The electrodeposition of metallic lithium is a major cause of failure in lithium batteries. The 3D microstructure of electrodeposited lithium 'moss' in liquid electrolytes has been characterised at ...sub-micron resolution for the first time. Using synchrotron X-ray phase contrast imaging we distinguish mossy metallic lithium microstructures from high surface area lithium salt formations by their contrasting X-ray attenuation.
Ceramic fuel cells offer a clean and efficient means of producing electricity through a variety of fuels. However, miniaturization of cell dimensions for portable device application remains a ...challenge, as volumetric power densities generated by readily-available planar/tubular ceramic cells are limited. Here, we demonstrate a concept of 'micro-monolithic' ceramic cell design. The mechanical robustness and structural integrity of this design is thoroughly investigated with real-time, synchrotron X-ray diffraction computed tomography, suggesting excellent thermal cycling stability. The successful miniaturization results in an exceptional power density of 1.27 W cm
at 800 °C, which is among the highest reported. This holistic design incorporates both mechanical integrity and electrochemical performance, leading to mechanical property enhancement and representing an important step toward commercial development of portable ceramic devices with high volumetric power (>10 W cm
), fast thermal cycling and marked mechanical reliability.
An optically transparent polymer electrolyte membrane (PEM) water electrolysis cell was studied using a high-speed camera, thermal imaging and electrochemical impedance spectroscopy to examine the ...relationship between flow and electrochemical performance. The flow regime spans bubble and slug flow, depending on the rate of gas formation (current density) and water feed rate. Electrochemical impedance spectroscopy (EIS) shows that there is a reduction in mass transport limitation associated with the transition to slug flow.
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•Optically transparent electrolyser cell made using printed circuit boards.•Different flow regimes identified as function of current and water feed rate.•Bubble-induced mass limitation identified in electrochemical impedance response.•Criteria for flow optimisation presented.
Obligate seeder trees requiring high‐severity fires to regenerate may be vulnerable to population collapse if fire frequency increases abruptly. We tested this proposition using a long‐lived obligate ...seeding forest tree, alpine ash (Eucalyptus delegatensis), in the Australian Alps. Since 2002, 85% of the Alps bioregion has been burnt by several very large fires, tracking the regional trend of more frequent extreme fire weather. High‐severity fires removed 25% of aboveground tree biomass, and switched fuel arrays from low loads of herbaceous and litter fuels to high loads of flammable shrubs and juvenile trees, priming regenerating stands for subsequent fires. Single high‐severity fires caused adult mortality and triggered mass regeneration, but a second fire in quick succession killed 97% of the regenerating alpine ash. Our results indicate that without interventions to reduce fire severity, interactions between flammability of regenerating stands and increased extreme fire weather will eliminate much of the remaining mature alpine ash forest.
Lung-inspired, fractal flow-fields hold great potential in improving the performance of polymer electrolyte membrane fuel cells (PEMFCs) by providing uniform gas distribution across the electrodes ...and ensuring minimum entropy production in the whole system. However, the inherent susceptibility of the fractal flow-fields to flooding renders their use inadequate at high humidity conditions. In-depth understanding of water management in lung-inspired flow-fields is indispensable for the implementation of alternative outlet channel geometries or engineered water removal strategies to alleviate flooding. Here, liquid water formation and transport across the lung-inspired and serpentine flow-field based PEMFCs are evaluated using neutron radiography. The results reveal a propensity to flooding in the interdigitated outlet channels of the fractal flow-field with N = 4 generations as a result of slow gas velocity and narrow channel dimensions, which leads to significant performance deterioration. Neutron images also elucidate the importance of ensuring a well-defined internal channel structure of the fractal flow-fields to prevent backflow of liquid water via wicking and capillary pressure build-up arising from the narrow inlet gas channels and hydrophobic gas diffusion layer.
•Neutron radiographs are presented for the lung-inspired and serpentine flow-fields.•A well-defined channel structure of the fractal flow-field is indispensable.•Water removal strategies required to alleviate flooding in the fractal flow-field.
Optimizing the chemical and morphological parameters of lithium-ion (Li-ion) electrodes is extremely challenging, due in part to the absence of techniques to construct spatial and temporal ...descriptions of chemical and morphological heterogeneities. We present the first demonstration of combined high-speed X-ray diffraction (XRD) and XRD computed tomography (XRD-CT) to probe, in 3D, crystallographic heterogeneities within Li-ion electrodes with a spatial resolution of 1 μm. The local charge-transfer mechanism within and between individual particles was investigated in a silicon(Si)−graphite composite electrode. High-speed XRD revealed charge balancing kinetics between the graphite and Si during the minutes following the transition from operation to open circuit. Subparticle lithiation heterogeneities in both Si and graphite were observed using XRD-CT, where the core and shell structures were segmented, and their respective diffraction patterns were characterized.
The next generation of automotive lithium‐ion batteries may employ NMC811 materials; however, defective particles are of significant interest due to their links to performance loss. Here, it is ...demonstrated that even before operation, on average, one‐third of NMC811 particles experience some form of defect, increasing in severity near the separator interface. It is determined that defective particles can be detected and quantified using low resolution imaging, presenting a significant improvement for material statistics. Fluorescence and diffraction data reveal that the variation of Mn content within the NMC particles may correlate to crystallographic disordering, indicating that the mobility and dissolution of Mn may be a key aspect of degradation during initial cycling. This, however, does not appear to correlate with the severity of particle cracking, which when analyzed at high spatial resolutions, reveals cracking structures similar to lower Ni content NMC, suggesting that the disconnection and separation of neighboring primary particles may be due to electrochemical expansion/contraction, exacerbated by other factors such as grain orientation that are inherent in such polycrystalline materials. These findings can guide research directions toward mitigating degradation at each respective length‐scale: electrode sheets, secondary and primary particles, and individual crystals, ultimately leading to improved automotive ranges and lifetimes.
High voltage operation of Ni‐rich cathodes can meet the rate and capacity demands of electric vehicles; however, degradation impedes practical application. This work reports that fabrication cracking is more severe at the cathode‐separator interface; variously sized secondary particles can experience operational cracking; even low cycle numbers can induce inter‐primary particle splitting; and crystal disorder may be linked to Mn mobility.
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