Lithium—the crucial ingredient in the world’s best batteries—could help us kick the oil addiction. Jay Elwes descended down a dark tunnel in the countryside to find out moreby Jay Elwes / March 22, 2018 / Leave a comment
Published in April 2018 issue of Prospect Magazine
The entrance to South Crofty, a 400-year-old copper and tin mine in west Cornwall, is shut off by two high red gates. Since the mine closed in 1998, a decade or so after that industry began grinding to a halt in the region, few people have ventured inside. But on a recent winter’s morning, Aaron Wilkins, a geologist who believes the mine has a future, drove Jay Elwes through the gates…
Down a long, narrow slope—no wider than a London Underground tunnel—we headed deeper into the Earth. The car’s headlamps lit the way until we could drive no further and had to continue on foot, emergency respirators attached to our belts. Several hundred metres below ground, the neat tunnel of the mine’s entrance gave way to bare stone, and a craggy, low ceiling. The floor of the mine was red—a sign of the iron drawn from the rock by the water, which ran down the walls, collecting on the ground in large pools. We were standing at the site of the Great Cross Course, an enormous geological fault line that cuts north-south across Cornwall and out beneath the Celtic Sea.
“Most rock is fairly impermeable,” Wilkins explained. “But where there’s a discontinuity, or a structure like a joint or a fault, you would expect to find mineralising fluids. And at depth, some of these structures will contain elevated temperatures which will increase the mineral content.” The iron turning the water red is not, however, the reason why there is now commercial interest in South Crofty—and neither are there new finds of copper or tin, the metals for which the mine was dug several centuries ago. The geological faults, Wilkins said, are where “you would expect to find elevated concentrations of lithium.”
Lithium is the very first metal, and the first solid, in the periodic table. If you remember it from school it is probably because lithium fizzles to nothing when dropped in water. It is extremely reactive on account of its atomic structure. A lithium atom has three electrons, one of which is particularly unstable, and it will give up that outermost electron very easily, which makes it highly reactive. There are many other alkaline metals with loose electrons, but lithium also happens to have the smallest atomic radius of all metals. This small atomic size means that “it contains the highest potential charge, or charge density, of all metals,” said Melanie Loveridge, a senior research fellow at the University of Warwick and a materials chemist who specialises in lithium-ion battery technology. “Imagine a box of tennis balls compared with a box of ping-pong balls—say each ball represents an atom. There will be more matter (and source of charge) in the box with the ping-pong balls, as they pack more densely.”