Batteries are usually studied via electrical properties like voltage and current, but new research suggests that observing how heat flows in conjunction with electricity can give important insights into battery chemistry.
“Our work is about understanding the fundamental thermodynamics of dissolved lithium ions, information that we hope will guide the development of better electrolytes for batteries,” said David Cahill, a U. of I. materials science & engineering professor and the project lead. “Measuring the coupled transport of electric charge and heat in the Peltier effect allows us to deduce the entropy, a quantity that is closely related to the chemical structure of the dissolved ions and how they interact with other parts of the battery.”
The Peltier effect is well-studied in solid-state systems where it is used in cooling and refrigeration. However, it remains largely unexplored in ionic systems like lithium electrolyte. The reason is that the temperature differences created by Peltier heating and cooling are small compared to other effects.
To overcome this barrier, the researchers used a measurement system capable of resolving one hundred-thousandth of a degree Celsius. This allowed the researchers to measure the heat between the two ends of the cell and use it to calculate the entropy of the lithium-ion electrolyte in the cell.
“We’re measuring a macroscopic property, but it still reveals important information about the microscopic behavior of the ions,” said Rosy Huang, a graduate student in Cahill’s research group and the study’s co-lead author. “Measurements of the Peltier effect and the solution’s entropy are closely connected to the solvation structure. Previously, battery researchers relied on energy measurements, but entropy would provide an important complement to that information that gives a more complete picture of the system.”
2024-03-10 12:41:02
Original from phys.org