• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.5
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• pp.398-402
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• 2012

Synthesis of $Li_2MnSiO_4$ was attempted by the conventional solid-state reaction method, and the phase formation behavior according to the change of the calcination condition was investigated. When the mixture of the three source materials, $Li_2O$, MnO and $SiO_2$ powders, were used for calcination in air, it was difficult to develop the $Li_2MnSiO_4$ phase because the oxidation number of $Mn^{2+}$ could not be maintained. Therefore, two-step calcination was applied: $Li_2SiO_3$ was made from $Li_2O$ and $SiO_2$ at the first step, and $Li_2MnSiO_4$ was synthesized from $Li_2SiO_3$ and MnO at the second step. It was easy to make $Li_2MnSiO_3$ from $Li_2O$ and $SiO_2$. $Li_2MnSiO_4$ single phase was developed by the calcination at $900^{\circ}C$ for 24 hr in Ar atmosphere as the oxidation of $Mn^{2+}$ was prevented. However, the $Li_2MnSiO_4$ was ${\gamma}-Li_2MnSiO_4$, one of the polymorph of $Li_2MnSiO_4$, which could not be used as the cathode materials in Li-ion batteries. By applying the additional low temperature annealing at $400^{\circ}C$, the single phase ${\beta}-Li_2MnSiO_4$ powder was synthesized successfully through the phase transition from ${\gamma}$ to ${\beta}$ phase.

• Journal of the Korean Electrochemical Society
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• v.18 no.4
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• pp.143-149
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• 2015

Carbon-coated $Li_2MnSiO_4$ powders as the active materials for the cathode were synthesized by planetary ball milling and solid-state reaction, and their phase formation behavior and charge-discharge properties were investigated. Calcination temperature and atmosphere were controlled in order to obtain the ${\beta}-Li_2MnSiO_4$ phase, which was active electrochemically, and the carbon-coated $Li_2MnSiO_4$ active material powders with near single phase ${\beta}-Li_2MnSiO_4$ could be fabricated. The particles of the synthesized powders were secondary particles composed of primary ones of about 100 nm size. The carbon incorporation was essential to enable the Li ions to be inserted and extracted from $Li_2MnSiO_4$ active materials, and the initial capacity of 192 mAh/g could be obtained in the $Li_2MnSiO_4$ active materials with 4.8 wt% of carbon.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.7
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• pp.447-453
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• 2017

In this study, $Li_2MnSiO_4$ cathode material and LiPON solid electrolyte were manufactured into thin films, and the possibility of their use in thin-film batteries was researched. When the RTP treatment was performed after $Li_2MnSiO_4$ cathode thin-film deposition on the SUS substrate by a sputtering method, a ${\beta}-Li_2MnSiO_4$ cathode thin film was successfully manufactured. The LiPON solid electrolyte was prepared by a reactive sputtering method using a $Li_3PO_4$ target and $N_2$ gas, and a homogeneous and flat thin film was deposited on a $Li_2MnSiO_4$ cathode thin film. In order to evaluate the electrochemical properties of the $Li_2MnSiO_4$ cathode thin films, coin cells using only a liquid electrolyte were prepared and the charge/discharge test was conducted. As a result, the amorphous thin film of RTP treated at $600^{\circ}C$ showed the highest initial discharge capacity of about $60{\mu}Ah/cm^2$. In cases of coin cells using liquid/solid double electrolyte, the discharge capacities of the $Li_2MnSiO_4$ cathode thin films were comparable to those without solid LiPON electrolyte. It was revealed that $Li_2MnSiO_4$ cathode thin films with LiPON solid electrolyte were applicable in thin film batteries.

• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.752-756
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• 2002

Green-emitting $Zn_2SiO_4:Mn$ phosphors for PDP(Plasma Display Panel) application were synthesized by colloidal seed-assisted spray pyrolysis process. The codoping with $Gd^{3+}/Li^+$, which replaces $Si^{4+}$ site in the willemite structure, was performed to improve the luminous properties of the $Zn_2SiO_4:Mn$ phosphors. The particles prepared by spray pyrolysis process using fumed silica colloidal solution had a spherical shape, small particle size, narrow size distribution, and non-aggregation characteristics. The $Gd^{3+}/Li^+$ codoping amount affected the luminous characteristics of $Zn_2SiO_4:Mn$ phosphors. The codoping with proper amounts of $Gd^{3+}/Li^+$ improved both the photoluminescence efficiency and decay time of $Zn_2SiO_4:Mn$ phosphor particles. In spray pyrolysis, the post-treatment temperature is another factor controlling the luminous performance of $Zn_2SiO_4:Mn$ phosphors. The $Zn_{1.9}SiO_4:Mn_{0.1}$ phosphor particles containing 0.1 mol% $Gd^{3+}/Li^+$ co-dopant had a 5% higher PL intensity than the commercial product and 5.7 ms decay time after post-treatment at $1,145^{\circ}C$.

• Journal of the Korean Vacuum Society
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• v.20 no.3
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• pp.205-210
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• 2011

Structural and electrochemical properties of spinel oxide $LiMn_2O_4$ thin films prepared by using a sol-gel method on Pt/Ti/$SiO_2$/Si substrates were investigated. When Li/Mn molar ratio of the film was smaller than 0.5, $Mn_2O_3$hase was found to coexist with $LiMn_2O_4$. Half-cell batteries fabricated using the $LiMn_2O_4$ films as the cathode were put into chargedischarge (C-D) cycles and the change in structural properties of the cathode after the cycles was examined by X-ray diffraction and Raman spectroscopy. As the C-D cycle number increases, the discharge capacity of pure $LiMn_2O_4$ battery gradually decreases, being reduced to 72% of the initial capacity at 300 cycles. Such capacity fading is attributable to the decrease in the number of $Li^+$ ions that return to the tetrahedral sites of the spinel structure during the discharge step and the resultant increase in $Mn^{4+}$ density in the film. Also, $Mn_2O_3$ phase gradually appeared in the film as the cycle number increases.

