• 대한화학회지
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• 제66권6호
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• pp.451-458
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• 2022

LiNi_xMn_yCo_1-(x+y)O₂의 자기특성을 고려한 자기장 이용 결정방향 제어 연구를 통해, LiNi_0.6Mn_0.2Co_0.2O₂ 결정 내 많은 비율의 (00l) plane들이 전극집전체 표면에 수직으로 정렬된 결정배향 전극을 확보하였다. 해당 결정배향 전극은 리튬이차전지의 충방전 과정 중에 낮은 전극 polarization 특성을 나타내었으며, 일반 LiNi_0.6Mn_0.2Co_0.2O₂ 전극 대비 높은 용량을 기록하였다. 결정 배향 전극은 빠른 리튬이온 전달에 적합한 구조적 특성으로 인해 리튬이차전지 성능 향상에 기여한 것으로 예상되었다. 결정배향 전극에 의한 성능 향상을 다양한 전기화학적 이론 및 분석 결과를 통해 검증, 해석하였다.

• 한국자기공명학회논문지
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• 제6권2호
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• pp.118-131
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• 2002

Manganese-doped H-SAPO-34 samples were prepared by an ion-exchanged reaction between H-SAPO-34 and paramagnetic Mn(II) species in methanol media and characterized by ESR and Electron Spin-Echo Modulation(ESEM) studies. In the hydrated (W)MnH-SAPO-34 measured in water, the Mn(II) ion was octahedrally coordinated with four framework oxygens and two water molecules at a displaced site IV of the eight membered ring window in the ellipsoidal cavity, while the Mn(II) ion was octahedrally coordinated to three framework oxygens and three water molecules at a displaced site I' of the six membered ring window in the ellipsoidal cavity in hydrated(M)MnH-SAPO-34 measured in methanol. The similar result was found in the experiments with methanol adsorbents except ethanol.

• Current Applied Physics
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• 제18권11호
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• pp.1431-1435
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• 2018

Using first-principles calculations, we successfully investigate the electrochemical performance of the monoclinic $NaMnO_2$ for the sodium ion batteries. $NaMnO_2$ possesses a voltage window of 3.54-2.52 V and theoretical reversible capacity of $136mAh\;g^{-1}$. Besides, we find that the metallicity of the monoclinic $NaMnO_2$ gradually increases during Na extraction. Moreover, the computational Na migration energy barrier in the monoclinic $NaMnO_2$ is 0.18 eV, ensuring ideal conductivity and reversible capacity. Although the Jahn-Teller distortion effects limit the enhancement of the reversible capacity of the monoclinic $NaMnO_2$, it is still a right cathode material for the sodium ion batteries. The computational results are well in consistent with the experimental investigations.

• 한국재료학회지
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• 제31권2호
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• pp.68-74
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• 2021

Zinc-ion Batteris (ZIBs) are recently being considered as energy storage devices due to their high specific capacity and high safety, and the abundance of zinc sources. Especially, ZIBs can overcome the drawbacks of conventional lithium ion batteris (LIBs), such as cost and safety issues. However, in spite of their advantages, the cathode materials under development are required to improve performance of ZIBs, because the capacity and cycling stability of ZIBs are mainly influenced by the cathode materials. To design optimized cathode materials for high performance ZIBs, a novel manganese oxide (MnO2) coated graphite sheet is suggested herein with improved zinc-ion diffusion capability thanks to the uniformly decorated MnO2 on the graphite sheet surface. Especially, to optimize MnO2 on the graphite sheet surface, amounts of percursors are regulated. The optimized MnO2 coated graphite sheet shows a superior zinc-ion diffusion ability and good electrochemical performance, including high specific capacity of 330.8 mAh g-1 at current density of 0.1 A g-1, high-rate performance with 109.4 mAh g-1 at a current density of 2.0 A g-1, and remarkable cycling stability (82.2 % after 200 cycles at a current density of 1.0 A g-1). The excellent electrochemical performance is due to the uniformly decorated MnO2 on the graphite sheet surface, which leads to excellent zinc-ion diffusion ability. Thus, our study can provide a promising strategy for high performance next-generation ZIBs in the near future.

• Journal of Electrochemical Science and Technology
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• 제4권3호
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• pp.102-107
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• 2013

The electrochemical properties of Mg-doped $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ and pure $LiFe_{0.5}Mn_{0.5}PO_4$ olivine cathodes are examined and the lattice parameters are refined by Rietveld analysis. The calculated atomic parameters from the refinement show that $Mg^{2+}$ doping has a significant effect in the olivine $LiFeMnPO_4$ structure. The unit cell volume is 297.053(2) ${\AA}^3$ for pure $LiFe_{0.5}Mn_{0.5}PO_4$ and is decreased to 296.177(1) ${\AA}^3$ for Mg-doped $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ sample. The doping of $Mg^{2+}$ cation with atomic radius smaller than $Mn^{2+}$ and $Fe^{2+}$ ion induces longer Li-O bond length in $LiO_6$ octahedra of the olivine structure. The larger interstitial sites in $LiO_6$ octahedra facilitate the lithium ion migration and also enhance the diffusion kinetics of olivine cathode material. The $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ sample with larger Li-O bond length delivers higher discharge capacities and also notably increases the rate capability of the electrode.

