I assembled the coin cell in glove-box and my electrodes and seperator had not problem. I think the self-discharge is related to formation process of coin cell.
Dear Mohammad,
It is very hard to say without knowing much about the cell. How did you know that you have self-discharge? Are you monitoring the OCV? If your OCV keeps reducing after cell assembly, it means that your cell is reaching to its equilibrium and it should be stable after a couple of hours.This could be due to the insufficient soaking of your separator or cathode/anodes with electrolyte. What is your cell chemistry (anode, cathode, and electrolyte)?
Dear Amir,
I assembled a full cell with NCA (cathode) and graphite(anode) electrodes. its OCV is abou 300 mV immediately after the assembling. this OCV is almost stable. I want to do the formation process of this coin cell so that its voltage be stable after charging.
Dear Mohammad,
The self discharge is possible only in the case if the electrodes are not separated properly. In your first question you are talking about some Li coin but in the next one you are using graphite as anode. Please make your question more simple. However, it is understood that self discharge can occur due to short circuit. Do you mean metallic Li as anode from Li coin?
From my experience the reasons are due to the connections and parasitic effects of capacitance due to packaging and the effects of inductance and resistance due to connecting leads. A picture of the actual assembly will shed more light to this. Also, if you monitor the self-discharge (voltage) then we can easily model this behavior and prove it via simulation.
Normally, we use a single (separator[1]) layer, a thin (as thin as possible) porous membrane[1] that physically separates[2] the anode and cathode. In order to exclude the case, that the separator is the reason for your problem, then try to assemble two more (new test) Li-ion coin cells. One using 2 separators, and one more using 3 separators.
1. What is the Function of the Separator? http://batteryuniversity.com/learn/article/bu_306_battery_separators
2. The Role of Separators in Lithium-Ion Cell Safety http://www.electrochem.org/dl/interface/sum/sum12/sum12_p061_065.pdf
I'm new use the coin cell for electrochemical testing, I want to know how to unpack an used coin cell without destroy the case.
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