Laboratory notes Prof Rabissi

Pagina 1

LABORATORY With respect to PMFC technology we are facing a purely commercial technology. From a point of view of testing, has an important, consequence, there is strong limitation even by intellectual property. You won't know anything about the chemistry, the internal geometries, the composition of the electrolyte of the electrodes à there is no, standard on the market. Batteries are close systems à more limited STRUCTURE, GEOMETRY AND CHEMISTRY Never dealing with an actual steady state. So in this case, when you charge or discharge a battery you are always changing the activity of reactants and products inside your electrodes. You are not able to keep a constant activity. Elemental cell is constituted by a current collector foil made out of, copper. And the negative electrode, it's copper because it's, let's say, electrochemically stable at the potential at which the negative electron is, called to operate. It's stable at very low potentials. On this current collector, which is very thin, is typically dispersed the active material of the negative electrode, which is typically carbon. So it's made out of graphite, but it's not the only possibility. The next layer is the separator, which is, a polymer nowadays, constituted by polyethylene, polypropylene, or the combinations of the two of them. The separator is porous, it’s plastic, but could be provided with reinforcing material inside in order to increase the mechanical stability and also electro chemical, protecting from dendrites and lithium plating development à operates as a safety device Then you have the positive part of your battery. So you have, again, a current collector, this time it's constituted by aluminium because it's stable at a higher potential at which the positive electrode is called to operate. the…