Exploring hybrid Mg2+/H+ reactions of C@MgMnSiO4 with boosted voltage in magnesium-ion batteries.

• So-called hybrid concepts boosted the voltage of MgMnSiO 4 cathode vs. metallic mg. • The electrolyte is an electrochemically active part with transmitter of Mg2+/H+. • Mg/Mg(TFSI) 2 -DME+W04/MgMnSiO 4 safe battery with 300 W h kg−1 energy density. • Acceptable time-dependent stability of the electrolyte determined by 25Mg NMR. MgMnSiO 4 is a promising cathode material for rechargeable magnesium batteries, however, it still suffers from unsatisfactory electrochemical performances. Although the modulation of electrolyte formulation and cell configuration are critical to enhancing the electrochemical behavior of MgMnSiO 4 , few works focused on these important issues. Therefore, to get cathode materials operating at high voltage and overcome the electrostatics problems of bivalent Mg2+ ion, we adopt an unconventional approach of engaging water in a conventional nonaqueous solution such as 0.5 M Mg(TFSI) 2 in DME (dimethoxyethane). The electrochemical reaction of Mg/electrolyte/C@MgMnSiO 4 cell occurs at 2.8 – 0.5 V (vs. Mg2+/Mg) with 160 mA h g-1 entailing 300 W h kg−1 at the materials' level. The results show that C@MgMnSiO 4 could be a potential cathode material for high-energy magnesium secondary batteries in a bifunctional electrolytes, which not just utilized as a transmitter... of Mg2+, but also as a source of H+. We prove that the generated H+ increases the isotropy around Mg2+, changes in the Mn oxidation states, and modifies Mg/MgO interphase. Eventually, by assembling several Mg-ion full cells versus different anodes including Li 4 Ti 5 O 12 , activated carbon, and Mg 0.5 MnSiO 4 , we recall the main challenges to overcome. [ABSTRACT FROM AUTHOR]