Exploring hybrid Mg2+/H+ reactions of C@MgMnSiO4 with boosted voltage in magnesium-ion batteries. (1st February 2022) - Rubio, Saul
Highlights: So-called hybrid concepts boosted the voltage of MgMnSiO4 cathode vs. metallic mg. The electrolyte is an electrochemically active part with transmitter of Mg 2+ /H + . Mg/Mg(TFSI)2 -DME+W04/MgMnSiO4 safe battery with 300 W h kg −1 energy density. Acceptable time-dependent stability of the electrolyte determined by 25 Mg NMR. Abstract: MgMnSiO4 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 MgMnSiO4, few works focused on these important issues. Therefore, to get cathode materials operating at high voltage and overcome the electrostatics problems of bivalent Mg 2+ 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@MgMnSiO4 cell occurs at 2.8 – 0.5 V (vs. Mg 2+ /Mg) with 160 mA h g -1 entailing 300 W h kg −1 at the materials' level. The results show that C@MgMnSiO4 could be a potential cathode material for high-energy magnesium secondary batteries in a bifunctional electrolytes, which not just utilized as a transmitter ... of Mg 2+, but also as a source of H + . We prove that the generated H + increases the isotropy around Mg 2+, changes in the Mn oxidation states, and modifies Mg/MgO interphase. Eventually, by assembling several Mg-ion full cells versus different anodes including Li4 Ti5 O12, activated carbon, and Mg0.5 MnSiO4, we recall the main challenges to overcome.