Lithium Mobility in Graphite Anodes at Different States of Charge as Observed by NMR

Charge transfer and ion mobility in the electrodes determine battery performance among other factors. 7Li NMR spectra and relaxation of Li+ intercalated in graphite are investigated with regard to 7Li+ ion mobility in graphite anodes of technically used lithium-ion batteries, which have been formatted and charged. The state of charge ranged from 0% up to 100%. 7Li with a nuclear spin I = 3/2 is sensitive to quadrupolar interactions in addition to magnetic interactions. Temperature dependent 7Li NMR transverse relaxation and line width analysis were modeled to determine the correlation times and in consequence activation energies of the interaction fluctuations, which reflect the 7Li+ mobility in the anode’s graphite. Activation energies of the temperature dependent 7Li+ ion mobility were derived, assuming thermally activated motion.