Solid NMR Studies of Cathode Materials for Rechargeable Li Battery

Abstract

Li[Ni,Mn,Co]O2 electrode has been studied by 7Li MAS NMR. A sharp resonance at –1 ppm and a very broad resonance at approximately 400 ppm are assigned to the Li ions in Co-only environment and Ni/Mn(Co) environment, respectively, indicating a segragation of Co ions and Ni/ Mn ions. Different temperature behavior of the peak position is observed for Co-only environment and Ni/Mn(Co) environment. Oxidation of Ni ions is involved during the entire charging process. At high temperature, a peak narrowing caused by the electron hopping is observed