If you feel like your cellphone is running out of battery more quickly now than when you just bought it, that's normal. Over time, the ability of lithium-ion batteries to store power will decrease.
Every time a battery is charged and used, its capacity slowly decreases. That's why after hundreds of charging cycles, the battery can't store as much energy as before.
So it's not just because the cellphone is getting older or there are too many applications. The battery itself also experiences a natural aging process.
