Battery problem with Redmi MI 2 phone

There could be some bad contact situation at the gold plated contacts between battery and phone. You can try to clean it and again try to charge.

If you want to charge the battery by keeping it out then you will have to approach some good mobile repair shop who can try to charge it from an external source after ascertaining its exact charging voltage which is written on the phone.

If nothing works then probably your battery is dried up before its useful cycles and now requires a replacement.

The problem solved. The charger connector was faulty. It is now replaced and working nicely.

Many users are facing motherboard and charging problem in Mi handsets. If you visit any Mi service center, then you will come to know that almost ninety percent of the users are facing these two problems.
In your case, I would suggest you to visit your nearest service center of Mi and they will definitely help you with your problem. However, you will be charged the repairing cost because your phone is out of warranty as they provide warranty for only one year.
I would also like to suggest you to charge your phone only with the authorized charger. Plug your phone in charging only when the battery is below 40 percent and plug it out once it crosses 80 percent. Never charge your phone up to 100 percent, it can kill your battery life and will affect the phone performance as well.