Abstract
This work aims at studying electrode materials for Li-ion and Na-ion batteries as they function inside batteries. Diffraction is the mainly used technique, exploiting neutrons, X-Rays and synchrotron radiation (SR), to obtain insights on the structural evolution of such materials as Li+ or Na+ are inserted/extracted from their framework. We adopted a combined approach of ex situ, in situ and operando measurements to extract a maximum of information from our studies. At first, we designed an electrochemical cell for in situ neutron powder diffraction (NPD) measurements, featuring a “neutron-transparent” (Ti,Zr) alloy; this cell, joined to others previously developed in our group, gave us a complete set of tools to perform our studies. We demonstrated the feasibility of operando NPD using LiFePO4, showing good electrochemical performances and high-quality NPD patterns for Rietveld structural refinements. Then we carried out detailed studies of spinels Li1+xMn2-xO4 (x = 0, 0.05, 0.10) and LiNi0.4Mn1.6O4: we reported phase diagrams, structural evolutions and subtle parameters as lithium's behavior inside the spinel framework, or thermal displacement parameters, directly upon cycling. Complementary use of SR shed light on other features, as the nature of the ordered phase Li0.5Mn2O4. Our combined studies concerned other promising electrode materials: LiVPO4O and Na3V2(PO¬4)2F3. Both revealed complex behaviors upon Li+/Na+