Seminars & Symposium

Title

Ab initio random structure searching for battery cathodes and more

Date

April 9 (Fri.), 2021 16:00-16:40 on Japan Time (8:00-8:40 on British Summer Time)
Although we temporarily close this seminar as a special event of AIMR's Friday Tea Time at around 16:40, the participants who wish to hear more details can continue Zoom connection and the discussion with Dr. Lu till around 17:30.

Venue

Online (Zoom)

Abstract

Cathodes are critical components of rechargeable batteries. Conventionally, the search for cathode materials relies on experimental trial-and-error and a traversing of existing computational/experimental databases. While these methods have led to the discovery of several commercially-viable cathode materials, the chemical space explored so far is limited and many phases will have been overlooked, in particular those that are metastable. We describe a computational framework for battery cathode exploration, based on ab initio random structure searching (AIRSS), an approach that samples local minima on the potential energy surface to identify new crystal structures. We show that, by delimiting the search space using a number of constraints, including chemically aware minimum interatomic separations, cell volumes, and space group symmetries, AIRSS can efficiently predict both thermodynamically stable and metastable cathode materials.

Specifically, we investigate LiCoO₂, LiFePO₄, and Li_xCu_yF_z to demonstrate the efficiency of the method by rediscovering the known crystal structures of these cathode materials. The effect of parameters, such as minimum separations and symmetries, on the efficiency of the sampling is discussed in detail. The adaptation of the minimum interatomic distances, on a species-pair basis, from low-energy optimized structures to efficiently capture the local coordination environment of atoms, is explored. A family of novel cathode materials based, on the transition-metal oxalates, is proposed. They are predicted to demonstrate superb energy density, oxygen-redox stability, and lithium diffusion properties.

The application of AIRSS and density functional theory-based thermodynamics to solid electrolytes and interfaces will also be briefly talked about.