Battery questions

Does rechargeable aaa batteries decrease performance in my ledshoppe 50? I mean because they are only 1,2V instead of 1,5V.

Also, can I use one 3,6V 10440 battery in there with some foil? I heard that increases performance, but I don't want to kill it.

It most likely will decrease it's power. As for the Lithium battery question...I don't know.