New Mi2s battery overheated

Nov 1, 2012
I bought new 32Gb Mi2S phone last week and i flashed the 3.5.31 version.

My phone phone heats up When I was open 3G network and Wireless but No problem 2G network.
phone set normal mode.
I open back cover and I took off the battery when phone warm-heats up-overheated.
I saw battery overheated but phone not overheated.