Not sure if you've found your answer or not, but I found out how to crack it open pretty easily despite the battery not being all that serviceable.... if you look closely at the seam all the way around it, just below the charging prongs, opposite from the USB ports, there is a small break in the material inside the seam. Stick an eyeglass flathead screw driver through it and twist - it will separate! Follow the seam to the top of the device in between the USB ports and the charging prongs, and you'll see another one, so while keeping the two sides spread apart as best as possible, do the same thing to the next tab, and you'll be able to pull the whole thing apart.
Now, that being said, the 6000mAh battery is composed of two cells that are hardwired to the connectors - unless you source the cells separately, which I don't see how that's possible, this probably won't help you. The reason I cracked mine open was to fine out how to replace the charging prongs since the ones that came with it were VERY fragile and broke - first they stopped being synchronized and you would have to flip each prong individually, and then one just simply fell out of the housing! In order to fix it, I grabbed a spare Jawbone charger for any headset or Jambox, cracked that open with a hammer (it cannot be used again after you do this anyways), ripped out the charging prongs carefully so as not to break them, and then on the Zaggsparq 2.0, unscrewed the arm that holds them in place, removed the one remaining one, and inserted the joined charging prongs, then screwed down the arm over the prongs.
NOTE - When you reassemble the housing, it may not snap together as you had it before, I actually had two small 2-3mm pieces of plastic rattling around inside the housing while I was trying to figure out why it wasn't snapping back together. The simple fix is to get some GOOD (read: 3M heavy duty) clear packaging tape and run around it ONCE after holding everything together without any gaps, lining up the top panel that the charging prongs sit it. Doesn't look like new, but functions just like it now!
Hope that helps a LITTLE, or at least helps someone else who doesn't feel like spending another $30-60 on a new one if the stupid charging prongs break!!!