Charge Transfer Mechanism into the Chevrel Phase Mo6S8 during Mg Intercalation

We re-examine the charge transfer mechanism in the Chevrel phase Mo6S8 upon Mg intercalation and deintercalation by the mean of X-ray photoemission spectroscopy. We highlighted a two-step reversible charge transfer process involving successively axial sulfurs and Mo-6 cluster redox center. In parallel, the Mg 2p and Mg KLL Auger transition evolution evidenced two insertion sites having different polarizations in accordance with previous studies. The nonconventional metal transition redox reaction, involved during Mg intercalation in Chevrel phase, might be at the origin of its excellent reversibility and intercalation kinetics.