Yeah disposable vape pens are a massive e-waste. Usually the batteries and electronics are still totally functional. There was a YouTuber making a large rechargeable battery from discharded vape pens although you really need to have the same make and model to pull that off as you need the cells to be mostly identical at to avoid the possibility of it exploding or catching fire. So yeah if you can collect hundreds of the same disposable vape pen you can build yourself a pretty serious battery.