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Facile preparation of core@shell and concentration-gradient spinel particles for Li-ion battery cathode materials

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ABSTRACT

Core@shell and concentration-gradient particles have attracted much attention as improved cathodes for Li-ion batteries (LIBs). However, most of their preparation routes have employed a precisely-controlled co-precipitation method. Here, we report a facile preparation route of core@shell and concentration-gradient spinel particles by dry powder processing. The core@shell particles composed of the MnO2 core and the Li(Ni,Mn)2O4 spinel shell are prepared by mechanical treatment using an attrition-type mill, whereas the concentration-gradient spinel particles with an average composition of LiNi0.32Mn1.68O4 are produced by calcination of their core@shell particles as a precursor. The concentration-gradient LiNi0.32Mn1.68O4 spinel cathode exhibits the high discharge capacity of 135.3 mA h g−1, the wide-range plateau at a high voltage of 4.7 V and the cyclability with a capacity retention of 99.4% after 20 cycles. Thus, the facile preparation route of the core@shell and concentration-gradient particles may provide a new opportunity for the discovery and investigation of functional materials as well as for the cathode materials for LIBs.

No MeSH data available.


(a) XRD patterns of the MnO2@Li(Ni,Mn)2O4 core@shell powder and the concentration-gradient powders prepared by calcination at various temperatures for 2 h. (b) Expanded XRD patterns for the (111) and (400) peaks of the MnO2@Li(Ni,Mn)2O4 core@shell and concentration-gradient powders. The standard XRD peaks of PDF No. 00-035-0782 for LiMn2O4 and PDF No. 01-070-8650 for LiNi0.5Mn1.5O4 are also shown.
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Figure 5: (a) XRD patterns of the MnO2@Li(Ni,Mn)2O4 core@shell powder and the concentration-gradient powders prepared by calcination at various temperatures for 2 h. (b) Expanded XRD patterns for the (111) and (400) peaks of the MnO2@Li(Ni,Mn)2O4 core@shell and concentration-gradient powders. The standard XRD peaks of PDF No. 00-035-0782 for LiMn2O4 and PDF No. 01-070-8650 for LiNi0.5Mn1.5O4 are also shown.

Mentions: The XRD patterns of the MnO2@Li(Ni,Mn)2O4 core@shell powder and the concentration-gradient powders prepared by calcination at various temperatures are shown in figure 5. Although a broad XRD pattern was obtained for the core@shell powder, the diffraction peaks were attributed to a cubic spinel structure with a space group of Fd-3m. This broad XRD pattern is due to the low crystalline MnO2 phase of the core and the unreacted NiO phase. By calcination of the core@shell powder, the sharp XRD patterns were obtained, and the separation of (311) and (222) diffraction peaks became clear. A tiny diffraction peak at 17° is due to a Kβ peak of the strongest (111) diffraction. The expanded XRD patterns in the 2θ regions of 17°–20° and 43°–46° show the (111) and (400) diffraction peaks of their spinel phases, respectively (figure 5(b)). These diffraction peaks for the Li(Ni,Mn)2O4 shell of the core@shell powder were located between the LiMn2O4 and LiNi0.5Mn1.5O4 phases as a reference. Consequently, the formation of a Ni-doped LiMn2O4 phase by mechanical treatment was confirmed by XRD analysis. Both (111) and (400) diffraction peaks shifted to a higher angle by calcination. This peak shift suggests that the MnO2 phase of the core decreased with increasing the formation ratio of the spinel phase. The lattice parameter of the concentration-gradient LiNi0.32Mn1.68O4 particles obtained by calcination at 700 °C was calculated by the least square method using silicon as an internal standard material. The calculated lattice parameter of 8.181(1) Å was in agreement with the linear relation estimated from the reported values of the LiNi0.5−xMn1.5+xO4 spinels [15].


Facile preparation of core@shell and concentration-gradient spinel particles for Li-ion battery cathode materials
(a) XRD patterns of the MnO2@Li(Ni,Mn)2O4 core@shell powder and the concentration-gradient powders prepared by calcination at various temperatures for 2 h. (b) Expanded XRD patterns for the (111) and (400) peaks of the MnO2@Li(Ni,Mn)2O4 core@shell and concentration-gradient powders. The standard XRD peaks of PDF No. 00-035-0782 for LiMn2O4 and PDF No. 01-070-8650 for LiNi0.5Mn1.5O4 are also shown.
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Related In: Results  -  Collection

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Figure 5: (a) XRD patterns of the MnO2@Li(Ni,Mn)2O4 core@shell powder and the concentration-gradient powders prepared by calcination at various temperatures for 2 h. (b) Expanded XRD patterns for the (111) and (400) peaks of the MnO2@Li(Ni,Mn)2O4 core@shell and concentration-gradient powders. The standard XRD peaks of PDF No. 00-035-0782 for LiMn2O4 and PDF No. 01-070-8650 for LiNi0.5Mn1.5O4 are also shown.
Mentions: The XRD patterns of the MnO2@Li(Ni,Mn)2O4 core@shell powder and the concentration-gradient powders prepared by calcination at various temperatures are shown in figure 5. Although a broad XRD pattern was obtained for the core@shell powder, the diffraction peaks were attributed to a cubic spinel structure with a space group of Fd-3m. This broad XRD pattern is due to the low crystalline MnO2 phase of the core and the unreacted NiO phase. By calcination of the core@shell powder, the sharp XRD patterns were obtained, and the separation of (311) and (222) diffraction peaks became clear. A tiny diffraction peak at 17° is due to a Kβ peak of the strongest (111) diffraction. The expanded XRD patterns in the 2θ regions of 17°–20° and 43°–46° show the (111) and (400) diffraction peaks of their spinel phases, respectively (figure 5(b)). These diffraction peaks for the Li(Ni,Mn)2O4 shell of the core@shell powder were located between the LiMn2O4 and LiNi0.5Mn1.5O4 phases as a reference. Consequently, the formation of a Ni-doped LiMn2O4 phase by mechanical treatment was confirmed by XRD analysis. Both (111) and (400) diffraction peaks shifted to a higher angle by calcination. This peak shift suggests that the MnO2 phase of the core decreased with increasing the formation ratio of the spinel phase. The lattice parameter of the concentration-gradient LiNi0.32Mn1.68O4 particles obtained by calcination at 700 °C was calculated by the least square method using silicon as an internal standard material. The calculated lattice parameter of 8.181(1) Å was in agreement with the linear relation estimated from the reported values of the LiNi0.5−xMn1.5+xO4 spinels [15].

View Article: PubMed Central - PubMed

ABSTRACT

Core@shell and concentration-gradient particles have attracted much attention as improved cathodes for Li-ion batteries (LIBs). However, most of their preparation routes have employed a precisely-controlled co-precipitation method. Here, we report a facile preparation route of core@shell and concentration-gradient spinel particles by dry powder processing. The core@shell particles composed of the MnO2 core and the Li(Ni,Mn)2O4 spinel shell are prepared by mechanical treatment using an attrition-type mill, whereas the concentration-gradient spinel particles with an average composition of LiNi0.32Mn1.68O4 are produced by calcination of their core@shell particles as a precursor. The concentration-gradient LiNi0.32Mn1.68O4 spinel cathode exhibits the high discharge capacity of 135.3 mA h g−1, the wide-range plateau at a high voltage of 4.7 V and the cyclability with a capacity retention of 99.4% after 20 cycles. Thus, the facile preparation route of the core@shell and concentration-gradient particles may provide a new opportunity for the discovery and investigation of functional materials as well as for the cathode materials for LIBs.

No MeSH data available.