This renewal award to SUNY Stony Brook by the Solid State Materials Chemistry program in the Division of Materials Research is aimed at understanding how electrode materials and anionic conductors function under operating conditions. With this project, Professor Grey will be building, testing and utilizing a NMR probe designed to acquire NMR spectra of functioning and intact lithium-ion batteries. Lithiated silicon anode materials, which are in metastable crystalline phase, will be studied using a combination of in and ex-situ 7Li and 29Si Magic Angle Spinning Nuclear Magnetic Resonance (NMR) spectroscopy and pair distribution function analysis of x-ray and neutron scattering. A second application involves the investigation of nanoparticles of layered materials such as LixCoO2, to determine the effect that size and morphology have on the various phase transitions that occur on charging this material, and the stability of the charged materials in the electrolyte. Nanoparticulate cathode materials are expected to have applications in high power batteries in, for example, hybrid electric or electric vehicles. The role of local structures on long-range anionic conductivity of electrode materials such as perovskite (such as LaGaO3) and browmillerite (such as Ba2In2O5) along with materials that can be viewed as intermediates between these end-number structures will also be studied as the second part of this study. Variable temperature NMR spectroscopy (e.g., 71Ga, 89Y NMR) of the B sites will be used to determine the coordination environments of the cations as a function of temperature, while 17¬O NMR spectroscopy will be used to determine the mobility of the oxide ions in different local environments of the electrode materials.
The materials investigated by this program will have significant technological relevance for the design of the next generation of materials for use in Lithium ion batteries and fuel cells. The use of silicon as an anode material for a Lithium ion batteries is likely to be of great commercial interest. In addition, the project will provide fundamental insight in the design and development of the next generation of materials for energy sources, improved batteries and fuel cells. Graduate, undergraduate and high students working in this project through their research and classroom experiences will be trained in sophisticated techniques with an appreciation to their use to solve important technical problems.
Nuclear magnetic resonance (NMR) approaches have been developed to investigate materials used in fuel cells and batteries. One focus was on materials with either rapid oxygen ion or proton transport, which have potential applications as solid-state electrolytes in fuel cells. In the first study, we have investigated the anion vacancies and defects formed on doping perovskite ceramics. NMR was used to determine the locations of the vacancies. Density Functional Theory calculations were employed to help assign the NMR spectra and determine the energies of the different defects relevant for fast ionic mobility. High temperature NMR spectroscopy was used to establish how the ions move within the solid and to link rapid mobility to specific local structures. Water can be accommodated in the vacant sites, the water molecules splitting to form structural hydroxyl groups and protons. NMR has been used to follow the hydration process and to identify optimal structures for high protonic transport. In a second effort, new methods were developed to study the structural and dynamical changes that occur in lithium-ion and lithium batteries while they are being charged and discharged in real time (i.e. in-situ). Applications of the method included the observation of self-discharge in a lithium-silicon battery.
