Pure curiosity: Does anyone know what it looks like when you cut open a VEX battery? Always wanted to know, but I do not want to cut open any of my lab’s batteries 
Usually just like this. VEX doesn’t make that different 7.2V batteries than you find on the market.
The VEX batteries are standard battery packs that are mainly used for RC cars. VEX just has a custom printed wrap on them. Fun Fact: As a result you can use many different similar batteries on your robot, for example LiPos as they last longer, just not for a competition.
This is true, I can confirm this. However, realizing this last year, we decided to use some old 7.2 Volt batteries that we had from an RC car. What you will find is that the length of the Black and Red connectors are much shorter than VEX batteries. And typically the Chargers that come with the non-vex batteries dont work as well. We ran our own test to see if this were true, turns out VEX 7.2V Batteries can be used for .566 hours longer than Non-VEX Batteries.
I can defentially imagine an overcharged Lipo bursting into flames half way though a match. 