As shown in this discharge voltage-capacity diagram, an irregular upward voltage reversal occurs at the beginning of the discharge process. What could be the cause, and how could it be prevented?
The chemistry in the anode of the 18650 battery is graphite, while the cathode is nickel-rich. Ioannis Samaras
Hello, are you sure this data originates from a discharge cycle? An easy explanation would be voltage relaxation at the end of a charging cycle after going from a high c-rate to a low c-rate.
Else it could be a poor estimation of the open-circuit voltage (I assume this is the OCV-capacity graph)? This is more likely to have errors in the beginning and end of the SOC. Do you have the c-rate data to go along with this graph?
Dear Shayan Javanmardi ,
for a commercial (18650 brand?, and/or link?) battery, you must say more, e.g. about its' previous charge/discharge/relaxation (note SOH?) 'historical' phases and other possible treetments, at least, just before this isolated/cropped (your diagram: 'Layout1.tif') discharging (C-rate ?) phase.
May be you have Lithium plating. Otherwise discharge current was programmed from High to low for a fraction of second.
Yes, it is the original data, and I should mention that there is an interval for relaxation after charging and before beginning to discharge.
The c rate is around C/2, but I believe that the amount of conductive additive is insufficient, causing the IR drop from the high resistance in the electrode to create the problem here, resulting in a rapid drop. In terms of lithium plating, I'm not sure. Based on the (dV/dQ) plot, we can detect some similarities, but the slop of the curve for capacity voltage is positive, which is unusual to the extent that I know of.
I should open the cell to examine if there is lithium plating or not for additional investigation. I will share more once I realize the explanation. Thank to everyone who responded to this topic. Surajit Sengupta Ioannis Samaras Djef Brak
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