Huiwen Ji

The facile transport of ions through crystalline materials underpins the functionality of numerous devices, including batteries, separation membranes, and fuel cells. Structural characterization of these materials, however, remains a major challenge: they often exhibit short-range order, whereas conventional diffraction techniques primarily probe long-range periodic structures. Precise characterization of short-range order not only reveals previously inaccessible structure-property relationships but also opens opportunities to discover materials with greater structural complexity. This talk will begin with a new class of battery materials known as cation-disordered rocksalts, whose ionic conductivity and electrochemical performance critically depend on the formation and percolation of local migration pathways. These local structures can be characterized using powder pair distribution function analysis in conjunction with first-principles calculations. We will then introduce the three-dimensional difference pair distribution function (3D-ΔPDF) as a direct, model-free approach for visualizing local chemical and displacive correlations, and demonstrate how its application reveals previously unrecognized structure-property relationships in superionic conductors.