The temporally and spatially resolved tracking of lithium intercalation and electrode degradation processes are crucial for detecting and understanding performance losses during the operation of lithium-batteries. Here, high-throughput X-ray computed tomography has enabled the identification of mechanical degradation processes in a commercial Li/MnO 2 primary battery and the indirect tracking of lithium diffusion; furthermore, complementary neutron computed tomography has identified the direct lithium diffusion process and the electrode wetting by the electrolyte. Virtual electrode unrolling techniques provide a deeper view inside the electrode layers and are used to detect minor fluctuations which are difficult to observe using conventional three dimensional rendering tools. Moreover, the 'unrolling' provides a platform for correlating multi-modal image data which is expected to find wider application in battery science and engineering to study diverse effects e.g. electrode degradation or lithium diffusion blocking during battery cycling.

Lithium sulfur (Li–S) batteries have great potential as a successor to Li-ion batteries, but their commercialization has been complicated by a multitude of issues stemming from their complex multiphase chemistry. In situ X-ray tomography investigations enable direct observations to be made about a battery, providing unprecedented insight into the microstructural evolution of the sulfur cathode and shedding light on the reaction kinetics of the sulfur phase. Here, for the first time, the morphology of a sulfur cathode was visualized in 3D as a function of state of charge at high temporal and spatial resolution. While elemental sulfur was originally well-dispersed throughout the uncycled cathode, subsequent charging resulted in the formation of sulfur clusters along preferred orthogonal orientations in the cathode. The electrical conductivity of the cathode was found not to be rate-limiting, suggesting the need to optimize the loading of conductive carbon additives. The carbon and binder domain and surrounding bulk pore phase were visualized in the in situ cell, and contrast changes within both phases were successfully extracted. The applications of this technique are not limited to microstructural and morphological characterization, and the volumetric data can serve as a valuable input for true 3D computational modeling of Li–S batteries.

The cold neutron imaging and diffraction instrument IMAT at the second target station of the pulsed neutron source ISIS is currently being commissioned and prepared for user operation. IMAT will enable white-beam neutron radiography and tomography. One of the benefits of operating on a pulsed source is to determine the neutron energy via a time of flight measurement, thus enabling energy-selective and energy-dispersive neutron imaging, for maximizing image contrasts between given materials and for mapping structure and microstructure properties. We survey the hardware and software components for data collection and image analysis on IMAT, and provide a step-by-step procedure for operating the instrument for energy-dispersive imaging using a two-phase metal test object as an example.

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The increasing use of intermittent renewable energy sources calls for novel approaches to large-scale energy conversion and storage. Hydrogen can be readily stored and produced from renewable sources using polymer electrolyte membrane water electrolysers (PEMWEs). Mass transport of water and product gas in the liquid-gas diffusion layer (LGDL) is critical for PEMWE performance, particularly at high current densities. In this work, neutron radiography is deployed to measure the spatial distribution of water within three different LGDLs, while X-ray micro-computed tomography (XCT) is used to characterize the microstructure of the LGDL materials. The combination of these two techniques yields valuable insight into water transport within the LGDL. Significant local water heterogeneity is observed and a link between flow-field geometry/location and LGDL mass transport is identified. It is further shown that the pore volume in these LGDLs is significantly under-utilized, pointing the way towards design optimisation of LGDL materials and architectures.

In-depth understanding of the dynamics of water formation, accumulation and removal is important for flow-field design optimization to ensure robust performance and durability of polymer electrolyte fuel cells (PEFCs). Here, in-operando neutron radiography is used to display and quantify liquid water distribution across the entire active area of single-, double-and quad-channel serpentine flow-fields. The results revealed that the water management and performance of PEFCs is strongly affected by the number of serpentine channels in the cathode flow-field. The single-channel serpentine-based PEFC exhibits both a better cell performance and uniformity in the local water distribution. The quad-channel based PEFC exhibits the largest voltage fluctuations caused by severe water flooding in the gas channels. However, the single-channel design leads to significantly larger pressure drop than the multiple-channel counterparts, which requires much higher parasitic power to pressurize and recirculate the reactants. Three different regimes of operation can be defined based on the current density: gradually increasing hydration (< 400 mA cm-2), flooding (400 mA cm-2 ≤ j ≤ 600 mA cm-2) and drying out (>600 mA cm-2). The reduced overall quantity of water in the channels with an increase in current density can be attributed to faster gas velocity and higher cell temperature.

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Water dynamics in the membrane electrode assembly (MEA) and flow channels of polymer electrolyte fuel cells (PEFCs) is governed by the complex interplay of many physical and operational factors. The chemical nature and structure of the gas diffusion layer (GDL) plays a large part in this and is affected by the extent to which is mechanically compressed. Here, X-ray computed tomography shows the effect of cell compression on the MEA, and how it differs under the land and channel regions. Multi-orientation neutron radiography reveals the effect of compression on the way in which water accumulates and is transported between land and channel and between cathode and anode. By performing neutron imaging in both the inplane and through-plane directions it is possible to determine what constitutes a given 'thickness' of water mapped across the extent of an MEA. Changing MEA compression from 25% to 35% has a significant effect on water distribution and dynamics in operational cells. The effect of compression on performance is most marked in the mass transport region and there are consequences for liquid accumulation in channels and back-diffusion of water from the cathode to the anode.