A multidisciplinary research team involving scientists from Collège de France, CNRS, Université Rennes 1 and Université de Montpellier has developed a method for tracking the chemistry inside a battery, live, and throughout its multiple charges and discharges. Presented in Nature Energy on November 7 2022, this technology paves the way for improving the performance and design of future batteries.
Batteries offer the ability to store energy in chemical form : during charging, the current forces chemical reactions and energy is stored, then during discharging a spontaneous electrochemical reaction causes the electrons in the system to move in reverse. Energy is released to create an electric current.
Controlling and studying the chemistry of a battery is therefore crucial not only to understanding how it works, but also to improving its design. While this is easy to do in the laboratory, it is far less so when integrated into a system. But a multi-disciplinary research team1 led by scientists at the Laboratoire chimie du solide et de l'énergie (CNRS/Collège de France/Sorbonne Université) has just developed a method for tracking the chemistry of a commercial battery, live, as it is charged or discharged.
The technology, presented in an article published in Nature, is based on the transport of infrared light in chalcogenide glass optical fibers placed across a battery. The interaction of this light with the constituents of the battery makes it possible to identify and track the chemical molecules present around the fiber.
Researchers were thus able to observe the evolution of electrolytes and the insertion/extraction of sodium-lithium ions in the electrodes as a function of charge. And they were able to do this while the battery was in use - a first ! With this system, scientists were also able to study the interface between the electrolyte and the negative electrode material called Solid electrolyte interphase (SEI). This layer, which both conducts ions and insulates electrons, determines the longevity of batteries. In particular, the team was able to monitorin situ the nature of the chemical species involved in the nucleation and growth of the SEI that takes place during a battery's very first charge.
From a practical point of view, these results pave the way for easier and improved battery design. Currently, the optimization of electrolytes and charge test protocols is a lengthy process, in order to find the best option for an ideal SEI, and thus improve a battery's longevity. With this novel method, it is possible to see quickly and precisely how each element of the recipe evolves, interacts with the others and influences battery performance. The research team is continuing its work, focusing on the SEI, and hopes to reveal all its secrets.
Source : CNRS
Caption and image credits : A chalcogenide glass optical fiber passes through the battery, carrying light in the infrared range. The interaction of this light with the battery's components enables chemical molecules present around the fiber to be identified and tracked. frédérique PLAS / CSE / CNRS Photothèque
