Dear readers, I am studying sulfur battery cathodes. For this, I am trying to study the active material which consists of 80% sublimed sulfur+10% conductive carbon black+10% PE (Mw=4000). I proceed always by preparing the slurry in chloroform and then doctor blade the paste on graphite sheets with a known geometric surface area. Afterwards, the prepared cathode is studied by cyclic voltammetry using a Pt foil as a counter electrode and Ag/AgCl as a reference electrode. I used several solutions such as 0.1M TBAB/DMF; 0.1M LiTFS/(DOL:DME 1/1 v:v) and 0.1M LiClO4/DI water. All these systems didn't allow the observation of the two cathodic peaks and the anodic peak. Can anyone show me the mistake(s) that I am doing and how can I study the sulfur cathode materials using cyclic voltammetry?
Use only a pure (anhydrous) organic Li-electrolyte.
Also, on the occasion that, you apply a 3-electrodes' configuration, in your CV of a Li-cell with (pure organic) Li-electrolyte, replace your (inconsistent with a Li-electrolyte) conflicting RE (Ag/AgCl, as reference electrode) by a pseudo-RE (Pt-wire[1]).
1. Cyclic Voltammetry in Lithium–Sulfur Batteries—Challenges and Opportunities https://onlinelibrary.wiley.com/doi/epdf/10.1002/ente.201801001
Dear Ioannis Samaras , the solvents that I am using are purchased from Sigma Aldrich with low percentage of moisture. Also, I am not performing CV on Li-cells (eventually that's my goal), but currently I trying to understand my material using the classical CV in an electrochemical cell+3 electrodes immersed in the solution of electrolyte.
However[1], you say[2], that you add (on, more[3]) water, dear Amir Bzainia .
1. Your quote: Can anyone show me the mistake(s) that I am doing and how can I study the sulfur cathode materials using cyclic voltammetry ?
2. Your quote: All these systems didn't allow the observation of the two cathodic peaks and the anodic peak.
3. 0.1M LiClO4/DI water: "I used several solutions such as 0.1M TBAB/DMF; 0.1M LiTFS/(DOL:DME 1/1 v:v) and 0.1M LiClO4/DI water."
I agree with you about the aqueous system, but what about the other two systems with organic solvents?
The other two cells (systems with 'organic solvents') have, inappropriately, imported an afield 'RE', Ag/AgCl, as a (floating) reference electrode, because it has different energy (reference) levels, or in other words:
this 'RE' has NOT the same solvent network references (HOMO-LUMO[2]) with the 'WE'.
So, I will say, again: replace this 'RE' by a pseudo-RE (Pt-wire[1]), or even better, apply, mainly, an uncomplicated 2-electrodes' configuration, in your next CVs[3].
1. Cyclic Voltammetry in Lithium–Sulfur Batteries—Challenges and Opportunities https://onlinelibrary.wiley.com/doi/epdf/10.1002/ente.201801001
2. https://en.wikipedia.org/wiki/HOMO_and_LUMO
3. And/then show some plots of these (new) CVs.
Dear Ioannis Samaras , I tried the two electrode set-up and the CV has the same shape as the previous ones using Ag/AgCl... The reference electrode will only "shift" the peaks but will not change the kinetics of the system and create new peaks...
This CV (peaks on Untitled.png) is, just, one more example testing the verification of the remaining (in organic solvents, percentage of) water (splitting, look at the high i-peaks) and the dissolved air (look at very low i-peaks, mainly due to the oxygen content) in samples' solvent[1,2]. Maybe you would like to remake 'better' (extended examples, scalable-tests of) CV(s) using some new cells, inside an inert atmosphere (Ar -) filled GB[3].
Finally, try to follow the recommended Ref.4, in order to save most of your working time.
1. https://www.researchgate.net/post/What_happens_when_I_run_CV_cyclic_voltammetry_without_a_redox_couple
2. Peaks from Dissolved Air in Sample Solvent https://www.shimadzu.com/an/hplc/support/lib/lctalk/37/37lab.html
3. https://en.wikipedia.org/wiki/Glovebox
4. Cyclic Voltammetry in Lithium–Sulfur Batteries—Challenges and Opportunities https://onlinelibrary.wiley.com/doi/epdf/10.1002/ente.201801001
This is what I obtained when I put sulfur (2mM) and TBAB (0.1M) in DMF, used Pt foil as counter electrode and Ag/AgCl as reference electrode. The working electrode is glassy carbon and the scan rate is 50mV/s. The oxygen wasn't removed from the solution prior to measurements.
Dear Dr. Ioannis Samaras , eventually I followed the paper that you suggested ( Cyclic Voltammetry in Lithium–Sulfur Batteries—Challenges and Opportunities https://onlinelibrary.wiley.com/doi/epdf/10.1002/ente.201801001 ) by studying sulfur directly in the electrolyte, and I obtained same peaks as reported in the article. Thanks for guidance.
Seeing like you were able to get what you expected. Sometimes you may also find that The "following" Electrode Processes could probably explain why the expected cathodic or anodic peaks wont show. The reduced or oxidized form of the electro-active species may have shorter lifetimes than voltammetry acquisition times. Eventually , a system that would have been reversible becomes irreversible or quasi
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering
- Powders