You have to charge a round cell Li-Ion with a charger made for the cell. Cell phone chargers are often just a power source where the phone manages charging internally. It's possible the voltage from the cell phone charger is much too high which will result in severe damage to the 14500 at best and will cause the battery to vent at worst.
If you know for sure the phone charger has the charging managment built into the adapter, it would work, but since you're asking, you probably don't know one way or the other.