CAREER: Scalable Liquid Exfoliation Processing of Ultrathin Two-Dimensional Metal Dichalcogenides Nanosheets for Energy Storage Devices

Kansas State University, Manhattan KS

Investigators

Abstract

This Faculty Early Career Development (CAREER) Program grant will establish a novel process for large-scale production of atomically thin sheets of transition metal dichalcogenides (or TMDs) with optimized properties suitable for energy-based applications, specifically, rechargeable metal-ion batteries. TMD sheets possess several distinct functional properties that are not realized in their bulk crystalline form or in other widely studied layered materials such as pristine graphene and hexagonal boron nitride. One major hurdle currently impeding the commercial success of TMDs is lack of production at larger scales while maintaining desired chemical and physical attributes. This award supports fundamental research to provide needed knowledge for the development of a solution-based processing route that involves spontaneous exfoliation (i.e., separation into single molecular layers) of bulk crystals in strong acids. The new process will enable production of kilogram quantities of ultrathin TMD nanosheets, which would overcome major roadblocks and unlock a vast array of applications for these materials in the energy sector, ranging from inexpensive catalysts for hydrogen production to high performance rechargeable batteries and supercapacitors. Therefore, results from this research will promote the U.S. economy, environment, and quality of life of its citizens. This research spans across several disciplines including manufacturing, engineering mechanics, electrochemistry, and materials science. The inter-disciplinary approach will increase participation by underrepresented groups in laboratory research and positively impact engineering education. This project's solution-based approach can overcome challenges that current methods have such as low production rates of single layer sheets, scission of sheets into sub-micron sized particles, and long sonication times (hours to days). However, additional scientific barriers need to be overcome in order to unlock the full potential of exfoliated TMDs in the energy sector (for example, sodium-ion rechargeable batteries). These include, lack of basic science related to exfoliation mechanism(s); inability to manufacture large-area nanostructured TMD electrodes with desired fracture properties; and unexplored mechanism(s) of TMD/metal-ion intercalation and conversion chemistry. This project aims to fill-in these knowledge gaps by (1) performing experiments and developing theoretical formulations to explain the dominant mechanisms for spontaneous exfoliation of bulk TMDs into ultrathin sheets, (2) assessing the processing advantages of exfoliated sheets by interfacing with graphene (thinnest and strongest electrical conductor) to form composite electrodes, thereby testing the limits of nanostructuring on fracture strength and electrochemical storage capacity, and (3) combining novel in-situ and ex-situ experimental techniques with companion computational models to establish TMD/metal-ion intercalation chemistry and phase transition mechanisms.