Warning- Dangerous methods involved, this is not a how-to guide. Do not try this at home, instead go a friends house and bring safety glasses! If you try this I hold no liability and let it be know that I not only have membershit in zero f*cks club, I am the president of the club.

Never solder or disassemble Lithium Batteries. They can explode when heated and the strips inside react violently when exposed to water and moisture in the air. ]

Okay so when you need a 9V battery you probably already know it's going to cost you a bank roll. So what do I do? I go upstairs and grab my old trusty analog meter (Instead of walking out to my car and grabbing my clamp meter that had a battery). I turn it on... Opps, already turned on for the last 5 years but I can just replace the AA and be on with it... Open it up and it takes a AA and a 9V but it has a 9V in it. I pull out my unloaded 9 and that is where it all starts...

Get that old 9V and take it's cover off...
Built me a 9...a 9V...(DO NOT ATTEMPT-DANGER)-20170612_013224.jpg
They are hardly ever made like this now, they have a newer cheaper way of making them where it it stacked in plastic casing but with this style the battery pretty much consist of AAAA batteries, 1.5V each.
Built me a 9...a 9V...(DO NOT ATTEMPT-DANGER)-20170612_013216.jpg
Built me a 9...a 9V...(DO NOT ATTEMPT-DANGER)-20170612_013140.jpg
I pulled the top off of it, noting which was negative side and which was positive then I arrange my free Harbor Freight AA cells in the right directions then put a rubber-band around them.
I get my trusty solder iron out and my safe goggles and tin the tips of all the batteries. I noticed 2 of the batteries had dents in the side but that's okay....
Built me a 9...a 9V...(DO NOT ATTEMPT-DANGER)-20170612_013636.jpg
I then solder a wire going neg - to pos + so that the batteries are connected in series....
Built me a 9...a 9V...(DO NOT ATTEMPT-DANGER)-20170612_035826.jpg
Note that I had the connector soldered on backwards here but all and all it worked...
Built me a 9...a 9V...(DO NOT ATTEMPT-DANGER)-20170612_035909.jpg
Then after all that soldering on them gotta hold them together somehow so I bust out the hot glue gun and done. Here is a little side by side to compare the sizes
Built me a 9...a 9V...(DO NOT ATTEMPT-DANGER)-20170612_040649.jpg