The investigation of lithium-ion battery failures is a major challenge for personnel and equipment due to the associated hazards (thermal reaction, toxic gases and explosions). To perform such experiments safely, a battery abuse-test chamber has been developed and installed at the microtomography beamline ID19 of the European Synchrotron Radiation Facility (ESRF). The chamber provides the capability to robustly perform in situ abuse tests through the heat-resistant and gas-tight design for flexible battery geometries and configurations, including single-cell and multi-cell assemblies. High-speed X-ray imaging can be complemented by supplementary equipment, including additional probes (voltage, pressure and temperature) and thermal imaging. Together with the test chamber, a synchronization graphical user interface was developed, which allows an initial interpretation by time-synchronous visualization of the acquired data. Enabled by this setup, new meaningful insights can be gained into the internal processes of a thermal runaway of current and future energy-storage devices such as lithium-ion cells.

Passengers routinely carry numerous Portable Electronic Devices (PEDs) powered by lithium-ion batteries, which present hazards when subjected to thermal runaway, including emission of toxic gases, smoke generation and potential fires. The LOKI-PED project investigates the severity of such events in aircraft cabins by experimentally characterizing combustion gases, validating a zonal cabin model and predicting exposure to harmful substances and smoke. PEDs were deliberately forced into thermal runaway in both burn chamber and A320 cabin mockup tests, enabling the quantification of emitted carbon dioxide and toxic compounds such as carbon monoxide, formaldehyde, hydrogen fluoride, and hydrogen chloride. These measurements were correlated to CO₂ peak concentrations, enabling a factor-based scaling approach for full-scale cabin simulations. A validated zonal model was then used to predict the temporal and spatial spread of gases and smoke in the cabin, cockpit and galley. Results show that while cabin ventilation generally keeps exposure below harmful levels, the cockpit and galley are significantly more vulnerable. The study highlights the importance of rapid crew response, limitations on PED battery capacities and operational mitigation strategies to ensure flight safety.

Electrochemical double layer capacitors (EDLCs) are widely considered to be reliable energy storage systems; however, their behavior when subjected to overcharge remains poorly understood. Using time‐resolved, in situ synchrotron radiography combined with synchronized thermal and electrical measurements, we directly visualize the internal evolution of EDLCs under abusive overcharge. We reveal a progressive, thermally driven failure pathway, distinct from the chemically driven thermal runaway seen in lithium‐ion batteries, in which initial electrical instability triggers electrolyte decomposition, vapour formation, and gas accumulation, generating heterogeneous internal pressures that drive electrode collapse, casing deformation, and structural destruction. Post‐mortem X‐ray Computed Tomography (X‐ray CT) and cell tear‐down confirm permanent electrode delamination and separator failure, while Gas Chromatography‐Mass Spectrometry (GC‐MS) analysis of vented gases identifies flammable and potentially toxic species, highlighting acute fire and chemical hazards. By linking internal structural dynamics to external failure signatures, this work provides the most detailed mechanistic picture of EDLC failure to date and reinforces the importance of acknowledging and mitigating underappreciated hazard modes in high‐power, high‐reliability system design.