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SUMMARY:Current-Induced Stresses in Ceramic Lithium-Ion Conductors - Profe
 ssor Charles Monroe\, Energy and Power Group Oxford University
DTSTART:20180216T140000Z
DTEND:20180216T150000Z
UID:TALK97735@talks.cam.ac.uk
CONTACT:Hilde Hambro
DESCRIPTION:Ceramic electrolytes are of interest for next-generation batte
 ries because they suppress morphological instability when lithium plates a
 t the lithium-metal/electrolyte interface. Lithium-ion-conductive garnet o
 xides based on Li7La3Zr2O12 (LLZO) have room-temperature conductivity appr
 oaching 1 mS/cm\; various dopants ensure thermodynamic stability against l
 ithium metal. Cations move through the crystal lattice of LLZO with near-u
 nit transference. The shear modulus of LLZO is of the order of 50 GPa\, we
 ll above the ~8 GPa needed for morphologically stable deposition. Despite 
 these favorable properties\, LLZO surprisingly still exhibits a ‘critica
 l current’\, above which lithium dendrites form.\n\nOur group has put si
 gnificant effort into developing consistent electrochemical models to desc
 ribe electrolytes of various types\, including liquids\, ionomer gels\, gl
 asses\, and ceramics. We have extended multicomponent transport theory to 
 account for excluded-volume effects\, which arise from considering the the
 rmodynamics of a material’s density\, and have used principles of irreve
 rsible thermodynamics to produce transport constitutive laws whose applica
 tion can illustrate the mechanical consequences of viscous drag in liquid 
 electrolytes and space charging at the interfaces of ceramics. \n\nThis ta
 lk will summarize our recent progress toward a theory that rationalizes th
 e critical current of LLZO in electromechanical terms. We describe a varie
 ty of new measurements that help to characterize elastic solid electrolyte
 s\, lay out the modifications of familiar transport laws that are needed t
 o account rigorously for the energetic impact of electrolyte elasticity\, 
 and examine how electrochemical/mechanical coupling affects practical data
  such as impedance spectra. Interfaces are found to affect critical curren
 ts by changing the balance of bulk ohmic loss and capacitive surface charg
 ing\, the latter of which leads to stresses within the material. Our theor
 y produces scaling laws that agree well with experiments\, predicting how 
 the critical current varies with temperature and interfacial properties.
LOCATION:Oatley Seminar Room\, Department of Engineering
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