Identifying Damaged Li-Ion Cells: Voltage Parameters and Tolerance in Powerbank System

Hello. I have a few questions about Li-Ion cells. I have several of them from a used laptop battery. I search everywhere and I can't find information on topics:
- How to recognize a damaged / worn cell? If my cells after charging have: 1 pair 3.8V, 2 pair 4.08V - in general what is the minimum final voltage that determines a working cell? There should be something around 4.2V, but I need accurate information
- What is the permissible voltage drop on a cell if I draw current from it up to 1.5A? With a cell charged up to 4.08V, after connecting the phone to the powerbank system, the voltage drops to about 3.3V and after about 15 minutes it is already below 2.9V. If it falls too much (or rather so), how many should it fall to?

I use the cells in a powerbank system (Li-Ion charger limited to min, 2.8V and max 4.2V voltage + step up converter to 5V and output current 1.2A max.

Thank you in advance for your answers, I want to know which links are functional. I am mainly interested in those ranges by which I will recognize a used cell, etc.

Two parameters are used to determine the state of the cell - the cell's internal resistance and its capacity. The voltage does not matter, although it may indicate too high internal resistance (when it reaches the maximum charging voltage without much current consumption) or cell damage (quick self-discharge, or simply short circuit - i.e. too low voltage).

A colleague must make some assumptions to determine if the cell is worn or not ... I think it's best based on the cell's datasheet - so look for the symbol on the Internet until you find information about capacity or resistance.

Digression: I have a starter battery in the car, in which (discharged) 3Ah entered, and which quietly spun the starter - despite the low capacity, it had enough internal resistance for the car to start ... Is the battery worn out? - depends on the point of view.

Measurements - can be done; for example for measuring capacitance, it is best to simply check how much of the cell will "come out" when discharging with a known current in time to reach the minimum voltage.

If a colleague will do similar experiments in the future, I recommend you consider buying a model charger - even a Chinese one, for PLN 100 (iMax B6 for example) - it displays the cell capacity on the LCD during discharging (apparently some versions also provide the internal resistance of the cell - I have not met yet with this).

I compared the drops with Samsung cells that I bought recently, used, but apparently in working order. On them the voltage under a connected telephone dropped from 4.09 to 3.90V and dropped very slowly. However, those from the laptop, as I mentioned, connecting to the phone caused immediate drops from 4.08V to about 3.3V and the maximum current consumed is 1.5A, so probably too large these drops at such a current. 2 cells recharged my phone by 2% and two by 15% (I was charging the phone until the cells discharged to 2.8V). I think that both pairs will no longer serve as a powerbank link. I have another link from a Chinese powerbank, which surprisingly holds 4.23V (I don't know how it is possible) and drops to about 4.1V under load, I wonder how long it will work.