• Journal of Bio-Environment Control
• /
• v.4 no.2
• /
• pp.188-194
• /
• 1995

This study was carried out to investigate the effect of NH$_4$H$_2$PO$_4$ on pH stabilization in deep flow culture system using tap water, and to determine the optimum range of NH$_4$H$_2$PO$_4$ in culture solution. The pH of tap water is 7.5. The higher the concentration of NH$_4$H$_2$PO$_4$ was, the more the pH of nutrient solution was decreased. In NH$_4$H$_2$PO$_4$ 4/3-5/3 me/$\ell$, the pH of nutrient solution was 6-7.5 during the experiment. The highest brix(%) was obtained in NH$_4$H$_2$PO$_4$ 5/3-6/3 me/$\ell$. Leaf length, leaf width and stem-base diameter were highest in NH$_4$H$_2$PO$_4$ 2/3 me/$\ell$. The L and b＊ values were highest and the a＊ value was lowest in NH$_4$H$_2$PO$_4$ 8/3 me/$\ell$. Toxicity symptom of ammonium appeared in NH$_4$H$_2$PO$_4$ 8/3 me/$\ell$. It suggests that there was the relationship between leaf color and growth condition. It was concluded that NH$_4$H$_2$PO$_4$ 2/3 me/$\ell$ was good before harvest stage and NH$_4$H$_2$PO$_4$ 5/3-6/3 me/$\ell$ at harvest stage.

• Journal of the Korean Electrochemical Society
• /
• v.13 no.4
• /
• pp.246-250
• /
• 2010

In this study, nano-crystallized $Al_2O_3$ was coated on the surface of $LiFePO_4$ powders via a novel dry coating method. The influence of coated $LiFePO_4$ upon electrochemical behavior was discussed. Surface morphology characterization was achieved by transmission electron microscopy (TEM), clearly showing nano-crystallized $Al_2O_3$ on $LiFePO_4$ surfaces. Furthermore, it revealed that the $Al_2O_3$-coated $LiFePO_4$ cathode exhibited a distinct surface morphology. It was also found that the $Al_2O_3$ coating reduces capacity fading especially at high charge/discharge rates. Results from the cyclic voltammogram measurements (2.5-4.2 V) showed a significant decrease in both interfacial resistance and cathode polarization. This behavior implies that $Al_2O_3$ can prevent structural change of $LiFePO_4$ or reaction with the electrolyte on cycling. In addition, the $Al_2O_3$ coated $LiFePO_4$ compound showed highly improved area-specific impedance (ASI), an important measure of battery performance. From the correlation between these characteristics of bare and coated $LiFePO_4$, the role of $Al_2O_3$ coating played on the electrochemical performance of $LiFePO_4$ was probed.

• Journal of the Korean Electrochemical Society
• /
• v.15 no.2
• /
• pp.101-108
• /
• 2012

The purpose of this study was to improve the conductivity of $Li_3V_2(PO_4){_3}$ by adding carbon source so that the discharge rate and cyclic properties were improved. Glucose and CNT were added to $Li_3V_2(PO_4){_3}$ and the structure and electrochemical properties were studied. $Li_3V_2(PO_4){_3}$, $Li_3V_2(PO_4){_3}$/C and $Li_3V_2(PO_4){_3}$/CNT were synthesised by solid state reaction using hydrogen reduction method at 600, 700, 800, $900^{\circ}C$. The cathode materials were assembled to coin cell type 2032 with Lithium metal as a counter electrode. The coin cell was galvanostatically evaluated in the voltage range of 3.0~4.8 V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.11a
• /
• pp.132-132
• /
• 2009

Phospho-olivine $LiFePO_4$ cathode materials were prepared by hydrothermal reaction. In this study, Multi-walled carbon nanotube (MWCNT) and Carbon black was added to enhance the electrical conductivity of $LiFePO_4$. $LiFePO_4$, $LiFePO_4$-MWCNT and $LiFePO_4$-C particles were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) transmission electron microscope (TEM). $LiFePO_4/SPE/Li$, $LiFePO_4$-MWCMT/SPE/Li and $LiFePO_4$-C/SPE/Li cells were characterized electrochemically by charge/discharge experiments at a constant current density of $0.1mA\;cm^{-2}$ in a range between 2.5 and 4.3 V vs. $Li/Li^+$ and cyclic voltammetry (CV).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.6
• /
• pp.519-523
• /
• 2006

$LiFePO_4$ has been received attention as a potential cathode material for the lithium secondary batteries. In our study, $LiFePO_4$ cathode active materials were synthesized by a solid-state reaction. It was modified by coating $TiO_2$ and carbon in order to enhance cyclic performance and electronic conductivity. $TiO_2$ and carbon coatings on $LiFePO_4$ materials enhanced the electronic conductivity and its charge/discharge capacity. For lithium polymer battery applications, $LiFePO_4$/solid polymer electrolyte (SPE)/Li and $LiFePO_{4}-TiO_{2}/SPE/Li$ cells were characterized by a cyclic voltammetry and charge/discharge cycling. The electrode with $LiFePO_{4}-carbon-TiO_{2}$ in PVDF-PC-EC-$LiClO_{4}$ electrolyte showed promising capacity of above 100 mAh/g at 1C rate.

