Batteries for Canon Powershot S20

Hi! I hope im in the right subreddit. I was gifted a Canon Powershot S20 recently and im struggling a bit with the battery. The camera came with the original NB-5H battery but no charger. The charger for this type of battery is very expensive so i looked into using rechargeable replacement batteries instead as its much cheaper. However, i dont know if it will kill the device to use rechargeable batteries instead of a 6v lithium battery, which the device requests. Any suggestions? Thanks in advance!