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Title: Competing Mechanisms in CO Hydrogenation over Co-MnO x Catalysts
Award ID(s):
1438227
NSF-PAR ID:
10131837
Author(s) / Creator(s):
; ; ; ; ;
Date Published:
Journal Name:
ACS Catalysis
Volume:
9
Issue:
6
ISSN:
2155-5435
Page Range / eLocation ID:
5603 to 5612
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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  1. Abstract

    Most research on the electrochemical dynamics in materials for high‐energy Li‐ion batteries has focused on the global behavior of the electrode. This approach is susceptible to misleading analyses resulting from idiosyncratic kinetic conditions, such as surface impurities inducing an apparent two‐phase transformation within LiNi0.8Co0.15Al0.05O2. Here, nano‐focused X‐ray probes are used to measure delithiation operando at the scale of secondary particle agglomerates in layered cathode materials during charge. After an initial latent phase, individual secondary particles undergo rapid, stochastic, and largely uniform delithiation, which is in contrast with the gradual increase in cell potential. This behavior reproduces across several layered oxides. Operando X‐ray microdiffraction (‐XRD) leverages the relationship between Li content and lattice parameter to further reveal that rate acceleration occurs between Li‐site fraction (xLi) ≈0.9 and ≈0.5 for LiNi0.8Co0.15Al0.05O2. Physics‐based modeling shows that, to reproduce the experimental results, the exchange current density (i0) must depend onxLi, and thati0should increase rapidly over three orders of magnitude at the transition point. The specifics and implications of this jump ini0are crucial to understanding the charge‐storage reaction of Li‐ion battery cathodes.

     
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