Need recommendations for battery packs

I'm going to my dad's for Thanksgiving in a few weeks, and my phone doesn't really have the best battery life (i only use my phone with the maxed out resolution so not a big shocker)

After looking at other posts, I see that people say different airlines have different rules on what defines if a battery pack is allowed or not

I'm flying through Delta, if anyone could give me any recommendations it would be greatly appreciated. Thank you!