https://en.wikipedia.org/wiki/Nickel–metal_hydride_battery
This is why the xbox controller doesn't ship with builtin Lion battery, its a cost saving measure nothing else, they include cheap shitty alkaline batteries ...
Yeah no, that's not why Lion has taken over, I suggest you read up about NiMH and Lion, none of them are new tech, If Graphene batteries ever become a reality then yeah at last charging and energy storage will fundamentally change and become much safer.
Controllers do more than just register button presses as well there is the touchpad / haptic triggers / rumble motors / microphone / speaker etc etc that all consumes battery, furthermore USB Charging and Lion Batteries is the industry standard compatible with practically all phone / tablet / wall usb chargers. Finally:
This doesn't even make sense, the power bank charges the battery.