Adventtr/Getty Images Lithium batteries essentially rule our world now. Our phones, cordless tools, and cars, to name a few, all rely on the technology, and it, in turn, relies on our ability to mine and process lithium. And while deposits such as the 2.3 million metric tons of lithium in the Appalachian Mountains suggest that we'll have a steady supply of the metal for many years to come, it doesn't change the fact that lithium is relatively expensive, trading at about $26,000 per tonne as of mid-May 2026. That's not necessarily exorbitant, admittedly, but there are plenty of cheaper metals out there: Iron…