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

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:
Grant/Contract Number:
AC02-06CH11357
Type:
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
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)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 25 ENERGY STORAGE; humidity; lithium battery; moisture; proton exchange
OSTI Identifier:
1371485