7Li ‐  NMR  of Well‐Graphitized Vapor‐Grown Carbon Fibers and Natural Graphite Negative Electrodes of Rechargeable Lithium‐Ion Batteries

Abstract

Lithium intercalation of natural graphite and well‐graphitized vapor‐grown carbon fibers has been investigated by solid‐state 7normalLi‐NMR and by cyclic voltammetry. Chemical shift of 7normalLi in Li‐graphite intercalation compounds (Li‐GICs) of natural graphite occurs in two regions, >40 and <10 ppm. The former shifts were assigned to GICs with the in‐plane density of LiC6 and the latter shifts were assigned to those with the in‐plane density of LiC9 . Phase diagram of Li‐GICs during electrochemical intercalation is discussed. In comparison to natural graphite, 7normalLi in the vapor‐grown carbon fibers showed higher chemical shifts. The passivating film was also examined by 7normalLi‐NMR and structural change of the film during the first charge‐discharge cycle is indicated. Scanning electron microscopy imaging of the passivation film supports the 7normalLi NMR data during charge‐discharge. The swelling and shrinking of passivation is evident by scanning elecron microscope image and nuclear magnetic resonance data. The thickness of the solid electrolyte interface layer depends on the nature of salt, solvent, carbon origin, and current density. © 1999 The Electrochemical Society. All rights reserved.

Operando NMR and XRD study of chemically synthesized LiC oxidation in a dry room environment

“…(Figure 2a). The pure stage LiC 18 , which is thermodynamically stable, has a quadrupole frequency of 19 kHz, agreeing with 6 previous reports (6,14,15,20). Lastly, when an excess amount of Li (>25 wt.%) was added to the LiC 6 preparation, the Li metal resonance is observed at 270 ppm along with the inner and outer transitions from…”

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Application of Magnetic Resonance Techniques to the In Situ Characterization of Li-Ion Batteries: A Review

“…Overall, it was demonstrated that NMR is very sensitive to the structural changes within graphite associated with its lithiation and can serve as an external reference for determining an electrode's state of charge (SOC). These data are also in good agreement with previously reported ex situ NMR spectra [54].…”

Improved Electrochemical Performance of Modified Mesocarbon Microbeads for Lithium‐Ion Batteries Studied using Solid‐State Nuclear Magnetic Resonance Spectroscopy

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“… for a recent review). There are several solid‐state NMR studies on lithium intercalation in carbon matrices, for example graphite intercalation compounds (GICs) . The GICs, for different Li–C crystallographic environments, exhibit a range of Li chemical shielding and quadrupole interaction strengths during Li insertion/removal steps .…”