If by "fundamental battery issue" you mean that all phones have this issue or some comparably severe tradeoff, then no, this is not a fundamental issue. Batteries don't all degrade at the same rate, and even given a specific battery tech, the way it's implemented in the device can have a dramatic impact on the longevity. Temperature, rate of charging, the degree (i.e. voltage) up to which it is charged, the degree (i.e. voltage) at which it is considered empty are all factors that are primarily in the device manufacturers hands.

Even a few percent overprovisioning can extend life expectency by a lot; and aggressive temperature-related charging (and discharging) throttling can trade peak (benchmark) performance and predictable charging speeds for longevity. I bet apple could make a phone with at least double the battery longevity with 1% price, mass, and size increases, and perf and battery life decreases -- if they wanted to. Of course, those factors are easily quantifiable, and battery longevity less so...

So sure: battery degradation is a fundamental issue in the sense that all batteries degrade - but how they do and what tradeoffs the device makes to minimize that are largely up to the manufacturer, and unfortunately also poorly documented, poorly benchmarkable, and I'm not sure how clearly a warranty would apply - so yeah, the it's a factor that manufacturers are bound to skimp on.

(I wouldn't particularly expect apple to be any worse than the rest of the pack, though).

There are ways to try and mitigate it, but when I was really getting at is that if you use ANY device with the lithium ion battery long enough something like this will end up happening.

Some other phone may be designed so it takes an extra year and a half or two, but it will still happen one day.

Technically, I suspect they could easily make em last 10 years without too many drawbacks. And if you're willing to be a bit more compromising, much more even than that. But why engineer that kind of life expectancy into a device that's going to be hopelessly outdated before then?

But a little more honesty in expected degradation would be nice, including the warranty that if degradation exceeds some minimal specification, the phone will be fixed at the manufacturer's cost, and not just for a year. 10 years may be unnecessarily long, but 1 year is definitely too short; and the level of acceptable degradation is too vague.

Cheaper Samsung phones shut off, thought Samsung has SO TERRIBLE BATTERIES it's not even shameful, they should be sued! Every battery puffs up after 6-12 months, and the warranty only covers first 6 months of usage. I know many people to whom it happened, to some multiple times, and they didn't drop the phones. This was with cheap phones obviously, but still, very bad behavior from phone manufacturers on all sides... :/

Back when I was still an Android user, I had a Nexus 4. After a year of use, it also started shutting down at random points if battery was below 20%. Before that I had HTC Desire (the first one), which did the same, at reaching 10% of battery, after about a year of use.

Maybe manufacturers should focus on usability instead of bling and flesh-cutting thinness, the latter of which would probably never make it as a feature request if it weren't for the incentivized yearly upgrade cycle.

But I bet you knew it was a battery problem, and how to fix it without buying a new phone.

That's the main problem here.

Well, yeah. But to be honest, I'd rather the performance decline than knowing I have 20% of battery and am waiting for a critical call and then the battery dies.