A multi-institutional research team led by Georgia Tech’s Hailong Chen has developed a new, low-cost cathode that could radically improve lithium-ion batteries (LIBs) — potentially transforming the electric vehicle (EV) market and large-scale energy storage systems. 

“For a long time, people have been looking for a lower-cost, more sustainable alternative to existing cathode materials. I think we’ve got one,” said Chen, an associate professor with appointments in the George W. Woodruff School of Mechanical Engineering and the School of Materials Science and Engineering.

The revolutionary material, iron chloride (FeCl3), costs a mere 1-2% of typical cathode materials and canstore the same amount of electricity. Cathode materials affect capacity, energy, and efficiency, playing a major role in a battery’s performance, lifespan, and affordability.

“Our cathode can be a game-changer,” said Chen, whose team describes its work in Nature Sustainability. “It would greatly improve the EV market — and the whole lithium-ion battery market.”

First commercialized by Sony in the early 1990s, LIBs sparked an explosion in personal electronics, like smartphones and tablets. The technology eventually advanced to fuel electric vehicles, providing a reliable, rechargeable, high-density energy source. But unlike personal electronics, large-scale energy users like EVs are especially sensitive to the cost of LIBs. 

Batteries are currently responsible for about 50% of an EV’s total cost, which makes these clean-energy cars more expensive than their internal combustion, greenhouse-gas-spewing cousins. The Chen team’s invention could change that.

Building a Better Battery

Compared to old-fashioned alkaline and lead-acid batteries, LIBs store more energy in a smaller package and power a device longer between charges. But LIBs contain expensive metals, including semiprecious elements like cobalt and nickel, and they have a high manufacturing cost. 

So far, only four types of cathodes have been successfully commercialized for LIBs. Chen’s would be the fifth, and it would represent a big step forward in battery technology: the development of an all-solid-state LIB.

Conventional LIBs use liquid electrolytes to transport lithium ions for storing and releasing energy. They have hard limits on how much energy can be stored, and they can leak and catch fire. But all-solid-state LIBs use solid electrolytes, dramatically boosting a battery’s efficiency and reliability and making it safer and capable of holding more energy. These batteries, still in the development and testing phase, would be a considerable improvement. 

As researchers and manufacturers across the planet race to make all-solid-state technology practical, Chen and his collaborators have developed an affordable and sustainable solution. With the FeCl3 cathode, a solid electrolyte, and a lithium metal anode, the cost of their whole battery system is 30-40% of current LIBs. 

“This could not only make EVs much cheaper than internal combustion cars, but it provides a new and promising form of large-scale energy storage, enhancing the resilience of the electrical grid,” Chen said. “In addition, our cathode would greatly improve the sustainability and supply chain stability of the EV market.”

Solid Start to New Discovery

Chen’s interest in FeCl3 as a cathode material originated with his lab’s research into solid electrolyte materials. Starting in 2019, his lab tried to make solid-state batteries using chloride-based solid electrolyteswith traditional commercial oxide-based cathodes. It didn’t go well — the cathode and electrolyte materials didn’t get along. 

The researchers thought a chloride-based cathode could provide a better pairing with the chloride electrolyte to offer better battery performance.

“We found a candidate (FeCl3) worth trying, as its crystal structure is potentially suitable for storing and transporting Li ions, and fortunately, it functioned as we expected,” said Chen.

Currently, the most popularly used cathodes in EVs are oxides and require a gigantic amount of costly nickel and cobalt, heavy elements that can be toxic and pose an environmental challenge. In contrast, the Chen team’s cathode contains only iron (Fe) and chlorine (Cl)—abundant, affordable, widely used elements found in steel and table salt.

In their initial tests, FeCl3 was found to perform as well as or better than the other, much more expensive cathodes. For example, it has a higher operational voltage than the popularly used cathode LiFePO4 (lithium iron phosphate, or LFP), which is the electrical force a battery provides when connected to a device, similar to water pressure from a garden hose. 

