Check the charger...if it only outputs 1 amp at 5volts....check if the phone will accept a 2.0 amp charger ...this reduces the charge times considerably.Most phone chargers are rated 2 amps .If it is 2 amps...try a different charger before you decide to replace battery.
Charging any rechargeable battery requires you to alternate between 80 % and 20% mist of the time and full drain and full charge occasionally....this will extend the life of Said battery.