I'm stating to assembly LFP | 1M LiPF6 in EC:DC electrolyte | Graphite pouch cells for practicing.
I started to charge the pouch at C/20 CCCV until 3.8V. The battery was able to charge, but know it can't perform discharge, as it reaches 0V in a second. Why is the battery not discharging?
Hello Natsalia,
first of all, it seem you should clarify your testing situation a little bit more, for example
1. All material used in cell preparation, are commercial or one or more than one parts have been synthesized/ prepared by yourself?
2. have you ever tested your LFP in half cell? did it show good performance in half cell?
3. has your pouch cell shown a flat plateau at 3.1 V vs Graphite, (or can you share an image of charging graph?
Hossein Ghafarian-Zahmatkesh thank you for your answer.
1. All materials are comercial, except for the electrolyte (some cells are done with 1M LiPF6 in EC:DMC and others are with a synthesized IL. I get the same results with both...
2. I've tested LFP in half cell and it is working.
3. When I assemble the pouch I get an OCV after assembly of +- 100 mV. I left the cell resting for 24h prior to preconditioning.
Then I start a c/20 CCCV charge. I can't get a discharge though...
However, after charging i'm able to light up leds and mantain the voltage at rest ...
I don't know if i'm preconditioning well the cells.
Hi again,
It seems you have some impurities in your electrolyte or in your battery cell, because you should have a flat plateau in charging of battery.
Have you done any test with a commercial electrolyte? If I suggested right, the 1M EC:DMC should be commercial electrolyte. If so, is that sample has shown the same charging graph as well?
I can say based on my suggestion that if you have had the same problem with commercial electrolyte, it seems you might have some air trapped in your cell while sealing. in addition I can see a high internal resistance in the charging graph of your cell.
I forgot to add more potential error that might happen while your are going from coin cell to pouch cell.
electrode calendering, it cannot show much effect in coin cell stage because of its smaller surface area compared to pouch cell
Hello Natsalia,
you might have a (quasi) 'short-circuit' from (a small number of) pin holes inside your (thin?) separator. In that case, applying a double separator(s) might save the initial life of your preparatory/pilot pouch cell(s).
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