Anti-site mixing governs the electrochemical performances of olivine-type MgMnSiO4 cathodes for rechargeable magnesium batteries

Abstract

Rechargeable magnesium batteries are deemed as the next-generation secondary battery systems because of their high theoretical capacity and the terrestrial abundance of magnesium, which is used as the anode in these batteries. The cathode material is an important factor to improve the energy density of the magnesium batteries. In this study, we investigate olivine-type MgMnSiO₄ cathode materials owing to their high theoretical capacity (>300 mA h g⁻¹). The low-temperature synthesis of MgMnSiO₄ suppresses anti-site mixing between Mg and Mn, which drastically improves the charge–discharge capacities of the magnesium battery cathode. Our results show that the suppression of the degree of anti-site mixing between Mg and Mn enhances the diffusion of Mg²⁺ during magnesium (de)insertion, and therefore, it is a dominant factor that affects the electrochemical performance of olivine-type MgMnSiO₄.