UChicago scientists are designing next-gen batteries without “forever chemicals”

Lithium-ion batteries contain harmful PFAS compounds, but PME team is working to change

Chibueze Amanchukwu wants to fix batteries that haven’t been built yet.

Demand for batteries is on the rise for EVs and the grid-level energy storage needed to transition the planet off fossil fuels. But more batteries will mean more of a dangerous suite of materials used to build them: PFAS, also known as “forever chemicals.”

“To address our needs as a society for electric vehicles and energy storage, we are coming up with more environmental challenges,” said Amanchukwu, Neubauer Family Assistant Professor of Molecular Engineering in the UChicago Pritzker School of Molecular Engineering (UChicago PME). “You can see the dilemma.”

PFAS are a family of thousands of chemicals found in batteries but also everything from fast food wrappers and shampoo to firefighting foam and yoga pants. They keep scrambled eggs from sticking to pans and rain from soaking into jackets and paint, but the same water resistance that makes them useful also make them difficult to remove when they get into the water supply. This earned them the nickname “forever chemicals.” 

Although Amanchukwu and other UChicago PME research teams are working on extraction techniques, with current technology, PFAS stay in the water forever.

Some PFAS have been linked to developmental delays in children, decreased fertility, increased cancer risk and lessened immune response. PFAS have been found in water, air, fish, and soil – and in the blood of people and animals around the planet.

“This is what we've done as a society,” Amanchukwu said. “We make an amazing material or amazing device, and then we realize that it’s not good for the environment, and then we scramble to see if we can replace it.”

The Amanchukwu Lab at UChicago PME want to flip that script. In two recent papers, the team designed two new families of PFAS-free solvents that make ideal components for next-generation batteries. The goal is to get ahead of PFAS pollution, giving future researchers a safe but powerful suite of chemicals to explore when designing batteries, turning “forever chemicals” into “never chemicals.”

"We need next-generation batteries, but for most of the current research, they are using PFAS,” said Peiyuan Ma, PhD’24, the first author of both papers. “That's why we started doing our research, to give people at least a chance to use the non-PFAS materials.”

Getting ahead of forever

PFAS make up a comparatively small part of a modern battery. A battery’s positive terminal, called the cathode, uses a small amount of a PFAS chemical called polyvinylidene difluoride as a binder – a glue to hold the particles together. Battery electrolytes, meanwhile, use fluorinated solvents, but not all fluorinated compounds are PFAS.

The problem is not the electrolyte in current batteries. It’s the future ones.

Battery demand is increasing, calling for more and better batteries. When design problems arise, the scientific community’s default solution is too often turning to useful but dangerous PFAS, Amanchukwu said.

“We are demanding more batteries and more from our batteries. We want low-temperature performance. We want high-temperature performance. We want fast charging. We want lithium metal batteries. These are things that we are demanding as consumers,” Amanchukwu said. “What the scientific literature is doing now is to say, ‘Oh, let's add more fluorinated components into the electrolyte.’ Almost all of those will be considered PFAS."

One of the team’s recent papers, published in ACS Energy Letters, created partially fluorinated non-PFAS solvents for lithium-ion batteries. The other, published in Journal of the Electrochemical Society, designed entirely non-fluorinated solvents for the lithium metal batteries currently being explored as a higher-energy alternative to lithium-ion.

"In our work, we tried to extract some fundamental understanding of the interactions between the battery materials, we try to understand, how those material interact, and why some interactions are important to make the battery work well,” Ma said. “We realized there's no fundamental requirement of having PFAS to make the battery work."

Getting industry on board

To get industry, academia and national labs to explore this new chemical strategy, the team’s challenge was not only to prove their new family of electrolytes will be safer. They also had to prove their electrolytes perform as well as or better than electrolytes based on PFAS.

The nonfluorinated lithium metal battery designs showed more ion pairing and better capacity retention than designs based on fluorinated compounds, with some of their new family of materials also showing more oxidative stability.

The lithium-ion designs, meanwhile, showed longer cycle life and better rate capability over commercially available batteries, plus they worked in a wider range of temperatures. They showed stable cycling at temperatures from 60 to negative 40 degrees Celsius.

Switching to partially fluorinated compounds also has major environmental benefits.

“When you have a single fluorine group, they are easier to degrade,” Amanchukwu said.

There were downsides as well. The partially fluorinated electrolytes didn’t create as protective a coating on the battery’s negative terminal, for example. But including additives – which are also not PFAS – the team was able to circumvent these problems, creating low-temperature cycling and faster-charging batteries.

There are environmental arguments and scientific ones for keeping “forever chemicals” from entering the water in the first place. But there’s also an economic argument for fighting a problem before it starts.

“There's risk we take bringing new materials to market in general, regardless of environmental regulations,” Amanchukwu said. “But there's even greater risk to bringing a new material to the market with the possibility that somebody might say in 10 years or 15 years, ‘This is illegal. You can’t make this anymore.’”

• Learn more about UChicago PME’s Materials Systems for Sustainability and Health theme

—Adapted from an article first published by Pritzker Molecular Engineering.