Battery technology v2

Pagina 1

BATTERY TECHNOLOGY LITHIUM ION BATTERY • Negative side of the current collector made of copper • Negative electrode: it’s a layer of graphite, and it is also a storage component à all the Li is inside and that’s why it is so thick. Each cluster is made of layers, Li can enter between di?erent layers in a sort of metallic form (not ion) • Separator: very thin layer made of porous polymer structure (20 µm), not conductive at all • Positive electrode: metal oxide The electrolyte is a hydrocarbon solution because Li solves in very high concentration, it’s in the liquid phase à it’s everywhere in the battery In the positive side we have a partial oxidation, just partial because we want to reverse it. The most electrode used in automotive are Ni, Mn or Nr because of the high energy density; other options are Li, F , P because they are very stable Þ longer life. For the graphite layer we need binders to keep the graphite stable and the clusters together. The electrolyte being liquid can enter in its porous and fill the void à this gives the ionic contact. The electrons transport happens in the solid phase. The rection will occur and the surface of the clusters, while inside we have the storage. The main di?erence from fuel cell is that we have storage, so we will have Li di?usion which is very slow. Issue: if the electron is thick, there will be a high resistance to the passage among clusters and the path is more complex. We have two interfaces in which we have the reaction, the remaining volume is just a tank. Here we put the most important activity of the rection, in some cases we will add the Li+ activity. The error is very low also because we have the resistance of the electrolyte and the one of the electrodes. It is not possible to define a SS because during the discharge,…