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

• Low-cost MgFe x Mn 2-x O 4 nanoparticles were prepared via a facile so-gel route. • MgFe 1.33 Mn 0.67 O 4 exhibited good rate ability and cycling stability. • MgFe 1.33 Mn 0.67 O 4 displays Mg-ions diffusion coefficients of 2.55 × 10−7 cm2 s−1. 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 MgFe x Mn 2-x O 4 (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 MgFe 1.33 Mn 0.67 O 4 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 MgFe 1.33 Mn 0.67 O 4 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. [ABSTRACT FROM AUTHOR]