Fracture of crystalline silicon nanopillars during electrochemical lithium insertion

Type
Article

Authors
Lee, S. W.
McDowell, M. T.
Berla, L. A.
Nix, W. D.
Cui, Y.

KAUST Grant Number
KUS-l1-001-12
KUK-F1-038-02

Online Publication Date
2012-02-27

Print Publication Date
2012-03-13

Date
2012-02-27

Abstract
From surface hardening of steels to doping of semiconductors, atom insertion in solids plays an important role in modifying chemical, physical, and electronic properties of materials for a variety of applications. High densities of atomic insertion in a solid can result in dramatic structural transformations and associated changes in mechanical behavior: This is particularly evident during electrochemical cycling of novel battery electrodes, such as alloying anodes, conversion oxides, and sulfur and oxygen cathodes. Silicon, which undergoes 400% volume expansion when alloying with lithium, is an extreme case and represents an excellent model system for study. Here, we show that fracture locations are highly anisotropic for lithiation of crystalline Si nanopillars and that fracture is strongly correlated with previously discovered anisotropic expansion. Contrary to earlier theoretical models based on diffusion-induced stresses where fracture is predicted to occur in the core of the pillars during lithiation, the observed cracks are present only in the amorphous lithiated shell. We also show that the critical fracture size is between about 240 and 360 nm and that it depends on the electrochemical reaction rate.

Citation
Lee SW, McDowell MT, Berla LA, Nix WD, Cui Y (2012) Fracture of crystalline silicon nanopillars during electrochemical lithium insertion. Proceedings of the National Academy of Sciences 109: 4080–4085. Available: http://dx.doi.org/10.1073/pnas.1201088109.

Acknowledgements
A portion of this work is supported by the US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Contract DE-AC02-76SF00515 through the Stanford Linear Accelerator Center National Accelerator Laboratory, Laboratory Directed Research and Development project and Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the US DOE under Contract DE-AC02-05CH11231, Subcontract 6951379 under the Batteries for Advanced Transportation Technologies Program. Y.C. acknowledges support from the King Abdullah University of Science and Technology (KAUST) Investigator Award (KUS-l1-001-12). S. W. L. acknowledges support from KAUST (KUK-F1-038-02). M. T. M. acknowledges support from the Chevron Stanford Graduate Fellowship, the National Defense Science and Engineering Graduate Fellowship, and the National Science Foundation Graduate Fellowship. L. A. B. acknowledges support from the National Science Foundation Graduate Research Fellowship and, together with W.D.N., gratefully acknowledges support from the Office of Science, Office of Basic Energy Sciences, of the US DOE under Contract DE-FG02-04-ER46163.

Publisher
Proceedings of the National Academy of Sciences

Journal
Proceedings of the National Academy of Sciences

DOI
10.1073/pnas.1201088109

PubMed ID
22371565

PubMed Central ID
PMC3306693

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