Not an expert and I didn't downvote but from my examination of laptop batteries, they appear to be composed of LIon cells of a standard size, something like 3V

Not an expert and I didn't downvote but from my examination of laptop batteries, they appear to be composed of LIon cells of a standard size, something like 3V cells. Phone batteries OTOH seem to be pretty custom designs to fit a specific phone or range of phones. For e.g. https://electronics.stackexchange.com/questions/156928/replacing-18650-cells-in-laptop-battery-with-greater-capacity-ones https://electronics.stackexchange.com/questions/156928/repla... Edit: added link.