If the outer shell of the battery is compromised and the innards of the battery are exposed to air, it's very likely to oxidise violently and most likely catch fire and/or explode. There are plenty of YouTube videos showing what happens when Li-Ion and LiPo batteries are punctured.
Heat with anything in group 1 or 2 is going to damage something and produce a lot of heat...
Not to mention that you have to do it outside and if you're in a foggy or smoggy area, just don't try doing it. You might release a load of chloroethene and others that will just stay there if dust and carbon structures denser are blocking it....
If the batteries in there, you can almost always open the unit even if it looks like you can't. Batteries aren't designed to be dropped from a great height or onto a hard surface so don't try smashing it...