Spectroscopic Neutron Imaging for Chemically Sensitive In Situ Electrolyte Characterisation

Spectroscopic neutron imaging (SNI) is a chemically sensitive imaging technique for probing composition‐dependent variations in a variety of systems, including hydrocarbon‐based liquid battery electrolytes. This technique utilises wavelength‐dependent transmission to distinguish between electrolyte components and H environments by leveraging incoherent scattering interactions in hydrogenous materials, revealing information about the physico‐chemical state. Therefore, SNI has the potential to serve as a powerful tool for electrolyte engineering, enabling in situ studies of electrolyte dynamics, heterogeneity, and degradation within commercial lithium‐ion battery (LIB) environments. To this end, detection limits for hydrogen and total neutron cross‐sections, and , respectively, were evaluated across multiple spatial resolutions, achieving the detection of 10% fluoroethylene carbonate (FEC) in 1 M LiPF 6 dissolved in 3:7 (w/w) ethylene carbonate (EC): ethyl methyl carbonate (EMC) electrolytes at a spatial resolution of 275 μm. These findings establish a framework for applying SNI to electrolyte engineering, enabling the monitoring of solid electrolyte interphase (SEI) formation and characterisation of electrolyte degradation pathways. This framework will support the development of safer, more robust, advanced high energy‐density electrochemical devices from LIBs and beyond.