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Title: Depth-Dependent Redox Behavior of LiNi 0.6Mn 0.2Co 0.2O 2

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 LiNi 0.6Mn 0.2Co 0.2O 2 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. In conclusion, this likely drives the structural and chemical transformations observed at particle surfaces in Ni-rich materials.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [2] ;  [2] ; ORCiD logo [5] ; ORCiD logo [1]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
  4. SLAC National Accelerator Lab., Menlo Park, CA (United States); Donghua Univ., Shanghai (People's Republic of China)
  5. Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231; SC0012704; AC02-76SF00515
Type:
Published Article
Journal Name:
Journal of the Electrochemical Society
Additional Journal Information:
Journal Volume: 165; Journal Issue: 3; Journal ID: ISSN 0013-4651
Publisher:
The Electrochemical Society
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; cathode; Li-ion battery; NMC
OSTI Identifier:
1425689
Alternate Identifier(s):
OSTI ID: 1458538