The question centers around how to read the capacity loss graph on page 7
At first glance, the 75-65 cycle seems to be the best for the battery, but you need to normalize it for work done: a 50% depth of discharge cycle does 5 times more work, 1000 cycles of 10% is 100 full cycles. This is labeled as work done in the table below.
SoD / EoD: start and end of discharge.
DoD: depth of discharge, SoD - EoD.
Cap % at 4k: capacity lost at 4000 DST cycles.
Work done: 4000 * DoD / 100%.
Cap loss per 1k work done: capacity loss per 1000 full cycles. 1000 cycles is about the full life time of a phone, about 3 years of 1 full charge a day.
|SoD||EoD||DoD||Cap % at 4k||Cap loss||Work done||Cap loss per 1k work|
As you can see, in this model, the loss is with the 100-25 cycle, or alternatively, the 75-25 cycle. It is unfortunate this information is so hidden in this paper.
Also, note that this test was done with a 3.3V nominal voltage cell, which is not a standard Li-ion cell, that chemistry is 3.7/3.8V, so findings do not always transfer.
Xu, B., Oudalov, A., Ulbig, A., Andersson, G., & Kirschen, D. S. (2018). Modeling of Lithium-Ion Battery Degradation for Cell Life Assessment. IEEE Transactions on Smart Grid, 9(2), 1131-1140. doi:10.1109/tsg.2016.2578950