Magnesium Ion Some researchers are looking beyond lithium. The Department of Energy’s Advanced Research Projects Agency for Energy (ARPA-E) is funding high-risk, high-reward technology, such as the magnesium ion battery being developed at Pellion Technologies, an MIT spin-off. Pellion says its batteries will have twice the energy density as existing lithium-ion batteries for both consumer products and electric vehicles. At the same time, Toyota researchers in Michigan say they are developing their own magnesium battery for an EV that can run twice the distance as current batteries on a single charge, but don’t expect it until 2020. The race is on.