Splitting the case of the Mifi 2200 is necessary to be able access the internal parts. This is how to go about that.
Remove the rear cover by pressing down on the cover and pulling it away from the device.
Place your finger on the back of the battery located near the edge of the device.
Push your finger into the battery and lift up to pop the battery out of the device.
Using a metal spudger, pry open the device around the seam between the front and back cover.
Once the seal has been broken all the way around, open the cases using your hands.