Annual Review 2024-2025

D I A M O N D L I G H T S O U R C E L I M I T E D 13 explore planetary interior conditions, as well as other experiments requiring high pressures and non-ambient temperatures including porous materials and engineering applications. I15-1 is a dedicated X-ray Pair Distribution Function beamline. The pair distribution function allows researchers in fields as diverse as materials chemistry, solid-state physics, Earth science and pharmaceuticals to gain insight into the local structure of crystalline, amorphous, and liquid materials both ex situ and in situ . I19 is a high-flux tuneable-wavelength facility for the study of small-molecule systems by single-crystal X-ray diffraction techniques. The beamline supports high throughput analysis of challenging samples as well as a variety of techniques to map structural change of systems under the influence of an external effect (such as pressure, temperature, photoexcitation or gas exchange). Solid electrolytes: a breakthrough for safer, high-performance batteries Batteries are a critical technology for the transition to a sustainable energy economy. Most Li-ion batteries rely on a liquid electrolyte to conduct ions between the anode and cathode. However, liquid electrolytes can leak and are flammable, which can lead to fires. One solution to this issue is to use a solid electrolyte. A team of researchers from the University of Liverpool have discovered a solid material with high enough Li-ion conductivity to replace the liquid electrolytes in current Li-ion battery technology, improving safety and energy capacity. The team opted for a design strategy using multiple anions to construct suitable pathways, supported by AI and physics-based calculations. The material they synthesised, Li 7 Si 2 S 7 I, is a pure Li-ion conductor created by an ordering of sulphide and iodide with many different cation coordination environments that combine to create superionic conductivity. Created from non-toxic earth-abundant elements, the new material operates in a new way and achieves a high enough Li-ion conductivity to replace liquid electrolytes. After suitable crystals for single-crystal diffraction were grown, the team used high resolution single-crystal X-ray Diffraction (SCXRD) on beamline I19 to solve the crystal structure. Measurements on these initial crystal samples - using both SCXRD on the I19 beamline, and Powder X-ray Diffraction (PXRD) on I11 - showed that the material has a lot of disordered lithium sites. Operando studies confirmed that the high conductivity of Li 7 Si 2 S 7 I arises from a combination of Li-ion sites of widely varying geometry and anion coordination. This diversity offers multiple rapid transport pathways by providing many different low-barrier site-to-site connections. The team is now exploring ways to optimise the chemistry of Li 7 Si 2 S 7 I to further enhance the properties of the material. The new understanding provided by the study will also allow the identification of other materials that are well suited to exploratory synthesis. DOI: 10.1126/science.adh5115 C RY S TA L L O G R A P H Y G R O U P The figure represents the lithium ions (in blue) moving through the structure (Credit: Liverpool University)