There's a method of iPhone charging (and probably most phones) that is potentially detrimental to its battery lifespan, and it's something that most people do without a second thought. Stop charging your iPhone with its case on. While some cases may not make a difference, it's better to be safe than sorry.
Apple explicitly warns against this practice on the Maximizing Performance section of its website. Scroll down far enough and it says pretty clearly (in big bold text) to "remove certain cases during charging." It doesn't specify what types of cases might be responsible for this issue, but it does note that if your phone gets noticeably hot when charging, you should take it out of that case.
Stop charging your iPhone with its case on
TikToker David Eluemunoh went viral sharing this fact, citing Apple's recommendation. He claims this is why your phone stops charging at 80%, which is something that has happened to me several times before when I wake up in the morning and am surprised to see my phone isn't at full charge.
@david_eluemunoh ♬ original sound - David Eluemunoh
Apple's website has plenty of other battery saving recommendations that should be kept in mind. If you're planning to store the device long term, it is recommended to not fully charge or completely deplete the charge on the phone. If it is fully charged, it will actually lose capacity over time and shrink the batter life. If the phone is not charged at all, it could go into a "discharge state" and become "incapable of holding a charge" again.
The other bits of advice to protect your phone's battery are a little more obvious, like "avoiding extreme ambient temperatures" (which Apple cites as anywhere below 32 degrees Fahrenheit or above 95 degrees Fahrenheit as being the limits). The other tips are even simpler, like using Low Power Mode or optimizing brightness settings.
