Uio-66 metal-organic framework as an anode for a potassium-ion battery: Quantum mechanical analysis

The natural abundance of potassium in the earth's crust is 1000 times higher than that of lithium, so energy technologies built on potassium are more sustainable. Potassiumion batteries have attracted considerable attention because of their relatively low cost and high operating potential, but questions remain about the best anode material for such batteries. Here, we report first-principles computations based on density functional theory to investigate the performance of the UiO-66 metal- organic framework as an anode material for potassium-ion batteries; the goal is to provide a fundamental understanding of metal-organic framework (MOF)-based electrodes to guide the design and development of high-performance potassium-ion batteries. Our study includes the stability and electronic properties of potassiated structures and the mechanisms of potassium intercalation and diffusion in the framework. The results indicate that UiO-66 has a maximum specific capacity of 644 mAh/g as the anode of a potassium-ion battery. During potassiation, we observe charge transfer from potassium to carbon or oxygen of UiO-66 near the intercalated K. During K diffusion, the K migrates along the UiO-66 framework with a maximal migration energy barrier of 0.377 eV in the optimal pathway, which is much lower than the barriers for Li and Na diffusion in UiO-66. The diffusion coefficient of K in the anode is several orders of magnitude larger than those of Li and Na. This favors potassium ions over lithium ions or sodium ions when UiO-66 is the anode.