Phone battery swelling

[Russell]

I am trying to buy a replacement phone and the two that I have received (original and replacement) have both had the back of the phone starting to come unglued from the phone chassis.  There's talk on the internet that this is caused by the battery swelling and forcing the back off.  But would this happen to a phone new and unused or is it a function of the battery being charged and discharged in use?

[Wowbagger]

The only batteries I can recall swelling were to the drone that Dez bought some years ago. I can't recall what the cause was.

This may be relevant:

https://www.ifixit.com/Wiki/What_to_do_with_a_swollen_battery

[T42]

The batteries I used in my 2011 phone were both OK ~3 months ago but have since swollen up.  I've also had this with el cheapo camera batteries. Conclusion: batteries either old, of dodgy manufacture or both. Or they've been drained and left flat for too long.

[Russell]

That article seem to imply that swelling due to outgassing occurs due the generation of electrical energy.  So just sitting in a box with 30% charge is not likely to cause swelling

[Kim]

Swelling can be the result of thermal or mechanical damage without current being passed.

Could be a manufacturing defect in the battery, abuse during construction of the phone (perhaps as simple as poor dimensional tolerances), or storage at excessive temperatures.

Either way, best not to trust a swollen battery.