I am making Li half cells using NMC as cathode. The OCV is around 3 V but it self discharges and during charging the voltage increases to 3.5 V and then drops to 3.3-3.4 V and stays there. I have tried using two separators but the same low voltage plateau happens again. I have tried also different electrolytes and different electrodes. Has anyone see something similar? Thank you very much.
Dear Ioanna Maria Pateli ,
say more, please, what is the origin of your NMC material (cells and electrodes) ?
Also, undertake, please, some,
1) CVL, and/or
2) EIS[1] spectra,
as additional (diagnostic) measurements.
1. Include some V_DC polarization(s) values (in EIS) within the range (3.3-3.5) V, beyond the initial (common, reference) value of V_DC=OCV.
Hi Ioanna Maria Pateli,
more information please,
Is it a commercial NMC cathode or lab-made? If lab-made, what conductive additive are you using? Also, did you dry your electrodes properly?
Try charging at a higher rate initially and then holding at a higher cut-off voltage for 2-3 hours to reach the theoretical capacity you're expecting. Then try discharging.
Also, as Ioannis Samaras suggested please try to other characterizations including a CV.
Any suggestions Binson Babu , Shruti Suriyakumar , Vadivel Selvamani
Hi Ioanna Maria Pateli , As mentioned Vishnu Surendran pls give more details about that like, the as recorded profile.
In general the electrolyte reactivity is the major cause of self-discharge, especially with lithium metal. in addition, contaminated electrode also leads to self-discharge. For Ni-rich system, high temperature drying is mandate and storing under inert condition too. Common surface contamination of native oxide/carbonates leads a shoulder at the beginning (breaking of surface residues) followed by regular electrochemical signature, where the electrochemical reaction starts at > 3.6 V vs Li+/Li. share the electrochemical details to resolve the issue, further.
If it is in-house developed on, then ensure the XRD pattern
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