@article{25130, keywords = {Sputtering, Lithium, Secondary cells, Chromatography, Electrochemical electrodes, Electrochemical impedance spectroscopy, Fourier transform spectra, Graphite, Infrared spectra, Mass spectra, Raman spectra, Scanning electron microscopy, Surface structure}, author = {Laurence J Hardwick and Marek Marcinek and Leanne Beer and John B Kerr and Robert Kostecki}, title = {An Investigation of the Effect of Graphite Degradation on Irreversible Capacity in Lithium-Ion Cells}, abstract = {

The effect of surface structural damage on graphitic anodes, commonly observed in tested Li-ion cells, was investigated. Similar surface structural disorder was artificially induced in Mag-10 synthetic graphite anodes using argon-ion sputtering. Raman microscopy, scanning electron microscopy, and Brunauer–Emmett–Teller measurements confirmed that Ar-ion sputtered Mag-10 electrodes display a similar degree of surface degradation as the anodes from tested Li-ion cells. Artificially modified Mag-10 anodes showed double the irreversible charge capacity during the first formation cycle compared to fresh unaltered anodes. Impedance spectroscopy and Fourier transform infrared spectroscopy on surface-modified graphite anodes indicated the formation of a thicker and slightly more resistive solid electrolyte interphase (SEI) layer. Gas chromatography/mass spectroscopy analysis of solvent extracts from the electrodes detected the presence of new compounds with Mw on the order of 1600gmol−1 for the surface-modified electrode with no evidence of elevated Mw species for the unmodified electrode. The structural disorder induced in the graphite during long-term cycling may be responsible for the slow and continuous SEI layer reformation, and consequently, the loss of reversible capacity due to the shift of lithium inventory in cycled Li-ion cells.

}, year = {2008}, journal = {Electrochemical Society}, volume = {155}, pages = {A442-A447}, doi = {10.1149/1.2903882 }, language = {eng}, }