We all have this reflex: plug in our phone at night, let it charge overnight, and leave in the morning with a full battery. It’s convenient… but not ideal for its lifespan.
Most modern smartphones use lithium-ion batteries. These powerful batteries have one drawback: they age faster if they’re left fully charged too often. A worn-out battery means less battery life and more frequent recharging .
Battery Chemistry, Made Simple

Inside, energy is stored through chemical reactions. As the battery approaches its maximum capacity, the internal voltage increases… and the cells are put under more stress . Imagine a balloon that is inflated to its maximum capacity every day: after a while, it will lose its flexibility.
Keeping the battery at 100% for a long time therefore accelerates its natural aging.