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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.

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Cross-sectional EDS elemental maps of Ni (purple) and Mn (yellow) for the concentration-gradient powders prepared by calcination at (a) 600 °C, (b) 700 °C and (c) 800 °C for 2 h. Scale bar represents 20 μm. (d) Atomic ratio of transition metals as a function of the distance from the center to the surface for the core@shell and concentration-gradient powders.
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Figure 4: Cross-sectional EDS elemental maps of Ni (purple) and Mn (yellow) for the concentration-gradient powders prepared by calcination at (a) 600 °C, (b) 700 °C and (c) 800 °C for 2 h. Scale bar represents 20 μm. (d) Atomic ratio of transition metals as a function of the distance from the center to the surface for the core@shell and concentration-gradient powders.

Mentions: The concentration-gradient spinel particles were prepared by calcination of the MnO2@Li(Ni,Mn)2O4 core@shell powder at 600–800 °C for 2 h. The superimposed EDS maps and elemental profiles of the cross-sectional view for the obtained particles are shown in figure 4. The distribution of nickel, which existed in the shell, spread into the core with the increasing calcination temperature (figures 4(a), (b)). After calcination at 800 °C, manganese and nickel were distributed to all the regions of the particles (figure 4(c)). The relative atomic ratio of manganese and nickel from the center to the surface was measured by EDS point analysis, which selected particles with a diameter of ≈50 μm (figure 4(d)). Comparing the atomic ratios in the MnO2@Li(Ni,Mn)2O4 core@shell particle and the concentration-gradient particle obtained by calcination at 600 °C, the nickel ratio slightly increased in the shell part. The product possessing a concentration gradient of manganese and nickel in the entire particle was obtained by calcination at 700 °C. In the case of calcination at 800 °C, the atomic ratio of manganese and nickel was about 80% and 20%, respectively, all through the particle. The formation approaches of the concentration-gradient shell or particle were achieved by changing a calcination temperature of the core@shell particles as a precursor. An elemental analysis of the concentration-gradient particles was conducted by ICP-AES. The total average chemical composition was determined to be LiNi0.32Mn1.68O4 in all the concentration-gradient particles prepared by calcination at 600–800 °C. The doped amount of nickel in this average composition was higher than that in the concentration-gradient spinel particle prepared by Wei et al [27].


Facile preparation of core@shell and concentration-gradient spinel particles for Li-ion battery cathode materials
Cross-sectional EDS elemental maps of Ni (purple) and Mn (yellow) for the concentration-gradient powders prepared by calcination at (a) 600 °C, (b) 700 °C and (c) 800 °C for 2 h. Scale bar represents 20 μm. (d) Atomic ratio of transition metals as a function of the distance from the center to the surface for the core@shell and concentration-gradient powders.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036501&req=5

Figure 4: Cross-sectional EDS elemental maps of Ni (purple) and Mn (yellow) for the concentration-gradient powders prepared by calcination at (a) 600 °C, (b) 700 °C and (c) 800 °C for 2 h. Scale bar represents 20 μm. (d) Atomic ratio of transition metals as a function of the distance from the center to the surface for the core@shell and concentration-gradient powders.
Mentions: The concentration-gradient spinel particles were prepared by calcination of the MnO2@Li(Ni,Mn)2O4 core@shell powder at 600–800 °C for 2 h. The superimposed EDS maps and elemental profiles of the cross-sectional view for the obtained particles are shown in figure 4. The distribution of nickel, which existed in the shell, spread into the core with the increasing calcination temperature (figures 4(a), (b)). After calcination at 800 °C, manganese and nickel were distributed to all the regions of the particles (figure 4(c)). The relative atomic ratio of manganese and nickel from the center to the surface was measured by EDS point analysis, which selected particles with a diameter of ≈50 μm (figure 4(d)). Comparing the atomic ratios in the MnO2@Li(Ni,Mn)2O4 core@shell particle and the concentration-gradient particle obtained by calcination at 600 °C, the nickel ratio slightly increased in the shell part. The product possessing a concentration gradient of manganese and nickel in the entire particle was obtained by calcination at 700 °C. In the case of calcination at 800 °C, the atomic ratio of manganese and nickel was about 80% and 20%, respectively, all through the particle. The formation approaches of the concentration-gradient shell or particle were achieved by changing a calcination temperature of the core@shell particles as a precursor. An elemental analysis of the concentration-gradient particles was conducted by ICP-AES. The total average chemical composition was determined to be LiNi0.32Mn1.68O4 in all the concentration-gradient particles prepared by calcination at 600–800 °C. The doped amount of nickel in this average composition was higher than that in the concentration-gradient spinel particle prepared by Wei et al [27].

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.


Related in: MedlinePlus