 0.6Mn0.2Co0.2O2

Depth-Dependent Redox Behavior of LiNi 0.6Mn0.2Co0.2O2

TitleDepth-Dependent Redox Behavior of LiNi 0.6Mn0.2Co0.2O2
Publication TypeJournal Article
Year of Publication2018
AuthorsChixia Tian, Dennis Nordlund, Huolin L Xin, Yahong Xu, Yijin Liu, Dimosthenis Sokaras, Feng Lin, Marca M Doeff
JournalJournal of The Electrochemical Society
Volume165
Issue3
PaginationA696 - A704
Date Published03/2018
ISSN0013-4651
Abstract

Nickel-rich layered materials are emerging as cathodes of choice for next-generation high energy density lithium ion batteries intended for electric vehicles. This is because of their higher practical capacities compared to compositions with lower Ni content, as well as the potential for lower raw materials cost. The higher practical capacity of these materials comes at the expense of shorter cycle life, however, due to undesirable structure and chemical transformations, especially at particle surfaces. To understand these changes more fully, the charge compensation mechanism and bulk and surface structural changes of LiNi0.6Mn0.2Co0.2O2 were probed using synchrotron techniques and electron energy loss spectroscopy in this study. In the bulk, both the crystal and electronic structure changes are reversible upon cycling to high voltages, whereas particle surfaces undergo significant reduction and structural reconstruction. While Ni is the major contributor to charge compensation, Co and O (through transition metal-oxygen hybridization) are also redox active. An important finding from depth-dependent transition metal L-edge and O K-edge X-ray spectroscopy is that oxygen redox activity exhibits depth-dependent characteristics. This likely drives the structural and chemical transformations observed at particle surfaces in Ni-rich materials.

DOI10.1149/2.1021803jes
Short TitleJ. Electrochem. Soc.
Refereed DesignationRefereed