I assembeled half coin cells with graphite anode and lithium chip. The OCV of coin cell as assembeled was around 2 - 2.5 V (data based on more than 10 cells) and after fortmation cycles (3 cycles at C/10 with 0.10 to 2 V) reduced to 1-1.1 V. Why OCV changed so much? Is it because of SEI formation? This is two electrode system so I belive the OCV is the potential diference between the cathode and anode and Lithium has a standard potential -3.04 V vs SHE.
SEI could play a role. The potential of each electrode may also change due to irreversible reactions during cycling. For example, Any oxygen functional groups on the graphite may undergo irreversible changes. Also, many electrolyte solutions form HF if exposed to moisture, which degrades the electrodes and possible the OCV. Also, lithium may not deintercalate from graphite defects.
Jacob Bagley Thank you. I didn't see much decay in the capacity though. I agreed that there might be some HF formation from LiPF6 electrolyte.
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