The Peltier effect is a phenomenon involving two different metal elements in a circuit. It explains how an increase or decrease of temperature occurs at these materials, depending on which way the current flows. A team of researchers at University of Illinois Urbana-Champaign studied this effect in heat flows in lithium-ion batteries.
What They Learned from Heat Flows in Lithium-Ion Batteries
Battery scientists usually track voltage and current to assess battery performance, the researchers explain. However, their work demonstrates how observing heat flows in lithium-ion batteries also provides important insights into battery chemistry. In this instance the key was exploiting the Peltier Effect to the team’s advantage.
In particular, they were able to experimentally measure the entropy of the lithium-ion electrolyte. This is important, because that factor assesses thermal energy per unit of temperature that is available for doing useful work. This valuable information could impact future battery design.
“Our work is about understanding the fundamental thermodynamics of dissolved lithium ions,” the project leader explains. “And we hope this information will guide the development of better electrolytes for batteries.”
How This Work Differs from Previous Research
Much work has already been done involving the Peltier Effect in solid-state systems. However to date, the temperature differences have been too slight in ionic systems like lithium electrolyte. The team from University of Illinois Urbana-Champaign resolved this impasse, by using a novel temperature measurement scale.
This new scale enabled them to resolve one hundred-thousandths of a degree Celsius. This enabled the team to measure the heat difference at the two ends of the battery scale. They were then able to calculate the entropic thermal energy available to do useful work
“An underappreciated aspect of battery design is that the liquid electrolyte is not chemically stable when in contact with the electrodes,” the project leader explains.
“It always decomposes and forms … a solid-electrolyte interphase. To make a battery stable over long cycles, you need to understand the thermodynamics of that interphase, which is what our method helps to do.”
More Information
Electrolytes in Electro-Chemistry Moving Ions
Solid–Electrolyte Interphase – Dramatic News
