[Image above] Microscope image showing dendrites growing in a lithium metal battery. Credit: Neil Dasgupta

We write about lithium-ion batteries a lot—but that’s because there is a lot of research happening to better these little energy storage powerhouses.

That research spans a wide gamut of strategies to better tomorrow’s batteries. For example, some researchers are devising inexpensive and scalable solutions to fabricate battery anodes made of silicon nanowires that could significantly boost capacity. Other scientists are developing ceramic films that could allow development of safer solid-state lithium-ions.

But in addition to strategies to better lithium-ions, there are lots of alternative battery types, too.

One promising energy storage option is lithium metal batteries, which offer 10X greater energy storage potential than today’s lithium-ions. But the key word there is potential.

That’s because lithium metal batteries incorporate all-metal electrodes that are particularly prone to dendrite formation on their surface. Dendrites—tiny fingerlike structures that kill battery performance and pose safety issues—are a problem for other batteries, too, but particularly problematic for lithium metal versions.

“As researchers try to cram more and more energy in the same amount of space, morphology problems like dendrites become major challenges. While we don’t fully know why the Note 7s exploded, dendrites make bad things like that happen,” Kevin Wood, a postdoctoral researcher in mechanical engineering at the University of Michigan, says in a Michigan news release. “If we want high energy density batteries in the future and don’t want them to explode, we need to solve the dendrite problem.”

Wood and a team of University of Michigan researchers have made an important step towards doing just that—they have developed a strategy to observe dendrite formation in batteries in real time. Those observations will help scientists understand how dendrites form, a critical step towards being able to solve the dendrite problem.

The team build a battery with a visualization window—a literal window in the side of the battery that simply allows the team to watch what happens as the battery cycles.

The scientists mounted the visualization window-equipped battery onto a high-definition video microscope so they could film the dendrites as they formed. Coupling that visual data with simultaneous voltage measurements from the battery as it cycled, the team analyzed how the presence of dendrites correlated with battery performance.

To simplify their initial tests of the system, the scientists built their batteries with two lithium electrodes. But, they say the concept can be adapted to other kinds of batteries, too.

“Our window battery is a simple platform that can be used by researchers worldwide,” Neil Dasgupta, assistant professor of mechanical engineering at Michigan and senior author on the team’s research paper, says in the new story. “It can be reproduced in any lab with an optical microscope, simple electrochemical equipment, a machine shop and a $100 budget.”

Although the team published some of their observations in an open-access paper published in ACS Central Science, the scientists aren’t giving up all their secrets too easily. “Using this insight, the team discovered a way to significantly extend the lifetime of lithium electrodes, to be revealed in a future publication,” according to the release.

In the meantime, watch the dendrites dance and hear more from the researchers themselves in this short University of Michigan video.

Credit: Michigan Engineering; YouTube

The open-access paper, published in ACS Central Science, is “Dendrites and its: Untangling the complex behavior of lithium metal anodes through operando video microscopy” (DOI: 10.1021/acscentsci.6b00260).