This technology may be less than five years from commercial viability in EVs. For now, the team will continue investigating FeCl3 and related materials, according to Chen. The work was led by Chen and postdoc Zhantao Liu (the lead author of the study). Collaborators included researchers from Georgia Tech’s Woodruff School (Ting Zhu) and the School of Earth and Atmospheric Sciences (Yuanzhi Tang), as well as the Oak Ridge National Laboratory (Jue Liu) and the University of Houston (Shuo Chen).

“We want to make the materials as perfect as possible in the lab and understand the underlying functioning mechanisms,” Chen said. “But we are open to opportunities to scale up the technology and push it toward commercial applications.”

CITATION: Zhantao Liu, Jue Liu, Simin Zhao, Sangni Xun, Paul Byaruhanga, Shuo Chen, Yuanzhi Tang, Ting Zhu, Hailong Chen. “Low-cost iron trichloride cathode for all-solid-state lithium-ion batteries.” Nature Sustainability.

FUNDING: National Science Foundation (Grant Nos. 1706723 and 2108688)

 

 

Women make up just 24% of the automotive industry, but Georgia Tech graduates Jenn Voelker and Julia Vorpahl haven't let statistics stop them from paving their own way in a male-dominated field.

Both Voelker and Vorpahl work for Karma Automotive, a luxury electric vehicle manufacturer based in California. Beginning with their time at Tech, they've never let gender bias stop them from pursuing their passion.

"It's math," Vorpahl, a visualization and digital design modeler at Karma, said. "You either get the question right, or you get the question wrong. I think that attitude really helps when you get into a professional environment. It teaches you to have tougher skin where if you are the best for that job, you will get the job. That's what Georgia Tech instilled."

Vorpahl grew up in the industry watching her family operate what is now the oldest independently owned Mercedes-Benz dealer in metro Atlanta after her grandfather, an engine designer for the German automaker, came to America and opened the shop in 1967. She arrived at Georgia Tech unsure if she'd follow in her family's footsteps, but ultimately, she landed an internship at Daimler, the nation's largest commercial vehicle manufacturer.

While other interns came in with a background in automotive design, Vorpahl’s willingness to learn and tireless work ethic landed her a full-time job as the only woman in the company's design studio.

During her three years at Daimler before accepting her position at Karma in 2022, she'd occasionally make the drive from Portland, Oregon, back to Georgia. Along the way, she crossed paths with truckers, who often expressed surprise that Vorpahl was among those behind the scenes designing their rigs. She often heard questions like “Why do you work there?” or “How did you end up there?”

And her response was simple. "Women like cars, too.” 

That rang true through Voelker's childhood as well. When the senior director of program management for Karma arrived in Atlanta for her first year at Georgia Tech, she knew she'd found a place that could help her turn an aptitude for math and science, and a fervor for cars, into a career.

"Best move I ever made," Voelker said on her decision to enroll at Tech, although it wasn't just the Institute's stellar reputation that lured her from her home state of New Hampshire. "I visited campus in February. There was 6 feet of snow on the ground and then I came to Atlanta, and the flowers were blooming."

After changing her major from mechanical engineering to industrial design, Voelker got her foot in the door through an internship with Masterack, a commercial cargo vehicle equipment manufacturer based in Atlanta. She attended Tech at a time when women made up around 27% of the undergraduate population, so when she entered the workforce, she wasn't fazed. "It never bothered me. I have always felt like I fit right in, especially when it's the right school, the right class, or the right company where everybody appreciates learning from each other and working together towards a common goal," she said.

In fact, her experience on North Avenue taught her to always keep learning and never give up, a piece of advice she now passes along to other women entering the industry.

"Don’t be afraid to give your opinion in meetings, speak up and use all of the knowledge that you've learned over the years toward whatever project you're working on," said Voelker, who worked her way up the ladder at Masterack for 18 years before seeking a new challenge at Karma. “That's one thing that I haven't backed down on. If I have a strong opinion about something, I have no fear of saying it.”

