IPhone 3GS battery expanding/swelling?

So a couple of weeks ago i decided to treat myself to the IPhone 5s which would replace my iPhone 3GS now like you would with any out with the ok in wit the new it gets put in a draw until you decide what to do with it.

After about a month and a half i pulled it out of the draw where it had been for weeks untouched as a temporary phone as i broke the screen of my 5s and it seemed fine it was completely flat of juice so i plugged it in and after about 45 mins of it being lay on my desk charging from my mac i noticed the screen had popped up from the bezel about 2mm i picked it up to have a closer look and it was quite hot so i immediately unplugged it and put it on the table in the garden wasn't taking any risks.

After about 20 mins i went out and the whole screen and bezel had popped up and the back had all cracked and was bulging i knew straight away what it was as its quite familiar on the 3GS models.

the phone itself is about 3 years old but the battery ha been replaced about 7 month before hand with a genuine oem battery, the logic board is bent and it still comes on but freezes a lot and turns off I'm guessing this is the stress i the board and the battery being faulty.

Is there a safe way to dispose of the defective battery and where can I find a brand new genuine one, also where can I find the rear housing i've looked on ebay but they all seem to be used or cheap looking.

I don't know a lot about IPhone's in particular, but maybe this info can be helpful to you. Swollen cell batteries are common, and this is a tell tale sign that the battery is bad. The reason it happens is due to heat generated by the phone. This problem can easily be exacerbated by leaving your phone plugged up too much. Ideally, you should charge your battery when it drops to 20% and not before if possible, and most importantly, unplug it when it's charged or before.

Go and visit a phone specialist in your local town an they will sort it out for you and tell you what's wrong with it!

Not a great phone