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Title: Chemical weathering of layered Ni-rich oxide electrode materials: Evidence for cation exchange

Abstract

Lithiated ternary oxides containing nickel, cobalt, and manganese are intercalation compounds that are used as positive electrodes in high-energy lithium-ion batteries. These materials undergo compositional changes that adversely affect their cycling performance when they are stored in humid air or exposed to moisture. There is a new urgency to better understanding of these “weathering” processes as manufacturing moves towards a more environmentally benign aqueous processing of the positive electrode. Delithiation in the oxide subsurface regions and the formation of lithium salts (such as hydroxides and carbonates) coating the surface, have been suggested as chemical drivers for these processes, but the mechanistic details remain poorly known. The redox reactions which follow oxide delithiation are believed to cause all of the observed transformations. In this article we suggest another possibility: namely, the proton – lithium exchange. We argue that this hypothesis provides a simple, comprehensive rationale for our observations from X-ray diffraction, X-ray photoelectron spectroscopy, scanning transmission electron microscopy, and electrochemical measurements. These observations include contraction of the c-axis (unit cell) lattice parameter, strain in the crystalline oxide bulk, directionality of the chemical damage, formation of amorphous surface films, and the partial recovery of capacity loss by electrochemical relithiation of the material.more » Lastly, these effects need to be mitigated before aqueous processing of the positive electrode can find widespread adoption during cell manufacturing.« less

Authors:
 [1];  [1];  [2];  [2];  [3];  [1];  [1]
  1. Argonne National Lab. (ANL), Argonne, IL (United States)
  2. Univ. of Illinois at Chicago, Chicago, IL (United States)
  3. Univ. of Illinois at Urbana-Champaign, Urbana, IL (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22), Joint Center for Energy Storage Research (JCESR)
OSTI Identifier:
1371485
Grant/Contract Number:
AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of the Electrochemical Society
Additional Journal Information:
Journal Volume: 164; Journal Issue: 7; Journal ID: ISSN 0013-4651
Publisher:
The Electrochemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 25 ENERGY STORAGE; humidity; lithium battery; moisture; proton exchange

Citation Formats

Shkrob, Ilya A., Gilbert, James A., Phillips, Patrick J., Klie, Robert, Haasch, Richard T., Bareno, Javier, and Abraham, Daniel P.. Chemical weathering of layered Ni-rich oxide electrode materials: Evidence for cation exchange. United States: N. p., 2017. Web. doi:10.1149/2.0861707jes.
Shkrob, Ilya A., Gilbert, James A., Phillips, Patrick J., Klie, Robert, Haasch, Richard T., Bareno, Javier, & Abraham, Daniel P.. Chemical weathering of layered Ni-rich oxide electrode materials: Evidence for cation exchange. United States. doi:10.1149/2.0861707jes.
Shkrob, Ilya A., Gilbert, James A., Phillips, Patrick J., Klie, Robert, Haasch, Richard T., Bareno, Javier, and Abraham, Daniel P.. Sat . "Chemical weathering of layered Ni-rich oxide electrode materials: Evidence for cation exchange". United States. doi:10.1149/2.0861707jes. https://www.osti.gov/servlets/purl/1371485.
@article{osti_1371485,
title = {Chemical weathering of layered Ni-rich oxide electrode materials: Evidence for cation exchange},
author = {Shkrob, Ilya A. and Gilbert, James A. and Phillips, Patrick J. and Klie, Robert and Haasch, Richard T. and Bareno, Javier and Abraham, Daniel P.},
abstractNote = {Lithiated ternary oxides containing nickel, cobalt, and manganese are intercalation compounds that are used as positive electrodes in high-energy lithium-ion batteries. These materials undergo compositional changes that adversely affect their cycling performance when they are stored in humid air or exposed to moisture. There is a new urgency to better understanding of these “weathering” processes as manufacturing moves towards a more environmentally benign aqueous processing of the positive electrode. Delithiation in the oxide subsurface regions and the formation of lithium salts (such as hydroxides and carbonates) coating the surface, have been suggested as chemical drivers for these processes, but the mechanistic details remain poorly known. The redox reactions which follow oxide delithiation are believed to cause all of the observed transformations. In this article we suggest another possibility: namely, the proton – lithium exchange. We argue that this hypothesis provides a simple, comprehensive rationale for our observations from X-ray diffraction, X-ray photoelectron spectroscopy, scanning transmission electron microscopy, and electrochemical measurements. These observations include contraction of the c-axis (unit cell) lattice parameter, strain in the crystalline oxide bulk, directionality of the chemical damage, formation of amorphous surface films, and the partial recovery of capacity loss by electrochemical relithiation of the material. Lastly, these effects need to be mitigated before aqueous processing of the positive electrode can find widespread adoption during cell manufacturing.},
doi = {10.1149/2.0861707jes},
journal = {Journal of the Electrochemical Society},
number = 7,
volume = 164,
place = {United States},
year = {Sat May 13 00:00:00 EDT 2017},
month = {Sat May 13 00:00:00 EDT 2017}
}