Vorpahl and Voelker each commended Karma for their dedication to promoting hard-working women and a culture that fosters diversity — a principle that Vorpahl especially values after completing two study abroad programs at the University of Singapore and the University of Strathclyde.

“One of the biggest advantages was seeing how people from different countries approach design and how different schools approach design. You don’t want a bunch of people who all think exactly the same way. Otherwise, we’d all be driving around in the exact same vehicle,” she said.

Leading Karma’s commercial vehicle product line, Voelker noted that she has continued to see more women in leadership positions and at industry conferences, and she hopes that momentum carries over to the next generation. Highlighting the importance of igniting both young girls’ and boys' interest in STEM, Voelker recently spoke to a local second grade class to share her experiences.

"I've been really fortunate to have had some great mentors over my career, so I love to pay it forward to the younger generation," she said. "They were so excited, and I hope that stays with them and excites them to learn more about engineering."

In addition to providing an example to young women of how to succeed in a competitive industry, Vorpahl also hopes to share the technical aspects of what she's learned in the field with her alma mater and offer future graduates a roadmap to a career in automotive design.

"The students would thrive in this industry because it is so nitpicky, and Tech minds would just love it," she said. "There's not really a direct path from the Georgia Tech studios into car studios, so I'm hoping that I can show them that path."

Voelker and Vorpahl are bonded by their employer and their alma mater, but it’s their shared passion for seeing their hard work hit the pavement that continues to drive them.  

In the decade since Professor Gleb Yushin’s battery materials startup participated in Georgia Tech’s Advanced Technology Development Center, investments in the company have rolled in — along with the first customers.

Now the U.S. Department of Energy (DOE) is getting on board with Yushin’s Georgia Tech startup as part of federal efforts to reinvigorate tech manufacturing in the United States.

DOE awarded Sila Nanotechnologies $100 million this fall to support the company’s new factory in Moses Lake, Washington, and help Sila hire and train up to 300 workers for the facility. It was one of 21 projects funded in domestic battery materials processing and manufacturing.

“It’s our mission to help move America away from being energy dependent and become a leader in the energy transformation,” said Yushin, the company’s chief technology officer and a faculty member in the Georgia Tech School of Materials Science and Engineering. “With this funding, Sila will deliver proven, clean energy technology and world-scale manufacturing to revitalize the industry and gain independence.”

Birthed from Yushin’s research on lithium-ion batteries, Sila manufactures next-generation materials and a silicon anode technology that boosts battery energy density by 20%. The silicon anodes are a drop-in replacement for graphite anodes in lithium-ion batteries. The new facility is projected to produce enough capacity to power 200,000 electric vehicles by 2026. Sila has inked a deal with Mercedes-Benz to use the company’s technology, starting with G-Class vehicles.

Read the full story on the College of Engineering website.

For electric vehicles (EVs) to become mainstream, they need cost-effective, safer, longer-lasting batteries that won’t explode during use or harm the environment. Researchers at the Georgia Institute of Technology may have found a promising alternative to conventional lithium-ion batteries made from a common material: rubber.

Elastomers, or synthetic rubbers, are widely used in consumer products and advanced technologies such as wearable electronics and soft robotics because of their superior mechanical properties. The researchers found that the material, when formulated into a 3D structure, acted as a superhighway for fast lithium-ion transport with superior mechanical toughness, resulting in longer charging batteries that can go farther.  The research, conducted in collaboration with the Korea Advanced Institute of Science and Technology, was published Wednesday in the journal Nature.

In conventional lithium-ion batteries, ions are moved by a liquid electrolyte. However, the battery is inherently unstable: even the slightest damage can leak into the electrolyte, leading to explosion or fire. The safety issues have forced the industry to look at solid-state batteries, which can be made using inorganic ceramic material or organic polymers.

