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CATEGORIES:Engineering - Mechanics and Materials Seminar Seri
 es
SUMMARY:Current-Induced Stresses in Ceramic Lithium-Ion Co
 nductors - Professor Charles Monroe\, Energy and P
 ower Group Oxford University
DTSTART;TZID=Europe/London:20180216T140000
DTEND;TZID=Europe/London:20180216T150000
UID:TALK97735AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/97735
DESCRIPTION:Ceramic electrolytes are of interest for next-gene
 ration batteries because they suppress morphologic
 al instability when lithium plates at the lithium-
 metal/electrolyte interface. Lithium-ion-conductiv
 e garnet oxides based on Li7La3Zr2O12 (LLZO) have 
 room-temperature conductivity approaching 1 mS/cm\
 ; various dopants ensure thermodynamic stability a
 gainst lithium metal. Cations move through the cry
 stal lattice of LLZO with near-unit transference. 
 The shear modulus of LLZO is of the order of 50 GP
 a\, well above the ~8 GPa needed for morphological
 ly stable deposition. Despite these favorable prop
 erties\, LLZO surprisingly still exhibits a ‘criti
 cal current’\, above which lithium dendrites form.
 \n\nOur group has put significant effort into deve
 loping consistent electrochemical models to descri
 be electrolytes of various types\, including liqui
 ds\, ionomer gels\, glasses\, and ceramics. We hav
 e extended multicomponent transport theory to acco
 unt for excluded-volume effects\, which arise from
  considering the thermodynamics of a material’s de
 nsity\, and have used principles of irreversible t
 hermodynamics to produce transport constitutive la
 ws whose application can illustrate the mechanical
  consequences of viscous drag in liquid electrolyt
 es and space charging at the interfaces of ceramic
 s. \n\nThis talk will summarize our recent progres
 s toward a theory that rationalizes the critical c
 urrent of LLZO in electromechanical terms. We desc
 ribe a variety of new measurements that help to ch
 aracterize elastic solid electrolytes\, lay out th
 e modifications of familiar transport laws that ar
 e needed to account rigorously for the energetic i
 mpact of electrolyte elasticity\, and examine how 
 electrochemical/mechanical coupling affects practi
 cal data such as impedance spectra. Interfaces are
  found to affect critical currents by changing the
  balance of bulk ohmic loss and capacitive surface
  charging\, the latter of which leads to stresses 
 within the material. Our theory produces scaling l
 aws that agree well with experiments\, predicting 
 how the critical current varies with temperature a
 nd interfacial properties.
LOCATION:Oatley Seminar Room\, Department of Engineering
CONTACT:Hilde Hambro
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