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/MnO₂ 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.

The electrochemical reduction of CO₂ is a pivotal technology for the defossilization of the chemical industry. Although pilot-scale electrolyzers exist, water management and salt precipitation remain a major hurdle to long-term operation. In this work, we present high-resolution neutron imaging (6 μm) of a zero-gap CO₂ electrolyzer to uncover water distribution and salt precipitation under application-relevant operating conditions (200 mA cm⁻² at a cell voltage of 2.8 V with a Faraday efficiency for CO of 99%). Precipitated salts penetrating the cathode gas diffusion layer can be observed, which are believed to block the CO₂ gas transport and are therefore the major cause for the commonly observed decay in Faraday efficiency. Neutron imaging further shows higher salt accumulation under the cathode channel of the flow field compared to the land.

This paper explains why the critical state of sand is non-unique when expressed in terms of stress and void ratio only. For this purpose, a thermodynamically consistent, micromechanically inspired constitutive modelling framework with competing grain crushing and dilation is developed. While grain crushing is described through the theory of breakage mechanics, dilation is modelled in a novel way by acknowledging its negative contribution to the overall positive rate of dissipation. The competition between dilation and grain crushing underpinned by this framework yields a unique critical state in a space of stress, void ratio and breakage, in agreement with recent experiments. As an example, a simple constitutive model with only five mechanical parameters is proposed, which not only predicts the critical state but also quantitatively connects the full constitutive behaviour to key index properties related to grading- and breakage-dependent minimum and maximum densities.