A recent study sheds light on the movement of electrons within the conductive elements of complex fluids found in electrochemical devices like batteries. This research can aid engineers in bridging knowledge gaps and enhancing the performance of these essential devices.
Thomas Edison experimented with countless materials before discovering the ideal tungsten filament for his lightbulb. This method of trial-and-error research persists today, yielding numerous inventions that enrich our lives. Batteries, which power many aspects of our daily existence both visibly and invisibly, serve as a prime example.
However, to enhance these materials and devices, more is needed than just experimentation. Today’s engineers must attain a deeper comprehension of the basic principles that dictate material performance, which can guide them in designing superior materials that meet demanding product specifications.
In a study released on August 13 in the Proceedings of the National Academy of Sciences (PNAS), researchers from the University of Delaware, Northwestern University, and various industries detail a broadened understanding of how electrons travel through the conductive segments of complex fluids, known as slurries, that are utilized in electrochemical devices like batteries and other energy storage systems.
This critical research helps fill existing gaps in understanding how electrons transfer between conductive particles in these materials, as engineers seek innovative methods to enhance this process.
The study is a product of collaboration between UD’s Norman Wagner, who holds the Unidel Robert L. Pigford Chair in Chemical and Biomolecular Engineering, and a team led by Jeffrey Richards, an assistant professor of chemical and biological engineering at Northwestern University and a former postdoctoral researcher at UD. Among the lead authors are UD alumna Julie Hipp, who received her PhD in chemical and biomolecular engineering in 2020 and is now a senior scientist at Procter and Gamble, and Paolo Ramos, a former NU graduate student currently at L’Oreal. Contributions were also made by Northwestern University doctoral candidate Qingsong Liu.
Wagner notes that the research team discovered that improving performance entails more than just tweaking formulation chemistry. A thorough understanding of how electrical conductivity behaves during the processing and manufacturing of slurry materials is also essential.
“To manage device performance, it’s inadequate to control chemistry alone; we must also regulate the microstructure,” Wagner explained. The final microstructure of the material—essentially how all its components come together—governs electron movement, thus influencing the device’s power and efficiency.
Performance hinges on specifics
While there are numerous electrochemical devices, let’s focus on batteries to explain further.
Batteries generate electricity by allowing electrons to flow through a conductive “slurry” composed of materials and solvents via a chemical reaction. The effectiveness of a battery system is dictated by its materials, which encompass both the chemistry and the manufacturing processes involved in its creation.
Imagine multiple racecars circling a racetrack. Although all cars have steering wheels, tires, and engines, the construction of each vehicle and its assembly can differ significantly. Therefore, just because a car features an engine and steering wheel does not guarantee it will perform like the others. This principle applies equally to critical battery components—how they’re assembled is crucial.
Conductive types of carbon black (or soot) are frequently employed in batteries as well as numerous electrochemical devices. These are nano-sized carbon crystals that aggregate, forming clusters that can be mixed with various liquids to create a slurry used to fabricate battery components or other devices.
“Within this mixture, electrons can move rapidly through the carbon black, which is extremely conductive like an electrical wire. However, the electrons must jump from one carbon black particle cluster to another because the carbon black isn’t connected as a solid structure within the slurry,” Wagner elaborated.
The researchers had previously established that the flow characteristics of carbon black—its rheology—significantly influence the material’s performance, using neutron-scattering methods at the National Institute of Standards and Technology’s Center for Neutron Research in Gaithersburg, Maryland, in collaboration with UD’s Center for Neutron Science. In this latest research, the team built upon that work to create a comprehensive framework for understanding how the conductivity of flowing slurries depends not only on the components’ chemistry but also on how the slurry is processed.
Collectively, these elements create a detailed guide for processing energy storage devices during manufacturing. The promise of such a framework is an improved capacity to design materials systematically and predict the behavior of electrochemical devices early in the design process.
“Our research provides a foundation for understanding how the structure of this carbon-black slurry, this aggregated suspension, affects the efficiency and performance of these devices,” Wagner stated. “While we are not addressing a specific battery issue, our foundational findings are intended for practical application by others working on their electrochemical systems and challenges.”
The researchers anticipate that this work will influence the formulation and processing strategies for cutting-edge electrochemical energy storage methods and water deionization technologies.
Wagner cited electrolyzer devices that utilize electricity to break water into hydrogen and oxygen. A major challenge in this process is managing how the material solutions are mixed and ensuring they possess the right properties for effectively freeing hydrogen molecules for use as an energy resource. According to Wagner, future enhancements in such devices will rely heavily on processing techniques.
“Just getting the chemistry right is not enough; if you fail to process it correctly, you won’t achieve the desired performance,” Wagner warned.
