Synthesis of K0.25V2O5 hierarchical microspheres as a high-rate and long-cycle cathode for lithium metal batteries

Hierarchical potassium vanadate (K 0.25 V 2 O 5 ) microspheres are synthesized via a facile hydrothermal reaction followed by annealing process. The K 0.25 V 2 O 5 microspheres with an average diameter of ∼1–2 μm, are composed of interconnected nanosheets , exhibiting the hierarchical structures. This novel architecture exhibits excellent lithium storage performance, including a discharge specific capacity of 249 mA h g −1 at the current density of 100 mA g −1 , good cyclic stability up to 500 cycles and a satisfactory rate capacity of 161.2 mA h g −1 at 1.5 A g −1 . The good performance of K 0.25 V 2 O 5 microspheres may be ascribed to the hierarchical spherical morphology and its stable structure. Importantly, a quantitative analysis method was first used to calculate the contribution of capacitive charge storage for potassium vanadates. The dominant capacitive charge storage mechanism enables the high rate capability of K 0.25 V 2 O 5 microspheres. However, the volumetric energy density of this material is tiny (897 Wh/L), which limits the practical application.