Local structure of manganese oxides and lithium intercalates

Abstract

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

High-energy ‘composite’ layered manganese-rich cathode materials via controlling Li2MnO3 phase activation for lithium-ion batteries

“…10 Raman-active modes keep unchanged, the band at 552 cm À1 disappears, while shoulders characterizing cubic spinel-like phase between 630 and 670 cm À1 appear. 27,29,30 These behaviors show that the monoclinic C 2 /m symmetry is absent after cycling, which is well consistent with the XRD research results by Yabuuchi et al, 23 and the cubic spinel-like phase transformation of layered phase in local regions of these electrode materials indeed arises after long time cycling. Besides, with the initial charge/discharge current density decreasing from 50 to 20 and 5 mA g À1 , the cubic spinel-like Raman band becomes more obvious, and the Raman band position shifts from 667 to 662 and 645 cm À1 .…”

“…The spinel phase can nucleate in the layered LiMnO 2 material on the first charge (delithiation), and transformation completes within a few charge-discharge cycles. 25 In order to further investigate the phase transformation of the 0.5Li 2 MnO 3 Á0.5LiMn 0.42 Ni 0.42 Co 0.16 O 2 electrode material quantitatively, Raman scattering spectroscopy, which is sensitive to the short-range environment of oxygen coordination around the cations in oxide lattices and has been proven to be useful tools for the identification of the Li-Mn-O phases, [26][27][28][29][30] has been introduced in this work. Fig.…”

“…Fig. 10 shows the Raman spectroscopies of the 0.5Li 2 MnO 27,29,30 The two main bands at 479 and 599 cm À1 are assigned to the E g and A 1g Raman-active modes for the M-O arrangements in the layered lithium metal oxide with rhombohedral R % 3m symmetry. 31,32 The band at 552 cm À1 is more likely to be assigned to the band of the Mn-O arrangements with monoclinic C 2 /m symmetry.…”

Structure and electrical properties of lithium nickel manganese oxide (LiNi0.5Mn0.5O2) prepared by P123 assisted hydrothermal route

“…5(a)), indicating no carbon residuals after calcination. The observed Raman active bands were found to be well agreed with the reported values of the layered compounds [42][43][44][45][46][47].…”

“…5(a) the two Raman active modes A 1g and E g were found to be at 591 and 480 cm −1 respectively. These modes were due to the vibrations of Mn-O and Ni-O respectively for layered LNMO compounds [46]. Some of the less pronounced shoulders were found to appear below 400 cm −1 due to the presence of Li 2 MnO 3 super lattice.…”