In Feb. 2008, OCW posted a 2006 interview with Prof. Ortiz.

In Feb. 2008, OCW posted a 2006 interview with Prof. Suresh.

Downsizing Matter: Impact On Electrochemical Energy Conversion And Storage

Speaker: Joachim Maier, Max Planck Institute for Solid State Research

Time: 3:30p-4:30p

Location: Chipman Room, 6-104

While size effects on electronic transport properties are quite well studied and led to the acknowledged field of nano-electronics, this contribution will essentially be concerned with the effects on ion transport. Ion conduction enables a palette of applications in particular in the field of energy research that cannot be rendered dispensable by using electrons. Examples are chemical sensors, fuel cells and batteries. Here nanostructuring can have a substantial impact. It will be shown that by the introduction of interfaces and the variation of their spacing not only drastic changes in conductivities but also qualitative changes can be achieved: insulators can be turned into conductors, electronic conductors into ion conductors, anion into cation conductors and interstitial into vacancy conductors. The use of true size effects leads to the generation of artificial mesoscopic ion conductors. In addition to transport also storage and reactivities are severely influenced. This is not only significant for fundamental research but also for electrochemical devices. In particular in the field of Li-batteries nano-ionics is demonstrated to be of great potential.

NEW GENERATION LITHIUM-ION BATTERIES
Bruno Scrosati
Dipartimento di Chimica, Università di Roma “La Sapienza”, 00185 Rome, Italy.

Friday, February 27
11 a.m.
Room 3-133

Great research efforts have been lately directed to the development of lithium ion batteries suitable for application as electrical intermittent energy (EES) storage systems as well as power sources for low emission hybrid vehicles (HEVs), or even for no emission, electric vehicles (EVs). However, a successful use in these fields requires the upgrading of the performances of the batteries in terms of energy density, cheapness and, particularly safety. The energy content may be enhanced by passing from the present structure to innovative chemistries involving advanced electrode materials. In this respect, the lithium metal alloys have received large attention due to their very high specific capacity. However, these materials, which are considered as very appealing negatives electrodes to be exploited in replacement of conventional graphite, suffer of large volume expansion and contraction during the charge-discharge cycling, this inducing mechanical disintegration which in turn results in a very poor cycle life. The approach carried out in our laboratory to control this issue has been focused on revolutionary Sn-C nanocomposite structures. These novel electrodes operate at high rates and high capacity with a life extending over several hundreds cycles and thus, they can be successfully used as anodes in advanced lithium-ion battery types. The safety issue is, among other factors, associated to the common liquid organic electrolytes, which are volatile and flammable. Thus, a promising approach for improving safety is in the use of alternative electrolytes based on more thermally stable solvents. Ideal in this respect are ionic liquids, ILs, namely room temperature molten salts, since they are highly conductive, non-volatile and stable up to high temperatures. However, the electrochemistry of IL-based solutions is not totally clear, especially in terms of their compatibility with the electrode materials. A systematic study has been carried out in our laboratory to investigate various classes of ionic liquid solutions and their suitability for lithium battery application.

The DMSE Community is invited to the first Lunch N Lecture* of the Spring semester with Professor Craig Carter. Pizza and refreshments will be served!

Kinetics of Micelle Formation Below the Critical Micelle Concentration
Speaker: Craig Carter
Professor of Materials Science and Engineering
Date: Tuesday, February 24th
Time: 12:00pm-1:00pm (pizza and refreshments will be served at 11:40am)
Location: The Chipman Room (6-104)

Abstract:
At amphiphilic surfactant concentrations above the critical micelle concentration (CMC), the stable micelle morphology has been predicted and is observed as a function of concentration and intrinsic micelle curvature. The kinetics of evolution from micelle nucleation to the stable morphology is much more complicated.

A phase field method to simulate morphological transitions of interfaces in soft materials such as surfactant self-assembled structures is developed and simulations are presented. The model captures both self-assembly of micelles and the effect of interface-curvature elastic-energy on their morphologies. Simulations of single micelle growth in dilute solutions reveal several previously unknown morphological transitions, including a disk-to-cylinder transition and a tip-splitting instability of cylindrical micelles. We propose that these morphological instabilities provide for the branched micelle structures, which have been observed and have significant effects on the rheological properties of solutions.

(This work has been done in collaboration with Ming Tang, LLNL)

*The MRS “Lunch N Lecture” is a series of informal talks from any faculty member whose research interests are in materials. To learn more about the MRS and its lecture series, please visit the chapter homepage. Want to see a particular faculty member give a talk? E-mail the MRS officers at mrschapter.officers [at] mit.edu and give us suggestions!