Hello!
I just started learning battery research. I'm working on to get myself used to coin cell assembly process and to achieve reproducibility of sample preparation.
Here's my coin cell performance protocols in general:
OCP for 24 hours
initial five cycles (2.0 - 3.7 V vs. Li/Li+) at C/5 rate, charging -> discharging
Following cycles at different C rates (faster)
Then I realized that ~1/3 of coin cells has an issue during first charging cycle.
I understand slight discrepancy between each cells in regards with OCV.
However, the 1/3 of coin cells are charging for too long and never approach 3.7V.
For successful cells, it takes
So it looks like there are many issues here:
1. Quite obvious, but make sure you're assembling the coin cells inside a Ar-filled glove box (N2 reacts with Li metal).
2. In line with the previous one, make sure you're using a high quality electrolyte. If you buy the prepared electrolytes make sure they are not exposed to air at any point, as they absorb water. If you prepare the electrolyte yourself, make sure to dry the solvents in advance using activated molecular sieves. The peak at the beginning of charge evidences some passivation of the Li-metal which makes me think that your electrolyte is not pure, which can also result in a "eternal charge" that you describe in some cells.
3. Make sure you scratch the surface of the Li-metal right before assembling the cell. You want a shinny surface and normally Li surface gets passivated easily even if stored under insert atmosphere.
I hope it helps
it's happen to me one time and the problem was because my battery was not well assembly , i had the problem with electrolyte .
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