No, you can't wear out a certain part of a Lithium battery. Well, you could on multi-cell batteries, but that is not possible because they are attached to a balancing circuitry which makes sure the cells are all charged and discharged evenly.
In the end, it's all about the battery chemistry. Every charging cycle does damage to the battery's chemistry, reducing its ability to store energy. So every time you charge, you will lose a tiny bit of your battery capacity. Also, the chemistry will age even without using it, using some of its ability to store energy over time, thus reducing the capacity of the battery. That's perfectly normal and there is nothing you can do about this.
There are however things that Li-Ion or Li-Poly Chemistry doesn't like at all. This includes
- being discharged to very low levels (<20%) [medium impact]
- staying on low charging levels for a long period of time [high impact]
- being charged to 100% [medium impact]
- or staying on 100% charge all the time [high impact].
Doing these things, increases the aging of the battery chemistry and makes the battery lose it's original capacity faster.
Now to make that clear: You won't destroy your battery immediately by running it empty or by charging it to 100%. There is nothing wrong with doing that when it's necessary. But it shouldn't be done too often or all the time like a lot of people do. So don't run your battery to 0% all the time and don't charge it to 100% if you don't absolutely need a full charge. Try to use your battery within the range of 20% to 80% when possible, which can reduce aging of the chemistry significantly over the long term.
Anyhow, the aforementioned behavior has a comparably minimal impact on battery health. Common mistakes such as leaving a battery on low charging levels for extended periods of time or leaving it plugged in with 100% charge for days are much worse for the chemistry as already indicated in the list above, and are to be avoided at all cost. Thus, if you don't plan on using the battery for a longer time, you shouldn't charge to more than 80%, better is something in between 50% to 70%. This avoids the accelerated chemistry aging from being stored at a charge of 100%.
There is no reason why Apple doesn't let the users take manual control over their optimized battery charging. I guess it's just against their philosophy which is plain stupid because their feature doesn't work. But that's why I recommend AlDente which does what Apple failed to do. They are using the same mechanism that Apple's optimized charging uses, telling the SMC to stop charging at a specific battery level. Once that level is reached, no more energy will be pumped into the battery and the Mac runs from external power. If you want to use the battery, you can either choose to charge it to 100% before you unplug or you simply use it from whatever your limit is.
