Figure 3. XPS analysis of sulphur cathode.

(a) Discharge and charge of a Mg/S coin cell at 50 and 25 μA, respectively. XPS spectra were taken from coin cells at various stages of cycling. (b) HRES S 2p spectra of the cathode as-prepared (I), after first discharge (II) and after first charge (III) are compared with standard samples of S powder (top) and MgS powder (bottom). Note that the S 2p peaks contain both a 2p_3/2 and 2p_1/2 spin-orbit splitting state. The 2p_3/2 states, located at lower binding energies, were used for chemical state identification and are emphasized with filled symbols.