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SUMMARY:Energy Storage and Conversion:  Using Local Structural Probes to U
 nderstand and Optimise Function of Battery and Fuel Cell Materials - Clare
  Grey (University of Cambridge/SUNY Stony Brook)
DTSTART:20100118T160000Z
DTEND:20100118T170000Z
UID:TALK20390@talks.cam.ac.uk
CONTACT:Ian Farnan
DESCRIPTION:The application of new Nuclear Magnetic Resonance (NMR) approa
 ches to correlate structure and dynamics with function in materials lithiu
 m-ion batteries and solid oxide fuel cells will be described.  A particula
 r focus is the development of methodology to allow these systems to be inv
 estigated in-situ\, i.e.\, under realistic operating conditions.  This all
 ows processes to be captured\, which are very difficult to detect directly
  by ex-situ methods.  For example\, we can detect side reactions involving
  the electrolyte and the electrode materials\, and processes that occur du
 ring extremely fast charging and discharging.  The approach will be demons
 trated for the anode material silicon.  Lithium-ion batteries (LIBs) conta
 ining silicon have been the subject of much recent investigation\, because
  of the extremely large gravimetric and volumetric capacity of this anode 
 material.  This material undergoes a crystalline-to-amorphous phase transi
 tion on electrochemical Li insertion into crystalline Si\, during the firs
 t discharge\, hindering attempts to link structure in these systems with e
 lectrochemical performance.  We apply a combination of static\, in-situ an
 d magic angle sample spinning\, ex-situ 7Li and 29Si nuclear magnetic reso
 nance and pair distribution function analysis studies to investigate the c
 hanges in local structure that occur in the actual working LIB.  The first
  discharge occurs via the formation of isolated Si ions and smaller Si-Si 
 clusters embedded in a Li-ion matrix\; the latter are broken apart at the 
 end of the discharge forming isolated Si ions.  In a second example\, we i
 llustrate the use of NMR to investigate the nature of the defects in mater
 ials that have been proposed for use as electrolytes that operate via eith
 er oxygen-ion or protonic conduction in solid oxide fuel cells.  For examp
 le\, BaZrO3 or BaSnO3 can be doped with Y3+ to create oxygen vacancies.  T
 hese vacancies can be filled with H2O\, the water molecules dissociating t
 o form mobile ions that contribute to the long-range ionic transport in th
 ese systems.  NMR experiments are used to examine the local structure\, th
 e locations of the vacancies and how this affects protonic/oxygen ion moti
 on in these systems.  
LOCATION:Harker 2 lecture room\, Department of Earth Sciences\, Downing Si
 te
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