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. (C) 2022 Elsevier Inc. All rights reserved.