In Situ and (in) Operando Neutron Diffraction for Energy Materials: a Practical Guide to Design, Execution, and Data Analysis

Neutron diffraction has become an indispensable technique for probing structural evolution in energy materials and devices under realistic operating conditions. Compared to other scattering techniques such as X-ray or electron-based methods, using neutrons as a probe offers unique advantages. High sensitivity to light elements such as lithium and hydrogen especially in the presence of heavier elements, isotope discrimination, and a high penetration depth for non-destructive bulk analysis. These features enable characterization of complex, multi-component systems and allow experiments within functional devices without modification. This article provides a practical introduction to the application of neutron diffraction in the context of materials and devices for energy storage and generation, including principles of neutron–matter interactions, best practices for planning and executing experiments, considerations for sample environments and mitigating common measurement artefacts, and suggestions for data acquisition and analysis. Recent advances in neutron source intensity, detector technology, and automated data processing have significantly improved temporal resolution, enabling real-time tracking of phase transitions, lattice strain, and ion migration pathways during device operation providing mechanistic insights into energy materials and devices.