High‐Energy‐Density Aqueous Magnesium‐Ion Battery Based on a Carbon‐Coated FeVO 4 Anode and a Mg‐OMS‐1 Cathode

Porous FeVO 4 is prepared by hydrothermal method and further modified by coating with carbon to obtain FeVO 4 /C with a hierarchical pore structure. FeVO 4 /C is used as an anodic electrode in aqueous rechargeable magnesium‐ion batteries. The FeVO 4 /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 FeVO 4 /C as the anode, Mg‐OMS‐1 (OMS=octahedral molecular sieves) as the cathode, and 1.0 mol L −1 MgSO 4 as the electrolyte. The discharge capacity of the Mg‐OMS‐1//FeVO 4 /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.