is it possible of the battery will explode?

Yes it is saw one on the news here in the Philippines, it was an N series Nokia phone using BLC-5 battery all original and it means it does have company defect. There is a site to verify when the battery was manufactured and if it falls to this particular timeline you can have it replaced for free

You mean cellphone batteries of some Nokia phones? Yup, I believe so, but it's just a very rare occurence...but better prevent it than be sorry later on. I mean, when you are charging your phone, never leave it alone. You should just be around just in case something like that (what we saw on TV) happens, or an explosion, which could be possible...the cause is yet unknown. I read that it could be due to some factory defects; however, more studies are conducted to really get to the bottom of it all...

Generally, it is using inferior quality standards that lead to these types of incidents [exploding phones] occurring. The best way to prevent such incidents is to use only original product enhancements and to buy them from an authorized or other reputable dealer. Usually, it is during the charging that this incident happens because of defective, rogue and counterfeit batteries and charger.