MIL-53 Metal–Organic Framework as a Flexible Cathode for Lithium-Oxygen Batteries

Abstract

Li-air batteries possess higher specific energies than the current Li-ion batteries. Major drawbacks of the air cathode include the sluggish kinetics of the oxygen reduction (OER), high overpotentials and pore clogging during discharge processes. Metal–Organic Frameworks (MOFs) appear as promising materials because of their high surface areas, tailorable pore sizes and catalytic centers. In this work, we propose to use, for the first time, aluminum terephthalate (well known as MIL-53) as a flexible air cathode for Li-O2 batteries. This compound was synthetized through hydrothermal and microwave-assisted routes, leading to different particle sizes with different aspect ratios. The electrochemical properties of both materials seem to be equivalent. Several behaviors are observed depending on the initial value of the first discharge capacity. When the first discharge capacity is higher, no OER occurs, leading to a fast decrease in the capacity during cycling. The nature and the morphology of the discharge products are investigated using ex situ analysis (XRD, SEM and XPS). For both MIL-53 materials, lithium peroxide Li2O2 is found as the main discharge product. A morphological evolution of the Li2O2 particles occurs upon cycling (stacked thin plates, toroids or pseudo-spheres).

Metal–Organic Frameworks‐Based Cathode Materials for Energy Storage Applications: A Review

“…MOF offers several benefits, including many active sites, ease of fabrication, large pore sizes and shapes, highly organized crystalline structure with adjustable hydrophobic/hydrophilic balance, controllable chemical composition, and modifiable functional groups. [10,48,49] These characteristics are very valuable in photo-, electro-, and organocatalysis applications. [50,51] In the hunt for high-performance electrode materials for metal-ion [40] Copyright 2015, American Chemical Society.…”

“…[ 85 ] Aluminum terephthalate (MIL‐53) was commonly utilized as a flexible air cathode in Li–O 2 batteries. [ 10 ] MIL‐53‐based MOFs with varying aspect ratios and particle sizes may be produced using hydrothermal and microwave‐assisted techniques. MIL‐53 MOF also emits the major byproduct of Li 2 O 2 , which has tiny toroidal crystals or plate‐like structures at first and toroidal or sphere‐like shapes after ten discharge cycles.…”

“…[ 9 ] MOFs may also provide different internal surfaces with distinct accessible metal sites, various structural topologies, and chemical variety, such as the usage of acidic and basic functional groups and tunable wettability (hydrophilicity and hydrophobicity). [ 10 ]…”

“…acidic and basic functional groups and tunable wettability (hydrophilicity and hydrophobicity). [10] MOF-based materials have been widely used as an electrocatalyst for energy conversion and storage applications in recent years. [5,9,[11][12][13] In contrast, the poor electrical conductivity, electrochemical capacity, stability of MOF, irreversible structural deterioration during charge/discharge cycles, and low tap density restrict its usage as an electrode in battery applications.…”