Coordination of the Mn⁴⁺-Center in Layered Li[Co_0.98Mn_0.02]O₂ Cathode Materials for Lithium-Ion Batteries

Abstract

The local coordination of the manganese in Li[Co

A Theoretical Study of Local Electronic–Magnetic Properties for LiCoMnO4 in the Charge and Discharge Process

“…Although the EPR spectra of Mn 4þ in lithium cobalt manganese battery has been widely measured and reported, [19,29,30] present calculations exhibit significant differences from the previous literatures. For example, compared with LiCoMnO 4 , [19] the similar composition of Li[Co 0.98 Mn 0.02 ]O 2 and Li[Co 0.98 Mg 0.01 Mn 0.01 ]O 2 shows evidently distorted [MnO 6 ] 8À octahedra with large anisotropies of g factors and zero-field splittings (D and E), which afford remarkably rhombically distorted 3d 3 center in CF model.…”

“…As mentioned in the section of calculations, the same reference R 0 is adopted in the three centers based on the reported literatures of the Mn 4þ -involved LIBs. [29,30] Determined from Equation ( 1)-( 3), the major contributions are from D q and N, which are deeply influenced by the CF strength and the admixture of electron cloud between central Mn 4þ and ligand O 2À . Therefore, the more suitable model of D q and N based on two theoretical models (CF and CF þ CT) in C 1 should be further selected.…”

“…For example, compared with LiCoMnO 4 , [19] the similar composition of Li[Co 0.98 Mn 0.02 ]O 2 and Li[Co 0.98 Mg 0.01 Mn 0.01 ]O 2 shows evidently distorted [MnO 6 ] 8À octahedra with large anisotropies of g factors and zero-field splittings (D and E), which afford remarkably rhombically distorted 3d 3 center in CF model. [29][30][31] In addition, the g factors in LiCoMnO 4 (1.983-2.005 for C 1 , 2.090-2.14 for C 2 , and 2.014-2.21 for C 3 in Li-extracted and reinserted process) are much larger than the aforementioned two systems (with the average values of 1.986 and 1.982 in Li[Co 0.98 Mn 0.02 ]O 2 [29] and Li[Co 0.98 Mg 0.01 Mn 0.01 ] O 2 , [30] respectively). Therefore, the CT mechanism should be considered here, in view of the much larger g values for present systems.…”

“…Based on the constructed perturbation formulas of g factors and the relation with the local environment parameters, some unknown middle parameters can be confirmed by taking in the initial values of free ions. First, the reference bond distance R 0 (Mn-O: 1.902 Å) can be reasonably accepted by considering the similar systems as mentioned by Jakes et al and Stoyanova et al [29,30] and the following Density Functional Theory (DFT) calculation. Second, the group overlap integrals (S dpt % 0.0329, S dpe % 0.0900, S ds % 0.0724, and A % 1.2383) can be calculated with the obtained reference distance R 0 from the Slater-type self-consistent field (SCF) wave functions.…”

From Free Radicals and Spin-Chemistry Over Spin-Dynamics and Hyperpolarization to Biology and Materials Science

“…Jakes et al [40] investigate the local coordination of the manganese ions in LiCo x Mn 1 − x O 2 cathode materials for lithium-ion batteries employing a combination of XRD and EPR characterization. By EPR the authors could show that the manganese ions are in the high-spin Mn 4 + -oxidation state.…”