7Li-nuclear magnetic resonance observations of lithium insertion into coke carbon modified with mesophase-pitch

Lithium intercalation into coke carbon modified with mesophase-pitch and heat-treated at 800, 1000, and 3000°C was observed using solid-state 7Li-nuclear magnetic resonance (7Li-NMR) spectroscopy. It was found that the fully lithiated state charged to 0 V in the modified coke heat-treated at 3000°C showed a peak at about 45 ppm; on the other hand, two peaks appeared at about 45 and 16–17 ppm in the modified coke heat-treated below 1000°C. The peak appearing at 45 ppm indicated that Li-GIC is present in the first stage, and the peak at about 16–17 ppm indicated that the lithium stored in the modified part has an ionic character greater than in the coke part and is not a lithium cluster. The lithiated states charged to 0.1 and 0.2 V and discharged to 0.1, 0.2 and 1.5 V from the charged state (0 V) are also described.