MIT develops pure lithium electrodes and subverts battery design, seeking large-scale production

Recently, a research team from the Massachusetts Institute of Technology (MIT) announced that they have developed a new battery electrode that can be used to develop batteries with higher energy density.

This breakthrough was made possible by MIT's Julie Lab's long-term goal of using pure lithium metal as a battery anode. Even more unexpectedly, the development of a pure lithium electrode was only part of the conceptual design of an all-solid-state battery.

The electrolyte in current batteries allows lithium ions to move back and forth during charge and discharge cycles. But the all-solid-state battery concept designed by the team abandons the current electrolyte, which is a liquid or polymer gel between the two electrodes inside the battery.

We know that all-solid-state versions of batteries are safer than the highly volatile liquid electrolytes that have been the source of explosions in lithium batteries in the past . But one of the biggest challenges facing solid-state batteries is that when they are charged, atoms pile up inside the lithium metal, causing the lithium metal to expand as it charges and the metal to shrink during discharge. This repeated change in the battery's shape makes it difficult for the solids to maintain constant contact and can easily cause the solid electrolyte to break or separate.

Additionally, when the solid electrolyte comes into contact with lithium metal, chemical instabilities between the substances cause the solid material to degrade over time.

So the team used an unusual design to construct two classes of solids, a "mixed ionic-electronic conductor" (MIEC) and an "electronic and lithium-ion insulator" (ELI). Both materials are chemically stable when in contact with lithium metal.

On this basis, they also constructed a three-dimensional nanostructure inside the battery in the form of a honeycomb hexagonal array of MIEC tubes, part of which was injected with solid lithium metal to form a battery electrode, with extra space in each electrode tube. When lithium expands during charging, it fills the vacancies in the tube. During charging, this flow releases the pressure generated by the expansion. ELI is used as a "key mechanical adhesive" between the MIEC wall and the solid electrolyte layer.

The research team is understood to be trying to find ways to mass-produce their invention.