Hello !
I fabricated lithium-ion half cells (silicon anodes and lithium metal) with LP30 +2% FEC as the electrolyte solution and tested galvanostatically at C/10 rate. After 5 cycles, there was a rest for 10 hours and then I took strange curves at delithiation state (C/10 rate). Is there any idea about that ?
P.S
I would like to mention that the temperature of the lab is stable at around 23oC.
I have also noticed that sometimes, high c-rates "recover" the curves to initial behavior.
comments please !
Thank you for your time !
Dear Ioannis Gkionis,
this kind of behaviour might be related to internal short-circuiting of the cell. Sometimes, due to lithium plating and dendrite formation on the counter electrode, the counter and working electrodes are short-circuited through the separator, which causes a rapid internal discharge process, drop in the working electrode potential value and internal circuit break.
If the problem persist in every cell you test, I would suggest checking the contamination level of your glove box and the materials used for cell preparations, as the contaminants (in electrolyte, lithium foil and so on) might affect the stability of SEI layer and enhance dendrite evolution.
Best regards,
MK.
Dear Michal Krajewski,
Thank you very much for your response !
This is something that should be further investigated.
Best regards,
Ioannis Gkionis
Michal is right about lithium plating if you are lithiating your silicon electrodes up to its maximum limit and once there is a short circuit, electrode die very rapidly. Do you observe that? Can you share the lower potential limits? Additionally are you using bulk or nano-silicon? From the profile it looks bulk?
I think, after multiple cycling you are destroying the structure of your electrode which exposes the current collector, allowing lithium plating. During de-lithiation you are extracting lithium from silicon but at 0.7 V you starts to strip lithium which gives you this abnormal profile. I have no reference in favor of my claim but I also witnessed the same abnormal profile and this is the explaination i came up with.
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