I have repaired several NiCd types but not LiOn. They are usually called a Sub-C due to their smaller length than a regular C battery.
They are usually spot welded in a series so you need to 1st find the bad cell w/VOM & then break the weld & solder the new sub-c in its place. Note the polarity! Charge & test.
Hope this helps.
Kevin
August 2009