I have few similar prismatic LFP cells but from two different batches. After discharging them at the same C-Rate and after disconnecting them from the load, the voltage recoveries read different values. The ones from one batch have a voltage recovery of 0.4 V, while the ones from the other batch around 0.2 V. Same chemistries, capacities, voltages etc. Now, the most common suspicion would be to say that it is because of the internal resistance, which I'm sure has some contribution. But can this be the only parameter that can cause this difference? I am also thinking about the overpotentials, but I am not sure. Does anyone have any experience with this?
In my point of view, the potential recovery is all about equilibrium. So I think the reason for the different recoveries in your case is from the different delithiation levels in the LFP, even though the difference is likely to be very small based on your description. Another reason might be from the lithium anode side. A slight contamination or something might also affect the equilibrium.
Good luck!
Thank you for the answer. I also suspect that some kind of contamination is what causes this behavior. I have measured the ohmic internal resistances and they seem to be the same, so there must be something else inside the structure slowing down the diffusion. I will measure the impedance using EIS soon and see if this can reveal something.
Depending on the viscosity of the electrolyte and your pore sizes and the electrode manufacturing, the wettability of the electrodes might be important to consider.
Sometimes your glovebox might be warmer, sometimes the electrolyte is more or less viscous. There are many conditions that one is not able to keep equal. Your electrodes are then differently wetted. If you just test for some cycles, your electrodes will show often different behaviours.
Normally, you can put the cells to an equilibrium by some cycles of 0.1C Charge-Discharge or some loops of 1 mV/s CV.
Did you measure impedance of your cells? (If the internal resistance is very off, then it will have certainly a huge effect on your cells) I think for academia 2-5 Ohm of scattering is okay, but more will lead to different results.
Is your cycler/potentiostat placed in a climatized room or in a climatic chamber?
(Different temperatures affect self-discharge rates and potentials)
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