• Transactions on Electrical and Electronic Materials
• /
• v.8 no.1
• /
• pp.41-45
• /
• 2007

Phospho-olivine $LiFePO_4$ cathode materials were prepared by hydrothermal reaction. Carbon black was added to enhance the electrical conductivity of $LiFePO_4$. The structural and morphological performance of $LiFePO_4$ and $LiFePO_4$-C powders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). $LiFePO_4$/Li and $LiFePO_4$-C/Li cells were characterized electrochemically by cyclic voltammogram (CV), charge/discharge experiments and ac impedance spectroscopy. The results showed that the discharge capacity of $LiFePO_4$/Li cell was 147 mAh/g at the first cycle and 118 mAh/g after 30 cycles, respectively. The discharge capacity of $LiFePO_4$-C/Li cell with 5 wt% carbon black was the largest among $LiFePO_4$-C/Li cells, 133 mAh/g at the first cycle and 128 mAh/g after 30 cycles, respectively. It was demonstrated that cycling performance of $LiFePO_4$-C/Li cell with 5 wt% carbon black was better than that of $LiFePO_4$/Li cell.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.12a
• /
• pp.48-52
• /
• 2006

Phospho-olivine $LiFePO_4$ cathode materials were prepared by hydrothermal reaction. Carbon black was added to enhance the electrical conductivity' of $LiFePO_4$. The structural and morphological performance of $LiFePO_4$ and $LiFePO_4$-C powders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). $LiFePO_4$/Li and $LiFePO_4-C$/Li cells were characterized electrochemically by cyclic voltammogram (CV), charge/discharge experiments and ac impedance spectroscopy. The results showed that the discharge capacity of $LiFePO_4$/Li cell was 147 mAh/g at the first cycle and 118 mAh/g after 30 cycles, respectively. The discharge capacity of $LiFePO_4-C$/Li cell with 5wt% carbon black was the largest among $LiFePO_4-C$/Li cells, 133 mAh/g at the first cycle and 128 mAh/g after 30 cycles, respectively. It was demonstrated that cycling performance of $LiFePO_4-C$/Li cell with 5wt% carbon black was better than that of $LiFePO_4$/Li cell.

• Journal of the Microelectronics and Packaging Society
• /
• v.26 no.4
• /
• pp.83-88
• /
• 2019

LiBaPO₄:Eu²⁺ phosphors with stoichiometric and nonstoichiometric compositions were prepared using a solid state reaction followed by heat treatment in reduced atmosphere, and the crystal structures and photoluminescence(PL) properties of the powders were investigated by x-ray powder diffraction and luminescence spectrometer. At 900℃, the Ba₃(PO₄)₂ phase as the intermediate phase was observed with the LiBaPO₄ phase as the main crystalline phase. Samples with a low europium concentration at 1,000℃ belonged to the trigonal structure, whereas samples with Eu²⁺ content more than 4 mol% showed monoclinic structure. In the nonstoichiometric compositions of 4 mol% Eu²⁺ and above, a single phase of Eu²⁺-doped LiBaPO₄, showing bluish green emission, was formed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.06a
• /
• pp.368-369
• /
• 2006

The pure $LiFePO_4$, carbon added $LiFePO_4(LiFePO_4/C$) and pyrene added $LiFePO_4(LiFePO_4/P$) are synthesized by using solid-state reaction. XRD patterns show no impurity phase in the three kinds of the cathode materials. The 10wt% pyrene added $LiFePO_4$ shows around 140mAh/g of discharge capacity at 3rd cycle compared to the pure $LiFePO_4$. The carbon added $LiFePO_4$ shows 145mAh/g of discharge capacity at 3rd cycle and stable cycle-life compared to the others.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.05b
• /
• pp.5-9
• /
• 2005

$LiFePO_4$ is a potential candidate for the cathode material of the lithium polymer batteries. $LiFePO_4$ cathode active materials were synthesized by coating on the $LiFePO_4$ was tried using $TiO_2$ and corbon in oreder to increase cyclic performance and electronic conductivity. Highly dispersed on the particles enhances the electronic conductivity and increases the capacity. For lithium polymer battery applications, $LiFePO_4$/SPE/Li and $LiFePO_4$-$TiO_2$/SPE/Li 'cells were characterized electrochemically by cyclic volatammetry and charge/discharge cycling. The $LiFePO_4$-carbon-$TiO_2$ cathode in PVDF-PC-EC-$LiCIO_4$ electrolyte showed high capacity at high current density.