I've seen plenty of studies that reference degradation due to low SoC (high DoD) during use; li-ion isn't NiMH. Battery University has a summary:
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
Similar to a mechanical device that wears out faster with heavy use, the depth of discharge (DoD) determines the cycle count of the battery. The smaller the discharge (low DoD), the longer the battery will last. If at all possible, avoid full discharges and charge the battery more often between uses. Partial discharge on Li-ion is fine. There is no memory and the battery does not need periodic full discharge cycles to prolong life. The exception may be a periodic calibration of the fuel gauge on a smart battery or intelligent device. (See BU-603: How to Calibrate a “Smart” Battery)
The following tables indicate stress related capacity losses on cobalt-based lithium-ion. The voltages of lithium iron phosphate and lithium titanate are lower and do not apply to the voltage references given.
Note: Tables 2, 3 and 4 indicate general aging trends of common cobalt-based Li-ion batteries on depth-of-discharge, temperature and charge levels, Table 6 further looks at capacity loss when operating within given and discharge bandwidths. The tables do not address ultra-fast charging and high load discharges that will shorten battery life. Not all batteries behave the same.
Table 2 estimates the number of discharge/charge cycles Li-ion can deliver at various DoD levels before the battery capacity drops to 70 percent. DoD constitutes a full charge followed by a discharge to the indicated state-of-charge (SoC) level in the table.
Depth of discharge
Discharge cycles
(NMC / LiPO4)
Table 2: Cycle life as a function of
depth of discharge. A partial discharge reduces stress and prolongs battery life, so does a partial charge. Elevated temperature and high currents also affect cycle life.
Note: 100% DoD is a full cycle; 10% is very brief. Cycling in mid-state-of-charge would have best longevity.
100% DoD ~300 / 600
80% DoD ~400 / 900
60% DoD ~600 / 1,500
40% DoD ~1,500 / 3,000
20% DoD ~1,500 / 9,000
10% DoD ~10,000 / 15,000
Lithium-ion suffers from stress when exposed to heat, so does keeping a cell at a high charge voltage. A battery dwelling above 30°C (86°F) is considered elevated temperature and for most Li-ion a voltage above 4.10V/cell is deemed as high voltage. Exposing the battery to high temperature and dwelling in a full state-of-charge for an extended time can be more stressful than cycling. Table 3 demonstrates capacity loss as a function of temperature and SoC. . . .
For long term storage (9-10 months in the case of the study below) the situation seems less clear, and dependent on specific Li-ion chemistry. This study from 2016 compares NCA, NMC and LFP at various temps, and SoCs from 0 to 100%:
Calendar Aging of Lithium-Ion Batteries
http://jes.ecsdl.org/content/163/9/A1872/F2.expansion.html
General aging behavior.—For the three types of lithium-ion cells
examined, Figures 2a–2c show the capacity fade after a storage period
of 9–10 months. As expected, they all exhibit an increased calendar aging
with higher storage temperature. However, no steadily increasing
degradation with SoC is observed. Instead, there are plateau regions,
covering SoC intervals of more than 20%–30% of the cell capacity,
in which the capacity fade is similar. A marked step in the capacity
curves is observed at about 60% SoC for the NCA and NMC cells
and above 70% SoC for the LFP cells. For the observed relationships
between storage SoC and capacity fade, no simple linear, polynomial,
or exponential approximations are possible without considerable deviation
in certain SoC regions. Hence, the measurement of calendaraging for only
three SoCs, as is the case in most publications, is not sufficient to precisely
describe calendar aging with respect to the SoC when the qualitative
characteristics over the entire SoC range are not known. . . .
There seems to be little difference between storage at 0% and 30% SoC for most of the chemistries.
FWIW, Jeff Dahn recently recommended keeping the battery between 30-70% when possible, but charging to 100% for trips as needed. See the tmc thread on that:
https://teslamotorsclub.com/tmc/thr...tion-on-long-term-battery-preservation.97134/
I've long seen 30 deg. C (86 deg. F) as given by the BU quote above as the general point at and above which li-ion heat-related degradation accelerates rapidly. Probably the specific chemistry used will move the temp slightly one way or the other, but I doubt it changes the general point.