Synthesis, structure, and phase relationship in lithium manganese oxide spinelElectronic supplementary information (ESI) available: neutron and X-ray Rietveld refinement results of LiMn2O4. See http://www.rsc.org/suppdata/jm/b3/b314810f/

Abstract

Phase relationships, structures, magnetic properties, and phase transitions in the lithium manganese oxide spinel were studied based on a wide variety of samples synthesized at temperatures over a range of 750 ¡ t ¡ 900 uC with Li/Mn ratios between 0.5 and 0.55 and various starting materials. The system was divided into three categories: oxygen deficient spinels, LiMn 2 O 4 2 d ; lithium-substituted spinels, Li 1 1 x Mn 2 2 x O 4 2 d ; and the stoichiometric spinel, LiMn 2 O 4 . Their structures were discussed based on the structure data determined by TOF neutron and synchrotron X-ray Rietveld analysis. The amount of oxygen vacancy was determined to be d # 0.14(3) in LiMn 2 O 4 2 d , for example, for the spinel synthesized at 900 uC, and the nearly stoichiometric composition was obtained at 750 uC followed by heating at 470 uC for several times from lithium hydroxide and manganese oxides as starting materials. The oxygen vacancy was dependent upon the synthesis conditions and starting materials. It decreased as the Li/Mn ratio varied from 0.5 to 0.55, and as the synthesis temperature decreased from 900 to 750 uC. Based on the synthesis and structure results, the phase relationship in the ternary diagram, Li-Mn-O, is discussed.{ Electronic supplementary information (ESI) available: neutron and X-ray Rietveld refinement results of LiMn 2 O 4 . See

Oxygen‐Vacancy Ordering at Surfaces of Lithium Manganese(III,IV) Oxide Spinel Nanoparticles

“…[4] This is attributed to charge ordering of Mn 3+ and Mn 4+ ions as a result of cooperative interactions between Jahn-Teller-distorted Mn 3+ ions on the octahedral site. The presence of oxygen vacancies, which can be introduced by altering the synthesis conditions and starting reagents, [5] leads to a higher proportion of Mn 3+ relative to Mn…”

The Sintering Temperature Effect on Electrochemical Properties of LiMn2O4

“…8 This is because the number of oxygen vacancies increases with increasing the heat treatment temperature, accompanied by a decrease in the average oxidation state of the Mn ions. 9,15,28 In the case of LiMn 2 O 4 , Mn 3+ and Mn 4+ ions are located in the octahedral site in high spin states 29 and the ionic radius of Mn 3+ is greater than To confirm Mn dissolution of the LiMn 2 O 4 particles produced at high temperatures, the XRD patterns were compared after 50 charge-discharge tests (Fig. 8).…”

“…8 It induces a change in the mean charge state of the Mn ion, alters the lattice parameter, and deteriorates the electrical properties. 9,10 On the other hand, Mn dissolution reduces the amount of active materials after a reaction with the electrolyte, which is represented by the Hunter's reaction 11 ; 2LiMn 2 O 4 + 4H + = 3λ-MnO 2 + Mn +2 + 2Li + + 2H 2 O. The proton in the chemical reaction is supplied as a byproduct of the chemical reaction of LiPF 6 in the electrolyte and water molecules, and Mn +2 ions are produced from the reaction; 2Mn +3 = Mn +2 + Mn +4 .…”

Surface Imaging by ABF-STEM: Lithium Ions in Diffusion Channel of LIB Electrode Materials

“…The thermal diffusion scattering absorptive potential approximation was included with Weikenmeier-Kohl scattering factor. The DebyeWaller factors of manganese, oxygen, and lithium were assumed to be 0.84, 1.11, and 1.07Å 2 , respectively [19]. The slice thickness was 0.291 nm in the [110] direction.…”

“…A LiMn 2 O 4 crystal, a well-known positive electrode material of LIB, has a spinel structure (space group: Fd3m, a = 0.8245 nm [19]). Manganese ions are located in octahedral sites and lithium ions, tetrahedral sites in the cubic close packed (ccp) array of oxygen ions.…”