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  • The Ni-rich layered oxides with a Ni content of >0.5 are drawing much attention recently to increase the energy density of lithium-ion batteries. However, the Ni-rich layered oxides suffer from aggressive reaction of the cathode surface with the organic electrolyte at the higher operating voltages, resulting in consequent impedance rise and capacity fade. To overcome this difficulty, we present here a heterostructure composed of a Ni-rich LiNi 0.7Co 0.15Mn 0.15O 2 core and a Li-rich Li 1.2-xNi 0.2Mn 0.6O 2 shell, incorporating the advantageous features of the structural stability of the core and chemical stability of the shell. With amore » unique chemical treatment for the activation of the Li 2MnO 3 phase of the shell, a high capacity is realized with the Li-rich shell material. Aberration-corrected scanning transmission electron microscopy (STEM) provides direct evidence for the formation of surface Li-rich shell layer. Finally, the heterostructure exhibits a high capacity retention of 98% and a discharge- voltage retention of 97% during 100 cycles with a discharge capacity of 190 mA h g -1 (at 2.0–4.5 V under C/3 rate, 1C = 200 mA g -1).« less
  • Capacity and voltage fading of layer structured cathode based on lithium transition metal oxide is closely related to the lattice position and migration behavior of the transition metal ions. However, it is scarcely clear about the behavior of each of these transition metal ions. We report direct atomic resolution visualization of interatomic layer mixing of transition metal (Ni, Co, Mn) and lithium ions in layer structured oxide cathodes for lithium ion batteries. Using chemical imaging with aberration corrected scanning transmission electron microscope (STEM) and DFT calculations, we discovered that in the layered cathodes, Mn and Co tend to reside almostmore » exclusively at the lattice site of transition metal (TM) layer in the structure or little interlayer mixing with Li. In contrast, Ni shows high degree of interlayer mixing with Li. The fraction of Ni ions reside in the Li layer followed a near linear dependence on total Ni concentration before reaching saturation. The observed distinctively different behavior of Ni with respect to Co and Mn provides new insights on both capacity and voltage fade in this class of cathode materials based on lithium and TM oxides, therefore providing scientific basis for selective tailoring of oxide cathode materials for enhanced performance.« less
  • The impedance of a lithium- and manganese-rich layered transition-metal oxide (MR-NMC) positive electrode, specifically Li 1.2Ni 0.15Mn 0.55Co 0.1O 2, is compared to two other transition-metal layered oxide materials, specifically LiNi 0.8Co 0.15Al 0.05O 2 (NCA) and Li 1.05(Ni 1/3Co 1/3Mn 1/3) 0.95O 2 (NMC). A more detailed electrochemical impedance spectroscopy (EIS) study is conducted on the LMR-NMC electrode, which includes a range of states-of-charge (SOCs) for both current directions (i.e. charge and discharge) and two relaxation times (i.e. hours and one hundred hours) before the EIS sweep. The LMR-NMC electrode EIS studies are supported by half-cell constant current andmore » galvanostatic intermittent titration technique (GITT) studies. Two types of electrochemical models are utilized to examine the results. The first type is a lithium ion cell electrochemical model for intercalation active material electrodes that includes a complex active material/electrolyte interfacial structure. In conclusion, the other is a lithium ion half-cell electrochemical model that focuses on the unique composite structure of the bulk LMR-NMC materials.« less