This applications note demonstrates the use of both conventional (Al Kα) and higher photon energy (Ag Lα) excited X-ray Photoelectron Spectroscopy (XPS) to characterise the solid electrolyte interphase layer formed on a graphite anode during charge/discharge cycles.  Samples were prepared in a glove box at the manufacturing site and transported to the XPS analysis laboratory using an air sensitive sample transport accessory.