The CEMHTI laboratory invites you to discover the research topic of one of its students: Clément Hachem, a CIFRE 2A doctoral student in thermodynamics at ASB Aerospatiale Batteries.

My research focuses on understanding the reactive mechanisms within thermal batteries. The goal is to identify the processes behind capacity losses during operation and assess their thermal consequences (improving the thermal management of the battery).

This primary electrochemical generator remains inert until activated (no risk of electrocution, no self-discharge for years, no maintenance required). Once operational, it delivers particularly high power densities, suitable for the requirements of Aerospace and Defense. ASB Aerospatiale Batteries is currently one of the global leaders in this field.

The electrochemical stack includes active elements (traditionally lithium-based negatives, positives based on metal sulfides), an electrolyte based on inorganic salts, solid and non-conductive ionic at room temperature, and pyrotechnic elements. Upon activation, the latter provide the stack with the heat needed to melt the salts. Its high-temperature operation ensures high ionic conductivity (up to 3 times higher than that of common electrolytes) and an increase in the kinetics of electrochemical reactions. Thermal batteries can thus deliver high electrical power.

This system is composed of multiple highly reactive electrochemical materials, particularly sensitive to moisture and air. Confined in a protective casing, the battery is robust and withstands severe conditions that may involve mechanical shocks, high accelerations, rapid rotations, and wide temperature ranges.

ASB aimed to complement its industrial means and methodologies with an academic approach supported by instrumentation capable of characterizing the physical and chemical processes at the heart of the electrochemical cell during operation. It found in CEMHTI a partner bringing scientific expertise and promising techniques in the field of high temperatures, molten salts, and batteries. The first collaboration materialized through the implementation of this thesis.

ASB has developed expertise in characterizing electrochemical systems at high temperatures. Among other things, it provides access to specialized equipment dedicated to the manufacturing and study of thermal batteries (cell discharge test bench in an atmosphere representative of the battery, ...).

I employ a multi-technique approach that allows me to observe the operation of an electrochemical cell at different scales. Specialists at CEMHTI are training me in the methodologies of using cutting-edge equipment: X-ray diffraction, electron imaging, and NMR are just a few techniques advanced by the laboratory's researchers.

These powerful tools, enabling both pre and post-mortem characterization as well as in situ observation of the evolution of our high-temperature systems during discharge, provide me with data rich in insights.

In conclusion, the thermal battery is a perfect example of a multi-material system evolving in extreme conditions, representing a real technical and scientific challenge.

Back to news