Battery tech boosts EV driving range

The rise of the electrical vehicle market has seen a corresponding increase in demand for high-capacity batteries that can extend EV driving ranges. A joint team of researchers from POSTECH and Sogang University have developed a functional polymeric binder for stable, high-capacity anode material that could increase the current EV range at least tenfold.

The team, led by POSTECH professors Soojin Park and Youn Soo Kim along with Professor Jaegeon Ryu of Sogang University, developed a charged polymeric binder for a high-capacity anode material that is designed to be both stable and reliable, offering a capacity that is 10 times or higher than that of conventional graphite anodes. This was achieved by replacing graphite with Si anode combined with layering-charged polymers while maintaining stability and reliability. The research findings were published in Advanced Functional Materials.

High-capacity anode materials such as silicon are essential for creating high-energy density lithium-ion batteries; they can offer at least 10 times the capacity of graphite or other anode materials. The challenge here is that the volume expansion of high-capacity anode materials during the reaction with lithium poses a threat to battery performance and stability. To mitigate this issue, researchers have been investigating polymer binders that can effectively control the volumetric expansion.

However, research to date is focused solely on chemical crosslinking and hydrogen bonding. Chemical crosslinking involves covalent bonding between binder molecules, making them solid, but has a flaw in that once they are broken, the bonds cannot be restored. On the other hand, hydrogen bonding is a reversible secondary bonding between molecules based on electronegativity differences, but its strength (10–65 kJ/mol) is relatively weak.

The new polymer developed by the researchers utilises hydrogen bonding and also takes advantage of Coulombic forces (attraction between positive and negative charges). These forces have a strength of 250 kJ/mol, higher than that for hydrogen bonding, yet they are reversible, making it easy to control volumetric expansion. The surface of high-capacity anode materials is mostly negatively charged, and the layering-charged polymers are arrayed alternately with positive and negative charges to effectively bind with the anode. The researchers also introduced polyethylene glycol to regulate the physical properties and facilitate Li-ion diffusion, resulting in the thick high-capacity electrode and maximum energy density found in Li-ion batteries.

“The research holds the potential to significantly increase the energy density of lithium-ion batteries through the incorporation of high-capacity anode materials, thereby extending the driving range of electric vehicles. Silicon-based anode materials could potentially increase driving range at least tenfold,” Soojin Park said.

Image credit: iStock.com/Дмитрий Ларичев