Who can simply explain how the function works in the software of the laptop manufacturer, limiting the battery level to a certain limit, say, 80-90%.
Please do not kick much, not special. battery technology, but, in my opinion, this is done only to avoid overheating at 100% charge, when the laptop is heavily loaded and not disconnected from the mains. That is, the logic is to operate the battery in acceptable temperature conditions, because when the charge reaches 90-100%, the battery itself begins to heat up and raise the temperature in the case in addition to other elements giving off heat (processor, video card ...). Of course, everything is IMHO and it is only about lithium-ion.
In general, in my opinion, if a laptop (or any other Li-ion device) does not suffer from overheating, then this proprietary function may not be turned on or deprived of 15-20% of autonomy.