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. 2011 Jul 1;196(13):5659-5666.
doi: 10.1016/j.jpowsour.2011.02.036.

Solid-State Nuclear Magnetic Resonance Studies of Electrochemically Discharged CF(x)

Sohan Desilva  1 , Rafael Vazquez, Phillip E Stallworth, Thomas B Reddy, Joseph M Lehnes, Rui Guo, Hong Gan, Barry C Muffoletto, Steven G Greenbaum
Affiliations

Solid-State Nuclear Magnetic Resonance Studies of Electrochemically Discharged CF(x)

Sohan Desilva et al. J Power Sources. .

Abstract

Electrochemical studies of three types of CF(x) (F - Fiber based, C - Petroleum coke based, G - Graphite based) have demonstrated different electrochemical performances types in previous work, with fiber based CF(x) delivering superior performance over those based on petroleum coke and graphite. (13)C and (19)F MAS (Magic Angle Spinning) NMR techniques are employed to identify the atomic/molecular structural factors that might account for differences in electrochemical performance among the different types of CF(x). Small quantitative variations of covalent CF and LiF are noted as a function of discharge and sp(3) bonded carbons are detected in discharged F type of CF(x).

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Figures

Figure 1
Figure 1
19F MAS NMR of manually mixed LiF/CFx mixtures. The percentages given above refer to the fraction of LiF in the mixture. Asterisks denote spinning sidebands.
Figure 2
Figure 2
19F MAS NMR deconvolution of manually mixed LiF/CFx mixtures. Numbers are molar percentages which correspond to weight percentage values in Table 3.
Figure 3
Figure 3
Discharge voltage profiles of CFx F, CFx G, and CFx C cells under 6 month discharge rate.
Figure 4
Figure 4
CFx type effect on cell internal Rdc change vs. %DOD.
Figure 5
Figure 5
X-ray diffractograms of CFxC at three different DoD values.
Figure 6
Figure 6
SEM image of CFx C at 1.2% DOD and CFx C at 69.8% DOD.
Figure 7
Figure 7
19F MAS NMR Spectra of Greatbatch discharged nearly starting materials (F, C, G). Asterisks denote spinning sidebands.
Figure 8
Figure 8
19F MAS NMR Spectra of Greatbatch discharged F Series. Asterisks denote spinning sidebands.
Figure 9
Figure 9
19F MAS NMR deconvolution of Greatbatch discharged F, C and G series.
Figure 9
Figure 9
19F MAS NMR deconvolution of Greatbatch discharged F, C and G series.
Figure 10
Figure 10
13C MAS NMR Spectra of Greatbatch discharged F series.
Figure 11
Figure 11
13C MAS NMR deconvolution of Greatbatch discharged F, C and G Series. The spectral results of C at 99.4% DoD are not included due to the low SNR characteristics of that sample. Although CF intensity appears in the 19F spectra for the ~ 89% DoD samples, it does not show up distinctly in the 13C deconvolutions due to large overlap.
Figure 11
Figure 11
13C MAS NMR deconvolution of Greatbatch discharged F, C and G Series. The spectral results of C at 99.4% DoD are not included due to the low SNR characteristics of that sample. Although CF intensity appears in the 19F spectra for the ~ 89% DoD samples, it does not show up distinctly in the 13C deconvolutions due to large overlap.
Figure 12
Figure 12
7Li MAS NMR spectrum of Greatbatch 99.4% discharged F sample.
Figure 13
Figure 13
7Li MAS NMR T1 measurements of Greatbatch discharged batteries. The straight lines are guides to the eye.
Figure 14
Figure 14
19F MAS NMR T1 measurements of Greatbatch discharged batteries. The straight lines are guides to the eye.
Figure 15
Figure 15
19F MAS NMR Spectra of Hunter and Greatbatch discharged batteries. Asterisks denote spinning sidebands.
Figure 16
Figure 16
MAS NMR Spectra of Hunter discharged batteries for F, C and G series.
Figure 17
Figure 17
MAS NMR Spectra of Hunter 80% discharged F series.
Figure 18
Figure 18
13C MAS NMR Spectra of Hunter 46% discharged G series.
Figure 19
Figure 19
13C MAS NMR Spectra of Hunter 46% discharged C series.
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