Sub-nanometer confinement enables facile condensation of gas electrolyte for low-temperature batteries

Abstract

Confining molecules in the nanoscale environment can lead to dramatic changes of their physical and chemical properties, which opens possibilities for new applications. There is a growing interest in liquefied gas electrolytes for electrochemical devices operating at low temperatures due to their low melting point. However, their high vapor pressure still poses potential safety concerns for practical usages. Herein, we report facile capillary condensation of gas electrolyte by strong confinement in sub-nanometer pores of metal-organic framework (MOF). By designing MOF-polymer membranes (MPMs) that present dense and continuous micropore (~0.8 nm) networks, we show significant uptake of hydrofluorocarbon molecules in MOF pores at pressure lower than the bulk counterpart. This unique property enables lithium/fluorinated graphite batteries with MPM-based electrolytes to deliver a significantly higher capacity than those with commercial separator membranes (~500 mAh g−1 vs. <0.03 mAh g−1) at −40 °C under reduced pressure of the electrolyte.

Oxygen‐Rich Cobalt–Nitrogen–Carbon Porous Nanosheets for Bifunctional Oxygen Electrocatalysis

“…Such an ultrathin 2D template‐induced method is a straightforward manner to prepare MOF‐based composite nanosheets. [ 45,46 ] The evolution of morphology and structure from the CoO nanosheet template to the resulting O–Co–N/C nanosheets were investigated by transmission electron microscopy (TEM) and powder X‐ray diffraction (XRD). First, the ultrathin CoO template was prepared as previously reported [ 47 ] and its crystalline structure was confirmed by the XRD pattern, in which the dominant peaks located at 31.2° and 57.4° were assigned to the (100) and (110) planes of CoO, [ 48 ] respectively (Figure S1, Supporting Information).…”

Metal–Organic Framework-Based Hierarchically Porous Materials: Synthesis and Applications

“…Schematic showing the mechanism of nanoconfinement effects for lowering the equilibrium pressure of liquefied gas and the implementation of MPM-based LGE for Li-battery cells. Reproduced with permission from ref . Copyright 2021 Springer Nature.…”

“…419 To apply the nanoconfinement effect (capillary condensation) in the battery chemistries for shifting the critical properties of gas-based electrolytes, Cai et al developed a novel "brick-and-mortar"-like strategy to construct mechanically flexible MOF−polymer membranes (MPMs) by using the microporous MOFs as the porous "brick" and polymer binder as the mechanically flexible "motor" (Figure 32). 417 However, conventional MOF-based membranes are not suitable for desired ion migration in LGE under reduced pressure, due to the presence of numerous gaps between the binders and MOF particles which inevitably degrade the continuous liquefied gas flux required for Li + migration throughout the entire membrane. To produce a dense and continuous microporous network throughout the nanoscale MOFs assembled macroscopic membranes, the MOFs was elaborately in situ grown on a 2D GO nanosheet, in which a large cross-sectional area of MOF nanosheet enlarge the contact of MOF assembled units.…”

Large-Scale Production of Hierarchically Porous Metal–Organic Frameworks by a Reflux-Assisted Post-Synthetic Ligand Substitution Strategy

“…Therefore, we propose that the coordinated acetate was removed by the (DMF + aqueous HCl) activation, which causes a chlorine containing MOF (Figure S19). − …”