INTERVIEW WITH BENOIT MATHIEU, RESEARCH ENGINEER AT CEA
How will the developed tools and models allow an optimisation of high voltage gelled electrolyte cells? How would you define a cell and its function within batteries?
To better understand and answer all these questions, it is necessary to further explain the cell function within the battery. The cell is the smallest unit of energy in a battery. It consists of a positive and a negative electrode, a separator and some electrolyte in a sealed package. It provides between 3 and 4.5 volts. A battery can be made of one or more identical cells associated in series or in parallel to increase the voltage or the current of the unitary cells. Individual cell performance, lifetime and safety are the key parameters to build relevant batteries.
In relation to the above, modelling or simulation tools are essential in every field of the industry to optimise the products and reduce the costs of development and manufacturing. The cells will be used in various applications requiring specific capabilities like fast charging, high energy density, long cycle life, low temperature capability, etc. Depending on the most important criteria, cell manufacturing parameters can be quicky found by modelling to reach the best compromise for each application at the lowest cost. Moreover, thanks to the models, the cell use can also be optimised by tuning the battery management system to increase the cell life-time and safety.
Finally, the gel cell modelling is a complex system involving many physical phenomena and design parameters. Modelling the cell consists in building a method -usually a computer software- that uses some design parameters as inputs and predicts what would be the cell performance for these parameters. For this purpose, the electrochemical reactions and their interactions with environmental conditions like temperature and applied charge or discharge current must be perfectly understood and put into equations. These equations are then solved within a simulation software to predict how the cell voltage, temperature, and capacity evolves in time. Modelling also addresses safety issues by predicting safe operating limits and what happens to the cell in various accidental scenario.
