I cannot give a answer to that. Storing the cell at higher voltage will wear the cell down faster, but fast charging at high voltage will also wear the cell down.
Algorithms to fast charge LiIon cells uses a high current for the initial part of the charge, then reduces the current when the cell is partly charged (This has nothing to do with CC/CV charging). Research has show that high current will not reduce lifetime when the cell is at a low charge state.
The cutoff voltage around 2.75V or 3.0V is a kind of standard for the rechargeable 3.7V battery cell, mainly determined by the IC of the protection PCB for the battery pack. As flydiver wrote: I try to keep the voltage above 3.0v at all times and generally above 3.2v. There is VERY little capacity under 3.0v and the volts drop precipitously after that making it a slippery slope. Once the cell voltage goes under 2.5 it gets dicey, below 2.0V it will cause permanent damage,can not be recharged any more.
From our long-term experience in the rechargeable battery industry, the cutoff voltage is affected largely by the discharging current as well, just as the charging cutoff, and a voltage recovery immediately after the cutting-off.
The ones I tested had considerable lower cut-off than that (In the 2.0 to 2.5V range): Discharge protection test
And the cut-off was always at exactly the same voltage, independent of current. It also makes the most sense, it would be fairly complicated to adjust the cut-off voltage depending on current drain.
Note: My test is for single cell protection, not for battery packs.
Many thanks for your details. Yes, you are right, the testing results from our engineering department are usually for the complete battery packs with protection PCB, which seems quite different from your testing results. However, all your testing about the battery cells and chargers can be a perfect reference for our customers to get a most suitable charger for their battery packs.
Since there are so many Li-ion 18650 battery cells from difefrent cell manufacturers, that can be available for lighting systems, is it possible for you to test them for the cycling performance, or do you happen to have the cycling results for some battery cells? Thank you in advance.
