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SUMMARY:Current Status of Operando-$\\mu^+$SR for Battery Materials at J-P
 ARC
DTSTART;VALUE=DATE-TIME:20220829T152000Z
DTEND;VALUE=DATE-TIME:20220829T154000Z
DTSTAMP;VALUE=DATE-TIME:20220826T110007Z
UID:indico-contribution-3706@indico.stfc.ac.uk
DESCRIPTION:Speakers: Kazuki Ohishi (Neutron Science and Technology Center
 \, CROSS)\nIon transport in solids is a key feature for the operation of i
 on batteries. There are two parameters for describing ion transport in bat
 tery materials\; one is a self-diffusion coefficient ($D^J$) and the other
  is a chemical diffusion coefficient ($D^C$). The former diffusion is caus
 ed by thermally activated fluctuation of ions\, while the latter diffusion
  is caused by a flow due to a concentration gradient of ions. Majority of 
 work concerning battery materials\, $D^C$ has been measured with an electr
 ochemical technique under a concentration gradient of the ion in a half-ce
 ll. $D^C$ is then estimated using the relationship: $D^C=\\Theta D^J$\, in
  which $\\Theta$ denotes a thermodynamic factor.\nAccording to the Cottrel
 l equation\, the time evolution of the current of the planer electrode in 
 the half-cell under an ion-concentration-gradient has a relation\, $I(t)\\
 propto A_{re}\\sqrt{D^C}C$\, where $A_{re}$ and $C$ denote the reactive su
 rface area of the electrode and the concentration of the ion. Thus\, the o
 btained value from the electrochemical measurement is not $D^C$ but $D^C A
 _{re}^2$. Because the correct $A_{re}$ in liquid or solid electrolytes is 
 unknown\, it is very difficult to determine $D^C$. We have thus initiated 
 series of experiments to measure intrinsic $D^J$ of battery materials with
  $\\mu^+$SR [1]. Due to the change in the crystal structure and occupancy 
 of a regular Li site with SOC\, $D^J$ is predicted to depend on SOC [2]. T
 herefore\, it is highly desirable to measure $D^J$ as a function of SOC un
 der working condition\, namely\, an operando $\\mu^+$SR. We are attempting
  to establish such technique in J-PARC\, and show the current status.\n\n[
 1] For example\, J. Sugiyama et al.\, Phys. Rev. Lett. 103\, 147601 (2009)
 .\n[2] A. Van der Ven and G. Ceder\, Electorchem Solid-State Lett. 3\, 301
  (2000).\n\nhttps://indico.stfc.ac.uk/event/53/contributions/3706/
LOCATION:Science and Technology Campus\, University of Parma
URL:https://indico.stfc.ac.uk/event/53/contributions/3706/
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