• Journal of Electrochemical Science and Technology
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• v.3 no.2
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• pp.72-79
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• 2012

$Li_2MnSiO_4$ was synthesized using the solid-state method under an Ar atmosphere at three different calcination temperatures (900, 950, and $1000^{\circ}C$). The optimization of the carbon coating was also carried out using various molar concentrations of adipic acid as the carbon source. The XRD pattern confirmed that the resulting $Li_2MnSiO_4$ particles exhibited an orthorhombic structure with a $Pmn2_1$ space group. Cyclic voltammetry was utilized to investigate the capacitive behavior of $Li_2MnSiO_4$ along with activated carbon (AC) in a hybrid supercapacitor with a two-electrode cell configuration. The $Li_2MnSiO_4$/AC cell exhibited a high discharge capacitance and energy density of $43.2Fg^{-1}$ and $54Whkg^{-1}$, respectively, at $1.0mAcm^{-2}$. The $Li_2MnSiO_4$/AC hybrid supercapacitor exhibited an excellent cycling stability over 1000 measured cycles with coulombic efficiency over > 99 %. Electrochemical impedance spectroscopy was conducted to corroborate the results that were obtained and described.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4205-4209
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• 2011

The $Li_2Mn_{0.5}Fe_{0.5}SiO_4$ silicate was prepared by blending of $Li_2MnSiO_4$ and $Li_2FeSiO_4$ precursors with same molar ratio. The one of the silicates of $Li_2FeSiO_4$ is known as high capacitive up to ~330 mAh/g due to 2 mole electron exchange, and the other of $Li_2FeSiO_4$ has identical structure with $Li_2MnSiO_4$ and shows stable cycle with less capacity of ~170 mAh/g. The major drawback of silicate family is low electronic conductivity (3 orders of magnitude lower than $LiFePO_4$). To overcome this disadvantage, carbon composite of the silicate compound was prepared by sucrose mixing with silicate precursors and heat-treated in reducing atmosphere. The crystal structure and physical morphology of $Li_2Mn_{0.5}Fe_{0.5}SiO_4$ was investigated by X-ray diffraction, scanning electron microscopy, and high resolution transmission electron microscopy. The $Li_2Mn_{0.5}Fe_{0.5}SiO_4$/C nanocomposite has a maximum discharge capacity of 200 mAh/g, and 63% of its discharge capacity is retained after the tenth cycles. We have realized that more than 1 mole of electrons are exchanged in $Li_2Mn_{0.5}Fe_{0.5}SiO_4$. We have observed that $Li_2Mn_{0.5}Fe_{0.5}SiO_4$ is unstable structure upon first delithiation with structural collapse. High temperature cell performance result shows high capacity of discharge capacity (244 mAh/g) but it had poor capacity retention (50%) due to the accelerated structural degradation and related reaction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.64-65
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• 2008

3D microbattery에 사용할 수 있는 $LiMn_2O_4$ 3차원 박막전극을 제조하여 그 전기화학적 특성을 관찰하였다. 3차원 구조의 형성을 위하여 먼저 polystyrene(PS) microsphere를 platinum이 증착된 Si/$SiO_2$ 기판위에 dip-coating 방식으로 코팅시켜 template로 사용하였다. 그 위에 sol-gel법을 이용, 박막을 형성시킨 후 template 를 제거하는 방식으로 $LiMn_2O_4$ 3차원 박막전극을 형성하였는데 이때 solution은 Lithium acetylacetonate[$LiCH_3CO-CHCOCH_3$], Manganese(III) acetylacetonate [Mn$(CH_3COCHCOCH_3)_3$]를 source 물질로 1-butanol과 acetic acid를 solvent로 활용하여 제조하였다.

• Bulletin of the Korean Chemical Society
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• v.30 no.3
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• pp.653-656
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• 2009

3-Dimensionally ordered macroporous $LiMn_2O_4$ thin film was prepared by a sol-gel and dip coating method on Pt/Ti/$SiO_2$/Si substrate. An opal structure consisting of mono dispersed polystyrene beads (300 nm) was used as a template. After solution containing Mn and Li precursors was coated on the template-deposited substrate, the template and organic materials in the precursors was removed by calcination at 400 ${^{\circ}C}$. And then the 3-dimensional $LiMn_2O_4$ thin film with spinel structure was fabricated by heat treatment at 700 ${^{\circ}C}$. The structural and electrochemical property was investigated by XRD, SEM and charge-discharge cycler.

• Journal of Energy Engineering
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• v.20 no.2
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• pp.103-108
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• 2011

$Li_2MnSiO_4$/C was synthesized by solid state reaction and solution synthesis with sucrose for carbon source. The X-ray diffraction patterns of solid state reaction indicates small amount of impurities. By FE-SEM and HR-TEM, solution synthesis comprised several tens of nanometer comparing to 500~600 nm of $Li_2MnSiO_4$/C prepared by solid state reaction. The $Li_2MnSiO_4$/C prepared by solution synthesis show better electrochemical performance than solid state reaction. The first charge-discharge capacity are 236, 189 mAh/g respectively by solution synthesis. But its cycle performance was poor as yet and its capacity retention was 62% after 10 cycles.