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Title: Structural transformations in high-capacity Li 2Cu 0.5Ni 0.5O 2 cathodes

Cathode materials that can cycle >1 Li + per transition metal are of substantial interest for increasing the overall energy density of lithium-ion batteries. Li 2Cu 0.5Ni 0.5O 2 has a very high theoretical capacity of ~500 mAh/g assuming both Li+ ions are cycled reversibly. The Cu 2+/3+ and Ni 2+/3+/4+ redox couples are also at high voltage, which could further boost the energy density of this system. Despite such promise, Li 2Cu 0.5Ni 0.5O 2 undergoes irreversible phase changes during charge (delithiation) that result in large first-cycle irreversible loss and poor long-term cycling stability. Oxygen evolves before the Cu 2+/3+ or Ni 3+/4+ transitions are accessed. In this contribution, X-ray diffraction, transmission electron microscopy (TEM), and transmission X-ray microscopy combined with X-ray absorption near edge structure (TXM–XANES) are used to follow the chemical and structural changes that occur in Li 2Cu 0.5Ni 0.5O 2 during electrochemical cycling. Li 2Cu 0.5Ni 0.5O 2 is a solid solution of orthorhombic Li2CuO2 and Li2NiO2, but the structural changes more closely mimic the changes that the Li 2NiO 2 endmember undergoes. Li 2Cu 0.5Ni 0.5O 2 loses long-range order during charge, but TEM analysis provides clear evidence of particle exfoliation and the transformationmore » from orthorhombic to a partially layered structure. Linear combination fitting and principal component analysis of TXM–XANES are used to map the different phases that emerge during cycling ex situ and in situ. Lastly, significant changes in the XANES at the Cu and Ni K-edges correlate with the onset of oxygen evolution.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [2] ;  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725; AC02-76SF00515
Type:
Accepted Manuscript
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 29; Journal Issue: 7; Journal ID: ISSN 0897-4756
Publisher:
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1350931
Alternate Identifier(s):
OSTI ID: 1361140