It's true, if you hold the hot soldering iron on the battery for a long period of time. One or two seconds won't hurt the battery at all.

You need a soldering iron with a large chisel tip, preferably 40 Watts or greater. This allows you to transfer lots of heat to a small area quickly, without causing the rest of the cell to heat up. Rough up the end of the cell with a dremel drum sander to get it clean, then tin the cell with quality solder such as Radio Shack rosin core.