Olivine-Type MgMn_0.5 Zn_0.5 SiO₄ Cathode for Mg-Batteries: Experimental Studies and First Principles Calculations

Magnesium driven reaction in olivine-type MgMn_0.5 Zn_0.5 SiO₄ structure is subject of study by experimental tests and density functional theory (DFT) calculations. The partial replacement of Mn in Oh sites by other divalent metal such as Zn to get MgMn_0.5 Zn_0.5 SiO₄ cathode is successfully developed by a simple sol-gel method. Its comparison with the well-known MgMnSiO₄ olivine-type structure with (Mg)_M1 (Mn)_M2 SiO₄ cations distribution serves as the basis of this study to understand the structure, and the magnesium extraction/insertion properties of novel olivine-type (Mg)_M1 (Mn_0.5 Zn_0.5 )_M2 SiO₄ composition. This work foresees to extend the study to others divalent elements in olivine-type (Mg)_M1 (Mn_0.5 M_0.5 )_M2 SiO₄ structure with M = Fe, Ca, Mg, and Ni by DFT calculations. The obtained results indicate that the energy density can be attuned between 520 and 440 W h kg^-1 based on two properties of atomic weight and redox chemistry. The presented results commit to open new paths toward development of cathodes materials for Mg batteries.