“Most of the industry is focusing on building inorganic solid-state electrolytes. But they are hard to make, expensive and are not environmentally friendly,” said Seung Woo Lee, associate professor in the George W. Woodruff School of Mechanical Engineering, who is part of a team of researchers who have uncovered a rubber-based organic polymer superior to other materials. Solid polymer electrolytes continue to attract great interest because of their low manufacturing cost, non-toxicity and soft nature.  However, conventional polymer electrolytes do not have sufficient ionic conductivity and mechanical stability for reliable operation of solid-state batteries.

Novel 3D Design Leads to Jump in Energy Density, Performance

Georgia Tech engineers have solved common problems (slow lithium-ion transport and poor mechanical properties) using the rubber electrolytes. The key breakthrough was allowing the material to form a three-dimensional (3D) interconnected plastic crystal phase within the robust rubber matrix. This unique structure has resulted in high ionic conductivity, superior mechanical properties and electrochemical stability.

This rubber electrolyte can be made using a simple polymerization process at low temperature conditions, generating robust and smooth interfaces on the surface of electrodes. These unique characteristics of the rubber electrolytes prevent lithium dendrite growth and allow for faster moving ions, enabling reliable operation of solid-state batteries even at room temperature.

“Rubber has been used everywhere because of its high mechanical properties, and it will allow us to make cheap, more reliable and safer batteries,” said Lee.

“Higher ionic conductivity means you can move more ions at the same time,” said Michael Lee, a mechanical engineering graduate researcher. “By increasing specific energy and energy density of these batteries, you can increase the mileage of the EV.”

The researchers are now looking at ways to improve the battery performance by increasing its cycle time and decreasing the charging time through even better ionic conductivity. So far, their efforts have seen a two-time improvement in the battery's performance / cycle time. 

The work could enhance Georgia’s reputation as a center for EV innovation.  SK Innovation, a global energy and petrochemical company, is funding additional research of the electrolyte material as part of its ongoing collaboration with the Institute to build next-generation solid-state batteries that are safer and more energy dense than conventional LI-ion batteries. SK Innovation recently announced construction of a new EV battery plant in Commerce, Georgia, expected to produce an annual volume of lithium-ion batteries equal to 21.5 Gigawatt-hours by 2023.   

“All-solid-state batteries can dramatically increase the mileage and safety of electric vehicles. Fast-growing battery companies, including SK Innovation, believe that commercializing all-solid-state batteries will become a game changer in the electric vehicle market,” said Kyounghwan Choi, director of SK Innovation’s next-generation battery research center. “Through the ongoing project in collaboration with SK Innovation and Professor Seung Woo Lee of Georgia Tech, there are high expectations for rapid application and commercialization of all-solid-state batteries."

CITATION: M. Lee, et. al, "Elastomeric electrolytes for high-energy solid-state lithium batteries," (Nature, 2022) https://doi.org/10.1038/s41586-021-04209-4

***

The Georgia Institute of Technology, or Georgia Tech, is a top 10 public research university developing leaders who advance technology and improve the human condition. The Institute offers business, computing, design, engineering, liberal arts, and sciences degrees. Its nearly 44,000 students representing 50 states and 149 countries, study at the main campus in Atlanta, at campuses in France and China, and through distance and online learning. As a leading technological university, Georgia Tech is an engine of economic development for Georgia, the Southeast, and the nation, conducting more than $1 billion in research annually for government, industry, and society.

A new fabrication technique could allow solid-state automotive lithium-ion batteries to adopt nonflammable ceramic electrolytes using the same production processes as in batteries made with conventional liquid electrolytes. 

The melt-infiltration technology developed by materials science researchers at the Georgia Institute of Technology uses electrolyte materials that can be infiltrated into porous yet densely packed, thermally stable electrodes. The one-step process produces high-density composites based on pressure-less, capillary-driven infiltration of a molten solid electrolyte into porous bodies, including multilayered electrode-separator stacks.

“While the melting point of traditional solid state electrolytes can range from 700 degrees Celsius to over 1,000 degrees Celsius, we operate at a much lower temperature range, depending on the electrolyte composition, roughly from 200 to 300 degrees Celsius,” explained Gleb Yushin, a professor in the School of Materials Science and Engineering at Georgia Tech. “At these lower temperatures, fabrication is much faster and easier. Materials at low temperatures don’t react. The standard electrode assemblies, including the polymer binder or glue, can be stable in these conditions.”

