>Over the course of years, the lithium-ion battery that once powered your machine for hours (days, even!) will gradually lose its capacity to hold a charge. Eventually you’ll give in, maybe curse Steve Jobs and then buy a new battery, if not a whole new gadget.
That sentence bugs me a lot because Apple only uses these batteries in a few devices: iPhones and iPods. ((They do sell massive quantitates of these devices though.)) The rest of Apple’s battery powered devices use the newer lithium-polymer batteries. In the battery world lithium-ion was a massive step forward, flawed, but worth the trade offs.
Admittedly I don’t know a ton about lithium-polymer batteries, but from what I read over on the ever questionable [Wikipedia](http://en.wikipedia.org/wiki/Lithium-polymer_battery), these batteries are an extension of lithium-ion batteries that do two things better:
1. More cycles before the battery wears down.
2. Less discharge while sitting unused.
This is why new MacBook Airs, for example, can hold their charge on ‘standby’ for a month at a time. This is also likely why Apple seals these batteries out of the customers reach:
>The major risk factor is the volatility. When punctured, Li-Po batteries react quickly by smoking and causing large fires.
So there’s that.