Correlation between x-ray absorption and chemical potential measurements in lithium intercalated carbons

Using synchrotron radiation we measured the x-ray absorption (XAS) near the C₁ₛ edge for powdered graphite, boron substituted graphite, and a disordered graphitic carbon. The chemical potential of Li intercalated into the same carbons has also been measured as a function of x in Liₓ{C}₆$. When Li is intercalated, the 2s electron is transferred to the C host, filling the same levels as probed by XAS. In XAS, final-state energies contain a contribution from the electron--core-hole interaction which mimics the situation in Li intercalation where Li⁺ interacts with conduction electrons. We show that XAS results correlate well with chemical potential measurements of intercalated Li made on the same materials.