Smartphone batteries can swell overtime when they are constantly charging (as it is the case when connected to a kapptivate smartphone robot). There is no real solution to this issue, but you may use a smartphone stand to reduce heat and delay this phenomenon.
To completely prevent such issues, you may want to consider smartphone models that can support "pass through charging" which means that, when charging, the power goes directly to the phone itself without going to the battery. This way the battery is not being used constantly and won't swell overtime.
Here is a non-exhaustive list of smartphones that support this feature:
- Galaxy S23 series
- Galaxy S22 series
- Galaxy Z Fold 5
- Galaxy Z Fold 4
- Galaxy Z Fold 3
- Galaxy Z Fold 2
- Galaxy Z Flip 5
- Galaxy A73 5G
- Galaxy A33 5G (most affordable phone)
To learn more about this feature (and how to activate it), you can read this article.