• Energy Research

Self-assembling, nanophase-separated multi-block copoly(arylene sulfone)s, selectively swelled with ethylene carbonate, provide excellent single-ion conductivity and cycling stability for high-energy lithium/Li[Ni1/3Co1/3Mn1/3]O2 batteries.

Correlative neutron and X-ray imaging unravels the causes of localized defects in Li-ion batteries containing a silicon-graphite based anode.

Abstract Design and implementation of advanced membrane formulations for selective transport of ions and molecular species are critical for creating the next generations of fuel cells and separation devices. It is necessary to understand the detailed transport mechanisms over time- and length-scales relevant to the device operation, both in laboratory models and in working systems under realistic operational conditions. Neutron scattering techniques including quasi-elastic neutron scattering, reflectivity and imaging are implemented at beamline stations at reactor and spallation source facilities worldwide. With the advent of new and improved instrument design, detector methodology, source characteristics and data analysis protocols, these neutron scattering techniques are emerging as a primary tool for research to design, evaluate and implement advanced membrane technologies for fuel cell and separation devices. Here we describe these techniques and their development and implementation at the ILL reactor source (Institut Laue-Langevin, Grenoble, France) and ISIS Neutron and Muon Spallation source (Harwell Science and Technology Campus, UK) as examples. We also mention similar developments under way at other facilities worldwide, and describe approaches such as combining optical with neutron Raman scattering and x-ray absorption with neutron imaging and tomography, and carrying out such experiments in specialised fuel cells designed to mimic as closely possible actual operando conditions. These experiments and research projects will play a key role in enabling and testing new membrane formulations for efficient and sustainable energy production/conversion and separations technologies.

Abstract The water distribution of an operating proton exchange membrane fuel cell (PEMFC) was monitored in real time by using Small Angle Neutron Scattering (SANS). The formation of liquid water was obtained simultaneously with the evolution of the water content inside the membrane. Measurements were performed when changing current with a time resolution of 10 s, providing insights on the kinetics of water management prior to the stationary phase. We confirmed that water distribution is strongly heterogeneous at the scale at of the whole Membrane Electrode Assembly. As already reported, at the local scale there is no straightforward link between the amounts of water present inside and outside the membrane. However, we show that the temporal evolutions of these two parameters are strongly correlated. In particular, the local membrane water content is nearly instantaneously correlated to the total liquid water content, whether it is located at the anode or cathode side. These results can help in optimizing 3D stationary diphasic models used to predict PEMFC water distribution.

International audience

Proliferation of hydrogen fuel cell systems is hindered by degradation of the platinum catalyst. Here, we provide a device level assessment of the catalyst degradation phenomena and its coupling to nanoscale hydration gradients, using advanced operando X-ray scattering tomography tailored for device-scale imaging. Gradients formed inside the fuel cell produce heterogeneous degradation of the catalyst nanostructure, which can be linked to the flow field design and water distribution in the cell. Striking differences in catalyst degradation are observed between operating fuel cell devices and the liquid cell routinely used for catalyst stability studies, highlighting the crucial impact of the complex operating environment on the catalyst degradation phenomena. This degradation knowledge gap accentuates the necessity of multimodal, in situ characterization of real devices when assessing the performance and durability of electrocatalysts, and more generally, electrochemically active phases used in energy conversion and storage technologies.