Designing complex chalcogenides through building block approach

Missouri University Of Science And Technology, Rolla MO

Investigators

Abstract

PART 1: NON-TECHNICAL SUMMARY The performance of a device is dependent on the performance of the materials it is made of. For example, cell phones need a high efficiency lithium-ion battery to run longer without recharging, while HDTVs need good quality phosphors (color generating materials) for high resolution color. Scientists currently achieve and improve the desired properties of the materials in devices by a combination of intuition and painstaking trial and error, resulting in slow rate of discoveries of the new, better and/or cheaper materials. Coming up with rational design principles for new materials can speed-up these discoveries. With support from NSF's Solid State and Materials Chemistry Program in the Division of Materials Research, the team from Missouri S&T develops new materials in a more rational and predictive manner by performing experiments aided by theoretical predictions. The team synthesizes and uses fixed molecular units to produce new materials with tailored properties. These molecular units or building blocks are like legos or bricks that come in various shapes and sizes and can be precisely connected in different and predictable ways. Through this NSF award the team prepares highly conducting solid ion conductors that are needed to enable all-solid-state lithium ion batteries, which are much safer than current technologies. Undergraduate and graduate students from Missouri S&T are involved in carrying out this project and are getting trained to work in the realm of physics and chemistry. Knowledge acquired from this interdisciplinary project is integrated into undergraduate and graduate level courses. Additionally, workshops demonstrating the application of these materials in batteries to high school students and teachers are designed to educate and interest students with an underrepresented minority background in science. PART 2: TECHNICAL SUMMARY Directed synthesis of materials possessing desired property is a sought-after goal in solid state materials chemistry. This project, funded by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, develops direct synthesis methods for multinary chalcogenides via metathesis reactions involving alkali chalcometallates and metal halides. It is based on the hypothesis that in these reactions, chalcometallate building blocks present in the starting reactants remain intact in the targeted compounds. The availability of large number of chalcometallate units containing main group elements with varying negative charge and degree of covalence makes them ideal for the synthesis of materials with desired applications. By choosing appropriate combinations of building blocks and metal ions materials that can generate useful properties related to magnetism, ion conduction and redox properties are rationally designed. The focus of this study is to create more stable solid ion conductors and redox active chalcogenide lattices. Experimental synthesis efforts are performed in tight integration with the predictive Density Functional Theory (DFT) simulations of the thermodynamic stability of the possible structures and compositions. DFT calculations are used together with the chemical intuition to down-select the most promising candidates for synthesis out of the compositional space, which are then synthesized to validate the theoretical prediction. This synergetic experimental-theoretical approach to rationally synthesize complex chalcogenides is translatable to a wide variety of other materials systems with wide range of applications, including energy storage, photovoltaics, thermoelectrics, and solid state lighting. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.