Mg–Zn–Mn Oxide Systems for a Rechargeable Mg-Battery Cathode

Abstract

Mn-based spinel-oxide cathode materials are promising for achieving high-energy-density rechargeable Mg batteries (RMBs). However, Mg insertion into them often induces unfavorable phase transformation due to the poor stability of λ-MnO2, leading to capacity fading during cycling. Defect spinel ZnMnO3, which can be regarded as ZnO-stabilized λ-MnO2, is an outstanding exception that allows highly reversible Mg insertion/extraction. To further understand its phase stability, here we investigate wide-range compositions in Mg–Zn–Mn oxide systems and show that the stability of the spinel structure can be significantly improved by compositionally incorporating stable XO (X = Zn, Mg) with λ-MnO2. In particular, (i) the equimolar mixing of XO and MnO2 is critical to obtaining a single-phase cubic spinel structure and (ii) a higher Zn/Mg ratio is effective for preventing the formation of an irreversible rock salt phase to decrease the overpotential during discharge/charge cycling. Consequently, Zn-rich Mg–Zn–Mn oxides with the cubic spinel structure delivered as high as 120 mAh/g discharge capacities repeatedly at an elevated temperature of 150 °C. This work provides a fundamental understanding of the phase stability of Mg–Zn–Mn oxide materials and insights into designing high-performance cathode materials for RMBs.

Research and Development of Novel Secondary Batteries in Japan

“…While promising, these approaches suffer from several fundamental and technical problems. The VSI reports significant achievements for the Mg-metal batteries in developing new electrolytes and electrode active materials through collaboration between material scientists and computational scientists in Japan. − The VSI describes extensive studies on the elucidating mechanisms of oxygen electrode reaction, developing electrode materials and solvents, and establishing cell design strategies for the practical implementation of Li–O 2 batteries. − …”