While a lot less dramatic then the laptops that burst into flames (here and here) this battery is definitely distressed.
The battery originally had perfect right angles. (Its hard to photograph)
It has now become so bloated that the cover on the back of this cordless phone (yes I know it looks like a calculator), does not close. The phone is actually very slick and can only be used with a headset. But anyway, now I have to find a new battery for it. BTW this probably has nothing to do with Uniden, it just happens to be in their phone.
See also this link for the relevant Wikipedia entry on the Lithium ion battery.