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October 2014

Dispelling a Misconception About Mg-Ion Batteries

Lithium (Li)-ion batteries serve us well, powering our laptops, tablets, cell phones and a host of other gadgets and devices. However, for future automotive applications, we will need rechargeable batteries with significant increases in energy density, reductions in cost and improvements in safety. Hence the big push in the battery industry to develop an alternative to the Li-ion technology.

One promising alternative would be a battery based on a multivalent ion, such as magnesium (Mg). Whereas a Li-ion with a charge of +1 provides only a single electron for an electrical current, a Mg-ion has a charge of +2, which means Mg-ions, in principle, can provide twice the electrical current of Li-ions if present with the same density. Mg-ion batteries would also be safer and less expensive than Li-ion batteries. However, the additional charge on a multivalent ion creates other problems that have hampered the development of Mg-ion batteries. This situation may soon change thanks to new findings from the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) as part of the Joint Center for Energy Storage Research (JCESR), a DOE Energy Innovation Hub.

David Prendergast and Liwen Wan, scientists working in the Theory of Nanostructured Materials group at the Molecular Foundry, ran a series of computer simulations that dispelled a long-standing misconception about Mg-ions in the electrolyte that transports the ions between a battery’s electrodes.

“The catch for multivalent ions is that their increased charge draws more attention to them – they become surrounded in the battery’s electrolyte by other oppositely charged ions and solvent molecules – which can slow down their motion and create energetic penalties to exiting the electrolyte for the electrodes,” says Prendergast. “However, we found the problem may be less dire than is widely believed.”

Read the full press release.