Unveiling relationships between synthesis, structure and nonaqueous ion cycling in chemically preintercalated layered oxides

PART 1: NON-TECHNICAL SUMMARY

The expanding variety of applications relying on portable autonomous power sets a challenge for the discovery of innovative materials to be used as high-capacity electrodes in batteries with lithium and more affordable sodium and potassium ions in electrolytes. The solution is offered by hydrated layered oxides with a large interlayer region, such as bilayered vanadium oxides (BVOs).

This research, funded by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, exploits controllable BVOs preparation via a low-temperature wet-chemical synthesis route, developed in the Prof. Pomerantseva’s laboratory and called chemical preintercalation, to incorporate specific amounts of various ions and molecules into the interlayer region of material structure.

The structure parameters governing improved transport of electrochemically cycled ions and enhanced structural stability are revealed leading to advanced electrochemical properties. This research provides necessary information for the design of electrode materials to enable next-generation energy storage systems with high energy density and long cycle life.

The fundamental new knowledge gained from this study also advances emerging applications based on reversible cycling of ions beyond energy storage, such as sensing, actuation, ion-tunable non-volatile memory and electrochromics. This project provides a platform to equip senior undergraduate and graduate students with interdisciplinary skills. The educational and outreach efforts enrich undergraduate and graduate curricula at the PI’s institution, enhance women’s involvement in science and engineering, and introduce pre-college students to energy storage technology through the development of a new intercalation reaction demonstration.

PART 2: TECHNICAL SUMMARY

This project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, develops strategies to alleviate performance degradation of high-capacity metastable hydrated layered insertion oxides with an expanded interlayer region over extended electrochemical cycling caused by structural instability. The goal of this research project is to provide a fundamental understanding of how the nature and amount of interlayer species affect the structure and energy storage properties of this family of materials.

Bilayered vanadium oxides (BVOs), which demonstrate unique chemical versatility of the interlayer region, serve as the model material system. Complimentary X-ray and neutron pair distribution function analysis is used to determine the positions of all atoms in the structure of BVOs to establish structure – property correlations. The goal is achieved by testing the hypothesis that interlayer species define diffusion pathways and mechanism of charge storage by not only forming certain arrangements in the interlayer region but also directing the formation and intralayer structure of V-O layers.

The hypothesis consists of three parts, each of which is tested in the project: (1) The nature and amount of chemically preintercalated inorganic ions determine the structure of V-O layers, thus affecting diffusion of electrochemically cycled ion; (2) Interlayer water molecules contribute to creating intercalation sites and diffusion paths for electrochemically cycled ions and their concentration can be controlled at certain value, enabling stability of layered structure with minimized parasitic reactions which cause performance degradation; (3) Further tunability of the structure and charge storage properties of bilayered vanadium oxides can be achieved via chemical preintercalation of versatile organic species. The ultimate aim of this research is to determine correlations between chemical composition of the interlayer region and the structure of bilayered vanadium oxides and to establish parameters that lead to facilitated diffusion of electrochemically cycled ions and enhanced structural and electrochemical stability of the electrodes in nonaqueous Li-ion, Na-ion and K-ion intercalation batteries.

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.