You probably need to replace the battery.
Next, some battery life extention tips:
ALWAYS recharge the battery when it's charge drop under 5%.
DON'T recharge if the charge is over 30%: you want to minimise the recharge cycles.
If the battery is totaly drained, RECHARGE IT AS SOON AS POSSIBLE. After one day, it may be to late.
Leaving a Li-ion battery drained for more that a few hours is a sure way to kill it!