Are you in Greece at the moment and if so what is the temperature? Anything over 40 Celsius can cause battery cell damage when charging. Allow for sun through windows in the car or your home too increasing the heat on the phone. Always charge in a shaded area if possible.
No problem , I actually use an old phase change material laptop cooling mat when I'm charging my phone and/or tablet. It's useless for laptops with fan vents underneath as it blocks them but is still good for mobile devices. Says it contains sodium sulphate on the hazard label