• 한국세라믹학회지
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• 제43권9호
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• pp.588-593
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• 2006

Spinel phase $LiMn_2O_4$ is of great interest as cathode materials for lithium-ion batteries. In this study, SHS (Self propagating High-temperature Synthesis) method to synthesize spinel $LiMn_2O_4$ directly from lithium nitrate, manganese oxide, manganese and sodium chloride were investigated. The influence of Li/Mn ratio, the heat-treated condition of product have been explored. The resultant $LiMn_2O_4$ synthesized under the optimum synthesis conditions shows perfect spinel structure, uniform particle size and excellent electrochemical performances.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1220-1221
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• 2006

[ $LiMn_2O_4$ ] powders for lithium ion batteries were synthesized from two separate raw material pairs of LiOH/MnO and $LiOH/MnO_2$. The powders prepared at 780 and $850^{\circ}C$ and their difference of electrochemical properties were investigated. Both powders calcined at 780 and $850^{\circ}C$ were composed of a single-phase spinel structure but those treated at $850^{\circ}C$ showed a lower intensity ratio of $I_{311}$ to $I_{400}$, a slightly larger lattice parameter, and an increased discharge capacity by 10% under $3.0{\sim}4.3V$ voltage range. The XPS study on the oxidation states of manganese repealed that powders made from LiOH/MnO had less $Mn^{3+}$ ion and gave better battery performances than those from $LiOH/MnO_2$.

• 분석과학
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• 제17권1호
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• pp.1-7
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• 2004

N-nitroso-N-phenylhydroxylamineammonium salt(cupferron)과 tetrabutylammonium ion ($TBA^+$)을 사용하여 수용액 중 미량 Mn(II)을 상승 용매 추출하는 법에 대해서 연구하였다. $TBA^+$가 존재할 때 cupferron으로 수용액 중의 Mn(II)을 추출하면 용액의 pH 4-10 범위에서 95% 이상이 추출되지만 $TBA^+$가 존재하지 않으면 거의 추출되지 않았다. 이런 조건에서 Mn(II)의 추출은 $CH_2Cl_2$나 $CHCl_3$와 같은 유기용매를 사용 할 때가 다른 비극성 용매를 사용할 때 보다 현저히 잘 추출되었으므로 여기서는 chloroform을 사용하였다. 그리고 수용액의 pH는 5로 조절하였다. 실제시료 중 존재하는 극미량의 Mn(II)을 정량하기 위해서는 chloroform에 추출된 Mn(II)을 다시 0.1 mol/L $HNO_3$용액에 역 추출하여 GF-AAS로 Mn(II)의 흡광도를 측정하였다. 본 방법으로 얻은 Mn(II)의 검출한계는 0.37 ng/mL이었고, 이 방법을 응용하여 실험실 수돗물 중 Mn(II)을 정량한 결과는 0.4-1.01 ng/mL로 얻어졌다. 이 시료에 일정량의 Mn(II)용액을 첨가하여 얻은 회수율은 94-107%이었다. 그리고 Cu(II), Ca(II), Fe(III) 등 공존하는 다른 원소는 10 내지 $20{\mu}g/mL$까지 Mn(II) 정량에 방해를 하지 않았다. 이로서 본 방법이 극미량 Mn(II)의 새로운 분석법으로 사용될 수 있을 것으로 생각된다.

• 상하수도학회지
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• 제32권2호
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• pp.145-152
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• 2018

This study is focused on manganese (Mn(II)) removal by ozonation in surface water. Instant ozone demand for the water was 0.5 mg/L in the study. When 0.5 mg/L of Mn(II) is existed in water, the optimum ozone concentration was 1.25 mg/L with reaction time 10 minutes to meet the drinking water regulation. The ozone concentration to meet the drinking water regulation was much higher than the stoichiometric concentration. The reaction of soluble manganese removal was so fast that the reaction time does not affect the removal dramatically. When Mn(II) is existed with Fe, the removal of Mn(II) was not affected by Fe ion. However As(V) is existed as co-ion the removal of Mn(II) was decreased by 10%. Adding ozone to surface water has limited effect to remove dissolved organic matter. When ozone is used as oxidant to remove Mn(II) in the water, the existing co-ion should be evaluated to determine optimum concentration.

• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.309-314
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• 2010

The surface modified $LiMn_2O_4$ materials with Li-Fe composites were prepared by a sol-gel method to improve the electrochemical performance of $LiMn_2O_4$ and were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and transmission electron microscopy (TEM)-EDS. XRD results indicate that all the samples (modified and pristine samples) have cubic spinel structures, and XRD, XPS, and TEM-EDS data reveal the formation of $Li(Li_xFe_xMn_{2-2x})O_4$ solid solution on the surface of particles. For the electrochemical properties, the modified material demonstrated dramatically enhanced reversibility and stability even at elevated temperature. These improvements are attributed to the formation of the solid solution, and thus-formed solid solution phase on the surface of $LiMn_2O_4$ particle reduces the dissolution of Mn ion and suppresses the Jahn-Teller effect.