In situ neutron imaging of lithium-ion batteries during heating to thermal runaway.

Lithium-ion batteries (LIBs) have become essential components that power most current technologies, such as smartphones and electric vehicles, thus making various safety evaluations necessary to ensure their safe use. Among these evaluations, heating tests remain the most prominent source of safety issues. However, information on the phenomena occurring inside batteries during heating has remained inaccessible. In this study, we demonstrate the first in situ neutron imaging method to observe the internal structural deformation of LIBs during heating. We developed an airtight aluminium chamber specially designed to prevent radioactive contamination during in situ neutron imaging. We successfully observed the liquid electrolyte fluctuation inside a battery sample and the deformation of the protective plastic film upon heating up to thermal runaway. Hence, this work provides the foundation for future investigations of the internal changes induced in batteries during heating tests and experiments.

The energy-resolved neutron imaging system, RADEN.

The energy-resolved neutron imaging system, RADEN, has been installed at the pulsed neutron source in the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Research Complex. In addition to conventional neutron radiography and tomography, RADEN, the world's first imaging beam-line at a pulsed neutron source, provides three main options for new, quantitative neutron imaging techniques: Bragg-edge imaging to visualize the spatial distribution of crystallographic information, resonance absorption imaging for elemental composition and temperature information, and polarized neutron imaging for magnetic field information. This paper describes the results of characterization studies of the neutronic performance and installed devices at RADEN and shows the results of several demonstration studies for pulsed neutron imaging.

Development of a biaxial tensile testing machine for pulsed neutron experiments.

A biaxial tensile testing method has been used to get macroscopic information on elastoplastic deformation of a thin steel specimen and improve the accuracy of plastic processing of steel materials. We newly developed a biaxial tensile testing machine for pulsed neutron experiments (BTM-NEU) to provide the microscopic crystallographic information of steel materials under biaxial load and correlate it with the macroscopic mechanical properties of the materials. The performance of the BTM-NEU was experimentally evaluated with cold-rolled mild steel and hot-rolled high-tensile-strength steel materials and compared with that of a standard biaxial tensile testing machine (BTM-std) as follows. •The BTM-NEU can test an ISO-standardized cruciform specimen as the BTM-std and its performance is equivalent to that of the BTM-std.•The BTM-NEU has excellent long-time reliability and stability necessary for pulsed neutron experiments, especially Bragg-edge neutron imaging experiments.•The BTM-NEU can be applied to pulsed neutron experiments using a Bragg-edge imaging method.