• 한국재료학회지
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• 제12권4호
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• pp.274-278
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• 2002

Discrete-variational(DV)-$X{\alpha}$ method was applied to investigate the electronic structures of spinel- type manganese oxide which is well known to the high performance adsorbent or cathode material for lithium ion. The results of DOS(density of states) and Mulliken population analysis showed that Li was nearly fully ionized and interactions between Mn and O were strong covalent bond. The effective charge of Li and Mn was +0.77 and +1.44 respectively and the overlap population between Mn and O was 0.252 in $LiMn_2O_4$. These results from DV-X$\alpha$ method were well coincided with the experimental result by XPS analysis and supported the feasibility of theoretical interpretation for the $LiMn_2O_4$ compound.

• 한국분말재료학회지
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• 제19권3호
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• pp.210-214
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• 2012

Mass production-capable $Li_2MnSiO_4$ powder was synthesized for use as cathode material in state-of-the-art lithium-ion batteries. These batteries are main powder sources for high tech-end digital electronic equipments and electric vehicles in the near future and they must possess high specific capacity and durable charge-discharge characteristics. Amorphous silicone was quite superior to crystalline one as starting material to fabricate silicone oxide with high reactivity between precursors of sol-gel type reaction intermediates. The amorphous silicone starting material also has beneficial effect of efficiently controlling secondary phases, most notably $Li_xSiO_x$. Lastly, carbon was coated on $Li_2MnSiO_4$ powders by using sucrose to afford some improved electrical conductivity. The carbon-coated $Li_2MnSiO_4$ cathode material was further characterized using SEM, XRD, and galvanostatic charge/discharge test method for morphological and electrochemical examinations. Coin cell was subject to 1.5-4.8 V at C/20, where 74 mAh/g was observed during primary discharge cycle.

• Transactions on Electrical and Electronic Materials
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• 제10권3호
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• pp.102-105
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• 2009

$Li[Ni_{0.2}Li_{0.2}Mn_{0.6}]O_2$ cathode materials have been synthesized by a microwave-assisted sol-gel method. The structure and electrochemical properties of $Li[Ni_{0.2}Li_{0.2}Mn_{0.6}]O_2$ were studied by X-ray difftactometry (XRD), scanning electron microscopy (SEM) and charge-discharge cycler. The powder prepared by microwave assisted sol-gel method showed good crystallinity and well-defined facet shapes. The $Li[Ni_{0.2}Li_{0.2}Mn_{0.6}]O_2$ electrode delivered a high discharge capacity of 230 $mAhg^{-1}$ at the specific current of 40 $mAg^{-1}$ (0.2 C rate) in the voltage range of 2.0${\sim}$4.8 V. About 60 % of the discharge capacity measured at 0.2 Crate (140 $mAhg^{-1}$) was maintained at a 6 C (1200 $mAg^{-1}$)rate. The cyclic property was also stable and it did not deteriorated at a high Crate.

• 공업화학
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• 제16권5호
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• pp.689-692
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• 2005

스피넬계 $LiMn_2O_4$를 양극 활물질로 사용하는 리튬이온전지의 전기화학적 성능을 향상시키기 위하여 서로 상이한 입자크기를 가지는 Super P Black 및 $Vulcan^{(R)}$ XC-72R을 사용한 이성분계 전도성물질을 제조하였다. 이렇게 이성분계 전도성물질을 사용하여 제조되어진 $LiMn_2O_4$ 전지 시스템은 충 방전 동안의 비용량 및 사이클 수명의 관점에서 특성 평가되었다. 결과적으로 Super P Black 및 $Vulcan^{(R)}$ XC-72R이 3:7의 비율로 구성되어진 이성분계 전도성물질을 사용하였을 때의 전지가 우수한 전기화학적 성능을 보여주었으며 이는 적절한 조합의 ionic diffusion rate와 electric contact에 의해 제어되어졌기 때문인 것으로 여겨진다.

• 한국결정성장학회지
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• 제10권3호
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• pp.239-244
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• 2000

$LiMn_2$$O_4$Spine에 Li 과량 및 Mn 대신 Co를 일부 치환시킨 $_{1+x}$ Co$_{y}$ Mn$_{2-y}$ $O_4$(0$\leq$x$\leq$0.2,y=0,1/9,1/6) spinel에 대한 합성온도 결정, 상의 생성 등 고온 상평형에 대해 연구하였다. 고온 합성에 따른 제 2상의 생성을 방지하기 위해 저온합성이 가능한 습식화학적 합성법중 하나인 oxalate 침전법을 사용하여 $600^{\circ}C$ 이하에서 단일상의 spinel로 합성하였다. 이렇게 합성된 분말에 대해 TG-DTA분석 및 고온에서 급냉한 분말에 대한 XRD분석을 통해 질량(산소)의 증감에 연관된 가역적인 상전이 온도인 $T_1$, $T_2$및 $T_{2'}$ 들을 확인하였으며, 첨가된 Li의 양과 치환된 Co의 양에 따른 격자상수, 상전이 온도의 변화, 고온상의 안정성 등에 대해 연구하였다. 본 연구를 통해 Li$_{1+x}$ Co$_{y}$ Mn$_{2-y}$ $O_4$spinel의 합성온도 및 냉각속도 둥 합성과정 결정에 필요한 결과들을 얻을 수 있었다.

