Low-cost MgFexMn2-xO4 cathode materials for high-performance aqueous rechargeable magnesium-ion batteries

Aqueous Mg-ion batteries attract lots of attention due to its high safety, low cost and potential application for large scale energy storage system. Although spinel-type metal oxides display their capable Mg ions storage behavior, low diffusion ability extremely hinder their practical application. Herein, low-cost MgFexMn2-xO4 (x = 0.67, 1, 1.33, 1.6) nanomaterials are prepared by a facile sol-gel method. Their electrochemical performance is affected by molar ratio of iron to manganese. The optimized MgFe1.33 Mn0.67O4 exhibits excellent electrochemical cycling performance and rate capability. Even at high current density of 1000 mA g( -1) , a specific capacity 88.3 mAh g(-1) is obtained after 1000 charge-discharge cycles. The stable structure of MgFe1.33Mn0.67O4 promise a cycling stability. Moreover, hydrogen evolution and oxygen evolution of the electrode material during charging-discharging process can be effectively suppressed by regulating the atom ratio of iron to manganese. In addition, it presents a high magnesium diffusion coefficient at two oxidation peaks, leading to a good rate ability.