MOF derived TiO2 with reversible magnesium pseudocapacitance for ultralong-life Mg metal batteries

Magnesium metal batteries have attracted much attention due to the good safety, low cost of magnesium and high theoretical volumetric capacity. However, developing magnesium metal batteries is restricted by large polarization and sluggish kinetics during Mg insertion/deinsertion process. Herein, TiO2 ultrafine nanocrystals derived from Ti-metal–organic-framework (Ti-MOF) are applied as the cathodes in magnesium metal batteries. Remarkably, an ultralong life of the Mg(s) || TiO2 battery can be obtained during cycling (capacity retention of 75% after 1000 cycles). On the basis of in-situ XRD characterization and cyclic voltammetry analysis, a high pseudocapacitive performance is found, which results in the high kinetics. Moreover, according to Arrhenius behavior, carbon skeleton in TiO2 cathode can facilitate ion migration and Faraday reaction, thus improving the magnesium storage performance.