What About Manganese? Toward Rocking Chair Aqueous Mn-Ion Batteries

The emerging interest in aqueous rechargeable batteries has led to significant progress in the development of next-generation electrolytes and electrode materials enabling reversible and stable insertion of various multivalent ions into the electrode's bulk. Yet, despite its abundance, high salt solubility, and small ionic radius, the use of manganese ions for energy storage purposes has not received sufficient attention. Herein, we present the use of Mo6S8 (Chevrel phase) as an anode for Mn2+ insertion. By careful optimization of the electrolyte solution, high-capacity values exceeding 90 mAh/g and long-term stability (more than 1500 cycles) have been obtained. Based on in situ XRD analysis, the charging mechanism and the associated structural changes occurring during Mn2+ insertion have been carefully studied. Finally, we demonstrate for the first time a rocking chair aqueous Mn-ion battery comprising a Chevrel anode and NiHCF cathode.