Scientific Events

Where: virtual on Zoom (link follows) [more]

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 electrolytes^2,3 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]

Where: virtual on Zoom (link follows) [more]

Where: virtual on Zoom (link follows) [more]

(zoom lecture link comes shortly before) An ever-increasing demand for better batteries (with high voltage, high capacity, fast charging, and high safety) has set extraordinarily high standards for electrolyte materials, which are far beyond the realm of conventional nonaqueous electrolyte design based on 1 mol L^-1 (M) LiPF₆ and ethylene carbonate (EC). Generally, further increasing salt concentration over the conventional 1 M increases the viscosity and decreases the ionic conductivity, both of which are unfavorable for battery electrolytes in terms of reaction kinetics. However, various unusual functions have been recently discovered at high salt concentrations (over 3 M) (Fig. 1), including i) high reduction stability, ii) high oxidation stability, iii) fast electrode reactions, iv) high safety, v) wide liquidus temperature range, and vi) prevention of Al corrosion at high potentials, etc. As a result, concentrated nonaqueous and aqueous solutions are emerging as a new class of liquid electrolytes for advanced batteries. In this talk, I will introduce various unusual functions of concentrated electrolytes, which are not shared by conventional dilute electrolytes, discuss the mechanism from the viewpoint of their unique ion-solvent coordination structures, and present new electrolyte design strategies to advanced batteries. Reference 1. Y. Yamada et al., Nat. Energy, 4, 269 (2019); 2. Y. Yamada et al., J. Am. Chem. Soc., 136, 5039 (2014); 3. J. Wang and Y. Yamada et al., Nat. Commun., 7, 12032 (2016); 4. Y. Yamada et al., Nat. Energy, 1, 16129 (2016); 5. J. Wang and Y. Yamada et al., Nat. Energy, 3, 22 (2018); 6. Q. Zheng and Y. Yamada et al., Angew. Chem. Int. Ed., 58, 14202 (2019); 7. Q. Zheng and Y. Yamada et al., Nat. Energy, 5, 291 (2020); 8. J. Wang and Y. Yamada et al., Adv. Sci., 8, 2101646 (2021); 9. S. Ko and Y. Yamada et al., Joule, 5, 998 (2021). [more]

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(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]