I tried clicking that link, but it seems one needs a subscripting to view the article.
“The lithium ion needs some space in the electrodes and the electrode has to make this space, and because of the stress,” Mr. de Vries said, “the electrodes will gradually degrade and that is also then a loss of capacity in the battery.”
Why's it not there by default, then?
“It’s pretty easy to fill a sponge from dry to mostly saturated,” said Mr. Purdy, who is also a former senior staff writer for Wirecutter. “But trying to force a nearly saturated sponge to absorb the very last drops of liquid requires pressure and likely leaves more liquid pooled on the surface. That ‘pooling’ is the S.E.I. (solid electrolytic interface) buildup on a battery. S.E.I. buildup reduces the overall capacity of a battery.”
It's interphase, not interface. And this phenomena is caused by excessive discharge. I'm still looking for evidence for this at "overcharge." Instead, what i'm reading here is that this is caused simply by charging it at all, not charging beyond certain ranges or maintaining a certain charge above a certain range. It stands to reason that one could extend the life more effeciently but not allowing the charge to change much if at all. However, occasionally draining the battery to a certain degree can somewhat undo the effect, as well.
Skimming the article i don't see these quotes. Nor do i see anything on overcharge except for the comments.
One thing to contemplate: if it was a bad idea to charge them above 80%, why wouldn't the manufacturers put limiters on them to keep them from charging beyond 80%[like they already do to prevent batteries from going over 100%]?
Possible reasons:
1. If one manufacturer capped their battery capacity at 80% while the others don't, people will simply buy the product with 100% capacity unlocked for the convenience and the 80% battery product will fail unless other factors are compensating.
Write custom driver or simply design the circuit to report as 100% at 80%. We already have things setting on the battery to prevent genuine overcharge.
2. Most people are either unaware or don't care about the long-term battery life. That's the next owner's problem.
This isn't addressing the actual question.
3. Obsessing over life cycle charges isn't worth the hassle for some people. $75 labour + $40 OEM-equivalent battery is every 3-4 years is quite affordable. Some recommend 2 years, but it depends on how necessary and often you need your phone.
Still not addressing why the manufactuer isn't making this convenient.
I use AccuBattery (Android) to tell me when to charge my phone and when to unplug. It gets annoying sometimes, though. You could probably just get a smart wireless charger that'll regulate its charging speed based on the battery capacity.
This is another angle: why aren't there external plug-based chargers if this can be done with wireless charging? And, also, we're not exclusively talking about phones, here.