IMO, and recognized battery experts, there is no way to solder directly to the cell without damaging the battery. The only way to do it is with solder tabs that have been welded to the battery ends.

I know we will have lots of testimonials to the fact that they have done it for years and never had a problem. I have done it too, and never had any problem, as I have gotten away with a lot of other bad habits. The fact is, battery manufactures supply batteries with tabs for the specific reason of avoiding soldering directly to the cells.

Vince