Exploration of bifunctional Vanadium-based Metal-Organic framework with double active centers for Potassium-ion batteries

Exploration of suitable electrode hosts with large open channels that can reversibly accommodate K + with large radius have been extensively investigated. Nevertheless, the reported inorganic counterparts were inevitably restricted by the difficulty of large K + diffusion capability in crystal structure and the huge volume change. Herein, we report a bifunctional vanadium-based metal–organic framework (MIL-47) with double active centers and larger lamellar spacing that could serve as both cathode and anode material , respectively by controlling the redox potential range in potassium-ion batteries. The results suggest that the stable K-storage mechanism is the reversible rearrangement of the conjugated carboxyl groups of organic terephthalic acid into enolate and the reversible redox activity of V ions , with the specific capacity of 272 mAh g −1 (0.01–1.5 V) and 50 mAh g −1 (1.5–3.8 V) at the current density of 10 mA g −1 for MIL-47 anode and MIL-47 cathode, respectively. The unsaturated functional group of MIL-47 and the intermediate bridged V atom not only provide multi-dimensional channels for electron and ion transport but also stabilize its crystal structure. Additionally, a symmetric full-cell in potassium-ion batteries based on MIL-47 was constructed successfully by avoiding the utilization of K metal with safety concerns. Our results provide new insight into structure design for next-generation large-scale energy storage applications.