• 한국전기전자재료학회논문지
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• 제17권10호
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• pp.1085-1089
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• 2004

An impedance properties of the positive active material Li(Cr$_{0.4}$Mn$_{0.6}$)O$_2$ are measured by the changeable trend to the time. The charge-discharge capacities of 297 mAh(g)$^{-1}$ 175 mAh(g)$^{-1}$ are obtained by the made cell with the active material that the Cr was added to LiMnO$_2$ to prevent structural degradation of an electrode active material with impedance of 75 Ω to get at an initial hour. Resultantly, these variations which the impedances enhanced continually, were not watched the impeditive variations as the results of the delay time that the positive thin films and the references have been soaked all together in the solution of electrolyte of 1M LiPF$_{6}$ EC/DEC(l/2). Accordingly, it means an amount increased of the discharged capacities in the view of the results that the impeditive values were decreased are known already through a authorized paper.per.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1487-1488
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• 2011

Electrical properties and microstructure were investigated on the effects of $MnO_2$ and the lead-free $(Na_{0.44}K_{0.52}Li_{0.04})(Nb_{0.83}Sb_{0.07}Ta_{0.1})O_3$ ceramics with the addition of $MnO_2$ were fabricated by a conventional mixed oxide method. A gradual change in the crystal and microstructure was observed with the increase of $MnO_2$ addition. For the NKN-LST-xmol%$MnO_2$ sintered at $1100^{\circ}C$, bulk density increased with the addition of $MnO_2$ and showed maximum value at addition 1.0mol% of $MnO_2$. Curie temperature of the NKN-LST ceramics slightly decreased with adding $MnO_2$. The dielectric constant, piezoelectric constant ($d_{33}$) and electromechanical coupling factor ($k_p$) increased below 0.25mol% of $MnO_2$ addition, which might be due to the increase in density. The high piezoelectric properties = 145 pC/N, electromechanical coupling factor = 0.421 and dielectric constant = 2883 were obtained for the NKN-LST-0.25mol%$MnO_2$ sintered at $1100^{\circ}C$ for 4h.

• 전기화학회지
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• 제18권4호
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• pp.137-142
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• 2015

$Mn_{1+X}Co_{2-X}O_4$ solid solutions with various Mn/Co ratios were synthesized by a combustion method, and used as cathode catalysts for lithium/air secondary battery. Their electrochemical and physicochemical properties were investigated. The morphology was examined by transmission electron microscopy (TEM), and the crystallinity was confirmed by X-ray diffraction (XRD) analyses. For the measurement of electrochemical properties, charge and discharge measurements were carried out at a constant current density of $0.2mA/cm^2$, monitoring the voltage change. Electrochemical impedance spectroscopy (EIS) analyses were also employed to examine the change in charge transfer resistance during charge-discharge process. $Mn_{1+X}Co_{2-X}O_4$ solid solutions showed enhanced cycleability as a cathode of Li/air secondary battery, and the performance was found to be strongly dependent on Mn/Co ratio. Among synthesized catalysts, $Mn_{1.5}Co_{1.5}O_4$ exhibited the best performance and cycleability, due to high charge transfer rate.

• 한국응용과학기술학회지
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• 제18권3호
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• pp.167-173
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• 2001

The spinel $LiMn_{2}O_{4}$ powders were synthesized at $480^{\circ}C$ for 12 h in air by a sol-gel method using manganese acetate and lithium hydroxide as starting material and the $Fe_{3}O_{4}$ powders were synthesized by the precipitation method using $0.2M-FeSO_{4}{\cdot}H_{2}O$ and 0.5M-NaOH. The synthesized $Fe_{3}O_{4}$ powders were mixed at portion of 5, 10, 15 and 20 wt% about $LiMn_{2}O_{4}$ powders through ball-milling followed by drying at room temperature for 48 h in air. The mixed catalysts were reduced at $350^{\circ}C$ for 3 h by hydrogen and the decomposition rate of carbon dioxide was measured at $350^{\circ}C$ using the reduced catalysts. As the results of $CO_{2}$ decomposition experiments, the decomposition rates of carbon dioxide were 85% in all catalysts but the initial decomposition rates of $CO_{2}$ were slightly high in the case of the $5%-Fe_{3}O_{4}$ added catalyst.

• 한국세라믹학회지
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• 제45권2호
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• pp.112-118
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• 2008

To prepare the high-capacity cathode material with improved electrochemical performances, nanoparticles of $C0_3(PO_4)_2$ were coated on the powder surface of $Li[Co_{0.1}Ni_{0.15}Li_{0.2}Mn_{0.55}]O_2$, which was already synthesized by simple combustion method. The coated powders after the heat treatment at >$700^{\circ}C$ surely showed well-structured crystalline property with nanoscale surface coating layer, which was consisted of $LiCOPO_4$ phase formed from the reaction bwtween $CO_3(PO_4)_2$ and lithium impurities. In addition, cycle performance was particularly improved by the $CO_3(PO_4)_2$-coating for the cathode material for lithium rechargeable batteries.