help please

i got a second hand xperia ion with dead battery,after changing a new one it turns on with a lock pattern,several trails then appairs mcafee with pin and code finaly a strange lock :
the battery shows 0% even when plagued to charger it turns on : sony logo xperia then hangs on first step and turns off then after 10mn it does the same thing
i managed to flash it with flashtool and LT28h_6.2.B.0.211_Generic firmware but the probleme is not solved and now i can t even enter flashmode or flashboot mode
please,please,please,i need your help