Titre : “ Next-Generation Li-ion Positive Electrodes: Understanding the Challenges ''
Endroit : Pavillon Roger-Gaudry, salle G-715 à 9 h 30.
Cette conférence sera prononcée par le Professeur Éric Mc Calla du Département de chimie de l'Université du Minnesota.
Résumé : Advanced Li-ion batteries utilizing Li-rich layered oxides as the positive electrode have the potential to substantially increase the energy density of batteries as required for both personal electronics and electric vehicles. Despite this, there remain important challenges with respect to these materials which stem from a poor understanding of the synthesis conditions and compositions required to make optimum materials and also an incomplete description of the mechanisms taking place in the electrode material during operation of the battery. In this talk, the former issue is addressed by discussing detailed phase diagrams produced by way of combinatorial XRD studies performed on thousands of samples with varying Li-Ni-Mn-O compositions. These studies provide a great deal of insight into changes taking place during synthesis which are of high significance in industrial settings, but they also reveal new materials worthy of further study. The second issue, related to a poor understanding of the changes taking place during electrochemical cycling, is also addressed here with detailed studies of model systems with varied cationic chemistries (including the use of Fe, Te, Sb, Ir, Sn and Ru). This survey study revealed a number of mechanisms taking place on the nanoscale during electrochemical cycling and has suggested a number of future directions for improving positive electrode performance such as increasing the rigidity of the cationic network and increasing the covalency of the metal-oxygen bonds.
