High rate performance of aqueous magnesium-ion batteries based on the δ-MnO2@carbon molecular sieves composite as the cathode and nanowire VO2 as the anode.

The need for safe, cost-effective aqueous magnesium ion batteries has led to high electrochemical performance designs of materials and structures to meet strict requirements. A composite of manganese dioxide and carbon molecular sieves (δ -MnO 2 @CMS) with a core-shell structure is used as the cathode in the aqueous magnesium ion battery, which not only solves the inherent deficiencies of low conductivity from manganese dioxide but also maximizes its specific capacities via a hierarchical structure. In addition, the anode material, nanowire VO 2 (formed via a solvothermal reaction) is rarely investigated in this system. Interestingly, this material can form new electrodes with more stable structures after the first charged process and avoids the formation of MgO, thereby providing insertion/extraction of magnesium ions into/from the host anode material. An aqueous rechargeable magnesium ion battery can be successfully assembled using the two electrodes designed above. This device shows high rate properties and delivers reversible capacities of 112.2, 94.6, 78.7, 69.5, and 59.1 mAh g−1 at current densities of 50, 100, 200, 300, and 500 mA g−1. Image 1 • δ -MnO 2 @CMS with core-shell structure is synthesized by hydrothermal method. • The nanowire VO 2 as anode is obtained by simple one-step hydrothermal process. • The Mg2+ insertion/deinsertion mechanism of two electrodes is explored. • Assembled aqueous magnesium-ion battery exhibits excellent rate property. [ABSTRACT FROM AUTHOR]