Huiwen Ji: Harnessing structural complexity for the design of new battery materials

Harnessing structural complexity for the design of new battery materials

Abstract
The facile transport of alkali ions in inorganic crystalline materials is a prerequisite for the many electrochemical processes in rechargeable batteries, the production of which is now being rapidly scaled up to electrify vehicles and even enable grid-scale energy storage. Achieving fast ion transport kinetics in electrode materials requires an optimized crystal structure with favorable short-range atomic arrangements, which are, in the meantime, extensively connected in the long range. In conventional electrode materials, wherein a single unit cell exactly repeats its chemistry and geometry into infinity, the two criteria conveniently become one. Such perfectly-ordered structures, though easy to characterize, lack flexibility and impose a narrowed selection in chemistry, causing significant strains on several metal resources, such as cobalt and nickel. In this talk, I will show how strategically introducing compositional and structural disorder into a simple rocksalt lattice can lead to the discovery of novel electrode materials with ultrahigh energy and power density as well as a reversible anion redox process. The design strategies might open up a vast chemical space for the search of new battery materials made from earth-abundant elements. As the degree of disorder further increases, resulting in the so-called class of cation-disordered rocksalt materials, the degeneracy of chemical/structural order at various length scales gets lifted. As a result, cation short-range order (SRO), hidden in diffraction, is not only ubiquitous but also controls the Li transport behavior. General guidelines are identified for manipulating cation SRO for the benefit of Li transport.

Speaker Bio:
Huiwen Ji, Ph.D., enjoys working at the intersection of solid state chemistry, condensed matter physics and materials engineering. She is most interested in synthesizing and characterizing solid-state materials with functional properties, establishing chemistry-structure-property relationships to accelerate materials innovation. She received her doctorate degree in chemistry from Princeton University, where she worked with Professor Robert J. Cava to discover new topological insulators and van der Waals magnetic materials. She then spent three years as a postdoctoral associate, at the University of California Berkeley under Professor Gerbrand Ceder, studying cation-disordered oxides and oxyfluorides as a new class of high-capacity Li-ion cathode materials. She is now a John S. Newman Early Career Scientist in the Energy Storage & Distributed Resources Division at Lawrence Berkeley National Laboratory.