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Synthesis of Spinel-Structured Core-Shell Nanocrystals for Lithium Ion Batteries
Herein, Mn3O4 nanocrystals (NCs) were synthesized by thermal decomposition of manganese acetate in oleylamine and an ultra-thin shell layers that are enriched in aluminum were introduced, finally leading to the formation of core-shell (C-S) NCs. The particle size of Mn3O4 and C-S NCs were approximately 21 nm and 24 nm, respectively, as shown in Figure 1. The atomic ratio of Al/Mn in C-S NCs was found to be ~0.2 by energy dispersive X-ray spectroscopy (EDX). The crystal structures of Mn3O4 and C-S NCs were studied using X-ray diffraction (XRD) in Figure 2, both of which matched with a tetragonal spinel structures (I41amd, JCPDS card # 55492) without any peaks related to Al2O3. In order to study composition and microstructure of the shell layer, the scanning transmission electron microscopy (STEM) will be carried out.
C-S LiMn2O4 NCs are prepared by mixing precursor C-S NCs and Li sources followed by thermal treatment. The electrochemical properties will be evaluated in Li metal half cells compared to the counterpart without shell layer. The effect of the shell layer on the electrochemical stability will be discussed.
Fig. 1. TEM images of (a) Mn3O4 and (b) C-S NCs. Magnified images are shown in the insets (Scale bars of (a) and (b) are 5 nm and 10 nm, respectively).
Fig. 2. XRD patterns of (a) Mn3O4 and (b) C-S NCs, which match well with a tetragonal phase
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