What is the lowest voltage for a lithium-ion battery

Simply put it is often under 3.0v per cell it begins to degrade in most chemistries however the degredation is exponentially related to the voltage and often mitgated by newer processes(an 18650 can be shipped at 0v and recover 80% of the rated capacity easy I could run my 18650's down to 2–2.5v with minimal issue under low current loads like a remote control as long as I don't leave it below 3.0v for very long also lower or higher nominal voltage cells respond related to how far below the nominal you reach a lifepo4 cell (a aa battery with that chemistry is common for the phase out of "disposable" batteries) can easily hit 2.0v safely because they are designed to mimic a 2S AA setup using a dummy cell(shunt wire inside) as the voltage range is supposed to be 2.0–3.6v to tolerate lithium primary cell types used in cameras but the most common chemistry other than lifepo4 is nominal at 3.6–3.8v and can only reach 2.5–3.0v before it starts losing capacity and C rating(max discharge current vs capacity) so if it is a lifepo4 I'd say never below 2.0v under low loads and cut off at 2.5v under high loads if not lifepo4 then assume 3.0v is the safe low point as it can tolerate a spike down to 2.0v but will degrade if left under 3.0v for very long my portable dvd player pack said they were toast at 2.5v but they are among the best quality salvaged cells I ever found and I could have possibly recovered the pack if I simply charged each parallel cell pair manually using a buck-boost module set to 3.5v and a limit of about 1–2 amps then balance charged using the bms that said they were toast