Here is more a tutorial to make a battery i remember when i was young to have made one of this have a look at the link, it's not mine (wiki source) but i know how to make it!

 

https://www.wikihow.com/Make-a-Homemade-Battery

 

Here is shown how Elettrolisis works it's in Italian i'm sorry (not my source):

 

http://www.icsgioiasannitica.gov.it/wp-content/uploads/2014/06/elettrolisi.pdf

 

Ciao

 

Toolkitman