Toward High‐Performance Metal–Organic‐Framework‐Based Quasi‐Solid‐State Electrolytes: Tunable Structures and Electrochemical Properties

Abstract

Metal–organic frameworks (MOFs) have been reported as promising materials for electrochemical applications owing to their tunable porous structures and ion‐sieving capability. However, it remains challenging to rationally design MOF‐based electrolytes for high‐energy lithium batteries. In this work, by combining advanced characterization and modeling tools, a series of nanocrystalline MOFs is designed, and the effects of pore apertures and open metal sites on ion‐transport properties and electrochemical stability of MOF quasi‐solid‐state electrolytes are systematically studied. It isdemonstrated that MOFs with non‐redox‐active metal centers can lead to a much wider electrochemical stability window than those with redox‐active centers. Furthermore, the pore aperture of MOFs is found to be a dominating factor that determines the uptake of lithium salt and thus ionic conductivity. The ab initio molecular dynamics simulations further demonstrate that open metal sites of MOFs can facilitate the dissociation of lithium salt and immobilize anions via Lewis acid–base interaction, leading to good lithium‐ion mobility and high transference number. The MOF quasi‐solid‐state electrolyte demonstrates great battery performance with commercial LiFePO4 and LiCoO2 cathodes at 30 °C. This work provides new insights into structure–property relationships between tunable structure and electrochemical properties of MOFs that can lead to the development of advanced quasi‐solid‐state electrolytes for high‐energy lithium batteries.

Continuous Amorphous Metal–Organic Frameworks Layer Boosts the Performance of Metal Anodes

“…In contrast, the blocking nature of grain boundaries and the polymorphic traits in most MOFs induce sluggish ion migration . In addition, the more open metal sites in A-ZIF-8 can facilitate the dissociation of Zn salt and immobilize anions of Zn salt via Lewis acid–base interaction …”

Recent progress on metal–organic framework/polymer composite electrolytes for solid-state lithium metal batteries: ion transport regulation and interface engineering

“…110 ZIF-8 exhibited the capacity to absorb TFSI À owing to the larger pore size of ZIF-8 compared to that of TFSI À . Within the pores of ZIF- 112 They synthesized three distinct MOFs (Zn-MOF-74, HKUST-1, and MOF-5) Fig. 5 (a) Ion transport in the amorphous region of solid polymer electrolytes.…”

“…Dong et al conducted a systematic study on the effect of pore apertures and open metal sites of MOFs on Li-ion transport. 112 They synthesized three distinct MOFs (Zn-MOF-74, HKUST-1, and MOF-5) with varying pore apertures (Fig. 6c).…”

Electrospinning techniques for inorganic–organic composite electrolytes of all-solid-state lithium metal batteries: a brief review

“…136,137 On the one hand, the researchers designed the pore size of the porous MOF material to reduce the activation energy of the solid electrolyte, thereby increasing the ionic conductivity and electrochemical window. 138 On the other hand, an unsaturated metal site is constructed on the MOF material to weaken the interaction between Li + and lithium salt anions, so as to realize the rapid conduction of lithium ions. 139 However, the design of the framework for improving the conduction of lithium ions is still limited, and the ionic conductivity at room temperature is only 10 −4 –10 −6 S cm −1 .…”