Stevens Institute of Technology: Charging Forward in the Race to Design Stronger, Safer Batteries

When it comes to the batteries that power our laptops, smartphones and (increasingly) electric vehicles, Stevens materials scientist Jae Chul Kim is thinking outside the box.

Literally.

“Conventional lithium-ion batteries are activated by materials with certain crystal structures,” he explains. “Now I am trying to think beyond and outside those structures.”

Now the U.S. Department of Energy, the New Jersey energy company PSEG and global battery giant LG Energy Solution are all listening — and contributing financial support to Kim’s lab.

Because, if Kim is right, next-generation batteries could last up to 30% longer, become ever thinner (opening the door to life-saving biomedical uses) — and be far less likely to catch fire.

Solidifying the future of better batteries
Raised in South Korea, Kim says his early interest in science was piqued by his parents — a pharmacist and an accountant — who encouraged him to pursue his curiosity about materials.

An opened smartphone, showing the battery inside
Lithium-ion batteries use liquid-electrolyte technology, which has drawbacks
After completing undergraduate and master’s degrees in materials science and engineering at Korea University, he moved to the United States in 2007 to complete his doctorate in materials science and engineering at Massachusetts Institute of Technology (MIT).

Later he served MIT as a postdoctoral fellow, then moved to Lawrence Berkeley National Laboratory (LBNL) to continue postdoctoral training before joining Stevens in 2018 and focusing his research on energy storage technologies.

Today much of Kim’s work involves investigations into solid-state lithium batteries, which are a sort of holy grail for battery, automotive and electronics manufacturers.

“Industry is very interested in these technologies right now,” he points out.

Solid-state lithium batteries that employ a solid electrolyte should be able to last longer, and be far safer (they can’t catch fire), than the conventional liquid electrolyte-based lithium ion batteries that now power our electric cars, tablets, smart watches and smartphones.

But knowing a solid-state is the goal doesn’t mean it is quick or easy to achieve.

There are significant challenges in designing and making solid-state batteries, explains Kim, particularly at the interfaces where the components that make all batteries work — a cathode, an anode and electrolyte materials — touch. These interfaces can physically fracture, after repetitive discharge and recharge; chemically oxidize, at lithium batteries’ relatively high voltage; or become diffuse as different elements combine and react.

“These three problems are combined; you cannot really separate them,” he says. “To make a better battery, you have to solve all of them at the same time. You have to achieve excellent mechanical, electrochemical and chemical stability.

“This is so tricky that it’s almost an ‘either-or’ problem.”

Fortunately, a class of substances known as ‘superionic conductors’ – solid electrolyte materials that retain high conductivity, comparable to that of a liquid electrolyte, when lithium ions zip around within it — has recently emerged, offering one of the most promising avenues to get there.

And that’s where thinking outside of a box comes in.

Novel materials, with the best traits of their ancestors
“Conventional materials design is largely constrained by crystal structures,” Kim explains, “because the structure dictates physical properties. Once we know the structure of a new material we are designing, we can guess what its properties would be.”

This fact is both a blessing and a curse, however.

Stevens professor Jae Chul Kim
Stevens professor Jae Chul Kim leads the university’s lithium-battery research
The properties of newly developed crystalline materials can be well-predicted by their symmetry before they’re ever made in a lab or factory, but there’s also little hope of a eureka! discovery that will shake up the world.

And since most solid-state lithium batteries currently being designed involve certain well-known arrangements of atoms or groups of atoms, their properties — and limitations — are already predictable, even as scientists labor to incrementally improve them.

“Electric cars aren’t going to suddenly start going twice as far on a charge tomorrow, or maybe even ever,” Kim sums.

Pushing beyond the limits of current technology will require new ideas, and Kim has an idea about how to do it.

“I want to get outside of conventional crystalline structure, to exploring non-crystalline materials that still retain some of the best, most desirable properties of crystalline ones,” he says.

The search for new battery materials is something like shopping for eggs at a somewhat forgiving grocery store.

Let’s say you take an empty dozen-egg carton to the egg case, packing the twelve cavities with combinations of white, brown, cage-free and Omega-3 eggs — while leaving a few, some, most (or even none) of the spaces in the carton empty.

There are many ways to do it, but a carton is still a carton; the eggs need to be similar in size to fit in the holes.

Now let’s say you bring an environmentally friendly, shapeless mesh bag to the store’s cooler room instead. You can fill it with any number and size of any mixture of different eggs that you like. You’re still working with the exact same set of elements, but the possible combinations you can bring home have multiplied exponentially — all because you ditched the carton.

Better yet, whatever you bring home in your flexible mesh bag will still be highly similar to what you would have brought back in that fixed-shape carton. You can still make an omelette. Your new omelette might taste different, more interesting or better than the first one… but it’s still an omelette.

“The most critical challenge in studying these non-crystalline materials is that there is no conclusive means to rationalize their properties,” Kim says of his painstaking work. “My hypothesis is that new solid, non-crystalline materials, if made from crystalline materials, will inherit some of the local structures of those original materials — and that we can then figure out what makes non-crystalline materials better.”

“If it works out well, this could be very impactful to industry.”

Regional, national and international support
The Department of Energy recently agreed to support Kim’s work understanding the materials chemistry of superionic conductors for the next five years, awarding him a $750,000 Early Career Research Program award recommended by DOE’s Office of Basic Energy Sciences.

PSEG has also supported Kim’s work as part of several gifts to Stevens for advanced energy research, most recently in 2021.

And we’re not just talking about cars that can drive farther or phones that can go longer without a recharge. In addition to those obvious transportation and communications applications, the development of working solid-state batteries would usher in new classes of medical uses, such as pacemaker or other batteries.

“You could make solid-state lithium batteries very thin, even into flexible films, which is something you can’t do with current lithium-ion technology,” Kim points out. “There is a certain form factor required by the configuration of the lithium-ion cell, and it is non-trivial to make those batteries smaller or more flexible than are now.

“Truly solid-state lithium batteries could open up many new biomedical applications, including wearables and medical devices.”

As he works on the challenge of materials design, Kim also continues research on other, related projects, including a collaboration with Stevens chemical engineer and polymer expert Dilhan Kalyon. The two propose to use electrowriting techniques to improve the fabrication process of lithium batteries, work supported by the next-generation battery company LG Energy Solution.

“Better batteries are very important to the planet’s sustainable energy mix,” concludes Kim. “As academic researchers, we will play a significant role in developing a better understanding of the fundamentals of new materials and processes for energy storage and generation.”

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