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     COLLOQUIUM OF THE COMPUTATIONAL MATERIALS SCIENCE CENTER
   AND THE SCHOOL OF PHYSICS, ASTRONOMY AND COMPUTATIONAL SCIENCES
                       (CSI 898-Sec 001)
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          Using computational design to make rechargeable 
               batteries smaller, faster and lighter

                            Michelle Johannes
             Center for Computational Materials Science 
              Naval Research Laboratory, Washington DC

Rchargeable Li ion batteries supply the energy for most of today's portable
devices, including cell phones, laptops, GPS systems and power tools.  The
emphasis on portability requires that batteries be light, quickly
rechargeable, able to be cycled many times and preferably, cheap.  Many of
these conditions are addressed by the constituent materials of the battery 
(the anode, cathode and electrolyte), rather than the battery design.
Computational methods have proven to be extremely useful in elucidating how
and why some materials make better electrodes than others.  In this talk, I
will discuss the common materials used for Li ion rechargeable batteries, with
an emphasis on the physics and chemistry that determine their strengths
and weaknesses.  Phenomena such as phase transitions, magnetic ordering, and
transport (electronic and ionic) are all calculable using density
functional theory and all can effect the suitability of a material for battery
operation.  Since cathode materials are primarily transition metal oxides
and phosphates, the rich physics that characterizes these classes (magnetism,
magnetoresistance, Mott-insulator transitions, orbital ordering, etc..) is
present. I will talk about calculations of the electronic structure for
several common cathode materials, and particularly how experiment and
computation together can guide the development of better materials. Anodes are
predominantly composed of single component materials, such as carbon, Sn,
or Si (though transition metal oxides can be used too).  I will briefly
discuss what limits the usage of these materials and what directions can be
taken to improve them in the future.

                      Monday, April 4, 2011
                               4:30 pm
                    Room 301, Research I, Fairfax Campus

Refreshments will be served at 4:15 PM.
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Find the schedule at http://cmasc.gmu.edu/seminar/schedule.html