Scientific Events

Host: Prof. Dierk Raabe

Processing and applications of two-dimensional nanosheet inks

(zoom lecture link comes shortly before)Liquid phase exfoliation has been proved to be a cheap, scalable method for the mass production of 2D sheets. This talk will first discuss the galaxy of existent layered materials, with emphasis on synthesis, liquid-phase exfoliation, and characterization, focussing on some key applications recently developed in our laboratories, ranging from energy storage to printed electronics. We will for example discuss how two-dimensional Ti3C2 (MXene) can be formulated in aqueous and organic viscous inks for extrusion printing and inkjet printing, respectively, and demonstrate direct MXene printing on various substrates. The additive- and binary solvent-free MXene inks do not show coffee ring effect, enabling high-resolution printing without substrate pre-treatment. The resulting all-MXene printed micro-supercapacitors showcase excellent charge storage performance, including areal capacitance up to 43 mF/cm2 and volumetric capacitance up to 562 F/cm3 in protic gel electrolyte, coupled with long lifetime and good flexibility. We also show examples of all-inkjet-printed MXene arrays for ohmic resistors. The versatile direct-ink-printing technique highlights the promise of MXene functional inks for scalable fabrication of easy-to-integrate components of printable electronics. We will also discuss how MXenes can be used as a conductive binder for silicon electrodes produced by a simple and scalable slurry-casting technique without the need of any other additives. The nanosheets form a continuous metallic network, enable fast charge transport and provide good mechanical reinforcement for the thick electrode (up to 450 µm). Consequently, record high areal capacity anodes (up to 23.3 mAh cm−2) can be demonstrated. EMI shielding applications will also be discussed. [more]

Translating insight from the catalysis of green hydrogen and ammonia production to batteries and vice versa

Electrochemistry will play a pivotal role in our transition away from fossil fuels to a net zero society. While batteries and fuel cells are set to decarbonise transportation, electrolysers can enable the sustainable synthesis of our most coveted chemicals, such as H2 and NH3. It turns out that some of the reactions that we aim to accelerate in water electrolysis, such as H2 evolution, are exactly the reactions that we wish to inhibit in Li ion batteries and during N2 reduction. To that end, in our group we translate techniques and insight from battery science to electrosynthesis and vice versa. I will present our mechanistic studies on the electrocatalysis of (i) O2 evolution for water electrolysis on iridium based and nickel based oxides1 and (ii) N2 reduction to NH3 on Li-based electrodes in organic electrolytes2,3 and (iii) parasitic gas evolution in Li ion batteries. Our studies incorporate electrochemical measurements, electrochemical mass spectrometry, operando optical spectroscopy, secondary ion mass spectrometry, x-ray photoelectron spectroscopy and density functional theory; using the combination of these techniques, we build a holistic picture of the factors controlling these technologically critical reactions. 1 Francas, L., Corby, S., Selim, S., Lee, D., Mesa, C., Godin, R., Pastor, E., Stephens, I. E. L., Choi, K.-S. & Durrant, J. Nat. Commun. 10, 5208, (2019). 2 Andersen, S. Z., Colic, V., Yang, S., Schwalbe, J. A., Nielander, A. C., McEnaney, J. M., Enemark-Rasmussen, K., Baker, J. G., Singh, A. R., Rohr, B. A., Statt, M. J., Blair, S. J., Mezzavilla, S., Kibsgaard, J., Vesborg, P. C. K., Cargnello, M., Bent, S. F., Jaramillo, T. F., Stephens, I. E. L., Norskov, J. K. & Chorkendorff, I. Nature 570, 504, (2019). 3 Westhead, O., Jervis, R. & Stephens, I. E. L. Science 372, 1149, (2021). [more]
(zoom lecture link comes shortly before) Current state-of-the-art lithium-ion batteries (LIBs) contain electrode materials with mostly layered structures that serve as host lattices for the reversible, electrochemical intercalation of lithium ions. The kinetics of these intercalation reactions are typically limited by the solid-state diffusion of the ions inside the lattice. Volumetric changes that accompany the (de-)insertion of ions further lead to degradation of the electrode materials. These factors contribute to the limited power and lifetime of LIBs. While some of these limitations can be mitigated by nanostructuring of the electrode material, there is a large interest in finding structural motifs that allow for intrinsically fast ion diffusion with reduced host lattice deformation, even in bulk-sized particles. In this presentation, I will highlight how interlayer properties, such as interlayer distance and interlayer chemistry, affect electrochemical ion intercalation processes in layered host materials. It is demonstrated that the presence of interlayer structural molecules can increase the accessibility of intercalating ions to the interlayer space and affect their transport properties. Increased interlayer spacing and reduced deformation during ion intercalation can lead to a change from diffusion-limited to non-diffusion limited (or pseudocapacitive) charge storage behavior, enabling favorable charge storage kinetics. The talk will give an overview of my research group’s efforts to synthesize interlayer-functionalized layered and two-dimensional materials with tailored interlayer properties towards high power intercalation electrodes and highlight the challenges regarding both materials synthesis and characterization. [more]
(zoom lecture link comes shortly before)The improvement of current and new-generation battery technologies requires the discovery of new electrode materials and the continuous development of existing ones. These are complicated processes where materials design (often aided by computational techniques), materials synthesis and characterization play an equally important role. This lecture will span different alkali-ion battery technologies and different materials chemistries (layered, polyanionic) to demonstrate the importance of an all-around approach to materials discovery and development. Particular attention will be given to thorough structural characterization techniques, using complementary probes, and to their implementation in situ, i.e. in real time during synthesis or during battery charge/discharge. [more]

Recent progress in micromechanics-based approach of ductile fracture in metals

The mechanisms of nucleation, growth and coalescence of voids leading to the fracture of ductile metals have been investigated for more than 50 years and modelled with increasing degrees of complexity. Nevertheless, we are still far today from a fully predictive approach, in particular in the context of the new generations of metallic alloys with advanced microstructures. Challenges remain on several fronts, for instance: the description of the statistical aspects of void nucleation, the transition into shear dominated failure mode, the physical meaning of the internal lengths entering non local models, the treatment of competing fracture mechanisms (e.g. intergranular versus ductile), etc. In this talk, recent progress made regarding the characterization and modelling of ductile fracture in Al alloys and in steel will be presented, insisting on void nucleation aspects. Topic: 9th MMELO Lecture - Prof. Thomas Pardoen Time: Febr 17, 2022 15:00h CET [more]

Materials science meets battery chemistry: Approaches to better batteries

Metal fuels for zero-carbon heat and power

In order to address climate change, we must transition to a low-carbon economy. Many clean primary energy sources, such as solar panels and wind turbines, are being deployed and promise an abundant supply of clean electricity in the near future. The key question becomes how to store, transport and trade this clean energy in a manner that is as convenient as fossil fuels. The Alternative Fuels Laboratory (AFL) at McGill University is actively researching the use of recyclable metal fuels as a key enabling technology for a low-carbon society. Metal fuels, reduced using clean primary energy, have the highest energy density of any chemical fuel and are stable solids, simplifying trade and transport. The chemical energy stored in the metal fuels can be converted to useful thermal or motive power through two main routes: the Dry Cycle, where metal powders/sprays are burned with air, or the Wet Cycle, where metal powders are reacted with water to produce hydrogen and heat as an intermediate step before using the hydrogen as a fuel for various power systems. This talk will overview the concept of metal fuels and the various power system options. It will also touch on the combustion and reaction physics of metal fuels and the propagation of metal flames. [more]
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