The problem isn't specifically Apple's batteries; it's with current Lithium-ion battery chemistry in general. As a whole, we've nearly reached the upper bound of where energy density and consumer safety are at for providing us with a good battery that doesn't easily explode and gives the phone a constant current. The documentary series NOVA had a good episode earlier in the year that showed some possible alternatives to these https://m.youtube.com/watch?v=gxZrQ5yPsLI

Regarding the slowing down of devices, underclocking the CPU allows for both less power and a lower peak voltage to be drawn from the battery and extends the real usable life of the phone. Others would simply not turn on or pass a hardware test by failing to POST. You are right about new software versions being 'encouraged obsolescence'- a company that pushes features to its older phones knowing they may not be able handle these alongside the older essential ones definitely has an interest in you purchasing a new phone. This could easily be fixed by not having the slimmest phone on the market and instead have a thicker and more easily user-replacable battery.

"The problem isn't specifically Apple's batteries; it's with current Lithium-ion battery chemistry in general." - I'm not a battery expert, but at least according to this page [0], if you were to fit a 30% larger capacity battery, and only charge to a maximum of 4.0V instead of 4.2V, you'd apparently get the same day-to-day battery life, but the overall life of the battery would be extended 4x (ie from 1 years to 4 years)

[0] http://batteryuniversity.com/learn/article/how_to_prolong_li...

So you would be willing to have 30% less battery life everyday to avoid replacing the pack every couple of years? That’s a trade off I personally wouldn’t make.

There is no such battery.

The performance requirements could be met, but the battery (and phone) would be larger and more massive.

Even a bigger battery is going to degrade at the same rate. It might limit the need for CPU throttling, but probably not by much.

Seeing as iPads are basically iPhones with much larger batteries, and don't suffer from the same issues, I disagree.

This could have been avoided if they weren't so obsessed with thinness. I reckon that if it was thick enough to not have a camera protrusion, it would be the perfect balance of form and battery life.

A larger battery, running the same CPU, with the same stated "battery life" as the original battery, will degrade gracefully for a longer period of time before the compute performance must also degrade.