Fast ion conductors are major players in energy storage; critical for widespread vehicle electrification and the best solution to the intermittent and random nature of many renewable energy sources (solar and wind). Past research has heavily focused on ion conductors with perfect prototype structures, resulting in limited and incremental improvement in a narrow chemical space. The Ji research group specializes structurally-disordered ion conductors with compositional flexibility that can potentially alleviate the industry’s unsustainable reliance on any single critical metal source. We explore diverse research projects with some highlights including:
Battery Materials
Fast charging remains one of the greatest safety challenges in Li-ion batteries due to Li-dendrite growth occurring on graphite anodes if they are lithiated too quickly. The search for high-rate anodes has highlighted materials in the Wadsley-Roth (WR) shear phase family. The relative abundance of V compared with traditional WR compositions of Nb and W makes V-based phases attractive. However, the high voltage and poor reversibility typically associated with V-redox have made V-rich WR phases less studied than Nb- and W-rich phases. In an upcoming Chemistry of Materials paper we show that a new V-rich Wadsley-Roth phase achieves excellent rate capability.
Diffuse Scattering
The facile transport of ions in crystalline materials enables key functionality in various devices, such as batteries, membranes, and fuel cells. The structural characterization of these materials, however, presents an outstanding challenge. As a result, past research either had to ignore it for lack of instrument sensitivity or avoided it completely for fear of complexity and unpredictability. We overcome these difficulties by performing state-of-the-art synchrotron and neutron scattering to characterize these structural subtleties.
Memory Devices
Battery-inspired materials have recently demonstrated high-speed low-energy switching behavior that can be used to develop next-generation memory devices for powerful computation. We apply our expertise in fast ion conductors and subtle structural determination to developing memory devices from Li-intercalated neuromorphic materials and intercalated transition metal dichalcogenides. We modify the compositional and synthesis variables and correlate these parameters with structural observations and property measurements to reveal previously overlooked structure-property relationships. These insights enable the design of disruptively new materials.
STEM Outreach
The Ji Research Group is invested in fostering the next generation of researchers and STEM professionals. We have created STEM activity kits with a focus on opals and crystallography for middle and high school students, have developed of an augmented reality app for interactive crystallography called Crystal Impact that is freely available on the Google Play Store, and have mentored local middle-school science fair teams.
JI GROUP 