Suk Hyun Kang

A facile and highly efficient short-time homogenization hydrothermal approach for the smart production of high-quality α-Fe2O3 for rechargeable lithium batteries

In the present work, we have synthesized zero-dimensional (0D) and three-dimensional (3D) iron oxide (α-Fe2O3) sub-micron particles using a one-pot hydrothermal approach. Morphological studies reveal that the as-synthesized spherical α-Fe2O3 (SFO) material consists of nanospheres with void spaces. The prepared SFO delivers a high specific surface area of 100.80 m2 g−1 and significantly increases the contact area between the electrode and the electrolyte. The initial galvanostatic specific capacity of the SFO materials was 1306 mA h g−1 at a current density of 100 mA g−1, which is superior to that of bare cubic α-Fe2O3 (CFO). Moreover, the mesoporous SFO shows a good cycling stability with a capacity retention rate of 91.4% after 100 cycles. These attractive results suggest that the mesoporous SFO shows a good electrochemical performance as a negative electrode material for high-performance Li-ion batteries.

Preparation and Characterization of the LiNi0.8Co0.1Mn0.1O2 Cathode Active Material by Electrophoretic Deposition

The electrophoretic deposition (EPD) process enables more uniform coating layers and saves time over the traditional laminating (LN) process. LiNi0.8Co0.1Mn0.1O2 (NCM811) is prepared by EPD and LN processes in this study. The electrode materials, which are composed of active materials, conductive agents, and binders, are more uniformly dispersed on the substrate by the EPD process when compared with the LN process. Since the weight ratio of NCM811 can be changed through the EPD process, the specific capacity is calculated by weighing the deposited active materials after the process. The crystal structure and particle morphology of the prepared cathode electrode are investigated by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. The electrode prepared by EPD delivers a specific discharge capacity of 189.3 mAh g-1 at a current rate of 0.2 C at the first cycle and exhibits capacity retention of 88.6% after the 40th cycle. Compared with LN, EPD shows a good rate capability at various current rates from 0.2 to 2.5 C. These results provide the evidence of the superior electrochemical properties and process efficiency of the electrodes prepared by EPD.

Growth of Er3+/Yb3+ co-doped CaMoO4 thin film by a spray coating and its upconverting luminescence.

Polycrystalline Er3+/Yb3+ co-doped CaMoO4 (CaMoO4:Er3+/Yb3+) film was successfully fabricated by a spray coating method. Crystal structure, surface morphology and upconversion (UC) luminescent properties were investigated. Under 980-nm excitation, CaMoO4:Er3+/Yb3+ film exhibited strong green UC emissions at 530 and 550 nm (2H,11/2 --> 4S3/2 - 4I15/2) visible to the naked eye with a weak red emission near 660 nm (4F9/2 --> 4I15/2) corresponding to the intra 4f transitions of Er3+. A possible UC mechanism related to the pump-power dependence is discussed in detail.