Lithium Ion 14500 is AA size but wrong voltage 3.7v vs 1.5v and not a good idea to use them as unless the device is designed to use them, some flashlights for example can use those 14500 but has to be designed for them otherwise you are likely to destroy whatever you have put them in.
The protected versions of those batteries can also be a little longer than a normal AA so you might have problems with fitment and you dont want to be messing around with unprotected lithium ions if you don't know what you are doing.
Also i think the reason you don't see them in normal stores is people would be trying to charge them in a normal Ni-Mh chargers so they are specialist batteries, but you can get chargers now that do both lithium ion and Ni-Mh batteries so if you got one of those and some protected 14500's you could use them but don't put them in things that are not designed for them due to the voltage difference if you were to use 2x 14500 in a 2x AA device your now powering it at 7.4v rather than 3v and follow the usual rules of messing around with 18650 lithium ions.
I use a protected 14500 in a 1xAA nose trimmer which now runs about 3x faster and will probably burn out eventually but not the end of the world for something cheap.
