High‐Energy‐Density Aqueous Magnesium‐Ion Battery Based on a Carbon‐Coated FeVO4 Anode and a Mg‐OMS‐1 Cathode

Porous FeVO4 is prepared by hydrothermal method and further modified by coating with carbon to obtain FeVO4 /C with a hierarchical pore structure. FeVO4 /C is used as an anodic electrode in aqueous rechargeable magnesium-ion batteries. The FeVO4 /C material not only has improved electrical conductivity as a result of the carbon coating layer, but also has an increased specific surface area as a result of the hierarchical pore structure, which is beneficial for magnesium-ion insertion/deinsertion. Therefore, an aqueous rechargeable magnesium-ion full battery is successfully constructed with FeVO4 /C as the anode, Mg-OMS-1 (OMS=octahedral molecular sieves) as the cathode, and 1.0 mol L-1 MgSO4 as the electrolyte. The discharge capacity of the Mg-OMS-1//FeVO4 /C aqueous battery is 58.9 mAh g-1 at a current density of 100 mA g-1 ; this value is obtained by calculating the total mass of two electrodes and the capacity retention rate of this device is 97.7 % after 100 cycles, with almost 100 % coulombic efficiency, which indicates that the system has a good electrochemical reversibility. Additionally, this system can achieve a high energy density of 70.4 Wh kg-1 , which provides powerful evidence that an aqueous magnesium-ion battery is possible.