New type of rechargeable lithium battery now made possible thanks to scientists solving this mystery

Labs around the world have been pursuing this breakthrough for years.
Sade Agard
Solid State Battery for EV Electric Vehicle.
Solid State Battery for EV Electric Vehicle.


The development of a new type of rechargeable lithium battery, which labs have pursued throughout the world for years, that is more lightweight, compact, and safe than current ones, may now be possible thanks to a discovery made by MIT researchers.

Currently, there are two essential components of this prospective advancement in battery technology.

One is the replacement of the liquid electrolyte between the positive and negative electrodes with a considerably thinner, lighter layer of solid ceramic material. The second is the replacement of one electrode with a solid lithium metal.

By doing this, the battery's total size and weight is greatly lowered, and the flammable liquid electrolytes that pose a safety danger would be removed. However, dendrites have proven to be a considerable roadblock in that endeavour.

Until now, what creates dendrites or how to prevent them was a mystery 

Dendrites are metal growths that can accumulate on the lithium surface, pierce through the solid electrolyte, and finally cross from one electrode to the other, shorting out the battery cell. Their name is derived from the Latin word for branches. 

Until now, there hasn't been much advancement in the understanding of what causes these metal filaments or how to stop them from occurring, making lightweight solid-state batteries a practical alternative.

The new study trumps a previous belief that dendrites form by mechanical processes

The new study, which was published today (Nov. 18), not only appears to answer the question of what triggers dendritic growth, but it also demonstrates how dendrites can be stopped from piercing the electrolyte.

The team's findings show that mechanical stresses are what create the issue. Previously, some researchers believed that dendrites formed by a solely electrochemical process rather than a mechanical one.

In an earlier study, the team found a "surprising and unexpected" discovery. During the process of charging and discharging the battery, the shuttling back and forth of ions caused the volume of the electrodes to change.

Dendrite production is caused by a change in the solid-state electrolyte's volume

The team argues that this volume change inevitably causes stresses in the solid electrolyte, which must remain fully in contact with the electrodes its sandwiched between.

"There’s an increase in volume on the side of the cell where the lithium is being deposited. And if there are even microscopic flaws present, this will generate a pressure on those flaws that can cause cracking,” said MIT Professor Yet-Ming Chiang, coauthor of the study in a press release.

The team has now demonstrated that those forces are what cause the fissures that let dendrites form. Adding extra stress in the ideal direction, and with the perfect power is the answer to the issue.

Like squeezing a sandwich from the side, the dendrites could be rendered harmless

The dendrites can be rendered harmless by being directed — by pressure — to remain parallel to the two electrodes and kept from ever crossing to the opposite side. This direction would be as though you were squeezing a sandwich from the sides.

That could finally make it practical to produce batteries using solid electrolyte and metallic lithium electrodes. Not only would these pack more energy into a given volume and weight, but they would also eliminate the need for liquid electrolytes, which are flammable materials.

That could eventually make it feasible to manufacture batteries with metallic lithium electrodes and solid electrolytes. These would not only contain more energy for a given volume and weight, but also do away with the necessity for flammable liquid electrolytes.

"This is an understanding...we believe the industry needs to be aware of and try to use in designing better products"

“I would say this is an understanding of failure modes in solid-state batteries that we believe the industry needs to be aware of and try to use in designing better products,” said Chiang.

According to Chiang, the team's next step will be to attempt to apply these concepts to the production of a functional prototype battery. After this  they will determine precisely what manufacturing techniques would be required to build such batteries in large quantities.

He claims that even though they have applied for a patent, the researchers do not intend to market the technology since other businesses are currently engaged in the research and development of solid-state batteries.

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