UiO-66 Metal–Organic Framework as an Anode for a Potassium-Ion Battery: Quantum Mechanical Analysis

Abstract

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.

Potassium Storage Performance of UiO-66 Derivatives from First Principles Calculations

“…The optimized structures of UiO-66-Ti, UiO-66-Hf, and UiO-66-L are shown in Figures S1, S2, and . In UiO-66-M, the optimized supercell volume of UiO-66-Hf is 4505.6 Å 3 , which is close to that of UiO-66 (4559.8 Å 3 ) reported by Tang et al, while the volume of UiO-66-Ti supercell is 4204.5 Å 3 , smaller than that of UiO-66-Hf. The bond lengths of M–O in the M 6 O 4 (OH) 4 node (M = Ti, Zr, or Hf) are shown in Table .…”

“…In a UiO-66-Hf supercell, when all sites are occupied by K (Figure ), the volume expansion rate is 14.6%, slightly smaller than that of UiO-66 (16.2%). The maximum capacity of UiO-66-Hf is 490.3 mAh/g, which is smaller than that of UiO-66 (644 mAh/g), because the atomic mass of Hf is much larger than that of Zr. For the UiO-66-Hf with the maximum capacity, the re-optimization shows that the structure can be fully recovered after removing all K, which verifies the stability of UiO-66-Hf during charging.…”

“…Our previous research , has found that UiO-66 can be used as the anode of a battery and has unique advantages applied to KIBs compared with LIBs. In this work, we used the first principle calculations to study whether UiO-66 derivatives as electrode materials have better potassium storage performance from the following aspects: volume expansion, binding energies, electronic structures, and K-ion migration energy barriers, including the replacement of the central metal Zr with Ti and Hf, and the introduction of functional groups (−NH 2 , −NO 2 , −Br, −Cl, −OH, −SH, and −CH 3 ) in organic linkers.…”

Conductive Co-based metal organic framework nanostructures for excellent potassium- and lithium-ion storage: kinetics and mechanism studies

“…Among those materials, metal organic frameworks (MOFs) are promising anodes for potassium storage, thanks to their merits of low cost, low density, multiple redox sites, and abundant porosity. 12,[27][28][29][30] Taking advantage of the sufficient inner space of MOFs, Li et al demonstrated that a novel rectangular-shaped [C 7 H 3 KNO 4 ] n MOF can be used as the anode for efficient potassium storage, 26 which maintained a specic capacity of 123 mA h g À1 aer 150 cycles at a current density of 50 mA g À1 . The abundant N-K/O-K coordination bonds through the MOF pores are responsible for the excellent electrochemical performance.…”

A review on carbon nanomaterials for K‐ion battery anode: Progress and perspectives

“…In recent years, MOFs are being received huge research interest due to their distinct physicochemical properties, tunable structures, and superior surface areas integrated with excellent application-oriented morphologies. [147][148][149][150][151][152] A wide variety of MOFs-derived composites with various structures and morphologies have already been used and proved as efficient electrode candidates for battery systems (ie, LIBs, SIBs, etc). At present, they possess greater potential for effective potassium storage, hence mitigating the bottlenecks encountered by the traditional KIBs electrode materials.…”