IJS KOLOKVIJ, sreda 17. 4. 2019, ob 13.00 uri, prof. dr. Laurent Pilon

[Natasa Gosevac]

Vabimo vas na 16. predavanje iz sklopa "Kolokviji na IJS" v letu 2018/19, ki
bo v sredo, 17. aprila 2019, ob 13 uri v Veliki predavalnici Instituta
>Jožef Stefan<  na Jamovi cesti 39 v Ljubljani. Napovednik predavanja
najdete tudi na naslovu http://www.ijs.si/ijsw/Koledar_prireditev, posnetke
preteklih predavanj pa na http://videolectures.net/kolokviji_ijs. 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



prof. dr. Laurent Pilon 

University of California Los Angeles, Los Angeles, ZDA 

 

In operando kalorimetrija v elektrokemijskih kondenzatorjih 

 

Elektrokemijski kondenzatorji so zelo zanimivi kot obetavni sistemi za
shranjevanje električne energije za močnostne aplikacije vključno s
hibridnimi ali popolnoma električnimi vozili in pametnim omrežjem.
Elektrokemijski kondenzatorji shranjujejo energijo s hitrimi redoks
reakcijami in/ali z adsorpcijo ionov v električnem dvosloju na stiku
elektrode in elektrolita v zelo poroznih materialih. Disociirani ioni, ki so
prisotni v elektrolitu, se prenašajo na površino elektrode in iz nje zaradi
kombinacije difuzije in elektrostatičnih sil ter so podvrženi steričnim
efektom. Ti ioni lahko sodelujejo v redoks reakcijah na površini elektrode
ali se v elektrodo interkalirajo. Ta mehanizma shranjevanja sta zelo hitra
in visokoreverzibilna, kar vodi do velike gostote energije in dolgoživosti
kondenzatorja. Obenem pa je napajanje elektrokemijskih kondenzatorjev
povezano s sproščanjem toplote, ki lahko vodi do zelo visokih temperatur,
zaradi česar se kondenzator hitro stara, hitrost samodejnega praznjenja se
poveča, nadzor nad sproščeno toploto pa je skromen.

V predavanju bomo predstavili nov in operando kalorimeter, s katerim lahko
izmerimo trenutni toplotni tok v elektrokemijskih kondenzatorjih med
polnjenjem in praznjenjem. Elektrode, ki smo jih preučevali, so izdelane iz
(i) aktivnega ogljika, ki shranjuje naboj s tvorbo električnega dvosloja, in
iz (ii) raznovrstnih oksidov prehodnih kovin (npr. MnO2 in  MoO2), kjer
pride do shranjevanja zaradi hitrih površinskih redoks reakcij ali
interkalacije ionov litija. Posebno pozornost bomo namenili ločevanju
hitrosti ireverzibilnega in reverzibilnega sproščanja toplote ter ločenemu
merjenju Joulovega gretja od trenutne hitrosti sproščanja toplote, merjene
na vsaki elektrodi. Naposled bomo meritve primerjali z napovedmi fizikalnega
modela, izpeljanega iz prvih principov, ki vključuje prenos naboja na
elektrodi, redoks reakcije in interkalacijo ionov kakor tudi elektrodifuzijo
ionov in sterični odboj v elektrolitu.

 

Predavanje bo v angleščini.

Lepo vabljeni!

 
***********

 

We invite you to the 16th Institute colloquium in the academic year 2018/19.
The colloquium will be held on Wednesday, April 17, 2019 at 13 PM in the
main Institute lecture hall, Jamova 39, Ljubljana. To read the abstract
click   <http://www.ijs.si/ijsw/Koledar_prireditev>
http://www.ijs.si/ijsw/Koledar_prireditev. Past colloquia are posted on
<http://videolectures.net/kolokviji_ijs>
http://videolectures.net/kolokviji_ijs.

********************************************

prof. dr. Laurent Pilon 

University of California Los Angeles, Los Angeles, USA

 

In operando calorimetry in electrochemical capacitors

 

Electrochemical capacitors have attracted significant attention as promising
electrical energy storage systems for high power applications including
hybrid or all-electric vehicles and smart grid. Electrochemical capacitors
store energy via fast redox reactions and/or via ion adsorption in the
electric double layer forming at the electrode/electrolyte interfaces in
highly porous materials. Dissociated ions, present in the electrolyte, are
transported to and from the electrode surface under the combined influence
of diffusion and electrostatic forces and are subject to steric effects.
These ions may engage in redox reactions at the surface of the electrode
materials or intercalate therein. These storage mechanisms are very fast and
highly reversible resulting in large power density and long cycle life.
However, charging electrochemical capacitors results in heat generation
potentially leading to excessively large temperatures responsible for
accelerated aging, increasing self-discharge rates, and thermal runaway. 

This seminar will present a new in operando calorimeter capable of measuring
the instantaneous heat generation rate in electrochemical capacitors under
charging/discharging conditions. The electrodes of the devices investigated
were made of (i) activated carbon storing charges via electric double layer
formation or (ii) various transition metal oxides (e.g., MnO2, MoO2) storing
charges by fast surface redox reactions or lithium ion intercalation.
Particular attention will be paid to distinguish between irreversible and
reversible heat generation rates and to isolate Joule heating from the
instantaneous heat generation rate measured at each electrode. Finally, the
experimental measurements will be compared with predictions by a physical
model derived from first principles and accounting for charge transfer in
the electrode, redox reactions and ion intercalation as well as ion
electrodiffusion and steric repulsions in the electrolyte.

 

Cordially invited!

 

 

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