The new technique, to be reported March 8 in the journal Nature Materials, could allow large automotive Li-ion batteries to be made safer with 100% solid-state nonflammable ceramic rather than liquid electrolytes using the same manufacturing processes of conventional liquid electrolyte battery production. The patent-pending manufacturing technology mimics low-cost fabrication of commercial Li-ion cells with liquid electrolytes, but instead uses solid state electrolytes with low melting points that are melted and infiltrated into dense electrodes. As a result, high-quality multi-layered cells of any size or shape could be rapidly manufactured at scale using proven tools and processes developed and optimized over the last 30 years for Li-ion.

“Melt-infiltration technology is the key advance. The cycle life and stability of Li-ion batteries depend strongly on the operating conditions, particularly temperature,” Georgia Tech graduate student Yiran Xiao explained. “If batteries are overheated for a prolonged period, they commonly begin to degrade prematurely, and overheated batteries may catch on fire. That has prompted nearly all electric vehicles (EV) to include sophisticated and rather expensive cooling systems.” In contrast, solid-state batteries may only require heaters, which are significantly less expensive than cooling systems. 

Yushin and Xiao are encouraged by the potential of this manufacturing process to enable battery makers to produce lighter, safer, and more energy-dense batteries. 

“The developed melt-infiltration technology is compatible with a broad range of material chemistries, including so-called conversion-type electrodes. Such materials have been demonstrated to increase automotive cell energy density by over 20% now and by more than 100% in the future,” said co-author and Georgia Tech research scientist Kostiantyn Turcheniuk, noting that higher density cells support longer driving ranges. The cells need high-capacity electrodes for that performance leap. 

Georgia Tech’s technique is not yet commercially ready, but Yushin predicts that if a significant portion of the future EV market embraces solid-state batteries, “This would probably be the only way to go,” since it will allow manufacturers to use their existing production facilities and infrastructure.

“That’s why we focused on this project – it was one of the most commercially viable areas of innovation for our lab to pursue,” he said. 

Battery cell prices hit $100 per kilowatt hour for the first time in 2020. According to Yushin, they will need to drop below $70 per kilowatt hour before the consumer EV market can fully open. Battery innovation is critical to that occurring.

The Materials Science lab team currently is focused on developing other electrolytes that will have lower melting points and higher conductivities using the same technique proven in the lab. 

Yushin envisions this research team’s manufacturing advance opening the floodgates to more innovation in this area.

“So many incredibly smart scientists are focused on solving very challenging scientific problems, while completely ignoring economic and technical practicality. They are studying and optimizing very high-temperature electrolytes that are not only dramatically more expensive to use in cells but are also up to five times heavier compared with liquid electrolytes,” he explained. “My goal is to push the research community to look outside that chemical box.”

In addition to Yushin, Xiao and Turcheniuk, co-authors included Aashray Narla, Ah-Young Song, Alexandre Magasinski, Ayush Jain, Sheirley Huang, and Haewon Lee from Georgia Tech, and Xiaolei Re from both Georgia Tech and Chongqing Technology and Business University in China.

This work was mostly supported by Sila Nanotechnologies Inc., a Georgia Tech startup, with characterization performed at the Materials Characterization Center at Georgia Tech. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsoring organization.

Gleb Yushin is co-founder, CTO, and a stockholder of Sila. Yushin is entitled to royalties derived from Sila’s sale of products related to the research described in this paper. This study could affect his personal financial status. The terms of this arrangement have been reviewed and approved by Georgia Tech in accordance with its conflict of interest policies. 

CITATION: Y. Xiao, et al., “Electrolyte Melt-Infiltration for Scalable Manufacturing of Inorganic All-Solid-State Lithium-Ion Batteries.” (Nature Materials, 2021)  https://dx.doi.org/10.1038/s41563-021-00943-2.