Local structure of manganese oxides and lithium intercalates
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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+δMn2–δO4 with 0≤x≤1 and 0≤δ≤0.33. The trigonal distortion of MnO6 octahedra is evidenced by insertion of lithium ions into the [B2]O4 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.
KeywordsMnO2 Manganese Oxide Pyrolusite Lithium Intercalation Reliable Description
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