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Title: Structural Transformations in High-Capacity Li 2 Cu 0.5 Ni 0.5 O 2 Cathodes

Abstract

Cathode materials that can cycle > 1 Li+ per transition metal are of substantial interest to increase the overall energy density of lithium-ion batteries. Li2Cu0.5Ni0.5O2 has a very high theoretical capacity of ~ 500 mAh/g assuming both Li+ are cycled reversibly. The Cu2+/3+ and Ni2+/3+/4+ redox couples are also at high voltage, which could further boost the energy density of this system. Despite such promise, Li2Cu0.5Ni0.5O2 undergoes irreversible phase changes during charge (delithiation) that result in large first-cycle irreversible loss and poor long-term cycling stability. Oxygen is evolved before the Cu2+/3+ or Ni3+/4+ transitions are accessed. In this contribution, XRD, TEM, and TXM-XANES are used to follow the chemical and structural changes that occur in Li2Cu0.5Ni0.5O2 during electrochemical cycling. Li2Cu0.5Ni0.5O2 is a solid solution of orthorhombic Li2CuO2 and Li2NiO2, but the structural changes more closely mimic the Li2NiO2 endmember. Li2Cu0.5Ni0.5O2 loses long-range order during charge, but TEM analysis provides clear evidence for particle exfoliation and the transformation 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. Significant changes in the XANES at the Cu and Ni K-edgesmore » correlate with the onset of oxygen evolution.« less

Authors:
ORCiD logo; ORCiD logo; ; ; ; ORCiD logo
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
OSTI Identifier:
1356495
Report Number(s):
PNNL-SA-123197
Journal ID: ISSN 0897-4756; 49321; KP1704020
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemistry of Materials; Journal Volume: 29; Journal Issue: 7
Country of Publication:
United States
Language:
English
Subject:
Environmental Molecular Sciences Laboratory

Citation Formats

Ruther, Rose E., Samuthira Pandian, Amaresh, Yan, Pengfei, Weker, Johanna Nelson, Wang, Chongmin, and Nanda, Jagjit. Structural Transformations in High-Capacity Li 2 Cu 0.5 Ni 0.5 O 2 Cathodes. United States: N. p., 2017. Web. doi:10.1021/acs.chemmater.6b05442.
Ruther, Rose E., Samuthira Pandian, Amaresh, Yan, Pengfei, Weker, Johanna Nelson, Wang, Chongmin, & Nanda, Jagjit. Structural Transformations in High-Capacity Li 2 Cu 0.5 Ni 0.5 O 2 Cathodes. United States. doi:10.1021/acs.chemmater.6b05442.
Ruther, Rose E., Samuthira Pandian, Amaresh, Yan, Pengfei, Weker, Johanna Nelson, Wang, Chongmin, and Nanda, Jagjit. Tue . "Structural Transformations in High-Capacity Li 2 Cu 0.5 Ni 0.5 O 2 Cathodes". United States. doi:10.1021/acs.chemmater.6b05442.
@article{osti_1356495,
title = {Structural Transformations in High-Capacity Li 2 Cu 0.5 Ni 0.5 O 2 Cathodes},
author = {Ruther, Rose E. and Samuthira Pandian, Amaresh and Yan, Pengfei and Weker, Johanna Nelson and Wang, Chongmin and Nanda, Jagjit},
abstractNote = {Cathode materials that can cycle > 1 Li+ per transition metal are of substantial interest to increase the overall energy density of lithium-ion batteries. Li2Cu0.5Ni0.5O2 has a very high theoretical capacity of ~ 500 mAh/g assuming both Li+ are cycled reversibly. The Cu2+/3+ and Ni2+/3+/4+ redox couples are also at high voltage, which could further boost the energy density of this system. Despite such promise, Li2Cu0.5Ni0.5O2 undergoes irreversible phase changes during charge (delithiation) that result in large first-cycle irreversible loss and poor long-term cycling stability. Oxygen is evolved before the Cu2+/3+ or Ni3+/4+ transitions are accessed. In this contribution, XRD, TEM, and TXM-XANES are used to follow the chemical and structural changes that occur in Li2Cu0.5Ni0.5O2 during electrochemical cycling. Li2Cu0.5Ni0.5O2 is a solid solution of orthorhombic Li2CuO2 and Li2NiO2, but the structural changes more closely mimic the Li2NiO2 endmember. Li2Cu0.5Ni0.5O2 loses long-range order during charge, but TEM analysis provides clear evidence for particle exfoliation and the transformation 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. Significant changes in the XANES at the Cu and Ni K-edges correlate with the onset of oxygen evolution.},
doi = {10.1021/acs.chemmater.6b05442},
journal = {Chemistry of Materials},
number = 7,
volume = 29,
place = {United States},
year = {Tue Mar 21 00:00:00 EDT 2017},
month = {Tue Mar 21 00:00:00 EDT 2017}
}