Local structure of manganese oxides and lithium intercalates

The aim of this work is to determine the vibrational properties of manganese oxide frameworks and their lithium intercalates used as positive electrode material in Li-ion batteries. Raman and FTIR spectroscopies yield reliable description of material structure in which distortion of the basal MnO6 octahedra may be expected. Lattice dynamics are studied using either a classical group theoretical analysis or a local environment model. The local arrangement in MnO2 structures is investigated for pyrolusite, ramsdellite and the Li0.33MnO2 phase. The phase evolution as a function of the degree of lithium intercalation or deintercalation is reported and analysed in series of manganospinels Li1-x+delta Mn2-delta O4 with 0 <= x <= 1 and 0 <= delta <= 0.33. The trigonal distortion of MnO6 octahedra is evidenced by insertion of lithium ions into the [B-2]O-4 spinel framework. A comparison with tetragonal Li2Mn2O4 and Li6.5Mn5O12 spinels shows the influence of the Jahn-Teller effect on the Raman features for this class of materials. The local structure was characterized as a function of the mean oxidation state of manganese cations.