Issue 39, 2023

Direct observations of electrochemically induced intergranular cracking in polycrystalline NMC811 particles

Abstract

Establishing the nature of crack generation, formation, and propagation is paramount to understanding the degradation modes that govern decline in battery performance. Cracking has several possible origins; however, it can be classified in two general cases: mechanically induced, during manufacturing, or electrochemically induced, during operation. Accurate and repeatable tracking of operational cracking to sequentially image the same material as it undergoes cracking is highly challenging; observing these features requires the highest resolutions possible for 3D imaging techniques, necessitating very small sample geometry, while also achieving realistic electrochemical performance. Here, we present a technique in which particle cracking can be completely attributed to electrochemical stimulation via sequential ex situ imaging in a laboratory X-ray nano computed tomography (CT) instrument. This technique preserves the mechanical and electrochemical response of each particle without inducing damage in the particles except for the effects of high voltage. Significant cracking within the core of secondary particles was observed upon the electrochemical delithiation of NMC811, which propagated radially. As X-ray computed tomography allows for imaging of the particle cores, the particles were not required to be modified/milled, guaranteeing any synthesis induced strain in the particles was maintained during the whole technique, resulting in an observation that contrasts crystallographic data, suggesting a significant volume expansion of the secondary particles.

Graphical abstract: Direct observations of electrochemically induced intergranular cracking in polycrystalline NMC811 particles

Supplementary files

Article information

Article type
Paper
Submitted
23 5 2023
Accepted
11 9 2023
First published
18 9 2023
This article is Open Access
Creative Commons BY license

J. Mater. Chem. A, 2023,11, 21322-21332

Direct observations of electrochemically induced intergranular cracking in polycrystalline NMC811 particles

H. C. W. Parks, A. M. Boyce, A. Wade, T. M. M. Heenan, C. Tan, E. Martínez-Pañeda, P. R. Shearing, D. J. L. Brett and R. Jervis, J. Mater. Chem. A, 2023, 11, 21322 DOI: 10.1039/D3TA03057A

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