Self-assembled vanadium oxide nanoflowers as a high-efficiency cathode material for magnesium-ion batteries

Magnesium-ion batteries (MIBs) are expected to be an alternative energy storage system for lithium-ion batteries in the future due to their high theoretical capacity and high safety. However, the current MIB cathode materials suffer from structural instability and poor cycle performance during Mg ions intercalation/deintercalation, which limit the further development of MIBs. Therefore, exploring high-performance cathode materials has become the focus of current MIB research. Currently, vanadium oxides are considered as a promising class of advanced MIB cathode materials. Among them, V5O12·6H2O has high theoretical capacity and stable crystal structure, making it a potential cathode material for MIBs. Herein, we employ a facile one-step solvothermal method for the controllable synthesis of V5O12·6H2O nanoflowers formed by self-assembly of nanosheets, and investigate them as a cathode material for MIBs for the first time. The structural water contained in the interlayer of V5O12·6H2O can improve the stability of the crystal structure and create more active sites for Mg2+ storage. In addition, the unique nanoflower morphology can enhance the contact between the electrode material and the electrolyte, thereby improving the diffusion kinetics of Mg2+. The synthesized V5O12·6H2O nanoflowers exhibit encouraging electrochemical properties, including high specific capacity (234.3 mAh g−1 at 10 mA g−1), satisfactory rate performance (53.2 mAh g−1 at a high current density of 500 mA g−1), and excellent cycling stability (0.017% capacity loss per cycle during 1500 cycles). Our findings highlight an efficient approach to exploit high-performance cathode materials for MIBs with excellent structural stability and cycling capability.