Journal
ACS NANO
Volume 6, Issue 10, Pages 9158-9167Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nn3034343
Keywords
amorphous silicon carbon nanofiber; interface; crack; lithium ion battery; in situ TEM
Categories
Funding
- Laboratory Directed Research and Development (LDRD) project at Sandia National Laboratories (SNL)
- Nanostructures for Electrical Energy Storage (NEES)
- Energy Frontier Research Center (EFRC)
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DESC0001160]
- LDRD
- NEES center
- Sandia-Los Alamos Center for Integrated Nanotechnologies (CINT)
- U.S. Department of Energy's National Nuclear Security Administration [DE-AC04-94AL85000]
- National Science Foundation [CMMI-1031161]
- OSD SBIR [FA8650-10-C-2041]
- Army SBIR [W56HZV-11-C-0193]
- Div Of Civil, Mechanical, & Manufact Inn
- Directorate For Engineering [0928517] Funding Source: National Science Foundation
- Div Of Civil, Mechanical, & Manufact Inn
- Directorate For Engineering [1031161] Funding Source: National Science Foundation
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Silicon-carbon nanofibers coaxial sponge, with strong mechanical integrity and improved electronic conductivity, is a promising anode structure to apply into commercial high-capacity lithium ion batteries. We characterized the electrochemical and mechanical behatiors of amorphous silicon-coated carbon nanofibers (a-Si/CNFs) with in situ transmission dectron microscopy (TEM). It was found that lithiation of the a-Si coating layer occurred from the surface and the a-Si/CNF Interface concurrently, and propagated toward the center of the a-Si layer. Such a process leads to a sandwiched LixSi/Si/LixSi structure, indicating fast Li transport through the a-Si/CNF interface. Nanocracks and sponge-like structures developed in she a-Si layer during the lithiation-delithiation cycles. Lithiation of the a-Si layer sealed in the hollow CNF was also observed, but at a much lower speed than the counterpart of the a-Si layer coated on the CNF surface. An analytical solution of the stress field was formulated based on the continuum theory of finite deformation, explaining the experimental observation of longitudinal crack formation and general mechanical degradation mechanism in c-Si/CNF electrode.
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