לוח שנה משולב

Fundamental materials research is needed to move present-day energy storage technologies to the scale needed to develop all-electric vehicles and to manage intermittent sources such as wind and solar. Structural studies of materials utilized in lithium battery and fuel cell technology are often hampered by the lack of long-range order found only in well-defined crystalline phases. Powder x-ray diffraction yields only structural parameters that have been averaged over hundreds of lattice sites, and is unable to provide structural information about amorphous compounds. Our laboratory utilizes solid state nuclear magnetic resonance (NMR) methods to investigate structural and chemical aspects of lithium ion cathodes, anodes, electrolytes, interfaces and interphases. NMR is element- (nuclear-) specific and sensitive to small variations in the immediate environment of the ions being probed, for example Li+. NMR is also a powerful tool for probing ion and molecular motion in polymer electrolytes for lithium batteries and fuel cells (both hydrogen and direct methanol), with a dynamic range spanning some ten orders of magnitude through spin-lattice relaxation and self-diffusion measurements. A survey of brief summaries of several recent NMR investigations will be presented, including water and proton transport in nanocomposite PEM fuel cells membranes, single crystal studies of LiMPO4 (M = Fe, Co, Ni) cathodes, electrode passivation in lithium ion batteries, and structural aspects of CFx primary lithium battery cathodes.

The dipole moment of a water molecule in liquid water differs from that of the isolated molecule because each molecule is further polarized by the electric field of its neighbours. In the lecture an analytical formula for the spatial dependence of the relative permittivity of an electrolyte near a highly charged surface is obtained in which the excluded volume and mutual influence of the water molecules is taken into account. The orientational ordering of water dipoles is considered in the saturation regime. Based on the formula derived for the spatial dependence of relative permittivity it is predicted that the relative permittivity of an electrolyte solution near the highly charged surface (i.e. the in saturation regime) may be substantially decreased due to orientational ordering of water (saturation effect) and depletion of water molecules (depletion effect) due to accumulation of counterions.