Structure and Ionic Conductivity Properties of Metal-Organic Framework Composites

Lead Research Organisation: University of Cambridge
Department Name: Materials Science & Metallurgy

Abstract

As battery technology continues to improve and becomes cheaper, we rely more heavily on rechargeable battery technology in mobile electronics, healthcare and transport. For this purpose, lithium ion batteries are of interest due to the incredibly high volumetric and gravimetric energy densities compared to alternative battery technologies. Commercial lithium ion batteries rely on an organic liquid electrolyte which is often toxic, flammable and can lead to leakage if the battery is mistreated or disposed of incorrectly. One potential solution to this is the development of solid state electrolyte materials which can efficiently transport ions between the anode and cathode, but are also non-flammable, stable (both chemically and thermally) and compatible with the other battery materials.
This PhD project aims at understanding the structure and properties of a composite material formed from a sponge-like framework consisting of metal nodes and organic linker molecules, and an ionic liquid. These sponge-like frameworks are called Metal-Organic Frameworks and comprise a huge number (>70,000) of materials with variations in the chemical composition and structural arrangements. Guest molecules can be captured within the pores of such framework materials and in many cases, this can improve a particular property beyond that of the pure components. Incorporating a guest within the pores of the framework results in a pseudo solid-state material as the guest is trapped and there is an energy barrier which must be overcome in order to escape.
In particular, we are interested in the application of these composite materials as ionic conductors for solid electrolytes in batteries. The negligible volatility and non-flammability of the ionic liquids alleviate many of the safety concerns when compared with traditional organic electrolytes whilst maintaining high ionic conductivities required for operation. However, key questions still remain with regards to the nature of the interaction between the framework and the ionic liquid. To what extent do the electronic interactions disrupt the framework? Can this interaction be tuned to enhance specific properties such as ionic conductivity?
To answer these questions, novel composite materials will be synthesised to look at the effects of specific structural changes including: the size of the pores, the chemical composition of the framework, dynamic behaviour of the framework and the amount of pore filling to name a few. In order to confirm the successful synthesis of these novel composite materials, meticulous characterisation of the structure must be carried out via a multitude of techniques in order to prove that both the framework and ionic liquid are still intact and that the ionic liquid has been successfully incorporated into the pores of the framework. After this, it is then possible to measure the ionic conductivity properties of the composites and begin to understand trends between structural changes and the resulting properties of the material.

Publications

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Tuffnell JM (2019) Novel metal-organic framework materials: blends, liquids, glasses and crystal-glass composites. in Chemical communications (Cambridge, England)

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/R512461/1 01/10/2017 30/09/2021
1948666 Studentship EP/R512461/1 01/10/2017 30/09/2021 Joshua Tuffnell
 
Description Through this award we have developed new candidates for sodium ion battery materials and begun to understand their structure and properties. Whilst most research focuses on the electrodes of a battery, research into the electrolyte (the part of the battery which seperates the electrodes and shuttles the ions back and forth) has been lacking. In particular, this work represents a step towards safer and better batteries in the future, with the replacement of the traditional organic based liquid electrolytes (which can leak and are flammable) with a solid, non-flammable material.

During this work, it was discovered that these composite materials can also be used to produce novel glass materials which are unlike traditional inorganic glasses. This effect is not known in the pure components and we are currently exploring this further.
Exploitation Route The classes of materials being developed in this work may be used in next-generation lithium or sodium ion batteries.

Similarly, the glassy materials produced are of keen interest for companies looking at functional glasses.
Sectors Construction,Energy,Manufacturing, including Industrial Biotechology

URL https://www-nature-com.ezp.lib.cam.ac.uk/articles/s41598-020-60198-w??utm_source=other&utm_medium=other&utm_content=null&utm_campaign=JRCN_2_LW01_CN_SCIREP_article_paid_XMOL
 
Description Ion conduction in IL@MOF composites and their corresponding glasses 
Organisation Friedrich Schiller University Jena (FSU)
Country Germany 
Sector Academic/University 
PI Contribution Independent verification and analysis of electrochemical impedance spectroscopy data. Discussions on potential IL and MOF candidates. Experimental X-ray Pair Distribution Function (XPDF) analysis of the composite samples.
Collaborator Contribution Synthesis of the novel IL@MOF composites. Structural characterisation of the materials. Heat treatment of samples to form glasses.
Impact Publication - https://chemrxiv.org/articles/Sodium_Ion_Conductivity_in_Superionic_IL-Impregnated_Metal-Organic_Frameworks_Enhancing_Stability_Through_Structural_Disorder/8325668/1
Start Year 2019