This is for lithium ion chemistries, including LCO and NMC, regardless if they are 18650 or prismatic cells. Their rated voltage is usually 3.7 volts, although phone manufacturers like to mark them as 3.8 volt batteries to get a marginal increase in Wh capacity. 3.7 is the nominal voltage, but their actual range is 3-4.2 volts. Most devices shut down around 3.4 volts as there is little energy to obtain by going further down to 3 volts.
Lithium Iron Phosphate batteries, or LiFePO4, have a max charge of 3.6 volts, with a nominal rating of 3.2 volts. These are commonly used where stability and extra long life are desired. EV conversions and electric scooters tend to have these cells, while phones, laptops, and production EVs use either li-ion NMC or LCO (Tesla).
To demonstrate this further, at my former workplace, part of the standard setup for the laptops was to limit max charge to 90%. Since the laptops spent most of their time plugged into power, the batteries don’t get used much. In two years time, the batteries still reported 90% capacity, vs. 70% capacity for batteries left sitting at 100% charge. My personal laptop has a charge limit of 75%, capping the cell voltage at 4.1 volts. In four years, it’s down to 95% capacity.
Lithium ion chemistries are primarily damaged by sitting at max charge for long periods of time, being exposed to high temperatures, or by being charged when the cell temperature is below freezing (0C / 32F). They like staying between 3.5 and 4.1 volts at room temperature the best.
My iPhone was at 100% reported capacity a week ago. It’s normally only charged while I’m commuting, so it rarely hits full charge. However, this last week we were on a trip, so the phone spent a lot of time at full charge and warmer than normal due to heavy use (photography and navigation). It dropped to 99% reported capacity, with just a few days of being fully charged (this phone is only a few months old).