Collaborative Research: Understanding Relationships Between Synthesis, Structure, Solid-State Electrochemistry, and Phase Stability in Clathrates and Related Materials

点击翻译按钮获取中文摘要

NON-TECHNICAL DESCRIPTION:Clathrates are a class of materials with cage-like structures that can naturally hold guest ions, a feature that may be exploited for energy storage in rechargeable batteries. However, more research is needed to understand how the structure of the clathrate affects ion migration and the durability of the material under repeated electrochemical cycling. Through this collaborative project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, researchers at Arizona State and University of Delaware jointly identify structural features of the clathrates that promote fast ion diffusion and develop new approaches to synthesize these materials. Thereby they gather new knowledge connecting the structural effects of clathrates and related compounds to their physical, electrochemical, and materials chemistry properties. The fundamental science gained from these studies could have far reaching impacts in other fields where these materials have potential applications, such as superconductors, thermoelectrics, optoelectronics, magnets, and photovoltaics. Additionally, this collaboration between two universities and three different departments (materials science, chemistry, and physics) exposes students to multidisciplinary research. Outreach and educational activities also engage students and provide interdisciplinary training and immerse them into areas outside their immediate field of expertise. TECHNICAL DESCRIPTION:This collaborative project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, identifies structural features that lead to fast ion diffusion and obtain better understanding of electrochemically driven phase transformations in Li-Tetrel (Tt) systems, particularly for clathrates and other open framework structures. The specific objectives of the research are to: (1) Understand the structural parameter space for Tt (Tt = Si, Ge, Sn) clathrate and clathrate-like materials with high ionic mobility; (2) Re-map the phase space of Li-Tt systems, including non-equilibrium phases, coupled with studies on understanding the ionic transport within these phases, and (3) Use electrochemistry to inform solid-state synthesis and vice versa, to enable new synthetic approaches for clathrates and related materials that are either intermediates in the lithiation pathways or can be used as precursors for the synthesis steps. Through a concerted approach combining the synthetic, structural and electrochemical characterization, and theoretical expertise of the PIs, this work furthers the electrochemical understanding of clathrate materials, leading to new insights on structural features that result in fast diffusion pathways, low ion migration barriers, and phase stability. Novel synthetic approaches combining high temperature coulometric titration and low temperature flux methods are used to trap kinetic/metastable phases and controllably synthesize high quality single-crystalline materials. Isostructural compounds containing key Li local environments are employed as model compounds to understand the ion (de)insertion processes in Li-Tt binary (and ternary/quaternary) compounds, with an emphasis on Tt = Ge. By means of a unique feedback loop connecting electrochemistry and synthesis, information about phases formed during electrochemical lithiation is used to design novel precursors for synthesis of clathrates, and solid-state reactions using chemical oxidation are adapted to develop electrochemical synthesis methods with finer control over composition. Synchrotron X-ray studies are used to characterize the local and crystalline structures and phase evolution during electrochemical reaction and/or synthesis. In all cases, density functional theory calculations support experimental findings and guide materials design, particularly by identifying formation energies and ionic transport mechanisms.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.